Tempered glass transition

The aromatic rings contribute to the polycarbonate s high glass transition temperature and stiffness (Table 4.4). The aliphatic groups temper this tendency giving polycarbonate a decent solubility. The two methyl groups also contribute to the stiffness because they take up... 

To a much greater extent than either metals or ceramics, the mechanical properties of polymers show a marked dependence on a nnmber of parameters, inclnding temper-atnre, strain rate, and morphology. In addition, factors snch as molecnlar weight and temperature relative to the glass transition play important roles that are not present in other types of materials. Needless to say, it is impossible to cover, even briefly, all of these effects. We concentrate here on the most important effects that can affect selection of polymers from a mechanical design point of view. 

The energy elastic range and glass transition point are succeeded, as the temper-atiue rises, by the entropy elastic (soft or viscoelastic) range, i.e., the application range for polyolefins. 

Cnossen, A.G. Siebenmorgen. TJ. (2000). The Glass Transition Temperature Concept in Rice Drying and Tempering Effect on Milling Quality. Transactions of the ASAE, Vol. 23, pp. 1661-1667. 

Table 6.10. Castor Oil-Urethane/PS (CO-U/PS) IPN Glass Transition Temper atures " ...

A problem that pervades simulations of complex fluids, particularly at elevated densities and low temperatures (e.g., near the glass transition temperature), is that the system gets trapped in local energy minima from which it is unable to escape. In such cases Configurational Bias moves are often insufficient, and additional tricks are necessary to improve sampling. One class of methods that is particularly helpful and easy to implement is provided by Parallel Tempering techniques. 

Multidimensional Parallel Tempering has been employed successfully to study the phase behavior of electrolytes at low temperatures [44,45]. It has also been used to investigate the behavior of glass-forming disaccharides near the glass transition [46]. 

Incorporation of CNT into polymer matrix, due to the exceptional properties and laige aspect ratio, has been proven to be a promising approach leading to stmctural materials and composites with excellent physical and mechanical properties such as tensile strength, tensile modulus, strain to failure, torsional modulus, compressive strength, glass transition temper-... 

Many ways have been demonstrated for effectively generating surface compressive layers, some of which have been applied commercially. These include thermal tempering, ion exchange at temperatures either above or below the glass transition, surface crystallization, lamination, and glazing. 

The eight methylene units in sebacic acid, plus the numerous methylene units in the triglyceride all contribute to the low glass transition temperature, Tg, of the final product. The ten-second modulus vs. temper-... 

Figure 21 shows the temperature dependence of the dielectric constant for N-pben-ylated polyurea, abbreviated NPUR. IWo relaxation processes were observed first with a small relaxation strength in the temperature range I0(>-12(FC, probably due to processes such as a local motion, and sec in the range 160-17(fC, where the dielectric constant increases to about 12 due to the glass transition. The DC conduction above IfifTC increased drastically. The NPUR has a dielectric constant of 3.4 at room temper-ature. The X-ray diffraction pattern shows a typical amotpbous structure for NPUR. 

We have used a polymer melt, the polydimethylsiloxane, which is well into its liquid phase at room temperature (glass transition temperation T- = - 120 C). The choice of a polymer is convenient it ensures the low volatility of the liquid and allows to vary the viscosity in an enormous range (0.5 - 25.10 P in the present experiments) without affecting the... 

Figure 6.28 Schematic representation of residual stress generation in a thermally tempered glass sheet. Viscous flow is possible over Tg. Thermal gradient builds in. On passing the glass transition and obtaining uniform temperature, stress builds in.

Tempering (substrate) Removal of internal stresses by heating above the Glass transition temperature (glasses) or annealing temperature (metals). 

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