Study On The Technology Of Freeze-thaw Cycles Treated On Bamboo Based Container Floor

Today, the container industry of most concern issue in resource using is to find an alternative to instead of tropical hardwoods container flooring material. Bamboo is an environmental friendly material, can be useful in 3-5 year, with fast growing, high strength, good toughness, wear resistance, and other advantages, is a good alternative to hardwood materials. in China where has extensive and abundant bamboo resources, can help to solve resource shortages and rainforest ecology deterioration problems. As the same time bamboo based container floor is a new type of high efficient utilization of "green" floor, which in application and energy-saving reduction of wood based panel industry has a very important meaning.This paper is odd to study bamboo container flooring with bamboo-wood composite structure, primarily to research freeze-thaw cycles in bamboo processing, analysis the influence of freeze-thaw mechanisms and process factors. After freeze-thaw process, composite with eucalyptus and bamboo-wood, mats and blinds are used in surface, core is full of bamboo or eucalyptus veneer, the surface of base floor with phenol-formaldehyde resin impregnated paper overlay, using hot-pressing to make Bamboo container flooring. The technology of drying and impregnation to phenol-formaldehyde resin adhesive-related must be concerned in freeze-thaw bamboo penetration, and to optimize production process, analysis effects and characterizes of the testing. Preliminary test results showed that the freezing and thawing cycle of bamboo drying time is shortened, drying rates increased, penetration depth of impregnated phenol-formaldehyde resin increased, the penetration rate increased, dipping reduced, not only effectively shortened the production time, but also reduced production costs, in line with today’s enterprises to pursue win-win economic and benefit goals. And with a variety of characterization methods of analyzing the characteristics of raw materials after freeze-thaw cycling, with surface area Analyzer (BET), test materials before and after freeze-thawing treatment surface area, pore size and pore volume change; X-ray diffraction (XRD) analysis the crystal structure of modified wood fiber and its crystallinity; scanning electron microscopy (SEM) to observe the surface microstructure change before and after freezing and thawing; contact angle Analyzer (DSA 30) measuring surface before and after freeze-thawing treatment on the wetting properties of different solution. These paper’s main conclusions are as follows:(1) Response surface analysis shows that the effects of resin content placement order based on the size of the factors are:melting temperature> freezing time> cycle number> melting time. Four factors interactional effects are not significant to dipping, which range of values within the scope is freezing time and cycles of interaction effects on resin content most evident. By analyzing the binary regression model, within the range of values in each factors, providing an optimal process parameters for cyclic freeze-thaw:cycle 4 times, frozen 6h, melt 1.5h, melting temperature 60℃. Under the optimal conditions of freeze-thaw cycle parameters, phenol-formaldehyde adhesive resin content by this method is 10.25%.(2) In condition of optimal parameters of freeze-thaw cycles process to test bamboo’s quality, hardness and strength changes before and after freeze-thawing treatment. Then found bamboo’s quality, hardness and strength with different degrees of reduction and loss after freeze-thawing treatment. When the composite porous limit reached, the internal voids of bamboo increases and crack and connected to each other, thereby undermining the bamboo, resulting in loss of its physical and mechanical properties.(3) In condition of optimal parameters of freeze-thaw cycles process, by surface area Analyzer materials before and after freeze-thawing treatment surface area, pore size and pore size changes. After freeze-thaw process, found the surface area of bamboo changing from 0.88×10-2m2/g to 3.08×10-2m2/g, the surface area increased more than 250%. The pore volume of the bamboo from the original 1.62×10-4cm3/g increased to 2.18×10-4cm3/g, the pore volume increased 34.6%. but the average pore diameter of the bamboo from the original 73.13nm reduced to 28.31nm, the average pore reduced 61.3%. In short, the freeze-thaw cycle is benefit for bamboo’s micropore enlargement.(4) In condition of optimal parameters of freeze-thaw cycles process, by using scanning electron microscopy (SEM) to observe the surface microstructure change before and after freeze-thaw, the results revealed that by freeze-thaw treatment of bamboo, pore diameter smaller, fiber diameter of the sheath is larger. Carefully observation shows that untreated bamboo microstructure in vascular distribution of the bamboo walls of loose, irregular, transverse section close to the oval. Bamboo beam cross section and freeze-thaw cycles of its basic organization gap is evident between the thin-walled cells, larger cells, close to circular cross section shape, and after freeze-thaw cycling gel permeation effects increased.(5) In condition of optimal parameters of freeze-thaw cycles process, Use X-ray diffraction to dissect. The results showed that the bamboos before and after freeze-thaw cycle, major absorption peak did not change significantly, but with the reason of crystallinity changes small, amorphous region increases, makes the structure of loose, has a good permeability, is good for phenol-formaldehyde resin adhesive to easier penetration and chemical reactions occur, and the substrate produces better glued.(6) In condition of optimal parameters of freeze-thaw cycles process, use contact angle measurements to analysis the impact tests of different materials on the bamboo’s joint or not, different thickness of the bamboo, moisture content. Results showed that by the freeze-thaw cycle bamboo water absorption and resin content increased; distilled water over time in various locations of bamboo can completly wetting; no joint bamboo better wetting properties than joint of the bamboo, and with bamboo thickness smaller, contact angle lower than before, wettability is also good; in lower moisture relates better.(7) In optimal frozen thaw process to test bamboo, with bamboo containing water rate 40%, solid content 25%, dip lOmin, liquid temperature 30℃ to dip, control moisture content of dipping bamboo drying to 8%～12%, and with dried eucalyptus plywood glued together, control hot pressure for 4MPa, hot temperature for 150℃, hot time for 1.5min/mm, surface containing water rate for 16%, to suppress bamboo container floor. Determination of water content, density, bottom bending loads, bond strength, and transverse bending strength and modulus of elasticity, and other physical and mechanical properties. Results showed that by the freeze-thaw cycle pressed bamboo based container floor all the physical and mechanical properties are improved, in addition to density, but all of them reached the national standard requirements.(8) The stability test results showed by the freeze-thaw cycles of bamboo, eucalyptus and preparation of bamboo-wood composite base container floor, apart from the density slightly reduced, physical and mechanical properties, other performances are improved, and conform to national requirements. This means obtained by response surface model of freeze-thaw process has a very good stability, wet materials and dipping process and hot pressing process optimization scheme has a good availability and stability, setting parameters with some reference value. Under these conditions, suppressing its physical and mechanical properties of bamboo based container floor can reach the national standard, can broad the market of container floor, has a broad application prospects.