Effect of rubber confined in nano-space of nanomatrix structure on the mechanical properties

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Effect of physical interaction such as entanglement on the mechanical properties was investigated, in order to elucidate the origin of outstanding mechanical properties of rubbers with nanometrix structure. The nanomatrix structure was formed by graft-copolymerization of styrene onto natural rubber in latex stage followed by coagulation of the resulting latexd; so that, the dispersoid of natural rubber of about 1 um in average diameter was well dispersed in the nanomatrix of polystyrene of 10-60 nm in thickness. The polystyrene nano-particles of about 5 nm in average diameter were dispersed in the nanomatrix, in which natural rubber existed between the polystyrene nano-particles. The effect of the polystyrene nano-particles and natural rubber present in the nanomatrix was assessed with an Anton Paar MCR 302 RheometerThe sample used in the present work is commercial high ammonia natural rubber (HANR) latex. The HANR latex was subjected to deproteinization with urea and sodium dodecyl su … More lfate in order to prepare deproteinized natural rubber (DPNR). The graft-copolymerization of styrene onto natural rubber was carried out in latex stage with tert-butyl hydroperoxide with tetra ethylene pentamine. After coagulation of the grafted latex, morphology was observed by transmission electron microscopy.The nanomatrix structure was found for graft-copolymer of DPNR and polystyrene (DPNR-graft-PS), in which the dispersoid of natural rubber of about 1 um in average diameter was well dispersed in the nanomatrix of polystyrene of 10-60 nm in thickness.Value of storage modulus of DPNR-graft-PS with the nanomatrix structure was about10-100 times as high as that of DPNR at 30 OC, whereas the value of DPNR-graft-PS with the island-matrix structure was about 1-3 times. The 10-100 times higher value of the storage moduluswas remarkable advantage of the nanomatrix structure. When the size of PS nano-particle in the nanomatrix was about 5 nm and 60 nm, value of loss tangent of the DPNR-graft-PS with the nanomatrix structure was about 0.15 and 0.08, respectively, which were independent of frequency. The frequency independent loss tangent of the DPNR-graft-PS with the nanomatrix structure was distinguished from that of DPNR, itself. Consequently, it is concluded that a novel material, which possesses frequency independent loss tangent, is prepared by densely distributed the nano-particles into the nanomatrix. Less