Effect Of Microcapsule Formaldehyde Scavenger On Formaldehyde Emission Characteristics Of Plywood

With the continuous development of China's economy and the improvement of people's living standards,people have higher requirements for the furniture and they are keen to purchase some beautiful and practical furniture.However,with the shortage of wood resources in China,natural solid wood furniture has become a scarce product,so it's replaced by wood-based panels.Urea formaldehyde resin adhesive,which is mainly used in wood-based panel,has low price and good adhesion,but it can also release free formaldehyde and other pollutants for a long time.Formaldehyde will not only pollute the environment,but also cause great harm to human body.In this thesis,formaldehyde scavenger and microcapsule technology are combined to prepare microcapsule formaldehyde scavenger with sustained-release performance.Through optimizing the preparation process of microcapsule,microcapsules with high functional core material load and excellent formaldehyde degradation effect are obtained.Finally,based on the source control of formaldehyde emission from plywood,the microencapsulated formaldehyde scavenger is applied to plywood in different loading ways.The function mechanism of microencapsulated formaldehyde scavenger in plywood formaldehyde emission control can be analyzed by testing the formaldehyde emission characteristics of plywood.(1)The microcapsules were prepared by solvent evaporation method.The morphology,loading capacity,loading efficiency and formaldehyde degradation of the microcapsules were analyzed to determine the optimal process.The results showed that the microcapsules prepared with urea as core material,ethyl cellulose as wall material,core-wall ratio of 1:1,emulsifier sodium dodecyl sulfate content of 1%had good morphology,regular spherical shape,uniform surface pore distribution,and the load:ing capacity and loading efficiency of functional core material reached 29.6%and 22.1%respectively.The formaldehyde reducing efficiency of functional core material was 45.2%in 180min.(2)The microcapsule formaldehyde scavenger was applied to plywood in two ways:veneer impregnation and adhesive mixing.At normal temperature and pressure impregnation,formaldehyde emission of Plywood treated with veneer impregnation loaded with microcapsules was 65.73%lower than that of untreated plywood,and the formaldehyde emission of plywood decreased by 70.22%after ultrasonic impregnation.However,the plywood prepared by blending adhesive method,its formaldehyde emission is reduced by 58.43%compared with untreated material.The method of veneer impregnation and loading microcapsules enables the microcapsules to capture free formaldehyde in the path of formaldehyde release by filling the natural wood conduit;The method of loading microcapsules with mixed adhesives can make the core material participate in the reaction during the hot pressing process,and control from the source of free formaldehyde.(3)In the preparation of microcapsules,the temperature sensitive material polyisopropylacrylamide(PNIPAM)was introduced to prepare the microcapsule formaldehyde scavenger with temperature sensitive response.The results show that the molecular weight of PNIPAM is more than 10000 and the volume phase transition point is 33?.When the ratio of PNIPAM to wall material is 1:2,the loading capacity and loading efficiency of core material can reach 32.82%and 59.38%respectively.At room temperature,the degradation efficiency of the microcapsule to formaldehyde can reach 36.94%,and at 40?,the degradation efficiency of the microcapsule to formaldehyde can reach 53.13%.When the temperature increases beyond the phase transition point,the hydrophobic effect of PNIPAM macromolecular chain increases,the molecular chain dehydrates and shrinks,making the surface pores of the microcapsule increase,and formaldehyde can react more fully with the core material.(4)Based on the temperature sensitive microcapsule formaldehyde scavenger,the formaldehyde emission of plywood was controlled.The formaldehyde emission of plywood changed obviously under different environmental temperature.The results showed that compared with that of plywood without microcapsules,the formaldehyde reduction efficiency of plywood at room temperature was 42.29%,29.28%,20.57%at 1d,15d,28d respectively.The formaldehyde reduction efficiency at 40?was 41.13%,25.53%,19.34%respectively.With the increase of time,the consumption of core material and aldehyde reducing efficiency will decrease.Because of the addition of microcapsules,the mechanical strength of plywood will decrease slightly,the bonding strength will decrease by 11%,the elastic modulus and static bending strength will decrease by 24.3%and 22.4%respectively.