Blends of polycarbonate with poly(methyl methacrylate). Part I. Preparation of blends and calorimetric studies
Blends of polycarbonate with poly(methyl methacrylate).
Part I. Preparation of blends and calorimetric studies
The effect of the method of preparation of PC-PMMA blends on their mechanical properties has been investigated in the whole range of concentrations. Blends have been obtained in two ways: 1) by mixing together solutions of these two homopolymers followed by precipitation with a non-solvent and 2) by radical polymerization of methyl methacrylate in a solution of PC in methylene chloride followed by precipitation. The test specimens in the form of films have been obtained by dissolving polymer in CH2Cl2 and casting the solution on the glass plate, whereas specimens in the form of sheet were prepared by hot pressing of the polymer. IR spectra of both types of blends did not reveal any specific interactions between the two components. Some phase-separated structure of the as-polymerized film samples can be connected, however, with the nonuniformity in the average blend composition. DSC scans of the same samples showed only one glass-rubber transition, Tg, intermediate of the Tg's of pure homopolymers, indicating that a total phase separation did not occur. The density measurements revealed an increase in the molar volume of the as-polymerized blends in comparison with the additive values. NMR measurements showed the changes in tacticity of PMMA polymerized in the presence of PC and this can be considered as the reason of the changes in Tg's values as well as in the molar volumes with the composition of the blends. The coprecipitated blends exhibit two glass-rubber transition regions in the whole range of composition and the glass temperature assigned to pure PC in all cases remained almost unchanged where as the deviations for pure PMMA being at most equal to 10K. This is in agrement with NMR measurements, which did not reveal any significant changes in PMMA tacticlty in blends coprecipitated with PC. These studies on PC-PMMA blends led to a conclusion that a quite high degree of mixing of these two polymers can be achieved when the polymerization technique isused for the preparation of the polymer blend.
If you are interested in full versions of articles, please contact the editorial team of firstname.lastname@example.org