The effect of crosslinking on the properties of polyethylene/wood flour composites

In this study, the possibility of using silane technology in crosslinking composites of wood flour and polyethylene has been investigated. Composites of vinyltrimethoxy silane grafted high density polyethylene and wood flour were produced by compounding in a twin-screw extruder. Gel content analysis with p-xylene extraction revealed higher gel content in the samples where wood flour was added compared to neat crosslinked matrix. Mechanical analysis of the crosslinked composites showed increased tensile strength with increasing amount of wood flour, which might be an indication of improved adhesion between the matrix and the wood flour. The stiffness increased with increasing amount of wood flour with accompanied decrease in strain at break. Dynamic mechanical thermal analysis of crosslinked plastics and composites showed no significant shift in the γ-transition towards higher temperature for the composites compared to neat plastic. Short-term creep experiments showed reduced creep deformation with increasing amount of wood flour. Crosslinking of the composites reduced the creep deformation further. A boiling test in water followed by tensile testing showed that the crosslinked composites were less susceptible to water uptake compared to the non-crosslinked. Moreover, the decrease in tensile strength of the crosslinked composites was not as significant as for the non-crosslinked composites. Scanning electron microscopy revealed good compatibility and adhesion between the plastic and the wood flour for crosslinked composites.