A super-ductile PBT alloy with excellent heat resistance was successfully fabricated by reactive blending of poly(butylene terephthalate) (PBT) with poly(ethylene-coglycidyl methacrylate) together with linear low density polyethylene (LLDPE) and hydrogenated styrene-butadiene-styrene block copolymer (SEBS). It possesses a unique tensile stress-strain curve with no yielding point and large elongation at break, moreover, the alloy did not show serious deterioration of the mechanical properties by high temperature annealing at 1508C for 96 h. The structure-properties relationship is discussed on the basis of transmission electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, and wide-angle X-ray diffraction analysis. The outstanding ductile nature seems to come from the negative pressure effect of LLDPE (or LLDPE/SEBS) particles that dilates the PBT ligament matrix to enhance the local segment motions.
IntroductionThe development of main-chain liquid crystalline polymers (LCP) has received a great deal of attention over the last two decades primarily to extend the range of physical properties of high-performance polymers 1) . In most of the cases, they form nematic liquid crystalline phases above the crystal melting temperature. In addition to smallmolecule liquid crystals, recently, highly ordered smectic phases have also been observed in main-chain liquid crystalline polymers [2][3][4][5] . Poly(aryl ether ketone)s are one of the most well-known series of high temperature, high performance engineering thermoplastics, which have been found very useful as advanced structural materials with important applications [6][7][8] . In order to obtain different properties of poly(aryl ether ketone)s for various applications, structural modifications, such as introduction of lateral groups or biphenyl units onto the main chain, have been attempted [9][10][11] .Quite recently, thermotropic liquid crystalline behaviour of novel poly(aryl ether ketone)s with both lateral group and biphenyl mesogenic units are receiving considerable interest 12) . This new kind of liquid crystalline polymers exhibit not only nematic textures but also highly ordered smectic structures. In our previous works [13][14][15] , we have reported the synthesis and liquid crystalline behaviour of the novel poly(aryl ether ketone)s based on a biphenyl mesogenic monomer and a crystal-disrupting substituted monomer, phenylhydroquinone or chlorohydroquinone, with different difluoro monomers. These novel poly(aryl ether ketone)s have melting temperatures between 300 8C and 350 8C and are therefore ideal candidates for moldable high temperature LCPs. In LC molecular engineering, these novel materials will hopefully stimulate polymer scientists and engineers to understand their interest and potentially useful anisotropic properties.Full Paper: Novel poly(aryl ether ketone)s containing a lateral methoxy group were synthesized by nucleophilic substitution reactions of 4,49-biphenol and methoxyhydroquinone with 1,4-bis(4-fluorobenzoyl)benzene in a sulfolane solvent in the presence of anhydrous potassium carbonate. Their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques, e. g. differential scanning calorimetry (DSC), polarized light microscopy and temperature-dependent FTIR. Thermotropic liquid crystalline behaviour was observed in the copolymers containing 30 -80 mol-% mexthoxyhydroquinone. Both melting (T m ) and isotropization (T i ) transitions appeared in the DSC curves. The polarized light microscopy study of the liquid crystalline copolymers suggested their ordered smectic structures. As expected, the copolymers had lower melting transitions than the biphenol-based homopoly(aryl ether ketone)s because of the copolymerization effect of the crystal-disrupting monomer methoxyhydroquinone. Optical micrograph of the copolymer 70MH/30BP/100BF cooled from isotropic melt to the liquid crystal temperature and ann...
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