Evolution of chain entanglements under large amplitude oscillatory shear flow and its effect on crystallization of isotactic polypropylene
Evolution of chain entanglements under large amplitude oscillatory shear flow and its effect on crystallization of isotactic polypropylene
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大幅度振荡剪切流下链缠结的演变及其对等规聚丙烯结晶的影响
DOI：
10.1016/j.polymer.2019.121899
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发表时间：
2020-01
期刊：
影响因子：
4.6
通讯作者：
Jingbo Chen
中科院分区：
文献类型：
--
作者：
Bao Wang;Dario Cavallo;Xiaoli Zhang;Bin Zhang;Jingbo Chen
通过动态流变学和偏光光学显微镜（POM）研究了大幅度振荡剪切（LAOS）流动对等规聚丙烯（i-PP）链缠结-解缠结转变以及随后的结晶行为的影响。通过在 180°C 下应用 LAOS 流生成具有降低缠结密度的 i-PP。通过时间扫描流变测量来原位监测解开链的重新缠结过程。有趣的是，重新缠结动力学比基于完全缠结熔体的线性粘弹性弛豫时间的预期慢得多。此外，通过调整剪切条件（应变幅度、频率和温度），可以有效地改变缠结密度。拓扑约束较少的解开链在随后的结晶过程中发挥了独特的作用。与完全缠结熔体相比，球晶的成核密度和生长速率随着缠结密度的降低而增加，从而导致更快的整体结晶动力学。值得注意的是，相对于稳定剪切流，LAOS流可以产生较少解缠结的熔体状态，并且对随后的结晶行为的影响相应较弱。
The effect of large amplitude oscillatory shear (LAOS) flow on isotactic polypropylene (i-PP) chain entanglement-disentanglement transition and on the subsequent crystallization behavior was studied by dynamic rheology and polarized optical microscope (POM). i-PP with reduced entanglement density was generated through the application of LAOS flow at 180 °C. The re-entanglement process of disentangled chains was in-situ monitored by time-sweep rheological measurements. Interestingly, the re-entanglement kinetics was substantially slower than expectations based on the linear viscoelastic relaxation time of the fully entangled melt. Moreover, with the adjustment of shear conditions (strain amplitude, frequency and temperature), the entanglement density could be effectively modified. Disentangled chains exhibiting less topological constraints played a distinct role in the subsequent crystallization process. The nucleation density and growth rate of spherulites increased with reducing the entanglement density, resulting in a faster overall crystallization kinetics, compared to that in the fully entangled melt. It is worth to note that LAOS flow could produce a less disentangled melt state, and has a correspondingly weaker influence on the subsequent crystallization behavior, with respect to steady shear flow.
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影响因子：
4.6
作者：
Nan Tian;Dong Liu;Yanping Liu;Lingpu Meng;Xiangyang Li;Jie He;Liangbin Li;Xiuhong Li;Feng Tian
通讯作者：
Feng Tian
影响因子：
7.015
作者：
Luo, Chuanfu;Sommertt, Jens-Uwe
通讯作者：
Sommertt, Jens-Uwe
影响因子：
6
作者：
Tian Nan;Liu Dong;Wei Hanghang;Liu Yanping;Kong Jie
通讯作者：
Kong Jie
影响因子：
8.6
作者：
Luo, Chuanfu;Sommer, Jens-Uwe
通讯作者：
Sommer, Jens-Uwe
DOI：
10.1002/polb.20513
发表时间：
2005-08
期刊：
Journal of Polymer Science Part B
影响因子：
--
作者：
W. Rong;Zhongyong Fan;Yin-e Yu;H. Bu;Michael Wang
通讯作者：
W. Rong;Zhongyong Fan;Yin-e Yu;H. Bu;Michael Wang