PET in situ composites improved both flame retardancy and mechanical properties by phosphorus-containing thermotropic liquid crystalline copolyester with aromatic ether moiety

A novel phosphorus-containing thermotropic liquid crystalline copolyester with aromatic ether moiety (TLCP-AE) was used to prepare the in situ composites of poly(ethylene terephthalate) (PET)/liquid crystalline polymer. The morphological structure and properties of PET/TLCP-AE in situ composites were investigated using scanning electron microscopy (SEM), capillary rheometer, tensile tests, limiting oxygen index tests (LOI), cone calorimeter and thermogravimetric analysis (TGA). The rheological measurements show that the viscosity ratio of TLCP-AE to PET at 260 °C is less than 1, which meets a precondition for TLCP-AE to form fibrils in PET matrix during processing. The mechanical, LOI and cone tests prove that TLCP-AE can improve the mechanical properties and flame retardancy of PET synchronously. Moreover, TGA results exhibit that the initial decomposition temperatures and the final residues of PET/TLCP-AE composites increase with increasing TLCP-AE content.