The effect of neodymium stearate （NdSt） synthesized by saponification method on thermal degradation and thermo-oxidative degradation of expoxidized natural rubber with 25 mol.% epoxidation （ENR25） was investigated...The effect of neodymium stearate （NdSt） synthesized by saponification method on thermal degradation and thermo-oxidative degradation of expoxidized natural rubber with 25 mol.% epoxidation （ENR25） was investigated by thermogravimetric analysis （TGA）, and the structure of ENR25 vulcanized with NdSt after thermo-oxidative decomposition was characterized using Fourier transform infared spectroscopy-attenuated total-reflectance （FTIR-ATR）. The thermal degradation kinetic parameters of ENR25 with different loadings of NdSt were determined by Coats-Redfern method. The results showed that the thermal degradation of ENR25 in nitrogen was a one-step reaction regardless of NdSt content, whereas the thermo-oxidative degradation was a multiple-step reaction. The thermal and thermo-oxidative stability of the ENR25 vulcanizates with the addition of NdSt was higher than that of pure ENR25 vulcanizates. The ENR25 vulcanizates with the incorporation of 1 phr （per hundred parts of rubber） NdSt imparted the highest activa- tion energy （E） of thermal and thermo-oxidative degradation. This could be attributed to the many unoccupied orbits in rare earth Nd, which could capture the free radicals and make the epoxide groups stable in the process of thermal and thermo-oxidative degradation for ENR25.展开更多
Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene （HIPS） with triphenyl phosphate （TPP） and novolac type epoxy resin （NE） were characterized using t...Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene （HIPS） with triphenyl phosphate （TPP） and novolac type epoxy resin （NE） were characterized using thermo-gravimetric experiment. And the flammability was determined by limited oxygen indices （LOI）. The LOI results show that TPP and NE had a good synthetic effect on the flame retardancy of HIPS. Compared with pure HIPS, the LOI values of HIPS/NE and HIPS/TPP only increased by about 5%, and the LOI value of HIPS/TPP/NE reached 42.3%, nearly 23% above that of HIPS. All materials showed one main decomposition step, as radical HIPS scission predominated during anaerobic decomposition. TPP increased the activity energy effectively while NE affected the thermal-oxidative degradation more with the help of the char formation. With both TPP and NE, the materials could have a comparable good result of both thermal and thermal-oxidative degradation, which could contribute to their effect on the flame retardancy.展开更多
This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide(CFRPI)composite for modeling of the Iong-term degradation process.The degradation behaviors we...This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide(CFRPI)composite for modeling of the Iong-term degradation process.The degradation behaviors were revealed through off-gas products analysis,and the overall kinetic interpretation was achieved from study of the mass-loss curves recorded under dynamic conditions.It was found that thermooxidative degradati on of the CFRPI composite was a multistep process,which in eluded four main reaction steps.Since most kinetic an alysis methods were derived from simple reactions described by a single kinetic triplet,they cannot be applied reliably to such a process.Therefore,we firstly separated the four overlapped reaction steps by peak fitting of derivative thermogravimetric curves using Fraser-Suzuki equation consider!ng the asymmetrical n ature of kin etic curves,and subsequently an a lyzed each in dividual reaction employing Friedma n method and experimental master-plots method.Four sets of kinetic triplets were determined to characterize the entire degradation process.The validity of four corresponding kinetic triplets was confirmed by perfect simulation of mass-loss curves recorded at both dynamic conditions used in kinetic analysis and entirely different isothermal conditions.Finally,modeling of Iong-term aging at 400°C of the CFRPI composite was successfully achieved based on these kinetic triplets.The predicted mass loss and flexural property correlated well with experimental results.This study can serve as a basis for rapid evaluation of the long-term durability of the CFRPI composite in various application environments.展开更多
基金supported by National Program on Key Basic Research Project of China(973Program,2010CB635109)Ministry of Science and Technology R&D Research Institutes(2008EG134285)supported by the Fundamental Research Funds for Rubber Research Institute,CATAS(1630022013021,1630022012013)
文摘The effect of neodymium stearate （NdSt） synthesized by saponification method on thermal degradation and thermo-oxidative degradation of expoxidized natural rubber with 25 mol.% epoxidation （ENR25） was investigated by thermogravimetric analysis （TGA）, and the structure of ENR25 vulcanized with NdSt after thermo-oxidative decomposition was characterized using Fourier transform infared spectroscopy-attenuated total-reflectance （FTIR-ATR）. The thermal degradation kinetic parameters of ENR25 with different loadings of NdSt were determined by Coats-Redfern method. The results showed that the thermal degradation of ENR25 in nitrogen was a one-step reaction regardless of NdSt content, whereas the thermo-oxidative degradation was a multiple-step reaction. The thermal and thermo-oxidative stability of the ENR25 vulcanizates with the addition of NdSt was higher than that of pure ENR25 vulcanizates. The ENR25 vulcanizates with the incorporation of 1 phr （per hundred parts of rubber） NdSt imparted the highest activa- tion energy （E） of thermal and thermo-oxidative degradation. This could be attributed to the many unoccupied orbits in rare earth Nd, which could capture the free radicals and make the epoxide groups stable in the process of thermal and thermo-oxidative degradation for ENR25.
基金Guangdong Province Natural Sciences Fundation(No.39672)
文摘Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene （HIPS） with triphenyl phosphate （TPP） and novolac type epoxy resin （NE） were characterized using thermo-gravimetric experiment. And the flammability was determined by limited oxygen indices （LOI）. The LOI results show that TPP and NE had a good synthetic effect on the flame retardancy of HIPS. Compared with pure HIPS, the LOI values of HIPS/NE and HIPS/TPP only increased by about 5%, and the LOI value of HIPS/TPP/NE reached 42.3%, nearly 23% above that of HIPS. All materials showed one main decomposition step, as radical HIPS scission predominated during anaerobic decomposition. TPP increased the activity energy effectively while NE affected the thermal-oxidative degradation more with the help of the char formation. With both TPP and NE, the materials could have a comparable good result of both thermal and thermal-oxidative degradation, which could contribute to their effect on the flame retardancy.
文摘This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide(CFRPI)composite for modeling of the Iong-term degradation process.The degradation behaviors were revealed through off-gas products analysis,and the overall kinetic interpretation was achieved from study of the mass-loss curves recorded under dynamic conditions.It was found that thermooxidative degradati on of the CFRPI composite was a multistep process,which in eluded four main reaction steps.Since most kinetic an alysis methods were derived from simple reactions described by a single kinetic triplet,they cannot be applied reliably to such a process.Therefore,we firstly separated the four overlapped reaction steps by peak fitting of derivative thermogravimetric curves using Fraser-Suzuki equation consider!ng the asymmetrical n ature of kin etic curves,and subsequently an a lyzed each in dividual reaction employing Friedma n method and experimental master-plots method.Four sets of kinetic triplets were determined to characterize the entire degradation process.The validity of four corresponding kinetic triplets was confirmed by perfect simulation of mass-loss curves recorded at both dynamic conditions used in kinetic analysis and entirely different isothermal conditions.Finally,modeling of Iong-term aging at 400°C of the CFRPI composite was successfully achieved based on these kinetic triplets.The predicted mass loss and flexural property correlated well with experimental results.This study can serve as a basis for rapid evaluation of the long-term durability of the CFRPI composite in various application environments.
