Preparation Of Novel Flame Retardant And Its Application In Silicone Rubber

Organosilicon rubber,also known as organosiloxane,is a kind of elastomer with two organic groups in the main chain and two side chains.It is a semi-inorganic and non-polar elastomer with hetero-chains.It is one of the important varieties of special synthetic rubber.Compared with ordinary rubber,silicone rubber has excellent heat resistance,cold resistance,weather resistance and physiological inertia.It is widely used in aerospace,biomedical,electronic and electrical fields.Silicone rubber itself has certain flame retardant properties,but it can still burn in open fire,so it is necessary to continue to improve the flame retardant grade of silicone rubber.Diatomite(DM)is one of the important non-metallic mineral resources.Its main component is amorphous Si O 2,which has the characteristics of dense voids and can be used as an inorganic flame retardant.Because the surface of DM contains a certain amount of hydroxyl groups,it can be modified to improve the properties of DM.In this paper,diatomite was modified and compounded due to its porous and multi-hydroxyl structure,and phosphorus and nitrogen were introduced into the surface of diatomite to prepare a new type of diatomite flame retardant.In addition,the structure and properties of the flame retardant were investigated,and the flame retardant were added to silicone rubber to improve the flame retardancy of the composite.The main research contents are as follows:(1)A new flame retardant DDP@DM was prepared by esterification of carboxyl groups in [(6-oxo-6H-dibenzo [c,e] [1,2] oxophosphorus heterohexocyclic-6-yl)methyl]succinic acid(DDP)with hydroxyl groups on the surface of DM,and added to silicone rubber to prepare flame retardant composites.The structure of the composites was characterized by scanning electron microscopy(SEM),infrared spectroscopy(FTIR)and thermogravimetric analysis(TGA).The effects of the amount of flame retardant on the flame retardancy of silicone rubber were studied by cone calorimeter,vertical combustion test and limit oxygen index test.The results showed that the silicone rubber withDDP@DM owned better thermal stability and flame retardancy.The peak heat release rate(PHRR)of silicone rubber with 10 copies of DDP@DM was 24.7% lower than that of blank silicone rubber,and the total heat release(THR)was 27.5% lower.The silicone rubber with 40 copies of DDP@DM had self-extinguishing property.(2)A new flame retardant,MWCNT@DM,was prepared by self-assembly using the non-covalent interaction of hydroxyl and amino groups on the surface of hydroxyl multi-walled carbon nanotubes(MWCNT),polyethyleneimine(PEI)and DM.The flame retardant composites were prepared by adding MWCNT@DM to silicone rubber.The structure of flame retardants and composites was characterized by polarizing microscope(PLM),SEM and FTIR.The flame retardancy of composites was studied by cone calorimeter and vertical combustion test.The results showed that MWCNT@DM had better dispersion in silicone rubber than unmodified DM,and the silicone rubber with MWCNT@DM had better flame retardancy.Compared with blank silicone rubber,the PSPR of silicone rubber with 10 copies of MWCNT@DM decreased by at least 7.4% and THR by at least 6.2%.(3)The flame retardant DM/MEL was prepared by using the synergistic flame retardant effect between melamine(MEL)and DM.The flame retardant DM/MEL was added to silicone rubber.The effects of different proportions of MEL and DM on the flame retardant properties of silicone rubber were studied,and the composite material with the best flame retardant performance was obtained.The results showed that the flame retardant properties of the silicone rubber prepared by the combination of MEL and DM are better than those of the unmodified silicone rubber.The PHRR decreased by at least 15.7% and PSPR decreased by at least 15.5% when the silicone rubber was mixed with DM and MEL.The LOI increased from 21% of blank silicone rubber to 28.5% when 10 phr of DM and 20 phr of MEL were added.