Coupling pattern and efficacy of organofunctional silanes in wood flour-filled polypropylene or polyethylene composites

The coupling efficacies of four silanes, i.e. n-propyl-trimethoxysilane, γ-amino-propyltrimethoxysilane, γ-methacryloxypropyl trimethoxy silane, and allyltrimethoxysilane, were investigated in wood flour-filled polypropylene or polyethylene composites. Compared to untreated composites, treatment of wood flour with these silanes alone did not cause any improvement in the mechanical strength of the ensuing composites. In the presence of dicumyl peroxide, composites treated with γ-methacryloxypropyl trimethoxy silane and allyltrimethoxysilane exhibited an increase up to 90, 60, and 50% in flexural, tensile, and impact strength, respectively. Moreover, creep deformation was inhibited during the creep recovery test. The improvement was obviously greater in polyethylene-based composites than in polypropylene-based composites. This study demonstrates that the coupling efficacy of silane depends not only on the establishment of covalent bonds between silane and the matrix, but also on the chemical structure of the matrix.