SynopsisThe relations between the properties and the blend ratios of natural rubber ( N R ) and styrene-bntadiene rubber (SBIt) blends were studied in comparison with four blending methods. The relations between the properties of unvulcanized and vulcanized blends and the blend ratios of blends prepared by means of solution blending, latex blending, roll blending, and Banbury mixer blending were studied. I n practice, such rubber blending methods as roll blending are more effective for obtaining uniform blends than Banbriry mixer blending the latter. In roll blending, it is more effective to blend NR and SBIt by way of a master-batch in which the ingredients are compounded beforehand than to blend raw rubber. In solution and latex blending, very uniform blends are easily obtained. It was found, however, that the properties of NR/SBR blends prepared carefully showed a direct relation to their blend ratios, regardless of blending method rised.
SynopsisThe properties of butadiene-styrene copolymers and of polybutadiene-polystyrene blends were compared. Polybutadiene, polystyrene, and four copolymers having styrene contents of 20,40,60, and 80% were prepared. The copolymers were compared with blends having various styrene contents and prepared by means of latex blending and roll blending. Vulcanizates were prepared by three different curing methods, i.e., sulfur cure, peroxide cure, and radiation cure. The results of the benzene extraction of three vulcanizates showed that the polystyrene blended was not cured by any of the curing methods used. The properties of the vulcanizates of the copolymers were markedly different from those of the blends, i.e., in the case of the blends the properties showed a linear relationship with their blending ratio, while in the copolymers the properties showed a curvilinear relationship which had an inflection point at a styrene content of about 60%. From this phenomenon of the copolymers, it was proposed that the second-order transition point of styrene is the cause of the properties showing this peculiar point. From the results, it was found that the behavior of styrene in copolymers is essentially different from that in blends. INTRODUCTIONRecently the consumption of butadiene-styrene rubber has increased rapidly, and in the rubber industry it has become an indispensable rubber.It is well known that in butadiene-styrene rubber the properties of the copolymer are affected by the bonded styrene content. As the quantity of bonded styrene is increased, the copolymer becomes less rubbery and more leatherlike and resinlike. Many studies concerning the processing method and the properties of the copolymers have been reported for copolymers having a commercially practical bonded styrene content, ie., SBR and high-styrene resin. However, copolymers containing styrene in amounts outside of the current practical range have not been studied extensively.There are a few studies on the relationship between the bonded styrene content and the properties of the A study on the methods of blending natural rubber with butadienestyrene rubber has been r e p~r t e d .~In order to clarify the difference between the properties of copolymers and of blends of the butadiene and styrene, copolymers having various styrene contents and physically blended mixtures of polybutadiene (rubber) with polystyrene (resin) having styrene contents corresponding to those of the copolymers were studied.The butadiene-styrene copolymers used were prepared on a pilot-plant scale for this study and had molecular weights of about 200,000. The blends were prepared by means of latex blending and roll blending. To study the differences in properties of the vulcanizates, both the copolymers and the blends were cured with sulfur, with peroxide, or by radiation.Results of benzene extractions of these vulcaniaates showed that the polystyrene blended was not cured by any of the curing systems.Results on the vulcanizates indicate that the properties of the blends, showed a lin...
The properties of butadiene–acrylonitrile copolymers were compared with those of polybutadiene–polyacrylonitrile blends. Also, the properties of copolymers having an acrylonitrile unit content of about 30% were compared with those of polymer blends having the same acrylonitrile unit content, i.e., NBR–NBR, polybutadiene–NBR, and polyacrylonitrile–NBR, having different acrylonitrile unit contents. These blends were prepared by roll blending and the vulcanizates were prepared by sulfur cure. The properties of the copolymers were markedly different from those of the blends, that is, in the blends the properties showed a linear relationship with their blending ratios, while in the copolymers the properties showed a curvilinear relationship. In the cases of the polymer blends having a constant acrylonitrile unit content, those blends which were prepared by blending two polymers having similar acrylonitrile unit contents showed better properties than the ones having very different acrylonitrile unit contents.
In another paper the radical polymerization of styrene in the presence of various chlorosilanes was investigated, and polystyrenes having chlorosilyl groups as endgroups were obtained. In the present work attempts were made to obtain polysiloxane styrene graft and block copolymers from chlorosilyl polystyrenes. Block copolymers were obtained with dichlorosilane and graft copolymers with tri‐ and tetrachlorosilanes. In the latter case the insoluble fractions increased, if a suitable stopper, such as butanol or trimethylchlorosilane [(CH3)3SiCl], was not used in the condensation reaction. Methyldichlorosilane was used for the preparation of the graft copolymer, because the SiH bond was more effective than the SiCl bond for the chain transfer reaction.
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