Mechanical and physical properties of thermally modified wood flour reinforced polypropylene composites
¹Tallinn University of Technology, Faculty of Chemical and Materials Technology, Department of Polymer Materials, Chair of Woodworking, Teaduspargi 5, EE 12618 Tallinn, Estonia
²Tallinn University of Technology, Faculty of Mechanical Engineering, Department of Materials Engineering, Chair of Materials Science, Ehitajate tee 5, EE19086 Tallinn, Estonia
³Tallinn University of Technology, Faculty of Chemical and Materials Technology, Department of Polymer Materials, Ehitajate tee 5, EE 19086 Tallinn, Estonia
Heat treatment of wood helps to lower the hydrophilicity and polarity of wood fibres used in wood-plastic composites. By means of heat treatment it is possible to reduce the access to wood hydroxyl (OH) group, which causes hydrophilic and polarity of wood fibres. Therefore improving compatibility between the wood and polymer matrix. In this research, the effect of wood flour (WF) heat treatment and chemical modification with 3-aminopropyltriethoxysilane (APTES) were investigated. WPC test samples were prepared using alder (Alnus incana) WF with mesh size of 0.05 mm as a filler material and polypropylene (PP) as the matrix material. WF was chemically modified with NaOH and APTES to increase the adhesion and compatibility of WF to polymer matrix. The composites were manufactured using a twin-screw extruder and the test samples were made by injection molding. The composites mechanical properties were tested using three-point flexural test and Charpy impact test. The composite physical properties were investigated with Fourier transform infrared spectroscopy (FTIR). The effect of silane (APTES) and NaOH modification on thermally treated and untreated WF was examined with contact angle measurement. Comparisons were made between the untreated WF and thermally treated WF. Also the effect of NaOH and silane (APTES) modification on the properties of thermally modified and unmodified WF composite were investigated. Using WF as a filler material increased flexural strength, while impact strength decreased thus making the material more rigid and brittle. The test results revealed that there was no significant difference in the mechanical properties between thermally treated and untreated composites. However, chemical modification improved the mechanical properties of the composites.