Polycarbonate-poly(methyl methacrylate) blends. Part II. Mechanical properties
Polycarbonate-poly(methyl methacrylate) blends.
Part II. Mechanical properties
The dynamic mechanical and tensile properties of polycarbonate (PC) — poly(methyl methacrylate) (PMMA) systems prepared in two ways have been examined. The preparation of these blends has been described in the first part of the paper. The loss modulus E", storage modulus E' and tan δ revealed one glass-rubber transition region for was polymerized samples, i.e. when methyl methacrylate (MMA) was polymerized in the presence of PC. This testifies to a quite good compatibility of the components in such PC-PMMA blends. The coprecipitated blends, obtained by simultaneous precipitation of the pure homopolymers from mixed dilute solutions, displayed two transitions in the whole range of compositions at temperatures intermediate between the Tg's of PC and PMMA. The above data have been supported by DSC results for the same samples. Extraction experiments showed that PMMA was not removed completely from as-polymerized blends while is was almost completely extracted from mechanical blends. With the increasing content of PMMA in the blend the tensile properties of PC were improved, this effect being much more pronounced in the case of as-polymerized PC-PMMA systems. From all the electron micrographs of carbon replica of as-polymerized PC-PMMA film surfaces it has been shown that both polymers are cpmpatible on the microscopic level. On the macroscopic level, however, the polymers do not form one homogeneous phase. The results presented suggest that the extent and type of molecular mixing depends to some degree on the method of the preparation of PC-PMMA blends.
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