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Study on the Rheological Behavior for Polymer Melts and Concentrated Solutions The Molecular Theory of Visco-elasticity for Recoverable Strain and Swelling Ratio of Homo-polymers Melts Extrudate
Song Mingshi,Yang Zhihong
Author NameAffiliation
Song Mingshi Laboratory of Polymer Physical MechanicsResearch Institute of Polymeric Materials Beijing University of Chemical TechnologyBeijing 100029 
Yang Zhihong Laboratory of Polymer Physical MechanicsResearch Institute of Polymeric Materials Beijing University of Chemical TechnologyBeijing 100029 
Abstract:
Based on the structural model of multiple entangled transient networks and the mechanism of multiple reptation by dynamic reorganization of entanglements,the probability distribution function of the end - to - end vector for entangled constituent chain,the conformation probability distribution function of entangled polymer chain,the visco - elastic free energy of deformation of polymeric melts under stress, and the recoverable visco - elastic free energy of deformation of extrudates without stress were calculated by the combined method of statistical mechanics and kinetics. A new molecular theory of visco - elasticity of recoverable strain for extrudates of polymers was proposed. The memory function and elastic modulus were derived from the molecular theory of visco - elasticity of recoverable strain for extrudates of polymers. When the memory function is introduced into the O - W - F type of constitutive equation with the Cauchy - Green and Finger tensors for simple strain shear fluid,then the dependence of viscosity and first normal - stress difference coefficient on shear rate was formulated. A new method for determining the visco- elastic parameters(η0,GN and ψ10)and the topologically constrained dimension numbers( n' and a)was used to study on the relations of recoverable strains to the conditions of extrusion. It is well known that the total strain consists of elastic and visco - elastic strains,when the unified structure parameter of the fraction of trans - isomer conformation of polymer chains under elastic and viscoelastic strain state is introduced into above expressions of free energy of deformation. A new relationship between the recoverable strain and the swelling ratio for extrudates is obtained and a new equation of swelling ratio for extrudates was derived. At the same time,based on the material function a set of new relationships between the recoverable strain( SR)with the condition of extrusion[temperature,rate of extrusion,extrusion die and length to diameter ratio( L / D)]and the primary structure of resins was developed. These equations were verified by a great amount of experimental data. It shows that they are an excellent agreement between theese theoretical equations and experimental data.
Key words:  Recoverable strain,Theory of visco - elasticity,Swelling ratio of extrudates,Polymeric melts,Transient networks,Material function
FundProject:国家自然科学基金资助项目(5947303)
高分子熔体和浓溶液流变性能的研究
宋名实*,杨志洪
摘要:
基于多重缠结网络结构模型和高分子链上缠结点在流动中可进行动态解缠和再缠结的多重蠕动机理,用统计力学和动力学相结合的方法,分别计算出了缠结链组的末端距分布函数;处于缠结状态下高分子链构象统计分布函数;受力下聚合物熔体粘弹性形变自由能和解除外力下高分子挤出体可回复性粘弹性形变自由能,提出了高分子挤出体可回复形变的粘弹性分子理论。推导出的高分子熔体的回忆函数、简单剪切流下的本构方程和物料函数,并采用一种新的方法测定出物料的四种参数:η0、GN0、n′和a。对于高分子挤出体,可回复性粘弹性形变由快速弹性形变和慢速
关键词:  粘弹性分子理论  挤出胀大  聚合物熔体  流变性能  物料函数  可回复性形变
DOI:1003-7713/2000/06-0699-22
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