Study On Wood Fire-Retardant Coatings Based On A Synergistic Effect Of Pentaerythritol Phosphate And Guanylurea Phosphate

Intumescent water-based wood flame-retardant coatings have the advantages of simple preparation,excellent performance and environment-friendly characteristics.It can form an intumescent foam quickly on wood surface during fire,which can effectively protect the substrate and reduce the fire risk.However,the existing products are generally opaque and would cover the beautiful texture of wood.In this study,a novel aqueous transparent intumescent fire-retardant was synthesized from pentaerythritol phosphate(PEPA)and guanylurea phosphate(GUP)as fire-retardant system,melamine-urea-formaldehyde(MUF)resin as binder.The main results are given as below:(1)The PEPA did not exhibit enough solubility in the waterborne coating.In order to improve the solubility of PEPA in aqueous solution,we systematically investigated the effect of incorporation of glycol,PER and GUP.The results showed that addition glycol,PER and GUP can improve the solubility of PEPA;however,glycol and PER had negative effect on the fire retardance as evidenced by cone calorimetric analysis:1)the presence of glycol in coating resulted in light flame in 20s combustion;2)The PER restrained the intumescences of the coating during combustion;3)At 50? GUP can promote the dissolution of PEPA in aqueous solution and the resulting coating exhibited proper fire retardance;the presence of GUP can also restrain the decrease of pH value of the coating dispersion.(2)The formula was optimized according to intumescent degree,charcoal residual content,and film transmittance.The optimum ratio of GUP/PEPA was set at 1.8/1.The thermal decomposition of coating compositions was analyzed using thermogravimetry(TG).The combustion behavior of plywood uncoated(Ply-A)and coated with the prepared coating(Ply-C)and MUF(Ply-B)was tested using cone calorimetry.The surface morphologic characteristics of the residues after combustion was analyzed using scanning electron microscopy(SEM).The TG analysis showed that the flame-retardant coating had a large range of thermal weight toss,and it mainly occured between 150 and 300?,which closely matched the thermal decomposition temperature of wood(200-260?).This meaned that during the whole wood decomposition process,the gaseous products of MUF and GUP pyrolysis can be used as a gas source to exert a gas phase dilution effect.And PEPA and GUP were simultaneously used as an acid source to catalyze the dehydration and promote the carbonation of pentaerythritol and the wood surface matrix.Thus,a dense carbon layer was formed on the surface of the wood to block the transmission of heat insulation and effectively protect the substrate.The three conponents cooperated with each other in the combustion process and showed a good continuous reaction,indicating that GUP-PEPA was an effective wood flame retardant system.The cone calorimetric results indicated that the intensity of heat release rate(HRR)and smoke production rate(SPR)of Ply-C was substantially reduced compared to the Ply-A and Ply-B,suggesting an improved fire-retardancy by the prepared coating.The SEM showed that the Ply-C presented an integral,compact,and porous carbon layer on the well-protected wood char after combustion.These findings demonstrate that PEPA and GUP can be incorporated into the MUF resin to create a translucent,intumescent,and fire-retardant coating.