An Insight on processing and characterization of in-situ and in-situ hybrid composites with liquid crystalline polymers

Abstract

Blends of a liquid crystalline polymer (LCP) and a thermoplastic are generally immiscible. They are termed as 'in-situ composites', taking into account of the formation of LCP fibrils capable of reinforcing the resulting blends. Blends of Vectra A950 (VA950) with poly (trimethylene terephthalate) (PTT) showed better melt processibility as a result of partial LCP fibrillation. The best LCP dispersion was found at the lowest processing temperature and the smallest LCP content. The modulus and thermal stability were improved. VA950 was found to accelerate the non-isothermal crystallization rate of the PTT phase by serving as a nucleating agent. The microwave-synthesized spherical zinc oxide (ZnO) particles were introduced to the blends of VA950 and poly (ethylene terephthalate) (PET). ZnO reduced the LCP fibrillation owing to its lubricating effect, retarded the PET melt crystallization rate, and yet improved the tensile modulus. An increase in the extent of triclinic crystalline phase of PET as induced by microwave radiation was promoted in the presence of VA950, yielding improved mechanical properties. Multi-walled carbon nanotubes (CNTs) were introduced to polycarbonate/LCP blends where the LCP chosen were VA950 and Vectra V400P (V400P). CNTs showed better affinity with LCP and consequently prohibited LCP fibrillation leading to the disruption of conductive pathways. As a result, a greater CNT loading was required to reach a percolation threshold compared to the composites without LCP. The value of storage modulus showed improvement by the addition of CNTs or VA950.