| Natural rubber has superior properties and is widely used,but the application of natural rubber is limited because of its flammability characteristics.In addition,it is also a poor conductor of heat.When natural rubber products are used under dynamic conditions,the heat generated by friction cannot be transmitted to the outside in time,so it will accumulate in the natural rubber products and form a local high temperature.As a result,the aging speed of rubber products is accelerated,and the performance is reduced,which will also make it more combustible.In order to modify the flame retardant of natural rubber,it is necessary to add flame retardant to natural rubber.Expandable graphite can provide good fire protection for all kinds of materials.However,the hydrophobicity of expanded graphite and the poor interfacial adhesion between expanded graphite and polymer lead to uneven dispersion and easy agglomeration of expanded graphite in the matrix.By encapsulating expandable graphite microadhesive,expandable graphite can be better used in flame retardant polymer.However,microencapsulation of expandable graphite will reduce the thermal conductivity of expandable graphite,which is not conducive to heat conduction,so the addition of thermal conductive materials can not only improve the thermal conductivity of expandable graphite microcapsules,but also improve the heat accumulation of natural rubber.In this paper,boron nitride high thermal conductivity expandable graphite microcapsules and carbon nanotube high thermal conductivity expandable graphite microcapsules were prepared by in-situ polymerization using boron nitride and carbon nanotubes as thermal conductive materials.Boron nitride high thermal conductivity expandable graphite microcapsules were added to natural rubber to prepare composite natural rubber,and the flame retardancy and mechanical properties of the composite rubber were studied.The results showed that the high thermal conductivity expandable graphite microcapsule added into boron nitride improved the flame retardancy of the composite rubber,and the peak heat release rate of the composite rubber was 727.57k W/m2,which was 45.06%lower than that of pure natural rubber;the highest fire performance index was 4.95×10-2m2s/k W,and the lowest fire growth rate index was 13.72k W/sm2;the lowest smoke release rate was 17.94m2/(s·m2),which was 40.42%lower than that of pure natural rubber.And the thermal conductivity is greatly improved,and the highest thermal conductivity is 0.451W/m K,which is 205%higher than that of natural rubber,and alleviates the deterioration effect of EG on the mechanical properties of composite rubber.In this paper,carbon nanotube high thermal conductivity expandable graphite microcapsules were added to natural rubber to prepare composite natural rubber,and the flame retardancy and mechanical properties of composite rubber were studied.The results showed that the high thermal conductivity expandable graphite microcapsules into carbon nanotubes improved the flame retardancy of the composite rubber,and the peak heat release rate of the composite rubber was 723.52 k W/m2,which was 45.57%lower than that of pure natural rubber.The fire performance index was the highest of5.25×10-2m2s/k W,and the lowest fire growth rate index was 12.47k W/sm2.The lowest smoke release rate was 20.52m2/sm2.The highest thermal conductivity of composite rubber is 0.46W/m K,which is more than three times that of natural rubber;and the tensile strength is 118.8%higher than that of natural rubber with unmodified expandable graphite,and the elongation at break is 23.7%higher. |
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