Elastic moduli and failure mechanism of composites made of spherical glass beads,of polyethylene using poly (4-vinylpyridine graft butylacrylate) as an interface agent

Graft polymers were prepared by copolymerization of double bond terminated long chain poly(vinylpyridine), endowed with polar units interacting with glass, and butylacrylate (BA) having short groups interactive with polyethylene. These polymers were used to coat A glass beads which were mixed with polyethylene (PE) to obtain glass-PE-composites. Good adhesion due to the presence of the adhesive polymer, and to a glass hydrolyzing pretreatment, permits higher elastic moduli and higher tensile strengths than in their absence. The adhesive composition has some influence especially on the yield stress which is higher when using the g-polymer endowed with longer BA branches. Theoretical predictions of the moduli are discussed and do not give satisfactory results when compared with the experimental values, except at low concentrations. Failure is observed to begin in the polar zone and its mechanism appears to be dependent on the presence or absence of adhesive. The experimental stress and strain at the beginning of failure are lower for untreated fillers. The specific volume variation \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{\Delta V}}{{V_O }} $\end{document} during the tensile test appears to be an important index of adhesion. Both the critical strain at which detachment begins and the slope of the \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{\Delta V}}{{V_O }} $\end{document} curve can be assumed as effective adhesion indexes.