Synopsiscis-1,PPolybutadiene and trun-s-l,4polybutadiene were mixed at the ratio in weight of 100/0, 75/25, 50/50, 25/75 and 0/100, and various problems related to the mixing were studied. The mixing waa carried out by the three methods, i.e., (I) by rolling, ( 2 ) by filler batch polymer, and ( 3 ) by coprecipitation of the solution. For the mixed compound and vulcanized rubber, such characteristics aa the viscosity of the solution, the Mooney viscosity, x-ray diffraction, infrared spectra phase separation of the solution, tensile strength, and the swelling ratio in benzene were observed. No marked difference in the state of mixing waa noted, regardless of the method of mixing. However, the mixing of filler batch polymer waa accomplished more easily than by the rolling method.A 50/50 blend rubber waa microheterogeneous and contained particles about 0.5 p in length, but these did not affect the crystallization, as judged from the observation of the state of dispersion, by means of electron microscopy, x-ray diffraction, and infrared analysis. This waa revealed by comparing infrared spectra of extracts obtained from the unvulcanized portion after various vulcanization times. The Cis4 vulcanizate did not show any crystalline pattern even at 550% elongation.The lruns-4 polymer, vulcanized a t a much slower rate than C i s 4
SynopsisThe reactions of rubber with aldehydes have previously been studied in latex or in solutions and the reaction products formed by cyclization, condensation, or addition, have been reported. In the present study, solid-state reactions of rubber with aldehydes were carried out. It was found that crosslinked rubbers may be obtained by press curing in the presence of aldehydes with acidic catalysts. Polychloroprene and Hypalon especially undergo these reactions without a catalyst or with a small amount of catalyst. In the experiments using various aldehydes, some improvements in the properties of the crosslinked rubber were observed when aldehydes such as paraformaldehyde or a-polyoxymethylene were used. Some Lewis acids such as SnClz.2HzO were found to be more effective catalysts than the above, and it was found that organic acids such as ptoluenesulfonic acid could also be used.The physical properties of the crosslinked rubber are similar to these of sulfur-cured rubbers.The curing seemed to be an ionic reaction.
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