CRYSTALLIZATION BEHAVIOR OF NATURAL RUBBER, PART3 EFFECT OF SATURATED FATTY ACID ON CRYSTALLIZATION OF CIS-1, 4-POLYISOPRENE

Abstract

Crystallization behavior of synthetic cis-1, 4 polyisoprene (IR), mixed with 0.4×10^-2mol/kg_??_4.8×10^-2mol/kg saturated fatty acid, was investigated by dilatometry at -25 and -15°C. The crystallization of IR was abruptly promoted by the addition of saturated fatty acids higher than 1.0×10^-2mol/kg, such as stearic acid, palmitic acid and myristic acid, respectively, because of the formation of crystalline domain of the fatty acids. But, capric acid did not stimulate the crystallization of IR due to melting at above -25°C and soluble into IR. These demonstarate that the lowest concentration of fatty acids necessary for the acceleration of the crystallization rate of IR was 1.0×10^-2mol/kg, when fatty acid formed crystalline domain dispersed in IR matrix. The crystallization of IR was influenced by not only equilibrium crystal structure, but also dynamic deposition of stearic acid from melt, which was confirmed by precooling of the rubber at 0, 10 and 30°C before crystallization at -25°C.