【作者】 贺子如；

【导师】 金日光； 宋名实；

【作者基本信息】 北京化工大学 ， 高分子材料， 1992， 博士

【摘要】 以阴离子聚合方法合成的苯乙烯—二烯嵌段共聚物热塑性弹性体由于它具有良好的力学性能和易于加工成型的特点已获得了大规模的商业应用，大量的文献报道了它们的力学性能和熔体流变特征，但至今尚无一个合理的理论对其粘弹性进行系统而确切的数学描述和结构表征。鉴于大量的实验事实和文献依据，在作者硕士论文工作的基础上，本文提出了一个较为合理的多相网络结构模型，利用一系列结构、性能的表征手段和数学方法进行了系统的理论探讨和实验分析，综合和发展了一个新的粘弹性统计理论，它既能描述SDS弹性固体、熔体及浓溶液的粘弹性行为，又可推广用来表征溶胀网的弹性力学行为和极限断裂行为。 现代流变学认为，高聚物弹性固体与流体之间没有截然不同的界限，同一材料可兼容固体和流体两种力学行为。高聚物之所以出现各种力学状态，归咎于聚合物在不同实验条件下内部结构单元和运动单元的不同，以及各运动单元在松弛时间上的差异性。基于此概念，模型认为SDS嵌段共聚物处于受迫高弹态(如低于橡胶相的T_?时的弹性固体)时，局部链段运动是一种最基本的运动模式，此时有可能出现次级松弛转变；处于高弹态时，微区—高分子链物理吸咐链组、交联链组和缠结链组是最主要的运动单元，它们之间相互牵制构成强大的三维网络结构，提供有效的弹性应力；而处于单分子熔体状态时，由于剪切运动和布朗运动，使单分子链上的缠结链组不断破灭和再生，驱使共聚物单个大分子链的质心发生移动。随着温度的升高或剪切过程的应力活化，其运动单元发生了变化，从而表现出粘弹性材料所具有的弹性形变和粘性流动的特征，呈现出各种力学状态和转变区域。因而该微观结构模型（参见图8）可由微区和链段所构成的微区—高分子链物理吸咐链组、交联链组和缠结链组相互牵制而成的三维网络结构，以及随着剪切过程的发展PS链段不断从微区中分离出来所形成的单个大分子链构成，随着温度和剪切速率的增加，存在着四种理想的微观结构形态。从弹性体向熔体的转换经历一个力学状态转变过程，通过其中运动单元和流动单元的数目及松弛时间的变化，结合从随机统计力学计算得到的各网络链组的末端距几率分布函数，可推导出体系总的粘弹形变自由能[3-2-41式]，它包含着三项的贡献，即三维弹性网中交联链组、缠结链组和微区—高分子链物理吸附链组的弹性形变自由能贡献，单分子熔体的粘弹形变自由能贡献以及从高弹态向粘流态转换的力学状态转变自由能。从而成功地使我们早先发展起来的SDS弹性体和均相聚合物熔体的粘弹性统计理论得到了有机的统一和进一步的完善。 从体系总的粘弹形变自由能出发，本文导出了下面一系列的物理模型： 1．根据溶胀体和非溶胀体的应变储能函数，可得到四种形变类型下的应力—应变关系式； 2．从单轴拉伸下的应力—应变状态方程出发，可得到弹性体的弹性模量和柔量表达式以及充油弹性网的平衡模量； 3．可得到结构流体的记忆函数，并结合非线性积分型本构方程，得到了如下所示的各种流场下的一系列物料函数； 4．稳态剪切流的稳切粘度、第一、第二法向应力差系数、第一法向应力差、稳态起始流的切应力增长系数和第一法向应力增长系数以及稳切流静止后的切应力衰减系数和第一法向应力衰减系数；更多还原

【Abstract】 The unusual physical properties and good processability of commercial thermoplastic elastomers SDS, synthesized by anionic polymerization, hae stimulated interest in new application and new products. Many literatures have reported the mechanical properties and the flow behavior of these two -phase block copolymers. Unfortunately, a systematical and reasonable treatment on their viscoelasticity and mechanical properties has not yet been developed because of their complexity of gradual structure breakdown with increasing temperatures and shear rates (or shear stresses). From a point of view of technological importance, a better understanding and knowledge of the mechanical properties of elastomers and the processing behaviors necessitates a development towards a valid rheological equation of state.Based on a detailed investigation on the structure, morphology and mechanical properties, a multiphase model structure which varies with the temperature and rate of deformation is proposed in this thesis for styrene -diene block copolymers at solid or melt states. Further more, a statistical theory of viscoelasticity is developed for SBS(SIS) elastomers and melts or concentrated solutions. The theory can not only describe the elastic behavior of swollen and unswollen elastomers, but characterize the rheological properties of SDS structured fluids. Also, it can be extensively used to treat the ultimate properties of multiphase copolymers.It is general accepted in the modern rheology that no restricted discrepancy exists between solid and fluid of polymers. A polymer can show all the features of a glassy, brittle solid or an elastic rubber or a viscuous liquid depending on the temperature and time scale of measurement. There are different structure units and motion units at different mechanical states. Each motion or flow unit has its own characteristic relaxation time. On the basis of this concept, we consider in our model that the local motion of SDS segment chain is an ordinary motion mode when at forced high-elastic state (lower than T. of PD segment) ; While at high-elastic state, the constituent chains by crosslink, entanglement and physical adsorption in three-dimensional network are considered as elementary structure and motion units for SDS elastomers at two-phase state; While at monomolecular melt state, the network segment by tail, the entangled constituent chain and the monomolecules are the flow and motion units. The continual breakage and reformation of entangled constituent chain on monomolecules due to shear motion and local Brownian diffusion drive the movement of mass center of monomolecules. As increasing the temperature and shear stress, the PS segment is continuously pulled out from PS domain, and then migrated into D更多还原