Abstract:
The aim of this research was to prepare ultrafine fully vulcanized powdered rubbers (UFPRs) from natural rubber (NR), styrene-butadiene rubber (SBR) and nitrile rubber (NBR) by combination technologies of radiation vulcanization and spray drying. The latex form of these rubbers was changed to the vulcanized rubber latex by gamma vulcanization using gamma ray doses in a range of 0 to 250 kGy and the UFPRs particles were observed in a spray drying step. The effect of gamma radiation dose on properties such as swelling behaviors and thermal properties of irradiated rubber latices and UFPRs were investigated. An increase of gamma radiation dose affects to a decreasing of both swelling ratio and molecular weight between crosslink (Mc) of the vulcanized rubber. On the other hand, gel fraction, crosslink density, glass transition temperature and thermal stability of vulcanized rubber increased with increasing the dose of gamma rays. Moreover, the obtained UFPRs were used as toughening filler in polybenzoxazine (PBA-a) matrix. Comparing with the neat PBA-a, the glass transition temperature of PBA-a/UFPRs composites increased . Moreover, PBA-a/UFPNBR composites shows the highest value of flexural strength and flexural modulus over other composites systems at 150 kGy of gamma irradiation dose for UFPNBR vulcanization. The impact strength of all types of composites were also evaluated by izod impact test. The results show that all UFPRs can improve impact resistance of PBA-a based composites. From all results, it can be concluded that three types of UFPRs can be used as toughening fillers in polybenzoxazine matrix.
