Study On Flame Retardancy Of Microencapsulated Ammonium Polyphosphate For Rigid Polyurethane Foam

Rigid polyurethane foam is a new type of polymer material,which has the advantages of high specific strength,good thermal insulation,good plasticity and so on.It is widely used in construction,transportation,sports,medical and other fields.However,the limit oxygen index of the polyurethane rigid foam is low.It is easy to burn and release toxic gas and limits its application.Ammonium polyphosphate is a kind of environmental friendly flame retardant with remarkable flame retardant effect,but it is easy to be affected by moisture absorption and oxidative modification.The application of microcapsule treatment is widely concerned.In this paper,we use water as foaming agent to synthesize polyurethane rigid foam.Through the comparison of the main raw materials and the related additives,the optimum formula was obtained.By in situ method and in situ polymerization were coated with aluminum hydroxide and melamine formaldehyde resin ammonium polyphosphate,and as a flame retardant is added to add to the rigid polyurethane foam,improve the flame retardant properties of rigid polyurethane foam.1)The polyurethane rigid foam was prepared by using water as foaming agent.The change of density,compressive strength and limiting oxygen index of polyurethane rigid foam was studied under different adding amount of water.The results show that with the increase of water content,the density,compressive strength,tensile strength and limiting oxygen index of the polyurethane rigid foam are decreased.2)By means of microcapsule technology,ammonium polyphosphate was used as core material,aluminum hydroxide and melamine formaldehyde resin as wall materials to prepare a new type of coating modified flame retardant ATHAPP and MFAPP.Through the SEM scanning electron microscope and EDS element analysis,the coating material of ammonium polyphosphate was determined.The solubility test showed that the solubility of ammonium polyphosphate coated with two kinds of wall materials decreased from 0.857g/100mL to 0.394g/100mL and 0.296g/100mL.Thermogravimetric analysis showed that the ammonium polyphosphate coated with microcapsules had higher thermal stability and carbon residue.3)The halogen-free flame retardant polyurethane rigid foam was prepared by using the two kinds of microcapsule ammonium polyphosphate as halogen-free flame retardant and water as foaming agent,and the limit oxygen index,UL94 vertical combustion grade and thermal weight loss of polyurethane rigid foam were tested.The experimental results show that the improved limiting oxygen index PU/ATHAPP to 25.5%;when the amount of ATHAPP was higher than 20%,through the UL-94 V-0 test,after burning the final amount of residual carbon increased to 8.1%The improved limiting oxygen index PU/MFAPP to 26.3%;when the amount of MFAPP was higher than 15%,through the UL-94 V-0 test,after burning the final amount of residual carbon was 10%.The experimental results show that both ATHAPP and MFAPP can improve the flame retardancy of polyurethane rigid foam.