Detection of Thermoluminescence in Polyether Ether Ketone (PEEK)

Dipendra Adhikari

Data is provided by the student.

Abstract

Sterilization is a mandatory process for materials used in medical applications. Sterilization procedures commonly used are steam sterilization, ethylene oxide (EtO) sterilization and sterilization by radiation. The high energy photons incident upon a polymer can cause chain scission, crosslinking, defects (trapped electrons) within the polymer matrix, and the formation of free radicals. In this research work, we used thermally stimulated luminescence (TSL) and differential scanning calorimeter (DSC) to study the effects of X- and UV-irradiation on different grades of PEEK. We have observed a major sharp glow peak at temperature of about 150°C (with other five minor peaks), at the glass transition temperature of PEEK, similar to previous researchers. After X- and UV- irradiation the peak at about 100°C is much more affected by radiation. Initially, its intensity increases rapidly with the time of exposure to radiation and then increases slowly. Also, the observation showed that, after irradiation the intensity of peak at 100ºC decreases rapidly as the time passes and the effect of radiation persists for only about 24 hours after irradiation. The PEEK polymer is affected more by X-ray in comparison with UV-radiation. TSL of preheated samples of PEEK shows glow peak at about 75ºC and its intensity is found to increase with increase in preheat temperature. Moreover, the initial major TSL peak at about 150ºC completely disappear when the PEEK (film) is preheated at 250ºC for one hour in air and it reappears again as the sample is stored for longer time (within one day) at room temperature. DSC measurement shows a large exothermic crystallization peak at temperature 180 for PEEK film. This indicates that material has a strong tendency to crystallize. We observed that the glass transition temperature (Tg) increases and melting temperature (Tm) decreases slightly as a result of X-irradiation for all types of PEEK. Similar observations were made by past researcher in PEEK for γ- and e-beam irradiation. The shift of Tg to higher temperature and Tm to lower temperature with irradiation suggest that both cross-linking as well as chain scission mechanisms take place due to X-irradiation.