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Nanofiller as Vulcanizing Aid for Styrene-Butadiene Elastomer
Sahoo, N.G.,Das, C.K.,Panda, A.B.,Pramanik, P. The Polymer Society of Korea 2002 Macromolecular Research Vol.10 No.6
The use of ZnO and stearic acid is very well known in sulfenamide accelerated sulfur vulcanization of diene elastomers. Zn-ion coated nano filler has been developed and tested, in styrene-butadiene rubber (SBR) as sulfur vulcanizing activator cum reinforcing filler. In this study Zinc oxide has been replaced by the Zn-ion coated nano silica filler with an aim to study the dual role of this nanofiller in SBR. The presence of Zn-ion on the nano silica filler surface activates the sulfur vulcanization by involving Zn++ in to the sulfurating complex formed with thiazole from sulfenamide. The increase of Zn-ion, on the nanofiller, decrease the scorch safety of the elastomer compound but increase the tensile strength, state of cure and tear strength and attain maximum at its 10% level. The presence of stearic acid increases the rate of vulcanization. Replacement of stearic acid with mono-stearate, however, increases the vulcanization rate but decrease the ultimate state of cure. A mechanistic scheme involving dual function of this nanofiller has been suggested.
Structure -Properties Relations of Polypropylene/ Liquid Crystalline Polymer Blends
N.G.Sahoo,C.K.Das,HyewonJeong,Chang-SikHa 한국고분자학회 2003 Macromolecular Research Vol.11 No.5
The blends of polypropylene (PP) with glass filled thermotropic liquid crystalline polymer (LCP-g) have been prepared by melt mixing techniques at different blend ratios. The thermal, dynamic mechanical, crystalline and morphological characteristics of these blends were investigated. Higher percent crystallinity was observed for 10% level of LCP-g in the blend in comparison to that of other blend ratios. The thermal stability increased with LCP-g concentration in the blend with PP. The variation of storage modulus, stiffness and loss modulus as a function of blend ratios suggested the phase inversion at the 50% level of LCP-g in the blend. The scanning electron microscopy (SEM) photographs showed the creation of voids and destruction of the fiber structures during the dynamic mechanical measurements. Processing behavior of the blends depended on the fiber forming characteristics of LCP-g, which again varied with the molding temperatures.
Nanofiller as Crosslinker for Halogen-Containing Elastomers
Sahoo, N.G.,Kumar, E.Shiva,Das, C.K.,Panda, A.B.,Pramanik, P. The Polymer Society of Korea 2003 Macromolecular Research Vol.11 No.6
A Zn ion-coated nanosilica filler has been developed and tested, in chlorosulfonated polyethylene (CSPE) and polychloroprene (CR), as a vulcanizing activator, cum was reinforcing filler. In this study, ZnO was replaced by the Zn ion-coated nanosilica filler with an aim of studying the dual role of this nanofiller in CSPE and CR. In the case of CSPE vulcanizates, the presence of MgO deteriorated the state and rate of cure when the Zn ion-coated nanosilica filler was used, but in the case of CR it improved the state of cure and enhanced the modulus and tensile strength. The Zn ion-coated filler proved to be a better reinforcing-cum-curing agent than was externally added ZnO and NA-22 also proved to be a better curative in the presence of the Zn ion-coated nanosilica filler for both CSPE and CR.
Structure -Properties Relations of Polypropylene/ Liquid Crystalline Polymer Blends
Sahoo, N.G.,Das, C.K.,Jeong, Hye-Won,Ha, Chang-Sik The Polymer Society of Korea 2003 Macromolecular Research Vol.11 No.4
The blends of polypropylene (PP) with glass filled thermotropic liquid crystalline polymer (LCP-g) have been prepared by melt mixing techniques at different blend ratios. The thermal, dynamic mechanical, crystalline and morphological characteristics of these blends were investigated. Higher percent crystallinity was observed for 10% level of LCP-g in the blend in comparison to that of other blend ratios. The thermal stability increased with LCP-g concentration in the blend with PP. The variation of storage modulus, stiffness and loss modulus as a function of blend ratios suggested the phase inversion at the 50% level of LCP-g in the blend. The scanning electron microscopy (SEM) photographs showed the creation of voids and destruction of the fiber structures during the dynamic mechanical measurements. Processing behavior of the blends depended on the fiber forming characteristics of LCP-g, which again varied with the molding temperatures.
Foxp3 induces IL-4 gene silencing by affecting nuclear translocation of NFκB and chromatin structure
Kwon, H.K.,So, J.S.,Lee, C.G.,Sahoo, A.,Yi, H.J.,Park, J.N.,Lim, S.y.,Hwang, K.C.,Jun, C.D.,Chun, J.S.,Im, S.H. Pergamon Press 2008 Molecular immunology Vol.45 No.11
The forkhead family protein Foxp3 is a unique marker of regulatory T cells and plays a crucial role in the development and function of those cells. Ectopic expression of Foxp3 abolishes the expression of many cytokines in uncommitted cells but there is little information about whether it causes gene silencing in differentiated cells. In this study, we showed that ectopic expression of Foxp3 in primary T helper 2 cells abolished IL-4 gene expression. Foxp3 inhibited nuclear translocation of NFκB by increasing the stability of the NFκB inhibitor IκBα, which in turn reduced in vivo binding of NFκB to the IL-4 promoter region. Moreover, Foxp3 over-expression induced inactive chromatin structure by decreasing in vivo binding levels of acetylated histone 3 while increasing methylated histone 3 at lysine 9 in the IL-4 genomic locus. Our results suggest that Foxp3 could induce gene silencing by inhibiting NFκB activity and by causing its target loci to adopt an inactive chromatin configuration.