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Reinforcement of polyesters by boron minerals

Akgün, Aydın Mert
Polymers are used in areas where exposure to high-energy radiation might occur. Main effects of irradiation on polymers are crosslinking, chain scission and oxidation. Radiation resistance of polymers depends on structure, additives, or irradiation conditions. Since boron is highly effective material against radiation, especially against neutron radiation, with its high absorption cross section, boron products is used for radiation applications. The aim of this study is to investigate the effects of different types of boron minerals used as reinforcing fillers on mechanical properties, thermal properties and on radiation stability of unsaturated polyester resin. Four different boron minerals (anhydrous borax, calcined tincal, concentrated tincal and ground colemanite) with various B2O3 content were used in this study. Unsaturated polyester composites were prepared with 2%, 5% and 10% of boron mineral by weight. They were exposed to gamma radiation with irradiation dose rates of 30 Gy/h and 2500 Gy/h. Samples were characterized by ATR-FTIR, TGA, DMA and SEM techniques as well as their mechanical properties. Most satisfying mechanical test results were obtained for anhydrous borax which contains 68% of B2O3. Polystyrene formation and oxidizing reactions especially at high doses were observed from ATR-FTIR spectra. Tg of neat polyester resin was shifted from 66.3 to 74.3 °C for high doses. Neat polyester resin was thermally degraded around 410 °C and thermal stability of composites was not significantly affected by irradiation or reinforcement as seen from TGA thermograms. Agglomeration derived from higher reinforcing filler ratio was seen from SEM micrographs.