Interface and mechanical properties of peroxide cured silicate nanofiber/rubber composites

Four representative rubber matrices with varying molecular polarity, such as SBR, NBR, EPDM, and CNBR were reinforced by mechanical blending with γ-(methacryloxy)proxyltrimethoxy silane (KH570) silanized natural fibrillar silicate (FS)/unmodified FS when dicumyl peroxide was used as a curing agent. The effects of the loading amount of silane coupling agent KH570 and the type of rubber matrix on the dispersion of FS as well as the FS-rubber interfacial bonding were investigated. The mechanical properties of various rubber composites filled with unmodified FS and silanized FS individually were compared. As indicated by SEM and TEM, unmodified FS showed better dispersion in polar CNBR than in nonpolar SBR, whereas the improvement of the dispersion is more for SBR after the silanization of FS, constructing a stronger filler network. Compared with unmodified FS/rubber composites, silanized FS/rubber composites exhibited a higher interphase crosslinking network as well as a lower loss factor, indicating the improvement of the FS-rubber interfacial bonding. The more the loading amount of KH570 was, the more the FS-SBR bonding was improved. Similarly, the improvement of the FS-rubber bonding was more evident in nonpolar SBR and EPDM after FS was silanized, causing the more increase in mechanical properties, relative to polar NBR and CNBR. In strong molecular polar rubber such as CNBR and NBR, the strong interfacial bonding was achieved even if FS was not silanized with KH570, so that the composites filled with unmodified FS also possessed good mechanical properties.