Research On Performance Improvement Of Wood Polymer Compersites By Swell-Coupling System

It was fond of people for preparing poplar wood to wood polymer composites(WPC) because of its natural features and high useful values.However,it was very difficult to adjust the price of WPC to adapt the market competition as its expensive cost and low performance. So,the main aim of the research was to improve the general property of traditional WPC by the following thoughts.(1) Using SEM,FTIR and XRD to analysis the real relationship between the performance of WPC and the inner structure,and to find the basic reason why the capability of WPC was poor,combining with the property of WPC tested.(2) The first step was to prepare excellent WPC by seeking for proper functional reagents, additives and reformative preparing ways according to the found reason of poor performance of WPC.The optimized crafts should be found in the following step.And the last work was to estimate the general properties and complex effects of improved WPC by mechanism expressing and property testing.The following conclusions were got by the corresponding test according to the above thoughts.(1) The root cause of poor performance of WPC found by SEM,FTIR and XRD was wood and polymer mixed poorly,namely vinyl monomers reacted with wood components weakly.The obvious gaps between wood and polymer induced the poor performance such as mechanical properties,thermal stabilities,chemical erosion resistant,which not brought essential improvement by mixing.And the gaps also provided channels for water and microorganism entering into wood cell wall easily to reduce the dimensional stability and preservation performance.The lower property improvement was main because of the polymer filled the wood cell lumen to retard the water and microorganism entering into the wood cell wall.(2) GMA as a coupling agent was used to improve the performance of the traditional WPC in this research.And the optimum molar ratio of GMA to MMA was confirmed to 1:5,GMA to St was 1:4,and AIBN was 0.5%;the optimum polymerization condition was 100℃and 8h.It was known by SEM that,polymer in coupling WPC was widely filled in wood interspace,and which combined wood cell wall tightly without obvious gaps.It was also known by FTIR that GMA not only reacted with wood cell wall by its epoxy groups to remove the hydroxyl groups, but also reacted with vinyl monomers through its double bonds to form polymer loading in wood cell lumen.Additional,GMA also produced equal new hydroxyl groups as reacting with wood cell wall,which reacted continuerly with the epoxy group of GMA to form polyester chains in tridimensional reticulation forms.The XRD curves also indicated that GMA reacted with wood cell wall,which resulted in the decline of the relative crystallization.(3) The mechanical performance of coupling WPC were mostly improved 0～1 times comparing with the traditional WPC,1～5 times comparing with poplar wood.The impact toughness changed from negative 20%to plus 4 times comparing with the poplar wood and the traditional WPC.The durability of coupling WPC improved 0～13 times comparing with poplar wood and 0～12 times comparing with traditional WPC.The only declining performance was thermal stability,which declined 20～30℃comparing with poplar wood,but improved 17～31℃comparing with the traditional WPC.(4) Acetone selected as a swelling solution and Ma used as a swelling agent were mixed to swell the wood cell wall.Then the Ma-wood was got after reaction.After then,GMA and vinyl monomers were together immerged into wood cell lumen.At last,the swell-coupling WPC was gained after reaction.The optimum polymerization condition was also asured as 100℃and 8h. The SEM observing pictures showed that Ma and GMA composed as swell-coupling system reacted and formed solid polymer,which filled in wood cell lumen and connected cell wall without obivious gaps.It was also known that GMA not only reacted with carboxyl groups of Ma-wood,but also reacted with the unreacted hydroxyl groups of wood and the new producing hydroxyl groups between wood and GMA.At the same time,GMA also reacted with vinyl monomers through free radical copolymerization.The formed polymer filled in wood cell lumen as the form of tridimensional reticulation.The XRD curves also indicated that the relative crystallization of swell-coupling WPC declined 9%～22%comparing with the triditional WPC.It meaned that the polymer bonded to the wood cell wall as amorphous states, which resulted the declining of the relative crystallization.(5) The testing results showed that most mechanical properties of swell-coupling WPC improved 0～3 times comparing with poplar wood and 0～1 times compared with the traditional WPC,but not all higher than the coupling WPC.The durability of swell-coupling WPC most improved 4～42 times comparing with poplar wood,and 3～40 times comparing with traditional WPC,and 1～30 times comparing with coupling WPC.The only declining performance was thermal stability,which declineed about 42℃comparing with poplar wood,and declined about 7～24℃comparing with the coupling WPC,and only improved 17～31℃comparing with the traditional WPC.