Study On The Preparation And Flame Retardancy Performance Of High-Strength Reed Particleboard

To improve the comprehensive utilization rate of reed resources in Dongting Lake,Hunan Province,a substitute wood material was used to prepare particleboard,which can be used in furniture,architecture,and other fields.This alleviates the shortage of wood resources to some extent.However,the existence of a special siliceous hydrophobic layer in the reed stem epidermis makes the physical and mechanical properties of reed particleboard prepared by the industrially produced low molar ratio MUF adhesives difficult to meet the requirements of national standards.In this paper,we used polyvinyl alcohol(PVA)to modify MUF adhesives,and we obtained a PVA-modified MUF(PMUF)adhesive with good bonding properties.High-strength and flame-retardant reed particleboard was prepared by process optimization with P-MUF as adhesive and inorganic compound of aluminum hydroxide(ATH)and zinc borate(ZB)as flame retardant.We investigated the physical and mechanical properties and flame-retardant properties of the reed particleboard using scanning electron microscopy(SEM),Fourier changing infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),TG(CONE),and other characterization methods.The main conclusions are as follows:(1)A high-strength and environmentally friendly adhesive was prepared by modifying melamine-urea formaldehyde resin(MUF)with polyvinyl alcohol(PVA).We added PVA as a modifier to enhance the molecular cross-linking structure through chemical bonding,and we investigated the effects of PVA addition on the apparent properties,chemical structure,curing reaction,and thermal stability of MUF adhesives.As PVA content increased,the viscosity,solid content,and curing time of the P-MUF adhesives increased,while the content of free formaldehyde gradually decreased.The content of ether bond(C-O-C)group formed by chemical bonding between PVA and MUF adhesives also increased.As a result,the initial curing temperature of the adhesive and the enthalpy of the curing reaction decreased.However,the crystallinity and thermal stability of the P-MUF adhesives remained unchanged.(2)Preparation and properties of reed particleboard by P-MUF adhesive.The effect of PVA addition in P-MUF adhesive on the properties of reed particleboard prepared by P-MUF adhesive was studied by adjusting the amount of PVA added.The results showed that the MOR,MOE and IB of the reed particleboard prepared by P-MUF adhesive were 31.2 MPa,4093 MPa and 0.70 MPa when the better mass ratio of PVA to melamine and urea(PVA/(M+U))is 1.5:100.The mechanical properties of the board meet the requirements of the national standard GB/T 4897-2015 "Particleboard" for heavy-duty(P4)particleboard used in dry state.The formaldehyde emission of the board meets the requirements of the national standard GB/T 18580-2017 "Indoor decorating and refurbishing materials-Limit of formaldehyde emission of wood-based panels and finishing products".But the P-MUF adhesive has poor water-resistance,and the 2 h and 24 h thickness swelling(TS)of the particleboard prepared by P-MUF adhesive were 13.5%and 25.8%.The TS did not meet the requirements of the national standard GB/T 48972015.(3)Preparation and properties of high-strength reed particleboard by P-MUF adhesive.The P-MUF(PVA/(M+U)=1.5 wt.%)was used as adhesive to prepare highstrength reed particleboard.Explored the effects of board density,hot pressing temperature,hot pressing time,adhesive amount,and waterproof agent on the physical and mechanical properties of the board.The results showed that hot-pressing temperature had greatest impact on IB and 2 h TS of the particleboard,density had the greater impact on MOR of the particleboard than hot-pressing temperature,the adhesive content only had the impact on 2 h TS of the particleboard,the hot-pressing time had no significant impact on various properties of the particleboard,and the phenolic formaldehyde(PF)resin powder as waterproof agent could significantly improve the water-resistance of the particleboard.It was concluded that the optimal preparation process conditions for reed particleboard were as follows:density 0.85 g/cm3,hot-pressing temperature 160℃,hotpressing time 37.5 s/mm,adhesive content 12%and waterproof agent 5%.The MOR,MOE,IB,2 h and 24 h TS were 25.6 MPa,3592 MPa,1.25 MPa,6.3%and 14.5%,respectively.Compared with reed particleboard prepared by MUF adhesive,the IB is enhanced by 80.8%,2 h and 24 h TS are reduced by 53.3%and 43.8%,respectively.The comprehensive performance exceeds the requirements of the national standard GB/T 4897-2015 "Particleboard" for P4 type particleboard used in dry state.(4)Preparation and properties of high-strength and fire-retardant reed particleboard by P-MUF adhesive.The fire-retardant property of reed particleboard using ATH/ZB as flame retardant was invested.The results showed that the thermal property and flame retardancy of the particleboard were significantly improved with the increase of AZ content,while the physical and mechanical properties of the particleboard slightly decrease.When PF content was 5%and AZ content is 5 wt.%,the total heat release and total smoke release were reduced by 25%and 62%,the ignition time was extended from 52 s to 66 s,the CO and CO2 gas generated during combustion decrease significantly.The physical and mechanical properties of the particleboard meet the requirements of the national standard GB/T 4897-2015 "Particleboard" for P4 type particleboard used in dry state.