Generation of Thermoplastic Composites from Blends of Liquid Crystalline Polymerswith Polypropylene

摘要

The concept of tailoring a polymer's properties through blending is nowrecognized as a cost effective route to develop new materials with specific properties. This idea has been extended to thermotropic liquid crystalline polymers (TLCP's which have been blended with thermoplastics to form in-situ reinforced composites. These blends have the potential of being processed through various forming techniques, such as thermoforming and blow molding. Because of the high draw ratios required to generate molecular orientation in the TLCP phase, the in-situ formed sheet/film was usually very thin. In order to utilize the uniaxially oriented sheets for practical applications, it is necessary to laminate these thin sheets as prepregs in different directions to make a composite. One key factor in making laminated thermoplastic composites is that the matrix should have a melting point considerably lower than that of the reinforcing TLCP. If this condition is not satisfied, then the oriented TLCP phase will be disrupted or even melted during the lamination process. Therefore, selection of an appropriate thermoplastics/TLCP system can be difficult. An alternative is to choose a thermoplastic with a melting point lower than the TLCP which can be processed at moderately high temperatures, such as polypropylene (PP). Therefore a small amount of TLCP (less than 20 wt%) was blended with PP and extruded through a flat sheet die and drawn to high draw ratios. There was an order of magnitude improvement in torsional modulus, G', for the 20 wt% TLCP reinforced PP as compared with that for the neat PP. Reprints. (jes)