Electron microscopy and microanalysis of polymers and polymer blends : artifacts and applications
Abstract: Electron microscopy and microanalysis is used to examine the degradation of unstainable polymers and polymer blends in order to gain an understanding and arrive at methods for characterizing microstructures. Several methods have been used in order to obtain complementary ways of establishing artifacts arising from specimen preparation effects, the internal energy of the components, and degradation under the electron beam together with low or zero contrast between phases in a blend. It is shown that microstructural characterization of polymer requires the use of complementary methods, beside examination in the electron microscope, using e.g. microanalysis, SEM, and having a good physical understanding of degradation characteristics, microtome cutting properties, etc. Methods for following the degradation of polymers, such as changes in mass thickness and loss of particular elements, are developed. The exposure rate dependency of PVC and a POM/SAN blends is analysed and it is found that lifetime increases with exposure rate. The degradation of PVC is extensively examined and it is found that PVC loses nearly all its chlorine and half Of its mass thickness while maintaining constant density. The loss of chlorine is shown to follow a two term exponential. equation due to two types of chlorine-containing structures of which one is developed during degradation. A computer program of nonlinear regression analysis is developed to fit equations to measured data. Other chlorine-containing polymers are also analysed for chlorine and mass thickness loss. Blends between PVC and some other polymers are analyzed to study changes in the degradation speed of PVC due to certain additions. A change, for example, is found for PVC degradation when blended with PMMA, PCL and SAN.
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