Density glass properties

Shock Luminescence. Some transparent materials give off copious amounts of light when shocked to a high pressure, and thus they can serve as shock arrival-time indicators. A technique used by McQueen and Fritz (1982) to measure arrival times of release waves is based on the reduction of shock-induced luminescence as the shock pressure is relieved. Bromoform, fused quartz, and a high-density glass have been used for their shock luminescence properties. 

Results for the density, glass transition temperature, thermal expansion, rigidity, and yield strength are plotted according to Eq. (8.1) in Fig. 8.1. These properties remain proportional to each other. 

Thus, the peculiarities of the epoxy glass properties may be due to some specific features of the free volume. For instance, it is possible to explain qualitatively all the unusual properties of epoxy glasses in terms of the size distribution of density fluctuation which may depend on cure conditions 15-20). At present, X-ray methods allow to directly measure the spatial distribution of density fluctuations in polymeric glasses 84). However, it is still unknown how this distribution correlates with properties. 

The method of additive properties has been applied to density, glass transition temperature, and many other polymer properties by Van Krevelen (2 ). The basic idea is that the properties of each chemical group in the polymer are nearly independent of the other groups. Because of this., each group can be assigned a contribution to the glass transition temperature, for example, and the Tg of a polymer is the sum of the contributions of all the groups. 

In this paper we address the area of the structure-property relations of epoxy matrices, with specific emphasis on amine-cured epoxides. In attempts to correlate the structure-property relations of amine-cured epoxides, there have been a number of studies on the mechanical properties of these glasses as a function of epoxide amine ratios and the chemical structure of the constituent epoxide and amine monomers.(1-15) Generally, there is no direct correlation between the chemistry of the epoxide and amine monomers and the mechanical properties of epoxies with the exception that as the distance between crosslinks becomes shorter, these glasses become more brittle.(1,10,15) Also, for a specific amine-cured epoxide system, the Tg is always highest for the fully reacted, highest crosslink density glass.(3,6,9,12,... 

Material properties can be further classified into fundamental properties and derived properties. Fundamental properties are a direct consequence of the molecular structure, such as van der Waals volume, cohesive energy, and heat capacity. Derived properties are not readily identified with a certain aspect of molecular structure. Glass transition temperature, density, solubility, and bulk modulus would be considered derived properties. The way in which fundamental properties are obtained from a simulation is often readily apparent. The way in which derived properties are computed is often an empirically determined combination of fundamental properties. Such empirical methods can give more erratic results, reliable for one class of compounds but not for another. 

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