Study On WPC-Wood Multi-Phase Composites Window

Windows are not only indispensable functional componets of a building which is more strictly evaluated by energy saving standards in recent years,but also decrative enclosed structures,and thus they are more important to fulfil the aesthetic needs of consumers,complying the trends of returning to nature and individuation.Curently,the materials used to make window frame have serious drawbacks,such as the energy-extensive consumption and hevy pollution of aluminium,the deformation of creep and difficulty of waste disposal for polyvinyl choloride(PVC)plasric profile,and the serious shortage of natural wood resources.Innovation of materials for window frame is of key significance to scientific research and industrial pressing needs to the markets.Wood polyolefin composite was used to make window and door frames in Northeast Forestry University.However,the manufactured windows were mainly used in low-rise building becase of the creep and poor impact property of the hollow profile of wood plastic composite(WPC).In this paper,to take the advatages of protective properties of WPC and the toughness of wood,WPC-wood multi-phase composite profiles were prepared by the co-extrusion of WPC as the shell and wood as the core,and then windows were made by using the profiles as frame material.Comprehensive research was performed on the cross-sectional structure design,the extrusion,the coloring,and the aging of the WPC-wood multi-phase composite profile,on the design,the making,and the decoration of the WPC-wood composite window,and on the life cycle assessment(LCA)of the WPC-wood composite window products.The conclusions are as follows:1)WPC-wood multi-phase composite was prepared by the co-extrusion of WPC shell with wood core,using wood flour and high density polyethylene(HDPE)and laminated veneer lumber(LVL)of poplar wood as raw materials.Thus,poplar wood flour,HDPE,coupling agent maleiated polyethylene and lubricant stearic acid-polyethylene wax was mixed in a high kinetic mixer,then compounded in a twin screw extruder to prepare WPC granule,and then was co-extruded with LVL core to produce multi-phase composite profile of WPC and LVL,which was characterized by static mechanical test,creep test and water absorptivity test.The results showed that the apparent density of the WPC-wood multi-phase composite is 0.72g/cm,the 24h water absorptivity at 40℃ is 0.22%,MOR is 65MPa,MOE is 5.4GPa,50J and 75J falling impact performance is better than LVL core.To be concluded that this WPC-wood multi-composite,having better comprehensive physical performace than its components WPC shell or LVL core,is a novel composite with high strength and low density.2)WPC shell materials with different grayness were prepared by extrusion using carbon black and nano rutile titanium dioxide as colorant and inhibiter.UV accelerated aging test and characterization of the surface morphology and properties of the composites was performed,and compared with the non-colorred WPC control and the WPC containing UV absorber UV326.The results showed that the grayness of the WPC sample containing 5 percent titanium dioxide and 0.1 to 3 percent carbon black was darker with the increase of carbon black content;that the lightness index L*and color index a*and b*chaged slightly in the beginning 1000h to 2000h UV accelerating test time,then became unchanged until the end of test,time of 6000h,indicating the strong anti UV aging effectiveness of the titanium dioxide and crabon black colorant system for WPC.This may be illustrated that the colorant inhibited the surface photoxidation and further degradation of WPC,the later was proved by the following experimental facts that an increase in oxygen element content determined by XPS and IR absorption of carbonyl group determined by FTIR,and the formation of microcrack were observed on the surface of the control sample,while no significant changes were observed for the samples colored by titanium dioxide and crabon black.3)Basic production process characterized by the orthogonal mortise-tenon joint bonding and design priciples of the window made of WPC-wood multi-phase composite was put forward.Conceptual windows were made using WPC-wood multi-phase composite profiles with rectangular cross-section as frame.The design priciples of the window are as follows:(1)The mechanical and protective properties of the WPC-wood multi-phase composite must comply with the requirements of design,with the WPC shell of 3-5mm thickness,and wood core of glulam or LVL made of plantation wood,or solid wood core of straight texture;(2)On the premise of necessary fuction and decoration for the window,the cross-sectional shape and structure of WPC-wood multi-phase composite profile should be simple,less sharp edges and of good symmetry;(3)The bonding of the profle must gurantee the high bonding strength of the wood core and the good sealing property for the bonding of WPC shell,and orthogonal mortise-tenon joint bonding was preferentially recommended;(4)The structural design of WPC-wood multi-phase composite window should avoid cross joint as far as possible,use less T joint bonding;(5)Functionalization design should be performed on the basis of stablility,reliability,effectiveness,environment friendliness,and economic rationality,according to the application requirements and service environment.4)In view of the significant differences of properties,texture and color for WPC and traditional materials,a noval decorational design idea was put forward by using WPC as a brand new material taking its inherent advantage and feature,breaking through the traditional ideas for decoration of imitating solid wood.By adding carbon black,titanium dioxide or the mixture of the two with dfferent weight ratio as colorant to the formulation,three series of WPCs were prepared with the color of black,grey,and light brown,which was buitiful in color,desirable in decoration effects,and effective in anti UV aging for the samples colored by carbon black or its mixture with titanium dioxide,as was proved by the facts that the 6000h UV accelerated test did not change the appearance of the specimen.Also,new decoration and surface processing means were studed and a concept of "exchangeable shell" was put forward that the apperence of a window product could be easily changed by simply changing the detechable shell.5)The thermoperformance and carbon footprint of WPC-wood multi-phase composite window was systematically studed by comparation with windows made of aluminum,PVC plastic and solid wood respectively,using 1m2 window with the same double glazing system and frame of diferent profile material,and LCA method according the international standards of ISO 14000 series.The results showed that the U values of WPC-wood multi-phase composite window and WPC-wood frame was 1.04 Wm-2K-1 and 1.85 Wm-2K-1,respectively,being comparable to the corresponding values of wood window,and being excellent in thermal insulation.For the entire production processes of WPC-wood window frame from the initial raw materials to the window assembly shop gate,the carbon footprint value of WPC-wood window frame is 174.7 kg CO2e using virgin HDPE as plastic.The carbon footprint value of WPC-wood window frame is 137.1 kg CO2e if recycled HDPE was used,a value being closer to wood window frame which is 130.0 kg CO2e.The carbon footprint value of WPC-wood window frame could be reduced significantly if the WPC shell and the perfectly protected wood core were used as raw materials.It is concluded that WPC-wood multi-phase composite window is not only excellent in thermal insulation,but also advantageous in low carbon footprint.