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Two types of ethylene‐vinylacetate copolymers, containing 16% and 9% of vinylacetate, respectively, were crosslinked with dicumyl peroxide in a Brabender plastograf. The time of the torque maximum was proportional to the degree of crosslinking. The degree of crosslinking was determined by extraction and depended on the concentration of the crosslinking agent and of vinylacetate in the copolymer, and on the crosslinking temperature and time. It was found by DSC and by solid‐state CP‐MAS 13C NMR that with the progress of crosslinking the crystalline phase of the copolymers changed to the amorphous phase. Crosslinking took place mostly on the acetate groups.

With the addition of 20 phr of BR granulate grafted with ethyl acrylate by the redox or gamma irradiation method to polyacrylic rubber compound, the properties of the rubber worsened, but remained within the range of properties characteristic for these types of rubber. The stability of rubber against swelling in hot mineral oil was satisfactory even when 30 phr of grafted granulate was added to polyacrylic rubber. It can be concluded that polybutadiene granulate when grafted with ethyl acrylate, gains some properties characteristic for polyacrylic rubber due to the introduction of polar groups into the polymeric chain of the BR rubber. This might also be the reason why polybutadiene granulate grafted with ethyl acrylate could be in no case added to polybutadiene rubber regardless of the grafting method. No attempt was made so far to evaluate the economical aspects of grafting waste rubber and the real possibility of using grafted granulate on a large scale.

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Controlled two step block copolymerization of styrene, methyl methacrylate and ethyl acrylate with aliphatic and aromatic disulphides under UV irradiation took place in bulk and in THF solution. In the first step of the polymerization, the most reactive system was ethyl acrylate with aromatic disulphides.The molecular weights and yields of polymerizations increased with reaction time. The macromolecules were terminated by primary . SR radicals and by combination of two macroradicals which was observed by NMR spectroscopy. An insignificant portion of uninitiated photopolymerization was detected only for MMA. In the second step of polymerization, the purified macroinitiators from the first step reacted with additional monomers to form block copolymers with a small quantity of unreacted macroinitiator. The molecular weights of copolymers increased, the bonding segments between the blocks being detected by 'H NMR.The overall reaction is an insertion of monomers between two thiyl groups.

The NMR (nuclear magnetic resonance) and GPC (gel permeation chromatography) studies of the polymerization of maleic anhydride and 1,2-propylene glycol are reported. Assignment of individual groups was made and their concentration dependence on reaction time was established. The first step of the reaction is the formation of monoesters, which, immediately after the temperature increased, reacted to diesters. The reactivity ratio between the primary and the secondary hydroxyl group of 1,2-propylene glycol was 2.6: 1. The concentration of water formed was followed as a function of reaction time by the Karl-Fischer method. AND SCIENCE, MID-SEPTEMBER 7995, Yo/. 35, NO. 17 POLYMER ENGINEERING

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