Research On The Bonding Mechanism And Tecnology Of Special Bamboo Plywood

The questions of insufficient forest resources and inferior quality exacerbates the contradiction between raw material supply and demand in the country wood industry. Taking full advantage of bamboo, making suitable technical production for bamboo board, producting the bamboo plywood with perfect performance which satisfy the human kinds of demand, alleviate the timber resources scarce pressure.They play a vital significant role not only in making up for a lack of wood and extending the application field but also in realizing efficient resources utilization.Through the experiment,this research analysed and contrasted the chemical composition of bamboo under the different conditions and the permeability of bamboo under the different sizes. According to the test indexs of plates such as thickness swell,boiling ware resistance, modulus of rupture (MOR),modulus of elasticity (MOE),wear resistance, corrosion resistance, the glue bond test,formaldehyde emission and so on,the research dicussed the effect of thermo-compression three parameters on the special bamboo plywood. At the same time, it also explored the bonding mechanism of plywood by infrared spectral analysis(FTIR) and scanning electron microscope(SEM),which had further confirmed the effect of thermo-compression three parameters on the plywood.The following conclusions were drawn:(1)The chemical compositions were determined and analysed among the Phyllostachys heterocycla cv pubescen,the bleached bamboo,the carbonized bamboo,the carbonized bamboo filaments. The results showed that: the cellulose content was biggest in three elements, which was approximately 44.08-46.88%. The hemicellulose and acid accumulator insoluble lignin contents was respectively 18.50-22.35% and 20.02-21.17%.The sequence of chemical compositions reduction rate was the hemicellulose>the cellulose>the lignin.The sequence of the chemical extractions was: 1%NaOH extraction> the hot water extraction> the cold water extraction > the benzene-alcohol extraction. The reduction rate of carbonized bamboo filaments was the biggest,whose contents of cellulose,hemicellulose,lignin,1%NaOH extraction, the cold water extraction, the hot water extraction and the benzene-alcohol extraction was 44.08%,18.50%,20.02%, 35.05%,7.76%,10.06% and 5.52%. The analysis results were helpful to the material selection of the special bamboo plywood.(2)The bamboo structural changes were observed and compared,the result showed that:after canbonizing,the cell wall was thinner,the primary twassue cell was more translucent,the cell voids increased, and fiber as well appeared the gap, which was helpful to enhances the permeability of bamboo. The observed result also indicated: the permeability of carbonized bamboo was better than raw and bleached bamboo.(3)The permeability of carbonized bamboo filaments was about 0.14%/min.It was bigger than carbonized bamboo, so the of filaments had better permeability. The sequence of permeability was: carbonized bamboo filaments>carbonized bamboo>bleached bamboo>raw bamboo. So the raw materials selection of special bamboo plywood was the carbonized bamboo filaments.(4)The impregnating technology was studied by means of the L16(45)orthogonal test, the results showed that: the sequences of four factors influencing the effluent was PF concentration→bamboo moisture→time→length..And the best experiment program was PF concentration(25%),bamboo moisture(10%),time(20min),length(100mm).(5)The hot-pressing process of the special bamboo plywood was studied by L(934)orthogonal test. The result showed that the optimal hot-pressing process was that unit pressure of 2.0MPa, temperature of 160℃, pressing time of 1.7min/mm. The hot-pressing unit pressure had an remarkable effect on the acid resistance,modulus of rupture (MOR) and modulus of elasticity (MOE) of the plywood, and had little effect on the boiling water resistance, alkali resistance, abrasive resistance and the glue bond test of the plywood.The hot-pressing time had an remarkable effect on the MOR of the plywood,and had little effect on the other property of the plywood.The hot-pressing temperature had a certain effect on the property of the plywood, but not remarkable. Summing up the above, the optimal hot-pressing process was that unit pressure of 2.0MPa, temperature of 145℃, pressing time of 1.7min/mm.(6)The microstructure changes of special bamboo plywood and bamboo were analysed by SEM. The results showed that that the better performance ,the smaller gap and the less glue in one area unit.SEM gave that the additional instruction of the plywood bonding mechanism.(7)The characters of PF and bamboo filaments were analysed by FT-IR. The results not only showed that there was a chemical reaction of the functional groups of PF with bamboo three elements.It formed the new chemical bond, so the glue curing and the structure became to be the net working structure, played the cementation. The results also showed the functional groups of bamboo were cleavaged or disappeared after carbonizing, such as "C-H","C=C","CH3","CH2","=C-O-C","C-O-C","C-O"and so on. The results provided a reasonable basis for researching the bonding mechanism of special bamboo plywood.(8)The density of the special bamboo plywood was 1.30g/cm3, which was more dense than the ordinary Bamboo-mat plywood. The special bamboo plywood was dense and the density gradient was homogeneous, which was the first distinguishing feature of the special bamboo plywood.(9) The MOR and MOE of the special bamboo plywood were 12520 MPa and 150MPa,which were about 2.50 to 2.51 times the common bamboo plywoods, which were about 5.56 to 7.52 times the particleboard for load-bearing boards for use in dry conditions,which was the second distinguishing feature of the special bamboo plywood.(10)The special bamboo plywood had good acid resistance alkali resistance, salt tolerance and rotproofness, which was the third distinguishing feature of the special bamboo plywood.