Study On Dielectric And Photoluminescence Properties Of Rubber/Mesoporous Silica Composites

Mesoporous material SBA-15was prepared with P123as the templateagent and K-SBA-15was prepared using1,3,5-Trimethylbenzene as theswelling agent. The morphology and structure of SBA-15and K-SBA-15were characterized by X-ray diffraction （XRD）, nitrogen adsorption-desorption and transmission electronic microscopy （TEM）. Thecharacterizations showed that SBA-15has a long term ordered mesoporousstructure and TMB has an excellent performance in swelling the poroussize and volume of SBA-15while the long term ordered mesoporousstructure was destroyed. SBA-15/NBR and K-SBA-15/NBR compositeswere prepared by blending process and the dielectric properties of thecomposites were studied. The dielectric constant and dielectric loss of theSBA-15composites were decreasing with the increasing content ofSBA-15. When the content of SBA-15was40phr, the dielectric constantand loss of the composite was decreased by16.8%å'Œ18.4%compared tothe pure NBR respectively. Compared to the SBA-15, K-SBA-15has aweaker effect on the reduction of dielectric constant and loss of NBRcomposites which might be because of the destroyed long term orderedmesoporous structure of K-SBA-15. SBA-15/Hydrogenated carboxylated acrylonitrile-butadiene（HXNBR） composites were prepared by solution mixing with Epoxy-Polyhedral Oligomeric Silsesquioxane （POSS） as the crosslinking agent.The crosslinking degree of the composites were studied which showed thatthe crosslinking degree of the composites were increasing with the Epoxy-POSS contents. The dielectric properties of the SBA-15/HXNBRcomposites were studied. The dielectric constant and loss of the compositeswere decreased as the content of SBA-15increased which might be due tothe mesoporous structure of SBA-15. As the content of SBA-15increasedto20phr, the dielectric constant and loss of SBA-15/HNBR was reducedby14.8%å'Œ8.6%compared to pure HXNBR respectively. The dielectricconstant and loss of the composites were reduced with the increasingEpoxy-POSS contents which resulted from the crosslinking effect ofEpoxy-POSS that prohibited the segment motion of the HXNBR molecules.When the content of Epoxy-POSS content was50phr, the dielectricconstant and loss of the composite was decreased by13.6%å'Œ18.6%respectively. SBA-15and Epoxy-POSS have a synergic effect on thereduction of dielectric constant and loss of HXNBR composites.Eu（Pht）₃Phen/SBA-15hybrids were prepared by solution mixing andtheir morphologies and structures were characterized by X-ray diffraction（XRD）, scanning electronic microscopy （SEM）, nitrogen adsorption-desorption and transmission electronic microscopy （TEM）. The results showed that Eu（Pht）₃Phen was successfully incorporated into the channelsand assembled onto the surface of SBA-15and the long range orderedstructure of SBA-15was preserved. The silicone rubber composites withEu（Pht）₃Phen/SBA-15hybrids were obtained by mechanical blending, andtheir morphologies and photoluminescence properties were studied. Theresults showed that the photoluminescence intensities of the compositeswith the hybrids increased as the content of the hybrids increased. Thecomposite with the hybrids showed higher photoluminescence intensityand longer lifetime compared to the silicone rubber compounded withEu（Pht）₃Phen （Eu（Pht）₃Phen/silicone rubber composite）, Eu（Pht）₃Phenand SBA-15（[Eu（Pht）₃Phen+SBA-15]/silicone rubber composite）. Judd-Ofelt theory was used to investigate the local environment of Eu3+ions inthe silicone rubber composites. The photoluminescence quantumefficiency of the silicone rubber composite with Eu（Pht）₃Phen/SBA-15hybrids was calculated to be31.0%, higher than that ofEu（Pht）₃Phen/silicone rubber composite （26.4%） and[Eu（Pht）₃Phen+SBA-15]/silicone rubber composite （25.4%）. Theenhancement in photoluminescence intensity and increase in lifetime andphotoluminescence quantum efficiency could be attributed to the rigidstructure of SBA-15which reduced the nonradiative transition rate and the improvement of the dispersion of the hybrids in the composites.