Study Wood Plastic Composite For Construction Formwork

Wood-plastic composite (WPC) materials are widely used in the industries of construction formwork for its environmental protection, light weight and high strength advantages. The high proportion of wood flour could reduce manufacture cost of wood plastic construction formwork, but decreased the toughness of formwork, the formwork would be damaged easily when it was dismantled. The performance of WPC covering with Plywood formwork is excellent, but bubbles occur on the formwork surface during cementing process, which result in the decrease of overall bonding strength. And the delaminating phenomenon also emerges when the formwork is used, so that the service life of the formwork is shortened. In the present study, the performance of construction formwork with wood plastic composite was improved to solve above problems and promote the popularizing of wood plastic construction formwork.(1) The modified polyolefin elastomer A669 was introduced to improve the toughness of wood flour/high density polyethylene (WF/HDPE) composites. The results of static mechanical showed that the A669 had a significant effect on the improvement of the WF/HDPE composite toughness, and it could also maintained the rigidity of materials. XRD and DSC analysis results showed that A669 hindered the crystallization of WF/HDPE composites, which decreased the crystallization temperature and the crystallinity, while increased the grain size and the size of the diffraction surface. Thus more energy was absorbed and lost. In addition, the glass transition temperature of the WF/HDPE composite decreased after adding A669. The DMA and SEM analysis results showed that the WF/HDPE composites filled with A669 presented more viscosity characteristic, and the wiredrawing phenomenon of plastic matrix appeared on the fracture surface, which improved the toughness of the material.(2) Using the elastomer A669 to improve the toughness of WF/PP composite, the results showed that:the A669 had a significant effect on the improvement of the WF/PP composite toughness, but it reduced the rigid of composite. Three kinds of mesh (1250 mesh, 2000 mesh,3000 mesh) talcum were selected to enhance WF/PP composite and the adding amount of it was 4,6,8 and 10 parts. The results showed that:2000 mesh and 3000 mesh talcum could significantly improve the rigidity of composite, and with talcum content increasing, the elastic modulus of composite increased. The impact strength of composite increased and then decreased. When the ratio of A669 and talcum was 6:9, the toughness and rigidity of the WF/PP composite increased simultaneously, and can achieve an architectural template standard.(3) Using copolymerization PP and wood flour to fabricate composite, the weight ratio of PP and wood flour was 40:55. Comparing with ordinary PP (T30S) based wood plastic composite, copolymer PP based wood plastic composite exhibited better toughness and rigidity, the impact strength was 12.92 kJ/m2, bending modulus was 4.21 GPa, its comprehensive performance was excellent.(4) The bubble occurred during hot-pressing process of PP based wood plastic sheet of plywood formwork can be solved by adding curing agent, prolonging glue table plate cold place, adding flour to increase solid content. The new type of plywood templates presented excellent comprehensive properties could be produced by these method.(5) Analyzing the characteristics and the cost of ordinary PP based wood plastic building templates, copolymerization PP based wood plastic building template and PP plywood formwork of wood plastic coated surface, the results indicated that the impact strength and bending modulus of the ordinary PP based wood plastic building template could be improved through adding elastomer A669 and talcum compound and the cost was in the middle; Copolymer PP based wood plastic building template showed excellent performance, the technology of it was also simple, but the cost was the highest; the performance of wood plastic covering plywood formwork was the best, and the raw material cost was also the lowest.