Self‐Reinforced melt processible polymer composites: Extrusion, compression, and injection molding

Abstract

Rheological properties, extrusion, fiber spinning, compression, and injection molding of blends of polycarbonate and two thermotropic liquid crystal polymers based on wholly aromatic copolyesters have been studied. Blends were prepared using an internal Banbury mixer and static Koch mixer. Based upon differential scanning calorimetry and dynamic mechanical measurements, these blends have been shown to be incompatible in the entire range of concentrations. During extrusion and injection molding at high strain rates, it has been observed that thermotropic liquid crystal polymer at concentrations 2.5, 5, and 10 percent by weight in situ forms high modulus and high strength fibers within the polycarbonate matrix leading to self‐reinforced polymer composites. The tensile strength of the composite containing 10 percent of liquid crystal polymer exceeds that of the pure components. In addition, anisotropy of properties of the injection molded parts has been found to substantially reduce in a comparison with that of liquid crystal polymer. The processing conditions and technique for the production of self‐reinforced polymer composite during processing of the blends have been identified. This has been done by measurements of mechanical properties, direct observation of morphology, and by theoretical calculation using simplified composite theory for the unidirectional continuous fiber‐reinforced composites. At the high concentrations, 25 and 50 percent by weight, thermotropic liquid crystal polymer forms large spherical droplets inside polycarbonate leading to highly brittle material. This is in distinction from the fibrous, high modulus tough composites formed at the lower concentrations.

In situ compatibilization of a polyetherimide and a thermotropic polyester using an epoxy resin

“…These results indicate the effectiveness of the reinforcing action of the liquidcrystalline polymer, mainly due to the fibrillar morphology obtained during mixing, as already reported in the literature [19][20][21]. No significant role seems to be played by PKFE, probably ascribable to the low extent of interchain reactions between the components, which result in an insufficiently improved adhesion.…”

“…Additionally, to obtain fibrils of large aspect ratio, a proper concentration of TLCP is compelled together with a proper value of the viscosity ratio between TLCP and thermoplastics [8,9,14,17,18]. Excellent mechanical properties have been achieved for blends of thermoplastics and LCPs when partial miscibility exists and, in some cases, also when they are not miscible or compatible [19][20][21].…”

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

“…After primary and secondary differentiation of ! ),.FP with respect to r and l, the curved energy surface is found to have a barrier with a saddle point at r* and l*, which are given by r* =2a.//),.f l* =4a.//),.f (2) and ! ),.FP * =nr* 2 l*!…”

“…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.…”

In Situ Reinforcing Elastomer Composite Based on Polyolefinic Thermoplastic Elastomer and Thermotropic Liquid Crystalline Polymer

“…The morphology and the resultant properties of the blends are highly dependent on the processing conditions and the composition of the blend components. Moreover, it has been reported that the viscosity ratio and the strain rate are also the important parameters governing the fibrillation of TLCP in the blend (24)- (27) . Generally, the fibrillation of TLCP is enhanced as the viscosity ratio of TLCP to polymer matrix becomes mostly less than unity (28)- (29) and it has also been reported that the elongational flow causes more extensive fibrillation than the shear flow (30)- (32) .…”