The Mechanism Research On Dry Mosaicism Of Bamboo Fiber

The high-strength gluing of wood without glue is the frontier of wood gluing.Although the theory of glue-free gluing is earlier,but the core basic theory still remains in the cementation function of hemicellulose and lignin in lignocellulosic fiber,and the wood glueless glue technology developed by this theory has the defects of insufficient joint strength,cumbersome process and low efficiency,which leads to its unindustrial application.Bamboo is a special raw material in wood fiber materials,which is between wood and grass.Therefore,writer intends to select bamboo as the research object to produce the bamboo bioboard by one step of dried hot mold-pressing chimeric,and using scanning electron microscopy,nanoindentation,micro-CT and other modern analytical techniques to reveal the mechanism of ultra-mechanical bonding and consolidation of bamboo fiber mosaic and determine the molecular bonding mechanism and the chimeric mechanism of dried bamboo fiber,and bamboo fiber bioboard has the advantages of high density,high bonding strength,water and heat resistance.The specific results are as follows:Study on physical and mechanical characteristics of bamboo fiber bioboard.The density of bamboo bioboard prepared by chimeric of dried bamboo fiber is higher than 1.0 g/cm³,and there is no fracture,delamination and damage in the whole.The cooling time is 90 min,and the bamboo fiber chimeric temperature is 170?,the prepared bamboo bioboard has a more compact surface and is not easy to crack after being subjected to force,and can withstand temperature changes.It does not crack and deform under high temperature for a long time,and the surface color is more natural and beautiful.The internal bonding strength of bamboo bioboards is about 1.5MPa,and the part is far more than 1.5 MPa.The internal bonding strength of bamboo bioboard is 2.5 and 1.87 times of the national standard of American particleboard and medium-density fiberboard,is 3.75 and 2.5 times of the national standard of Chinese particleboard and medium-density fiberboard,he internal bonding strength(1.5 MPa)of bamboo fiber bioboard is also higher than that of ordinary high-density fiberboard in China(density:>0.8 g/cm³,internal bonding strength:0.8 MPa).The micro-mechanical properties of the bamboo bioboard prepared at a bamboo fiber chiseling temperature of 170?and cooling time is 90 min achieved the best results(hardness:0.2753 GPa,elastic modulus:9.66 GPa).Moreover,it can form a dense and stable waterproof layer on the surface,and the inner fiber component can fully form chemical bonds and network hinges,effectively preventing the penetration and absorption of water,and the water absorption rate and the water absorption length expansion rate of the soaking water for 48 hours,the water absorption width expansion ratio,the water absorption thickness expansion ratio,and the water absorption volume expansion ratio are only 1.80%,0.26%,1.39%,5.42%,and 7.16%.In particular,the water absorption thickness expansion rate is much better than the national standard requirements of China/USA particleboard(8%/8%)and medium density fiberboard(10%/20%),has good waterproof performance.Sufficient temperature(170?)and cooling time(90 min)can promote the softening,riveting and inlaying of bamboo fibers to form a denser cell network structure and more chemical bonds,such as O-H?C-C?-COOR.Lignin appears to be molten at higher temperatures,acting as an adhesive,enhances the bonding between the various components of bamboo fiber.Hemicellulose binds more tightly to the surface of cellulose and connects to each other.Bamboo bioboard exhibit a higher crystallization index than untreated fibers,the chimeric of dried bamboo bioboard has significantly better thermal stability.The chimeric of dried bamboo bioboard forms more chemical bonds and more small molecular substances,such as C-N,iodide,etc.,which are decomposed by thermal decomposition to release N₂,NH₃and other non-flammable gases,and together form a cohesive phase resistance,blocking the supply of oxygen,resulting in incomplete combustion or even partial combustion,the PHRR and THR of some chimeric of dried bamboo bioboard are close to or even lower than the cold mold-pressing chimeric of dried bamboo bioboard of the same specification,PSPR and the highest CO and CO₂release rate peaks are significantly lower,and the chimeric of dried bamboo bioboard has better flame retardant potential.It is feasible to prepare bamboo bioboards by chimeric of dried bamboo fiber.Revealing the mechanism of dried chimeric of bamboo fiber bioboard.After systematic research and analysis,the bamboo fiber dry chimeric temperature is 170?and the cooling time is 90 min,which is the best bamboo bioboard preparation process.The chimeric mechanism of dried bamboo fiber is summarized as two aspects.The physical combination:in the process of dry heat molding of bamboo fiber,the bamboo fiber is softened,riveted,inlaid,and formed into a thermoplastic bond.Together,it produces a bond,and is particularly dense,and the bond between the fibers is enhanced so that the resulting fiber bundles are interwoven;the cell walls in the fiber are crushed,and the gap between the cell walls disappears,the cell walls were pierced and strengthen the interconnection;the fiber interface layer has great interconnectivity and tightness,forming a tightly bonded fiber network without gaps;lignin acts as an adhesive and enhances the composition of bamboo fiber.The combination of hemicellulose can bind more tightly to the surface of cellulose and connect with each other.More bamboo fiber components fuse with each other and completely bond with the fiber,which protects the bamboo fiber component and forms more bonding interfaces and higher fiber to volume ratio and enhanced overall three-dimensional network fiber structure.Chemical combination:the thermal degradation reaction is intensified,the total content of cellulose,hemicellulose and lignin is reduced,and a large amount of small molecular substances are formed,which is beneficial to the self-adhesive cooperation of bamboo;the number of chemical groups of bamboo bioboard is increased,forming more chemical bonds,such as hydrogen bonds,ester bonds,ether bonds,etc.,promote stronger chemical bonding and chemical structural changes between bamboo fibers and their components and form a dense interfacial layer and chemical bond;Under the joint action of water and heat,the partial hemicellulose of the amorphous zone is hydrolyzed,causing the content of cellulose crystallized area to increase significantly,the lignin becomes more complicated and solidified,and the C-C bond ratio is obviously increased,which promotes the combination of fibers and their components.After dry hot-pressing,the bamboo fiber bioboard has a dense structure,high density,water resistance and heat resistance.The fibers are intertwined and fitted with each other,and the fibers have a chemical bonding interface to form a tight bonding layer with high bonding strength.The mechanism of bamboo fiber dried chimeric was established.