Rubber/Nanocarbon Composites: Dispersion And Interface

Nanocarbons such as graphene and carbon nanotubes, are new kinds of nanomaterialswith unprecedented physical and mechanical properties which have been utilized for thereinforcement and functionalization of rubber, offering new changes for fabricating highperformance rubber composites. Widely known, the dispersion state of nanofillers and theinterfacial interaction between filler and rubber matrix are the two crucial factors in governingthe ultimate performances of rubber composites. In this thesis, the nanocomposites consistingrubber and two kinds of nanocarbons, multi-walled carbon nanotubes (MWCNTs) andgraphene oxide (GO), were investigated with emphasis on the dispersion of nanocarbons andinterfacial interaction.First, we developed a reliable process to fabricate styrene-butadiene rubber(SBR)/MWCNTs master batch with high MWCNTs content in which homogeneousdispersion of MWCNTs was achieved. High performance and functional SBR/MWCNTscomposites were manufactured based on above master batch. Due to the effectiveimpregnation of the MWCNTs by the rubber chains, the well interfacial interaction betweenfillers and rubber matrix and the elastic resilience of rubber chains were taken advantage asdriving force for disentangling and dispersing MWCNTs in the rubber matrix duringprocessing. The tensile strength and modulus, tear strength, electrical and thermalconductivities and abrasion resistance of SBR/MWCNTs composites enhanced significantlyas the MWCNTs content increased.For further enhancing the reinforcing efficiency of MWCNTs, a sulfur-containingvulcanization accelerator tetramethyl thiuram disulfide (TMTD) was fed into theSBR/MWCNTs master batch. After that, a more intensive molding is introduced to the masterbatch which would improve the impregnation of the MWCNTs by the rubber chains.Meanwhile, TMTD would decompose to induce slightly pre-crosslinking in the matrix whichwould improve the elastic resilience of rubber chains considerably. As a result, thedisentanglement of MWCNTs clews were improved apparently and the localized alignment ofthread-like MWCNTs were achieved. The tensile strength for TMTD pre-crosslinkedSBR/MWCNT composite with about10phr MWCNT loading is excellent comparing withthe reported data. The tensile modulus, tear strength, electrical conductivity and abrasionresistance of SBR/MWCNTs composites also enhanced as the TMTD content increased.Different VPR/GO hybrids with two distinct interface types, namely ionic bondinginterfaces (HVPR) and hydrogen bonding interfaces (CaVPR) were designed and fabricated by intentionally tailoring the interfacial chemistry with different flocculants during theco-coagulation process. The chain relaxation dynamics of VPR/GO hybrids were studiedthrough dielectric relaxation spectroscopy (DRS). The result showed that the concentration ofGO had no impact on the segmental dynamics of CaVPR, but the segmental dynamics ofHVPR slowed down at1.5vol.%of GO. Meanwhile, the segmental relaxation of HVPR wasalways a little faster than its CaVPR counterpart. All hybrids exhibited a new relaxationprocess which was attributed to the restricted chains in the VPR/GO interfacial region. Theinterfacial relaxation speeded up with increasing GO content in HVPR. However, it firstdecreases and then increases with decreasing GO concentration in CaVPR. The calculatedeffective activation enthalpy and the fragility parameter were introduced to evaluate theinterfacial interaction of VPR/GO hybrids. With the same GO loading, the interfacialinteraction in HVPR was always higher than that in CaVPR which resulted in a slowerinterfacial relaxation in HVPR.