Evaluation of self-thermally treated wood plastic composites from wood bark and rapeseed oil-based binder

•Dust in wood bark particles act as nucleation centres affecting polymer matrix.•Favourable wood bark particles and rapeseed oil-based binder ratio is 0.85.•Mechanical performance improves through sufficient interfacial adhesion.•Self-thermally treated biocomposite is a cost-effective product. In order to construct sustainable and approachable buildings it is necessary to develop efficient building materials (thermal insulation, structural and sound-absorbing) with lower environmental impact, especially regarding the carbon footprint. Therefore, this study examines a wood-plastic composite (WPC) from wood bark particles and rapeseed oil-based binding material. The advantage of this WPC is sufficient thermal insulation and self-bearing properties for structural application. Additionally, thermal treatment or loading conditions during production are not required, which is energy and cost-efficient. WPCs were produced from different ratios of binding material and wood bark particles, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95 and 1.0. The highest strength characteristics are found with the WPC-0.85 samples, however, water resistance properties such as water absorption and thickness swelling after 28 days of immersion are only reasonable. The WPC obtained at 0.85 binding material/wood bark particles ratio is characterised by density – 357 kg/m3, thermal conductivity – 0.0706 W/(m·K), compressive strength – 1.8 MPa, bending strength – 1.2 MPa, tensile strength – 0.23 MPa, water absorption by total immersion – 38.2 vol% and thickness swelling – 2.5%.