Structure and properties of ultrafast photo-degraded molten polypropylene in a transparent barrel extruder

A novel single screw extruder, with high transparent quartz glass as barrel, was employed to carry out reactive extrusion for ultrafast photo degrading molten polypropylene (PP). Ultraviolet (UV) was adopted to irradiate the molten PP to induce radical reaction and hereby to degrade PP macromolecules during extrusion. Compared with photo degradation of PP in solid state, reaction efficiency and uniformity in this process were greatly improved. Reactive degree was controlled by varying screw speed and photo-sensitizer (benzophenone, BP) concentrations. The structure and properties of degraded polypropylene was characterized by melt flow rate (MFR), Fourier Transform Infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and tensile properties test. After extrusion with UV irradiation, the melt flow rate increased and crystallization temperature decreased of the degraded samples. FT-IR showed no obvious CO groups were formed in molecular structure, indicating the oxidation reaction was very minimal.