PHYSICOCHEMICAL AND MECHANICAL CHARACTERI ZATION OF ALUMINUM-ALLOY POLY(VINYLIDENE FLUORIDE) JOINTS

The present study aims at understanding physico-chemical and mechanica l phenomena in an adhesive-bonded joint interface (PVF2/epoxy/Aluminum Alloy). We focus on the treatment of the polymer, a chemical attack n amed Tetra-etch. The influence of treatment time on the surface compos ition and the moistening capacity of the adhesive are correlated to th e behavior of the mechanical adhesive-bonded joints. The joints mechan ical properties are measured by double-lap shear test. The sample hole and the loading procedure insuring uniform strains in the bonded zone and the best contact are determined by simulations using the FORGE 2( R) software. The shape is chosen in the same way. By XPS, a decrease i n the fluorine concentration with treatment time is noted in relation with an increase of the oxygen concentration, as compared to the refer ence sample. We can also note that the carbon contributions are more i mportant. For a treatment of 15 min the amount of fluorine is minimum (maximum for the oxygen) After 1 hour, it rises while oxygen falls. Fo r a 15 min treatment, the adhesive's wetting ability is improved. This is in relation to critical surface energy measurements (gamma(c) is h ighest). Due to the difficulties in the identification and quantificat ion of functional groups through the direct application of XPS, we hav e been led to use chemical derivatization techniques. The Tetra-etch t reatment introduces a weak number of insaturations. From the mechanica l point of view, the adherence tests lead to the classification in ter ms of rupture force: F-ruptdegreased<F-rupt1h<F-rupt1min<F-rupt15min. The frature surface analysis reveals a fracture in the polymer. The lo calisation is closer to the interface with the adhesive when the fluor ine concentration increases, before adhesion. The creation of bands be tween the polymer and the adhesive is favoured by the chemical species modified by the treatment. We can thus establish a connection between the surface concentration modifications due to the treatment and the adherence properties, allowing an optimisation of the polymer surface treatment.