The dissertation presents the effects of thermally modified wood in wood-plastic composites for 3D printing on the properties of filaments and 3D-printed products, as well as the findings on how the conditions of use (e.g. temperature, relative humidity) affect the dimensional stability and mechanical and physical properties of 3D-printed parts. This includes the production of filaments from wood-plastic composites, the 3D printing of samples from extruded wood-plastic filaments and the investigation of the rheological and mechanical properties of 3D-printed wood-plastic composites. The addition of thermally modified wood leads to an improved surface quality (lower roughness, higher hydrophobicity), a higher maximum storage modulus, a lower filament density, a lower glass transition temperature, a higher modulus of elasticity and a higher hardness. The tensile strength decreases with increasing wood particle content. Using microscopic techniques, we have confirmed that thermally modified wood improves the interfacial adhesion between wood particles and the polymer, the porosity is lower, and the particles are more homogeneously distributed. The best properties of 3D-printed products were measured with a 30% addition of thermally modified wood to the base polymer matrix. The mechanical properties of 3D-printed products are improved by incorporating microcellulose into the filament, mainly due to better encapsulation of the wood particles with the polymer. The addition of wood particles to PLA creates a hygroscopically active composite material that can lead to dimensional changes under variable climatic conditions and thus to a change in the shape of the designed actuators, making this material suitable for use in 4D printing.
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