Study On The Properties Of Blending Modified Silicone Rubber Composites

In this paper,a series of high-proformance silicone rubber compound/polyolefin thermoplastic elastomer(SRC/POE)blends were prepared,and the effects of the structure of POE on the phase structure and non-isothermal crystallization behavior of SRC/POE blends were investigated systematically.Meanwhile,the influences of the phase structure of the SRC/POE blends on their properties,and the electromagnetic shielding performances and dielectric behavior of the SRC/POE blends with ionic liquid(ILs)modified multi walled carbon nanotubes(MWCNTs)were also studied.The main results are summarized as follows:1)The influence of the structure of the POE on the aggregation structure of the SRC/POE blends were investigated by DSC and SEM.It was found that the structure of the ?-olefin monomer and the ratio of two structural units of ethylene and ?-olefin in the POE were the main factors affecting the formation process of the aggregation state of the SRC/POE blends.Since the interaction between ethylene-octane copolymer and SRC matrix was stronger than ethylene-butene copolymer,the resulted SRC/ ethylene-octane blends exhibited the the bicontinuous phase structure,while SRC/ ethylene-butene blends showed the sea-island phase structure.Therefore,the mechanical properties of the materials prepared by POE 8150 and SRC were better than other systems,and their tensile strength and tear strength reached up to 6.6 MPa and 27.8 k N/m,respectively.2)A series of SRC/POE blends were prepared by changing the content of SRC,and their phase structures were analyzed by DSC.The results showed that the crystallization temperature and crystalline of POE in SRC/POE blends increased first and then decreased with the increase of SRC content.The phase structure of the SRC/POE blends changed from a bicontinuous structure to a sea-island structure with the increase of SRC content,and the surface energy increased step by step,due to the compatibility between POE and SRC significantly decreased at a high SRC content.When the content of SRC was 10wt%,the surface energy of SRC/POE blends was 11.2 m J/m2,and the tensile strength and the tear strength were 15.8 MPa and 45.6 k N/m,respectively.So the comprehensive performance was better than the pristine POE and other SRC/POE blends with different composition.3)A series of SRC/POE/ILs modified MWCNTs(MILs)electromagnetic shielding composites with different MILs content and filler network were prepared by melt blending.The surface modification mechanism of MWCNTs,as well as the phase structures,non-isothermal crystallization behaviors,dielectric behaviors,electromagnetic shielding and mechanical properties of the composites were studied.The results showed that MILs were dispersed in the silicone rubber phase,and the SRC/POE and SRC/POE/MILs composites both exhibited the bicontinuous phase structure.The dielectric loss of SRC/POE/MILs composites were gradually increased with the increment of frequency in low frequency range,due to the introduce of MILs reduced the regularity of macroscopically ordered structures of POE,which led to the significant difference of permittivity and conductivity between MILs and polymer matrix,SRC phase containing MILs and POE phase.With the increase of MILs content,the MILs conductive network and interfacial polarization of the SRC/POE/MILs composites were gradually enhanced.Benefitting from the synergy of ILs and MWCNTs,the electromagnetic interference shielding effectiveness(EMI SE)of SRC/POE/MILs composites,especially the absorption efficiency were greatly increased.When the SRC content was less,the filler network of MILs was more compact.The EMI SE of the SRC6/POE4/7.0MILs composite at 9 GHz could reach up to 22.5 d B,which was almost 24 times higher than that of the SRC6/POE4 blend.4)A series of SRC/POE-MILs dielectric composites in which MILs were dispersed in the POE phase were prepared by the control of blending process,and the aggregation structures,dielectric behaviors and mechanical properties of the composites were studied.The results exhibited that the processing technology of the composites could affect the phase structure of SRC/POE composites.The SRC6/POE4/MILs blends exhibited the bicontinuous phase structure,while the SRC8/POE2/MILs blends showed the sea-island phase structure.The regularity of macroscopically ordered structures of POE reduced with the increase of MILs content,which led to the decrease of melt crystallization ability and melting point of POE.Moreover,the dielectric constants of SRC/POE-MILs composites showed obvious dielectric polarization steps on the frequency spectra.The space charge carriers aggregated at the interface between MILs and polymer matrix,and the interfacial polarization was formed in the SRC/POE matrix.The dielectric constants of SRC8/POE2-7.0MILs and SRC6/POE4-7.0MILs composites at the frequency of 100 Hz were 99.6 and 1133,respectively,while the dielectric losses were 0.6 and 36.1,respectively,thus the dielectric properties of the composites were obviously improved.