The characterization of interfacial strength using single-particle composites

Abstract

The adhesion between two dissimilar materials is best characterized by measurement of its mechanical strength. By determining adhesion, or interfacial strength, in the most direct way possible, one can identify more readily the relevant adhesion mechanisms that might be at play at the interface. A technique is presented here whereby a single spherical particle is introduced into a polymeric matrix and particle-matrix adhesion is directly measured. The interfacial strength is determined by submitting the single-particle composite (SPC) to a uni-axial tensile field, recording the macroscopic stress at which interfacial failure occurs and relating this stress to the actual stress experienced at the interface using elasticity theory. Experiments using glass spheres embedded in a poly(vinyl butyral) matrix showed interfacial failure at stress levels that varied significantly with the surface treatment of the glass sphere. Results from the SPC measurements compared well with those of a modified 180° peel test. The technique thus provides a measurement of the interfacial strength between two elastic materials and is particularly useful for adhesion studies pertaining to filled polymer composites. Furthermore, the results are directly related to intrinsic adhesion because the test is not affected by variables such as frictional forces, viscoelasticity, and thermal stresses. The SPC measurements are used to verify proposed adhesion mechanisms for the various interfaces and to establish the role of adhesion in highly-filled polymer composites.

Keywords:

• Adhesion measurement
• interfacial strength
• filled polymer composites
• silane coupling agents
• work of adhesion