塑料瓶材質(zhi)中密(mi)度(du)(du)(du)(du)聚乙烯(xi)介紹,中密(mi)度(du)(du)(du)(du)聚乙烯(xi),是在合成(cheng)過程中用(yong)(yong)(yong)α烯(xi)烴共聚,控制(zhi)(zhi)密(mi)度(du)(du)(du)(du)而(er)成(cheng)。1970年美國用(yong)(yong)(yong)漿液法制(zhi)(zhi)出,其生產(chan)合成(cheng)工藝(yi)采用(yong)(yong)(yong)LLDPE的方法。α烯(xi)烴常(chang)用(yong)(yong)(yong)丙(bing)烯(xi)、1-丁烯(xi)、1-己烯(xi)、l-辛烯(xi)等,其用(yong)(yong)(yong)量(liang)的多少(shao)影(ying)響著密(mi)度(du)(du)(du)(du)大小,一(yi)般。烯(xi)烴用(yong)(yong)(yong)量(liang)為5%(質(zhi)量(liang)分(fen)(fen))左右。MDPE分(fen)(fen)子主(zhu)鏈(lian)中平均每1000個(ge)碳原子中引入(ru)20個(ge)甲基支(zhi)鏈(lian),或(huo)13個(ge)乙基支(zhi)鏈(lian),其性能變(bian)化由支(zhi)鏈(lian)多少(shao)及長(chang)短不(bu)同而(er)定(ding)。共聚可(ke)使其晶體小的片晶之間的連接鏈(lian)增多。MDPE的特點是耐環境應(ying)力開(kai)裂性及強度(du)(du)(du)(du)的長(chang)期保持性。MDPE的相對密(mi)度(du)(du)(du)(du)為0.926-0.953,結晶度(du)(du)(du)(du)為70%-80%,平均分(fen)(fen)子量(liang)為20萬(wan),拉伸(shen)強度(du)(du)(du)(du)為8-24兆帕,斷裂伸(shen)長(chang)率為50%-60%,熔融溫度(du)(du)(du)(du)126-135℃,熔體流動速率為0.1-35克/10分(fen)(fen)鐘,熱變(bian)形溫度(du)(du)(du)(du)(0.46兆帕)49-74℃。MDPE可(ke)用(yong)(yong)(yong)擠出、注射、吹塑、滾(gun)塑、旋轉、粉末成(cheng)型加工方法,生產(chan)工藝(yi)參數與HDPE和(he)LDPF相似,常(chang)用(yong)(yong)(yong)于管材、薄(bo)膜、中空容器等。