Temperature elasticity

Polymers will be elastic at temperatures that are above the glass-transition temperature and below the liquiflcation temperature. Elasticity is generally improved by the light cross linking of chains. This increases the liquiflcation temperature. It also keeps the material from being permanently deformed when stretched, which is due to chains sliding past one another. Computational techniques can be used to predict the glass-transition and liquiflcation temperatures as described below. 

Nylon-6. Nylon-6—clay nanometer composites using montmorillonite clay intercalated with 12-aminolauric acid have been produced (37,38). When mixed with S-caprolactam and polymerized at 100°C for 30 min, a nylon clay—hybrid (NCH) was produced. Transmission electron microscopy (tern) and x-ray diffraction of the NCH confirm both the intercalation and molecular level of mixing between the two phases. The benefits of such materials over ordinary nylon-6 or nonmolecularly mixed, clay-reinforced nylon-6 include increased heat distortion temperature, elastic modulus, tensile strength, and dynamic elastic modulus throughout the —150 to 250°C temperature range. 

Table 3 Room-temperature elastic constants, density, and the Debye temperature p of a number of Pd-Ni-P and Pd-Cu-P bulk amorphous alloys. The elastic moduli are in units of GPa and the density p is in units of g/cm. ...

Oxynitride glasses are silicate or alumino-silicate glasses in which oxygen atoms in the glass network are partially replaced by nitrogen atoms. As nitrogen increases, glass transition temperature, elastic modulus, viscosity and hardness increase while thermal expansion coefficient decreases. 

Room temperature elastic tensors for a- and [Pg.318]

Trials are carried out and described, which proves the method of elastic-deformation dispersion as a technique in making possible the effective processing of waste from various PVC materials to obtain fine-particle recycled product with wide possibilities of practical use. The elastic-deformation dispersion method, is based on the idea of multiple breakdown, when the material is subjected to the combined action of high pressure and shear deformation at elevated temperatures. Elastic-deformation dispersion of roughly ground materials with particle diameter of 1-3 cms. was carried out in a single-... 

Thermoplastic polyurethane containing 4,4 -diphenylmethane diisocyanate, poly(tetramethylene glycol) and 1,4-butanediol has good mechanical strength, wear resistance and tear resistance and low-temperature elasticity. Aiming to improve the performance of sPS by exploiting these properties, Xu et al. [43]... 

Partial replacement of siloxane units with silphenylene groups also increases polymer crystallinity (5, 6), results in a higher viscosity (7), increases the mechanical properties, and improves thermal stability. On the other hand, incorporation of the rigid silphenylene units into the poly siloxane backbones could decrease the low-temperature elasticity of these polymers (8). 

Limiting properties Poor low-temperature elasticity poor recovery strong, offensive odour until it skins stow skinning and cure rate unsuitable under water-immersed conditions... 

Testing of the temperature dependence of the extension and shrinkage behaviour at low (TMA) or oscillating (DMA) yarn tension glass temperature, elasticity and other parameters for exact differentiation of elastomeric fibres. 

The room temperature elastic moduli, such as the compression or bulk modulus K , Young s modulus E , and shear modulus G of the Ti5Si3 and TiSi2 compounds are presented in table II. The bulk and shear moduli are relatively low in comparison to the Young s moduli. This implies that Poisson s ratio is about V = 0,24 or less indicating that the elastic transverse... 

TABLE 11. Room Temperature Elastic Moduli and Mechanical Properties... 

Epoxy cured with low temperature, elastic and poor alkali resistance... 

Solid-state low-temperature elastic properties have been studied experimentally at the NBS Cryogenics Division for four years Most studies were... 

Only brittle plastics go through all of the steps along the temperature-elasticity curve. Some states of plastics are determined by the crystallites, others by the amorphous regions. The properties of these two phases are additive. 

The first evidence of LRO firom a one-component self-assembled, end-functionalized polymer was the assembly of a PIB bearing a single terminal DAT motif [59]. This material exhibited a series of SAXS diffiraction peaks with relative positions at lW2 V3, corresponding to a body-centered cubic (bcc) lattice with a periodicity of 6.5 nm. The structure dissolved upon heating to 90 °C, and it reversibly re-appeared when cooled to 20 °C. The temperature dependence of the bcc structure was later assessed [58] and found to be related to the materials rheological properties. The low-temperature elastic properties are attributed to... 

Elastic modulus of both particulate and platelet composites was determined from 25 to 1000°C as a function of alumina content by the impulse excitation of vibration method, ASTM C 1259 [26] using the flexure specimen configuration. One flexure specimen was used at each of alumina contents for a given composite. A total of five specimens were additionally used at each alumina content to evaluate ambient-temperature elastic modulus of the two composites. 

In the case of aU of the developed hybrid silarylene-siloxane and carboranylenesiloxane polymers, an evaluation of the nature of different phases containing aromatic or carborane groups will be illuminating to understand what contribution does each distinct phase has on the elasticity and other material properties of the generated networks. Other in-depth mechanical studies are also in order to better evaluate the high temperature elasticity of the materials. 

The room-temperature elastic constants of single crystals with the stoichiometry B5 fiC synthesized by the optical floating zone method have been measured using a resonant ultrasound spectroscopy technique [531]. The single crystal elastic constants indicate the strong anisotropy of the structure Cn = 542.81, Cg3 = 534.54, Ci3 = 63.51, C12 = 130.59, and 44= 164.79GPa, respectively. 

R represents an organic side group. The polymers have found some use in hose, gaskets, and seals in aviation-fuel-handling equipment. They have better solvent resistance and low-temperature elasticity than sUoxane-carborane polymers, and are less costly. 

Fig. 8.90. A graphical summary of selected room temperature elastic stiffness constants of the rare earth metals.

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