Mechanical Properties of Polymers and Rubbers

Abstract

AbstractOne major focus of this article is on models and testing techniques that can be applied readily to the research and development of polymers and rubbers. The article is divided into five sections, with the introduction being the first section. Sections 2 and 3 deal with stress–strain relationships and time‐ and temperature‐dependent behavior. The linear Hooke's law is described first, followed by the molecular mechanism of rubber elasticity, the Mooney–Rivlin model, and the Ogden model. Three viscoelastic models are presented, together with the Boltzmann superposition principle. Various types of apparatus for viscoelastic property measurements are described. The Williams–Landel–Ferry (WLF) equation for time–temperature superposition is illustrated with experimental data.Section 4 covers the ultimate properties. Topics include: cold drawing in crystalline polymers; temperature and pressure effects on yield stress; brittle–ductile transition; crazing; fracture; tearing of rubbers: extension of Griffith theory; viscoelastic rupture of elastomers; fatigue; and the effects of molecular weight and crystallinity. The ultimate properties are more complex and less well understood. Emphasis is placed on the most important aspects and techniques for understanding and representing yielding and fracture.Section 5 is devoted to polymer blends and composites. Rubber‐toughened polymers are used to discuss the enhancement of the deformation mechanisms in polymers. A general, mechanistic model is then presented to determine the moduli, break strengths, and break strains for polymer films containing liquid and solid microfillers.