Filament winding of bicomponent fibers consisting of polypropylene and a liquid crystalline polymer

This paper is concerned with novel wholly thermoplastic composite materials suitable for use in filament winding. Bicomponent fibers consisting of a sheath of polypropylene (PP) of lower melting point and a core of a thermotropic liquid crystalline polymer (TLCP) of higher melting point were produced in a ratio of 30/70(w/w) using a modification of a standard bicomponent spinning process. The modifications were required to handle the necessity of melting the TLCP at a temperature in the range of 320°C while not raising the temperature of PP above 300°C which would lead to significant degradation of PP. The tensile modulus and strength of the fibers were 38.7 GPa and 465 MPa, respectively. A methodology was developed for establishing the conditions for filament winding these bicomponent composite fibers, which would allow adequate consolidation without disrupting the molecular orientation within the TLCP component and hence reinforcing properties. Cylinders and rings were generated with winding angles of 90 and 80°C under conditions in which the PP was melted but the TLCP retained its properties. The degree of consolidation was evaluated using the interlaminar shear strength test and optical microscopy. Because of the uniform distribution of the reinforcing component there was no failure observed in this test. The void content was determined to be 5.2%. The tubes generated from these materials have the potential for transport liquid oxygen and corrosive fluids.