The photothermal dehydrochlorination of PVC has been investigated by the new spectroscopic methods absorption derivative spectroscopy and excitation-emission fluorescence matrix spectroscopy. The UV irradiation accelerates a rapid evolution of HC1 from thermally treated PVC samples; the evolution was measured by sensitive conductometric methods. It has been found that the quantum yield of HC1 evolution increases with increasing temperature. It has been suggested that in the initiation step carbonyl and/or hydroperoxide groups play a more important role than the residual double bond present and the double bond formed during photothermal dehydrochlorination of PVC. A mechanism involving electronic-to-vibrational energy transfer has been proposed in order to explain accelerated photothermal dehydrochlorination of PVC.

Poly(viny1 chloride) (PVC) and its blends with polybutadieneacrylonitrile (NBR) (containing 2 1.7 weight-percent acrylonitrile (AN), a heterogeneous two-phase system; and containing 41.6 weight-percent of AN, a homogeneous one-phase system) and with polyethylene-vinyl acetate (EVA) (containing 45 weightpercent of vinyl acetate (VA), a heterogenous two-phase system; and containing 65 weight-percent VA, a homogeneous one-phase system) were W-irradiated (at 3500 A W-light (solar spectrum). After W irradiation the kinetics measurements were made of the formation of hydroperoxy (OOH) and carbonyl (CO) groups and the changes of mechanical properties: tensile strength, elongation to break, and impact energy. As a result of the photooxidative degradation of PVC blends, decreases of mechanical properties were observed. The effects are more severe in PVC/NBR blends, which contain unsaturated bonds (polybutadiene segments) than in the case of PVCEVA. The phase structure plays an evident role on the W degradation only of PVC/NBR blends. The photostability of PVC blends can be slightly improved by introducing Tinuvin P or Ni-chelates photostabilizers. PVCIEVA BlendsAddition of 10 parts by weight of EVA-45 (containing 45 weight percent of vinyl acetate) gives a heterogenous two-phase system. EVA domains (weakly polar) are dispersed in the PVC matrix (polar). Addition of EVA-45 component improves impact strength, aging resistance, and weathering performance for outdoor applications (1, 3, 4).Addition of 10 parts by weight of EVA-65 (containing 6.5 weight percent of vinyl acetate) gives a homogeneous one-phase structure, and has a remarkable plasticizing effect on PVC. This is particularly useful in flexible profiles or calendered flexible films,

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