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Applying the method described in the preceding paper, molecular mechanics is used to calculate in a unified manner, from transferable conformational energy functions, the packing parameters and energy, vibrational dispersion curves, heat capacity, and thermodynamic functions, elastic constants, and refractive indices of polyethylene (PE) and poly(oxymethylene) (POM). PE was chosen as a "standard" to illustrate the method and POM because it occurs in two crystal forms occasioned by the effect of packing forces in distorting the intramolecular torsion angles and because its crystal properties are of interest. Compared to the free ••GGhelix, the helix in the orthorhombic form is under compression and that in the hexagonal form under tension. Good agreement between calculated and experimental structures was found. The packing energy of the orthorhombic form is slightly more favorable (1.5 kJ/mol) but the free energies at room temperature are more comparable (0.7 kJ/mol). The calculated heat capacity of POM over the range 100-300 K is in reasonable agreement with the extrapolated experimental values of Gaur and Wunderlich and significantly higher than those of Illers. The C33 elastic constant of PE is calculated to be 341 GPa and that of (hexagonal) POM is 83 GPa.

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The miscibility and crystallization behavior of binary crystalline blends of poly(butylene terephthalate) [PBT] and polyarylate based on Bisphenol A isophthalate [PAr(I-100)] have been investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). Both polymers were able to crystallize over a wide range of blend composition and temperature. This blend system exhibited a single composition-dependent glass-transition temperature over the entire composition range and two distinctive melting peaks in some compositions. The equilibrium melting point depressions of both PBT and PAr(I-100) were observed, and the Flory-Huggin's interaction parameter of χ 12(PBT) ) -1.3 was obtained. It indicated that these blends were thermodynamically miscible in the melt. The crystallization rate of neat PAr(I-100) was very slow. However, it was much faster when the PBT was added. The crystallization rate of PAr(I-100) was significantly influenced when the PBT crystal was previously formed. It was not only due to the amorphous phase composition shifted to a richer PAr(I-100) content after the crystallization of PBT but also to the constraint of the PBT crystal phase. On the other hand, the crystallization rate of PBT was reduced due to the addition of PAr(I-100).

This study reports the individual and combined effects of ultraviolet light and thermal shock on the physical properties of polymer matrix composites in air and in a "near-vacuum system." The longest exposure time was 180 days. It was found that the weight loss of composites increased with irradiation time. In the graphite/epoxy system, the weight loss in air was 2-3 times that in a "near-vacuum system." Similarly, the weight loss of the glass/epoxy system in air was 3-6 times that in a "near-vacuum system." The weight loss of the glass/epoxy system was always larger than that of the graphite/epoxy system. In all cases, the W irradiation and 1000 times thermal shock did not change the fracture mechanism-it was always brittle fracture in addition to fiber pullout. Surface erosion was observed in the irradiated surfaces by scanning electron microscopy. For both graphitelepoxy a n d glass/epoxy composites, the tensile strength decreased with increasing irradiation time irrespective of the irradiation environment. However, the decrease was not significant. By SEM, cracks could be observed in the up-surface and side-surface of the glass/epoxy system that was irradiated more than 1 month in air and through 1000 times thermal shock. Obviously, UV light cannot deeply penetrate the sample, and only the surface of the sample will be influenced. The UV radiation initiated microcracks, which propagated through the thermal shock.