Research On Non-metallic Fillers To Improve The Heat Resistance Of Silicone Rubber

Due to their special structure,silicone rubber has excellent heat resistance,aging resistance and so on,which has a wide range of applications in aerospace,national defense,military and so on.However,with the development of science and technology,more requirement for the heat resistance of silicone rubber were put forward.Adding heat-resistant fillers to silicone rubber is the simplest and most effective way to improve the thermal properties of silicone rubber.The heat-resistant fillers currently added are mainly concentrated on metal fillers,but metal fillers are easily oxidized and expensive,while non-metallic fillers are not easily oxidized,are inexpensive,have low pollution,and have low toxicity.In this paper,room temperature curing silicone rubber(RTV107)was used as the matrix,and two non-metallic heat-resistant fillers were selected to study their effects on the thermal properties,thermal degradation mechanism and thermal conductivity of silicone rubber.In this paper,GO was used as a filler and GO/SR composites were prepared by solution blending.The effects of the mass fraction of GO on the mechanical properties,dielectric properties and thermal properties of the composites were studied.It was found that the addition of 1.0 wt%GO could uniformly disperse in the SR matrix.1 wt%GO/SR composites had the best mechanical properties and thermal properties.Compared with pure SR,its tensile strength and elongation at break were increased by 6%and 7%,respectively.The 5%weight loss temperature(T1)was increased by 2.2?.The dielectric properties of GO/SR composites were also improved.On this basis,four different functional reagents(N-aminoethyl-y-aminopropyl trimethoxysilane(Z6020),1H,1H,2H,2H-perfluorodecyl triethoxy silane(PDTES),3,3,3Trifluoropropyltriethoxysilane(TPTES)and polysilazane)were used to obtain four different modified GO.It was found that the composites prepared by Polysilazane-GO had the best thermal properties,and their T1 was 2.4? higher than that of GO/SR composites and 4.6? higher than pure SR.The composites prepared by PDTES-GO had the best mechanical properties,and their tensile strength and elongation at break were 15%and 17%higher than those of GO/SR composites,respectively.The composites prepared by TPTES-GO had the largest dielectric constant.On this basis,modified graphene(PG)/SR composites with different mass fractions were obtained through in-situ reduction.The effect of adding different mass fractions of PG on the thermal properties of composites was explored,and the thermal degradation mechanism of composites was investigated.It was found that the addition of PG could significantly improve the thermal properties of the composites.When the mass fraction of PG was 0.2%,the initial decomposition temperature(T1),the decomposition midpoint temperature(T2),and the final decomposition temperature(T3)of the composites were increased by 10.9,61.2 and 20.2?,respectively,compared with pure SR.The addition of PG inhibited the cleavage of the SR side methyl group and the degradation caused by the terminal Si-OH.The degradation reaction of the main chain was dominant in the whole degradation process of the composites,due to the removal of oxygen-containing functional groups on PG and the uniform dispersion of PG in the SR matrix.The thermal conductivity of the composites had also been significantly improved.Compared with pure SR,the thermal conductivity of the PG-0.2 wt%/SR composite was increased by 64.4%.Subsequently,rosin and its derivatives were selected as a filler.Naminoethyl-y-aminopropyltrimethoxysilane(Z6020)was used to modify refined rosin and maleic rosin,and two rosin-based crosslinking agents were prepared.Two series of rosin cross-linked modified SR with different mass fractions were prepared from this.It was found that SR modified with refined rosin had the best thermal properties.When the mass fraction of the refined rosin crosslinking agent(ZRO)was 3%,the T1 of SRZRO-3 wt%was 19.9?higher than that of pure SR.On this basis,refined rosin was modified with amino silicone oil to obtain amino silicone oil modified refined rosin(ARO).The effect of adding different mass fractions of ARO on the thermal properties of SR was explored,and the thermal degradation mechanism of SRARO-X was studied.It was found that when the mass fraction of ARO was 1%,the T1,T2,and T3 of SRARO-1 wt%was increased by 8.7,122.7 and 63.6?,respectively,compared with pure SR.The addition of ARO inhibited the cleavage of the SR side methyl group and the degradation caused by the terminal Si-OH.The degradation reaction of the main chain was dominant in the whole degradation process of SRARO-X.This was because the ARO containing the strong rigid hydrogenated phenanthrene ring structure uniformly dispersed in the SR.The thermal conductivity of SRARO-X had also been improved.Compared with pure SR,the thermal conductivity of SRARO-1 wt%was increased by 27.7%.