Radiation Sheilding, Radiation Resistant & Gamma Radiation Stable Materials
Depending on their field of application, plastics can come into contact with different types of radiation, which can under certain circumstances influence the structure of the plastics. The spectrum of electromagnetic waves ranges from radio waves with a large wavelength, through normal daylight with its short-wave UV radiation, to extremely short-wave X and gamma rays. The shorter the wavelength of the radiation, the greater the propensity of the plastic to damage. An important characteristic in combination with electromagnetic waves is their dielectric loss factor. This describes the proportion of energy absorbed by the plastic. Plastics with high dielectric loss factors heat up considerably in alternating electrical fields and are consequently not suitable for use as a material for high-frequency and microwave insulating applications.
There are Two Types of Exposure to Radiation:
- UV radiation from sunlight is particularly effective in unprotected open-air applications. Plastics which are inherently resistant are to be found in the group of fluorinated polymers, such as PTFE and PVDF. Without suitable protective measures, various other plastics begin to yellow and become brittle depending upon the level of irradiation. UV protection is achieved using additives (UV stabilizers) or protective surface coatings (paints, metallization). The addition of carbon black is cost-effective, frequently used and is a very effective method.
- Gamma and X-ray radiation are frequently to be found in medical diagnostics, radiation therapy, in the sterilization of disposable articles and also in the testing of materials and in test instrumentation. The high energy radiation in these applications often leads to a decrease in the elongation characteristics and the development of brittleness. The overall service life is dependent upon the total amount of radiation absorbed. PEEK, Polyimide and the amorphous sulphur-containing polymers, for example, are proved to have very good resistance towards gamma radiation and X-rays. PTFE and POM are very sensitive and therefore are practically unsuitable for this purpose.
Radiation Resistance of Erta/Quadrant Materials - Research by CERN
Gamma Radiation Stability of Selected Plastics