Effect of large amplitude oscillatory shear (LAOS) on the dielectric response of 1,4-cis-polyisoprene

The dielectric response of 1,4-cis-polyisoprene under applied mechanical oscillatory shear with various shear amplitudes was investigated. For this purpose, a special setup was constructed which enables to measure dielectric spectra under the influence of large amplitude oscillatory shear (LAOS); the setup is explained in detail. A strong influence of the shear amplitude on the dielectric relaxation strength was observed if the dielectric normal mode was mechanically affected. With increasing amplitude the relaxation strength decreased while the mean relaxation time, the width and asymmetry basically remained unchanged. We interpret this process as an orientational phenomenon of the end-to-end-vectors which results in a decreasing fluctuation amplitude of the polarization fluctuations.     

Stabilization of Polyisoprene Rubber by 3-Mercapto-1,2,4-Triazine-5-One Derivatives

Abstract

In this work, attention focusses on mercaptotriazinone derivatives, which do not paint polymers and are effective stabilizers for thermooxidative degradation of carbon-chain polymers, in particular, of an isoprene rubber.     

异戊二烯橡胶的乳化与乳液稳定性研究

通过反相乳化和脱除溶剂制备了异戊二烯(PIP)橡胶乳液,研究了乳化剂、油水比、乳化剪切速度和胶体SiO2对异戊橡胶乳化液稳定性的影响。结果表明:油酸钾与Span80复配、油水相重量比为1∶1时,经高速剪切均化后得到相对稳定的PIP乳液。而胶体二氧化硅在PIP乳胶粒表面达到吸附饱和,可进一步提高PIP乳液的稳定性。     

The equilibrium melting temperature of cis-polyisoprene

The equilibrium melting temperature T°_m of cis-polyisoprene (Hevea natural rubber) has been determined to be 35.5°C at atmospheric pressure. The optical ‘turbidimetric’ technique developed to obtain the melting data, discussed in this paper, utilized unpolarized light and was free of complications (presumably involving melt strain) encountered with polarized light techniques, but was found to be consistent with that and other techniques. The effect of variables such as heating rate and crystallization time were considered. Two independent methods of extrapolation of the T_m data to evaluate T°_m produced values in the range T°_m = 35.5° ± 0.3°C. The fold surface free energy σ_e was also estimated, by two independent methods, to be 0.024 J m⁻².     

光刻胶用环化聚异戊二烯的研制

研究了顺１，４聚异戊二烯在二甲苯溶剂中在酸性复合催化剂ＳｎＣｌ４／ＰＴＳＡ存在下的环化反应。发现复合催化剂可在较低的温度下引发聚异戊二烯的环化反应，且可抑制聚合物的降解反应，找到了复合催化剂的最佳组成。制得了适用于光刻胶制造的环化聚异戊二烯。