Effects of glass fiber reinforcing and thermal post-treatment on the mechanical properties and crystallization behaviors of polyoxymethylene

Polyoxymethylene (POM)-based composites reinforced with pristine short glass fiber (SGF) and surface modified SGF with silane coupling agent (SGF550) were prepared by a twin-screw extruder, and then injection molded via various processing, including natural air-cooling, water-cooling, and oven heat-treating. The mechanical properties, micro-structures of tensile fracture surfaces and crystallization behaviors were investigated. The results indicated that the above properties were tightly related to the interfacial bonding ability. POM composites reinforced with SGF550 can significantly improve the tensile strength by 33%-43% and the elongation at break by 50% and 66%, comparing with POM/SGF. Further considering the thermal post-treatments, prompt water-cooling can induce insufficient crystallization and form tough amorphous regions beneficial to lock firmly with SGF550, thus enhancing the mechanical properties. This work commits to propose an idea to improve performance by means of screening different processing techniques, and provide a route to tailor some nature of thermoplastics to meet practical application. Based on the lightweight trend, these reinforced composites can be made parts with high load-bearing requirements, instead of the original metals, such as silent gear, automobile, and machinery instruments.