Structural characterization of polyethylenes by DSC analysis after crystallization segregation

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	Structural characterization of polyethylenes by DSC analysis after crystallization segregation
	Ma, Y; Xu, M
刊名	CHINESE JOURNAL OF POLYMER SCIENCE
	2000-11-01
卷号	18 期号:6 页码:557-564
关键词	Polyethylene Branch Point Distribution Segment Length Distribution Crystallization Segregation Dsc
ISSN号	0256-7679
英文摘要	The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/cm(3) to 0.917 g/cm(3), and the molecular weight determined by the GPC method is in the range of 1 similar to2 x 10(5). The branch paint content of the samples was determined by C-13-NMR measurements and was found to be less than 20 per 1000 C atoms along the main chain. Crystallization segregation DSC technique (CSDSC) was used to characterize the branch point distribution or the segment length distribution of PEs. The crystallization segregation was performed in a successive annealing process at decreasing temperatures. The interval of two successive annealing temperatures was 6 K, and the time length of each annealing step was 2.5 h. The CSDSC results clearly indicate that all the PE samples used, including some metallocene PEs, more or less exhibit their non-uniformity in segment length distribution, and bimodal or multimodal CSDSC curves were usually observed. For quantitative characterization of the CSDSC curves and the segment length distribution two parameters, the average melting point, T-mAV, and the root-mean-square deviation of melting temperature, (DeltaT(m)(AV)(2))(1/2), were proposed. TmAV is corresponding to the average segment length due to branching and (DeltaT(m)(AV)(2))(1/2) gives information about the: width of the segment length distribution. Experimental results show that both the degree of average melting temperature depression and the width of the distribution seem to increase with increasing the branching content and are dependent on the type of comonomers. Very good reproducibility and additivity of the CSDSC method were evidenced experimentally. It was concluded that the CSDSC technique is a sensitive and convenient method for characterizing the segment length distribution of branched polyethylenes and will be of great interest in structure-property relationship studies of crystalline polymers.
语种	英语
出版者	SPRINGER-VERLAG BERLIN
WOS记录号	WOS:000165081000011
内容类型	期刊论文
源URL	[http://ir.iccas.ac.cn/handle/121111/76331]
专题	中国科学院化学研究所
通讯作者	Xu, M
作者单位	Chinese Acad Sci, Inst Chem, Ctr Mol Sci, State Key Lab Polymer Phys & Chem, Beijing 100080, Peoples R China
推荐引用方式 GB/T 7714	Ma, Y,Xu, M. Structural characterization of polyethylenes by DSC analysis after crystallization segregation[J]. CHINESE JOURNAL OF POLYMER SCIENCE,2000,18(6):557-564.
APA	Ma, Y,&Xu, M.(2000).Structural characterization of polyethylenes by DSC analysis after crystallization segregation.CHINESE JOURNAL OF POLYMER SCIENCE,18(6),557-564.
MLA	Ma, Y,et al."Structural characterization of polyethylenes by DSC analysis after crystallization segregation".CHINESE JOURNAL OF POLYMER SCIENCE 18.6(2000):557-564.