Study On Preparation And Properties Of Microencapsulated Red Phosphorus Halogen-free Flame Retardant Wood Plastic Composites

Recently,wood plastic composites(WPC)have become a research focus due to their advantages of water and moisture resistance,insect resistance,environmental protection,processability and recyclability.However,since both wood fiber and plastic are combustible and can generate a lot of heat when burned,which greatly limits the application field of WPC,its research on flame retardation is very important and necessary.Based on this,in this paper,silane coupling agent KH-550 modified wood flour,low density polyethylene(LDPE)and linear low density polyethylene(LLDPE)were used as the research objects,microcapsule red phosphorus(MRP)was selected as the main flame retardant,nano magnesium hydroxide(nano-MH)and aluminum hydroxide(ATH)were selected as the coeffective flame retardants,respectively,to prepare WPC particles via twin-screw secondary extrusion,and investigate the molding conditions of fire retardant WPC by injection molding process;Meanwhile,the composites were systematically investigated for melt flow rate(MFR),mechanical properties,combustion properties and thermal degradation properties.The results are as follows:(1)After the wood flour was treated by KH-550,WPC with 35%addition of wood flour could be smoothly prepared.As the addition of wood flour increased,the impact properties of the composite systems rose and the tensile properties decreased.(2)WPC of MRP/nano-MH synergistic flame retardant with 30%wood flour content were prepared by twin-screw secondary extrusion and injection molding process.When the addition of MRP was 10%,the MFR of the composite system reached 0.214g/10min,and the impact strength reached 1.83 KJ/m~2.With the increase of MRP content,the combustion and heat resistance properties of the composite system become better,and when the MRP content is 12.5%,the fire-retardant level of the composite can reach UL94 V-0.(3)WPC of MRP/ATH synergistic flame retardant with 30%wood flour content were prepared by twin-screw secondary extrusion and injection molding process.When the MRP content is 7.5%,the composites system has better processing fluidity and mechanical properties.With the increase of MRP content,the thermal decomposition temperature of the composite system gradually increases,and the thermal resistance becomes better.When the MRP content is 12.5%,the fire retardant level of the composites can reach UL94 V-0.(4)Using the Kissinger kinetic method,the activation energy was calculated to be 140k J/mol,104 k J/mol and 72 k J/mol in the first stage of thermal decomposition for composites with flame retardant free,10%MRP and 10%nano-MH flame retardant,10%MRP and 10%ATH flame retardant,respectively,and 367 k J/mol,157 k J/mol and 180k J/mol in the second stage.In the stage of thermal decomposition,the addition of MRP,nano MH or ATH can reduce the activation energy of the composite.