IMPACT OF CARBON BLACK CONTENT IN RELATIONSHIPS BETWEEN MECHANICAL PROPERTIES AND CROSSLINKING OF FILLED POLYCHLOROPRENE DURING OXIDATIVE AGING

ABSTRACT Carbon black (CB) fillers are widely used in elastomer compounds to improve their mechanical performance. Extensive studies conducted over more than 80 yr now have provided a satisfactory understanding of the influence of CB content on the mechanical properties of elastomers. However, in the majority of the studies devoted to aging, similar elastomer formulations with different CB contents are often considered as independent materials, which hinders the applicability of structure–property relationships. Herein, we reconcile the effects of aging and CB content by investigating the oxidative aging at 80 °C in air of a polychloroprene rubber with four different CB contents (from 10 to 45 parts per hundred of rubber). Both macromolecular network and mechanical properties are determined via swelling, uniaxial tensile, and fatigue tests. It is shown that the response of the materials can be decomposed into the contributions of elastomer matrix and fillers. The behavior of the matrix during aging is the same regardless of the CB content. Relationships between the microstructural characteristics of the matrix and the local mechanical properties are then derived. Their relevance for aged materials and for a wide range of CB content are demonstrated. Oxidative ageing is performed on polychloroprene at different carbon black contents. The apparent crosslink density is related to the one of the unfilled rubber matrix. Crosslinking of the matrix behaves the same independently of fillers content. Mechanical properties are linked to the matrix network through ageing. At moderate contents, fillers effect follows established reinforcement theories.