A study of chemical interactions at the stainless steel/polymer interface by infrared spectroscopy. Part 2: Mechanical properties and study of the interphase

The interaction of a thermoplastic ethylene-maleic anhydride copolymer with stainless steel has been studied by infrared spectroscopic techniques (FTIR). The aim was to improve understanding of the reaction processes at the steel/polymer interface in order to optimize the quality of assemblies in terms of adhesion and durability under the conditions which will subsequently be those of normal operation. Steel/polymer associations have been tested after being submitted to several different conditions of treatment and aging in order to understand the various phenomena which occur at the steel/polymer interphase. Mechanical behavior improves after heat treatment, and similar conclusions can be transposed to the structure after use, such as in domestic equipment. Modifications in interactions between stainless steel and polymer are caused first by the chemical reactivity of anhydride functions, and second by the mobility of organic chains which reorganize at the interphase. Analysis of failure surfaces shows several correlations between the mechanical behavior and the chemical nature of residual polymer on the metal substrate. Localization of failure depends on aging conditions and can be explained by minimization of interfacial energy between the polar structure of the metal surface and the organic chains.