Studies of the Vulcanization and Structure of Polyacrylic Rubber

Abstract

Abstract Several characteristic features of the vulcanization of polyacrylates have been demonstrated. The fact that alcohol is formed and liberated during cure has been demonstrated; this finding might favor a Claisen type condensation. On the other hand, the fact that a copolymer of methyl acrylate and acrylic acid can be plasticized with alcohol and assumes a chain spacing comparable with that of cured polymethyl acrylate, whereas the uncured PMA and unplasticized copolymer are appreciably different in chain spacing, might favor a controlled hydrolysis and hydrogen association as the mechanism. The latter mechanism would be more compelling if the methyl acrylate/acrylic acid copolymer when alcohol plasticized showed other evidences of vulcanization, in situ, such as increased resistance to methylethyl ketone or reduced thermoplasticity in addition to increased rubberiness. Several different x-ray diffraction patterns are shown in Figures 6 to 15. Note the progression in spacing for the inner halo as the number of terminal carbons in the side chain increases. In comparing the pattern of α-carboxypimelic acid, a highly crystalline compound, with the patterns of the esters of the acid, we note the influence of hydrogen binding on the side chain association to produce a regular 3 dimensional structure, while esterification with relatively unreacting alkyl groups decreases cross-bonding between chains so much that the structure assumes a liquid configuration similar to that of the various polyacrylates.