Radiation Degradation of Polypropylene-Molecular Weight and Melt Viscosity Change

Isotactic polypropylene is widely used for production of disposable syringes and for some other single use medical products. Under irradiation the yield of scission is significantly greater than the yield of crosslinking, resulting in a deterioration of mechanical properties. In addition a slow process of chain autooxidative degradation, following irradiation, usually takes place. Two commercial resins and an additive-free isotactic polypropylene were used for studies in this work. The molecular weight distribution has been measured by high pressure, high temperature liquid chromatography, in order to determine the immediate effect of radiation degradation. This was accompanied by the melt viscosity measurements. These data may be useful to predict the short and long term mechanical properties of polypropylene made products, sterilized by ionizing radiation.