Incorporation of carbon black(CB)in natural rubber(NR)enhances the Mullins effect and Payne effect of their vulcanizates,but the strain softening mechanisms and the microstructure evolution in the vulcanizates have no...Incorporation of carbon black(CB)in natural rubber(NR)enhances the Mullins effect and Payne effect of their vulcanizates,but the strain softening mechanisms and the microstructure evolution in the vulcanizates have not been clearly concluded so far.We investigate the Mullins effect and Payne effect of CB filled NR vulcanizates by using cyclic tensile tests at different temperatures and dynamic rheological measurements combined with simultaneous electric conduction.During cyclic stretching,the normalized recovery hysteresis energy and accumulative softening energy for NR/CB vulcanizates with different loadings can be both superimposed on a master curve,indicating that the Mullins effect is mainly dominated by the rubber matrix.The irreversible simultaneous resistance evolution also reveals that the structural evolution of nanoparticles(NPs)network is not directly related to the Mullins effect.Moreover,the extension of linear viscoelastic region and the hysteresis of Payne effect for filled vulcanizates subjected to cyclic stretching indicate the destruction of CB aggregated structure and the interfacial layers between CB and rubber chains during cyclic stretching.This investigation would be illuminating for the microstructure evolution and strain softening of rubber nanocomposites under harsh service conditions.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
We reported an approach to reconstruct the complex phase morphology of impact polypropylene copolymer （IPC） with core-shell dispersed particles and to optimize its toughness in approximate shear condition. The molte...We reported an approach to reconstruct the complex phase morphology of impact polypropylene copolymer （IPC） with core-shell dispersed particles and to optimize its toughness in approximate shear condition. The molten-state annealing results indicate that the phase structure with core-shell dispersed particles is unstable and could be completely destroyed by static annealing, resulting in the degradation of impact strength. By using a co-rotating twin screw extruder, we found that the dispersed particle with core-shell structure could be rebuilt in appropriate condition with the recovery of excellent impact strength due to both the huge interfacial tension during solidification and the great difference in viscosity of components. Results reveal that almost all the extruded IPCs show the impact strength 60%-90% higher than that of annealed IPCs at room temperature. And the twice-extruded IPC shows the highest impact strength, 446% higher than that of IPC annealed for 30 min. As for low temperature tests, the impact strength of extruded IPCs also increases by 33%-58%. According to adjusting the processing conditions including extrusion speed, extrusion frequency and temperature, an optimization of toughness was well established.展开更多
The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations.Methods for solving the contradiction between improving reinforcement and redu...The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations.Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed.Herein carbon black(CB)filled isoprene rubber(IR)/liquid isoprene rubber(LR)blend nanocomposites with similar crosslink density(ve)are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated.The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes.Meanwhile,tuning ve and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances.The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.展开更多
As a widely used reinforcing filler of rubber, carbon black(CB) often enhances the nonlinear Payne effect and its mechanism still remains controversial. We adopt simultaneous measurement of rheological and electrical ...As a widely used reinforcing filler of rubber, carbon black(CB) often enhances the nonlinear Payne effect and its mechanism still remains controversial. We adopt simultaneous measurement of rheological and electrical behaviors for styrene-butadiene rubber(SBR)/CB compounds and CB gel(CBG) during large deformation/recovery to investigate the contribution of conductive CB network evolution to the Payne effect of the compounds. In the highly filled compounds, the frequency dependence of their strain softening behavior is much more remarkable than that of their CB network breakdown during loading, while during unloading the unrecoverable filler network hardly affects the complete recovery of modulus, both revealing that their Payne effect should be dominated by the disentanglement of SBR matrix. Furthermore,the bound rubber adjacent to CB particles can accelerate the reconstruction of continuous CB network and improve the reversibility of Payne effect. This may provide new insights into the effect of filler network, bound rubber, and free rubber on the Payne effect of CB filled SBR compounds.展开更多
Polystyrene coated silica（SiO_2@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxys...Polystyrene coated silica（SiO_2@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO_2 nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO_2@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO_2 and silane modified SiO_2 nanoparticles.Suspensions of the untreated and the silane modified SiO_2 exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO_2 at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.展开更多
Modulated-temperature differential scanning calorimetric and dynamic mechanical analyses and dielectric spectroscopy were used to investigate the glass transition of hydrated wheat gliadin powders with moisture absorp...Modulated-temperature differential scanning calorimetric and dynamic mechanical analyses and dielectric spectroscopy were used to investigate the glass transition of hydrated wheat gliadin powders with moisture absorption ranged from 2.30 db% to 18.21 db%. Glass transition temperature （Tg） of dry wheat gliadin was estimated according to the Gordon- Taylor equation. Structural heterogeneity at high degrees of hydration was revealed in dielectric temperature and frequency spectra. The activation energies （Ea） of the two relaxations were calculated from Arrhenius equation.展开更多
Payne effect and its associated weak overshoot are of importance for understanding and regulating the softening of rubber nanocomposites under large amplitude oscillations.Herein,Payne effect in diverse filled vulcani...Payne effect and its associated weak overshoot are of importance for understanding and regulating the softening of rubber nanocomposites under large amplitude oscillations.Herein,Payne effect in diverse filled vulcanizates is investigated for generalizing the common characteristics.Master curves of strain amplitude dependent storage modulus are created with respect to microscopic strain amplitude of the matrix,revealing a matrix-dominated elastic nonlinearity being independent of type and dispersity of filler,crosslinking density and sol fraction of matrix and filler-rubber interfacial interactions.However,carbonaceous fillers with higher affinity to the rubber matrices yield lower strain amplification and higher overshoot behavior in comparison with siliceous silica.The investigation would be illuminating for preparing rubber nanocomposites with optimized reinforcement and softening performances.展开更多
Electric conductivity and rheological responses of colloidal electrolytes consisting of lithium bis(trifluoromethanesulfon)imide, polyethylene glycol(PEG) oligomer, and fumed silica have been investigated. Incorporati...Electric conductivity and rheological responses of colloidal electrolytes consisting of lithium bis(trifluoromethanesulfon)imide, polyethylene glycol(PEG) oligomer, and fumed silica have been investigated. Incorporating silica could improve ionic conductivity of the electrolytes at the same lithium/oxygen ratios. The colloidal electrolytes demonstrate a sol to gel transition with increasing silica content while they exhibit shear thickening behaviors during steady flow at intermediate range of strain rate. The presence of lithium salt, on the one hand, could lower the crystallinity of PEG or forbid the crystallization and on the other hand, interferes the chain adsorption on the surface of silica. Furthermore, lithium salt strongly retards the segmental relaxation of PEG in the colloidal electrolytes.展开更多
The variation of phase morphology, critical temperature of demixing, and molecular dynamics for polystyrene/poly（vinyl methyl ether）（PS/PVME） blends induced by hydrophilic nanosilica（A200） or hydrophobic nanosil...The variation of phase morphology, critical temperature of demixing, and molecular dynamics for polystyrene/poly（vinyl methyl ether）（PS/PVME） blends induced by hydrophilic nanosilica（A200） or hydrophobic nanosilica（R974） was investigated. With the phase separation of blend matrix, A200 migrated into PVME-rich phase due to strong interaction between A200 and PVME, while R974 moved into PS-rich phase. The thermodynamic miscibility and concentration fluctuation during phase separation of blend matrix were remarkably retarded by A200 nanoparticles due to the surface adsorption of PVME on A200, verified by the correlation length ξ near the critical region from rheological measurement and the weakened increment of reversing heat capacity（ΔCp） during glass transition via modulated differential scanning calorimetry（MDSC）. The restricted chain diffusion induced by nanosilica still occurred despite no influence of A200 and R974 on the segmental dynamics of homogenous blend matrix. The interactions between nanosilica and polymer components could restrict the terminal relaxation of blend matrix and further manipulate their phase behavior.展开更多
Poly(vinyl alcohol)(PVA)is usually processed and used in a form of aqueous dispersion.A large number of inter-and intramolecular hydrogen bonds make it very difficult to obtain suitable rheological behavior for proces...Poly(vinyl alcohol)(PVA)is usually processed and used in a form of aqueous dispersion.A large number of inter-and intramolecular hydrogen bonds make it very difficult to obtain suitable rheological behavior for processing.In this study,carbon particles with different topological shapes were added into PVA aqueous dispersion to tune the steady and dynamic rheological behavior.The results show that the zero-dimensional particles(carbon black,CB)increase monotonically the zero-shear viscosity of PVA dispersion,while the one-dimensional particles(carbon nanotubes,CNTs)make it first increase,and then decrease and rise again,like an N-shape,and the two-dimensional particles(graphene oxide,GO)can make it first decrease and then increase,exhibiting a U-shape.It is believed that the topological shape of the carbon particles brought about these discrepancies.The zero-dimensional particles mainly act as physical crosslinking points due to their small size.While at a certain content,both CNTs and GO can destroy the intermolecular hydrogen bonds between PVA chains because the PVA chains can twine around the slim CNTs and the large planar size of GO prevents the adsorbed PVA from forming hydrogen bond with other chains.The high hydroxyl value of carbon particle surface could strengthen this effect.It is expected that the viscosity of polymer dispersion can be regulated by particles with different topological shape and the surface characteristic,so as to widen the operable concentration range during preparing composite functional materials.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51790503,52273084 and 51873181).
文摘Incorporation of carbon black(CB)in natural rubber(NR)enhances the Mullins effect and Payne effect of their vulcanizates,but the strain softening mechanisms and the microstructure evolution in the vulcanizates have not been clearly concluded so far.We investigate the Mullins effect and Payne effect of CB filled NR vulcanizates by using cyclic tensile tests at different temperatures and dynamic rheological measurements combined with simultaneous electric conduction.During cyclic stretching,the normalized recovery hysteresis energy and accumulative softening energy for NR/CB vulcanizates with different loadings can be both superimposed on a master curve,indicating that the Mullins effect is mainly dominated by the rubber matrix.The irreversible simultaneous resistance evolution also reveals that the structural evolution of nanoparticles(NPs)network is not directly related to the Mullins effect.Moreover,the extension of linear viscoelastic region and the hysteresis of Payne effect for filled vulcanizates subjected to cyclic stretching indicate the destruction of CB aggregated structure and the interfacial layers between CB and rubber chains during cyclic stretching.This investigation would be illuminating for the microstructure evolution and strain softening of rubber nanocomposites under harsh service conditions.
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financially supported by the National Natural Science Foundation of China(Nos.51173157 and 51173165)the Fundamental Research Funds for the Central Universities(No.2013QNA4048)
文摘We reported an approach to reconstruct the complex phase morphology of impact polypropylene copolymer （IPC） with core-shell dispersed particles and to optimize its toughness in approximate shear condition. The molten-state annealing results indicate that the phase structure with core-shell dispersed particles is unstable and could be completely destroyed by static annealing, resulting in the degradation of impact strength. By using a co-rotating twin screw extruder, we found that the dispersed particle with core-shell structure could be rebuilt in appropriate condition with the recovery of excellent impact strength due to both the huge interfacial tension during solidification and the great difference in viscosity of components. Results reveal that almost all the extruded IPCs show the impact strength 60%-90% higher than that of annealed IPCs at room temperature. And the twice-extruded IPC shows the highest impact strength, 446% higher than that of IPC annealed for 30 min. As for low temperature tests, the impact strength of extruded IPCs also increases by 33%-58%. According to adjusting the processing conditions including extrusion speed, extrusion frequency and temperature, an optimization of toughness was well established.
基金the National Natural Science Foundation of China(Nos.U1908221,51873190 and 51790503)the Fundamental Research Funds for the Central Universities(No.2020XZZX002-08).
文摘The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations.Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed.Herein carbon black(CB)filled isoprene rubber(IR)/liquid isoprene rubber(LR)blend nanocomposites with similar crosslink density(ve)are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated.The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes.Meanwhile,tuning ve and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances.The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.
基金financially supported by the National Natural Science Foundation of China(Nos.51790503 and 51873181)。
文摘As a widely used reinforcing filler of rubber, carbon black(CB) often enhances the nonlinear Payne effect and its mechanism still remains controversial. We adopt simultaneous measurement of rheological and electrical behaviors for styrene-butadiene rubber(SBR)/CB compounds and CB gel(CBG) during large deformation/recovery to investigate the contribution of conductive CB network evolution to the Payne effect of the compounds. In the highly filled compounds, the frequency dependence of their strain softening behavior is much more remarkable than that of their CB network breakdown during loading, while during unloading the unrecoverable filler network hardly affects the complete recovery of modulus, both revealing that their Payne effect should be dominated by the disentanglement of SBR matrix. Furthermore,the bound rubber adjacent to CB particles can accelerate the reconstruction of continuous CB network and improve the reversibility of Payne effect. This may provide new insights into the effect of filler network, bound rubber, and free rubber on the Payne effect of CB filled SBR compounds.
基金supported by the National Natural Science Foundation of China(No.51073136)the Fundamental Research Funds for the Central Universities of China(No.2010QNA4011)
文摘Polystyrene coated silica（SiO_2@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO_2 nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO_2@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO_2 and silane modified SiO_2 nanoparticles.Suspensions of the untreated and the silane modified SiO_2 exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO_2 at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.
基金supported by the National Natural Science Foundation of China(Nos.50773068 and 50473039)
文摘Modulated-temperature differential scanning calorimetric and dynamic mechanical analyses and dielectric spectroscopy were used to investigate the glass transition of hydrated wheat gliadin powders with moisture absorption ranged from 2.30 db% to 18.21 db%. Glass transition temperature （Tg） of dry wheat gliadin was estimated according to the Gordon- Taylor equation. Structural heterogeneity at high degrees of hydration was revealed in dielectric temperature and frequency spectra. The activation energies （Ea） of the two relaxations were calculated from Arrhenius equation.
基金financially supported by the National Natural Science Foundation of China(Nos.U1908221,51873190 and 51790503)the Fundamental Research Funds for the Central Universities(No.2020XZZX002-08)。
文摘Payne effect and its associated weak overshoot are of importance for understanding and regulating the softening of rubber nanocomposites under large amplitude oscillations.Herein,Payne effect in diverse filled vulcanizates is investigated for generalizing the common characteristics.Master curves of strain amplitude dependent storage modulus are created with respect to microscopic strain amplitude of the matrix,revealing a matrix-dominated elastic nonlinearity being independent of type and dispersity of filler,crosslinking density and sol fraction of matrix and filler-rubber interfacial interactions.However,carbonaceous fillers with higher affinity to the rubber matrices yield lower strain amplification and higher overshoot behavior in comparison with siliceous silica.The investigation would be illuminating for preparing rubber nanocomposites with optimized reinforcement and softening performances.
基金financially supported by the National Natural Science Foundation of China (Nos. 51873190, 51573157, and 51790503)
文摘Electric conductivity and rheological responses of colloidal electrolytes consisting of lithium bis(trifluoromethanesulfon)imide, polyethylene glycol(PEG) oligomer, and fumed silica have been investigated. Incorporating silica could improve ionic conductivity of the electrolytes at the same lithium/oxygen ratios. The colloidal electrolytes demonstrate a sol to gel transition with increasing silica content while they exhibit shear thickening behaviors during steady flow at intermediate range of strain rate. The presence of lithium salt, on the one hand, could lower the crystallinity of PEG or forbid the crystallization and on the other hand, interferes the chain adsorption on the surface of silica. Furthermore, lithium salt strongly retards the segmental relaxation of PEG in the colloidal electrolytes.
基金financially supported by the National Natural Science Foundation of China(No.51273173)the Fundamental Research Funds for the Central Universities(No.2017QNA4038)Zhejiang Natural Science Foundation(No.LY16E030001)
文摘The variation of phase morphology, critical temperature of demixing, and molecular dynamics for polystyrene/poly（vinyl methyl ether）（PS/PVME） blends induced by hydrophilic nanosilica（A200） or hydrophobic nanosilica（R974） was investigated. With the phase separation of blend matrix, A200 migrated into PVME-rich phase due to strong interaction between A200 and PVME, while R974 moved into PS-rich phase. The thermodynamic miscibility and concentration fluctuation during phase separation of blend matrix were remarkably retarded by A200 nanoparticles due to the surface adsorption of PVME on A200, verified by the correlation length ξ near the critical region from rheological measurement and the weakened increment of reversing heat capacity（ΔCp） during glass transition via modulated differential scanning calorimetry（MDSC）. The restricted chain diffusion induced by nanosilica still occurred despite no influence of A200 and R974 on the segmental dynamics of homogenous blend matrix. The interactions between nanosilica and polymer components could restrict the terminal relaxation of blend matrix and further manipulate their phase behavior.
基金financially supported by the National Natural Science Foundation of China(Nos.51873180,52173024 and 51673172)Zhejiang Provincial Natural Science Foundation of China(No.LGF20B040001)。
文摘Poly(vinyl alcohol)(PVA)is usually processed and used in a form of aqueous dispersion.A large number of inter-and intramolecular hydrogen bonds make it very difficult to obtain suitable rheological behavior for processing.In this study,carbon particles with different topological shapes were added into PVA aqueous dispersion to tune the steady and dynamic rheological behavior.The results show that the zero-dimensional particles(carbon black,CB)increase monotonically the zero-shear viscosity of PVA dispersion,while the one-dimensional particles(carbon nanotubes,CNTs)make it first increase,and then decrease and rise again,like an N-shape,and the two-dimensional particles(graphene oxide,GO)can make it first decrease and then increase,exhibiting a U-shape.It is believed that the topological shape of the carbon particles brought about these discrepancies.The zero-dimensional particles mainly act as physical crosslinking points due to their small size.While at a certain content,both CNTs and GO can destroy the intermolecular hydrogen bonds between PVA chains because the PVA chains can twine around the slim CNTs and the large planar size of GO prevents the adsorbed PVA from forming hydrogen bond with other chains.The high hydroxyl value of carbon particle surface could strengthen this effect.It is expected that the viscosity of polymer dispersion can be regulated by particles with different topological shape and the surface characteristic,so as to widen the operable concentration range during preparing composite functional materials.
