超临界二氧化碳协助双单体接枝聚丙烯

采用氧化法制备氢过氧化聚丙烯(HPP),然后用超临界二氧化碳(SC CO2)将单体苯乙烯(St)和季戊四醇三丙烯酸酯(PETA)溶胀到HPP颗粒内,再通过热引发将单体接枝到HPP上.考察了溶胀温度、压力、接枝反应温度、时间及单体用量对产物接枝率与单体接枝效率的影响,并采用红外光谱(FT-IR)、热重-差热分析(TG-DTA)、扫描电子显微镜(SEM)对接枝共聚物进行了表征.结果表明,合适的反应条件为30 g聚丙烯和0.5 g过氧化苯甲酰(BP0)在80℃反应2 h生成HPP,HPP与9 g苯乙烯(St)和季戊四醇三丙烯酸酯(PETA)的混合物(St与PETA物质的量之比为1:1)在37℃,8.5 MPa的超临界CO2中溶胀3 h,再在80℃常压下反应8 h,得到双单体接枝聚丙烯,接枝率达到28%,接枝效率大于90%,且PETA和St同时接枝到了PP分子链上,聚合物的耐热性增强.

Grafting Dual Monomers on Polypropylene Using Supercritical Carbon Dioxide as Swelling Agent

The hydroperoxidized polypropylene (HPP) was prepared by oxidizing polypropylene (PP), then monomers of pentaerythritol triacrylate (PETA) and styrene (St) were impregnated into HPP by the aid of supercritical carbon dioxide (SC CO_2), and were grafted onto the microporous HPP backbone through thermal cleavage of hydroperoxides. Effects of swelling temperature, swelling pressure, swelling time, grafting reaction time, reaction temperature, and monomer dosage on the grafting percentage and efficiency were investigated and the graft copolymers were characterized by Fourier transform infrared spectroscopy(FT-IR) , scanning electron microscopy(SEM) and thermogravimetry-differential thermal analysis (TG-DTA). The results showed that the appropriate preparation conditions of the grafting copolymer of PP were; for preparation of HPP, 30 g PP, 0. 5 g benzoyl peroxide(BPO), reaction temperaturec 80 ℃, reaction time 2 h; for swelling, 43 ℃, 8.5 Mpa, swelling time 3 h; for grafting reaction, 9 g mixture of styrene (St) and pentaerythritol triacrylate (PETA) (the molar ratio of St to pentaerythritol triacrylate 1 :1) , temperature 80℃ , reaction time 8 h. Under the above conditions, both PETA and St were grafted on PP and the graft percentage and graft efficiency reached 28% and 90%, respectively. The thermal stability of the copolymer was improved.