Incompatible blends of liquid crystalline polymers and engineering thermoplastic

The increasing demand for the high technology market for new applications in the aerospace industry has led to the research on high performance thermoplastics as composite matrices. The inclusion of solid fibres in this class of materials during manufacturing may result in processing conditions that are too demanding. High temperature and pressure in stamping or injecting tools may result in thermal degradation of the organic matrix. Moreover, the load transfer through the fibre-matrix interface produces fibres breaking into fragments shorter than the critical length, affecting their aspect ratio, and consequently reducing the final performance of the product. The possibility of producing the reinforcing filler during the cooling cycle of the composite processing has suggested the definition of 'in situ' composite. In this paper the addition of thermotropic liquid crystalline polymer to engineering thermoplastics has been investigated. X-ray diffraction techniques have been used to evaluate the molecular orientation of the dispersed phase. The rheology and the mechanical properties of the in situ composites is related to the morphology of the material and to the processing operations.