However in recent years some studies concerning UV irradiated extrusion process of molten PP have been published. He
and Tzoganakis [25] and Cao et al. [26] investigated the effect of ultraviolet irradiation on the structure and properties of
molten PP during extrusion process using a single screw extruder with quartz glass barrel. Due to the high reactive temperature
and photo-sensitizer (benzophenone) added into PP melt, this UV-promoted degradation process has very high
efficiency to break PP molecular chain.