Preparation And Performance Of High Compressive Strength Flame-retardant Rigid Melamine Foam Materials

Melamine foam materials exhibit excellent properties with flame retardance,good thermal stability and self-extinguish.Therefore,melamine foam materials used widely in building materials to reduce the fire accidents.However,the melamine foam materials prepared by traditional methods have disadvantages with large water absorption ratio and low compressive strength,which failed to meet the more advanced demands,such as exterior building wall.In this paper,a kind of rigid melamine foam materials with low water absorption ratio,high flame retardance and high compressive strength is prepared.The main contents are described as following.Modified melamine resin prepolymer was prepared with tripolycyanamide,formalin and paraformaldehyde as main materials,methenamine as pH regulator and trimethylolpropane as modifier.Water dropping test was performed to monitor the completion of as-prepared prepolymer.The effects of the proportion of tripolycyanamide and formaldehyde,pH regulators dosage,reaction temperature and reaction time on the synthesis of melamine resin prepolymer had been investigated,and the effects of viscosity of prepolymer,proportion of paraformaldehyde,the amount of modifiers on apparent density,water absorption ratio and compressive strength of melamine foam were studied.The results showed that the most appropriate conditions to prepare prepolymer of melamine foam suitable for foaming were as followed:the proportion of tripolycyanamide and formaldehyde is 1:3,formaldehyde solution is completely replaced by paraformaldehyde,dissolving for 50 min at 55 ℃,then adding 1 wt%methenamine,5 wt%trimethylolpropane based on the mass of tripolycyanamide as benchmark,and polymerizing for 40 min at 85 ℃.When the viscosity of the prepolymer was 10-15 Pa s,the prepared melamine foam showed good comprehensive performance.The orthogonal experiment with five factors and five levels is designed using OP-10(alkylphenol ethoxylates)and sodium dodecyl sulfate as the composite emulsifier,polydimethylsiloxane as the foam stabilizer,petroleum ether as the foaming agent,concentrated hydrochloric acid as the catalyst.The effects of the amount of emulsifier,foam stabilizer,foaming agent and catalyst on the apparent density,water absorption ratio,compressive strength and limiting oxygen index of melamine foam were investigated.The flame-retardant modifiers,such as boric acid,starch,oxalic acid and citric acid,which add to the modified melamine resin prepolymer,can further improve the performance of melamine foam.The results showed that when adding 3.64 wt%OP-10,0.48 wt%sodium dodecyl sulfate,3.00 wt%polydimethylsiloxane,2.10 wt%petroleum ether,4.00 wt%hydrochloric acid and 10.00 wt%citric acid based on the mass of prepolymer of modified melamine resin as benchmark,the melamine foam possessed the best comprehensive performance with apparent density of 108 kg·m-3,water absorption ratio of 21%,compressive strength of 258.0kPa,residual carbon rate of 12.94%and limiting oxygen index of 34.3%.