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.
N-(2,4,6-Tribromophenyl)maleimide (TBPMI) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in toluene solution using 2,2'-azoisobutyronitrile as free-radical initiation. The copolymerization reactivity ratios were found to be for the system TBPMI/MA r l = 0,095 i. 0,045 (TBPMI) and r2 = 2,17 5 0,142 (MA) and for the system TBPMVMMA rl = 0,037 -+ 0,042 (TBPMI) and r2 = 4,32 f 0,230 (MMA); Q and e values were also calculated. The initial rate of copolymerization, R,, for TBPMI/MA sharply decreases as the content of TBPMI in the monomer mixture increases but the composition of the feed does not have a strong influence on R, for the TBPMI/MMA copolymerization system. The course of copolymerization to high conversion is characterized by an increase of conversion up to a mole fraction of TBPMI of 0,7 in the monomer mixture, when MA was used as the comonomer. An opposite behaviour was found with MMA. Its copolymers show a considerable increase of thermal stability as well as of the glass transition temperatures with increasing TBPMI content.
By the redox method and by gamma irradiation, it was possible to graft ethyl acrylate on to granulate of waste rubber. The quantity of grafted monomer was larger when gamma irradiation was used. When combining ethyl acrylate with 5-methylene-2-norbornene in the redox system with the intention to introduce more double bonds in the grafted granulate, it was found that norbornene does not participate in the reaction and that it even prevents the grafting of ethyl acrylate. This is just a part of extensive experimental work which was done with the intention to chemically modify the rubber granulate for the purpose of enlarging the quantity of waste rubber to be possibly reused in the rubber industry.
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