Thermal and mechanical properties of injection molded liquid crystalline polymer/amorphous polymer blends

Abstract

Injection molded samples of binary blends of Vectra (LCP) and the three amorphous polymers polyethersulfone (PES), polycarbonate (PC), and aromatic poly(ester carbonate) (APEC) have been subjected to morphological and rheological characterization, and coefficients of linear thermal expansion and Young's moduli have been determined. The Young's modulus of the PES/LCP blends exhibited a near lower‐bound behavior that could be predicted by the one‐adjustable‐parameter equations of Halpin‐Tsai (ζ = 0.18) and Takayanaga (b = 0.23), whereas the coefficients of linear thermal expansion followed the Takayanaga equation with a value of b = 0.50. The chain orientation of the LCP component was essentially constant in all PES/LCP blends with a Herman's orientation parameter of 0.39 ± 0.03. Transesterification reactions led to randomization of the constituents of the PC/LCP and APEC/LCP blends. The effect was more pronounced in the PC/LCP blends. The introduction of the LCP into the PC/LCP blends led to no reduction in melt viscosity and no self‐reinforcement. APEC/LCP exhibited self‐reinforcement in blends with a content greater than 27 vol% LCP, and especially the blend with 67 vol% LCP. The self‐reinforcement was caused by the presence of an oriented LCP phase, confirmed by X‐ray diffraction, and by improved interfacial bonding, presumably resulting from the transesterification reactions occurring at the phase boundaries.

Reinforced poly(ether sulfone) materials by blending with a semiaromatic liquid crystalline copolyester

“…Other articles on PES/LCP blends studied the transport properties of methanol in the blends 25 and measured the interfacial tension by different methods. 12,26 Both extruded 9,18,19,21,22,24 and injectionmolded [13][14][15]22 PES-based blends were studied. The rest of the blends were processed by other methods.…”

Phase Diagram for Liquid Crystalline Polymer/ Polycarbonate Blends

“…However, the upper part of the curve becomes higher with the increase of LCP weight fraction. The variability of Tg for immiscible LCP/PC blends has been the subject of other studies [25][26][27][28]. So far, the reason for the increase of Tg is not fully understood.…”

“…So far, the reason for the increase of Tg is not fully understood. It has been suggested that transesterification is one of the factors [25,28]. However, the variation of free volume behavior during thermally induced phase separation could be the major cause of the fluctuating Tg of the PC-rich phase [25].…”

“…The variation of free volume behavior in the blends cou1d be exp1ained in terms of this phenomenon. The phenomenon has also been reported to be the reason for phase separation in b1end systems with simi1ar components [26][27][28]. Malik et al [26] also used DSC to study the miscibility behavior in the blends ofVectra and PC (Lexan 130-111).…”

“…The miscibility was supported by the observation that the Tg of the PC-rich phase was slightly lower than that of the pure Pc. However, Engberg et al [28] studied the Tg of the PC-rich phase in PC (Lexan 141R) blended with low concentration (up to 40%) Vectra system. The Tg increased since the blend system was immiscible.…”