Research On Manufactory Technique Of Rice-Straw/wood-Fiber Composites

This project was sponsored by National Natural Science Foundation of China for 863 Program Manufactory Technology of Wood (Bamboo);'Agricultural-residues Composites.As two kinds of raw material, rice straw and wood-fiber was mixed equably to manufacture the straw-wood composite board (SCB) in this research. With polymeric methylene diphenyl diisocyanate (MDI) for rice straw and urea-formaldehyde (UF) for wood-fiber, SCB was experimentally fabricated. Mechanical properties, i.e., bending modulus (MOE) and strength (MOR), internal bond strength (IBS), and thickness swelling (TS) of SCB were tested according to GB/T11718-1999. The tested results achieved GB/T11718-1999 for medium density fiberboard (MDF). The influences of resin content, the ratio of rice straw and wood-fiber (RRB), density and hot press curve were specifically discussed.The experiment results show that the most appropriate technical conditions were as follows: hot press temperature-160℃, hot press time-30sec/mm, resin content for straw-6%, density-no less than 0.85g/cm3, mat moisture content-10% and RRB-no more than 30%. SCB showed comparative mechanical properties as expected. RRB and resin content were demonstrated to be the two most important influential factors deciding the mechanical properties and dimensional stability. Obviously, RRB was in direct proportion to MOR and MOE and inverse to TS. But the correlation between RRB and IBS is complex. RRB showed no significant impacts on the vertical density profile. Low resin content could lead to bad performance of SCB. Density of SCB was in direct proportion to the mechanical properties. However, similar to RRB, density also showed no significant impacts on the vertical density profile.Surface characteristic of rice straw and adhesive joint of raw material and adhesive were also investigated as an important part of whole research. With the help of Fourier transform infrared spectrophotometer (FTIR), Si, in the surface layers of rice straw, was detected occurring in two kinds of forms-silicon dioxide and methyl-silicone. After glue application, much active reaction was detected by FTIR at adhesive joint of MDI and rice straw than it of UF and rice straw. Aconclusion was drawn that the adhesive system of UF and rice straw was the weakest system in SCB.Economic benefit analysis was the final part in this dissertation. Finishing calculating the cost of every RRB and resin content simply, the results showed that adding wood-fiber to rice straw made the cost of rice straw board economized markedly.(32 Figures; 16 Tables)...