Processing and Characterization of Microstructure and Mechanical Properties of PC/PBT Blend

Shabani, Farzan | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49702 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Blend of Polycarbonate/ poly(butylene terephthalate) is among the most famous blends of polycarbonate/polyester with vast engineering applications and unique properties. Miscibility and compatibilization of this blend are important as they directly influence the general properties.Transesterification which occurs in the melt state, is a series of cutting and rejoining of dissimilar polymer chains. The reaction ruins the order of pure chains and forms block copolymers of different natures. Further progress in transesterification lead into a completely random copolymer of initial chains. Time, temperature and addition of catalyst can effectively influence transesterification.In this study, progress of transesterification reaction has been monitored with the aid of differential scanning calorimetry measurements. One of the main goals is to depict a clear picture of thermal behavior of the blend and effect of transesterification on the crystalline structure. It is shown that despite the general belief, crystallinity is not a good criterion for the progress of transesterification reaction. On the other hand, melting temperature can best indicate the degree of transesterification. A simple model is proposed based on the reheating cycle of DCS measurements and effect of blending temperature on the degree of transesterification has been investigated in a quantitative manner. In the next section, a phase diagram of composition-randomness is proposed and it was shown that how the amorphous phases become more miscible with increase of randomness. Lamellas thickness and their density are calculated and are included in the overall picture of the blend.The results of the DSC measurements are reexamined with other tests and analysis. Transesterification is proved to has been occurred with the aid of FTIR and the degrading effect of temperature on the chains has been investigated. The results of the thermal analysis in the first section are vindicated by rheological measurements and the abnormal crystallization behavior of the blend has been further investigated. The influence of randomness on the morphology and compatibilization of the phases has been shown in the electron microscopy micrographs and an estimation of morphology based on the randomness and composition has been proposed. Finally, three major properties of the blend, chemical resistance, mechanical strength and tribological behavior are measured and the results are compared to the previous data
  9. Keywords:
  10. Polycarbonate ; Polybutylene Terephthalate ; Transesterification Reaction ; Differential Scanning Calorimetry

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