The effect of sorbed penetrants on the aging of previously dilated glassy polymer powders. Part III: The effect of exposure to lower alcohols on enthalpy relaxations in poly(methylmethacrylate)

• Published in: Journal of applied polymer science 1987-11, Vol.34 (7), p.2493-2505
• Main Authors: Stewart, M. E., Sorrells, D. L., McCoy, N. R., Koros, W. J., Hopfenberg, H. B.
• Format: Article
• Language: English
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.1987.070340713

Enthalpy relaxations in glassy poly(methyl‐methacrylate) have been studied through the endothermic, sub‐Tg, aging peak observed in differential scanning calorimetry (DSC) thermograms. Powder samples were swollen by exposure to high activity methanol vapor and then aged in vacuum and in the presence of low activities of methanol, ethanol, and n‐propanol at 308 K. The position and size of the DSC aging peak, which developed during aging, were monitored as a function of aging time. The aging peaks which developed for the alcohol‐aged samples were smaller than those observed for similar samples aged in vacuum. These results suggest that the presence of dissolved penetrant in the samples retarded or arrested the relaxations which were observed in otherwise identical experiments performed in vacuo. Contacting the powder samples with 0.05 activity n‐propanol or 0.10 activity ethanol during aging also appeared to arrest the shift in the temperature of the peak with aging time, whereas aging in the presence of 0.10 activity methanol or 0.05 activity ethanol appeared to have no effect on the temperature of the aging peak. These results are qualitatively consistent with a complementary study of the effect of the presence of lower alcohols on the time dependence of sorption capacity.