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It has recently been reported' that the gamma-ray irradiation of several monomer-polymer combinations produces graft copolymers. This paper is concerned with the mechanism of the grafting process and application of four different types of copolymers. The solution property behavior of various graft copolymers will be described elsewhere.2 EXPERIMENTAL PROCEDUREAll experiments were performed with polymer h s having limited swelling by the monomer employed. The technique generally involved suspension of the polymer film in a large excess of monomer enclosed within a 1 X 12 inch Pyrex ampule. The ampules were sealed under nitrogen and placed in cobalt-60 gamma sources of varying intensities. Dose rates of 200,000 rep per hour were employed for routine operations and, for kinetic measurements, dose rates ranging from 20,000 to 300,000 rep per hour were used. (The dose rates were measured using a high level ionization chamber.) All irradiations were performed at room temperature. Initially, distilled monomer was employed, but it was later found that commercial, undistilled monomer containing inhibitor could be employed, The inhibitor caused a short induction period which was followed by a rate of grafting identical to that obtained with distilled monomer. In grafting experiments with acrylonitrile, saturated aqueous solutions were found to be more advantageous than bulk acrylonitrile, because of the rapid homopolymerization rate of the latter. Grafting exeriments with vinylcarbazole were performed with 20 weight per cent solutions of the monomer in toluene.

The chemical reactivity of vinyl and diene polymers manifested during aging and degradation is similar to the reactivity manifested during polymerization; namely, the activated intermediates are radicals and the reaction proceeds by a chain mechanism. A discussion of the possible types of aggregative and disaggregative processes involved in aging is presented. On the basis that polymerization and degradation occur by means of the same radical mechanism, experimental evidence is given to indicate that under certain conditions both reactions may occur simultaneously. Viscosity changes of solutions of mono‐ and polystyrene and methyl methacrylate were studied under varying conditions of heat, oxygen, catalysts, light, and photosensitizers. An analysis of the concurrent aggregative and disaggregative reactions involved in aging may be obtained by isolating one reaction from the other, either by various physical methods, such as intermittent and continuous stress relaxation, or by such classical methods as sol‐gel determinations and aging in solution. A comparative study of the rate of oxygen absorption of a large number of polymer types was undertaken to evaluate the factors affecting oxidation. Evidence is presented to show that these factors may be specified by the following: (1) chemical structure of the polymeric material, (2) presence of antioxidants, and (3) compounding and vulcanization. The oxidizability of polymeric materials was also studied in a circulating oxygen absorption apparatus in order to determine the effect of evolved, gaseous oxidation products. A preliminary study of the effect of light on the aging of butyl and GR‐S rubber as measured by oxygen absorption and stress relaxation is presented.