SYNTHESIS AND RHEOLOGICAL STUDY OF SOME MALEIC-ACID AND FUMARIC-ACID STEREOREGULAR POLYESTERS .7. RHEOLOGICAL STUDY OF COPOLYMERIZATION REACTION OF CONFIGURATIONALLY PURE UNSATURATED COPOLYESTERS AND STYRENE

The crosslinking copolymerization of styrene and configurationally pure unsaturated copolyesters, containing phthalic acid and maleic or fumaric acid residues, was carried out in a dynamic shear field at a frequency of 6,28 rad . s-1 and ambient temperature. It was found that a clear distinction can be made between gelation and postgelation crosslinking. The former takes place between the onset at G' almost-equal-to G"(G', G":storage and loss shear moduli) and the practical end point at (DELTA-G'/DELTA-t)max = k0, while the latter represents a first-order process which is characterized by its mte constant, k1, and the corresponding crosslinking half-time. The relationship between k0 and k1 was established. It appears that the reaction of the fumarate residues with styrene is much faster than that of the maleate residues. At the same degree of unsaturation of 50 mol-%, k0 was about seven times higher for the reaction of fumarate copolyester than for the reaction of the maleates.