Effect of the sol fraction and hydrostatic deformation on the viscoelastic behavior of prestrained highly filled elastomers

A Azoug,M F Vallat,B Haidar,R M Pradeilles‐Duval,A Constantinescu,R Nevière

doi:10.1002/app.37800

Abstract

AbstractThis study focuses on the relations between the microstructure and the viscoelastic behavior of an industrial solid propellant belonging to the class of highly filled elastomers. Precisely, the study aims at determining the impact on the viscoelastic behavior of the presence of the sol fraction inside the polymer network. The sol fraction is the part of the binder that a good solvent can extract. The solid propellant is swollen to various extents by solutions of plasticizer and polymer molecules. This swelling leads to a hydrostatic deformation of the polymer network, corresponding to an extension or contraction loading for each specimen. Prestrained dynamic mechanical analysis tests, superimposing a small oscillating strain on a prestrain, characterize the viscoelastic behavior. The degree of swelling of the network and the effective filler fraction drive the viscoelastic response. In addition, the mechanical behavior does not depend on the chemical nature of the introduced sol fraction. Moreover, a nonlinear behavior, i.e., an increase in both storage and loss moduli with increasing prestrain, is initiated at low prestrain. This nonlinearity depends on the contraction or extension of the network and could result from particles aligning with prestrain, which is expected in such highly filled materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Highlights

Solid propellants are highly filled elastomers used for propulsion of rockets and launchers
The degree of swelling resulting from this preparation procedure depends on the quantity of sol fraction re-introduced in the specimen (Figure 3 and Table I), which again depends on the ability of the molecules to penetrate the network
The aim of this study is to specify the influence of the sol fraction on the viscoelastic properties of a solid propellant

Summary

Introduction

Solid propellants are highly filled elastomers used for propulsion of rockets and launchers. Filled elastomers have a filler volume fraction of up to 80%. The incorporation of such a high quantity of fillers has two main consequences. Adding fillers to a polymer fundamentally modifies its viscoelastic properties. These highly filled materials exhibit a complex nonlinear viscoelastic mechanical behavior, which is rather problematic to model. The offered models either are phenomenological[1,2,3] or go beyond classical homogenization theories.[4,5,6,7,8] Because of complex binder-filler and filler-filler interactions on multiple length scales, local deformation mechanisms are not clearly determined

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