REINFORCEMENT OF LIQUID RUBBER BY FILLERS .1. REINFORCEMENT OF POLYUREAURETHANE ELASTOMERS FROM POLY-(OXYTETRAMETHYLENE) GLYCOL BY SILICA

The silica reinforcement of polyureaurethane elastomers from poly (oxytetramethylene) glycol (PTMG), tolylene diisocyanate, and 3,3'-dichloro-4,4'-diaminodiphenylmethane was investigated. Added silica had a much more effect on the tear energy of the elastomers, Г, than on other mechanical properties; Г increased 2~7 times by loading 20~40 phr of silica, while the tensile strength at break TB rather decreased and the elongation at break αB somewhat increased. In addition, it was found that Г was greatly affected by lp/d, the ratio of chain length between adjacent physical crosslinks to diameter of a silica particle, and that lp/d was required to be larger than 3 in order to get a marked inprovement of Г by added silica. On the other hand, Г, ГB, and αB had much less values at 60 phr loading, where retardation of chain extention reaction by added silica is probably prominent. 10% modulus M10 was compared with the the thoretical M10 predicted from the Smallwood equation. The former was smaller than the latter, indicating that the amorphous part of hard segments consisting of substituted urea and urethane groups was partly disturbed. The crystalline part, however, was found not to be disordered according to results of the DSC measurement that the heat of fusion for the cryBtalHne part from 180~210°C remained unchanged within experimental error. Results in creep and swelling tests showed that the bond between silica and PTMG was probably weak. © 1979, The Chemical Society of Japan. All rights reserved.