Effect of Short-chain Branching on the Crystallization Process of Bimodal Polyethylene: Molecular Dynamics Simulation

Yan-ling HU; Xue-lian HE; Bo-ping LIU

doi:10.14028/j.cnki.1003-3726.2020.08.006

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Effect of Short-chain Branching on the Crystallization Process of Bimodal Polyethylene: Molecular Dynamics Simulation

更新时间：2022-08-31

- Effect of Short-chain Branching on the Crystallization Process of Bimodal Polyethylene: Molecular Dynamics Simulation
- Polymer Bulletin Vol. 33, Issue 8, Pages: 55-66(2020)
- 作者机构：
  
  1.上海市多相结构材料化学工程重点实验室,华东理工大学,上海 200237
  2.材料与能源学院,华南农业大学,广州 510642
- 作者简介：
- 基金信息：
- DOI：10.14028/j.cnki.1003-3726.2020.08.006
  CLC：
- Published：20 August 2020，
  
  Received：27 September 2019，
  
  Revised：01 July 2020，
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Yan-ling HU, Xue-lian HE, Bo-ping LIU. Effect of Short-chain Branching on the Crystallization Process of Bimodal Polyethylene: Molecular Dynamics Simulation. [J]. Polymer Bulletin 33(8):55-66(2020)
DOI：

Yan-ling HU, Xue-lian HE, Bo-ping LIU. Effect of Short-chain Branching on the Crystallization Process of Bimodal Polyethylene: Molecular Dynamics Simulation. [J]. Polymer Bulletin 33(8):55-66(2020) DOI： 10.14028/j.cnki.1003-3726.2020.08.006.

摘要

采用分子动力学模拟研究了短支链(short-chain branching

SCB)

特别是短支链浓度、支链分布和亚甲基序列长度对于双峰聚乙烯链结晶过程的分子机理。构建了两种不同支链分布且接近于工业双峰聚乙烯管材的双峰聚乙烯模型链:短支链全部均匀地分布在长链上或者是在短链上。模拟结果表明

在双峰聚乙烯链早期结晶过程中

存在反式构象富集现象。支链分布在长链上相比支链分布在短链上

对于诱导期前驱体的形成具有阻碍作用。双峰聚乙烯链的结晶机理取决于支链浓度:低浓度下(<5 SCB/1000C)

体系的结晶过程是处于成核过程和晶体生长过程相互竞争的状态;高浓度下(>5 SCB/1000C)

体系的结晶过程是由晶体生长过程控制。亚甲基序列长度增加

体系的反式构象含量也会增加。当支链浓度超过5 SCB/1000C时

支链分布在短链上体系的相比支链分布在长链上的体系具有更高的反式构象含量。

Abstract

Molecular dynamics simulations were conducted on bimodal polyethylene (BPE) in order to reveal the molecular mechanism of short-chain branching (SCB)

especially the effects of branch content (BC)

short-chain branching distribution(SCBD) and methylene sequence length (MSL) on BPE crystallization. This paper built two types of BPE models which were closer to the normal industrial BPE: SCBs evenly distributed on the long chain or on the short chains.

Tran-rich

phenomenon was observed during the early stage of crystallization. SCB placed on the long chain provoke a delay to the formation of precursor during the induction period as compared with the case of SCB placed on the short chains. The crystallization mechanism of BPE was dependent on the BC. When BC was lower than 5SCB/1000C

the crystallization state was a competitive state of nucleation process and crystal growth process. However

when BC was higher than 5SCB/ 1000C

the crystallization state was a crystal growth controlled state. The

trans

state population of BPE models was increased with the increase of MSL. Above 5 SCB/1000C

BPE models with SCB incorporated in the short chains show higher

trans

state population as compared with those with SCB incorporated in the long chain.

关键词

短支链分布双峰聚乙烯分子动力学模拟晶体成核

Keywords

Short-chain branching distributionBimodal polyethyleneMolecular dynamics simulationCrystal nucleation

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