LOW MOLAR-MASS POLYBUTADIENE MADE CROSS-LINKABLE BY THE INTRODUCTION OF SILANE MOIETIES VIA URETHANE LINKAGE - 2 - CROSS-LINKING STUDY

In the present paper we discuss the crosslinking of polybutadiene bear ing alkoxy silane functions (PBUnSi), where n is the number of silanes per chain (a = 1.2, 2, 2.4). Crosslinking was carried out at differen t temperatures, with and without a catalyst. The best experimental con ditions correspond to 80 degrees C, under moisture with dibutyl tin di laurate as the catalyst in the ratio of [DBTL]/[Si] = 5 x 10(-3). The reaction was followed by the measure of swelling (Q) in toluene and me chanical parameters (storage modulus (E'), E' at rubbery plateau and t an delta). The low rate of modification, essentially at chain extremit ies, leads to the molar mass per crosslinked unit (Mc) being practical ly constant and thus to a weak increase of T-g whatever the n value. O nly a drop of damping efficiency is observed during the crosslinking p rocess. (C) 1997 Elsevier Science Ltd.