双向拉伸聚乙烯的微观结构及热学表征

采用红外光谱、核磁共振波谱和高温凝胶色谱对2个双向拉伸聚乙烯试样(分别记作M1,M2)的链结构进行了表征,确定了试样的共聚单体类型、支化度、相对分子质量及其分布。利用差示扫描量热法(DSC)研究了试样的熔融和结晶行为。通过连续自成核退火热分级法测定了不同共聚物中亚甲基序列长度(MSL)的分布。结果表明:M1以短链支化为主,M2则以长链支化为主;M1的总支化度略高于M2,与红外光谱测试结果一致;MSL分布随MSL的增加呈单调递增趋势,M2的MSL集中在198,其峰面积占总峰面积的52.4%;M1的MSL分布呈现2个峰值,在MSL为61处有小峰,峰面积占总峰面积的8.3%,MSL为273处的峰面积占总峰面积的35.1%,与DSC测试的双熔点相对应。

Microstructure and thermal characterization of biaxially oriented polyethylene

The chain structures of the two samples of biaxially oriented polyethylene,M1,M2 were characterized respectively by infrared spectrum,nuclear magnetic resonance spectroscope and gel permeation chromatograph to determine their comonomers,branching degree,relative molecular weight and its distribution.The melting and crystallization behaviors of two products were studied by differential scanning calorimeter.The distribution of methylene sequence length(MSL)in different copolymers was determined by continuous self-nucleation annealing(SSA)thermal fractionation method.The results show that the short chain branching is dominant in M1 sample,and the long chain branching is dominant in M2 sample.The total branching degree of M1 sample is slightly higher than that of M2 sample,which is consistent with the results of the IR test.The distribution of MSL increases monotonously with the increase of MSL.The MSL of M2 is concentrated in 198,whose peak area accounts for 52.4%of the total peak area.The MSL distribution of M1 sample has two peaks,one peak of MSL is at 61,whose peak area accounts for 8.3%of the total peak area,and the content of MSL is the highest at 273,whose peak area accounts for 35.1%of the total peak area,which corresponds to the double melting temperature measured by differential scanning calorimeter(DSC).