A Study On Flaking Technique And Manufacture Of Bamboo OSB

Under the fanacial support of project "Flaking Technique and Equipment Development for Bamboo Oriented Strandsboard Manufacture" from Ministry of Science and Technology, and "948" project of "Oversea-introduced Key Flaking Technique of Bamboo Oriented Strandsboard" from the State Forestry Administration, this thesis has discussed series of critical problems on the flaking technique and manufacture of bamboo oriented strandsboard (BOSB).1. The advantage of bamboo resources in China and the future development of BOSB were addressed. The key technique problems in BOSB manufacture were also analyzed. It was pointed out that bamboo flaking technique is an urgent problem to be solved. Based on the investigation on BOSB manufacture, the thesis also explored the feasibility and advantage of BOSB manufacture using Moso bamboo (Phyllostachys heterocyclacv. Pubescen). The result indicated the bright development future in BOSB manufacture using Moso bamboo resources.2. The results of bamboo flaking method indicated that according to the three sawing directions, flaking modes were latitudinal-cut flaking, longitudinal-cut flaking and cross-cut flaking. It also could be divided into six detail modes: latitudinal-cutⅠ, latitudinal -cutⅡ, longitudinal -cutⅠ, longitudinal -cutⅡ, cross -cutⅠ, and cross -cutⅡ. The quality of bamboo flaking was mainly influenced by bamboo density, bamboo moisture content, flaking thickness, and flaking direction etc. The cutting force was mainly affected by bamboo mechanical properties and cutting parameters.3. This thesis discussed the manufacture of BOSB using Moso bamboo which planted in Hunan province. The effects of various dimensional parameters of bamboo strands on BOSB panel properties were investigated. The results showed that all the BOSB properties could meet the demand of Chinese Standard. The effects of strand thickness and length variation on BOSB properties were found. The optimum size of strands was 110～120mm in length and 0.6～0.8mm in thickness.4. The effects of hot pressing temperature, hot pressing pressure and hot pressing time on the properties of BOSB were discussed in the study. When the temperature reached to 160℃, the panel had the most superior properties. Otherwise, it would decline. BOSB showed inferior properties as the pressure was lower (e.g. 2.1 or 2.3 MPa). In the case of higher pressing pressure, the panel properties were improved with increasing panel density. However, this would cause an increasing of product cost and material consumption. When the hot pressing reached to 70s/mm, the BOSB property was the best.5. The influence of adhesive and respective technique condition were examined. The interface between bamboo strands and adhesive, and the resin distribution on bamboo strands were analyzed by using SESM, FTIR.The optimum technique of using water-solubility PF to manufacture BOSB:Resin content: 6%～8% based on oven-dried weight of bamboo strands (solid content)Blending method: SprayingStrand size: length×width×thickness=110～120mm×9～15mm×0.6～0.8mmHot pressing temperature: 160℃Hot pressing pressure: 2.5 MPaHot pressing time: 70s/mmThe optimum technique of using water-solubility PMDI to manufacture BOSB:Strand moisture content: 10%Resin content: 4.5%Ratio of main adhesive: coupling agent=15:85Blending method: SprayingStrand size: length×width×thickness=110～120mm×9～15mm×0.6～0.8mmHot pressing temperature: 160℃Hot pressing pressure: 2.5MPaHot pressing time: 40s/mm6. The schematic design of BOSB chipper was proposed. Several processing problems which affect the quality of flaking and capacity of BOSB were analyzed. It was the base for design the main production equipment and facilities. Results are as follows:(1) In order to increase the utilizition value of bamboo and to optimum the manufacture process, bamboo material should be cut into a certain length and be classified before using. Poor bamboo, small bamboo and the tip-parts of bamboo were also used to produce BOSB.(2) In the system of oriented flaking, the devices for pretreatment are the key, including block cutting and classification, longitudinal breaking, inner nodes eliminating, and oriented arrangement of bamboo pieces.(3) For the realization of auto-alignment, the auto-identifying and auto-correcting systems were designed to apply in real-time testing of production line. It could be used to adjust the right position of the surface and back of bamboo pieces, and to make sure their automatic arrangement in the same direction.(4) The key problem in oriented flaking was how to fix the position of bamboo pieces when it was forced to feed orderly into chipper to avoid their moving while flaking. Another problem was how to avoid strands smash. If strands were stricken in lateral, they were easily crushed due to the lower bonding strength between bamboo fibers.(5) The schematic design of strand chipper suitable for BOSB manufacture was proposed. According to the latitudinal-cutⅠ, flaking mechanism, of outer shell was choosen, and the flaking with fixed length and thickness could be possible by floating upper press plate, fixed low press plate and fixed curved position board in the blade ring.(6) Two types of chipper knives were designed, i.e., cutting knife (type A) and scoringknife (type B) for fixed length flaking. The function of cutting knife was to cut bamboo strands from a bamboo piece. Before they were cut off, a scoring-knife was used to precut a deep groove in the bamboo peice to section the strands.(7) The feeding system of chipper consist of feed plate, press roller, spring support, and float hammering iron, feed chain blanket, feed forced roll and press spring etc to keep bamboo pieces positioning and fixing.