Concentration and half - life period of radicals formed in modified PVC by UV-irradiation
On the basis of the ESR analysis, it has been found that the concentration of radicals formed In films prepared from pure PVC under the effect of UV-irradiation is much lower than that in PVC films modified by the addition of 1—10 per cent by weight of VC/VAc- or MM/MA-copoly- mers or MBS- and ABS-terpolymers. A comparison of the half-life periods of radicals formed in samples after an 0.5-or 1 h-irradiation reveals a much higher proportion of long-life polyene radicals in samples after shorter irradiation. This is sn indication that in their case the process of dehydrochlorination is a preponderant one. In the longer irradiated samples, the concentration of short-living peroxide radicals increases. This fact has been observed in particular for samples containing MBS, what can be ascribed to an accelerating effect of this terpolymer in respect to PVC photo-oxidation. From the results of ESR analysis one can conclude that the VC/VAc-copolymer and ABS-terpolymer catalyze the dehydrochlorination reaction of PVC.
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