Changes in natural rubber mechanical behavior during oxidation: Relationship with oxygen consumption

Abstract

This paper deals with the oxidation of rubber and more specifically with the possibility of setting up relationships between chemical degradation and its impact on mechanical properties for the lifetime prediction of polymers when the degradation process does not follow a single linear Arrhenian behavior. In this study, oxidation of unfilled natural rubber is first characterized at the molecular scale using oxygen consumption measurements for temperatures ranging from 115 °C to 21 °C. The results clearly show that oxidation does not follow a single linear Arrhenian behavior. Oxidation is then characterized at two other scales: the macromolecular scale using swelling measurements, and the macroscopic scale using tensile tests. Based on these findings, the relationship between the amount of oxygen consumed by the rubber and its crosslink density is first proposed within the temperature range of 115 °C to 85 °C. Finally, the relationships between the mechanical properties (Young modulus, elongation, and stress at break) and crosslink density of rubber are discussed.