Radiation Cross-linking of Polymers

The scope of the invited and regular presentations at the CNCP Seminar on the commercialisation of radiation tecchnologies in Lvov covered a broad range of subjects including the use of radiation to sterilize medical products, treat gemstones, modify the chemical structure of polymers and other materials applications.

Of particular interest were presentations from a significant number of former Soviet Union nuclear and other institutes on projects for the development of commercial enterprises. Presentations were made on the modification of polymeric materials to produce roofing materials, hydrogels for bandages, special materials for personnel protection equipment as well as other innovative potential products. The development of industrial facilities to produce these products and others such as heat recoverable products and wire and cable demonstrate the capability of the institutes to develop commercially significant uses for radiation technology.

On the subject of modification of materials, my presentation dealt with the radiation cross-linking of polymers to induce improved or new properties into plastic materials. Among the materials changes that can be realized are higher use temperature, improved mechanical properties, improved chemical resistance, elastic memory and permanent electrically conductivity in materials that then exhibit a positive temperature coefficient (PTC) effect.

Products developed using the improved properties are generally designed for use in areas where the requirements are severe and other materials cannot be used. As such, they often command higher prices and can be profitable to make and sell.

Traditionally, radiation cross-linking was used to improve the properties of bulk products such as insulation for wire and cable and elastic memory products such as film, tubing and molded parts. More recently, the PTC effect induced in radiation cross-linked polymeric conductive materials has been used to design selflimiting heaters and resettable circuit protection devices. Together these applications have resulted in a current world-wide market for radiation cross-linked products of approximately $ 100 billion, which continues to grow as new products for specific applications are developed. Today the largest growth is in the relatively new area of radiation curing of inks, paints and coatings. Growth here is being driven by both the increasing cost of energy and environmental concerns.

Commercial radiation treatment of polymeric products to improve their properties is an interesting and challenging field that requires experience in materials development, radiation chemistry, accelerator technology and complex manufacturing processes. Success in developing a new product starts with a complete understanding of customer requirements. Materials and product developers use these requirements and their knowledge of materials and the effects of radiation on these materials to design and develop the product. Because of demanding customer requirements, the materials developed are complex and difficult to process, requiring the development of new manufacturing processes. Overcoming these challenges to produce a superior product that has commercial value is an exciting and rewarding work experience.

David Vroom
Ex-head of applications development at Raychem