Polypropylene (PP) has the advantages of being nontoxic and inert to liquids and drugs. Its low cost and the ease with which it can be extruded or shaped are also important.
- Alpha radiation:
Polypropylene is widely used in the automobile industry for parts like dashboards and bumpers. If you irradiate polypropylene with alpha particles under certain atmospheric conditions it has been determined that an increase in its surface free energy results in greater wettability to certain liquids, such as water, formamide and diiodomethane.
- Beta radiation:
Is used for cross-linking of plastics and therefore is not relevant for polypropylene.
- Gamma radiation:
In the medical industry, it is necessary to sterilize these materials using gamma radiation to ensure total and reliable sterility. However, gamma-irradiated polypropylene is subject to dicoloration (yellow) or embrittlement over time. Radiation causes degradation of the polymer by direct energy transfer and subsequent oxidation.
Methods to improve polypropylene’s resistance to such degradation are focused on the relationships of morphology and radiation effects.
The need for radiation sterilizable plastics which are resistant to this type of degradation is important because of the increased use of gamma irradiation as a preferred sterilization method.
It is generally known that random copolymers (such as QT73A or QT73AV) are more resistant to gamma radiation than homopolymers.