synopsisDegradation of polyurethane samples by UV, combination of W-thermal, and natural weathering were studied by photoacoustic spectroscopy. This study reveals that degradation of polyurethane could be initiated at a relatively low temperature of 40°C and low W dosage. It was also found that the effect of heat is more pronounced than the effect of W. The reaction mechanism of polyurethane degradation is fully in agreement with photoacoustic absorption spectra.

SynopsisImmediately after heating rigid foam polyurethane (PU) at 165"C, it degrades in accordance with the degradation mechanisms suggested by Abu-&id et al. in earlier publications. However, after three days all photoacoustic spectra (PAS) bands indicative of PU degradation almost disappeared, and the samples were found to resist both UV and thermal degradation for a wide range of temperatures and W dosages. Residual catalysts left from PU polymerization were found to be the main cause of its degradation. When these residues were consumed in the process of solid repolymerization, PU becomes immune to heat and UV degradation.

synopsisPoly(viny1 chloride) film shows substantial changes in its photoacoustic absorption spectra (PAS) on either irradiation or heating in the presence of O2 or NP These spectral changes are due to the conjugation structures and carbonyl (group formation), formed during photo-and thermal degradation. In this paper interpretations of the PAS and of the decomposition mechanism of PVC are presented.

SynopsisPVC films were subjected to mechanical degradation at room and elevated temperatures and monitored by photoacoustic spectroscopy. Broken bonds in the main PVC chain result in the-formation of "mechanc-radicals," which in turn yield a zipper reaction and the formation of submicrocracks in the PVC samples. The mechanistic schemes based on the formation of the mechanc-radicals are introduced and are successfully supported by the experimental r e sults.

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