Proton beam modification of isotactic polypropylene

A systematic investigation of 100 keV proton-irradiated polypropylene has been carried out using mechanical tests and infrared spectroscopy. Some other polymers such as polyethylene, polyvinyl chloride, polystyrene, polyacrylic nitride and natural resin are also studied by proton, γ-ray and neutron irradiation for comparison. The experiments have shown that the mechanical properties of proton-irradiated polypropylene have dramatically changed, and both its elongation and tensile strength increase significantly at certain irradiation doses, while the other polymers undergo a rapid degradiation after 100 keV proton irradiation. The infrared spectra indicate that conformational changes have taken place in the polypropylene under proton bombardment, such as the transition from an ordered to a disordered state in the crystalline region of polypropylene, with the formation of double bonds as well as trans-conformations. This leads to the cross-linking between macromolecules of polypropylene at proper irradiation doses, thus enhancing its mechanical properties; such changes may have some potential applications.