Shear thinning behavior of linear polymer melts under shear flow via nonequilibrium molecular dynamics

doi:10.1063/1.4873709

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	Shear thinning behavior of linear polymer melts under shear flow via nonequilibrium molecular dynamics
	Xu, Xiaolei; Chen, Jizhong; An, Lijia
刊名	JOURNAL OF CHEMICAL PHYSICS
	2014-05-07
卷号	140 期号:17
ISSN号	0021-9606
DOI	10.1063/1.4873709
英文摘要	The properties of both untangled and entangled linear polymer melts under shear flow are studied by nonequilibrium molecular dynamics simulations. The results reveal that the dependence of shear viscosity eta on shear rate (gamma) over dot, expressed by eta similar to (gamma) over dot(-n), exhibits three distinct regimes. The first is the well-known Newtonian regime, namely, eta independent of shear rate at small shear rates (gamma) over dot < tau(-1)(0) (where tau(0) is the longest polymer relaxation time at equilibrium). In the non-Newtonian regime ((gamma) over dot > tau(-1)(0)), the shear dependence of viscosity exhibits a crossover at a critical shear rate (gamma) over dot(c) dividing this regime into two different regimes, shear thinning regime I (ST-I) and II (ST-II), respectively. In the ST-I regime (tau(-1)(0) < (gamma) over dot < (gamma) over dot(c)), the exponent eta increases with increasing chain length N, while in the ST-II regime ((gamma) over dot > (gamma) over dot(c)) a universal power law eta similar to (gamma) over dot(-0.37) is found for considered chain lengths. Furthermore, the longer the polymer chain is, the smaller the shear viscosity for a given shear rate in the ST-II regime. The simulation also shows that a characteristic chain length, below which (gamma) over dot(c) will be equal to tau(-1)(0), lies in the interval 30 < N < 50. For all considered chain lengths in the ST-II regime, we also find that the first and second normal stress differences N-1 and N-2 follow power laws of N-1 similar to (gamma) over dot(2/3) and N-2 similar to (gamma) over dot(0.82), respectively; the orientation resistance parameter m(G) follows the relation m(G) similar to (gamma) over dot(0.75) and the tumbling frequency f(tb) similar to follows f(tb) similar to (gamma) over dot(0.75). These results imply that the effects of entanglement on the shear dependences of these properties may be negligible in the ST-II regime. These findings may shed some light on the nature of shear thinning in flexible linear polymer melts. (C) 2014 AIP Publishing LLC.
语种	英语
出版者	AMER INST PHYSICS
WOS记录号	WOS:000336048000047
内容类型	期刊论文
源URL	[http://ir.iccas.ac.cn/handle/121111/52373]
专题	中国科学院化学研究所
通讯作者	Xu, Xiaolei
作者单位	Chinese Acad Sci, Changchun Inst Appl Chem, State Key Lab Polymer Phys & Chem, Changchun 130022, Peoples R China
推荐引用方式 GB/T 7714	Xu, Xiaolei,Chen, Jizhong,An, Lijia. Shear thinning behavior of linear polymer melts under shear flow via nonequilibrium molecular dynamics[J]. JOURNAL OF CHEMICAL PHYSICS,2014,140(17).
APA	Xu, Xiaolei,Chen, Jizhong,&An, Lijia.(2014).Shear thinning behavior of linear polymer melts under shear flow via nonequilibrium molecular dynamics.JOURNAL OF CHEMICAL PHYSICS,140(17).
MLA	Xu, Xiaolei,et al."Shear thinning behavior of linear polymer melts under shear flow via nonequilibrium molecular dynamics".JOURNAL OF CHEMICAL PHYSICS 140.17(2014).