Properties, mechanical

Some properties of a PPX are summarized in Table 2.3. Parylene E, with 69% diethylated and 25% monoethylated p-xylylene groups shows unusual properties among the Parylene group. It is nearly optically isotropic. Therefore this Parylene type is a candidate for optical waveguides. It 

Parylenes have dielectric constants of 2.35 to 3.15. The dielectric constant decreases as the quantity of fluorine atoms increases within the polymer, therefore, octafluoro[2.2]paracyclophane is a valuable monomer from this aspect. 

PPX (Parylene N) has a low dielectric constant, which is independent of frequency, and has a low dissipation factor, which makes it ideal for high-frequency applications. 

The above properties are static physical properties which are determined with a linearly increasing applied force. Polymeric materials, including structural adhesives, have another important set of physical properties due to the fact that these materials behave in a manner that is not only elastic, but also viscoelastic in response to an applied stress. Viscous response may be treated by means of the linear constitutive equation formalism. Thus for a polymeric body, following FerryEq. (14) may be written  

Differentiating this equation with respect to time gives Eq. (16). 

This equation shows that the response of the system consists of two components, one of which is in phase with the strain and the other of which is 90° out of phase with the strain. The expressions contained in square brackets in Eq. 18 are not functions of time, but of frequency only hence Eq. 18 may be written as Eq. 19. 

The quantities G and G are the shear storage modulus and the shear loss modulus, respectively. G is a measure of the average amount of energy stored in the sample during a period of the oscillation while G is a measure of the amount of energy lost as heat during the same period. This entire derivation is completely analogous to that for loss in an RC circuit in electronics or for a driven harmonic oscillator in simple mechanical systems. It is also possible to express Eq. (19) as Eq. (20), 

This term is the ratio of the loss modulus to the storage modulus. 

Mechanical properties of a polymer depend on many variables— molecular weight, molecular weight distribution, morphology, additives, temperature, time, and so on. Mechanical properties of polymers are 

Mechanical properties of a polymer are mainly determined by how much stress a sample will withstand before the sample fails. At low strain (i.e., 1 percent), the deformation of most polymers is elastic where the deformation is homogeneous and full recovery can occur over a finite time. Among the mechanical properties that are of fundamental interests in commercial polymers are  

Compressive strength It is the extent to which a sample can be compressed before it fails. 

Flexural strength It is a measure of resistance to breaking, or snapping, when a sample is bent (flexed). 

Impact strength It is a measure of toughness, that is, how well a sample will withstand the sudden onset of stress, like a hammer blow. Usually, chain stiffening lowers the impact strength and increases embrittlement. 

Mechanical properties include the many properties used to describe the strength of materials such as elasticity, plasticity, tensile strength, eompressive strength. 

Some ceramics are semiconductors. Most of these are transition metal oxides, such as zinc oxide. Ceramicists are most interested in the electrical properties that show grain boundary effects. Semiconducting ceramics are also employed as gas sensors. When various gases are passed over a poly crystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced. 

Pyroelectricity The piezoelectric effect is generally stronger in materials that 

Ferroelectricity In turn, pyroelectricity is seenmost strongly inmaterials which 

The tensile properties of homogeneous ethylene-alkene statistical copolymers were further explored by Kennedy et al. [64]. It has been shown that the yield stress of a semicrystalline polymer is dependent on its crystal thickness [65, 66]. During uniaxial compression, the yield stress of polyethylene was observed to increase with crystal thickness up to 40 nm, whereas for thicker crystals it leveled off [66]. Since the crystal thickness in homogeneous copolymers decreases with increasing counit concentration, not surprisingly, an inverse correlation was also found between yield stress and counit content [64]. 

In many ways, crystallization of statistical copolymers resembles that of homopolymers [65, 68-70]. For example, hydrogenated polybutadienes of different branch content and molecular weight show sigmoidal crystallization isotherms, similar to those seen in polyethylene homopolymer crystallization. In addition, at a given isothermal crystallization temperature, the degree of copolymer crystallinity drops above a critical molecular weight, also qualitatively similar to polyethylene homopolymer [69]. 

However, there are also aspects of the crystallization process that are particular to statistical copolymers [16, 69, 71-76]. In a series of studies on the crystallization and melting behavior of ethylene-butene statistical copolymers, it was observed that after isothermal crystallization, while polyethylene homopolymer exhibited a single-peak melting endotherm, all the copolymers showed bimodal melting behavior [16,71]. Each melting peak of the copolymer endotherm was determined to represent a distinct crystal population because its shape 

Another distinguishing aspect of copolymer crystallization is that with increasing counit content, the crystallization isotherms deviate from the Avrami relation, given in Equation 11.6 [79], at progressively lower extents of crystallization [69,76] 

In Equation 11.6, f t) is the fraction of the crystallization process that has occurred by time t, and k and n are constants determined by the nature of the crystallization process. At small extents of crystallization 

Many polymer properties such as solvent, chemical, and electrical resistance and gas permeability are important in determining the use of a specific polymer in a specific application. However, the prime consideration in determining the general utility of a polymer is its 

Several stress-strain plots are shown in Fig. 1-10. Four important quantities characterize the stress-strain behavior of a polymer  

Modulus. The resistance to deformation as measured by the initial stress divided by AL/L. 

Ultimate Strength or Tensile Strength. The stress required to rupture the sample. 

Ultimate Elongation. The extent of elongation at the point where the sample ruptures. 

The mechanical properties of tungsten are only intrinsic as long as highly pure single crystals are Considered. Polycrystalline tungsten, from a technical standpoint, is the most important form and, by far, the biggest amount of the metal used. These properties are also strongly influenced by two main factors  

Microstructure. The microstructure of a tungsten sample, which influences the mechanical properties within a wide range, depends on the type of preparation (powder metallurgy, arc cast, electron beam melted, zone refined, chemical vapor deposition) and the subsequent working (deformation, annealing, recrystallization). 

FIGURE 1.9 Microstructures of tungsten wires (A) fibrous structure of the as-drawn tungsten wire, (B) equiaxed grain structure of recrystallized pure wire, (C) interlocking grain structure of recrystallized NS-doped wire. By courtesy of Philips Lighting B.V, Eindhoven, The Netherlands. 

The analytical determination of the foreign element c ncentration and distribution in tungsten is linked with highly sophisticated equipment (Auger spectroscopy, secondary ion mass spectrometry) and with complicated pretreatment of the samples. This may be one reason why our knowledge about foreign element influences is still quite incomplete. 

Heterogeneous impurities (particles of foreign matter in the raw materials) cause locally foreign phases or voids, often combined with diflusion ones. 

The mechanical properties of materials involve various concepts such as hardness, stiffness, and piezoelectric constants, Young s and bulk modulus, and yield strength. The solids are deformed under the effect of external forces and the deformation is described by the physical quantity strain. The internal mechanical force system that resists the deformation and tends to return the solid to its undeformed initial state is described by the physical quantity stress. Within the elastic limit, where a complete recoverability from strain is achieved with removal of stress, stress g is proportional to strain e. The generalized Hooke s law gives each of the stress tensor components as linear functions of the strain tensor components as 

Since both stress and strain are symmetric with respect to an interchange of the suffixes and the elastic coefficients form symmetric fourth-rank tensors, there are 

21 independent elastic coefficients that can be formed into a symmetric 6x6 matrix. In hexagonal crystals, due to additional symmetry, there remains only five independent stiffness constants Cn, C33, C12, C13, and C44. The stress-strain relations for the wurtzite crystal are therefore expressed as (c-axis is chosen to be the z-axis) 

Similarly, the relations using the compliance matrix can be written as 

In zinc blende (cubic) crystals, there are only three independent stiffness constants Cii, C12, and C44. The above relations then take the form 

The mechanical properties, including Young s modulus, elongation at break, toughness, yield stress and yield strain, of all the nanocomposites prepared in this study, together with the corresponding values for the virgin polymer, are 

Biodegradable Polymer-Clay Nanocomposite Fire Retardants Table 6.2 

Comparative data on mechanical properties ( error) of PBA and PBA-SS nanocomposites. Reproduced from reference 41 with permission from Elsevier 

Sample Young s modulus (MPa) Elongation at break (%) Toughness (MPa) Yield strain (%) Yield stress (MPa) 

Biodegradable Polymer-Clay Nanocomposite Fire Retardants 

In the instance that mechanical effects can be adequately treated as purely elastic, the firequency of a SAW device is perturbed by modulus changes according to 

Organic polymers comprise the most common type of coating used with AW sensors due to their capability to reversibly sorb vapors and liquids. For those polymers whose interactions with AWs can be treated as perfectly elastic, the fact that A is invariably larger than ft means that the value of the term (A + fi)/( + 2ft) is constrained between 0.67 and 1 thus, this ratio can be approximated using a value of 0.84. The magnitude of a purely elastic perturbation is then proportional to the product of shear modulus and thickness, with no more than a 16% error. 

Other studies have reported frequency increases for polymer-coated SAW devices upon exposure to water vapor at elevated temperatures ( 80°C), consistent with a predominance of elastic stiffening of the coating [57]. At lower temperatures (25-35 C), the same sensors exhibited frequency decreases upon exposure to water vapor of the same concentration, a response consistent with mass loading. Thus, the dominant mechanism may be determined by a variety of factors, including the type of vapor-coating interactions and the ambient temperature. Note that ambient temperature can have profound effects on flim viscoelastic properties (see Chapter 4), which in turn can influence the results of vapor exposure. 

The relative importance of the mass-loading and viscoelastic contributions to the observed acoustic sensor response is an issue that has yet to be resolved. Capitalizing on these effects to improve chemical selectivity and detection sensitivity requires further characterization of sensor response, in terms of both velocity and attenuation changes, in addition to more accurate models describing how coating-analyte interactions affect relevant film properties. 

Adequate mechanical properties are a prerequisite in most applications of plastics response to stressing by fracture or deformation is usually of crucial 

Breakage of a component or article is frequently a limitation on its use this subject has, therefore, received considerable attention. Failure may be brittle or ductile, the former occurring at low elongation, the latter with considerable deformation, and as the culmination of creep. Brittle failure in plastics materials is sometimes inherent and sometimes unexpected. Many laboratory tests indicate that most plastics are either tough or brittle, which is very convenient, since there are rules for dealing with ductile materials, and different rules for dealing with brittle ones. However, some plastics break at unexpectedly low stresses and, even more seriously, products made from plastics which are expected to be ductile from laboratory tests and general experience can also fail in a brittle manner. 

Considerations based on a fracture mechanics analysis are necessary if the designer is to progress beyond the primary division of plastics into ductile or brittle , based on simple laboratory tests (see Chapter 2). 

The excellent mechanical properties of graphene are derived from the extremely strong o-bonds (670 kJ/mol) in the basal plane. In 2002, Bemhoic et al. had predicted that the intrinsic strength of graphene would be superior to any other material by quantum simulation. Lee et al. s experimental 

Typical values of the mechanical properties of the more common materials used in the construction of chemical process equipment are given in Table 7.2. 

Behari [10] gives a useful general review of many solid state properties of bone, both human and non-human, many of which are not dealt with here. These properties include the Hall effect, photo-electric effects, electron paramagnetic resonance effects and so on. 

There is a great range for values in the literature for many reasons. Amongst these are  

Age may affect intrinsic properties. Osteoporotic bone may differ from normal bone in ways other than the fact that it is more porous there is evidence that the collagen is different from that in similar-aged non-osteoporotic subjects [18]. Bone from osteogenesis imperfecta patients has a higher proportion of Type III and Type V collagen compared with Type I collagen, than bone from normal subjects [19]. 

Bone collagen from osteopetrotic subjects is in general older than that from normal subjects, and has correspondingly different properties [5]. 

The values reported below should be considered paradigmatic, that is, to be valid for a well-performed test on bone obtained from a middle aged person with no disease. Other values are reported in such a way as to make it clear how some property is a function of other features of the specimen. 

Mechanical analysis is a common approach for evaluating polymer properties. For reactive systems we shall limit ourselves to the thermal mechanical analyser (TMA) and the dynamic mechanical thermal analyser (DMTA). 

These differences were removed when one presented the data as a function of conversion, instead of time, indicating that there are differences in curing between DMTA and TMA. 

A fundamental property that determines the state of a reacting system is its extent of cure or chemical conversion (a). Several papers have shown that there is a unique relationship between the glass-transition temperature (Tg) and a that is independent of cure temperature and thermal history. This may imply that molecular structures of materials cured with different histories are the same or that the changes in molecular structure do not affect Tg. There are generally accepted to be two approaches to modelling glass-transition-conversion relationships, namely thermodynamic and viscoelastic approaches. These are summarized in Table 3.8. 

In order to understand the mechanical properties of polymers it is usefid to think of them in terms of their viscoelastic nature. Conceptually we can consider a polymeric item as a collection of viscous and elastic sub-components. When a deforming force is applied, the elastic elements deform reversibly, while the viscous elements flow. The balance between the number and arrangement of the different components and their physical constants controls the overall properties. We can exploit these relationships to create materials with a broad array of mechanical properties, as illustrated briefly by the following examples. 

At the opposite end of the polyethylene spectrum are the so-called ultra low density products with a high concentration of short chain branching that inhibits crystallization. These materials are soft, flexible, and transparent we encounter these materials in applications such as medical tubing, meat packaging films, and ice bags. 

Other polymers, such as polycarbonate and polymethylmethacrylate, are hard, tough, and transparent. These materials are ideal for applications that are likely to experience severe impact. We find these polymers in bus shelters, motorcycle helmet visors, and jet fighter canopies. 

Polymers that are rigid at high temperatures are known as engineering plastics This class of polymers includes polyacetal and many nylons. These polymers are used in applications such as small gears in office equipment and under the hood of automobiles. 

The properties of polyurethanes can be tailored by prudent selection of their constituent monomers. They can be converted into elastic foams, which are widely used in upholstery, and are used as covers for the handles of various tools and implements, such as the soft touch grips on ball-point pens and power tools. 

D5026-01 Measuring the dynamic mechanical properties of plastics in tension 6721-5 

D5045 Plane-strain fracture toughness and strain energy release rate of plastics materials 572 

D5048 Measuring the burning characteristics and resistance to burn-through of solid plastics using 125-mm flame 10351 

D5207 Calibration of 20 and 125 mm test flames for small-scale burning tests on plastics materials lEC 695-11-3, 4 

Testing of failed component for its mechanical properties in order to assess its compliance with the specifications is an important step in failure analysis. The common property tested is the hardness. Hardness testing helps the analyst to assess or evaluate the heat treatment, tensile strength of the alloy, detection of work hardening or the deleterious 

The effect of surface modification on the mechanical properties of the PE-HD/MDH composites is shown in Table 4.7. The presence of surface modifiers has an effect on strength, modulus, and the elongation at break. However, surface modifiers have different effects on the strength and modulus of the composites. 

The increase of unmodified (MDH3) and surface modified by aminosilane (MDH2) magnesium hydroxide used in high-density polyethylene increases the strength and modulus and decreases the elongation as compared to PE-HD. Surface modification of 

Symbol of composite Strength at break (MPa) Standard deviation (MPa) Elasticity modulus (MPa) Standard deviation (MPa) Elongation (%) Standard deviation (%) 

Addition to PE-HD/MDH composites (samples numbers 10-18) polymeric coupling agent PE-g-MA resulted in a significant improvement in the mechanical properties of the magnesium hydroxide modified by fatty acids. 

Impact strength and flexural modulus are the mechanical properties that can most be improved by careful selection of mineral flllers, and the shape of the particle is important. Fibre-like wollastonite particularly improves the flexural modulus while cube-shaped calcium carbonate can improve both impact strength and modulus. Talc offers many options because it is capable of many different modiflcations and surface treatments. The high aspect ratio of glass fibres means that they can provide the greatest improvement in mechanical properties. 

Tensile properties are one of the most important ngle indications of the stroigth of a material. Mechanical properties of polymeric materials are often measured using standard test sample configurations. In these stiufies, a tentile dumbbdl-shaped test specimen which conforms to ASTM D638 was used for all measurements. 

Usually the bulk mechanical behavior of a polymer network is characterized by its stress-strain properties describing the deformation and fracture of the network under stress. 

Static mechanical testing involves applying a constant stress or strain to a gel sample in tension or compression. 

For uniaxial tensile testing, dog bone-shaped samples are placed between two clamps and stretched at constant extension rates. Similarly, for unconfined compression tests, cylindrical specimens are compressed between two parallel plates. From these experiments, three important quantities can be determined (Fig. 4.16)  

From the initial region of the stress-strain curve, Young s modulus E and the shear modulus G can be obtained. Both are a measure of the stiffness of a given material, which mirrors the resistance of an elastic body against deflection of an applied force. The point where the stress-strain curve abmptly falls down is known as the fracture point where the sample ruptures. Fracture stress and fracture strain are defined as the maximal stress and deformation (elongation or compression) that a sample can withstand. Material toughness can also be calculated from the area under the stress-strain curve up to ultimate fracture point. It is defined as amount of energy per unit volume required to cause a fracture in a material. 

2 Dynamic Mechanical Analysis (DMA) Storage and Loss Modulus Dynamic mechanical analysis (DMA) is typically performed to measure the viscoelastic behavior of polymer networks. A sinusoidal force (stress) is applied to a material and the resulting displacement (strain) is measured, allowing one to determine the complex modulus. 

Commercial literature usually contains some data on mechanical properties of test formulations. This information is frequently not very useful because it refers to a simple formulation (very different from real industrial formulations). The commercial data are determined for formulations freely selected by manufacturers and therefore cannot be compared between different manufacturers. Finally, these results are not presented in fundamental form which may guide the user in the selection of plasticizers for Ms needs. Open literature usually offers information aiming at analysis of reasons for the observed behavior of materials but the number of pubhshed studies is limited by interest and resources. 

No data were found on the effect of hydrogen bonding or other chemical interactions between the plasticizer and matrix polymer on mechanical properties of plastificate. Intuitively, it can be anticipated that interaction of the plasticizer with the polymer should increase tensile strength but this should be verified by experiment. 

It is expected from the nature of plasticization that the tensile strength of materials decreases with the increase in plasticizer concentratioa This is a generally eorrect assumption but many physical and experimental exceptions ean be found. In Section 7.5, 

Mechanical performance of material can also be influenced by the effect of the plasticizer on polymer crystallization. This was reported for plasticization of polylactide by fatty acid ester. This process requires not only the right combination of materials but also specific thermal conditions (in the reported study, crystalhzation was observed after exposing material to 100°C for 24 h). 

Two plasticizers (di-(2-ethylhexyl) phthalate and epoxidized soya bean oil) were used in the range of concentrations from 0 to 50 phr. Tensile strength of both plastifieates was very similar and almost linearly decreased with the increase in plasticizer concentration. 

The long molecular chain structure of UHMWPE confers mechanical properties as shown in Table 2.1. The melting temperature range of UHMWPE is between 125 andl35°C. 

The mechanical behaviour of UHWMPE is related to the average molecular weight, which is routinely inferred from intrinsic viscosity measurements. There are commonly used methods for calculating the viscosity average molecular weight (Mv) for UHMWPE based on the intrinsic 

The compressibility of a foam is determined by the ability of the gas to compress, its wetting power is determined by the properties of the foaming solution [4]. As in any disperse system, a foam may acquire the properties of a solid body, i.e. it can maintain its shape and it possesses a shear modulus (see below). 

One of the basic mechanical properties of foams is its compressibility [4] (elasticity) and a bulk modulus may be defined by 

By taking into account the liquid volume Vi, the modulus of bulk elasticity of the wet foam ( is given by 

the real modulus of bulk elasticity ( wet foam) is higher than E, ( dry foam). 

Stars with 32% PSt, (PSt/15-h-PIB/34)g-C8, showed -26 MPa tensile stress. There was no appreciable difference in the tensile properties of unextracted and MEK extracted star blocks [see (PSt/15-h-PIB/34)g-C8 and (PSt/16-h-PIB/34)g-C8]. The modulus and Shore A hardness were slightly higher for the unextracted star, (PSt/16-h-PIB/34)g-C8, which maybe due to the presence of PSt contamination which acts as a rigid filler. A dramatic difference in the tensile behavior was observed when PSt content was increased. Stars with low PIB block molecular weight and high PSt content (46%), e.g., (PSt/21-h-PIB/25)g-C8, showed plasticlike behavior, i.e., it showed a high modulus, a yield point, and a short draw. Ex- 

Evidently, the products exhibited excellent strengths and elongations (up to 26 MPa and 500%, respectively), in spite of the presence of 10-15% contaminants (PSt and/or PSt-b-PIB diblocks) in the samples. The strength of these star blocks is superior to those of the strongest PSt- 7-PIB- 7-PSt triblocks reported [77] to date. 

Compared to polydiene-based TPEs [34,72], PIB-based TPEs have somewhat lower strength ( 35 MPa vs 25 MPa). The lower strength of PIB-based TPEs has been postulated to be due to a different failure mechanism, or to the presence of diblock contamination, or to the existence of a diffuse interphase [77]. However, linear PSt-b-PIB-b-PSt triblock ionomers [78] show higher tensile strength than corresponding linear triblocks, which contradicts the postulate of 

It can be seen from the equations in section 5.3.3 that the mechanical properties of ferroelectrics are closely related to the piezoelectric properties. The more widely used mechanical constants and their effect on the ferroelectric polymers will be discussed here. 

The subscripts i and / take values 1. 6 following the convention in Fig. 5.6, with Ti, T2 and the tension stresses parallel to the 1, 2 and 3 axes respectively, and T, and T(, the shear stresses around the 1,2 and 3 axes. Similarly, Sj, S2, S3 are the relative tension strains and S4, S5, the shear strains. Therefore, like the piezoelectric coefficients, is assigned a matrix related to the crystal symmetry of the material  

The stiffness has a similar form, since it is the matrix inverse of s,y. 

The compliances associated with shear, S44, S55 and S55, are not practically useful. The components Sn, S22 and S33 are associated with extension or compression, while S21, S31 and S32 are related to Poisson s ratio, as described in section 5.3.5(d). Techniques for obtaining these compliances have been developed, and values for PVDF are reported in the literature [41]. 

Young s modulus Y describes the elastic compliance under tension  

In fact, the electrical properties have many time and temperature dependent characteristics in common with the mechanical properties. The significant measure of the charging and polarisation (dielectric) behaviour of a polymer insulator is its permittivity. This can be thought of as a parallel to mechanical compliance where the stress is replaced by the electric field or voltage, and the strain by the charge movement or polarisation. Then the equivalent to mechanical loss is electrical conductance loss or dissipation. 

In Chapter 13 we shall introduce a short section on some photo properties of polymers that are governed by phenomena similar to the behaviour presented above. The photo characteristics of polymers are becoming very important as they are the basis of the growing technology of organic light emitting diodes (OLEDs), which may very well displace liquid crystal displays in computers in the next few years. Here we concentrate on  

In so doing we use the normal spectroscopic functions of absorption coefficient and emission intensity. These allow us to monitor the movement of energy as a quantum called an exciton. This energy can be transferred to another molecule behaving as a quenching agent, or it can be trapped by dimeric excited state complexes formed by the polymer and called excimers or exciplexes. 

So in this chapter we shall start by examining the mechanical properties and see how they depend on temperature, time and morphology. 

Four important mechanical properties — modulus and compliance, elastic recovery, vibration damping and energy loss, flow and creep - wiU be dealt with in this section. 

The information available on the effects of fire-retardants on the mechanical properties of various polymers is given in Table 8.2. 

Polymer Filler None fire retardant grades Fire retardant grades Fire retardant grades  

Polymer Filler Tensile strength (MPa) Flexural modulus (GPa) Elongation at break (%) Strain at yield (%) Notched Izod impact strength (kj/m) Tensile strength (MPa) Flexural modulus (GPa) Elongation at break (%) Strain at yield (%) 

6 Nil Good Very poor Very good Poor 0.11 Poor Very poor Good Very poor 

SAN Nil Good Good Poor Poor 0.02 Good Good Poor Poor 

Different types of tests can be performed to measure the following mechanical properties of polymers  

Brittle and tough high polymers like polystyrene and PMMA have high strength and very low extensibility and whereas plastics like polyethylene and plasticised PVC have relatively high extensibility and require much more energy to produce rupture, this energy is represented by the area under the stress-strain curve. 

The applications of polymers as solids are usually related to their mechanical properties. These properties often define them as rubbery, glassy or elastomeric materials. Similar to polymer blends, the final properties of polyrotaxanes will de- 

Wilkes and coworkers studied polyrotaxanes derived from self-assembly of a polyurethane bearing paraquat moieties and BPP34C10 [130b]. The polyurethanes contained soft (poly(tetramethylene oxide)) and hard (paraquat ionene) segments. Interestingly, dynamic mechanical analysis indicated that polyrotaxanes had higher rubbery plateau moduli than the corresponding backbones. Thermal analysis revealed that the stability was enhanced by the formation of the polyrotaxanes. 

Beckham and coworkers studied the dynamic mechanical properties of poly(urethane-crown ether rotaxane)s [138]. No difference was observed between the backbone and polyrotaxane, probably because of the low min value (0.02). However, 13C solid-state NMR detected die presence of the crown ether as a mobile structure at room temperature. The same observation was seen in polyrotaxanes with ether sulfone and ether ketone backbones (77-80) [114]. Although no detailed properties were reported, the detection of the liquid-like crown ether provided very important information in terms of mechanical properties, because these properties are the result of molecular response to external forces. For example, mobile crown ethers can play the role of plasticizers and thus improve impact strength. 

Therefore, to supplement the limited data cunendy available, further research on these aspects is essential  

The properties of some PP grades with different melt flow indices and structure are compared in Table 12. It can be observed that an increase in mechanical properties is not necessarily reflected in a trend predicted only on the basis of molecular weight, and other structural parameters, particularly crystallinity, play a very important role. Hence, the prediction of the mechanical properties on the basis of molecular weight or melt flow rate should be treated with caution. Appropriate data for the properties of the material should always be consulted. 

The elastic properties of hydrates are important to understanding the sonic and seismic velocity field data obtained from the natural hydrates-bearing sediments. Data on the mechanical properties of CO2 hydrates are hmited. Table 10.3 shows the elastic properties of ice, CH4 hydrates, and CO2 hydrates. It should be noted that these properties may vary for different guests and occupancies. For example, Kiefte et al. [21] measured the compressional velocity of methane, propane, and hydrogen sulfide hydrates as 3.3, 3.7, and 3.35 km/s, respectively. 

Changes in the morphology and the degree of crystallinity have considerable effects on the mechanical properties of polymers. In particular, the deformation mode of polyethylene changes from uniform extension to necking behaviour above about 50% crystallinity, and while the yield-stresses increase with density, the strain at fracture apparently decreases. In understanding deformation mechanism, and so mechanical properties, morphological studies play a central part, 

Yoda and Kuriyama have considered the structural changes associated with the hot rolling of polyethylene. As the draw ratio increases, the angle of the chain axis to the roll direction decreases until the chain coincides with the draw 

Kolbeck and Uhlmann have considered the effect of high stress extrusion on the properties of several polymers - polypropylene, poly(vinylidene fluoride) and polyethylene. There was no substantial heating on deformation up to twenty-five times. Polypropylene and poly(vinylidene fluoride) could not be continuously extruded below the melting point and brittle fracture and necking was observed, while the tensile properties depend on draw ratio with yielding. Above 373 K annealing occurs but the product has a lower elongation to break. The properties of oriented nylon-6, polyfethylene terephthalate), - polypropylene, and polyethylene have been widely studied. 

Many conflicting results are presented which have to be resolved in many different polymeric systems. No single technique will resolve these problems, but a concerted effort with a wide range of techniques in many and varied polymeric systems will do much to establish general features, and develop general theories. 

A comprehensive study of the properties of acetylated wood was undertaken by the Forest Products Laboratory in Madison, Wisconsin, and included an investigation of the mechanical properties of acetylated wood (Tarkow etal., 1946). The property changes were not significant, but there was some variation between species. For example, Sitka spruce and basswood exhibited increases in strength and MOE upon acetylation to about 20 % WPG, whereas yellow birch showed a decrease in these properties at 16 % WPG. 

Larsson and Simonson (1994) studied the mechanical properties of acetylated Pinus sylvestris and Picea abies. The MOR and MOE decreased by about 6 % for pine, but increased by about 7 % with spruce samples after acetylation. Samples for this study were vacuum/pressure impregnated with acetic anhydride, excess anhydride was then drained off and samples were heated at 120 °C for 6 hours. The hardness of the acetylated wood samples was also found to increase, which was considered to result from the lower MC of the modified wood. Acetylated samples were also found to be less susceptible to deformation when subjected to varying RH. 

There have been reports in which acetylation has a detrimental affect upon mechanical properties. Reachon of Scots pine in an acetic anhydride/xylene solution for 4 hours at 145 °C resulted in a 50 % decrease in the tensile modulus (Ramsden etal., 1997). Spruce modified in acetic anhydride at 100 °C was found to exhibit a reduction in toughness of about 20 %, compared to unmodified wood (Reiterer and Sinn, 2002). 

The dynamic viscoelastic properties of acetylated wood have been determined and compared with other wood treatments in a number of studies. Both the specific dynamic Young s modulus (E /j) and tan S are lower in acetylated wood compared with unmodified wood (Akitsu etal., 1991, 1992, 1993a,b Korai and Suzuki, 1995 Chang etal., 2000). Acetylation also reduces mechanosorptive creep deformation of the modified wood (Norimoto etal., 1992 Yano etal, 1993). In a study of the dynamic mechanical properties of acetylated wood under conditions of varying humidity, it was concluded that the rate of diffusion of moisture into the wood samples was not affected by acetylation (Ebrahimzadeh, 1998). 

The acoustic properties of wood are changed by acetylation and there have been several reports of the utilization of acetylated wood in musical instruments (Yano etal., 1986a, 1988, 1993 Obataya, 1999). Both the sound velocity and sound absorption decrease as the WPG of wood is increased. 

The relationship between microstructure and physical properties of ternary nanocomposites has been the subject of intense investigation due to their very complex nature. In this section, the mechanical properties of polymer blend nanocomposites are reviewed in the context of their microstructure. Following this, the various strategies that have been employed to obtain improved filler dispersion and interfacial interactions are mentioned. 

Generally, the overall mechanical performance of composites depends on (1) the nature of the components, (2) the quality of the interface between the components, (3) their architecture, and (4) their preparation procedure. The effects of preparation method on the final microstructure have already been covered in Section 2.2, so only the effects of the different microstructures on the mechanical properties and the importance of the interfacial properties are discussed. 

In virtually all applications, polymer materials have to be subjected to a loading force in some way or other. Hence, the assessment of mechanical properties is very important for the design of polymer materials for various applications. Polymer materials are more sensitive to the service temperature and other environmental effects compared with conventional materials. Hence, the data for mechanical properties, measured using conditions similar to a service environment, should be used for design rather than standard data available in the literature. 

When an elastic body is subjected to a tensile or compressive stress, the strain changes proportionally with stress according to Hooke s law, as given next  

Where a is the longitudinal stress, e is corresponding strain, and E is called Young s modulus (or the modulus of elasticity). Similarly, in shear deformation, the modulus is called the shear modulus or the modulus of rigidity (G). When a hydrostatic force is applied, a third elastic modulus is used the modulus of compressibility or bulk modulus (K). It is defined as the ratio of hydrostatic pressure to volume strain. A deformation (elongation or compression) caused by an axial force is always associated with an opposite deformation (contraction or expansion) in the lateral direction. The ratio of the lateral strain to the longitudinal strain is the fourth elastic constant called Poisson s ratio (v). For a small deformation, elastic parameters can be correlated in the following way  

In a rubbery network, Poisson s ratio is often close to 0.5 and hence shear modulus can be determined by dividing the elastic modulus by 3. 

Because ECMs store, transmit, and dissipate energy as part of their physiologic function, it is important to understand and characterize their mechanical properties. The mechanical properties of developing and adult tissues have been studied extensively. It is important to relate changes in mechanical properties of ECMs and mechanical loading to structural changes that are observed at the microscopic and gross levels. 

The presence of siloxane along with phosphorus moiety in bifunctional epoxy system exhibited synergism in establishing flame retardancy, thermal stability and mechanical properties. Hence, we extended our investigation to find out the effect of siloxane and phosphorus moiety and POSS 

The resin systems cured with BAPPO showed significant improvement in tensile, flexural and hardness properties, which are given in Table 3.3. 

For instance, the tensile and flexural strength of TGDDM cured with DDM is found to be 70 MPa and 130 

The effect of nano reinforcement (amino-POSS) was also dominant in the BAPPO cured systems as compared to the DDM cured systems (Table 3.4). The amine-terminated POSS reinforced tetrcdunctioncil epoxy nanocomposites exhibited the best results for the phosphorus (DOPO-based) skeletal modified tetra epoxy systems. This attention grabbing behavior may be attributed to the presence of additional crosslinking sites offered by POSS nano reinforcement paving the way 

Many researchers have shown that incorporation of nanoscale dimension particles (inorganic fillers, nanotubes, nanofibers etc) into a polymer matrix enhances the mechanical properties of the polymer without significantly raising its density or sacrificing its light transmission property. For instance, the Toyota research groups 

Maiti et al. [14] have studied the effects of different nanoclays (namely, NA, 10A, 20A, and 30B) on the properties of BIMS rubber. They have characterized the clays and the rubber nanocomposites by means of FTIR, , and XRD. 

The X-ray diffraction peaks observed in the range of 3°-10° for the modified clays disappear in the rubber nanocomposites. photographs show predominantly exfoliation of the clays in the range of 12 4 nm in the BIMS. Consequently, excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus is observed by the incorporation of the nanoclays in the BIMS. Maiti and Bhowmick have also studied the effect of solution concentration (5, 10, 15, 20, and 25 wt%) on the properties of fluorocarbon clay nanocomposites [64]. They noticed that optimum properties are achieved at 20 wt% solution. At the optimized solution concentration, they also prepared rubber/clay nanocomposites by a solution mixing process using fluoroelastomer and different nanoclays (namely NA, 10A, 20A, and 30B) and the effect of these nanoclays on the mechanical properties of the nanocomposites has been reported, as shown in Table 4 [93]. 

In addition, Maiti and Bhowmick [93] also used fluoroelastomers having different microstructure and viscosity (Viton B-50, Viton B-600, Viton A-200, and VTR-8550). Viton is a terpolymer of vinylidene fluoride (VF2), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). Even with the addition of only 4 phr of clay in Viton B-50, the tensile strength and modulus improved by 30-96% and 80-134%, respectively, depending on the nature of the nanoclays. The better polymer-filler interaction in the case of NA clay and the fluoroelastomers has 

This section contains two primary topics. The first is polymer rheology, which is concerned with how polymeric materials flow when they are placed under stress. Also of interest are the mechanical properties of polymers, particularly their elasticity. The combination of viscous effects with elastic phenomena is called viscoelasticity. 

The ratio of any value of the stress to the corresponding value of the strain is called the modulus. It is a direct measure of a material s resistance to deformation. Only in the low-strain region of the curve are the stress and strain directly proportional to one another. Therefore, only in this region is the modulus a constant. 

When the strain reaches a value called the elongation at yield, the curve becomes very non-linear. The stress at this point, the yield stress is sufficiently high to move the crystallites around in their very viscous surroundings, and to cause them to melt and then recrystallize in new orientations that partly relieve the stress. 

The curve then increases monotonically until rupture occurs. The strain at this point is called the maximum extensibility and the stress the ultimate strength. The area under the curve up to the rupture point is also of interest. It corresponds to the integral of fdL, and is therefore the work or energy required for rupture. It is the standard measure of toughness. The larger the area, the tougher the material. 

The next type is hard and brittle, for example polystyrene. Hard refers to the fact that the initial slope and modulus are large, and brittle is another way of saying the maximum extensibility is very small. 

In addition to specific properties of interest for a particular application of a material, its elasticity, compressive and tensile strength, deformability, hardness, wear-resistance, brittleness and cleavability also determine whether an application is possible. No matter how good the electric, magnetic, chemical or other properties are, a material is of no use if it does not fulfill mechanical requirements. These depend to a large extent on the structure and on the kind of chemical bonding. Mechanical properties usually are anisotropic, i.e. they depend on the direction of the applied force. 

Ionic crystals can be cleaved in certain directions. Fig. 19.1 shows why the exertion of a force results in cleavage if two parts of a crystal experience a mutual displacement by a shearing force, ions of like charges come to lie side by side and repel each other. The displacement is easiest along planes which have the fewest cation-anion contacts. In 

Inorganic Structural Chemistry, Second Edition Ulrich Muller 2006 John Wiley Sons, Ltd. 

Since fibrous monolithic ceramics are intended for use in applications where stresses are primarily generated due to bending, strength and work-of-fracture in flexure are measured to evaluate their basic mechanical properties. In addition, factors determining the manner of crack propagation should be 

5 (a) Low-magnification SEM composite showing three sections of a fibrous monolith with a [0°/90°] architecture (b) cross-sectional view of FM fabricated with a thin web of Si3N4 reinforcing the BN cell boundary (adapted from ref. [1]). 

6 Low-magnification SEM micrograph of polished sections, showing three-dimensional representations of the submillimeter structure of two architectures of Si3N4/BN FM (adapted from ref. [29]). 

In unidirectional FMs, fracture can initiate when the tensile stress carried by the cell exceeds the strength of the cell [1], This is generally favorable when the cell boundaries are tough in comparison to those of the cells. A 

In the following sections these factors will be considered briefly in relation to plastics. 

Strength and Stiffness. Thermoplastic materials are viscoelastic which means that their mechanical properties reflect the characteristics of both viscous liquids and elastic solids. Thus when a thermoplastic is stressed it responds by exhibiting viscous flow (which dissipates energy) and by elastic displacement (which stores energy). The properties of viscoelastic materials are time, temperature and strain rate dependent. Nevertheless the conventional stress-strain test is frequently used to describe the (short-term) mechanical properties of plastics. It must be remembered, however, that as described in detail in Chapter 2 the information obtained from such tests may only be used for an initial sorting of materials. It is not suitable, or intended, to provide design data which must usually be obtained from long term tests. 

In many respects the stress-strain graph for a plastic is similar to that for a metal (see Fig. 1.2). 

At low strains there is an elastic region whereas at high strains there is a nonlinear relationship between stress and strain and there is a permanent element to the strain. In the absence of any specific information for a particular plastic, design strains should normally be limited to 1%. Lower values ( 0.5%) are recommended for the more brittle thermoplastics such as acrylic, polystyrene and values of 0.2-0.3% should be used for thermosets. 

The effect of material temperature is illustrated in Fig. 1.3. As temperature is increased the material becomes more flexible and so for a given stress the 

The corrosion resistance of low-alloy steels is not significantly better than that of mild steel for aqueous solutions of acids, salts, etc. The addition of 0.5% copper forms a rust-colored film preventing further steel deterioration small amounts of chromium (1%) and nickel (0.5%) increase the rust 

5 to 9% Cr I or oil refinery applications involving high-sulfur process streams, e.g., pipe stills. 

CuCr (Corten) Rust-resisting steels for structural applications. 

Tabic 3.9. Comparison of Mild and Low-Alloy Quenched and Tempered Steels (111 

Relative total weight of other steel required for  

Property Test Density — 0.92glcnr (high-pressure polymers) Density = 0.94 gtcm high-pressure polymers Density — 0.95 glcm Ziegler-type polymers Density — 0.96 glcnr Phillips-type polymers Density — 0.9S g/cnr polymethylene 

Tensile strength (Ibf/in ) BS903 2200 1800 1500 1300 — 3000 3200t 3350t 3350t -4000 -5000 

A measure of the stiffness of a polymer is the modulus of elasticity (Young s modulus) E. It can be calculated fi om the stress-strain curve as the slope in the linear region of Hooke s law. It should be considered that due to the definition E = o/e for rubberlike materials which show a rather large extension e at quite 

The general correlations of structure and properties of homopolymers are summarized in Table 2.13. Some experiments which demonstrate the influence of the molecular weight or the structure on selected properties of polymers are described in Examples 3-6 (degree of polymerization of polystyrene and solution viscosity), 3-15, 3-21, 3-31 (stereoregularity of polyisoprene resp. polystyrene), 4-7 and 5-11 (influence of crosslinking) or Sects. 4.1.1 and 4.1.2 (stiffness of the main chain of aliphatic and aromatic polyesters and polyamides). 

Nearly all structure/properties relationships that were discussed for homopolymers are also valid for copolymers. Additional dependencies exist as a result of the composition and structure of the different types of copolymers. 

In the case of statistic copolymers of two monomers (binary copolymers) the glass transition temperature steadily changes with the molar amounts of the two monomers. In many cases, a similar behavior is observed with some mechanical properties (tensile strength, impact strength, stiffness, and hardness) (see Chap. 1). Deviations can occur in copolymers, which contain only a few percent of one comonomer. 

In general, block copolymers are heterogeneous (multiphase) polymer systems, because the different blocks from which they are built are incompatible with each other, as for example, in diene/styrene-block copolymers. This incompatibility, however, does not lead to a complete phase separation because the polystyrene segments can aggregate with each other to form hard domains that hold the polydiene segments together. As a result, block copolymers often combine the properties of the relevant homopolymers. This holds in particular for block copolymers of two monomers A and B. 

5 Mo ) 1.25 CrMo 1 2.25 CrMo ( 6 to 12 CrMoVW) High creep strength for 1. pressure vessels such as boilers operating at elevated temperatures and 2. oil refinery vessels such as crackers and reformers with high hydrogen pressures. 

Typically COC has a higher modulus than high density polyethylene) (HDPE) or poly(propylene) (PP). Thus, it is the more brittle than ordinary poly(olefine)s. 

However, branched COC chains increase the flexibility and processability of the polymers without significantly weakening the optical properties (45). 

Hou et al. (43) reported the poly(vinyl alcohol) nanocomposites using single walled (SWNT), few walled (FWNT) and multi walled (MWNT) nanotubes. The nanotubes were covalently functionalized to generate acid functionalities on the sidewalls. The incorporation 

In polyamide nanocomposites (39), the storage modulus of the composites was reported to increase steadily with increasing the loading of MWNTs. At 2 wt% concentration of the nanotubes, the storage modulus of the nanocomposite was measured to be 1.97 GPa, which is an increase of 54% than the storage modulus of 1.28 GPa for the pure polyamide matrix. 

Cao et al. (44) reported nanotube incorporation in Chitosan with medium molecular weight. The polymer, MWNTs and the composites with different fractions of MWNTs were characterized by X-ray diffraction. The MWNTs exhibited a sharp diffraction peak at about 20 

Polymer nanocomposites with medium density polyethylene were reported with a variety of fluorinated and un-fluorinated nanotubes (37). The nanocomposites consisting of 1 wt% F-SWNT-C H (fluorinated and surface treated nanotubes) nanotubes showed an increase in tensile strength by 52.4%, modulus by 15.9% and elongation by 18.9% as compared to the pure polymer. The composites with 1 wt% F-SWNT-CnH23 (fluorinated and surface treated nanotubes) had an increase of 28.3% in modulus as compared to the pure polymer. The tensile strength also increased from 4.33 MPa for the pure polymer to 5.01 Mpa for the nanocomposite, the elongation at 

Kim et al. (35) studied the thermotropic liquid crystalline polymer (TLCP) nanocomposites with varying extents of nanotubes. The mechanical performance of the nanocomposites has been demonstrated 

During cold working, polycrystaUine metals deform by mechanisms involving slip and, where slip is restricted, rotation of the individual grains. Both processes, of course, must satisfy the condition that the interfaces, along which the grains are connected. 

The absence of a lattice-based mechanism, such as slip planes, does not necessarily preclude aU deformation in brittle materials. Plastic flow can proceed in other modes. For example, at temperatures of about 40 percent to 50 percent of their melting points, grain-boundary shding can become important. Grain-boundary sliding is beheved to be the major contributor to the superplasticity observed in some polycrystal-hne ceramics. 

Product Tensile modulus Stress yield IS0527-1, -2 IS0527-1, -2 (MPa) (N/mm2) (MPa) (N/mm2) Nominal strain Strain yield break IS0527-1, -2 IS0527-1, (%) -2 (%)  

One interesting example is electroless Ni(P). Electroless Ni(P) is harder and has better corrosion resistance than electrode-posited Ni(P). Nonmagnetic electroless 

Ni(P) is used as an underlayer in high-density metallic memory disk fabrication to improve the mechanical finish of the surface. Thus, hardness, wear resistance, and corrosion resistance have been major properties determining the technological applications of electroless Ni(P) in the electronic, aerospace (stators for jet engines), automotive, machinery, oil and gas production, power generation, printing, and textile industries. 

It is interesting to note that Brenner and Riddell [1, 43] accidentally encountered electroless deposition of nickel and cobalt during the electrodeposition of nickel-tungsten and cobalt-tungsten alloys (in the presence of sodium hy-pophosphite) on steel tubes in order to produce material with better hardness than steel. They found deposition efficiency to be higher than 100%, which was explained by the contribution of electroless deposition to the electrodeposition. 

The energy of atomization of COF has been calculated (HUckel calculations) to be 1718 kJ mol [1441] force constant calculations give a value of 1460-1650 kJ mol [2034]. 

The density of liquid COFj (in each case at the saturated vapour pressure), determined pyknometrically, is given by Equation (13.15) [1756]. At the normal boiling temperature of 

this equation corresponds to a density value of 1.017 g cm 3, compared to the approximate value of 1.17 estimated from molecular data [174a]. At the melting point, the density of the liquid corresponds to 1.129 g cm 3 [1756] this corresponds to a molar volume, at the melting point, of 58.46 cm3 mol . The density of solid COFj at the temperature of boiling liquid air was determined to be 1.388 g cm 3 [1756]. 

Lennard-Jones potential parameters ( r = 0.445 nm, t k = 224 K) have been estimated for COFj [1588]. 

Selected mechanical properties of liquid COFj have been estimated from molecular data [1683]. The calculated values for the molar volume, thermal expansion coefficient (a), and isothermal compressibility (3), are recorded as a function of temperature in Table 13.16. 

Crystalline melting point (°C) Number average molecular — -108 -108 -108 -108 -108 125 -130 -130 -130 -133 136 

The maximum permissible loading of low-alloy steels, according to the ASME code for pressure vessels, is based on proof stress (or 

FIGURE 3. 24 c-Axis orientation function of take-up velocity showing influence of molecular weight. (From Nadella, H.P., Henson, H.M., Spruiell, J.E. White, J.L. J. Appl. Polym. Sci., 1977, 21, 3003. With permission.) 

As is well known, melt-spun fibers are not satisfactory for use in most applications until they are drawn. Drawing increases strength and modulus, and decreases elongation. On a macroscopic scale, drawing seems to be a simple flow process. However, on a microscopic scale, profound changes occur to the fiber structure. 

A material which is hard is able to resist wear, scratching, indentation and machining. Its hardness is also a measure of its ability to cut other materials. Hard materials are required for cutting tools and for parts where wear must be kept to a rtnnimurtL 

A britde material will break easily when given a sudden blow. This property is associated with hardness, since hard materials will often be britde. Britde materials cannot be used in the working parts of power presses, which are subjected to sudden blows. 

A ductile material can be reduced in cross-section without breaking. In wire-drawing, for instance, the material is reduced in diameter by pulling it through a circular die. The material must be capable of flowing through the reduced diameter of the die and at the same time withstand the puUing force. 

A malleable material can be rolled or hammered permanently into a different shape without fracturing. This property is required when forging. 

A material which is elastic will return to its original dimensions after being subjected to a load. If loaded above a point known as the elastic limit, the material will not return to its original dimensions and will be permanently deformed when the load is removed. Elasticity is essential in materials used in the manufacture of springs. 

Nishino et al. [56] have studied the elastic modulus of the crystalline regions of cellulose polymorphs in the direction parallel to the chain axis, which was measured by X-ray diffraction. The values of cellulose 

Mechanical Properties of Various Nanocelluloses Obtained from Different Sources Elastic Modulus in Axial Direction (GPa) Elastic Modulus in Transverse Direction (GPa) Tensile Strength (Tensile Testing) (GPa) 

and IVj were 138, 88, 87, 58, 75 GPa, respectively. This indicates that the skeletons of these polymorphs are completely different from each other in the mechanical point of view. The crystal transition induces a skeletal contraction accompanied by a change in intramolecular hydrogen bonds, which is considered to result in a drastic change in the Ej value. 

A detailed study on the topography of elastic and adhesive properties of individual wood-derived CNCs using atomic force microscopy (AFM) was made by Lahiji et al. [59]. The AFM experiments involving high-resolution dynamic mode imaging and jump-mode measurements were performed on individual CNCs imder ambient conditions with 30% relative humidity (RH) and under a N atmosphere with 0.1% RH. The transverse elastic 

FIGURE 8.11 (a) (1 0 0) projection showing slip possibilities on (0 0 1) (A) planes. Note 

Observations of the damaged morphology of the product particles after impact tests are in agreonent with the breakage mechanisms observed during nanoindentation 

FIGURE 8.12 (a) Load-displacement curves from indentation on faces (0 0 1) and (1 0 0) of aspirin carried out at loading rates of 5 mN/s and at similar depths. Pop-ins can be observed on both curves, indicated by the arrows, (b) Morphological sketch of aspirin drawn using SHAPE and scanning electron micrograph of a representative aspirin particle, (c) SEM image of an indent of aspirin (1 0 0) face. Source Adapted from Olusanmi et al. [79]. Reproduced with permission of Elsevier. 

Selection of solid-form and appropriate particle attributes is one of the foundation elements of drng product design. One challenge is to deliver consistent dissolution rates of API particles used in formulations. Additionally as the chemistry route is optimised and the final step isolation is refined, there is a need to be able to define the potential impact of changes of API particle size and shape on product efficacy. The model used to predict the dissolution kinetics of the monodisperse crystalline 

TABLE 8.7 Shape Eactors of the Three Different Celecoxib Crystals and the % Surface Area of the Eorms  

BORONIC ACID SUBSTITUTED SELF-DOPED POLYANILINE 

It is also shown in Table 5.2 [15] that the flexural strength and flexural modulus 

In order to choose the type of coating and determine the necessary coating thickness, many practice-oriented tests would have to be carried out in which the evaluation of damage areas and choice of service conditions are not always comparable [42-44]. However, information on the various thickness ranges of the PE coating in Ref. 4 was deduced from such experiments. 

A ductile material can be reduced in cross-section without breaking. In wire-drawing, for instance. 

A malleable material can be rolled or hammered permanently into a different shape without fracturing. This property is required when forging, where the shape of the metal is changed by hammering. Lead is a malleable material, as it can easily be shaped by hammering, but is not ductile since it is not strong enough to withstand a load if attempted to be drawn into wire. Heat may be used to make a material more malleable. 

The tensile modulus E has been obtained from the initial slopes of the stress-strain curves as shown in figure II - 17 and II - 1S. A relatively large force has to be applied to obtain a small deforaiaiion for a glassy polymer whereas for elastomers a small force is sufficient to obtain a large deformation. At a cenain stress the material may break or mav show 

Application of higher molding pressures at the gel point of a resol-type phenolic resin led to a reduction of voids in the matrix, improving the impact strength, as observed by Megiatto Jr. et al. (2009) in phenolic composites reinforced with sisal fiber. 

Mechanical properties are critical for many composite applications. The properties of the composites depend on the combination of the properties of the matrix and the reinforcing agent or fiber. The properties of polymer composites reinforced with short fibers depend on such factors as the fiber/ matrix interaction, the orientation and volume fraction of the fiber, the fiber aspect ratio (defined as Lid where L and d correspond to the fiber length and diameter, respectively) (Chawla, 1998) and processing conditions (Thomas and Pothan, 2008). Different tests can be used to evaluate the mechanical properties of the composites, such as tensile, flexural or impact resistance tests (Izod or Charpy tests). 

The impact test evaluates the improvement of the thermoset properties (classified as fragile) compared to composites reinforced with fibers (synthetic or natural fibers) or thermoplastic materials (Chawla, 1998). 

Kumar et al. (2009) investigated the tensile and flexural properties of phenolic composites reinforced with coir and glass fibers. The best tensile 

Mathur et al. (2010) used multi-walled carbon nanotubes (MWCNTs) to reinforce phenolic resins using both the wet and dry dispersion techniques before molding. The phenolic composites reinforced with 5% MWCNTs exhibited a flexural strength 158% higher than those of neat phenolic thermosets. 

The fracture toughness of poly(vinyl chloride), with a low degree of crystallinity, cannot be readily explained by simple fracture mechanic theories, since there is a marked yielded zone, as well as craze-crack propagation involved in all fractures. 

Environmental stress cracking of Nylon-6, 6 in inorganic salt solutions has been examined by X-ray dispersive techniques to analyse adsorbed ions on the fracture surface. The mechanism of adsorption of zinc cations on to the carbonyl groups and solvation of the cations with water to weaken the binding between the chains has been confirmed. Different cations behave differently, and lithium cations require solvent as a bridge. Different fracture surface features result from the two crazing salt solution types. 

The effect of annealing on the properties of ultra-high modulus linear polyethylene has been studied. There was a good correlation between the modulus and lamellae thickness irrespective of annealing temperature. On drawing, annealing, and rapid quenching to room temperature there is an immediate fall in 

Shear bands have been observed in polypropylene under compression at low temperature, which is the first observation of this mechanism of deformation in such a highly crystalline polymer. There are previous reports of craze formation in poi)q)ropylene, but not shear bands which are normally associated with glassy polymers. Two discrete sets of shears band at 35° to 42° to the compression axis have beat seen. It appears to be associated with sliding between lamellae and along spherulite boundaries. 

Residual strains in injection moulded Nylon-6 have been measured but the stress distribution is parabolic, with a compressive stress as much as 6 Mn m on the surface and a tensile one in the middle of 4 Mn m dimension in water reverses this distribution making it tensile on the surface. This has been attributed to recrystallization in presence of water and not simple to adsorption and volume changes. The yield and fracture toughness of the Nylon-6 is affected by water content, moulding conditions due to changes in yield stress. There is a brittle to ductile transition with temperature associated with cc-transition. The yield stress increases linearly with crystallinity, whereas the fracture toughness falls consistent with a move from plane strain to plane stress conditions. 

Since molded graphite does not deform plastically, at least at low temperatures, measurement of its tensile strength is difficult and unreliable. Instead, it is preferable to measure flexural (transverse) strength, which is a more reproducible property. Tensile strength is generally 50 to 60% of the flexural strength and compressive strength is approximately twice as much. 

S = fiexural strength P = ioad at rupture L s support span b = specimen width d s specimen thicknessf l 

This characteristic makes it difficult to interpret hardness measurements except with the ball-identation method which can be considered reasonably accurate. The resulting contact hardness is defined as the average pressure required to indent the material to a depth equal to 2/100th. of the radius of the ball. Other hardness-meeisurement methods such as the Scleroscope (which is the measure of the rebound height of a falling diamond-tipped hammer) are convenient but, as they are not based on the same principle, cannot readily be correlated with the ball hardness. 

Frictional Properties. Molded graphite materials have inherently low friction due to the ease of basal-plane slippage and the resulting low shear strength mentioned above. 

When graphite is rubbed against a metal or ceramic surface, a thin transfer film is formed on the rubbed surface. This lowers the coefficient of friction which can be less than 0.01 after the transfer film is fully developed. 

Unnotched Izod impact No break No break No break No break  

Note that all data are based on ISO test methods except for PEKK which is based on ASTM methods.  

of atoms Compressive modulus (A) (MPa) Compressive strength (MPa) Compressive modulus (B) (GPa) Yield length (A) 

When the applied stress, g , inereases to its allowable maximum given by the intrinsic strength, S, of the crack, a catastrophic failure occurs. Equation (8.6) becomes  

If n(o-) denotes a flaw distribution, then the number of the flaws which will fail between a and c + dc is n a)dG. The total number of flaws whose strengths are less than a is  

According to the Weibull distribution, the empirical form of the cumulative flaw distribution is given by  

commonly referred to as the cumulative failure probability, is defined as the probability of breakage below a stress level a. Consequently 1 — F a) is the survival probability. Assuming a group of M samples, F a) is calculated as below  

The failure stresses are listed with increasing magnitude as (Ti, ct so that the cumulative failure probability F ffi) can be determined. In the Weibull plot, the breaking stress cr is plotted versus the cumulative failure probability f. To compare different Weibull distributions, we use the median breaking stress, 7 , which corresponds to 50% failure probability. Combining Eqs. (8.9) and (8.10) we obtain  

These include both destructive and non-destructive tests. The former may include tensile, compression or shear testing, and other product-related tests such as tear, abrasion, flexural and impact testing. Non-destructive tests may vary from simple visual examination and weight, density or hardness tests to ultrasonics, X-ray analysis, thermography or other sophisticated techniques. 

Drawn from the data R.A.V. Raff in Encyclopaedia of Polymer Science and Technology, published 

In a hydrophilic matrix, the glassy soluble polymer transforms into a rubbery state as the water plasticizes it and reduces the T. The glassy/rubbery polymer interface will constitute the swelling (transition) front [9]. 

In the case of inert matrices, mechanical properties will affect the integrity of the system and drug release. All the polymers mentioned before for inert matrices have an amorphous structure with plastic deformation as dominant densification 

In addition, in the case of ethylcellulose, there is a correlation between the viscosity grade and the elastic nature, following the rank order 100 cp 45 cp 20 cp 10 cp. The dependence of the compressibility and compactibility on viscosity grade seems to be due to the increase in polymer order as a result of increased molecular 

Compressive strength, flexural strength, and the elastic modulus of magnesia-phosphate cement products are affected by composition and water content. The compressive strength, at different times, for seven phosphate-cement concretes is plotted in Fig. 

The compressive strength and setting time (Gillmore needle ASTM C266-74) for several phosphate-cement concretes containing different amounts of polyphosphate in ammonium phosphate solutions are plotted in Fig. 9. At 2 hours, 24 hours, and 7 days the compressive strength increases 

Handbook of Plastics Testing and Failure Analysis, Third Edition, by Vishu Shah Copyright 2007 by John Wiley Sons, Inc. 

Stress. The force applied to produce deformation in a unit area of a test specimen. Stress is a ratio of applied load to the original cross-sectional area expressed in Ib/in.l 

Strain. The ratio of the elongation to the gauge length of the test specimen, or simply stated, change in length per unit of the original length (A///). It is expressed as a dimensionless ratio. 

Elongation. The increase in the length of a test specimen produced by a tensile load. 

Yield Point. The first point on the stress-strain curve at which an increase in strain occurs without the increase in stress. 

Structural Aspects, Morphology and Fiber/Film Processing 

9-7 fa-c Correlation of modulus, tensile strength, conductivity and draw ratio for P(TV) fibers. After Reference [315], reproduced with permission. 

Flg 9-9 (a-b) Young s Modulus and Tensile strength for trans-P(Ac) as function of draw ratio. After Reference [204], reproduced with permission. 

The ability to change film dimensions by altering the water content in the films has driven Okuzaki et al. to employ PEDOT PSS as an electro-active polymer actuator. Film contractions of 2.4% to 4.5 % depending on relative humidity were realized by applying an electrical bias and removing water from the films due to Joule heating. 

Stress-strain diagrams of PEDOT PSS at different levels of relative humidity. (Reprinted from Sxfnth Met 159(5-6) 473-479, U. Lang, N. Naujoks, and J. Dual, Mechanical Characterization of PEDOTiPSS Thin Films. Copyright 2009, with permission from Elsevier.) 

According to the principles of action and application, the organic antiblocking, release, and slip additives are  

If the above statements are correct for an additive, the additive should not affect most mechanical properties. Impact resistance may be exception to some degree because it is sensitive to any imperfections in the material, and incompatible material may cause formation of such imperfections. 

If observations show that tensile strength is decreased, because of addition of antiblocking or slip agent, it suggests that the additive is soluble in polymer and interferes with its erystal-lization or affects crystalline region. If the elongation is increased, it most likely means that the additive that eauses this inerease acts as a plasticizer. 

Two mold release agents (polyolefin and fatty acid) were used in concentration of up to 2 wt% in polyetherimide. At their optimal levels (0.1 to 0.5 wt%), the mold release agents did not affect properties of polyetherimide.  

Fluoropolymer additive was used in blown film from metallocene linear low density polyethylene. This additive improves processability and eliminates melt fracture. The fluoropolymer additive presence was associated with substantial increase of dart impact strength (84%), and it had no effect on tear strength. Some slip agent of undisclosed composition was also used. With 3 wt% shp additive the dart impact strength was reduced to the same level as it had without fluoropolymer additive. The tear resistance was not affected by the addition of slip agent.  

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Before we can explore how reactor conditions can be chosen, we require some measure of reactor performance. For polymerization reactors, the most important measure of performance is the distribution of molecular weights in the polymer product. The distribution of molecular weights dictates the mechanical properties of the polymer. For other types of reactors, three important parameters are used to describe their performance ... 

The mechanical properties of waxes and solid paraffins are of considerable importance for most applications and numerous tests have been developed for characterizing the hardness, the brittleness, and resistance to rupture. 

The publication of interstate Standard GOST 30415-96" Steel. Non-destructive inspection of mechanical properties and microstructure of metal products by magnetic method" - is the long-expected event for works laboratories and development engineers of non-destructive test means. 

Not to overload the Statidard, three supplements are predetermined for it. The Supplement A (compulsory ) with the list of statistics is due to compulsory determination by non-destructive magnetic method of mechanical properties test. This Supplement provided the possibility to set the reasonable compromise between two opposite tendencies -to simplify utmost a body of mathematics or, on the contrary, to complicate it to such extent that it becomes inaccessible. 

NONDESTRUCTIVE MAGNETIC METHID OF INSPECTION OF THE MECHANICAL PROPERTIES OF CAST STEELS. 1. CONSTRUCTION OF CORRELATION MODELS and II. PRACTICAL APPLICATION OF CORRELATION... 

ELECTROMAGNETIC MONITORING OF MICROSTRUCTURE AND MECHANICAL PROPERTIES FOR COLD-ROLLED 12Kh2MFSR STEEL TUBE by V.A.Burganova, L.V. Kochman, V.A. Kuz mina and L.P. Chukanova, Vol.10, No. 4, 1974, pp. 432 -437... 

Information supplied by flaw visualization systems has decisive influence on fracture assessment of the defect. Results of expert ultrasonic examination show that in order to take advantage of AUGUR4.2 potentialities in full measure advanced methods of defect assessment should be applied using computer modelling, in-site data of material mechanical properties and load monitoring [4]. 

The radiation and temperature dependent mechanical properties of viscoelastic materials (modulus and loss) are of great interest throughout the plastics, polymer, and rubber from initial design to routine production. There are a number of laboratory research instruments are available to determine these properties. All these hardness tests conducted on polymeric materials involve the penetration of the sample under consideration by loaded spheres or other geometric shapes [1]. Most of these tests are to some extent arbitrary because the penetration of an indenter into viscoelastic material increases with time. For example, standard durometer test (the "Shore A") is widely used to measure the static "hardness" or resistance to indentation. However, it does not measure basic material properties, and its results depend on the specimen geometry (it is difficult to make available the identity of the initial position of the devices on cylinder or spherical surfaces while measuring) and test conditions, and some arbitrary time must be selected to compare different materials. 

The Institute has many-year experience of investigations and developments in the field of NDT. These are, mainly, developments which allowed creation of a series of eddy current flaw detectors for various applications. The Institute has traditionally studied the physico-mechanical properties of materials, their stressed-strained state, fracture mechanics and developed on this basis the procedures and instruments which measure the properties and predict the behaviour of materials. Quite important are also developments of technologies and equipment for control of thickness and adhesion of thin protective coatings on various bases, corrosion control of underground pipelines by indirect method, acoustic emission control of hydrogen and corrosion cracking in structural materials, etc. 

Electrons, protons and neutrons and all other particles that have s = are known as fennions. Other particles are restricted to s = 0 or 1 and are known as bosons. There are thus profound differences in the quantum-mechanical properties of fennions and bosons, which have important implications in fields ranging from statistical mechanics to spectroscopic selection mles. It can be shown that the spin quantum number S associated with an even number of fennions must be integral, while that for an odd number of them must be half-integral. The resulting composite particles behave collectively like bosons and fennions, respectively, so the wavefunction synnnetry properties associated with bosons can be relevant in chemical physics. One prominent example is the treatment of nuclei, which are typically considered as composite particles rather than interacting protons and neutrons. Nuclei with even atomic number tlierefore behave like individual bosons and those with odd atomic number as fennions, a distinction that plays an important role in rotational spectroscopy of polyatomic molecules. 

Many phenomena in solid-state physics can be understood by resort to energy band calculations. Conductivity trends, photoemission spectra, and optical properties can all be understood by examining the quantum states or energy bands of solids. In addition, electronic structure methods can be used to extract a wide variety of properties such as structural energies, mechanical properties and thennodynamic properties. 

The technological importance of thin films in snch areas as semicondnctor devices and sensors has led to a demand for mechanical property infonnation for these systems. Measuring the elastic modnlns for thin films is mnch harder than the corresponding measurement for bnlk samples, since the results obtained by traditional indentation methods are strongly perturbed by the properties of the substrate material. Additionally, the behaviour of the film under conditions of low load, which is necessary for the measnrement of thin-film properties, is strongly inflnenced by surface forces [75]. Since the force microscope is both sensitive to surface forces and has extremely high depth resolntion, it shows considerable promise as a teclnhqne for the mechanical characterization of thin films. 

Salmeron M B 1993 Use of the atomic force microscope to study mechanical properties of lubricant layers MRS Bulletin XVIII-5 20... 

Most properties of linear polymers are controlled by two different factors. The chemical constitution of tire monomers detennines tire interaction strengtli between tire chains, tire interactions of tire polymer witli host molecules or witli interfaces. The monomer stmcture also detennines tire possible local confonnations of tire polymer chain. This relationship between the molecular stmcture and any interaction witli surrounding molecules is similar to tliat found for low-molecular-weight compounds. The second important parameter tliat controls polymer properties is tire molecular weight. Contrary to tire situation for low-molecular-weight compounds, it plays a fimdamental role in polymer behaviour. It detennines tire slow-mode dynamics and tire viscosity of polymers in solutions and in tire melt. These properties are of utmost importance in polymer rheology and condition tlieir processability. The mechanical properties, solubility and miscibility of different polymers also depend on tlieir molecular weights. 

In block copolymers [8, 30], long segments of different homopolymers are covalently bonded to each otlier. A large part of syntliesized compounds are di-block copolymers, which consist only of two blocks, one of monomers A and one of monomers B. Tri- and multi-block assemblies of two types of homopolymer segments can be prepared. Systems witli tliree types of blocks are also of interest, since in ternary systems the mechanical properties and tire material functionality may be tuned separately. 

Polymers have found widespread applications because of their mechanical behaviour. They combine the mechanical properties of elastic solids and viscous fluids. Therefore, they are regarded as viscoelastic materials. Viscoelastic... 

In sorjDtion experiments, the weight of sorbed molecules scales as tire square root of tire time, K4 t) ai t if diffusion obeys Pick s second law. Such behaviour is called case I diffusion. For some polymer/penetrant systems, M(t) is proportional to t. This situation is named case II diffusion [, ]. In tliese systems, sorjDtion strongly changes tire mechanical properties of tire polymers and a sharjD front of penetrant advances in tire polymer at a constant speed (figure C2.1.18). Intennediate behaviours between case I and case II have also been found. The occurrence of one mode, or tire otlier, is related to tire time tire polymer matrix needs to accommodate tire stmctural changes induced by tire progression of tire penetrant. 

Ward I M 1971 Mechanical Properties of Solid Polymers (New York Wiley) p 329... 

Saunders S R J, Evans FI E and Stringer J A (eds) Workshop on Mechanical Properties of Protective Oxide Scales. Materials at High Temperatures vo 12 (Teddington)... 

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