Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resista...Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.展开更多
Along with the developing technology in the rubber industry, the use of natural and synthetic rubbers as well as liquid rubbers has increased significantly in recent years. The formulation of the tread compound, which...Along with the developing technology in the rubber industry, the use of natural and synthetic rubbers as well as liquid rubbers has increased significantly in recent years. The formulation of the tread compound, which directly affects the performance of a tire, is generally produced from natural and synthetic rubbers. Intensive scientific studies have been carried out on liquid rubbers because they reduce the consumption of process oils used in the tire production phase and increase dispersion. In this study, the rheological and physico-mechanical properties of rubbers developed using only liquid rubber (liquid isoprene and liquid SBR) with four different viscosities and without using process oil (Styrene Butadiene Rubber—SBR) were investigated. It has been observed that the rubber blends produced by adding four different liquid rubbers to the same recipe caused changes in rheological and physico-mechanical properties compared to the reference sample. It was observed that the minimum torque/viscosity (ML), maximum torque/viscosity (MH) and curing time (t90) in some of the formulas tested decreased significantly due to the use of liquid rubber.展开更多
Gaskets are applied in PEMFCs(proton exchange membrane fuel cells) to keep reactant gases and liquid within their respective regions, which are of great significance for the both sealing and electrochemical performa...Gaskets are applied in PEMFCs(proton exchange membrane fuel cells) to keep reactant gases and liquid within their respective regions, which are of great significance for the both sealing and electrochemical performance of fuel cells during the long-term operation. In this study, the degradation of silicone rubbers, often selected as seals in PEMFCs, in Fenton's reagents with different H_2O_2 concentrations was investigated. The changes in chemical properties, mechanical behavior and surface morphology of the samples were studied before and after exposure to the test environment over time. It is found that increasing H_2O_2 concentration will degrade the rubbers more severely. The experimental results elucidate the degradation mechanism of silicone rubbers in Fenton's reagents and the influence of H_2O_2 in the degradation process.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
Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic,...Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth (MSE) walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents (5 wt%, 10 wt%, 15 wt% and 20 wt%) of recycled crumb rubber (RCR) to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry (PIV) technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.展开更多
In this paper, the automated grid method is applied to test for the mechanical properties of conditioned rubbers under the moderate ?nite deformation (not exceeding 100%). More accurate stress-strain curve...In this paper, the automated grid method is applied to test for the mechanical properties of conditioned rubbers under the moderate ?nite deformation (not exceeding 100%). More accurate stress-strain curves of conditioned rubber specimens under di?erent conditioned strains are obtained. Test results show di?erences between these curves. Based on an analysis of the classical constitutive models, a new modi?ed eight-chain model is proposed, which takes account of both the locking stretch of chains and the interaction e?ect in the network. Fitting test data shows that the modi?ed model well characterizes the incompressible hyperelastic mechanical behavior of conditioned rubbers under the moderate ?nite deformation as well as under the large deformation.展开更多
Comprehensive Summary,As one of the three types of polymeric materials,rubber has played an irreplaceable role in various fields such as industrial production,aerospace,military,and national defense.Improving the cold...Comprehensive Summary,As one of the three types of polymeric materials,rubber has played an irreplaceable role in various fields such as industrial production,aerospace,military,and national defense.Improving the cold resistance of rubbers and extending their service temperature range have always been one of the main focuses in rubber research.However,there have been few detailed public reports or literatures on the progress or summary of cold-resistant rubbers,creating an invisible barrier for new researchers wishing to enter this field of research.Therefore,starting from the basis of polymer physics,this review introduces the research difficulties in this field and systematically summarizes the research progress in constructing cold-resistant rubbers based on three different types of flexible polymer chains in recent years.In addition,several important properties of cold-resistant rubbers including mechanical performance,oil resistance,and self-healing ability are also discussed along with the summary of recent progresses.Finally,the future challenges and prospects of cold-resistant rubbers are discussed.展开更多
To illustrate mechanisms of Payne effect in rubbers and their nanocomposites experiencing large amplitude oscillatory shear(LAOS),comparison studies were performed in styrene-isoprene-styrene(SIS)copolymers and their ...To illustrate mechanisms of Payne effect in rubbers and their nanocomposites experiencing large amplitude oscillatory shear(LAOS),comparison studies were performed in styrene-isoprene-styrene(SIS)copolymers and their selectively crosslinked materials at temperatures below and above glass transition temperature of the polystyrene(PS)phase.It was found that under periodic dynamic shear,the strain softening is reversible when the polyisoprene(PI)phase,either crosslinked or not,is restricted by hard PS domains but it shows hysteresis once the PS domains disassociate.The strain softening can happen at the time scale of intrinsic Rouse relaxation of elastically active network strands.Critical stress of strain softening scales with number density of elastically active network strands,a simple relation being verified not only in the selectively crosslinked SIS copolymers but also in PI gum vulcanizates and carbon black filled PI compounds.Payne effect is traditionally used to term strain softening of highly filled rubber vulcanizates under LAOS deformation while evidenced herein is that the Payne effect of highly filled rubber vulcanizates shares the mechanism being common to the strain softening of SIS copolymers.展开更多
Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rat...Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rate sensitivity and strain hardening index increase with increasing nanorubber content.Potential mechanisms are proposed based on numerical simulations using a unit cell model.An increase in the strain rate sensitivity with increasing nanorubber content results from the fact that the nanorubber becomes less incompressible at high strain,generating a higher hydro-static pressure.Adiabatic shear localization starts to occur in the epoxy under a strain rate of 22,000 s^(-1) when the strain exceeds 0.35.The presence of nanorubber in the epoxy reduces adiabatic shear localization by preventing it from propagating.展开更多
The cubic stiffness force model(CSFM)and Bouc-Wen model(BWM)are introduced and compared innovatively.The unknown coefficients of the nonlinear models are identified by the genetic algorithm combined with experiments.B...The cubic stiffness force model(CSFM)and Bouc-Wen model(BWM)are introduced and compared innovatively.The unknown coefficients of the nonlinear models are identified by the genetic algorithm combined with experiments.By fitting the identified nonlinear coefficients under different excitation amplitudes,the nonlinear vibration responses of the system are predicted.The results show that the accuracy of the BWM is higher than that of the CSFM,especially in the non-resonant region.However,the optimization time of the BWM is longer than that of the CSFM.展开更多
The present study evaluates the potential of a bio-inspired pulsation damper in a vane pump used in mobile hydraulic ap- plications. Pressure pulsations caused by such positive displacement pumps can lead to malfuncti...The present study evaluates the potential of a bio-inspired pulsation damper in a vane pump used in mobile hydraulic ap- plications. Pressure pulsations caused by such positive displacement pumps can lead to malfunctions and noise in a hydraulic system. A common measure to reduce pressure pulsations is the integration of pressure pulsation dampers downstream of the pump. This type of damping measure can also be found in biology as e.g. in the human blood circulatory system. Such working principles found in living organisms offer a high potential for a biomimetic transfer into technical applications. The newly developed bio-inspired damper consists of cellular rubbers with non-linear viscoelastic material properties. In order to evaluate the new damping method, pressure pulsations were measured at two different back pressures and at a wide engine speed range of the vane pump. For further assessment, different setups, varying the stiffness of the cellular rubber materials and the damper volume, were tested. Within the tested back pressures, the pressure pulsations could be reduced by up to 40%. The developed integrated pulsation damper offers a high potential to dampen pressure pulsations of positive displacement pumps used in mobile hydraulic applications ooeratin~ below 10 bar.展开更多
High-intensity earthquakes can cause severe damage to bridges,buildings,and ground surfaces,as well as disrupt human activities.Such earthquakes can create long-distance,high-intensity surface movements that negativel...High-intensity earthquakes can cause severe damage to bridges,buildings,and ground surfaces,as well as disrupt human activities.Such earthquakes can create long-distance,high-intensity surface movements that negatively impact bridge structures.This article delves into the seismic reduction and isolation design strategies for bridges in high-intensity earthquake areas.It analyzes various seismic reduction and isolation technologies and provides case studies to help relevant units understand the design strategies of these technologies.The results of this article can be used as a guideline to effectively enhance the seismic performance of bridges in high-intensity earthquake areas.展开更多
The molecular weight of a polymer is of prime importance and greatly influences the processing and mechanical properties of the polymer. Trans-1,4-poly(butadiene-co-isoprene) multi-block copolymer rubbers(TBIR) exhibi...The molecular weight of a polymer is of prime importance and greatly influences the processing and mechanical properties of the polymer. Trans-1,4-poly(butadiene-co-isoprene) multi-block copolymer rubbers(TBIR) exhibit outstanding fatigue resistance, low heat build-up and good abrasion resistance, and are expected to be desirable candidate for high performance tire. Study on the influence of TBIR with different molecular weights on the structure and properties of TBIR and natural rubber(NR)/TBIR blends is essential to understand its contribution to the greatly improved dynamic properties of the rubber vulcanizates. TBIR with different molecular weights characterized by 1H-NMR, 13C-NMR, GPC, and DSC were highly trans-1,4-copolymers with similar chain sequence distribution and crystalline trans-1,4-polyisoprene(TPI) blocks. The green strength and modulus of TBIR increased with the increasing molecular weight.The NR/TBIR compounds filled with 40 phr carbon black were chemically cured by sulfur for the preparation of NR/TBIR vulcanizates.The compatibility between NR and TBIR, filler distribution, crosslinking bond and density, and properties of NR/TBIR vulcanizates were studied. The NR/TBIR vulcanizates showed increasing tensile strength, hardness, modulus, rebound, abrasion resistance, and flexural fatigue properties with increasing molecular weight of TBIR. Furthermore, they presented significant improvement in flexural fatigue resistance when compared with that of NR vulcanizate. The contribution mechanism of TBIR on the NR/TBIR blends was discussed. The TBIR with a wide range of molecular weight are ideal rubbers for high performance tires.展开更多
To meet the increasing demand for safe, environmentally friendly and high-performance smart materials, self-healing rubbers are highly desired. Here, the self-healing performance of ethylene propylene diene monomer ru...To meet the increasing demand for safe, environmentally friendly and high-performance smart materials, self-healing rubbers are highly desired. Here, the self-healing performance of ethylene propylene diene monomer rubber (EPDM) is reported, which was designed by graft-polymerization of zinc dimethacrylate (ZDMA) onto rubber chains to form a reversible ionic cross-linked network. Single ionic cross-linked network and dual network, combining covalent and ionic cross-links, could be tuned by controlling vulcanization process to achieve tailorable mechanical and self-healing properties. It was found that ionic cross-linked EPDM showed a recovery of more than 95% of the original mechanical strength through a healing process of 1 h at 100 °C. The covalent cross-links could improve mechanical properties but block self-healing. Adding 50 wt% liquid rubber to “dry” EPDM could effectively enhance self-healing capability of the dual cross-linked network and the healed tensile strength could reach 0.9 MPa. A compromise between mechanical performance and healing capability could be potentially tailored by controlling vulcanization process and liquid rubber content.展开更多
China is rich in rare earth resources. Rare earth elements, also named lanthanides, are number 58 to number 81 elements in the elemental periodic table. They have unique electronic structures and may form various coor...China is rich in rare earth resources. Rare earth elements, also named lanthanides, are number 58 to number 81 elements in the elemental periodic table. They have unique electronic structures and may form various coordination compounds. In the early 1960s, researchers at the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (CIAC) found the catalytic activities of lanthanide compounds in stereospecific polymerization of conjugated dienes, and published the first paper on this topic in 1964. On the basis of this finding, CIAC launched extensive research activities on lanthanide compounds as diene polymerization catalysts, from a series of fundamental research to the efforts of industrializing the rare earth catalyzed cis-1,4-polybutatine rubber and cis-1,4-polyisoprene rubber. This review aims to summarize the progress in this field in the past half century.展开更多
One prominent method of modifying the properties of dielectric elastomers(DEs)is by adding suitable metal oxide fillers.However,almost all commercially available sili-cone elastomers are already heavily filled with si...One prominent method of modifying the properties of dielectric elastomers(DEs)is by adding suitable metal oxide fillers.However,almost all commercially available sili-cone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting metal oxide filled elastomer may contain too much filler.We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler.Liquid silicone rubber(LSR)has relatively low viscosity,which is favorable for loading inorganic fillers.In the present study,four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber(RTV)were investigated.The resulting elastomers were evaluated with respect to their dielectric permittivity,tear and tensile strengths,electrical breakdown,thermal stability and dynamic viscosity.Filled silicone elasto-mers with high loadings of nano-sized titanium dioxide(TiO_(2))particles were also studied.The best overall performing formulation had 35 wt.%TiO_(2) nanoparticles in the POWERSIL®XLR LSR,where the excellent ensemble of relative dielectric permittivity of 4.9 at 0.1 Hz,breakdown strength of 160 V µm^(−1),tear strength of 5.3 MPa,elongation at break of 190%,a Young’s modulus of 0.85 MPa and a 10% strain response(simple tension)in a 50 Vμm^(−1) electric field was obtained.展开更多
A reactive flame retardant cross-linker(SPTES) was successfully synthesized with dichloropentate and 3-triethoxysily-lpropylamine(APTES) in this research. Then it was further applied into the room temperature vulc...A reactive flame retardant cross-linker(SPTES) was successfully synthesized with dichloropentate and 3-triethoxysily-lpropylamine(APTES) in this research. Then it was further applied into the room temperature vulcanized(RTV) silicone rubber to prepare novel flame retarded RTV silicone rubbers containing phosphorus. The structure, thermal degradation stability, mechanical properties and flammability properties of the novel RTV silicone rubbers were tested and characterized. The results showed that the mechanical and flammability properties of the RTV silicone rubber simultaneously got better with the SPTES content increased. Compared with the sample prepared by APTES, the tensile strength of novel RTV silicone rubbers increased from 0.12 MPa to 0.38 MPa and the limit oxygen index increased from 19.8 to 23.5.展开更多
In 1920,Hermann Staudinger put forward the concept that rubber is composed of isoprene units,which has been considered as the beginning of“macromolecular science”or“polymer science.”The past 100 years’development...In 1920,Hermann Staudinger put forward the concept that rubber is composed of isoprene units,which has been considered as the beginning of“macromolecular science”or“polymer science.”The past 100 years’development of polymer science has witnessed the greatness and foresight of this groundbreaking theory.On the occasion of the 100th anniversary of the birth of polymer science,this paper is dedicated to recalling a piece of research history on rubber.展开更多
Exciting R&D progress(1) Fluorine rubber makers closely follow environmental protection requirementsPushed by the rapid development of down-stream sectors such as
SBR In October 2008,because of the slack economy globally,the export of SBR (styrene-butadiene rubber) downstream products was apparently affected,and the demand for SBR in downstream sectors fell further.China’s SBR...SBR In October 2008,because of the slack economy globally,the export of SBR (styrene-butadiene rubber) downstream products was apparently affected,and the demand for SBR in downstream sectors fell further.China’s SBR producers consider-ably lowered ex-factory prices,China’s price of SBR therefore was down consider-ably in response to the soft demand展开更多
基金funded by the Science and Technology Research and Development Plan of the China State Railway Group Company Limited(No.N2023J053).
文摘Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.
文摘Along with the developing technology in the rubber industry, the use of natural and synthetic rubbers as well as liquid rubbers has increased significantly in recent years. The formulation of the tread compound, which directly affects the performance of a tire, is generally produced from natural and synthetic rubbers. Intensive scientific studies have been carried out on liquid rubbers because they reduce the consumption of process oils used in the tire production phase and increase dispersion. In this study, the rheological and physico-mechanical properties of rubbers developed using only liquid rubber (liquid isoprene and liquid SBR) with four different viscosities and without using process oil (Styrene Butadiene Rubber—SBR) were investigated. It has been observed that the rubber blends produced by adding four different liquid rubbers to the same recipe caused changes in rheological and physico-mechanical properties compared to the reference sample. It was observed that the minimum torque/viscosity (ML), maximum torque/viscosity (MH) and curing time (t90) in some of the formulas tested decreased significantly due to the use of liquid rubber.
基金the Natural Science Foundation of China(No.21476178)the Fundamental Research Funds for the Central Universities(WUT:2015IVA059)
文摘Gaskets are applied in PEMFCs(proton exchange membrane fuel cells) to keep reactant gases and liquid within their respective regions, which are of great significance for the both sealing and electrochemical performance of fuel cells during the long-term operation. In this study, the degradation of silicone rubbers, often selected as seals in PEMFCs, in Fenton's reagents with different H_2O_2 concentrations was investigated. The changes in chemical properties, mechanical behavior and surface morphology of the samples were studied before and after exposure to the test environment over time. It is found that increasing H_2O_2 concentration will degrade the rubbers more severely. The experimental results elucidate the degradation mechanism of silicone rubbers in Fenton's reagents and the influence of H_2O_2 in the degradation process.
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.
文摘Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth (MSE) walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents (5 wt%, 10 wt%, 15 wt% and 20 wt%) of recycled crumb rubber (RCR) to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry (PIV) technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.
文摘In this paper, the automated grid method is applied to test for the mechanical properties of conditioned rubbers under the moderate ?nite deformation (not exceeding 100%). More accurate stress-strain curves of conditioned rubber specimens under di?erent conditioned strains are obtained. Test results show di?erences between these curves. Based on an analysis of the classical constitutive models, a new modi?ed eight-chain model is proposed, which takes account of both the locking stretch of chains and the interaction e?ect in the network. Fitting test data shows that the modi?ed model well characterizes the incompressible hyperelastic mechanical behavior of conditioned rubbers under the moderate ?nite deformation as well as under the large deformation.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.22105222 and 21825503).
文摘Comprehensive Summary,As one of the three types of polymeric materials,rubber has played an irreplaceable role in various fields such as industrial production,aerospace,military,and national defense.Improving the cold resistance of rubbers and extending their service temperature range have always been one of the main focuses in rubber research.However,there have been few detailed public reports or literatures on the progress or summary of cold-resistant rubbers,creating an invisible barrier for new researchers wishing to enter this field of research.Therefore,starting from the basis of polymer physics,this review introduces the research difficulties in this field and systematically summarizes the research progress in constructing cold-resistant rubbers based on three different types of flexible polymer chains in recent years.In addition,several important properties of cold-resistant rubbers including mechanical performance,oil resistance,and self-healing ability are also discussed along with the summary of recent progresses.Finally,the future challenges and prospects of cold-resistant rubbers are discussed.
基金the National Natural Science Foundation of China(Nos.U1908221,51873190 and 51790503)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(No.2021SZ-TD002).
文摘To illustrate mechanisms of Payne effect in rubbers and their nanocomposites experiencing large amplitude oscillatory shear(LAOS),comparison studies were performed in styrene-isoprene-styrene(SIS)copolymers and their selectively crosslinked materials at temperatures below and above glass transition temperature of the polystyrene(PS)phase.It was found that under periodic dynamic shear,the strain softening is reversible when the polyisoprene(PI)phase,either crosslinked or not,is restricted by hard PS domains but it shows hysteresis once the PS domains disassociate.The strain softening can happen at the time scale of intrinsic Rouse relaxation of elastically active network strands.Critical stress of strain softening scales with number density of elastically active network strands,a simple relation being verified not only in the selectively crosslinked SIS copolymers but also in PI gum vulcanizates and carbon black filled PI compounds.Payne effect is traditionally used to term strain softening of highly filled rubber vulcanizates under LAOS deformation while evidenced herein is that the Payne effect of highly filled rubber vulcanizates shares the mechanism being common to the strain softening of SIS copolymers.
基金supported by the Key Research and Development Plan of Shaanxi Province (2023-GHZD-12)the Opening Fund of State Key Laboratory for Strength and Vibration of Mechanical Structures (SVL2021-KF-12)+1 种基金Fundamental Research Funds for the Central Universities (G2020KY05112)the 111 Project (BP0719007)
文摘Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rate sensitivity and strain hardening index increase with increasing nanorubber content.Potential mechanisms are proposed based on numerical simulations using a unit cell model.An increase in the strain rate sensitivity with increasing nanorubber content results from the fact that the nanorubber becomes less incompressible at high strain,generating a higher hydro-static pressure.Adiabatic shear localization starts to occur in the epoxy under a strain rate of 22,000 s^(-1) when the strain exceeds 0.35.The presence of nanorubber in the epoxy reduces adiabatic shear localization by preventing it from propagating.
文摘The cubic stiffness force model(CSFM)and Bouc-Wen model(BWM)are introduced and compared innovatively.The unknown coefficients of the nonlinear models are identified by the genetic algorithm combined with experiments.By fitting the identified nonlinear coefficients under different excitation amplitudes,the nonlinear vibration responses of the system are predicted.The results show that the accuracy of the BWM is higher than that of the CSFM,especially in the non-resonant region.However,the optimization time of the BWM is longer than that of the CSFM.
文摘The present study evaluates the potential of a bio-inspired pulsation damper in a vane pump used in mobile hydraulic ap- plications. Pressure pulsations caused by such positive displacement pumps can lead to malfunctions and noise in a hydraulic system. A common measure to reduce pressure pulsations is the integration of pressure pulsation dampers downstream of the pump. This type of damping measure can also be found in biology as e.g. in the human blood circulatory system. Such working principles found in living organisms offer a high potential for a biomimetic transfer into technical applications. The newly developed bio-inspired damper consists of cellular rubbers with non-linear viscoelastic material properties. In order to evaluate the new damping method, pressure pulsations were measured at two different back pressures and at a wide engine speed range of the vane pump. For further assessment, different setups, varying the stiffness of the cellular rubber materials and the damper volume, were tested. Within the tested back pressures, the pressure pulsations could be reduced by up to 40%. The developed integrated pulsation damper offers a high potential to dampen pressure pulsations of positive displacement pumps used in mobile hydraulic applications ooeratin~ below 10 bar.
文摘High-intensity earthquakes can cause severe damage to bridges,buildings,and ground surfaces,as well as disrupt human activities.Such earthquakes can create long-distance,high-intensity surface movements that negatively impact bridge structures.This article delves into the seismic reduction and isolation design strategies for bridges in high-intensity earthquake areas.It analyzes various seismic reduction and isolation technologies and provides case studies to help relevant units understand the design strategies of these technologies.The results of this article can be used as a guideline to effectively enhance the seismic performance of bridges in high-intensity earthquake areas.
基金financially supported by the National Basic Research Program of China(No.2015CB654700(2015CB 654706))Major Program of Shandong Province Natural Science Foundation(No.ZR2017ZA0304)Taishan Scholar Program
文摘The molecular weight of a polymer is of prime importance and greatly influences the processing and mechanical properties of the polymer. Trans-1,4-poly(butadiene-co-isoprene) multi-block copolymer rubbers(TBIR) exhibit outstanding fatigue resistance, low heat build-up and good abrasion resistance, and are expected to be desirable candidate for high performance tire. Study on the influence of TBIR with different molecular weights on the structure and properties of TBIR and natural rubber(NR)/TBIR blends is essential to understand its contribution to the greatly improved dynamic properties of the rubber vulcanizates. TBIR with different molecular weights characterized by 1H-NMR, 13C-NMR, GPC, and DSC were highly trans-1,4-copolymers with similar chain sequence distribution and crystalline trans-1,4-polyisoprene(TPI) blocks. The green strength and modulus of TBIR increased with the increasing molecular weight.The NR/TBIR compounds filled with 40 phr carbon black were chemically cured by sulfur for the preparation of NR/TBIR vulcanizates.The compatibility between NR and TBIR, filler distribution, crosslinking bond and density, and properties of NR/TBIR vulcanizates were studied. The NR/TBIR vulcanizates showed increasing tensile strength, hardness, modulus, rebound, abrasion resistance, and flexural fatigue properties with increasing molecular weight of TBIR. Furthermore, they presented significant improvement in flexural fatigue resistance when compared with that of NR vulcanizate. The contribution mechanism of TBIR on the NR/TBIR blends was discussed. The TBIR with a wide range of molecular weight are ideal rubbers for high performance tires.
基金financially supported by the National Basic Research Program of China (Nos. 2015CB654700 and 2015CB654706)the National Natural Science Foundation of China (No. 51403115)the Key Laboratory of Rubber-Plastics, Ministry of Education/ Shandong Provincial Key Laboratory of Rubber-plastics of Qingdao University of Science & Technology (KF2017008)
文摘To meet the increasing demand for safe, environmentally friendly and high-performance smart materials, self-healing rubbers are highly desired. Here, the self-healing performance of ethylene propylene diene monomer rubber (EPDM) is reported, which was designed by graft-polymerization of zinc dimethacrylate (ZDMA) onto rubber chains to form a reversible ionic cross-linked network. Single ionic cross-linked network and dual network, combining covalent and ionic cross-links, could be tuned by controlling vulcanization process to achieve tailorable mechanical and self-healing properties. It was found that ionic cross-linked EPDM showed a recovery of more than 95% of the original mechanical strength through a healing process of 1 h at 100 °C. The covalent cross-links could improve mechanical properties but block self-healing. Adding 50 wt% liquid rubber to “dry” EPDM could effectively enhance self-healing capability of the dual cross-linked network and the healed tensile strength could reach 0.9 MPa. A compromise between mechanical performance and healing capability could be potentially tailored by controlling vulcanization process and liquid rubber content.
文摘China is rich in rare earth resources. Rare earth elements, also named lanthanides, are number 58 to number 81 elements in the elemental periodic table. They have unique electronic structures and may form various coordination compounds. In the early 1960s, researchers at the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (CIAC) found the catalytic activities of lanthanide compounds in stereospecific polymerization of conjugated dienes, and published the first paper on this topic in 1964. On the basis of this finding, CIAC launched extensive research activities on lanthanide compounds as diene polymerization catalysts, from a series of fundamental research to the efforts of industrializing the rare earth catalyzed cis-1,4-polybutatine rubber and cis-1,4-polyisoprene rubber. This review aims to summarize the progress in this field in the past half century.
基金The authors gratefully acknowledge the financial support of InnovationsFonden.
文摘One prominent method of modifying the properties of dielectric elastomers(DEs)is by adding suitable metal oxide fillers.However,almost all commercially available sili-cone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting metal oxide filled elastomer may contain too much filler.We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler.Liquid silicone rubber(LSR)has relatively low viscosity,which is favorable for loading inorganic fillers.In the present study,four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber(RTV)were investigated.The resulting elastomers were evaluated with respect to their dielectric permittivity,tear and tensile strengths,electrical breakdown,thermal stability and dynamic viscosity.Filled silicone elasto-mers with high loadings of nano-sized titanium dioxide(TiO_(2))particles were also studied.The best overall performing formulation had 35 wt.%TiO_(2) nanoparticles in the POWERSIL®XLR LSR,where the excellent ensemble of relative dielectric permittivity of 4.9 at 0.1 Hz,breakdown strength of 160 V µm^(−1),tear strength of 5.3 MPa,elongation at break of 190%,a Young’s modulus of 0.85 MPa and a 10% strain response(simple tension)in a 50 Vμm^(−1) electric field was obtained.
基金Supported by the National Natural Science Foundation of China(51572201)the Project of the State Admimistration of Science,Technology and Industry for National Defense,PRC
文摘A reactive flame retardant cross-linker(SPTES) was successfully synthesized with dichloropentate and 3-triethoxysily-lpropylamine(APTES) in this research. Then it was further applied into the room temperature vulcanized(RTV) silicone rubber to prepare novel flame retarded RTV silicone rubbers containing phosphorus. The structure, thermal degradation stability, mechanical properties and flammability properties of the novel RTV silicone rubbers were tested and characterized. The results showed that the mechanical and flammability properties of the RTV silicone rubber simultaneously got better with the SPTES content increased. Compared with the sample prepared by APTES, the tensile strength of novel RTV silicone rubbers increased from 0.12 MPa to 0.38 MPa and the limit oxygen index increased from 19.8 to 23.5.
基金This work was financially supported by the National Natural Science Foundation of China(21674127 and 21825503).
文摘In 1920,Hermann Staudinger put forward the concept that rubber is composed of isoprene units,which has been considered as the beginning of“macromolecular science”or“polymer science.”The past 100 years’development of polymer science has witnessed the greatness and foresight of this groundbreaking theory.On the occasion of the 100th anniversary of the birth of polymer science,this paper is dedicated to recalling a piece of research history on rubber.
文摘Exciting R&D progress(1) Fluorine rubber makers closely follow environmental protection requirementsPushed by the rapid development of down-stream sectors such as
文摘SBR In October 2008,because of the slack economy globally,the export of SBR (styrene-butadiene rubber) downstream products was apparently affected,and the demand for SBR in downstream sectors fell further.China’s SBR producers consider-ably lowered ex-factory prices,China’s price of SBR therefore was down consider-ably in response to the soft demand