Structure and Properties of Blends of Polycarbonate and Poly(Ethylene-Terephthalate-Co-p-Hydroxybenzoate): Phase Diagram
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STRUCTURE AND PROPERTIES OF BLENDS OF POLYCARBONATE AND POLY(ETHYLENE-TEREPHTHALATE-CO-p-HYDROXYBENZOATE): PHASE DIAGRAM AND MECHANICAL BEHAVIOR ROBERT KOSFELD*, FRANK SCHUBERT*, MICHAEL HESS*, ** and WITOLD BROSTOW** * Department of Physical Chemistry, University of Duisburg, D-4100 Duisburg, Federal Republic of Germany **Center for Materials Characterization and Department of Chemistry, University of North Texas, Denton TX 76203-5371 ABSTRACT The investigation of the thermal behavior of polymer blends leads to phase diagrams which involve Important information about the system. From these diagrams, equilibrium as well as non-equilibrium phases can be deduced and ranges of miscibility or partial miscibility of the polymers become obvious. Hence the diagrams are of a great value for processing of advanced polymer blends, especially If a polyphasic polymers such as a polymer liquid crystal is one of the constituents of the system. INTRODUCTION Polymer blending has become a promising method in the search for polymeric materials with enhanced thermal and mechanical properties (and sometimes also with lower prices). To achieve this, studies were made on blends of ordinary engineering plastics (EP) with polymer liquid crystals (PLC) in order to preserve high-temperature stability, reinforcement by mesogenic groups, low thermal expansivities , etc. The large number of polymers available and the different methods of mixing open the way to numerous products. With a detailed knowledge of interrelations between blending procedures, morphology of the resulting blend, and mechanical as well as thermal behavior of the product, new materials can be tailored for sspecific applications Inearlier studies [1-41 the copolyester of poly(ethylene terephthalate and p-hydroxybenzoate (COP) was investigated In blends with poly(carbonate) (PC) and poly(ethylene terephthalate) (PET). Transesterification, phase behavior Inthe ternary system with solvent and solid state morphologies of the pure copolyester were studied. The thermal behavior of different compositions of the copolyester Is reported in [5]. Mat. Res. Soc. Symp. Proc. Vol. 171. ©1990 Materials Research Society
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MATERIALS The liquid crystalline material used in this study Is a COP containing 40 mole S PET and 60 mole S p-hydroxybenzoate (PHB). This material, with weight-average molecular mass M= 19,000, was first prepared by Jackson and Kuhfuss [6]. As discussed In (2], the polymer shows a two-phase morphology with Island structure; see also [5] and papers cited therein. The EP was a poly(bisphenol-A-carbonate) with M= 31,000, Most of the blends were prepared by dissolving certain amounts of the pure polymers Ina chloroform +trifluoroacetic acid solvent system and subsequent combined precipitation of both polymers from this solution with acetone. The precipitate was dried under vacuum and then compression molded or extruded. EPERIMENTAL TECHNIQUES The blends were analysed with light- and electron- microscopes; calorimetric experiments were carried out with a Perkin-Elmer DSC
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