Study On The Preparation Of Wood Fiber By NaOH Solution Treatment And Its Binder-free Bonding Mechanism

At present,traditional medium-density fiberboard is mainly produced by using low-cost urea-formaldehyde resin adhesives,but free formaldehyde is generated during the production process.Glue-free fiberboard can fundamentally solve the problem of free formaldehyde generated in fiberboard production;for no glue There are few researches on the bonding mechanism of fiberboard.Aiming at this phenomenon,this paper pretreats poplar wood chips by high-temperature and high-pressure boiling with NaOH alkali solution,and refines them to obtain wood fibers,and prepares non-glue fiberboards,and explores the most suitable pretreatment process.Through SEM,FTIR,XRD,XPS,chemical composition analysis,etc.,explore the internal mechanism of alkali-treated wood fiber on the macroscopic properties of the manufacture of non-glue fiberboard,and study the effect of alkali treatment on the energy-saving aspects of the preparation of non-glue fiberboard,and obtain the following The conclusion:(1)Wood fiber preparation process: the degree of beating and SEM results show that: wood manufactured by boiling and refining at different temperatures(150°C,180°C)and different concentrations of alkaline solutions(water,1%,3%,5%)The degree of fiber separation is close,and the alkali solution can make the fiber surface rougher.When the cooking temperature is 150°C and the concentration of the alkali solution is 1%,the hemicellulose is hydrolyzed to produce free hydroxyl groups,and the stretching vibration of the hydroxyl groups reaches the maximum,indicating that the alkali solution can produce more free hydroxyl crystallinity reduction.In summary,the best pretreatment conditions for the wood fiber preparation process are to select a cooking temperature of 150°C,an alkali solution concentration of 1%,and a cooking time of 5 minutes.(2)The prepared wood fiber is used to prepare the glueless fiberboard under the hot pressing conditions of hot pressing temperature of 180°C,hot pressing pressure of 4 MPa,and hot pressing time of 10 minutes.By measuring its physical and mechanical properties,it can be obtained that the low concentration of alkali is at150°C.Treatment can improve the physical and mechanical properties of the non-glue fiberboard.The best performance is achieved when the cooking temperature is 150 and the concentration of the alkali solution is 1%.?The specific values are elastic modulus: 4039.70 MPa,static bending strength: 19.65 MPa,internal bonding Strength: 0.58 MPa,24h water absorption thickness expansion rate: 51.36%.(3)Glue-free gluing mechanism: Under alkaline pretreatment conditions,the activation of NaOH on wood fiber is essentially as a catalyst for the reaction,promoting the degradation of hemicellulose and lignin,and generating more free active hydroxyl groups.Under the formation of various combinations,the active-OH combines into hydrogen bonds,thereby improving the physical and mechanical strength of the fiberboard.During the hot pressing process,a small amount of cellulose is degraded and the crystallinity is reduced,but the crystal form is not changed.(4)The influence of alkali treatment on the energy saving of preparing non-glue fiberboard: Under the boiling condition of 150?,the power consumption is 7.3k Wh,and increasing the cooking temperature and increasing the alkali solution concentration can reduce the energy required for preparing non-glue fiberboard.When the pretreatment condition is 150?-5%,the energy consumption for preparing the glueless fiberboard is the lowest,which is 4.2k Wh.