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

• Published in: Polymer engineering and science 1994-09, Vol.34 (17), p.1336-1345
• Main Authors: Engberg, K., Strömberg, O., Martinsson, J., Gedde, U. W.
• Format: Article
• Language: English
• Subjects: Analysis; Applied sciences; Blends; Exact sciences and technology; Forms of application and semi-finished materials; Polymer colloids; Polymer industry, paints, wood; Polymer liquid crystals; Technology of polymers; Thermal analysis
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.760341706

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.