Correlation between mechanical properties and microscopic structures of an optimized silica fraction in silicone rubber
Dong LiuLixian SongHongtao SongJie ChenQiang TianLiang ChenLiangwei SunA. LuChaoqiang HuangGuangai Sun
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Silicone rubber
Radius of gyration
Volume fraction
Radius of gyration
Gyration
Hydrodynamic radius
Stokes radius
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We report on a light scattering study performed on suspensions of aggregates of PVC and chemically-modified PVCs in diethyloxalate (DEO). The maximum in the scattering function reported by Mutin and Guenet is again observed. Its position, qm, depends upon the degree of chemical modification at constant polymer concentration: the larger the degree of modification, the lower the value of qm. The radius of gyration and the weight-averaged molecular weight of the aggregates are determined as a function of the preparation concentration from highly diluted suspensions. The radius of gyration is found to remain virtually unchanged when augmenting the degree of modification while a near 2-fold increase of the weight-averaged molecular weight is observed, the latter being consistent with the variation of qm. All these results point toward a cross-sectional growth of the fibrillar aggregates with chemical modification while the longitudinal fractal dimension does not vary significantly. Viscometry measurements provide further support to these conclusions.
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Hydrodynamic radius
Chemical modification
Gyration
Degree (music)
Molar mass distribution
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The following paper indicates variants of new materials obtained with various organic alloy elements. Our research has used recoverable silicone rubber, obtained from used scrapped silicone rubber, used for the tyre of 24 kV composite electrical insulators as a basic matrix, under the form of silicone powder, liquid silicone rubber to various proportions, along with nanopowders obtained through recycling
Silicone rubber
Matrix (chemical analysis)
Silicone Elastomers
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Large-scale modelling of short-fibre metal-loaded composites is described. The aim was to establish the relationship between fibre aspect ratio (A) and the critical volume fraction (Vc ) at which conductivity via a percolation mechanism occurs. For typical geometries, Vc was found to be proportional to (I/A)1 · 5 for 50 A 500. This gave good agreement with a first-order theoretical model (which predicts a I/A dependence for Vc ) for 150 A 500.
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Percolation (cognitive psychology)
Aspect ratio (aeronautics)
Percolation Theory
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Electrical and mechanical characterization of carbon nanotube (CNT) reinforced composites has long drawn the attention of researchers. Electrical conductivity of CNTs accounts for electrical properties of their composites. Conductivity of insulating polymers is achieved at relatively low volume fractions of CNTs. The lowest volume fraction of CNTs required for conductivity is called percolation threshold. This threshold is affected by the mechanical loading of the composite. In this computer study, the CNT sticks are scattered randomly within a sample block using the algorithm of Monte-Carlo. Subjected to mechanical loading, the sticks are displaced using the method of Mori-Tanaka. Then the diagrams of mechanical strain versus volume fraction at percolation threshold are drawn. The results show that by applying tensile stresses the percolation can be achieved at lower volume fractions compared to the unloaded state.
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Percolation (cognitive psychology)
Percolation Theory
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The spatial distribution of the terminal groups of poly(amido amine) dendrimers have been determined experimentally by small-angle neutron scattering with deuterium labeling and scattering contrast variation. The radius of gyration of deuterated terminal units of generation 7 dendrimers is 39.3 ± 1.0 Å. This is significantly larger than the radius of gyration of the whole dendrimer, which is 34.4 ± 0.2 Å. These data indicate that dendrimers have terminal groups that are concentrated near the periphery. These results are inconsistent with many computer simulations and some molecular models.
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Gyration
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Abstract The three-dimensional aggregated structure of carbon black in elastomer blends behaves in a similar fashion to that of the individual elastomers. The elastomer seems to act merely as a dispersing medium. The properties of the rubber reflect the structural effects of the filler superimposed upon the elastomer itself. The elastomer molecules no doubt retain their individual characteristics of rotation of bonds which govern the stiffness of the molecule. However, the superimposed carbon-black network exerts the predominant effect, as far as the low-strain dynamic characteristics are concerned. The polymeric medium seems to influence this interaction by determining the magnitude of agglomeration and distribution of black in the phases, but does not have visible influence on the overall characteristics of the carbon-black networks. In this respect blends of two elastomers behave as a single elastomer. The importance of the present work is that the strain-dependent dynamic properties of blends of elastomers are very similar to those of single elastomers. In tires and antivibration applications, the strain imposed is usually less than 10%. More and more blends of elastomers are being used for these applications. The filler structure and its breakdown at these strains have an important contribution to hardness, modulus, and hysteresis of these compounds.
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Carbon fibers
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The mechanical properties and the conductivity of silicone rubber composite filled with silver-coated glass beads were investigated in this paper.It was found that the mechanical properties of the composite were getting bad with the increase of addition of silver-coated glass beads,and the volume resistivity of the composite decreased,When the volume fraction of silve-coated glass beads was 38.8%,the composite transformed from the insulator into conductor,and presented an obvious percolation threshold.There was a slight inflexion in the curve of volume resistivity at the volume fraction was 46%.The existence of percolation threshold of the composite had much to do with the formation of rubber conductive net.
Silicone rubber
Volume fraction
Percolation (cognitive psychology)
Glass microsphere
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Radius of gyration
Hydrodynamic radius
Gyration
Static light scattering
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Abstract In this work, a self‐avoiding Monte‐Carlo off‐lattice 3D random walk model that is able to predict the configuration of linear and branched carbon‐based macromolecules, taking into account: i) the bond length, ii) the carbon‐carbon angle, and, iii) steric interferences, is presented. The methodology follows the theoretical framework proposed by the pioneering work of P. J. Flory. The Monte‐Carlo model developed is being validated based on experimental results of radius of gyration coming from linear polyethylene characterization by size exclusion chromatography multiangle light scattering (SEC‐MALS) technique. The most detailed version of the model manages to reach an accuracy level of 80% with regard to radius of gyration, without any tuning procedure involved. Furthermore, considering the solvent effect, the accuracy level reaches a value of 95%. On the contrary, it is shown that the simplest Monte Carlo random walk model version (including only the bond length restriction) is not able to quantitatively predict the experimentally acquired values of radius of gyration. Moreover, the developed Monte Carlo model is further employed to predict the expected radius of gyration values of more complex branched topologies, demonstrating the potential of this work.
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Gyration
Monte Carlo algorithm
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