Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking h...Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking have better performance, such as creep resistance and thermal shock resistance than the pipes made by the other cross-linking method. Because the PEX-a pipes indicate the higher cross-link degree as compared with the other PEX pipes. In this study, the PEX-a pipes which were mixed with several stabilizers were tested to evaluate the effects on cross-link degree and the oxygen induction time. And also they are evaluated with the chlorine aqueous solution by the performance of the long-term hydrostatic pressure test and the long-term hydro dynamic pressure test. As a result, it was found that the combination of antioxidants for PEX-a pipes plays an important role to prolong the oxygen induction time without inhibiting the cross-linking. From the results of the 1H pulsed NMR measurement over the melting point of polyethylene, it was found that each peroxide PEX pipe with different antioxidant combinations indicated the different proportion and crosslink density of cross-linked region, in addition, that these pipes had the effective structure of cross-linking for the hydrostatic and hydrodynamic pressure test with the chlorine aqueous solution. Therefore, it was considered to be useful results for studies of the stricture of cross-linking of polyethylene.展开更多
The thick insulation layer of 110 kV XLPE power cables will result in the gradient changing morphology with the radius due to crosslinking process and cooling of the XLPE insulation. In this paper, the morphology of c...The thick insulation layer of 110 kV XLPE power cables will result in the gradient changing morphology with the radius due to crosslinking process and cooling of the XLPE insulation. In this paper, the morphology of cross-linked polyethylene （XLPE） insulation of 110 kV cable and the uniforming effect of the heating process on it are researched by the differential scanning calorimetry （DSC） and X-ray diffraction （WAXD）. The middle layer morphology structures of insulation produced by normal technology are of better uniform, while the crystallinity of the inner and outer layer of the insulation is lower than that of the middle one. The melting enthalpy AHm of materials displays the difference of the crystal morphologies sensitively. The difference of crystallizing morphology in different layers of the high-voltage power cable insulation can be improved by heating process. But the uniforming of morphology of the insulation by heating process requires sufficient ttanperature and time. The effect of the on-line stress-relaxation equipment used widely by cable works now should be doubted. The test results of WAXD reveal that thermal stress changes the interplanar distances in the crystal region. So the radical stress in the insulation is tensile mainly.展开更多
BACKGROUND Polyethylene(PE)particles produced by wear of the acetabular insert are thought to cause osteolysis and thereby aseptic loosening of the implant in total hip arthroplasty(THA).As highly cross-linked polyeth...BACKGROUND Polyethylene(PE)particles produced by wear of the acetabular insert are thought to cause osteolysis and thereby aseptic loosening of the implant in total hip arthroplasty(THA).As highly cross-linked polyethylene(HXLPE)is presumed to give lower wear rates,in vivo studies are needed to confirm this.AIM To compare the wear of REXPOL,a HXPLE,with conventional PE within the first five years after implantation using Roentgen stereophotogrammetric analysis(RSA).METHODS Patients were randomised to receive either a HXLPE(REXPOL)or a conventional PE insert during primary THA.RSA images were obtained directly postoperative and after 6 wk,12 wk,6 mo,12 mo,24 mo and five years.Functional outcomes were assessed using the Hip Injury and Osteoarthritis Outcome Score and Harris Hip Score at baseline and five years after surgery.RESULTS The HXLPE(REXPOL)showed less wear in the latero-medial direction.Significant wear rates of conventional PE were seen in the latero-medial and center-proximal direction and in volume and corrected volume,whereas the REXPOL did not show these outcomes over time.Improvement from baseline in functional outcome did not significantly differ.CONCLUSION Total 3D wear is less in THAs inserted with a REXPOL inlay than a conventional PE inlay after five years.This study confirms,for the first,that the REXPOL HXLPE inlay is preferred to standard PE.展开更多
In order to prepare the polyethylene materials with controlling properties,we developed two kinds of controllable cross-linking polyethylene foaming system.2,5-dimethyl-2,5-bis (tert-butyl peroxy) hexane was used as c...In order to prepare the polyethylene materials with controlling properties,we developed two kinds of controllable cross-linking polyethylene foaming system.2,5-dimethyl-2,5-bis (tert-butyl peroxy) hexane was used as cross-linking agent and TEMPO as cross-linking inhibitor,azodicarbonamide (AC) was used as foaming agent and citric acid as foaming promoter.The density,expansion ratio,cellular structure and mechanical property of these two kinds of controllable materials were studied.Experimental results show that,properties of these two kinds of materials appear similar trend:cellular size and expansion ratio are enlarged with the amount of cross-linking inhibitor or foaming promoter increasing,while density and mechanical strength appear decreasing trend.Through comparing those two material systems’ properties,cross-linking polyethelene foaming system with citric acid as foaming promoter has better properties.展开更多
Physical cross-linking by hydrogen-bonds (H-bonds), providing a good combination of application properties of thermosets and processability of thermoplastics, is a potential strategy to resolve the recycling problem o...Physical cross-linking by hydrogen-bonds (H-bonds), providing a good combination of application properties of thermosets and processability of thermoplastics, is a potential strategy to resolve the recycling problem of traditional chemically cross-linked polyethylene. However, ureidopyrimidone (UPy), the most widely used H-bonding motif, is unfavorable for large-scale industrial application due to its poor thermal stability. In this work, H-bonds cross-linked polyethylene was successfully prepared by reactive melt blending maleic anhydride grafted polyethylene (PE-g-MAH) with 3-amino-1,2,4-triazole (ATA) to form amide triazole ring-carboxylic acid units. Triazole ring can easily generate multiple H-bonds with carboxylic acid and amide. More importantly, these units are more thermal stable than UPy due to the absence of unstable urea group of UPy. The introduction of H-bonds cross-linking leads to an obvious improvement in mechanical properties and creep resistance and a good maintain in thermal properties and recyclability. Furthermore, the reinforcement effect monotonically improves with increasing the density of H-bonds. The obtained good properties are mainly attributed to largely enhanced interchain interactions induced by H-bonds cross-linking and intrinsic reversibility of H-bonds. This work develops a novel way for the simple fabrication of H-bonds cross-linked PE with high performance through reactive melt blending.展开更多
Inkjet 3D printing has potential in the additive manufacturing of electronic circuits and devices.However,inks that can be used for printing layers with T5%>300℃ or hardness>200 MPa have been rarely reported.Cy...Inkjet 3D printing has potential in the additive manufacturing of electronic circuits and devices.However,inks that can be used for printing layers with T5%>300℃ or hardness>200 MPa have been rarely reported.Cyanate ester(CE)polymers have excellent thermal stability,high strength,and low shrinkage compared to other common dielectric inks for inkjet 3D printing,but cannot be quickly shaped by ultraviolet(UV)irradiation or thermal treatment.Combining CEs with UV-curable monomers may be a possible way to accelerate crosslinking,but there are challenges from the adverse effects of the dilution of both monomers.In this study,dielectric inks with acrylate and cyanate moieties were developed.The low viscosity and surface tension of the CE precursor(Bisphenol E cyanate ester)were combined with photocurable acrylate diluent monomers and cross-linker to realize an ink suitable for inkjet 3D printing.An internal dual three-dimensional cross-linked network structure resin was prepared by a combination of photocuring and thermal curing with T5%up to 326.69℃,hardness up to 431.84 MPa,dielectric constant of 2.70 at 8 GHz,and shrinkage of 1.64%.The developed dielectric inks can be applied to the 3D printing of printed circuit boards and other electronic devices that require dielectric properties.展开更多
Three-dimensional(3D)functional graphenebased architecture with superior electrical conductivity and good mechanical strength has promising applications in energy storage and electrics.Viscoelasticity-adjustable inks ...Three-dimensional(3D)functional graphenebased architecture with superior electrical conductivity and good mechanical strength has promising applications in energy storage and electrics.Viscoelasticity-adjustable inks make it possible to achieve desired 3D architectures with interconnected and continuous interior networks by microextrusion printing.In this work,ultra-low-concentration graphene oxide(GO)inks of~15 mg·ml-1 have been obtained and demonstrated in direct 3D printing with a facile cross-linking(direct ink writing).The rheological behavior of the GO strategy by cations,which is the lowest concentration to achieve direct ink writing inks,could be adjusted from 1×10^(4) to 1×10^(5) Pa·s^(-1) with different concentrations of cations due to strong cross-linking networks between GO sheets and cations.Meanwhile,the specific strength and electrical conductivity of 3D-printed graphene architecture are notably enhanced,reaching up to 51.7×10^(3) N·m·kg^(-1)and 119 S·m^(-1),which are superior to conventional graphene aerogels.Furthermore,3D printing graphene-based architecture assembled in micro-superc apacitor exhibits excellent electrochemical performance,which can be ascribed to the effective ion transportation through the interconnected networks.The strategy demonstrated is useful in the design of complex-shaped,graphene-based architectures for scalable manufacturing of practical energy storage applications.展开更多
To investigate the effects of polyethylene glycol cross-linking on the mechanical properties, 80 porcine aortic valves were harvested, decellularized, and introduced with sulflaydryl. Then the valves were randomly ass...To investigate the effects of polyethylene glycol cross-linking on the mechanical properties, 80 porcine aortic valves were harvested, decellularized, and introduced with sulflaydryl. Then the valves were randomly assigned into 5 experimental groups and 1 control group （n=16）. For the valves in those experimental groups, branched polyethylene glycol diacrylate （PEG） of 5 different molecular weights （3.4, 8, 12, 20, 40 kDa） were synthesized and cross-linked with them respectively. The efficiency of the cross-linking was determined by measuring the amount of residual thiol group and the mechanical properties of the cross-linked valve leaflets were assessed by uni-axial planar tensile testing. The efficiency of the PEG 20 kDa group was 70.72±2.33%, obviously superior to that of the other groups （p〈0.05）. Tensile test proved that branched PEG cross-linking can significantly enhance the mechanical behaviors of the deeellularized valve leaflet and the Young＇s modulus of each group was positively correlated with the molecular weight of PEG. It was concluded that branched PEG with the molecular weight of 20 kDa can effectively cross-link the decellularized porcine aortic valves and improve their mechanical properties, which makes it a promising cross-linker that can be used in the modification of decellularized tissue engineering valves.展开更多
文摘Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking have better performance, such as creep resistance and thermal shock resistance than the pipes made by the other cross-linking method. Because the PEX-a pipes indicate the higher cross-link degree as compared with the other PEX pipes. In this study, the PEX-a pipes which were mixed with several stabilizers were tested to evaluate the effects on cross-link degree and the oxygen induction time. And also they are evaluated with the chlorine aqueous solution by the performance of the long-term hydrostatic pressure test and the long-term hydro dynamic pressure test. As a result, it was found that the combination of antioxidants for PEX-a pipes plays an important role to prolong the oxygen induction time without inhibiting the cross-linking. From the results of the 1H pulsed NMR measurement over the melting point of polyethylene, it was found that each peroxide PEX pipe with different antioxidant combinations indicated the different proportion and crosslink density of cross-linked region, in addition, that these pipes had the effective structure of cross-linking for the hydrostatic and hydrodynamic pressure test with the chlorine aqueous solution. Therefore, it was considered to be useful results for studies of the stricture of cross-linking of polyethylene.
文摘The thick insulation layer of 110 kV XLPE power cables will result in the gradient changing morphology with the radius due to crosslinking process and cooling of the XLPE insulation. In this paper, the morphology of cross-linked polyethylene （XLPE） insulation of 110 kV cable and the uniforming effect of the heating process on it are researched by the differential scanning calorimetry （DSC） and X-ray diffraction （WAXD）. The middle layer morphology structures of insulation produced by normal technology are of better uniform, while the crystallinity of the inner and outer layer of the insulation is lower than that of the middle one. The melting enthalpy AHm of materials displays the difference of the crystal morphologies sensitively. The difference of crystallizing morphology in different layers of the high-voltage power cable insulation can be improved by heating process. But the uniforming of morphology of the insulation by heating process requires sufficient ttanperature and time. The effect of the on-line stress-relaxation equipment used widely by cable works now should be doubted. The test results of WAXD reveal that thermal stress changes the interplanar distances in the crystal region. So the radical stress in the insulation is tensile mainly.
文摘BACKGROUND Polyethylene(PE)particles produced by wear of the acetabular insert are thought to cause osteolysis and thereby aseptic loosening of the implant in total hip arthroplasty(THA).As highly cross-linked polyethylene(HXLPE)is presumed to give lower wear rates,in vivo studies are needed to confirm this.AIM To compare the wear of REXPOL,a HXPLE,with conventional PE within the first five years after implantation using Roentgen stereophotogrammetric analysis(RSA).METHODS Patients were randomised to receive either a HXLPE(REXPOL)or a conventional PE insert during primary THA.RSA images were obtained directly postoperative and after 6 wk,12 wk,6 mo,12 mo,24 mo and five years.Functional outcomes were assessed using the Hip Injury and Osteoarthritis Outcome Score and Harris Hip Score at baseline and five years after surgery.RESULTS The HXLPE(REXPOL)showed less wear in the latero-medial direction.Significant wear rates of conventional PE were seen in the latero-medial and center-proximal direction and in volume and corrected volume,whereas the REXPOL did not show these outcomes over time.Improvement from baseline in functional outcome did not significantly differ.CONCLUSION Total 3D wear is less in THAs inserted with a REXPOL inlay than a conventional PE inlay after five years.This study confirms,for the first,that the REXPOL HXLPE inlay is preferred to standard PE.
基金Funded by National Natural Science Foundation of China (No.21975108)Fundamental Research Funds for the Central Universities of China (No.JUSRP121033)。
文摘In order to prepare the polyethylene materials with controlling properties,we developed two kinds of controllable cross-linking polyethylene foaming system.2,5-dimethyl-2,5-bis (tert-butyl peroxy) hexane was used as cross-linking agent and TEMPO as cross-linking inhibitor,azodicarbonamide (AC) was used as foaming agent and citric acid as foaming promoter.The density,expansion ratio,cellular structure and mechanical property of these two kinds of controllable materials were studied.Experimental results show that,properties of these two kinds of materials appear similar trend:cellular size and expansion ratio are enlarged with the amount of cross-linking inhibitor or foaming promoter increasing,while density and mechanical strength appear decreasing trend.Through comparing those two material systems’ properties,cross-linking polyethelene foaming system with citric acid as foaming promoter has better properties.
基金financially supported by the National Natural Science Foundation of China (No. 51803130)Fundamental Research Funds for Central UniversitiesChongqing University Key Laboratory of Micro/Nano Materials Engineering and Technology (No. KFJJ2005)
文摘Physical cross-linking by hydrogen-bonds (H-bonds), providing a good combination of application properties of thermosets and processability of thermoplastics, is a potential strategy to resolve the recycling problem of traditional chemically cross-linked polyethylene. However, ureidopyrimidone (UPy), the most widely used H-bonding motif, is unfavorable for large-scale industrial application due to its poor thermal stability. In this work, H-bonds cross-linked polyethylene was successfully prepared by reactive melt blending maleic anhydride grafted polyethylene (PE-g-MAH) with 3-amino-1,2,4-triazole (ATA) to form amide triazole ring-carboxylic acid units. Triazole ring can easily generate multiple H-bonds with carboxylic acid and amide. More importantly, these units are more thermal stable than UPy due to the absence of unstable urea group of UPy. The introduction of H-bonds cross-linking leads to an obvious improvement in mechanical properties and creep resistance and a good maintain in thermal properties and recyclability. Furthermore, the reinforcement effect monotonically improves with increasing the density of H-bonds. The obtained good properties are mainly attributed to largely enhanced interchain interactions induced by H-bonds cross-linking and intrinsic reversibility of H-bonds. This work develops a novel way for the simple fabrication of H-bonds cross-linked PE with high performance through reactive melt blending.
基金supported by the National Key Researchand Development Programof China(No.2022YFB4600101)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB 0470303)+2 种基金the National Natural Science Foundation of China(No.21974057)the Western Light Project of Chinese Academy of Sciences(No.xbzg-zdsy-202007)the Oasis Scholar of Shihezi University and the Central Government to Guide Local Technological Development(No.23ZYQA315).
文摘Inkjet 3D printing has potential in the additive manufacturing of electronic circuits and devices.However,inks that can be used for printing layers with T5%>300℃ or hardness>200 MPa have been rarely reported.Cyanate ester(CE)polymers have excellent thermal stability,high strength,and low shrinkage compared to other common dielectric inks for inkjet 3D printing,but cannot be quickly shaped by ultraviolet(UV)irradiation or thermal treatment.Combining CEs with UV-curable monomers may be a possible way to accelerate crosslinking,but there are challenges from the adverse effects of the dilution of both monomers.In this study,dielectric inks with acrylate and cyanate moieties were developed.The low viscosity and surface tension of the CE precursor(Bisphenol E cyanate ester)were combined with photocurable acrylate diluent monomers and cross-linker to realize an ink suitable for inkjet 3D printing.An internal dual three-dimensional cross-linked network structure resin was prepared by a combination of photocuring and thermal curing with T5%up to 326.69℃,hardness up to 431.84 MPa,dielectric constant of 2.70 at 8 GHz,and shrinkage of 1.64%.The developed dielectric inks can be applied to the 3D printing of printed circuit boards and other electronic devices that require dielectric properties.
基金financially supported by the National Natural Science Foundation of China(No.51802195)Chen Guang Scholar Project of Shanghai Education Commission(No.19CG53)。
文摘Three-dimensional(3D)functional graphenebased architecture with superior electrical conductivity and good mechanical strength has promising applications in energy storage and electrics.Viscoelasticity-adjustable inks make it possible to achieve desired 3D architectures with interconnected and continuous interior networks by microextrusion printing.In this work,ultra-low-concentration graphene oxide(GO)inks of~15 mg·ml-1 have been obtained and demonstrated in direct 3D printing with a facile cross-linking(direct ink writing).The rheological behavior of the GO strategy by cations,which is the lowest concentration to achieve direct ink writing inks,could be adjusted from 1×10^(4) to 1×10^(5) Pa·s^(-1) with different concentrations of cations due to strong cross-linking networks between GO sheets and cations.Meanwhile,the specific strength and electrical conductivity of 3D-printed graphene architecture are notably enhanced,reaching up to 51.7×10^(3) N·m·kg^(-1)and 119 S·m^(-1),which are superior to conventional graphene aerogels.Furthermore,3D printing graphene-based architecture assembled in micro-superc apacitor exhibits excellent electrochemical performance,which can be ascribed to the effective ion transportation through the interconnected networks.The strategy demonstrated is useful in the design of complex-shaped,graphene-based architectures for scalable manufacturing of practical energy storage applications.
基金funded by the National High-Technology Research and Development Program of China(863 Program)(No.2009AA03Z420)the National Natural Science Foundation of China(Nos.30872540,81400290)
文摘To investigate the effects of polyethylene glycol cross-linking on the mechanical properties, 80 porcine aortic valves were harvested, decellularized, and introduced with sulflaydryl. Then the valves were randomly assigned into 5 experimental groups and 1 control group （n=16）. For the valves in those experimental groups, branched polyethylene glycol diacrylate （PEG） of 5 different molecular weights （3.4, 8, 12, 20, 40 kDa） were synthesized and cross-linked with them respectively. The efficiency of the cross-linking was determined by measuring the amount of residual thiol group and the mechanical properties of the cross-linked valve leaflets were assessed by uni-axial planar tensile testing. The efficiency of the PEG 20 kDa group was 70.72±2.33%, obviously superior to that of the other groups （p〈0.05）. Tensile test proved that branched PEG cross-linking can significantly enhance the mechanical behaviors of the deeellularized valve leaflet and the Young＇s modulus of each group was positively correlated with the molecular weight of PEG. It was concluded that branched PEG with the molecular weight of 20 kDa can effectively cross-link the decellularized porcine aortic valves and improve their mechanical properties, which makes it a promising cross-linker that can be used in the modification of decellularized tissue engineering valves.
