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.