The molecular theory of viscoelasticity for thermoplastic elastomer SBS (SIS) at large deformations

Abstract

A microstructure model for SBS and SIS triblock copolymers with hard domains as multifunctional reinforcing fillers is proposed. Based on this model and proposed mechanism of large deformations, the probability distribution function of the end-to-end vector for each constituent chain and the free energy of deformation for the total networks was calculated by the combination of statistical thermodynamics and kinetics. A new molecular theory of nonlinear visco-elasticity for SBS and SIS at large deformations is presented. It is successful in relating the viscoelastic state to molecular constitution by three important parameters (C100, C020, and C200) of the networks. The relations of stress to strain for four types of deformation, the elastic modulus and the constitutive equation for the stress relaxation were derived from this theory. It provides a theoretical foundation for studying the relationships of multiphase network structures and mechanical properties at large deformations. An excellent agreement between the theoretical relationships and experimental data from the experiments and the reference was obtained.

A New Molecular Theory of Non-Linear Viscoelasticity for Vitrifiable (or Crystallizable) Thermoplastic Polyurethane Elastomers

“…The morphology is to a certain extent similar to the one of thermoplastic copolymers SBS or SIS. The resemblance of their structures suggests the appropriateness of extending the previously developed theory for thermoplastic copolymers SBS [3] to VTPUE. In the model suggested here, the aggregates of hard-domains and softdomains are modeled by spheres of radii a dkj and a ckj , where d and c represent hard-domain and soft-domain, and k and j indicate extended and folded polymer chains.…”

“…Then the probability distribution functions of the end-to-end vector for the constituent chains by chemical conjunction, by physical adsorption, and by entanglement with different dimensions of " Ã Ã9 dk , " Ã Ã9 dj , " Ã Ã9 ck , " Ã Ã9 cj , and " Ã Ã ei in the real networks were calculated by a method described in references. [2,3,13] Probability Distribution Function of the End-to-End Vector (r9) for Constituent Chains Consisting of Primary Micro-Hard-Domains and Soft-Domains linked by Chemical Conjunction…”

“…In previous papers, [2,3] a new molecular theory of rubber elasticity with constraints of junctions, trapped entanglements, and carbon black-polymer interaction forces and a molecular theory of viscoelasticity for thermoplastic elastomers SBS (SIS) were proposed. Since the structure model of networks for VTPUE is very similar to that SBS block copolymers with soft and hard segments, [3] a similar method and procedure were used to establish the molecular theory of elasticity for VTPUE with Gaussian chains. [4] Now, the idea is extended to establish the molecular theory of viscoelasticity for VTPUE with real chains by combining statistical thermodynamics with kinetics.…”

“…Their probability distribution functions of the end-to-end vectors for the five kinds of constituent chains are calculated by a developed method. [2,3] Then the free energies of deformation for the five kinds of networks are calculated. The constitutive equations for four types of deformation, the dynamic shear viscosity, modulus and loss tangents are obtained.…”

“…Dependence of tan c on temperature for ET and ES samples:[1] ET-33-1000;[2] ET-63-1000;[3] ES-54-1367;[4] ES-30-1367. x = 10 Hz, the curves represent calculated curves with Equation (87); the points represent experimental data.…”