Influence of -radiation input dose and post-radiation high temperature shear grinding on polypropylene functional group composition

The effect of gamma-irradiation in vacuum and air followed by HTSG of polypropylene (PP) is studied using both infrared (IR) spectroscopy and computational chemistry at the correlated G3(MP2)B3 molecular orbital theory level. gamma-irradiation of PP in vacuum was found to primarily induce unsaturation and hydroxyl formation from residual system water whereas gamma-irradiation of PP in air oxidizes the polymer and degrades the backbone in a thin layer due to oxygen permeability limitations as supported by the computational thermodynamics results. HTSG of the irradiated PP produced smaller particles than un-irradiated PP. HTSG of the irradiated PP led to a decrease in the IR band intensity from degradation due to a nominal homogenization of the pellet. HTSG of air irradiated PP led to a reduction in IR vibrational band intensity from oxidation due to thermal degradation. Hightemperature shear grinding of gamma-irradiated PP produces variable chemical and physical composition depending on irradiation input dose and environmental conditions. The combination of gamma-irradiation and HTSG may be of benefit in recycling polypropylene.