THE PROCESSING OF TERNARY LCP LCP THERMOPLASTIC BLENDS

The feasibility of introducing a second thermotropic liquid crystalline polymer (TLCP) as a compatibilizer, or coupling agent, in order to improve the adhesion and dispersion between components of incompatible TLCP/thermoplastic blends was investigated. Two TLCP blends of a wholly aromatic copolyester (K161) with poly(ethylene terephthalate) (PET) and polycarbonate (PC) were prepared by a two-step melt-blending process, using an aliphatic containing TLCP, PET/60% poly(hydroxybenzoate) (PHB60), as the coupling phase. Preliminary morphological evidence indicated that the K161 reinforcing phase in the ternary systems exhibited improved adhesion and dispersion in a much finer scale than in binary blends of K161/PET and K161/PC prepared under the same processing conditions. It was found that the adhesion between the reinforcing K161 and the matrix PET phases depended on both the concentration of the coupling PET/PHB60 phase and the relative composition of the two TLCPs. The improved adhesion between K161 and PC matrix with the inclusion of PET/PHB60 phase was further delineated by comparing the phase morphology and mechanical properties of the ternary blends after a cold-drawing process with those of the binary systems. While the binary systems remained practically unaffected by the cold-drawing process, the ternary blends exhibited a well aligned and elongated K161 fibrillar phase with a diameter of around 1 mum or less. An increase of both initial modulus and breaking strength suggests that the enhanced adhesion between K161 and PC facilitates a better stress transfer for the deformation of the dispersed K161 particles into oriented, ellipsoidal domains. Other characterizations, including both differential scanning calorimetry and dynamic mechanical analysis, were conducted to elucidate the nature of the interactions between the components.