共查询到15条相似文献,搜索用时 15 毫秒
1.
P. A. Kakavas 《应用聚合物科学杂志》2000,77(3):660-672
The development of a new strain energy function for hyperelastic solids based on the logarithmic strain measure is the objective of the present article. For all possible types of deformation it was shown that the proposed energy function is based on three independent material parameters. Using available experimental data for rubber‐like materials from the literature, one may determined the materials parameters by a nonlinear fitting. The available domain of the strain energy function can be determined by plotting the third invariant of logarithmic strain vs the second one. The numerical integration of the experimental data of true stress as a function of the logarithmic strain for various types of deformation yields the strain energy function W, for rubber‐like solids. The proposed model involves only one parameter that must be determined by fitting with the experimental data. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 660–672, 2000 相似文献
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The torsional behaviour of 1, 3 and 5 phr peroxide crosslinked natural rubber has been characterized over a range of strains from near the undistorted state (γ ≈ 0.017) to γ ≈ 1.0. Isochronal measurements of both torque and normal force were used to calculate values of the derivatives of the strain energy function W with respect to the first and second stretch invariants I1 and I2. In the course of our work we found that, contrary to many reports in the literature, was affected significantly by the amount of crosslinking. Finally for the 1 phr peroxide crosslinked rubber it was found that, while ageing for 14 months at ambient conditions did not significantly affect the small-strain torsional modulus, , it did significantly affect the individual derivatives and . 相似文献
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Adhesive contact and rolling of a rigid cylinder under the pull of gravity on the underside of a smooth-surfaced sheet of rubber 总被引:1,自引:0,他引:1
The mechanical approach of the rolling contact of a rigid cylinder under the flat and smooth inclined surface of a natural rubber sample, if molecular attraction forces act, allows one to demonstrate, contrary to our first intuition, that the rolling of the cylinder occurs even if its weight per unit axial length is much greater than the critical value for the static equilibrium under a horizontal surface, as previously studied. It is shown that the maximum value of the rolling force per unit length is 50 times the static equilibrium force measured under a horizontal surface.
The rolling force varies as an n power function of the rolling speed and the value n = 0.55 previously determined in recent rebound and rolling experiments with the same rubber-like material is found again. Moreover, contact length measurements confirm theoretical predictions: the contact length varies as the n/3 = 0.183 power function of the rolling speed in a large range of velocities. 相似文献
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The devulcanization reaction of styrene–butadiene rubber (SBR) based ground tire rubber (GTR) in GTR/ethylene–propylene–diene monomer rubber (EPDM) blend was investigated through a compound‐induced reaction by increasing screw rotation speed and being in the presence of subcritical water. The effects of temperature, pressure, screw rotation speed, or promoting agents on the gel content, Mooney viscosity, and Fourier transform infrared spectra of the sol of the devulcanized blends (devulcanized ground tire rubber (DGTR)/EPDM) were measured, and the mechanical properties and microstructures of the revulcanized blend ((DGTR/EPDM)/SBR) were characterized. The results show that subcritical water as a swelling agent and reaction medium promotes the devulcanization reaction, increases the selectivity of the crosslink breakage, keeps the extrusion material from oxidative degradation, reduces the gel particle size of the devulcanized blends, and significantly improves the mechanical properties of the revulcanized SBR/(DGTR/EPDM) blends. In subcritical water, the suitable promoting agents (alkylphenol polysulfide 450, hydrogen peroxide H2O2, or 450/H2O2) accelerate the devulcanization reaction, keep the double bond content, and lead to further decrease of the gel content and Mooney viscosity of the devulcanized blends and further increase of the mechanical properties of the revulcanized SBR/(DGTR/EPDM) blends. Especially the compound promoting agent (450/H2O2) improves the selectivity of the crosslink breakage in devulcanization of SBR‐based GTR. When 450/H2O2 is added as a compound promoting agent at the best reaction condition in subcritical water (200°C, 1.6 MPa and 1000 rpm), the tensile strength and elongation at break of the revulcanized SBR/(DGTR/EPDM) blends reach to 85.4% and 201% of vulcanized SBR (24.0 MPa, 356%), respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1845–1854, 2013 相似文献
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The torsional behavior of poly(ether ester) (PEE) thermoplastic elastomer, based on poly(ethylene glycol) (PEG) and poly(butylene terephthalate) (PBT) was studied and compared with that of PBT itself. Two types of experiments were performed: (1) stress relaxation in torsion, and (2) measurement of intermittent couple-twist responses. It was shown that the relaxation of the torsional couple M could be represented as a sum of several exponential terms in the time, rather than as a simple exponential function. This sum might be called a Prony series on the analogy of the usual stress relaxation which occurs after stretching a sample to a certain deformation and holding it constant. The intermittent couple-twist experiments were carried out by analogy with similar experiments in elongation. For PEE the couple rises steadily with the twist, whereas for PBT it rises abruptly and remains constant within the experimental error for high twists. The residual twist, however, showed a similar trend for both PEE and PBT. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 495–502, 1998 相似文献
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Martin Traintinger Roman C. Kerschbaumer Michaela Hornbachner Bernhard Lechner Thomas Lucyshyn 《应用聚合物科学杂志》2024,141(6):e54901
Rubber compounds may exhibit significant batch variations due to multiple different ingredients mixed in one compound. Hence, defining the manufacturing process for constant part quality can be challenging. Common strategies in considering batch variations in rubber processing include the determination of reaction kinetics, and the definition of process parameters according to normalized vulcanization isotherms. Thereby, maintenance of the degree of cure is targeted. With this path, information on the mechanical properties of vulcanizates is lost, despite its visibility from the kinetic data and part quality assurance is missed. This contribution points out the differences obtained for parts produced to the same degree of cure at various temperatures and intends to emphasize new strategies in process definitions. Therefore, compression molded parts were produced from styrene-butadien rubber, which was then characterized with mechanical and chemical methods. Each of the methods revealed a significant difference in part behavior, which were manufactured to the same degrees of cure but at different temperatures. It was concluded that a temperature-dependent reaction rate should be considered when quality maintenance is targeted in the production. Only then will it be possible to predict the properties adequately, with simultaneous effect of enhancing sustainability policies in rubber processing. 相似文献
10.
T Takahashi H Suzuki T Inuzuka H Shibata M Maki 《International journal of molecular sciences》2012,13(6):7532-7549
ALG-2 is a penta-EF-hand Ca(2+)-binding protein and interacts with a variety of intracellular proteins. Two types of ALG-2-binding motifs have been determined: type 1, PXYPXnYP (X, variable; n = 4), in ALIX and PLSCR3; type 2, PXPGF, in Sec31A and PLSCR3. The previously solved X-ray crystal structure of the complex between ALG-2 and an ALIX peptide containing type 1 motif showed that the peptide binds to Pocket 1 and Pocket 2. Co-crystallization of ALG-2 and type 2 motif-containing peptides has not been successful. To gain insights into the molecular basis of type 2 motif recognition, we searched for a new hydrophobic cavity by computational algorithms using MetaPocket 2.0 based on 3D structures of ALG-2. The predicted hydrophobic pocket designated Pocket 3 fits with N-acetyl-ProAlaProGlyPhe-amide, a virtual penta-peptide derived from one of the two types of ALG-2-binding sites in PLSCR3 (type 2 motif), using the molecular docking software AutoDock Vina. We investigated effects of amino acid substitutions of the predicted binding sites on binding abilities by pulldown assays using glutathione-S-transferase -fused ALG-2 of wild-type and mutant proteins and lysates of cells expressing green fluorescent protein -fused PLSCR3 of wild-type and mutants. Substitution of either L52 with Ala or F148 with Ser of ALG-2 caused loss of binding abilities to PLSCR3 lacking type 1 motif but retained those to PLSCR3 lacking type 2 motif, strongly supporting the hypothesis that Pocket 3 is the binding site for type 2 motif. 相似文献
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A novel model based on a radial basis function neural network (RBF NN), chaos theory, self‐adaptive particle swarm optimization (PSO), and a clustering method is proposed to predict the gas solubility in polymers; this model is hereafter called CSPSO‐C RBF NN. To develop the CSPSO‐C RBF NN, the conventional PSO was modified with chaos theory and a self‐adaptive inertia weight factor to overcome its premature convergence problem. The classical k‐means clustering method was used to tune the hidden centers and radial basis function spreads, and the modified PSO algorithm was used to optimize the RBF NN connection weights. Then, the CSPSO‐C RBF NN was used to investigate the solubility of N2 in polystyrene (PS) and CO2 in PS, polypropylene, poly(butylene succinate), and poly(butylene succinate‐co‐adipate). The results obtained in this study indicate that the CSPSO‐C RBF NN was an effective method for predicting the gas solubility in polymers. In addition, compared with conventional RBF NN and PSO neural network, the CSPSO‐C RBF NN showed better performance. The values of the average relative deviation, squared correlation coefficient, and standard deviation were 0.1282, 0.9970, and 0.0115, respectively. The statistical data demonstrated that the CSPSO‐C RBF NN had excellent prediction capabilities with a high accuracy and a good correlation between the predicted values and the experimental data. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3825–3832, 2013 相似文献
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Rene Prieler Markus Mayrhofer Markus Eichhorn‐Gruber Günther Schwabegger Christoph Hochenauer 《火与材料》2019,43(1):34-50
In the present two‐parted study, a numerical approach is shown to consider fire resistance tests in virtual space, including the combustion, thermal analysis of the test specimen, and the deformation process. This part is dealing with the combustion process and thermal analysis of different building materials tested in a fire resistance furnace. Instead of using coupled computational fluid dynamics (CFD)/finite element method simulation for the combustion and thermal heat conduction in the solid, which is commonly used in literature, the present approach considers these transport phenomena in one CFD simulation. This method enables a two‐way coupling between the gas phase and the solid material, where chemical reactions and the release of volatile components into the gas phase can occur (eg, release of water vapour from gypsum). To validate the numerical model, a fire resistance test of a steel door, which is a multilayer construction, and a wall made of gypsum blocks were experimentally and numerically investigated. Due to the chemical reactions inside the gypsum, water vapour is released to the gas phase reducing the flue gas temperature about 80 K. This effect was taken into account using a two‐way coupling in the CFD model, which predicted temperatures in close accordance to the measurement. 相似文献
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Effects of the reagent molar ratio on the phase separation and properties of waterborne polyurethane for application in a water‐based ink binder 下载免费PDF全文
Waterborne polyurethane (WPU) dispersions with a high solid content and low viscosity were prepared successfully by a two‐step polymerization with isophorone diisocyanate, poly(propylene glycol), and dimethylol propionic acid as the main raw materials. The molar ratio of hard segments to soft segments was controlled to investigate its influence on the particle size, particle morphology, stability of dispersions, and final properties of the WPU films. Measurements including attenuated total reflectance/Fourier transform infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, X‐ray diffraction, polarizing optical microscopy, and contact angle tests were used to characterize the bulk structures, phase separation, thermal stability, crystallinity, and wettability of the WPU dispersions. The results indicate that all of the WPU dispersions with a high solid content (ca. 40 wt %) and low viscosity (ca. 20–50 mPa s) displayed excellent stability. The prepared WPU dispersions with acetone contents of 5–7 wt % could be used directly as an ink binder without removing the acetone; this is beneficial to industrial applications of water‐based ink binders. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45406. 相似文献
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Katerina Setnickova Zdeněk Wagner Richard D. Noble Petr Uchytil 《Chemical engineering science》2011,(22):5566
Solubility, diffusivity and permeability of toluene vapors in low-density polyethylene (LDPE) membranes of various thicknesses (approximately 48, 93, 138 and 187 μm) at different temperatures 30, 40 and 50 °C in the range of relative vapor pressure p/p0=(0.05; 0.95) were measured using new type of permeation apparatus. Moreover, special construction of the new cell enables determination of the permeant amount sorbed in the membrane in the steady state operation of vapor permeation.The simple semi-empirical model of toluene transport in a polyethylene membrane based on relation between experimentally obtained effective diffusion coefficients and concentration dependent diffusion coefficients evaluated from experiments on a new permeation apparatus was proposed. The model enables estimation of toluene fluxes, sorption in the steady state of vapor permeation and concentration profiles in a polyethylene membrane from equilibrium sorption isotherms and effective diffusion coefficients. Very good agreement between experimental and calculated values from the proposed model was obtained. 相似文献
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Brandt W Dessoy MA Fulhorst M Gao W Zenk MH Wessjohann LA 《Chembiochem : a European journal of chemical biology》2004,5(3):311-323
Experimental and theoretical investigations concerning the second-to-last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants are reported. The proposed intrinsic or late intermediates 4-oxo-DMAPP (12) and 4-hydroxy-DMAPP (11) were synthesized in deuterium- or tritium-labeled form according to new protocols especially adapted to work without protection of the diphosphate moiety. When the labeled compounds MEcPP (7), 11, and 12 were applied to chromoplast cultures, aldehyde 12 was not incorporated. This finding is in agreement with a mechanistic and structural model of the responsible enzyme family: a three-dimensional model of the fragment L271-A375 of the enzyme GcpE of Streptomyces coelicolor including NADPH, the Fe(4)S(4) cluster, and MEcPP (7) as ligand has been developed based on homology modeling techniques. The model has been accepted by the Protein Data Bank (entry code 1OX2). Supported by this model, semiempirical PM3 calculations were performed to analyze the likely catalysis mechanism of the reductive ring opening of MEcPP (7), hydroxyl abstraction, and formation of HMBPP (8). The mechanism is characterized by a proton transfer (presumably from a conserved arginine 286) to the substrate, accompanied by a ring opening without high energy barriers, followed by the transfer of two electrons delivered from the Fe(4)S(4) cluster, and finally proton transfer from a carboxylic acid side chain to the hydroxyl group to be removed from the ligand as water. The proposed mechanism is in agreement with all known experimental findings and the arrangement of the ligand within the enzyme. Thus, a very likely mechanism for the second to last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants is presented. A principally similar mechanism is also expected for the reductive dehydroxylation of HMBPP (8) to IPP (9) and DMAPP (10) in the last step. 相似文献