Adhesion and materials interconnection: Physicochemical and mechanical behaviour of rubber-like adhesive interfaces

This paper is devoted to the behaviour analysis of adhesion interfaces considered either from the point of view of the adherence mechanical tests, or from the point of view of the adhesive joint resistance and wet atmosphere ageing. Adhesive interfaces between rubber-like silicon polymers and oxide substrates are investigated. The first part considers the physicochemical optimisation and mechanical efficiency evaluation of primer surface treatments. A new route of optimisation for primer film elaboration is proposed, using the sol-gel chemistry. The simple-lap shear adherence test is analysed and modelled through finite element calculation. It is proved that, in the case of rubber-like adhesive, the macroscopic shear results in dominant principal tension stresses in the polymer film. It is demonstrated that the valuable criterium for adherence evaluation is the principal stretch to fracture. This applies to fracture located in the interface region as well as to fracture initiated in the polymer bulk. An additional result is the influence of the substrate surface physicochemistry on the crosslinking process of the elastomer during adhesion process. The ageing process in hot water or wet atmosphere of that kind of adhesion joints is studied by several investigation means. It is shown to be strongly dependant on the degradation mechanisms of the substrates. A basic explanation of the ageing behaviour is proposed, involving a progressive modification of the aggressive medium by the substrate corrosion residues, inducing a degradation of the interface region. The CaCO₃ reinforcing charge is proved to play a protective role, by a sacrificial action.