In order to predict the storage life of a certain type of HTPB(hydroyl-terminated polybutadiene)coating at 25℃ and analyze the influence of pre-strain on the storage life,the accelerated aging tests of HTPB coating a...In order to predict the storage life of a certain type of HTPB(hydroyl-terminated polybutadiene)coating at 25℃ and analyze the influence of pre-strain on the storage life,the accelerated aging tests of HTPB coating at 40℃,50℃,60℃,70℃ with the pre-strain of 0%,3%,6%,9%,respectively were carried out.The variation regularity of the change of crosslinking density was analyzed and the aging model of HTPB coating under pre-strained thermally-accelerated aging was proposed.The storage life of HTPB coating at 25℃ was estimated by using the Berthelot equation as the end point of the aging life with a 30% decrease in maximum elongation.The results showed that the change of crosslinking density of HTPB coating increased with the increase of aging temperature and aging time,and decreased with the increase of pre-strain.Under 0% prestrain,the relationship between the change of crosslinking density of HTPB coating and the aging time can be described by the logarithmic model with the confidence probability greater than 99%.The stress relaxation phenomenon existed under 3%,6%and 9%pre-strained aging.The aging model considering chemical aging and pre-strain was established with the confidence probability greater than 90%.The storage life of HTPB coating was 15.2935 years at 25C under 0% prestrain,which was reduced by 13.9007%,75.6949% and 89.7859% under 3%,6% and 9% pre-strain,respectively.The existence of pre-strain has a serious impact on the storage life of HTPB coating,therefore,the pre-strain should be avoided as much as possible during the actual storage.展开更多
Control crosslink network and chain connectivity are essential to develop shape memory polymers(SMPs)with high shape memory capabilities,adjustable response temperature,and satisfying mechanistical properties.In this ...Control crosslink network and chain connectivity are essential to develop shape memory polymers(SMPs)with high shape memory capabilities,adjustable response temperature,and satisfying mechanistical properties.In this study,novel poly(ε-caprolactone)(PCL)-poly(2-vinyl)ethylene glycol(PVEG)copolymers bearing multi-pendant vinyl groups is synthesized by branched-selective allylic etherification polymerization of vinylethylene carbonate(VEC)with linear and tetra-arm PCLs under a synergistic catalysis of palladium complex and boron reagent.Facile thiol-ene photo-click reaction of PCL-PVEG copolymers with multifunctional thiols can rapidly access a serious crosslinked SMPs with high shape memory performance.The thermal properties,mechanical properties and response temperature of the obtained SMPs are tunable by the variation of PCL prepolymers,vinyl contents and functionality of thiols.Moreover,high elastic modulus in the rubbery plateau region can be maintained effectively owing to high-density topological networks of the PCL materials.In addition,the utility of the present SMPs is further demonstrated by the post-functionalization via thiol-ene photo-click chemistry.展开更多
The intrinsic volume changes(about 300%)of Si anode during the lithiation/delithiation leads to the serious degradation of battery performance despite of theoretical capacity of 3579 mAh g^(-1) of Si.Herein,a three-di...The intrinsic volume changes(about 300%)of Si anode during the lithiation/delithiation leads to the serious degradation of battery performance despite of theoretical capacity of 3579 mAh g^(-1) of Si.Herein,a three-dimensional(3D)conductive polymer binder with adjustable crosslinking density has been designed by employing citric acid(CA)as a crosslinker between the carboxymethyl cellulose(CMC)and the poly(3,4-ethylenedioxythiophene)poly-(styrene-4-sulfonate)(PEDOT:PSS)to stabilize Si anode.By adjusting the crosslinking density,the binder can achieve a balance between rigidity and flexibility to adapt the volume expansion upon lithiation and reversible volume recovery after delithiation of Si.Therefore,Si/CMC-CA-PEDOT:PSS(Si/CCP)electrode demonstrates an excellent performance with high capacities of 2792.3 mAh g^(-1) at 0.5 A g^(-1) and a high area capacity above 2.6 mAh cm^(-2) under Si loading of 1.38 mg cm^(-2).The full cell Si/CCP paired with Li(Ni_(0.8)Co_(0.1)Mn_(0.1))O_(2) cathode discharges a capacity of 199.0 mAh g^(-1) with 84.3%ICE at 0.1 C and the capacity retention of 95.6%after 100 cycles.This work validates the effectiveness of 3D polymer binder and provides new insights to boost the performance of Si anode.展开更多
Biphenyl-contained monomer of 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] biphenyl （BP-SiH-EP） was prepared via hydrosilylation reaction of 1,4-bis（dimethylsilyl） biphenyl （BP-SiH） and 1,2-epoxy-4-vi...Biphenyl-contained monomer of 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] biphenyl （BP-SiH-EP） was prepared via hydrosilylation reaction of 1,4-bis（dimethylsilyl） biphenyl （BP-SiH） and 1,2-epoxy-4-vinylcyclohexane in the presence of Karstedt＇s catalyst. ^1H-NMR, 13C-NMR and FTIR were used to characterize the structure of the obtained monomer. BP-SiH-EP was then cured by methyl hexahydrophthalic anhydride （MeHHPA） with 1-cyanoethyl-2-ethyl-4- methylimidazole as an accelerator. The polymerization behavior was studied by DSC. The results of DMA measurement demonstrate that the cured BP-SiH-EP/MeHHPA can maintain high storage modulus （〉1 GPa） in a wide range of temperature up to 176 ℃. According to the damping factor curve of DMA, cured BP-SiH-EP/MeHHPA exhibits a high glass transition temperature （Tg） of 192 ℃, which is 20 ℃ higher than that of cured 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] benzene （DEDSB）/MeHHPA. TGA results show that cured BP-SiH-EP/MeHHPA has good thermal stability （Tso/o = 339 ℃） due to the high heat-resistance of rigid biphenyl group. Moreover, the crosslinking density of cured BP-SiH-EP/MeHHPA should be lower than that of cured DEDSB/MeHHPA estimated from their chemical structures, which conflicts with the calculated results based on the rubber elasticity equation. The inconsistence indicates that the calculated crosslinking densities are not comparable, possibly owing to their differences in the rigidity of polymer chains and intermolecular interaction.展开更多
The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting...The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting on the swelling, elongation and crosslinking density was observed. The orientational order arising from the correlation between chain segments decreases with the increase of the numbers of both links between junctions and solvent molecules around segments.展开更多
The effect of neodymium stearate （NdSt） on cure and mechanical properties of expoxidized natural rubber with 25 mol.% epoxidation （ENR25） was studied in the concentration range of 0 to 2 phr, and the relationship ...The effect of neodymium stearate （NdSt） on cure and mechanical properties of expoxidized natural rubber with 25 mol.% epoxidation （ENR25） was studied in the concentration range of 0 to 2 phr, and the relationship between structure and mechanical properties of ENR25 vulcanizates was also discussed. Neodymium sterate was synthesized by saponification of stearic acid with newly formed rare earth hydroxide m water medium, and the structure of NdSt was investigated by Fourier transform infrared spectroscopy （FTIR）. Crosslinking den- sity of vulcanized natural rubber was studied by equilibrium swelling method. The results indicated that the interaction force between carboxylic ion of NdSt prepared in the lab and Nd ion was mainly ionic bond through FTIR analysis. NdSt could accelerate the vulcanization of ENR25 and influence the network structure of ENR25 vulcanizates. The incorporation of 1 phr NdSt for ENR25 vulcanizatcs showed the optimal aging resistance.展开更多
The simulation on pyrolysis products of pure PF resin with different chemical structure was investigated and validated by pyrolysis gas-chromatography mass spectrometry(Py-GC/MS).The simulation of pyrolysis products o...The simulation on pyrolysis products of pure PF resin with different chemical structure was investigated and validated by pyrolysis gas-chromatography mass spectrometry(Py-GC/MS).The simulation of pyrolysis products of phenolic resin with different chemical structure was investigated by AMBER(Assisted Model Building with Energy Refinement)force field.The content of pyrolysis products phenol and cresol decreases with the increase of F/P(formaldehyde/phenol)value.The content of pyrolysis products dimethylphenol and trimethylphenol increases with the enhancement of F/P value.The crosslink density of phenolic mixture can be measured by the content of pyrolysis products dimethylphenol and trimethylphenol.Consequently,the results of simulation were validated by the Py-GC/MS experiment.展开更多
The transfer of graphene from metallic substrates onto application-specific substrates is usually inevitable for the applications of high-quality graphene films derived from chemical vapour deposition(CVD)approaches.C...The transfer of graphene from metallic substrates onto application-specific substrates is usually inevitable for the applications of high-quality graphene films derived from chemical vapour deposition(CVD)approaches.Commonly used to support the graphene films during the transfer,the coating of the polymer would produce the surface contaminations and hinder the industrially compatible transfer.In this work,through the thermal imidization of polyamide acid(PAA)to polyimide(PI)and tuning of the concentration of dangling chains,we achieved the ultraclean and crack-free transfer of graphene wafers with high electronic quality.The resulting contamination-free and hydrophilic surface also enabled the observed improved cell viability in a biomedical applications.By avoiding aqueous etching or the usage of strong bases,our proposed transfer method is industrially compatible for batch transfer of graphene films towards the real applications.展开更多
Oil bleed is a serious problem in elastomeric thermal silicone conductive pads. The components of the oil bleed and the effect of the silicone chemical parameters on the amount ofoil bleed have been determined. The ma...Oil bleed is a serious problem in elastomeric thermal silicone conductive pads. The components of the oil bleed and the effect of the silicone chemical parameters on the amount ofoil bleed have been determined. The main components of oil bleeds are the uncrosslinked silicones in the cured resins, which include the unreacted silicone materials and the macromolecular substances produced by the hydrosilylation reaction. Cured resins with a high crosslinking density and a high molecular weight of vinyl silicone residues had a lower amount of oil bleed. In addition, a low Si-H content also reduced the amount ofoil bleed.展开更多
Sustainable polyurethanes prepared from castor oil and diisocyanates show very low strength and toughness, due to the highly cross-linked and flexible structure. Herein, we report a new strategy to simultaneously rein...Sustainable polyurethanes prepared from castor oil and diisocyanates show very low strength and toughness, due to the highly cross-linked and flexible structure. Herein, we report a new strategy to simultaneously reinforce and toughen castor oil-based polyurethane via incorporating a stiff component （isosorbide, IS） to enhance network stiffness and reduce crosslink density. The crosslinking degree de- creases while the strength, moduli, ductility and heat re- sistance significantly increase accordingly with increasing IS content. The tensile behaviors are tunable over a broad range （either as elastomers or as plastics） depending on the com- positions. The polyurethanes show excellent thermal stability with onset decomposition temperature higher than 280℃. The investigation provides a new hint for future design and fab- rication of high performance sustainable polymers from other vegetable oils.展开更多
基金This work was supported by the National Defense Pre-Research Projects[grant number ZS2015070132A12002].
文摘In order to predict the storage life of a certain type of HTPB(hydroyl-terminated polybutadiene)coating at 25℃ and analyze the influence of pre-strain on the storage life,the accelerated aging tests of HTPB coating at 40℃,50℃,60℃,70℃ with the pre-strain of 0%,3%,6%,9%,respectively were carried out.The variation regularity of the change of crosslinking density was analyzed and the aging model of HTPB coating under pre-strained thermally-accelerated aging was proposed.The storage life of HTPB coating at 25℃ was estimated by using the Berthelot equation as the end point of the aging life with a 30% decrease in maximum elongation.The results showed that the change of crosslinking density of HTPB coating increased with the increase of aging temperature and aging time,and decreased with the increase of pre-strain.Under 0% prestrain,the relationship between the change of crosslinking density of HTPB coating and the aging time can be described by the logarithmic model with the confidence probability greater than 99%.The stress relaxation phenomenon existed under 3%,6%and 9%pre-strained aging.The aging model considering chemical aging and pre-strain was established with the confidence probability greater than 90%.The storage life of HTPB coating was 15.2935 years at 25C under 0% prestrain,which was reduced by 13.9007%,75.6949% and 89.7859% under 3%,6% and 9% pre-strain,respectively.The existence of pre-strain has a serious impact on the storage life of HTPB coating,therefore,the pre-strain should be avoided as much as possible during the actual storage.
基金financially supported by the National Natural Science Foundation of China(No.22171182)Sichuan Tianfu Emei Plan.
文摘Control crosslink network and chain connectivity are essential to develop shape memory polymers(SMPs)with high shape memory capabilities,adjustable response temperature,and satisfying mechanistical properties.In this study,novel poly(ε-caprolactone)(PCL)-poly(2-vinyl)ethylene glycol(PVEG)copolymers bearing multi-pendant vinyl groups is synthesized by branched-selective allylic etherification polymerization of vinylethylene carbonate(VEC)with linear and tetra-arm PCLs under a synergistic catalysis of palladium complex and boron reagent.Facile thiol-ene photo-click reaction of PCL-PVEG copolymers with multifunctional thiols can rapidly access a serious crosslinked SMPs with high shape memory performance.The thermal properties,mechanical properties and response temperature of the obtained SMPs are tunable by the variation of PCL prepolymers,vinyl contents and functionality of thiols.Moreover,high elastic modulus in the rubbery plateau region can be maintained effectively owing to high-density topological networks of the PCL materials.In addition,the utility of the present SMPs is further demonstrated by the post-functionalization via thiol-ene photo-click chemistry.
基金Financial support by the NSFC no. 52371224, 51972156, and 51872131
文摘The intrinsic volume changes(about 300%)of Si anode during the lithiation/delithiation leads to the serious degradation of battery performance despite of theoretical capacity of 3579 mAh g^(-1) of Si.Herein,a three-dimensional(3D)conductive polymer binder with adjustable crosslinking density has been designed by employing citric acid(CA)as a crosslinker between the carboxymethyl cellulose(CMC)and the poly(3,4-ethylenedioxythiophene)poly-(styrene-4-sulfonate)(PEDOT:PSS)to stabilize Si anode.By adjusting the crosslinking density,the binder can achieve a balance between rigidity and flexibility to adapt the volume expansion upon lithiation and reversible volume recovery after delithiation of Si.Therefore,Si/CMC-CA-PEDOT:PSS(Si/CCP)electrode demonstrates an excellent performance with high capacities of 2792.3 mAh g^(-1) at 0.5 A g^(-1) and a high area capacity above 2.6 mAh cm^(-2) under Si loading of 1.38 mg cm^(-2).The full cell Si/CCP paired with Li(Ni_(0.8)Co_(0.1)Mn_(0.1))O_(2) cathode discharges a capacity of 199.0 mAh g^(-1) with 84.3%ICE at 0.1 C and the capacity retention of 95.6%after 100 cycles.This work validates the effectiveness of 3D polymer binder and provides new insights to boost the performance of Si anode.
基金financially supported by the National Natural Science Foundation of China(Nos.51403039 and 21476072)the Natural Science Foundation of Shanghai(No.13ZR1451300)
文摘Biphenyl-contained monomer of 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] biphenyl （BP-SiH-EP） was prepared via hydrosilylation reaction of 1,4-bis（dimethylsilyl） biphenyl （BP-SiH） and 1,2-epoxy-4-vinylcyclohexane in the presence of Karstedt＇s catalyst. ^1H-NMR, 13C-NMR and FTIR were used to characterize the structure of the obtained monomer. BP-SiH-EP was then cured by methyl hexahydrophthalic anhydride （MeHHPA） with 1-cyanoethyl-2-ethyl-4- methylimidazole as an accelerator. The polymerization behavior was studied by DSC. The results of DMA measurement demonstrate that the cured BP-SiH-EP/MeHHPA can maintain high storage modulus （〉1 GPa） in a wide range of temperature up to 176 ℃. According to the damping factor curve of DMA, cured BP-SiH-EP/MeHHPA exhibits a high glass transition temperature （Tg） of 192 ℃, which is 20 ℃ higher than that of cured 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] benzene （DEDSB）/MeHHPA. TGA results show that cured BP-SiH-EP/MeHHPA has good thermal stability （Tso/o = 339 ℃） due to the high heat-resistance of rigid biphenyl group. Moreover, the crosslinking density of cured BP-SiH-EP/MeHHPA should be lower than that of cured DEDSB/MeHHPA estimated from their chemical structures, which conflicts with the calculated results based on the rubber elasticity equation. The inconsistence indicates that the calculated crosslinking densities are not comparable, possibly owing to their differences in the rigidity of polymer chains and intermolecular interaction.
基金Supported by the National Natural Science Foundation of China
文摘The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting on the swelling, elongation and crosslinking density was observed. The orientational order arising from the correlation between chain segments decreases with the increase of the numbers of both links between junctions and solvent molecules around segments.
基金Project supported by the National Program on Key Basic Research Project of China (973 Program,2010CB635109)Ministry of Science and Technology R&D research institutes (contract grantnumber:2008EG134285)
文摘The effect of neodymium stearate （NdSt） on cure and mechanical properties of expoxidized natural rubber with 25 mol.% epoxidation （ENR25） was studied in the concentration range of 0 to 2 phr, and the relationship between structure and mechanical properties of ENR25 vulcanizates was also discussed. Neodymium sterate was synthesized by saponification of stearic acid with newly formed rare earth hydroxide m water medium, and the structure of NdSt was investigated by Fourier transform infrared spectroscopy （FTIR）. Crosslinking den- sity of vulcanized natural rubber was studied by equilibrium swelling method. The results indicated that the interaction force between carboxylic ion of NdSt prepared in the lab and Nd ion was mainly ionic bond through FTIR analysis. NdSt could accelerate the vulcanization of ENR25 and influence the network structure of ENR25 vulcanizates. The incorporation of 1 phr NdSt for ENR25 vulcanizatcs showed the optimal aging resistance.
文摘The simulation on pyrolysis products of pure PF resin with different chemical structure was investigated and validated by pyrolysis gas-chromatography mass spectrometry(Py-GC/MS).The simulation of pyrolysis products of phenolic resin with different chemical structure was investigated by AMBER(Assisted Model Building with Energy Refinement)force field.The content of pyrolysis products phenol and cresol decreases with the increase of F/P(formaldehyde/phenol)value.The content of pyrolysis products dimethylphenol and trimethylphenol increases with the enhancement of F/P value.The crosslink density of phenolic mixture can be measured by the content of pyrolysis products dimethylphenol and trimethylphenol.Consequently,the results of simulation were validated by the Py-GC/MS experiment.
基金supported by the National Natural Science Foundation of China(Nos.T2188101 and 52372038)the National Key Research and Development Program of China(No.2022YFA1204900)the China Postdoctoral Science Foundation(No.2023M740030).
文摘The transfer of graphene from metallic substrates onto application-specific substrates is usually inevitable for the applications of high-quality graphene films derived from chemical vapour deposition(CVD)approaches.Commonly used to support the graphene films during the transfer,the coating of the polymer would produce the surface contaminations and hinder the industrially compatible transfer.In this work,through the thermal imidization of polyamide acid(PAA)to polyimide(PI)and tuning of the concentration of dangling chains,we achieved the ultraclean and crack-free transfer of graphene wafers with high electronic quality.The resulting contamination-free and hydrophilic surface also enabled the observed improved cell viability in a biomedical applications.By avoiding aqueous etching or the usage of strong bases,our proposed transfer method is industrially compatible for batch transfer of graphene films towards the real applications.
文摘Oil bleed is a serious problem in elastomeric thermal silicone conductive pads. The components of the oil bleed and the effect of the silicone chemical parameters on the amount ofoil bleed have been determined. The main components of oil bleeds are the uncrosslinked silicones in the cured resins, which include the unreacted silicone materials and the macromolecular substances produced by the hydrosilylation reaction. Cured resins with a high crosslinking density and a high molecular weight of vinyl silicone residues had a lower amount of oil bleed. In addition, a low Si-H content also reduced the amount ofoil bleed.
基金supported by the National Natural Science Foundation of China (51703188)the Basic and Frontier Research Project of Chongqing (cstc2017jcyj AX0426)the Fundamental Research Funds for the Central Universities (XDJK2017A016 and XDJK2017C022)
文摘Sustainable polyurethanes prepared from castor oil and diisocyanates show very low strength and toughness, due to the highly cross-linked and flexible structure. Herein, we report a new strategy to simultaneously reinforce and toughen castor oil-based polyurethane via incorporating a stiff component （isosorbide, IS） to enhance network stiffness and reduce crosslink density. The crosslinking degree de- creases while the strength, moduli, ductility and heat re- sistance significantly increase accordingly with increasing IS content. The tensile behaviors are tunable over a broad range （either as elastomers or as plastics） depending on the com- positions. The polyurethanes show excellent thermal stability with onset decomposition temperature higher than 280℃. The investigation provides a new hint for future design and fab- rication of high performance sustainable polymers from other vegetable oils.
