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聚丙烯接枝4-乙酰氧基苯乙烯的制备及电性能 被引量:4
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作者 张文龙 胡德帅 +2 位作者 李春雨 马英一 戴亚杰 《高分子材料科学与工程》 EI CAS CSCD 北大核心 2020年第9期81-87,共7页
为了研究聚丙烯材料的制备工艺及电性能,采用熔融法制备了聚丙烯(PP)接枝4-乙酰氧基苯乙烯(AOS),研究了制备工艺对接枝率的影响及接枝率对空间电荷、介电性能的影响。结果表明,当PP用量为50 g时,过氧化二异丙苯(DCP)用量对产物接枝率呈... 为了研究聚丙烯材料的制备工艺及电性能,采用熔融法制备了聚丙烯(PP)接枝4-乙酰氧基苯乙烯(AOS),研究了制备工艺对接枝率的影响及接枝率对空间电荷、介电性能的影响。结果表明,当PP用量为50 g时,过氧化二异丙苯(DCP)用量对产物接枝率呈不同的影响规律。在DCP用量为0.12 g时,随AOS用量的增加,接枝率逐渐增大,后趋于平稳;而当DCP用量为0.04 g和0.08 g时,AOS用量的增加,接枝率先增加,后反而降低。随着温度、转速的增加和时间的延长,接枝率呈先上升后下降的趋势。因此,PP-g-AOS接枝材料的最佳工艺为m(PP)∶m(AOS)∶m(DCP)=50∶1.4∶0.08,温度190℃、转速80 r/min、时间8 min,接枝率1.14%。接枝产物抑制内部空间电荷的能力、击穿强度、体积电阻率随着接枝率的增加先上升后下降,而介电常数和介电损耗变化不大;当接枝率为1.14%时,接枝材料的电性能最佳,此时,PP-g-AOS接枝材料抑制空间电荷的效果最好,体积电阻率为5.1×10^15Ω·m,比纯PP提高了3.25倍,击穿强度为48.7 kV/mm,是纯PP的2倍。 展开更多
关键词 聚丙烯 4-乙酰氧基苯乙烯 过氧化二异丙苯 接枝 空间电荷
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Fairness in Admission:Voices from Rural Chinese Female Students in Selective Universities in Chinese Mainland
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作者 yingyi ma Lifang WANG 《Frontiers of Education in China》 2016年第1期44-73,共30页
As the Chinese mainland has transitioned from elite to mass higher education,the race to attend university has escalated to become a race to attend selective universities.This study focuses on rural female university ... As the Chinese mainland has transitioned from elite to mass higher education,the race to attend university has escalated to become a race to attend selective universities.This study focuses on rural female university students and explores how they make sense of their higher education admission experiences.We rationalize that the inquiry into fairness is crystallized through examining rural female students’voices,which remain largely marginalized from the literature.Drawing from in-depth interviews with 22 rural female undergraduates from five selective universities in northern China,we focus on their perspectives towards three key issues in higher education admission:entrance exams,region-based quotas that put them at distinct disadvantages,and new reform initiatives. 展开更多
关键词 Chinese higher education reform and fairness university admission well-roundedness rural female students
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