Rheology and Mechanical Properties

Regarded as one of the cornerstones of physical science, is the Boltzmann s Law and Principle that developed the kinetic theory of gases and rules governing their viscosity and diffusion. This important work in chemistry is very important in plastics (Ludwig Boltzmann born in Vienna, Austria, 1844-1906). It relates to the mechanical properties of plastics that are time-dependent. 

As reviewed, a plastic when subjected to an external force part of the work done is elastically stored and the rest is irreversibly dissipated. Result is a viscoelastic material. The relative magnitudes of such elastic and viscous responses depend, among other things, on how fast the material is being deformed. It can be seen from tensile stress-strain (S-S) curves that the faster the material is deformed, the greater will be the stress developed since less of the work done can be dissipated in the shorter time. 

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The dry adhesive films on the two substrates to be joined must be placed in contact to develop adequate autoadhesion, i.e. diffusion of polymer rubber chains must be achieved across the interface between the two films to produce intimate adhesion at molecular level. The application of pressure and/or temperature for a given time allows the desired level of intimate contact (coalescence) between the two adhesive film surfaces. Obviously, the rheological and mechanical properties of the rubber adhesives will determine the degree of intimacy at the interface. These properties can be optimized by selecting the adequate rubber grade, the nature and amount of tackifier and the amount of filler, among other factors. 

Non-reinforcing fillers (passive) Ground calcium carbonate (CaCO ) Reduce formulation cost adjust rheology, and mechanical properties. 

Molecularly motivated empiricisms, such as the solubility parameter concept, have been valuable in dealing with mixtures of weakly interacting small molecules where surface forces are small. However, they are completely inadequate for mixtures that involve macromolecules, associating entities like surfactants, and rod-like or plate-like species that can form ordered phases. New theories and models are needed to describe and understand these systems. This is an active research area where advances could lead to better understanding of the dynamics of polymers and colloids in solution, the rheological and mechanical properties of these solutions, and, more generally, the fluid mechaiucs of non-Newtonian liquids. 

Epoxidized oils were also used to modify PLA Ali et ah (2009) reported that its use as a plasticizer to improve flexibility. Thermal and scanning electron microscope analysis revealed that epoxidized soybean oil is partially miscible with PLA. Rheological and mechanical properties of PLA/epoxidized soybean oil blends were studied by Xu and Qu (2009) Epoxidized soybean oil exhibited a positive effect on both the elongation at break and melt rheology. Al-Mulla et al. (2010b) also reported that plasticization of PLA (epoxidized palm oil) was carried out via solution casting process using chloroform as a solvent. The results indicated that improved flexibility could be achieved by incorporation of epoxidized palm oil. 

Antony, P., Puskas, J.E., and Kontopoulou, M. The Rheological and Mechanical Properties of Blends Based on Polystyrene-Polyisobutylene-Polystyrene Triblock Copolymer and Polystyrene. Proceedings of MODEST, International Symposium on Polymer Modification, Degradation and Stabilization, Budapest, Hungary, 2002. 

Processing aids are added to improve the processing characteristics of a material. They may increase the rheological and mechanical properties of a melted material. Acrylate copolymers are often utilized as processing aids. 

In the processing of foods and additives, rheological and mechanical properties, which determine end use properties are of primary significance. These properties are also related to others such as the impact of taste. Taste is the perception on the taste buds on the surface of the tongue, and colloidal properties will thus have an important role. Gels are also known to be used in many food products. The stability of food products is determined by colloidal stability in many systems (Dickinson, 1992 Friberg, 1976). 

Miilhaupt et al. has recently attempted to correlate the thermal, rheological and mechanical properties of polymers with spectroscopic fingerprints using multivariate analyses [11]. This approach is driven by the fact that polymer properties and... 

The crosslink density ultimately defines the rheological and mechanical properties of the polymer. Polymers that have a high crosslink density are thermosets and are infusible, insoluble, and dimensionally stable under load. These properties make epoxy resin systems useful as structural adhesives as well as important materials in other applications. Polymers that have a low crosslink density are more flexible and show greater resistance to stress concentration, impact, and cold. 

The results are reported of a study of the influence of stabilisers and antioxidants (Irganox B900 and Sandostab P-EPQ) on the rheological and mechanical properties of recycled PP and PVC. The effects of the number of reprocessing operations, reprocessing conditions, molecular parameters of the polymers and the type and content of stabilisers on the properties of the recycled polymers are discussed. 8 refs. 

A plasticiser plays an important role in the formulation of PVC and in determining its processability. The effects of the added small quantities of plasticiser on the rheological and mechanical properties of PVC/newsprint-fibre composites. The formulation of PVC/newsprint-fibre composites are modified by incorporating various concentrations as a plasticiser. Newsprint fibres are dispersed into the PVC matrix in a high shear turbine... 

Staniforth JN, Balchwal AR, Hart JP, Heng PWS. Effect of addition of water on the rheological and mechanical properties of mlcrocrystal-line celluloses. Int ] Pharm 1988 41 231-236. 

This chapter provides a broad overview of the subjects of polymer blends and lonomers. Specific topics concerning polymer blends Include the thermodynamics of mixing of polymer-polymer pairs, polymer Interfaces, rheology, and mechanical properties. For lonomers, the chemistry, structure, rheology and solution properties are discussed. 

There is a further complication in the analysis of polyesters (and several other polymers) and this is the presence of cyclic oligomers during the polymerization process, which are not removed from the commercial polymer. These oligomers will affect the rheological and mechanical properties but, since they have no end groups, cannot be detected by end-group... 

Kim HC, Nam KH, Jo WH. The effect of a styrene-methyl methacrylate block copolymer on the morphological, rheological and mechanical properties of poly(2-6-dimethyl-l,4-phenylene ether) (PPE) and poly(hydroxyether of bis-phenol A) (phenoxy) blends. Polymer 1993 34 4043-4051. 

Bi and Fetters studied the rheological and mechanical properties of DVB linked star-block copolymers of styrene and dienes [12]. The dynamic viscosities were... 

Ice crystals also have important effects on the rheology and mechanical properties of ice cream. However, because the other components also contribute to these, rheology and mechanical properties are discussed in the context of the whole composite material below. 

The behavior of proteins at interfaces influences the formation of foams and emulsions (32). Stabilization of foams and emulsions depends, to a great extent, on the formation, rheological, and mechanical properties of the interfacial film ( ). Factors which ensure optimum film properties in simple systems may retard film formation or cause destabilization in foams or emulsions (3 ) for example, many rheological properties of films are maximum in the isoelectric pH range of specific proteins, yet most proteins have minimum solubility in this pH range (34). Thus, environmental and processing factors which... 

A great deal of attention on PET/PEN blends has been paid to elucidate the type of kinetics of the transesterification reaction, and, in particular, reversible second-order kinetics has been found in solution [64], On the other hand, the reaction kinetics is strongly affected by terminal hydroxyl groups when the reaction is carried out in a mixing chamber [65], In the same device, studies on the thermal, rheological, and mechanical properties for blends with 25, 50, and 75 wt% of PEN content have also been reported [66], By using a twin-screw extruder, a block copolymer may be obtained via melt extrusion when the PEN content is 20 wt% [67],... 

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