Wholly thermoplastic composites from woven preforms based on nylon‐11 fibers reinforced in situ with a hydroquinone‐based liquid crystalline polyester

This work concerns a novel means to generate wholly thermoplastic composites based on low‐melting thermoplastics reinforced with high‐melting thermotropic liquid crystalline polymers (TLCPs). A novel dual extrusion process was employed to generate nylon‐11 fibers that are reinforced with continuous fibrils of a hydroquinone‐based liquid crystalline polyester (DuPont TLCP, HX8000). These composite fibers display tensile properties significantly higher than those predicted by composite theory. These fibers were subsequently woven into a fabric, which in turn serves as a composite preform. Several layers of the fabric preform were stacked and consolidated to yield a composite plaque. The consolidation was carried out at temperatures just high enough for nylon‐11 to melt, but well below the melting temperature of HX8000. Fabric preform composites based on the composite fibers with ∼35 wt% HX8000 gave modulus values close to five and one half times that of nylon‐11, and strength values approximately two and one half times that of nylon‐11. The tensile and flexural properties of these composites are superior to continuous glass‐fiber reinforced composites at comparable loadings on a volume basis. Moreover, as the reinforcing fibrils are already encapsulated by the matrix, fiber wetting and fabric impregnation issues that are critical in the fabrication of continuous glass and carbon fiber composites are eliminated.