Impact Of Pigments Upon The Weatherability Of Wood Fiber/High Density Polyethylene Composites

This paper selected eight kinds of organic and inorganic pigments and prepared the painted WF/HDPE composites by self-made SJSH30/SJ45 two-stage extrusion machine which were carried out weatherability test with artificial accelerated ultraviolet aging,seawater immersion aging and freezing-thawing-cycling aging according to the corresponding standards. Subsequently,the colors were measured by spectrophotometer referring to CIE1976 L~*a~*b~* color system and the mechanical properties were characterized by the method of static bending. The surface morphology and internal structure of painted WF/HDPE composites through different weatherability test were scanned by SEM.The results showed that:(1) The proper organic and inorganic pigments could paint WF/HDPE composites well.The pigments dispersed in the material evenly,so there was no stripe and mottling appeared.The color of all the painted materials whose mechanical properties were improved was colorful. The organic pigment had stronger coloration ability and could improve the strength of WF/HDPE composites greatly.(2) The artificial accelerated ultraviolet aging had harmful effects to various performance of WF/HDPE composites,however,the composites were protected effectively after adding pigments and the anti-ultraviolet aging performance improved gradually with the pigments increased.The destructive action of water on WF/HDPE composites occured mainly during the seawater immersion aging and freezing-thawing-cycling aging tests,therefore,the mechanical properties of composites whose color had little change decreased seriously.Furthermore the species and addition of pigments have no obvious effects to the performance of composites.(3) The color change of WF/HDPE composites after artificial accelerated ultraviolet aging were mainly because that ultraviolet had certain destruction to the materials surface and the pigments simultaneously.However the little color change of WF/HDPE composites after seawater immersion aging and freezing-thawing-cycling aging were mainly because that water destroyed the interface of HDPE and wood fiber on the composites surface.The mechanical properties decreasing were resulted from both ultraviolet and water after artificial accelerated ultraviolet aging,while that of seawater immersion aging and freezing-thawing-cycling aging were only resulted from water.(4) The various aging results showed that the WF/HDPE composites could be protected better by adding inorganic pigment iron red and two series of organic phthalocyanine pigments.