用减差红外光谱分峰法测定EVA共聚物的总支化度及支化度分布

对EVA大分子链上出现的支链结构,可选用无规聚丙烯的支链甲基峰1378cm~(-1),2-乙基己烷的支链乙基峰780cm~(-1)和聚α-己烯的支链丁基峰730cm~(-1)作为测定总支化度、乙基和丁基支化度的量度,并得到1000C中各支化度的分布公式:(L.B为长支链)n_3/1000C=0.50564 A_(1378)/dt-1.01966 n_(C_2H_5)/1000C=1.27161 A_(780)/dt-7.67873nC_(4H9)/1000C=0.09113 A_(730)/dt-6.41352 n_(L.B)/1000C=0.50564 A_(1378)/dt-1.27161 A_(780)/dt-0.09113 A_(730)/dt+13.07259由于EVA共聚物中,测定峰会发生重叠,故先用减差FTIR光谱分峰法,扣除干扰峰对测定峰的影响后,对测定峰进行峰面积积分,再计算支链的数均支化度,其测定结果与~1H-NMR结果一致。

DETERMINATION OF DEGREE OF BRANCHING AND ITS DISTRIBUTION IN EVA BY FTIR

The molar ratio of ethylene to vinylaeetate in ethylene-vinylacetate copolymers (EVA) was greater than 3:1, sothe side chains were deemed consisted mainly of ethyl and butyl branches. In this work, the 1378cm~(-1) band of CH_3 side group in ataetie polypropylene was selected as key band for determination of the amount of branched chains in eopolymers, the 780cm~(-1) band of C_2H_5 group in 2-ethylhexane for ethyl branche, the 730cm~1 band of C_4H_9 side group in poly-a-hexane for butyl branches, respectively. A reasonable estimation of branched chain distribution has been carried our by following equations. n_CH_3)/1000C=(0.50546 A_(1378)/dt)-1.01966 nC_2H_5/1000C=(1.27161 A_(780)/dt)-7.67873 nC_4H_9/1000C=(0.09113 A_(730)/dt)-6.41352 nL.B/1000C=(0.50564 A_(1378)/dt)-(1.27161 A_(780)/dt) -(0.09113 A_(730)/dt)+13.07259The interference from CH_3 in acetoxyl of VA is eliminated using band substraetion manipulation in FTIR and then the number average degree of branching has been determined by above equations. The results obtained were in good agreement with those obtained by ~1HNMR technique.