Influence of the temperature on the mechanical behaviour of filled and unfilled silicone rubbers

Abstract

This paper investigates the effects of temperature on the mechanical properties of silicone rubbers. First, differential scanning calorimetry tests are performed to determine the crystallization and melting temperatures. Second, mechanical tests are carried out at different temperatures above that of crystallization, up to 150 °C. In this temperature range, the silicone rubbers exhibit entropic behaviour. The neo-hookean model is used to fit the mechanical response. Third, the effects of temperature on the hysteresis, the stress softening and the stress relaxation are studied. Strong differences are observed and discussed.

Introduction

Silicone rubbers are increasingly used in many applications that differ in nature, for instance automotive applications, food storage products, footwear, electronics. This is mainly explained by their easiness of cure and, more generally, of manufacture. Moreover, silicone rubbers do not react with most chemicals, which explains why they are used in many medical applications.

Classically, silicone rubbers are filled with mineral fillers such as silica in order to increase their stiffness. In this case, fillers greatly complicate the mechanical response by inducing numerous phenomena: non-exhaustively, stress softening [1], the Payne effect [2], [3] and mechanical hysteresis. Even although mechanical response of filled and unfilled silicone rubbers has already been characterized in the literature at room temperature [4], [5], [6], no study investigates the effects of temperature on the mechanical response, while the large variety of applications requires a large range of service temperatures. Moreover, temperature variation affects the interaction between the fillers and the rubber matrix [7] and, consequently, it is necessary to study both filled and unfilled silicone rubbers.

This paper aims, therefore, at investigating the influence of temperature above that of crystallization on hyperelasticity, stress softening, mechanical hysteresis and stress relaxation. Section 2 presents the materials and the experimental setup. Section 3 gives the results obtained for both materials. The evolution of the various phenomena involved in the deformation of silicone rubbers is discussed in Section 4. Finally, concluding remarks close the paper.