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Qiang Zheng - One of the best experts on this subject based on the ideXlab platform.
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influence of coagents on Payne Effect of butadiene rubber vulcanizates
Polymer, 2021Co-Authors: Xinke Zhong, Yihu Song, Qiang Zheng, Wanjie WangAbstract:Abstract Gum vulcanizates exhibit Payne Effect and weak strain overshooting behavior, which is usually forgot in rubber industry. Herein the Payne Effect of butadiene rubber (BR) vulcanizates is investigated for clarifying the Effect of crosslinking density and sol content mediated by using coagent in conjugation with dicumyl peroxide. Toluene extraction and paraffin swelling of the vulcanizates are performed for clarifying the contribution of sol fraction and chains entanglement. The results show that the Payne Effect and weak strain overshooting of gum vulcanizates are closely related to Effective crosslinking density rather than network defects. This work is helpful for understanding the nonlinear rheological responses of the gum vulcanizates with defective network structure.
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Payne Effect of thermo oxidatively aged isoprene rubber vulcanizates
Polymer, 2020Co-Authors: Fengyi Hou, Yihu Song, Qiang ZhengAbstract:Abstract While many works focus on aging mechanisms and mechanical performances of aged vulcanizates, rare is performed to investigate the influences of aging induced network variation on the Payne Effect and energy dissipation. Herein the influence of thermo-oxidative aging on Payne Effect of isoprene rubber (IR) gum vulcanized with conventional vulcanization (CV) and efficient vulcanization (EV) systems at similar crosslinking densities was investigated, in order to disclose the roles of the crosslink types and therefore the thermo-oxidative degradation on the Payne Effect. The results indicate that the crosslink structure and thus the Payne Effect are highly susceptible to the thermo-oxidative aging. The aging induced degradation is more severe in CV than that in EV systems, which greatly improves the dissipation of accompanying the Payne Effect. This work is helpful for understanding the contribution of network structure to the Payne Effect for design rubber materials with optimized aging and dynamic properties.
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influences of chemical crosslinking physical associating and filler filling on nonlinear rheological responses of polyisoprene
Journal of Rheology, 2020Co-Authors: Xinpeng Fan, Yihu Song, Qiang ZhengAbstract:Chemical crosslinking, physical associating, and filler filling play vital roles in nonlinear responses of rubbers under large amplitude oscillatory shear (LAOS). Herein, a systematical investigation was performed for polyisoprene rubber vulcanizates and compounds on the framework of LAOS analytical methods to quantify intra- and intercycle nonlinearities. It is shown that the Payne Effect is featured by intercycle strain softening and intracycle hardening. Furthermore, chemical crosslinking and intermolecular association cause marked shear thickening at the medium range of rate amplitude, which is related to the nonideally crosslinked structures from numerical studies. Fillers can promote nonlinear viscoelastic behaviors. In compounds, modulus recovery during cyclic oscillatory shear deformation is not directly related to the reorganization of the filler phase, which is testified by simultaneous measurements of rheological responses and electrical resistivity during increasing-decreasing amplitude sweep cycles.
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influence of ionic liquids on rheological behaviors of polyisoprene rubber silica compounds
Polymer, 2019Co-Authors: Qiang Zheng, Yihu SongAbstract:Abstract Ionic liquids (ILs), 1-allyl-3-methyl-imidazolium chloride (AMIC) and 1-decyl-3-methyl-imidazolium chloride (DMIC), are used to pretreat hydrophilic fumed silica. Their influence on rheological responses of silica filled isoprene rubber (IR) compounds is investigated. The presence of ILs causes silica to form large agglomerates in the IR matrix, lowers bound rubber content, and prevents the formation of glassy fraction of IR chains. In the low filling compounds, ILs at low contents could lower reinforcement efficiency of silica, improve loss factor and promote the macromolecular diffusion. For the highly-filled compounds, ILs are able to improve the reinforcement efficiency on the one hand and intensify the weak strain overshoot accompanying the Payne Effect on the other hand. Nevertheless, ILs do not influence strain amplification Effect induced by silica.
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Rigid nanoparticles promote the softening of rubber phase in filled vulcanizates
Polymer, 2019Co-Authors: Yihu Song, Xinyan Shi, Ruiquan Yang, Qiang ZhengAbstract:Abstract Enhanced mechanical softening accompanying nanoparticles reinforcement of rubber is an important source of energy dissipation and heat buildup of industrially engineered elastomers. Its mechanism previously assigned to damages in the filler network, rubber-filler interface and rubber phase remains controversial in more than 70 years. Through investigating the typical Payne Effect of styrene-butadiene rubber gum and its vulcanizates as well as silica filled compounds and vulcanizates and the Mullins Effect of unfilled and filled vulcanizates, we herein evidence that the filler-promoted softening of the rubber phase softens the filled elastomer nanocomposites. Especially we show that the Mullins Effect is relevantly involved in the disentanglement/re-entanglement of dangling chains superposed on the entropically elastic network of the rubber phase. This paper clarifies that the mechanism of nonlinear mechanical softening for filled rubber compounds and vulcanizates should be rooted in macromolecular chains in the entanglement network (gum and filled compounds) or long dangling chain in non-ideally crosslinked network (vulcanized gum and filled vulcanizates), rather than damages involved in the “filler network” or filler-rubber interface. This suggests that adjusting the nonideally crosslinked network structure of viscoelastic rubber matrix should be able to optimize the use performance of the rubber nanocomposite products.
Yihu Song - One of the best experts on this subject based on the ideXlab platform.
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influence of coagents on Payne Effect of butadiene rubber vulcanizates
Polymer, 2021Co-Authors: Xinke Zhong, Yihu Song, Qiang Zheng, Wanjie WangAbstract:Abstract Gum vulcanizates exhibit Payne Effect and weak strain overshooting behavior, which is usually forgot in rubber industry. Herein the Payne Effect of butadiene rubber (BR) vulcanizates is investigated for clarifying the Effect of crosslinking density and sol content mediated by using coagent in conjugation with dicumyl peroxide. Toluene extraction and paraffin swelling of the vulcanizates are performed for clarifying the contribution of sol fraction and chains entanglement. The results show that the Payne Effect and weak strain overshooting of gum vulcanizates are closely related to Effective crosslinking density rather than network defects. This work is helpful for understanding the nonlinear rheological responses of the gum vulcanizates with defective network structure.
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Payne Effect of thermo oxidatively aged isoprene rubber vulcanizates
Polymer, 2020Co-Authors: Fengyi Hou, Yihu Song, Qiang ZhengAbstract:Abstract While many works focus on aging mechanisms and mechanical performances of aged vulcanizates, rare is performed to investigate the influences of aging induced network variation on the Payne Effect and energy dissipation. Herein the influence of thermo-oxidative aging on Payne Effect of isoprene rubber (IR) gum vulcanized with conventional vulcanization (CV) and efficient vulcanization (EV) systems at similar crosslinking densities was investigated, in order to disclose the roles of the crosslink types and therefore the thermo-oxidative degradation on the Payne Effect. The results indicate that the crosslink structure and thus the Payne Effect are highly susceptible to the thermo-oxidative aging. The aging induced degradation is more severe in CV than that in EV systems, which greatly improves the dissipation of accompanying the Payne Effect. This work is helpful for understanding the contribution of network structure to the Payne Effect for design rubber materials with optimized aging and dynamic properties.
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influences of chemical crosslinking physical associating and filler filling on nonlinear rheological responses of polyisoprene
Journal of Rheology, 2020Co-Authors: Xinpeng Fan, Yihu Song, Qiang ZhengAbstract:Chemical crosslinking, physical associating, and filler filling play vital roles in nonlinear responses of rubbers under large amplitude oscillatory shear (LAOS). Herein, a systematical investigation was performed for polyisoprene rubber vulcanizates and compounds on the framework of LAOS analytical methods to quantify intra- and intercycle nonlinearities. It is shown that the Payne Effect is featured by intercycle strain softening and intracycle hardening. Furthermore, chemical crosslinking and intermolecular association cause marked shear thickening at the medium range of rate amplitude, which is related to the nonideally crosslinked structures from numerical studies. Fillers can promote nonlinear viscoelastic behaviors. In compounds, modulus recovery during cyclic oscillatory shear deformation is not directly related to the reorganization of the filler phase, which is testified by simultaneous measurements of rheological responses and electrical resistivity during increasing-decreasing amplitude sweep cycles.
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influence of ionic liquids on rheological behaviors of polyisoprene rubber silica compounds
Polymer, 2019Co-Authors: Qiang Zheng, Yihu SongAbstract:Abstract Ionic liquids (ILs), 1-allyl-3-methyl-imidazolium chloride (AMIC) and 1-decyl-3-methyl-imidazolium chloride (DMIC), are used to pretreat hydrophilic fumed silica. Their influence on rheological responses of silica filled isoprene rubber (IR) compounds is investigated. The presence of ILs causes silica to form large agglomerates in the IR matrix, lowers bound rubber content, and prevents the formation of glassy fraction of IR chains. In the low filling compounds, ILs at low contents could lower reinforcement efficiency of silica, improve loss factor and promote the macromolecular diffusion. For the highly-filled compounds, ILs are able to improve the reinforcement efficiency on the one hand and intensify the weak strain overshoot accompanying the Payne Effect on the other hand. Nevertheless, ILs do not influence strain amplification Effect induced by silica.
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Rigid nanoparticles promote the softening of rubber phase in filled vulcanizates
Polymer, 2019Co-Authors: Yihu Song, Xinyan Shi, Ruiquan Yang, Qiang ZhengAbstract:Abstract Enhanced mechanical softening accompanying nanoparticles reinforcement of rubber is an important source of energy dissipation and heat buildup of industrially engineered elastomers. Its mechanism previously assigned to damages in the filler network, rubber-filler interface and rubber phase remains controversial in more than 70 years. Through investigating the typical Payne Effect of styrene-butadiene rubber gum and its vulcanizates as well as silica filled compounds and vulcanizates and the Mullins Effect of unfilled and filled vulcanizates, we herein evidence that the filler-promoted softening of the rubber phase softens the filled elastomer nanocomposites. Especially we show that the Mullins Effect is relevantly involved in the disentanglement/re-entanglement of dangling chains superposed on the entropically elastic network of the rubber phase. This paper clarifies that the mechanism of nonlinear mechanical softening for filled rubber compounds and vulcanizates should be rooted in macromolecular chains in the entanglement network (gum and filled compounds) or long dangling chain in non-ideally crosslinked network (vulcanized gum and filled vulcanizates), rather than damages involved in the “filler network” or filler-rubber interface. This suggests that adjusting the nonideally crosslinked network structure of viscoelastic rubber matrix should be able to optimize the use performance of the rubber nanocomposite products.
Gert Heinrich - One of the best experts on this subject based on the ideXlab platform.
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benefits of hybrid nano filler networking between organically modified montmorillonite and carbon nanotubes in natural rubber experiments and theoretical interpretations
Applied Clay Science, 2017Co-Authors: Aleksandra Ivanoskadacikj, Srecko Valic, Sven Wiesner, Gordana Bogoevagaceva, Gert HeinrichAbstract:Abstract In this paper some new aspects to the hybrid nano-filler networking in elastomer matrix under dynamic mechanical loading conditions and some new methods to reveal a hybrid nano-filler synergy are applied and discussed. Electron spin resonance (ESR) spectra of the multi-walled carbon nanotubes (MWCNT) present in the natural rubber (NR) based nanocomposites were investigated and the dependence of the double integral of resonance spectra on the amount of expanded organically modified montmorillonite (EOMt) present in the NR was established. Its decrease with an increasing amount of EOMt confirmed the synergy between these two nano-fillers. DMA temperature sweep measurements were performed and the cluster-cluster aggregation (CCA) model was used to assess the apparent filler networking energy. The obtained results suggest that the presence of the EOMt above a critical amount strengthens the hybrid-filler networking. In order to investigate how different ratios of these two nano-fillers influence the strain dependency of the storage modulus, strain sweep measurements were performed in tensile mode, and the CCA-model was used to describe the Payne Effect.
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benefits of hybrid nano filler networking between organically modified montmorillonite and carbon nanotubes in natural rubber experiments and theoretical interpretations
Applied Clay Science, 2017Co-Authors: Aleksandra Ivanoskadacikj, Srecko Valic, Sven Wiesner, Gordana Bogoevagaceva, Gert HeinrichAbstract:Abstract In this paper some new aspects to the hybrid nano-filler networking in elastomer matrix under dynamic mechanical loading conditions and some new methods to reveal a hybrid nano-filler synergy are applied and discussed. Electron spin resonance (ESR) spectra of the multi-walled carbon nanotubes (MWCNT) present in the natural rubber (NR) based nanocomposites were investigated and the dependence of the double integral of resonance spectra on the amount of expanded organically modified montmorillonite (EOMt) present in the NR was established. Its decrease with an increasing amount of EOMt confirmed the synergy between these two nano-fillers. DMA temperature sweep measurements were performed and the cluster-cluster aggregation (CCA) model was used to assess the apparent filler networking energy. The obtained results suggest that the presence of the EOMt above a critical amount strengthens the hybrid-filler networking. In order to investigate how different ratios of these two nano-fillers influence the strain dependency of the storage modulus, strain sweep measurements were performed in tensile mode, and the CCA-model was used to describe the Payne Effect.
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modified and unmodified multiwalled carbon nanotubes in high performance solution styrene butadiene and butadiene rubber blends
Polymer, 2008Co-Authors: Klaus Werner Stöckelhuber, René Jurk, Marina Saphiannikova, J Fritzsche, H Lorenz, M Kluppel, Gert HeinrichAbstract:Abstract The outstanding properties of carbon nanotubes have generated scientific and technical interests in the development of nanotube-reinforced polymer composites. Therefore, we investigated a novel mixing approach for achieving a good dispersion of multiwalled carbon nanotubes (CNTs) in a rubber blend. In this approach the CNTs were incorporated into a 50:50 blend of solution-styrene–butadiene rubber and butadiene rubber. First, the CNTs were predispersed in ethanol and then this CNT–alcohol suspension was mixed with the rubber blend at elevated temperature. The rubber nanocomposites prepared by such method exhibit significantly enhanced physical properties already at very low nanotube concentrations. Additionally, we have analysed the dielectric and thermal properties of the compound. The high aspect ratio of the carbon nanotubes enabled the formation of a conductive percolating network in these composites at concentrations below 2 wt.%. In contrast to the electrical conduction behaviour, the thermal conductivity of the composites has not been influenced significantly by the presence of carbon nanotubes. Dynamic mechanical analysis indicates that the incorporation of CNTs affects the glass transition behaviour by reducing the height of the tan δ peak considerably. Above the glass transition temperature the storage modulus has been increased after incorporation of a small amount of CNTs. Finally, the ‘Payne Effect’, an indication of filler–filler interactions, was observed at very low concentrations of CNT in the rubber matrix.
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recent advances in the theory of filler networking in elastomers
Advances in Polymer Science, 2002Co-Authors: Gert Heinrich, Manfred KluppelAbstract:The viscoelastic properties of (mostly carbon black) filled elastomers are reviewed with emphasis on the strain-dependence of the complex dynamic modulus (Payne Effect). Considerable progress has been made in the past in relating the typical dynamical behavior at low strain amplitudes to a cyclic breakdown and reagglomeration of physical filler-filler bonds in typical clusters of varying size, including the infinite filler network. Common features between the phenomenological agglomeration/deagglomeration Kraus approach and very recent semi-microscopical networking approaches (two aggregate VTG model, links-nodes-blobs model, kinetical cluster-cluster aggregation) are discussed. All semi-microscopical models contain the assumption of geometrical arrangements of sub-units (aggregates) in particular filler network structures, resulting for example from percolation or kinetical cluster-cluster aggregation. These concepts predict some features of the Payne Effect that are independent of the specific types of filler. These features are in good agreement with experimental studies. For example, the shape exponent m of the storage modulus, G′, drop with increasing deformation is determined by the structure of the cluster network. Another example is a scaling relation predicting a specific power law behavior of the elastic modulus as a function of the filler volume fraction. The exponent reflects the characteristic structure of the fractal filler clusters and of the corresponding filler network. The existing concepts of the filler network breakdown and reformation appear to be adequate in describing the deformation-dependence of dynamic mechanical properties of filled rubbers. The different approaches suggest in a common manner that there is a change of filler structure with increasing dynamic strain. However, in all cases additional assumptions are made about the accompanying energy dissipation process, imparting higher hysteresis to the filled rubber. This process may be slippage of entanglements (slip-links) in the transition layer between bound rubber layer and mobile rubber phase, and/or partially release of elastically ‘dead’ immobilized rubber trapped within the filler network or agglomerates.
Jacques W.m. Noordermeer - One of the best experts on this subject based on the ideXlab platform.
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Silane grafted natural rubber and its compatibilization Effect on silica-reinforced rubber tire compounds
Budapest University of Technology, 2017Co-Authors: K. Sengloyluan, Wilma K. Dierkes, Kannika Sahakaro, Jacques W.m. NoordermeerAbstract:Natural Rubber (NR) grafted with 3-octanoylthio-1-propyltriethoxysilane (NXT) was prepared by melt mixing using 1,1′-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane as initiator at 140 °C with NXT contents of 10 and 20 parts per hundred rubber [phr] and initiator 0.1 phr. The silane grafted on NR molecules was confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX). Based on 1H-NMR, the use of 10 and 20 phr (parts per hundred resin) of silane resulted in grafted NXT onto NR of 0.66 and 1.32 mol%, respectively, or a grafting efficiency of approx. 38%. The use of NXT-grafted NR as compatibilizer in silica-filled NR compounds, to give a total amount of NXT in both grafted and non-grafted forms in the range of 0.8–6.1 wt% relative to the silica, decreases the Mooney viscosity and Payne Effect of the compounds, improves filler-rubber interaction, and significantly increases the tensile properties of the silica-filled NR-compounds compared to the non-compatibilized one. At the same silane-content, the use of silane-grafted NR gives slightly better properties than the straight use of the same silane. With sulfur compensation, the use of NXT-grafted-NR with about 6 wt% NXT relative to the silica gives technical properties that reach the levels obtained for straight use of bis-(3-triethoxysilyl-propyl)tetrasulfide (TESPT) at 8.6 wt% relative to the silica
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Property Enhancement of Silica-filled Natural Rubber Compatibilized with Epoxidized Low Molecular Weight Rubber by Extra Sulfur
2016Co-Authors: Prachid Saramolee, Wilma K. Dierkes, Kannika Sahakaro, Natinee Lopattananon, Jacques W.m. NoordermeerAbstract:The properties of both compounds and vulcanizates of silica-filled natural rubber (NR) compatibilized with epoxidized low molecular weight natural rubbers (ELMWNRs) consisting of 12 and 28 mol % epoxide are investigated. The ELMWNRs with a molecular weight range of 50,000 to 60,000 g/mol are produced by depolymerization of epoxidized natural rubber (ENR) latex using periodic acid, and then used as compatibilizer in a range of 0 to 15 phr in virgin NR. The compounds with LMWNR without epoxide groups, and with bis-(triethoxysilylpropyl) tetrasulfide (TESPT) coupling agent are also prepared for comparison purpose. Incorporation of ELMWNRs lowers Mooney viscosity and Payne Effect to the level closed to that of silica/TESPT compound, and clearly enhances the modulus and tensile strength of vulcanizates compared to the compounds with no compatibilizer and LMWNR. The higher epoxide groups content results in the better tensile properties but somewhat less than the compound with TESPT. Addition of extra sulfur into the compounds with LMWNR and ELMWNRs to compensate for the sulfur released from silane molecule in the silica/TESPT system shows small influence on Mooney viscosity, but remarkably enhances 300 % modulus, tensile strength and loss tangent at 60oC as a result of the better network formation
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silica reinforced tire tread compounds compatibilized by using epoxidized natural rubber
European Polymer Journal, 2014Co-Authors: Wilma K. Dierkes, Kannika Sahakaro, K. Sengloyluan, Jacques W.m. NoordermeerAbstract:Silica-reinforced natural rubber (NR) tire tread compounds with epoxidized natural rubber (ENR) as a compatibilizer are investigated. The ENRs consisting of 10, 38 and 51 mole% epoxide are used in a range of 2.5–15.0 parts per hundred parts of rubber (phr). The addition of ENRs, especially ENR-38 and ENR-51, decreases the Mooney viscosity, Payne Effect, flocculation rate constant and filler networking factor, which implies an improvement of silica dispersion in the compounds. Chemically bound rubber contents and interaction parameters of the compounds also increase with higher epoxide-contents of the ENRs, indicating more interactions and/or reaction between the epoxide-groups of the ENR and silanol groups on the silica surface. Tensile strength of the vulcanizates is improved with increasing mole% epoxide, and the optimum value is observed at 7.5 phr of ENR-51. The overall results show that silica-reinforced NR can be substantially improved by adding ENR as a compatibilizer, when compared to a compound without ENR, but somewhat less than with using a silane coupling agent.
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Elucidation of filler-to-filler and filler-to-rubber interactions in silica-reinforced natural rubber by TEM Network Visualization
European Polymer Journal, 2014Co-Authors: Siti Salina Sarkawi, Wilma K. Dierkes, Jacques W.m. NoordermeerAbstract:Filler-to-rubber interaction is a key parameter in the reinforcement of rubber. This paper presents an investigation into filler-to-filler and filler-to-rubber interactions in silica-reinforced natural rubber (NR) in the presence and absence of a silane coupling agent. Using a special network visualization technique based on Transmission Electron Microscopy (TEM), insight into the silica and rubber interaction in NR is gained. In absence of silane, vacuoles around the silica particles are formed as a result of a weak filler-to-rubber interaction, while the presence of silane leads to strong filler-to-rubber bonding, which prevents formation of vacuoles. Further, the relationship between the filler-to-rubber interaction as seen from TEM images and bound rubber and Payne Effect is discussed
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optimization of rubber formulation for silica reinforced natural rubber compounds
Rubber Chemistry and Technology, 2013Co-Authors: Wisut Kaewsakul, Kannika Sahakaro, Wilma K. Dierkes, Jacques W.m. NoordermeerAbstract:The rubber formulation plays a significant role in the properties of NR compounds filled with silica. In this work, the influences of various silicas, silane coupling agents, and diphenylguanidine (DPG) on the properties of compounds and vulcanizates—that is, cure characteristics, Mooney viscosity, flocculation kinetics, bound rubber content, Payne Effect, tan δ at 60°C, tensile properties, and tear properties—are investigated. The results demonstrate that compound viscosity and curing behavior, as well as vulcanizate properties of the silica-filled NR, are much improved by incorporating silane coupling agents. Bis-triethoxysilylpropyltetrasulfide clearly gives better overall properties than the disulfide-based silane bis-triethoxysilylpropyldisulfide, except for scorch safety. DPG acts as a synergist to sulfenamide primary accelerators, as well as activator for the silanization reaction. Highly dispersible (HD) silicas can significantly enhance the degree of dispersion and so lead to higher filler–rubber interaction. As a consequence, the HD silicas provide better dynamic and mechanical properties for filled NR vulcanizates compared with conventional counterparts. The optimal quantities of both silane coupling agent and DPG required in the formulation are correlated to the cetyl trimethylammonium bromide specific surface area of the silicas. Furthermore, the results reveal that the silica structure as characterized by the dibutylphthalate adsorption also strongly influences the reinforcing efficiency
Sabu Thomas - One of the best experts on this subject based on the ideXlab platform.
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Morphology, Mechanical and Thermal Properties of Thermoplastic Polyurethane Containing Reduced Graphene Oxide and Graphene Nanoplatelets
MDPI AG, 2018Co-Authors: Michał Strankowski, Piotr Korzeniewski, Justyna Strankowska, Anu A. S., Sabu ThomasAbstract:Polyurethane/graphene nanocomposites were synthesized using commercial thermoplastic polyurethane (TPU, Apilon 52DE55), and two types of graphene derivatives: graphene nanoplatelets (GNP) and reduced graphene oxide (RGO). Fourier Transformation Infrared Spectroscopy Fourier Transformation Infrared Spectroscopy (FTIR) spectroscopy, TEM, and SEM microscopy and XRD techniques were used to chemically and structurally characterize GNP and RGO nanofillers. The properties of the new TPU nanocomposite materials were studied using thermal analysis techniques (Dynamical Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TG)) to describe the influence of graphene nanofillers on polyurethane matrix. Our investigation describes the comparison of two types of graphene derivatives, commercial one (GNP) and synthesized (RGO) on thermoplastic polyurethanes. These nanofillers provides opportunities to achieve compatibility with the TPU matrix. The property enhancements are attributed commonly to high aspect ratio of graphene nanoplatelets and filler–polymer interactions at the interface. The obtained nanocomposites exhibit higher thermal and mechanical properties due to the good dispersion of both nanofillers into TPU matrix. It was found that the addition of 2 wt % of the nanofiller could lead to a significant reinforcement Effect on the TPU matrix. Also, with high content of nanofiller (GNP and RGO), the Payne Effect was observed
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origin of nonlinear viscoelasticity in filled rubbers theory and practice
2014Co-Authors: Deepalekshmi Ponnamma, Sabu ThomasAbstract:The present chapter is written as an introduction towards this book on nonlinear viscoelasticity of rubber composites and nanocomposites. Rather than introducing the concept of the book to the readers this chapter reveals the basics behind rubber viscoelasticity and explains both linearity and nonlinearity from this behavior. Various filler reinforced rubbers are introduced emphasising the flow behavior of such nanocomposites. Major mathematical models proposed by Kraus, Huber and Vilgis and Maier and Goritz for the ‘Payne Effect’ are briefly addressed based on the filler matrix interactions existing in the composite systems.
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Influence of non-covalent functionalization of carbon nanotubes on the rheological behavior of natural rubber latex nanocomposites
European Polymer Journal, 2014Co-Authors: Deepalekshmi Ponnamma, Joung Sook Hong, Sang Hoon Sung, Kyung Hyun Ahn, K. T. Varughese, Sabu ThomasAbstract:This paper aims at correlating the dispersion of multi walled carbon nanotubes (MWCNT) in natural rubber latex (NRL) medium with the rheological properties of nanocomposites. For this, MWCNTs were first treated with surfactants of different charges – anionic sodium dodecyl sulphate (SDS), cationic cetyl trimethyl ammonium bromide (CTAB) and non-ionic Tween 20 (TW) – prior to their latex dispersion by solution mixing. Simple techniques like UV visible spectroscopy and sedimentation index analysis are used to explore the better dispersion of surfactant/MWCNTs in aqueous medium, where the surfactants reduce the agglomeration and entanglement of the nanotubes and facilitate strong filler–polymer interfacial adhesion. Rheology of the NRL-MWCNT suspensions is applied to derive the CNT–latex interfacial interactions in a quantitative way. For this Maier-Goritz theoretical modeling is applied on the observed ‘Payne Effect’. The Effect of concentration of fillers, mixing time and temperature on the viscoelasticity of composites were also investigated. Contact angle measurements, transmission electron microscopy and Raman spectroscopy have been employed to substantiate the enhanced compatibility of surfactants wrapped MWCNTs with NRL where a promising dispersion and interfacial adhesion were achieved.
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synergistic Effect of multi walled carbon nanotubes and reduced graphene oxides in natural rubber for sensing application
Soft Matter, 2013Co-Authors: Deepalekshmi Ponnamma, Kishor Kumar Sadasivuni, Michael Strankowski, Qipeng Guo, Sabu ThomasAbstract:Utilizing the electrical properties of polymer nanocomposites is an important strategy to develop high performance solvent sensors. Here we report the synergistic Effect of multi walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) in regulating the sensitivity of the naturally occurring elastomer, natural rubber (NR). Composites were fabricated by dispersing CNTs alone and together with exfoliated RGO sheets (thermally reduced at temperatures of 200 and 600 °C ) in NR by a solution blending method. RGO exfoliation and the uniform distribution of fillers in the composites were studied by atomic force microscopy, Fourier transformation infrared spectroscopy, X-ray diffraction, transmission electron microscopy and Raman spectroscopy. The solvent sensitivity of the composite samples was noted from the sudden variation in electrical conductivity which was due to the breakdown of the filler networks during swelling in different solvents. It was found that the synergy between CNTs and RGO exfoliated at 200 °C imparts maximum sensitivity to NR in recognizing the usually used aromatic laboratory solvents. Mechanical and dynamic mechanical studies reveal efficient filler reinforcement, depending strongly on the nature of filler–elastomer interactions and supports the sensing mechanism. Such interactions were quantitatively determined using the Maier and Goritz model from Payne Effect experiments. It is concluded that the polarity induced by RGO addition reduces the interactions between CNTs and ultimately results in the solvent sensitivity.
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interrelated shape memory and Payne Effect in polyurethane graphene oxide nanocomposites
RSC Advances, 2013Co-Authors: Deepalekshmi Ponnamma, Sabu Thomas, Kishor Kumar Sadasivuni, Michael Strankowski, Paula Moldenaers, Yves GrohensAbstract:We report the fabrication of graphene oxide (GO) based polyurethane (PU) nanocomposites by a simple method of mixing and their shape memory properties at different temperatures. Both the polymer and the filler were synthesized in the laboratory by simple and easy methods – PU by pre-polymer method and GO by improved graphene oxide synthesis method. High molecular level dispersion of GO platelets within the PU matrix and thus good mechanical properties were maintained by the improved PU/GO interfacial interaction. The structure of the polymer composites was investigated by scanning electron microscopy and X-ray diffraction studies revealed a highly dispersed morphology of graphene oxide sheets in PU. The improvement in shape memory obtained for the nanocomposites was then quantitatively analysed using the Payne Effect. The crosslink density calculated using the Maier and Goritz model (Payne Effect) was found to be dependent on the thermal transitions of the composites and it varied with the filler concentration. Accordingly a nice correlation was established between the temperature dependence of shape memory and the crosslink density. Composite behaviour was further analysed by the dynamic measurements such as rheology, stress relaxation and Mullins Effect. To the best of our knowledge, the quantification of shape memory in terms of physical crosslinks and filler–polymer entanglements of the PU/GO nanocomposite system has not been addressed before and is introduced in this work.