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Urethane-foam-backed poly(vinyl chloride) (PVC) degrades through dehydrochlorination, a process that results in the formation of conjugated polyene sequences within the backbone of the polymer. Raman spectroscopy at 633 nm and a combination of fluorescence spectroscopy and microscopy with blue excitation have been used to quantify the temporal degradation of two commercial foam/ vinyl composites. Since the resonance behavior of polyenes depends on their conjugation lengths, the Raman and fluorescence measurements were most sensitive to polyenes with conjugation lengths of ≥20 and ∼10, respectively. Durability tests were performed by weathering samples in the field for 35 months and in ovens at temperatures of 100 and 120°C for ∼500 h. For the field-weathered samples, the integrated fluorescence intensity correlates well with the polyene concentration as determined by Raman measurements, which suggests that for these aging conditions the kinetics controlling the steady-state populations of short- and long-length polyene sequences are similar. The results from the laboratory-weathered samples are consistent with the conclusion that short-conjugation-length polyenes form first and then propagate to longer conjugation lengths as degradation progresses. Most importantly, this work demonstrates that the relatively simpler fluorescence imaging techniques can be extremely useful in determining the comparative weatherability of different foam/vinyl composites.

Pentaglycerine (PG) and tris-hydroxy-aminomethane (Tris) are potential thermal energy storage materials which undergo energetic solid-state phase transformations. The low temperature a-phase structure of PG is body-centered tetragonal and that of Tris is orthorhombic. The high-temperature phase structure of both compounds is face-centered cubic. Polymorphic changes in the structure occur at 89~ for PG and 135~ for Tris. These compounds are dielectrics at low temperature with conductivities on the order of i0 -8 ~-~ cm -~ (at 21~ and I0 -9 ~-~ cm ~ (at 25~ for PG and Tris, respectively. Heating samples from room temperature leads to an initial decrease in a-phase conductivities followed by an increase for both of these compounds as a result of proton hopping. Continuous increases in the conductivity were observed at the transition temperature, with discontinuity evident in the case of PG. The conductivity variations in the a-and ~-phases have been found to be thermally activated. The activation energies are nearly equal suggesting similar conduction mechanisms and charge carriers. From the relaxation time data, an equation has been obtained for the charge carrier self-diffusion coefficient for the ~-phase of PG, just above the transition temperature; D (~) = 0.085e ~7,1~7~T. The conductivity in the ~]-phases are independent of the frequency in the range of i0 to i03 Hz. The temperature and frequency effects on the conductivities, relaxation times, and diffusional parameters of PG and Tris are presented.Molecular "plastic crystals" which undergo solid-state transitions are potential candidates for thermal energy storage applications.