Effect of silica particles on adhesion strength of polyvinyl chloride coatings on metal substrates

The aim of this study was to improve the adhesion performance of plasticized polyvinyl chloride (PVC) coatings on steel substrates by using nanoparticles. For this purpose, the PVC plastisol with different concentration of nano-silica was prepared and applied to bond steel joints. The adhesive strength of the joints was determined by single-lap shear test. Moreover, mechanical properties and microstructure of coating were investigated. The addition of 1wt% nano-silica to plastisol dramatically increased the lap shear strength up to 4-fold, which was an outcome of compatibilizing effect of silica. Young's modulus and tensile strength of plasticized PVC were slightly increased by adding nanoparticles, as well. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) exhibited higher inclusion size in the coating having higher silica volume which was attributed to the agglomeration of nanoparticles. In the following, the effect of plasticizer composition on the adhesion strength by replacing some part of dioctyl phthalate (DOP) plasticizer with more polar oil, epoxidized soybean oil (ESO), was examined. Although adding ESO improved the lap shear strength of the neat coating, its effect on the properties of the coatings containing silica was negligible.