| Silicone rubber foam is widely used because of its dual properties of silicone rubber and foam.There are a large number of hydrocarbon groups on the side chain of the silicone,and the pore structure inside the foam has high air circulation,large specific surface area,the silicone foam will burn and decompose under high temperature or fire conditions.However,in the fields of petroleum,chemical,electronics and electrical appliances,the flame retardant requirements for foam materials are relatively high,so it is necessary to further improve the flame retardant properties of silicone foam materials.Adding a phosphorus-based flame retardant to the silicone rubber foam can improve the flame retardant efficiency,but it will invalidate the platinum-containing catalytic foaming vulcanization system and affect the preparation of the silicone rubber foam.Therefore,the microfluidic technology was used to microencapsulate the phosphorus-based DMMP flame retardant,and study the flame retardant properties of the silicone rubber foam when added DMMP microcapsules.DMMP flame retardant microcapsules can be prepared by microfluidic technology and ultraviolet curing method.The influencing factors and characteristic parameters of microcapsule were studied by microfluidic equipment,scanning electron microscope and optical microscope.The experimental results show that the diameter of flame retardant microcapsules can be controlled by the viscosity of external water phase and the flow rate of each phase within a certain range,the particle size of the microcapsules decreases with the increase of the viscosity and flow rate of the external water phase,and increases with the increase of the flow rate of the continuous phase and the disperse phase;The longer the illumination time is,the easier the microcapsule core material leaks.Hydrophilic modification of external aqueous phase is very important in the preparation of microcapsules.The DMMP microcapsules have a well-enclosed core-shell structure,smooth surface,the sphericity of more than 97%,the coefficient of variation of 8.5%,and the wall thickness uniformity of less than 50%,the thermal stability is significantly higher than DMMP.When the DMMP flame retardant microcapsules were added to silicone rubber foam,the limiting oxygen index(LOI)value increased,the heat release rate and total heat release of silicone foam decreased,and its flame retardant performance is obviously enhanced.The flame retardant microcapsules of 5 wt%,10 wt%and 15 wt%were added to silicone rubber foam respectively,and the flame retardancy was studied by means of oxygen index apparatus,cone calorimeter and scanning electron microscope.The results show that when the addition amount is 5 wt%,the LOI increases from 28.8%to 29.5%,and the vertical burning(UL-94)grade was reached V-0;When the addition amount is 15 wt%,the peak heat release rate decreases from 142.13 kW/m2 to 106.62 kW/m2,and the total heat release decreases from 48.66 MJ/m2 to 36.47 MJ/m2,the fire performance index(FPI)and fire growth index(FGI)are 0.16 m2.s/kW and 2.05 kW/m2.s,respectively.Compared with the other two additions,the silicone foam containing 15 wt%DMMP flame retardant microcapsules has the highest safety factor.The silicone rubber foam with DMMP flame retardant microcapsules has a dense and continuous carbon layer on the surface after combustion,the carbon layer contains P—O—C groups,and the surface contained carbon particles,which further reveals the condense phase flame retardant mechanism of the silicone rubber foam containing DMMP microcapsules.The paper has certain reference significance for the development of flame retardant silicone rubber foam. |
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