This work focused on the effect of nanocrystalline cellulose （NCC） on the curing characteristics, aging resistance and thermal stability of natural rubber （NR） reinforced with carbon black （CB）. Sharing the same...This work focused on the effect of nanocrystalline cellulose （NCC） on the curing characteristics, aging resistance and thermal stability of natural rubber （NR） reinforced with carbon black （CB）. Sharing the same fillers loading of 45 parts per hundred rubber （phr）, NR/NCC/CB composites with different NCC/CB ratios （i.e. 0/45, 5/40, 10/35, 15/30, 20/25 phr） were prepared and analyzed. Resorcinol and hexamethylene tetramine （RH）, acting as the modifier in NR/NCC interface, was also discussed for its influence. The result showed that an relatively higher ratio of NCC/CB led to a lower torque, a shorter cure time （Tg0）, a slightly longer scorch time （Ti0） and a bigger vulcanization rate constant （K）. This tendency suggested that the existence of NCC accelerated the vulcanization process. Additionally, modified by RH, NR/NCC/CB compounds exhibited a short T10 and a elevated torque. And a moderate RH content would lower the E of vulcanization. A 10 phr substitute of CB by NCC can help to improve aging resistance in terms of mechanical properties. In a high temperature aging condition, composites with 10 phr NCC also performed the highest storage modulus （G＇） among composites tested. A moderate NCC content contributed to the best retention of G＇ after high temperature aging, so did the incorporation of RH. With the partial replacement of CB by NCC, the temperature of 5% weight-lose had a slight drop and the apparent crosslink density showed a decrease. Thanks to the interaction of RH with both NR and NCC, composites showed an improvement in apparent crosslink density after modified by RH.展开更多
A novel TU derivative, N-phenyl-N＇-（γ-triethoxysilane）-propyl thiourea （STU）, is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time ...A novel TU derivative, N-phenyl-N＇-（γ-triethoxysilane）-propyl thiourea （STU）, is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl iso- thiocyanate fragment still remains in the NPUSTU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.展开更多
基金supported by the National Natural Science Foundation of China(No.51173046)National Natural Science Foundation of China Joint Fund of Guangdong Province(No.U1134005)
文摘This work focused on the effect of nanocrystalline cellulose （NCC） on the curing characteristics, aging resistance and thermal stability of natural rubber （NR） reinforced with carbon black （CB）. Sharing the same fillers loading of 45 parts per hundred rubber （phr）, NR/NCC/CB composites with different NCC/CB ratios （i.e. 0/45, 5/40, 10/35, 15/30, 20/25 phr） were prepared and analyzed. Resorcinol and hexamethylene tetramine （RH）, acting as the modifier in NR/NCC interface, was also discussed for its influence. The result showed that an relatively higher ratio of NCC/CB led to a lower torque, a shorter cure time （Tg0）, a slightly longer scorch time （Ti0） and a bigger vulcanization rate constant （K）. This tendency suggested that the existence of NCC accelerated the vulcanization process. Additionally, modified by RH, NR/NCC/CB compounds exhibited a short T10 and a elevated torque. And a moderate RH content would lower the E of vulcanization. A 10 phr substitute of CB by NCC can help to improve aging resistance in terms of mechanical properties. In a high temperature aging condition, composites with 10 phr NCC also performed the highest storage modulus （G＇） among composites tested. A moderate NCC content contributed to the best retention of G＇ after high temperature aging, so did the incorporation of RH. With the partial replacement of CB by NCC, the temperature of 5% weight-lose had a slight drop and the apparent crosslink density showed a decrease. Thanks to the interaction of RH with both NR and NCC, composites showed an improvement in apparent crosslink density after modified by RH.
基金financially supported by the National Natural Science Foundation of China(Nos.51003031 and 51303026)Science Foundation for Universities and Institutions of Dongguan City(No.2012108102008)the Research Fund for the Doctoral Program of Dongguan University of Technology(No.ZJ121002)
文摘A novel TU derivative, N-phenyl-N＇-（γ-triethoxysilane）-propyl thiourea （STU）, is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl iso- thiocyanate fragment still remains in the NPUSTU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.
