Surface Energetic Characteristics of Wood-Polymer Composites, Containing a Valorised Hardwood By-Product

The aim of the study was to evaluate the surface energetic characteristics of wood-polymer composites (WPCs) based on recycled polypropylene (rPP) filled with ammoxidised lignocellulosic microparticles, obtained from aspen sawdust, a by-product of a Latvian company. The aspen sawdust, pre-hydrolysed in acidic medium, was treated with a reaction mixture of ammonium persulphate and NH4OH solution at their defined mass ratio during 120 h. The content of the introduced nitrogen was varied from 1,05 to 2,10%. It was found that the ammoxidation that was accompanied with the formation of amide linkages and the decrease of the hemicelluloses content enhanced the contact angles, decreased the work of adhesion and reduced the surface free energy of the WPC samples in comparison with the case of the composite filled with the initial sawdust. The valorisation of the wood particles increased their wettability towards the recycled polypropylene that had a positive effect on the WPC samples’ mechanical properties.