THERMOANALYTICAL STUDY OF THE METHYL-METHACRYLATE POLYMERIZATION UNDER THERMAL-GRADIENT

Cylindrical samples of thermally polymerized methylmethacrylate (MMA) were investigated and the time dependent temperatures at certain posit ions within the samples were measured during this process. Owing to th e polymerization heat evolved, the maximal observed temperature differ ence within this probe was Delta T = 3.5 degrees C, e.g. the MMA polym erization occurs under a thermal gradient. As a consequence, the maxim al difference at the glass transition temperature of the solid PMMA is Delta T-g = 1.5 degrees C, and for samples prepared at a higher tempe rature gradient (arranged by means of a central ''hot wire''), Delta T -g = 6 degrees C. For this cross sectional inhomogeneity, a difference in the molecular weight distribution for the annealed samples of Delt a M = 3 x 10(4) is proposed.