Preparation And Properties Of Biobased Flame-retardant Coating In Wood Surface

In order to solve the flammable hazards of wood in application effectively,to alleviate the resource pressure caused by the increasing depletion of fossil materials at the same time,and to enhance the safety and environmental benefits of materials,,taking biomass raw materials and N/P flame retardants as basis in this study,constructed the thermocuring biobased flame-retardant epoxy resin cross-linking system and UV-curing waterborne biobased flame-retardant unsaturated resin cross-linking system successively,and prepared the biobased flame-retardant coating in wood surface respectively.The curing behavior,physical properties,thermal degradation and flame retardancy of the coatings were characterized and analysed,as well as the corresponding flame-retardant mechanism was preliminarily revealed.The main research contents and conclusions are as follows:（1）HCPVC was prepared from vanillin and HCCP,the chemical structure was characterized by FTIR and ¹H-NMR,and participated in constructing the thermocuring biobased flame-retardant epoxy resin cross-linking system with epoxy resin.The gradient curing conditions were 80℃for 1h,100℃for 1h and 120℃for1h in turn,taking HCPVC as the epoxy curing agent could prevent the degradation of wood properties due to the long-term high-temperature preservation effectively.The apparent activation energy（E_a）of HCPVC was 71.59k J/mol,which was close to the typical amine curing agent and had good reactivity.（2）The epoxy coating HCPVC-EP which prepared with HCPVC showed excellent hardness,adhesion,water resistance and solvent resistance,as well as the prominent flame retardancy with UL-94 V-0 and the higher LOI value of 30.7%.HCPVC-EP degraded at around 319.9℃when heated or burned,and promoted the formation of intumescent dense char layer,which prevented the effective transfer of the heat,gas or volatiles and played the role of the condensed phase,meanwhile,it released more inert gas or nonflammable volatiles,such as CO₂,which exerted dilution and quenching effects and played the role of gaseous phase.（3）The waterborne epoxy soybean oil acrylate（IAESO）and waterborne flame-retardant comonomer（IAFRC）were prepared based on the esterification of itaconic anhydride,the chemical structure was characterized by FTIR and ¹H-NMR,and constructed the UV-curing waterborne biobased flame-retardant unsaturated resin cross-linking system.The waterborne system remained stable after high-speed centrifugation and possessed excellent water dispersibility.IAESO-F10 appeared turbidity in 90 days with the best storage stability,while IAESO-F30 appeared turbidity and stratification in a short time with the worst storage stability.The addition of IAFRC endowed system with the better water dispersion due to the more hydrophilic groups,but the particle size turned into the dominant factor of the water system stability when it excess added,the oversize particles resulted in decreasing the stability and appeared turbidity and stratification quickly.（4）The glass transition temperature,hardness and solvent resistance of the waterborne biobased flame-retardant UV-curing coating decreased in turn because the double bond of IAFRC possessed low activity which reduce the crosslinking degree,but IAFRC improved the adhesion of the coating due to the hydrogen bond.The flame retardancy affected by the amount of flame retardant and the crosslinking degree of the coating,IAESO-F20 appeared the best flame retardancy with UL-94 V-0and the higher LOI value of 28.9%.The UV-curing coating with IAFRC decomposed at around 360℃when heated or burned,and promoted the formation of intumescent dense char layer,which prevented the effective transfer of heat,gas and flammable volatiles and played a key role in flame retardancy.