To decrease climate changes, more research focuses on decreasing waste wood biomass (WWB) burning and increasing its conversion into value-added products. The WWB was isolated from model wood processing wastewater with a new hybrid coagulant by the coagulation/flocculation method. This study is aimed to characterize the WWB and to investigate its effect in the composition of a hybrid lignocellulosic filler on the properties of recycled polypropylene (rPP)-based wood–plastic composites (WPCs). The waste biomass contained high-molecular lignin and hemicelluloses substances and represented a finely dispersed powder. It was hydrophobic and was characterized by enhanced thermal stability. To minimize the negative effect of polymer wastes on the environment, recycled polypropylene as a polymer matrix was used with the hybrid filler in fabricating WPC samples. The presence of the coagulated WWB in the hybrid filler composition positively affects the mechanical properties, water uptake and dimensional stability of the composite samples. Such a behavior of the waste biomass showed its function as a compatibilizer, which promoted the interfacial adhesion in the composite system.

A wood residuesawdust of the mechanical processing of aspen (Populus tremula) woodwas used to obtain a short fibre filler in the form of the modified microparticles < 250 µm for polymeric composite materials. To reduce energy input for wood size reduction and the activation of the lignocellulosic matrix for modification, low temperature acid hydrolysis of the residue under mild conditions was carried out. The effect of the pre-treatment parameters (acid concentration, hydrolysis duration, hydromodulus) on the fractional and chemical composition as well as on the zeta potential and contact angle of the obtained filler were studied. A comparison of the mechanical properties (tensile, bending) of the composites filled with initial sawdust and hydrolysed microparticles modified with a non-stoichiometric polyelectrolyte complex showed a pronounced improvement of the mechanical properties of the composites filled with modified wood microparticles.

A lignin-containing adhesion enhancer, a water-soluble polyelectrolyte complex (LPEC) composed of soda hardwood lignin (HASL) and polyethylenimine (PEI), and the effect of the treatment of hydrolyzed and ammoxidized aspen sawdust with the LPEC nanoparticles were studied relative to the properties of wood-plastic composites (WPCs) based on recycled polypropylene (rPP). The presence of the excess of free amine groups and salt bonds between PEI and soda lignin, forming hydrophobic sites in the LPEC structure, caused the enhanced surface activity of the LPEC. The treatment with the LPEC nanoparticles increased the content of the fixed nitrogen in the modified sawdust samples and was accompanied by decreasing their water sorption and increasing contact angles that favored the decrease in the polar part of their surface free energy. The decreasing wetting ability enhanced the mechanical and water sorption properties of the obtained WPC samples. The improvement of the interfacial adhesion between the nitrogen-containing groups of the treated sawdust and the oxygen-containing groups of rPP was explained by the formation of both covalent and physicochemical bonds.

No abstract

The aim of this work was to functionalise birch wood sanding dust, a waste from plywood production, for obtaining recycled polypropylene-based wood-polymer composites (WPCs). The functionalisation of the lignocellulosic waste was carried out through a two-step procedure, namely, by its alkaline pretreatment, followed by amination. The alkaline pretreatment increased the amount of weak acid functional groups, decreased the content of hemicelluloses and enhanced the relative content of cellulose in the lignocellulosic matrix. The amination of the alkaline treated dust was performed with diethylepoxypropylamine. This functionalisation allowed introducing tertiary amino groups in the matrix, the amount of which, in terms of nitrogen content, was 1.6% and 3.4%. The WPC samples were prepared from recycled polypropylene and the aminated dust microparticles -by extrusion and moulding. The complex functionalisation of the birch sanding dust favoured the gain in the mechanical and hydrophobic properties of the WPC samples. Despite the positive effect of the functionalisation on the mechanical properties, the enhanced content of nitrogen in the dust particles deteriorated the hydrophobicity of the WPC samples due to the excess amount of hydrophilic amine groups in the lignocellulosic matrix.