Preparation And Performance Investigation Of Polysiloxane/Functionalized Graphene Composite Foam

Polysiloxane foam possesses the properties of organosilicon polymers including excellent low/high temperature resistance,radiation hardening,weather fastness and chemical stability,along with the charateristics of polymeric foams like light weight,sound-absorption,shock resistance,and etc.Graphene is an emerging two-dimentional carbon material in the 21 st century.Graphene has many advantages like large specific surface area,good thermal conductivity,high electrical conductivity and so on.In this paper,graphene and modified graphene were prepared to fabricate polysiloxane composite foams and impart polysiloxane foams improved properties.The thermal stability,electromagnetic interference shielding efficiency(EMI SE)and flameretardant property of polysiloxane composite foams were investigated.The main contents of this paper are as followed:1.Reduced graphene oxide(RGO)and mechanically exfoliated graphene(MEG)are most promising graphenes for industrial mass production.They were blended with polysiloxanes to fabricate composite foams,respectively.The structure and morphology of graphenes and the properties of composite foams were characterized,the results showed that: The average cell diameter of the composite foams filled with different graphenes decreased with the increment of filling content.Both RGO and MEG could improve the maximum degradation temperature of the second stages of TG curves.Corresponding temperatures were improved from 431.8 °C to 503.6 °C and 495.9 °C and mass ratios of residues were improved from 42.45 wt% to 55.93 wt% and 49.31 wt%,respectively.EMI SE of composite foams filled with the two types of graphenes were both improved.EMI SE of composite foam filled with 5.0 wt% MEG achieved the maximum 4.74 dB when the radiation frequency was 8.2 GHz,which means that the radiation intensity was decreased to 33.6%.2.Hexachlorocyclotriphosphazene(HCCP)and 3-aminopropyltriethoxysilane(APTS)were grafted to the surface of graphene oxide(GO)to prepare functionalized graphene oxide(FGO)which was subsequently used to fabricate polysiloxane composite foams.The structure and morphology of FGO and the properties of composite foams were characterized,the results showed that: The interlayer spacing of FGO increased from 0.72 nm to 0.82 nm,and the lamellas of FGO became more crumpled compared with GO.The average cell diameter of composite foams first increased and then decreased with increasing FGO content.FGO uniformly dispersed in polysiloxane foam matrix.The thermal stability of composite foams was markedly improved.The composite foam with 1.0 wt% FGO achieved the highest mass ratio of char residue,while the composite foam with 5.0 wt% FGO had maximum degradation temperature which was improved from 585.9 °C to 668.8 °C.LOI increased with increasing FGO content and reached the maximum 27.6%.Composite foam with 5.0 wt% FGO exhibited the best flame-retardant performance.PHRR,THR and TSP were reduced by 49.2%,14.5% and 62.2%,respectively.