The main aim of this thesis is to study the effect of pigments on the weathering properties ofwood-polypropylene composites (WPC). The studied properties are color change, waterabsorption, thickness swelling and Charpy impact strength. The impact of weathering and UVexposure on WPCs was studied by using pigments and minerals as protective agents. The studyshows that the pigments and/or mineral fillers can be used to improve the weathering propertiesof WPCs. The effect of pigments was found to vary with the type of pigment and the method ofweathering. The black pigment, an inorganic carbon black master-batch, was found to be themost effective one in reduction of the discoloration of WPCs. By preventing discoloration, andfurther reducing the degradation of the surface of the WPC, the pigments were found to reducethe decrease in the impact strength after weathering. As well as UV protection, the moistureresistance is a significant factor affecting the durability of WPCs. The addition of mineral fillerswas found to improve the moisture-related properties, such as water absorption and thicknessswelling, of WPC significantly. According to the findings, addition of pigments and mineralfillers to wood-polypropylene composites appears to be beneficial: color stability and moistureresistance can be enhanced especially in outdoor weathering. The combined effect of blackpigment (carbon black master-batch) and wollastonite as a mineral filler was found to bring aboutthe most effective properties against weathering.
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