Abstract: | Mixtures of poly(methyl methacrylate) (PMMA) and plasticizer were made by γ-irradiation of mixtures of methyl methacrylate with diethyl phthalate or with dioctyl phthalate. The glass transition temperature Tg was determined by differential scanning calorimetry. Plots of Tg versus volume fraction of PMMA were found to conform to the simple free volume theory of Kelley and Bueche, using physical property values either reported in the literature or else calculated by Bondi's procedures. |