Additive Effects on Thermotropic Liquid Crystal Polymer Alloys I. Effects of Third Component of Thermotropic Liquid Crystal Polymer on Mechanical Properties of Vectra A-Reinforced Polycarbonate

Abstract

ABSTRACT:The effects of addition of the 3rd component of thermotropic liquid crystal polymer (TLCP) on the mechanical properties and structure ofVectra A-reinforced polycarbonate (PC) were studied. The 3rd TLCP was the copolymer of p-hydroxybenzoate (PHB) and ethyleneterephthalate, known as X-7G TLCP. PC, Vectra A, and a small amount of the 3rd TLCP were blended in the molten state, the extrudate of which was cut and injection-molded. The mechanical properties of the blends were improved dramatically by addition of a small amount of the 3rd TLCP component. SEM revealed that the blend systems were always phase-separated, even after injection-molded, and the fibrils of Vectra A in the injection-molded blends became finer and longer in the presence of the 3rd TLCP. FT-IR indicated that no special chemical reaction took place between the TLCP and PC. The dynamic viscoelastic analysis indicated that the addition of the 3rd TLCP component had almost no effect on the thermal endurance of the blends. X-Ray diffraction analysis showed that the orientation ofVectra A fibril in the blend became higher when the 3rd TLCP was added, which Jed to the great improvement of the mechanical properties. Based on the assumption of additivity law, the fibril modulus was evaluated and found to be in the same order as the orientation evaluation by X-ray diffraction. The thinning of fibrils by addition of the 3rd TLCP component was discussed based on the crystallization kinetics of rodlike molecules.KEY WORDS Polycarbonate/ Liquid Crystal/ Ternary Blends/ Mechanical Properties / Morphology / Crystallization Kinetics / As one of the applications of the thermotropic liquid crystal polymers (TLCP), the blends of engineering plastics and TLCP are promising the improvement of mechanical and thermal properties due to the reinforcing function and thermal endurance of TLCP. There have been many engineering and scientific reports on this subject. Kiss 1 suggested a concept of"in situ composite," emphasizing the fact that the TLCP reinforcement could be formed "in situ" during processing. Isayev et al. 2 called them as "self-reinforced melt processable polymer composite". According to Brostow et al. 3 the composite could be classified into two kinds: one was the traditional fiber-reinforced composite, being classified as a heterogenous composite; the other was the molecular composite, such as selfreinforced plastics and the molecular composite in the strict meaning suggested by Takayanagi. 4 From many papers reported on the blends of the engineering plastics and TLCP, one can find two important facts: such blend systems are usually phase-separated and

Effects of annealing on structure and properties of TLCP/PEN/PET ternary blend fibers

“…[1][2][3][4][5][6][7][8][9] TLCPs have been used for high performance engineering plastics due to their high strength and modulus, excellent thermal endurance and chemical stability. [10][11][12][13] They consist of rigid molecular chains, and exist as ordered domains in LC state.…”

Evidence of Chemical Reaction in Binary Blends of Polycarbonate and a Semi-Flexible Liquid Crystal Polymer

“…It has been reported that, in heat-treated blends of PC and random liquid crystal co-polyester, the esterester interchange in the two polymers takes place where the bisphenol-A unit of PC first reacts with terephthalate unit and then with an oxy-benzoate unit of liquid crystal co-polyester [27][28][29][30]40], where the miscibility increases with transesterification in the blends of PC and other polyesters with LCPs. [56,[58][59][60][61] Although in the present study of heat-treated LCP1/PC blends, the origin of a chemical reaction is likely transesterification, however, due to the lack of information on the molecular weights of the utilized LCP1 and PC, we hesitated to directly specify the transesterification and instead utilized the more general term chemical reaction throughout this study.…”

“…Concerning LCP blends with PC, there exist some scientific literature including studies on various rigid and semi-rigid LCP additives, compatibilizers, and processing aids [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44], exhibiting chemical reactions, including transesterification [45][46][47][48][49]. In addition, other studies indicated that amorphous PC can be induced to crystallization by the synergistic action of LCP reactive compatibilizer [47], and transesterification in in-situ PC/aromatic-LCP blends exhibited increased compatibility consistent with improvements in mechanical property parameters of the blends [48].…”

Structure and properties of thermotropic liquid crystal polymer and poly(ethylene 2,6‐naphthalate) blend fibers

“…They are used in high‐performance engineering plastics because of their good mechanical properties and excellent thermal stability 1–4. The melt blending of TLCPs using conventional thermoplastics has attracted much attention due to the improved strength and tensile modulus of the resulting polymer composites 5–19. TLCPs show a high degree of order in the melt under shear and elongational flow fields, leading to deformation of the LC domains to form fibrils with high aspect ratios.…”