Study on compatibility of PP-STC blends functionalized by ultraviolet irradiation

To enhance the compatibility of polypropylene (PP) with sericite–tridymite–cristobalite (STC), polypropylene was irradiated by low-energy ultraviolet (UV) irradiation within 2.5 h to introduce the oxygen-containing groups onto the PP chains. From blending the UV-irradiated polypropylene with STC, the effects of the compatibility on the structure and properties of PP–STC blends could be investigated by differential scanning calorimetry, thermogravimetry, thermomechanical analysis, wide-angle X-ray diffraction, scanning electron microscopy, mechanical properties, and melt index measurements. The experimental results show that for the UV-irradiated PP–STC blends, the degree of crystallinity is smaller than those with an unirradiated PP–STC blend, the thermal degradation temperatures are increased and the thermal stability is improved. Furthermore, with the UV time varying from 0 to 2.5 h, the melt index increases from 2.73 to 3.39 g/10 min, and the mechanical properties improve, exhibiting stiffening and toughening effects. Also a toughened morphology can be observed because of the enhanced interaction between UV-irradiated polypropylene and STC.