Ultraviolet Irradiation of Poly(viny1 Chlorides). Radiation Parameters* Part I. Effect of Substituents on T<WRI-PING SHEN KWEI, Bell Telephone Laboratories, Incorporated) Murray Hill, New Jersey Or971
Synopsis
The crosslinking and main-chain scission of PVC and its derivatives by ultraviolet radiation at 2537 A. were investigated. Examination of the relationship between gel fraction and radiation dose showed that the number of crosslinks formed in pure PVC per 100 e.v., G., was 0.29 and did not vary greatly from pure PVC to commercial PVC.
However, the efficiency of scission was lowest (G. = 0.06) for purified PVC, increased to 0.23-0.26 for commercial PVC, and increased further when chelates were substituted on PVC at C1 atoms. G. for PVC with copper thalocyanine was 0.62, with copper salicylate was 1.38, and was 6.20 with ferrocene. Go values also increased in the same order, from 0.40 to 3.10. The ratio of main-chain fractures to number of crosslinks formed (@/a) increased again in this order from 0.1 for purified PVC to 1.0 for PVC-ferrocene. For purified PVC, @/a increased after 36 hr. of ultraviolet irradiations. In the presence of copper salicylate and ferrocene, ion-radical reactions probably contribute towards the high @/a ratio. Ability of the aromatic substituents to enter chain-transfer reactions with polymeric radicals followed by coupling reactions may contribute partly towards crosslinking in PVC.