The Effect Of Crystalline Of Trans-1,4-Polyisoprene On The Properties Of SBR/TPI Blends

Trans-1,4-polyisoprene(TPI) can significantly improve the dynamic performance of blend vulcanizates when blended with general rubbers.This may be related to its unique crystalline and the resulting chain regularity. In this issue, amorphous styrene-butadiene rubber (SBR) was chosen to blend with TPI. The crystallization of TPI was characterized by a variety of testing methods. And the physical and dynamic properties of SBR/TPI blends vulcanized by different curing systems were studied from the perspective of crystalline of TPI.The test results of crystalline of TPI showed that, there wereαandβcrystal melting peaks on its differential scanning calorimeter (DSC) curves. With increasing the heating rate, the melting point ofβcrystal increased gradually,and the melting peak ofαcrystal gradually disappeared after the elimination of thermal history.Freezing had little effect on the crystallinity of TPI.Polarizing microscopy (POM) analysis showed that different crystal morphology of TPI were obtained under different conditions.Fourier transform infrared spectroscopy (FTIR) results showed that the Mooney viscosity did not affect the absorption frequency of TPI. Compared with the cast film, new acromia emerged on the infrared curve of hot pressing film,and the absorption peaks were much sharper at 602cm-1 and 474cm-1. The crystallinity of TPI cooling at 45℃was higher than that at 0℃.X-ray diffraction (XRD) results showed that, TPI had the obvious characteristics of tensile-induced crystallization.The crystallization diffraction peak intensity of SBR/TPI blend vulcanizates were as follows: prestretch specimen> tensile fracture sample > original sample;The crystalline diffraction peak intensity of carbon black filled SBR/TPI blend vulcanizates were much lower than the unfilled samples. The effect of the crystallization of TPI on unfilled SBR/TPI blended vulcanizates cured by CV system was studied.The results showed that the frozen crystals of TPI had little effect on the tensile properties of SBR/TPI blend vulcanizates.While the stretch-induced crystallization increased their tensile strength and modulus at 100% and reduced their elongation at break.The tensile strength tested at low stretching rate was greater than that at high tensile rate.The compression strength and compression set increased with increasing TPI content. Along with TPI content increasing, Tg moved towards low temperature, and the tanδpeak decreased.The fatigue life was longest when 20 or 30phr TPI were added to SBR/TPI blend vulcanizates.Stretch-induced crystallization of TPI produced during the fatigue test.As TPI content increased, the fatigue section of SBR/TPI blend vulcanizates became rough gradually.The effect of the crystalline of TPI on the performance of unfilled SBR/TPI blend vulcanizates cured with different curing system was studied.The results showed that, the crystallization melting enthalpy, tensile strength and compression strength were as follows: DCP system> EV system> CV system. And the tanδpeak of samples were as follows: CV system> EV system>DCP system.At last, effects of the crystalline of TPI on carbon black filled SBR/TPI blend vulcanizates cured with CV system was investigated. The results showed that the tensile strength of SBR/TPI blend vulcanizates filled with carbon black was greater than that of unfilled samples. The elongation at break of unfilled samples first decreased and then increased. While the specimens filled with carbon black showed a overall downward trend.The modulus at 100% of both unfilled and filled samples increased with increasing TPI content. Compared with the stretching rate of 500mm/min, the growth rate of the tensile strength of carbon black filled samples tested at 50mm/min was less than the unfilled specimens. SEM images showed that, the tensile fracture of carbon black filled SBR/TPI blend vulcanizates was more rough than the unfilled samples. As the TPI content increased, the cross section structure of the former became more complex.