| Wood-plastic composite material(Wood Plastics Composites,referred to as WPC)is a new environment-friendly material,which is based on wood fiber(such as wood flour,bamboo flour and rice huck flour etc.)and plastic,and prepared by moulding and extrusion.It combines the advantages of wood fiber and plastic,and now has been widely used in the garden architecture,furniture,car interiors and other fields,however,its appearance,performance and service life will be seriously affected by thermal decomposition in the preparation process and thermal expansion,outside destroy,water absorption in using process.In order to study the thermal properties,mechanical and water absorption performance of WPC,in this paper,The effect of wood fiber type,wood flour content and particle size on thermal,mechanical and water absorption properties of HDPE-based plastic composite were studied,the wood filler parameters with best properties was determined.And HDPE/wood powder composites filled with different particle size of calcium carbonate(800 mesh,1250 mesh,3000 mesh and nanoscale),talc(800 mesh),wollastonite(800 mesh),nano A1203 and nano OMMT mineral filler filled material were studied,the influence law of the kinds,content and particle size of inorganic filler on thermal performance,mechanical and water absorption performance of composite were studied.The main conclusions can be drawn as follows:(1)The analysis of the HDPE based composites filled with different wooden fillers showed that,the composite with minimum CLTE is HDPE/wood composite(50.19 X 10-6/?),CLTE of HDPE composites filled with bamboo powder,rice husk powder increased 9.03%and 20.04%respectively;the heat resistance of HDPE/wood composite was the best,the initial weight loss temperature Ti and melting enthalpy ?H were 288.2?and 24.57 J/g.And its tensile strength,flexural strength,impact strength were 14.69 MPa,42.39 MPa and 3.60KJ/m2 respectively;the 24h water absorption of HDPE/wood composite,HDPE/bamboo composite and HDPE/rice composite were 0.89%,0.59%and 0.49%respectively..(2)The analysis of the HDPE based composites filled with different wood content(50wt%,55wt%,60wt%and 65wt%)showed that:when the wood content increased,CLTE of the composite significantly reduced,the CLTE of composite filled with 65wt%wood content decreased by 28%than 50wt%;the more the content of wood,the higher the initial decomposition temperature Ti,the smaller the heat of melting enthalpy AH;with the increase of the wood content,the mechanical properties of the composites increased first and then decreased,composite with wood content 55wt%has the best comprehensive mechanical properties,the bending strength and impact strength were increased 27.45%and 26.79%than that of the 50wt%wood content;24 h water absorption rate gradually increased with wood content increased.(3)The analysis of HDPE composites filled with different particle size(40 mesh,60 mesh,80 mesh and 100 mesh)showed that along with the particle size of wood flour decreased,CLTE of the composite showed a trend of decrease,CLTE of HDPE composite filled with 100 mesh wood powder reduced 19.68%,5.47%and 19.68%respectively than composites with the particle size of 40 mesh,60 mesh and 80 mesh;With wood powder particle size decreased,the initial weight loss temperature Ti of two weight loss stages after 2000? and the melting enthalpy ?H was decreased;When the particle size was 60 mesh,the comprehensive mechanical properties of the composite was the best;the smaller the particle size,the smaller the 24h water absorption.(4)HDPE/wood composites were prepared filled with different CaCO3 content(Owt%?3wt%?6wt%?9wt%?12wt%),the test results showed:CLTE of the composites first decreases and then increased and then decreased,composite with 6wt%CaCO3 has the minimum value;the more the content of CaCO3,the higher the initial weight loss temperature Ti of the first decomposition stage after 200?,and the lower initial weight loss temperature Ti of the second decomposition stage,the composites melting peak temperature Tm and the melting enthalpy ?H were first increased and then decreased,6wt%showed a maximum value;composite with 6wt%CaCO3 has the highest tensile strength,composite with 9wt%CaCO3 has the highest bending strength and impact strength and composite with 12wt%CaCO3 has the minimum water absorption.(5)HDPE/wood composites were prepared filled with different talc content(Owt%?3wt%?6wt%?9wt%?12wt%),the test results are as follows:CLTE of the composites first decreased and then increased,composite with 6wt%talc has the minimum value;TG data showed,the more the content of talc,the higher the initial weight loss temperature Ti of the first decomposition stage after 200?,and the lower initial weight loss temperature Ti of the second decomposition stage;The DSC analysis showed that,the melting peak temperature Tm and the melting enthalpy ?H of the composites increased at first and then decreased,composite with 6wt%talc has the maximum value;composite with 6wt%talc has the highest tensile strength and impact strength,composite with 9wt%talc has the highest bending strength and 12wt%has the minimum water absorption.(6)HDPE/wood composites were prepared filled with different wollastonite content(Owt%?3wt%?6wt%?9wt%?12wt%),the test results are as follows:CLTE of composite with 6wt%wollastonite has the minimum value;TG data showed the more the content of wollastonite,the lower the initial weight loss temperature Ti of the first decomposition stage after 200? and the higher initial weight loss temperature Ti of the second decomposition stage;the DSC curve showed that the melting peak temperature Tm and the melting heat enthalpy ?H showed a downward trend;composite with 6wt%wollastonite has the highest tensile strength,composite with 12wt%wollastonite has the highest bending strength and the minimum water absorption,and composite with 9wt%wollastonite has the highest impact strength.(7)HDPE/wood composites were prepared filled with different nano CaCO3 content(Owt%,2wt%,4wt%,6wt%),the test results are as follows:the CLTE of composite with 4wt%nano CaCO3 was minimum,and bending strength,tensile strength and impact strength were maximum,and increased by 32.85%,11.10%and 11.10%respectively;with the content of nano CaCO3 increased,the weight loss temperature Ti of the two decomposition stage after 200 ? increased,the melting temperature and melting Tm and thermal enthalpy ?H decreased;the water absorption decreased with the increasing content of nano CaCO3.(8)HDPE/wood composites were prepared filled with different kinds of nano fillers(nano CaCO3,nano OMMT,nano Al2O3),the test results are as follows:the CLTE of composites filled with the three kinds of fillers were significantly decreased,nano CaCO3 has the obvious decrease;the initial weight loss temperature Ti of the two decomposition stage after 200? of the composites filled with nano CaCO3 and nano Al2O3 increased,and the water absorption lower than the composite without filler,but the initial weight loss temperature Ti of the composites filled with nano OMMT was lower and the water absorption higher than the composite without filler;DSC curve showed that the melting peak temperature Tm and the melting heat enthalpy ?H decreased;and the addition of three kinds of fillers,the mechanical properties of composite materials were improved,and nano CaCO3 had the best effect,followed by nano Al2O3 and nano OMMT.(9)HDPE/wood composites were prepared filled with CaCO3 with different particle size(800 mesh,1250 mesh,3000 mesh,nanometer),the test results are as follows:the smaller the particle size of CaCO3,the smaller the CLTE of composite;the smaller the particle size of CaCO3,the lower the initial weight loss temperature Ti of the first decomposition stage after 200? and the higher initial weight loss temperature Ti of the second decomposition stage;the DSC curve analysis results showed that the melting peak temperature Tm and the melting enthalpy ? H was reduced;the mechanical properties of composites filled with micron CaCO3(800 mesh,1250 mesh and 3000 mesh)increased with particle size decreases;but the tensile strength and impact strength of the composite filled with nano CaCO3 and 3000 mesh were almost equal;the 24h water absorption also decreased with the decrease of particle size(micron level),and the 24h water absorption of composites filled with nano calcium carbonate was between 1250 and 3000 mesh. |
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