Long-term properties of polymeric materials
The main objective for this project is to obtain increased understanding and improvements regarding long-term performance of polymer systems and their interaction with the environment. Each improvement of bulk polymers such as polyethylene is of great importance for articles made of plastic materials, everything from car spare parts to pharmaceutical packages.
The migration of low molecular weight substances has to be controlled to create materials with predetermined shelf life. Antioxidants are used to stabilise polyolefins, as polyethylene and polypropylene, but the compatibility of antioxidants with these polymers is low due to the hydrophilic nature of the antioxidants. The migration of antioxidants and other low molecular weight substances present decreases the shelf life of the materials, makes lifetime predictions more difficult and is a problem in applications with high demands on knowledge of amount and properties of the migrating substances, e.g. for packages of pharmaceutical solutions. Diffusion to pharmaceutical products and provisions may imply a danger to the health of the product users. Determination of the small amount of antioxidants and their degradation products in the polymer and its surrounding media demands good optimised extraction and concentration methods using solid phase extraction and solid phase microextractions and quantifications. Our rapid low temperature test method will be further developed for the evaluation of polymer systems where small changes in the material will be detected at an early stage of aging using a special sensitive chemiluminescence method together with chromatographic fingerprinting. The project has to the end of 2004 also been financed by VR (The Swedish Research Council).