| Epoxidized natural rubber(ENR) is a derivative of natural rubber(NR), and has been widely used in adhesive, tire, and inner tube. However, ENR cured by traditional curing agents(such as sulphur and DCP) are susceptible to heat/oxygen due to the existence of plenty of epoxide groups, which results in the poor ageing resistance and large compression set of cured ENR. Those problems in traditional curing agents will greatly constrain the application of ENR. Therefore, exploring new crosslinking chemistry for ENR and the potential applications are of great importance in theory and practice. Our previous works had verified that unsaturated carboxylate, such as zinc acrylate(ZDA) and zinc ferulate(ZDF) can cure ENR effectively. The mechanism of the curing reaction is oxa-Michael addition reaction, and the vulcanizates exhibit good mechanical properties and excellent ageing resistance property. In this thesis, we investigated the properties of ENR cured by oxa-Michael reaction in detail. Besides, the applications of this new crosslinking system, such as shape memory elastomer and constructing sacrificial network are also explored. Specific works of this thesis are as follows:Firstly, we investigated the tunable mechanical properties, improved dispersion of silica and excellent ageing resistance property of ENR/ZDA/silica composites. ENR/ZDA、 ENR/ZDA/silica and ENR/S/silica composites were prepared by blending and hot-pressing. The tunable mechanical property of this crosslinking system under different curing time was verified by the crosslinking density、tension-recovery curves and mechanical properties of ENR/ZDA/silica composites. When compared with sulphur-cured system, the improved dispersion of silica and excellent ageing resistance property of ENR/ZDA/silica composites were revealed by DMA curves, mechanical properties, SEM and ageing resistance results.Secondly, we studied the shape memory performance of ENR/ZDF and ENR/ZDF/HNT composites. DMA results revealed that the Tg of ENR/ZDF vulcanizates were high and could be tuned in a wide temperature range just by changing the content of ZDF. The high Tg grants ENR/ZDF vulcanizates the potential of being shape memory elastomer. The measurement of shape memory performance showed that both fixing ratio and recovery ratio were higher than 95%, indicating the excellent shape memory effect. Then HNT was added to adjust the modulus of ENR/ZDF. The results demonstrated that the addition of HNT is an efficient way to tune modulus. The resultant composites also exhibited high fixing ratio and recovery ratio(higher than 91%). It is necessary to emphasize that the shape memory elastomer discussed in the thesis belongs to sustainable SMP due to that raw materials of this system, such as NR, ferulic acid(FA) and HNT, are all natural materials.Thirdly, based on the crosslinking selectivity of ZDA to ENR, we constructed a sacrificial network in commercial available SBR to efficiently enhance its mechanical properties. The data of break strength and fracture energy indicated that the mechanical properties were strikingly improved by introducing sacrificial network at small fraction. FTIR、DMA and curing curves demonstrated that sulphur-cured SBR network and ZDA-cured ENR sacrificial network coexisted in the blended rubber and sulphide-based crosslinks linked the two networks. Lastly, the stress-stain cycles and oscillatory rheological measurements verified the existence of sacrificial network. |
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