Effects of hydrophobation treatments of wood particles with an amino alkylsiloxane co-oligomer on properties of the ensuing polypropylene composites

In this study an amino alkylsiloxane co-oligomer was used to treat the wood particles to weight percent gains of 1.5%, 4.5%, and 7.0%, respectively, and coupling effects on the properties of the ensuing wood polypropylene composites were determined. The n-propyl-trimethoxysilane (alkylsilane) and 3-amino-propyltriethoxysilane (aminosilane) were also used for comparison. Compared to composites filled with untreated particles, composites treated with co-oligomer exhibited greater reduction in both the rates of water uptake and dimensional swelling than those treated with the other two silanes. Both, the flexural- and Charpy impact strengths of the composites, were moderately reduced but the tensile strength increased up to 23% due to treatment with the co-oligomer. The different effects by the silanes were also evidenced by dynamic mechanical analysis and microscopy. These results show that use of the co-oligomer can create a highly hydrophobic composite and any improvement in the mechanical properties is comparable to that with aminosilane.