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Quantitative comparisons of the merits of doing experimental studies of three-particle final state nuclear reaction using a continuous or pulsed beam are stated. The true and random coincidence rates with a pulsed beam are derived and checked with an experiment. Reaction 9 Be + p → n + p + 8 Be is chosen for study. Two-dimensional spectra of proton-neutron coincidence events are obtained. The pulsed beam technique is proved to be always more advantageous for multiparticle final state nuclear reaction studies involving neutrons.

The photo-oxidation of PVC has been studied over the temperature range 30–150°C. Initiation with ultraviolet (2537A) radiation has been correlated with the presence of minute amounts of ozone. The contribution of atomic oxygen and singlet oxygen (1Δg) molecules to the initiation mechanism is discussed. The β-chloroketones probably formed in the photo-oxidation of PVC, decomposed according to a Norrish type I reaction without loss of chlorine atoms. The gaseous products of the photo-oxidation of PVC at 30°C were carbon dioxide, carbon monoxide, hydrogen, and methane. Hydrogen chloride was obtained only when PVC was heated at high temperatures. When PVC was photo-oxidized and then heated at high temperature, benzene was obtained in addition to hydrogen chloride. The gaseous products from the photo-oxidations of model compounds, such as 4-chloro-2-butanone and 2,4-dichloropentane, were also compared with those from PVC. Hydrogen chloride was detected only after photo-oxidation at temperatures of 25°C or higher. Therefore, it was concluded that hydrogen chloride is mainly a product of thermal decomposition. Since unsaturation was not observed in photo-oxidized PVC films, the cause of discoloration is unclear. When PVC was modified by stabilizers or additives, the oxidative degradation was further complicated by side reactions with the additives.

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., Gc., was 0.29 and did not vary greatly from pure PVC to commercial PVC. However, the efficiency of scission was lowest (Gs = 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. Gs for PVC with opper thalocyanine was 0.62, with copper salicylate was 1.38, and was 6.20 with ferrocene. Gc values also increased in the same order, from 0.40 to 3.10. The ratio of main-chain fractures to number of crosslinks formed (β/α) increased again in this order from 0.1 for purified PVC to 1.0 for PVC–ferrocene. For purified PVC, β/α increased after 36 hr. of ultraviolet irradiations. In the presence of copper salicylate and ferrocene, ion-radical reactions probably contribute towards the high β/α 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.