Adhesion and Surface Modification

This review emphasizes the role of interactions in particulate filled composites. In an introductory section a general view is given about the factors influencing composite properties. Two basic type of interactions must be considered: particle/particle and matrix/filler interaction. The effect of the former is detrimental to composite properties, it decreases strength and impact resistance. The occurrence and extent of aggregation is determined by the relative adhesion and shear forces during homogenization. Due to matrix/filler interaction an interphase forms spontaneously in the composite with properties different from those of both components. The amount and characteristics of the interphase strongly influence composite properties. The strength of adhesion between the components can be characterized by thermodynamic quantities, mainly by the reversible work of adhesion. The most important techniques used for the estimation of the strength of interaction and the properties of the interphase are briefly reviewed. The modification of interactions is achieved through the surface treatment of the filler. Surface treatments are divided into four arbitrary groups and are discussed accordingly, i.e. non-reactive and reactive treatment, application of functionalized polymers and introduction of a soft interlayer around the particles. The practical relevance of interactions and their modification is also mentioned in the last section.