With the increasing application of electric and electronic devices in space and nuclear power stations, the polymeric insulation materials are inevitably exposed to various kinds of environments. Accordingly, it becom...With the increasing application of electric and electronic devices in space and nuclear power stations, the polymeric insulation materials are inevitably exposed to various kinds of environments. Accordingly, it becomes necessary to investigate the effects of the radiation and air pressure on insulation materials. This paper describes the effects of gamma-ray irradiation and reduced pressure on dielectric breakdown of polybutylene naphthalate (PBN) and polybutylene terephthalate (PBT) by applying a DC pulse voltage. Both PBN and PBT were irradiated in air up to 100 kGy and then up to 1 000 kGy with a dose rate of 10 kGy/h by using a60Co gamma-source. The effects of total dose and reduced pressure on the time to dielectric breakdown and discharge quantity were discussed. Obtained results show that, while increasing the total dose, the discharge quantity decreased with PBN, but increased with PBT. With decreasing the air pressure, the discharge quantity increased with PBN, but decreased with PBT. With increasing the total dose, the time to dielectric breakdown increased with PBN, but decreased with PBT. With decreasing the air pressure, the time to dielectric breakdown increased with both PBN and PBT. The experimental results suggest that the chemical structure of polybutylene polymers plays a main role in the result of radiation reaction, which is related to cross-linking and degradation reaction.展开更多
Studied influence of γ-irradiation on stucturation in butadiene nitrile rubber solution and films properties studied also. Structuration in solutions has defined by rheological method with rotation viscometer. Shown ...Studied influence of γ-irradiation on stucturation in butadiene nitrile rubber solution and films properties studied also. Structuration in solutions has defined by rheological method with rotation viscometer. Shown influence of solvent nature (methyl ethyl ketene: toluene) to strength properties and structures of films obtained from this solvents. It has been found that during irradiation of solvent, films and butadiene nitrile rubber solution characteristic viscosity η increased, increasing of Huggins constant (К') observed as well. Changing of spatial mesh of polymers occurs at the cost of changed size of macromolecule balls. Shown, that in the issue of crossing the properties including thermo dynamical features of films and butadiene nitrile rubber solution has changed.展开更多
Compared with non-cross-linked and dynamically covalent polymers,covalently cross-linked networks are irreplaceableinmany areas;however,they aredifficult to repair once fractured,due to limited polymer chain diffusion...Compared with non-cross-linked and dynamically covalent polymers,covalently cross-linked networks are irreplaceableinmany areas;however,they aredifficult to repair once fractured,due to limited polymer chain diffusion after cross-linking.Herein,the authors have reported a newkind of permanently cross-linked polyolefin,which when attached with amide side groups,yieldmechanically robust yet readily repairablematerials.A key is to use low cross-linking density,which enables satisfactory elasticity and chain mobility for thermodynamically favored healing.Another key is to incorporate dense hydrogen bonds that can undergo reversible associations.These factors jointly promise polyolefin networks with good mechanical properties and self-healing performance(recovered spontaneously up to 96%of its original tensile strength).More importantly,by means of mechanochemiluminescence from 1,2-dioxetane,which serves as the cross-linker and built-in self-reporting stress probe,a microscopic evaluation of how the chain entanglement proceeds upon healing and how failure occurs in the network can be obtained.展开更多
Natural rubber latex （NRL） and methyl methacrylate （MMA） grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The tens...Natural rubber latex （NRL） and methyl methacrylate （MMA） grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The tensile properties, swelling ratio and permanent set were measured. The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy. Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose. Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends. The decreasing trend of permanent set is high up to 5 kGy absorbed dose, and beyond that dose, it becomes almost flat.展开更多
基金Supported bythe Doctoral Foundation of Education Ministry of China (No.20040056037) .
文摘With the increasing application of electric and electronic devices in space and nuclear power stations, the polymeric insulation materials are inevitably exposed to various kinds of environments. Accordingly, it becomes necessary to investigate the effects of the radiation and air pressure on insulation materials. This paper describes the effects of gamma-ray irradiation and reduced pressure on dielectric breakdown of polybutylene naphthalate (PBN) and polybutylene terephthalate (PBT) by applying a DC pulse voltage. Both PBN and PBT were irradiated in air up to 100 kGy and then up to 1 000 kGy with a dose rate of 10 kGy/h by using a60Co gamma-source. The effects of total dose and reduced pressure on the time to dielectric breakdown and discharge quantity were discussed. Obtained results show that, while increasing the total dose, the discharge quantity decreased with PBN, but increased with PBT. With decreasing the air pressure, the discharge quantity increased with PBN, but decreased with PBT. With increasing the total dose, the time to dielectric breakdown increased with PBN, but decreased with PBT. With decreasing the air pressure, the time to dielectric breakdown increased with both PBN and PBT. The experimental results suggest that the chemical structure of polybutylene polymers plays a main role in the result of radiation reaction, which is related to cross-linking and degradation reaction.
文摘Studied influence of γ-irradiation on stucturation in butadiene nitrile rubber solution and films properties studied also. Structuration in solutions has defined by rheological method with rotation viscometer. Shown influence of solvent nature (methyl ethyl ketene: toluene) to strength properties and structures of films obtained from this solvents. It has been found that during irradiation of solvent, films and butadiene nitrile rubber solution characteristic viscosity η increased, increasing of Huggins constant (К') observed as well. Changing of spatial mesh of polymers occurs at the cost of changed size of macromolecule balls. Shown, that in the issue of crossing the properties including thermo dynamical features of films and butadiene nitrile rubber solution has changed.
基金This research was made possible as a result of a generous grant from the National Key Research and Development Program of China(grant nos.2017YFA0207800 and 2017YFA0204503)the National Natural Science Foundation of China(grant nos.21975178 and 21734006).
文摘Compared with non-cross-linked and dynamically covalent polymers,covalently cross-linked networks are irreplaceableinmany areas;however,they aredifficult to repair once fractured,due to limited polymer chain diffusion after cross-linking.Herein,the authors have reported a newkind of permanently cross-linked polyolefin,which when attached with amide side groups,yieldmechanically robust yet readily repairablematerials.A key is to use low cross-linking density,which enables satisfactory elasticity and chain mobility for thermodynamically favored healing.Another key is to incorporate dense hydrogen bonds that can undergo reversible associations.These factors jointly promise polyolefin networks with good mechanical properties and self-healing performance(recovered spontaneously up to 96%of its original tensile strength).More importantly,by means of mechanochemiluminescence from 1,2-dioxetane,which serves as the cross-linker and built-in self-reporting stress probe,a microscopic evaluation of how the chain entanglement proceeds upon healing and how failure occurs in the network can be obtained.
文摘Natural rubber latex （NRL） and methyl methacrylate （MMA） grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The tensile properties, swelling ratio and permanent set were measured. The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy. Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose. Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends. The decreasing trend of permanent set is high up to 5 kGy absorbed dose, and beyond that dose, it becomes almost flat.
