Dynamic stress relaxation behavior of nanogel filled elastomers (original) (raw)
Related papers
Influence of Nanogels on Mechanical, Dynamic Mechanical, and Thermal Properties of Elastomers
Nanoscale Research Letters, 2009
Use of sulfur crosslinked nanogels to improve various properties of virgin elastomers was investigated for the first time. Natural rubber (NR) and styrene butadiene rubber (SBR) nanogels were prepared by prevulcanization of the respective rubber lattices. These nanogels were characterized by dynamic light scattering, atomic force microscopy (AFM), solvent swelling, mechanical, and dynamic mechanical property measurements. Intermixing of gel and matrix at various ratios was carried out. Addition of NR gels greatly improved the green strength of SBR, whereas presence of SBR nanogels induced greater thermal stability in NR. For example, addition of 16 phr of NR gel increased the maximum tensile stress value of neat SBR by more than 48%. Noticeable increase in glass transition temperature of the gel filled systems was also observed. Morphology of these gel filled elastomers was studied by a combination of energy dispersive X-ray mapping, transmission electron microscopy, and AFM techniques. Particulate filler composite reinforcement models were used to understand the reinforcement mechanism of these nanogels.
Journal of Applied Polymer Science, 2008
The influence of sulfur-crosslinked, quasi-nanosized gels on the rheological and mechanical properties of raw natural rubber (NR) was investigated. Latex gels with different crosslink densities were prepared through the variation of the sulfur-to-accelerator ratio. These gels were characterized by dynamic light scattering, solvent swelling, and mechanical properties. The gels were mixed with raw NR latex at concentrations of 2, 4, 8, and 16 phr, and their effect on the rheological properties of NR was studied by Monsanto processability tester. The presence of gel in raw NR reduced the apparent shear viscosity and die swell considerably. Initially, the viscosity decreased up to a 8 phr gel loading and then increased with an increase in the gel loading. However, the change in the viscosity was related to the crosslink density of the gels. A new empirical equation relating the viscosity, volume fraction of the gels, and crosslink density was proposed. The die swell of gel-filled raw NR was at least 10% lower than that of unfilled raw NR and decreased with an increase in the gel loading. The effect of the gels on the die swell properties was explained through the calculation of the principal normal stress difference of gel-filled NR systems. Scanning electron photomicrographs of the extrudates revealed much better surface smoothness for the gel-filled virgin rubber systems than for the unfilled rubber. The addition of the gels to raw NR increased the modulus and tensile strength, whereas the elongation at break decreased. The effect of the gels on the dynamic mechanical properties of NR was also investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Radiation Physics and …, 2010
Electron beam (EB) crosslinked natural rubber (NR) gels were prepared by curing NR latex with EB irradiation over a range of doses from 2.5 to 20 kGy using butyl acrylate as sensitizer. The NR gels were systematically characterized by solvent swelling, dynamic light scattering, mechanical and dynamic mechanical properties. These gels were introduced in virgin NR and styrene butadiene rubber (SBR) matrices at 2, 4, 8 and 16 phr concentration. Addition of the gels improved the mechanical and dynamic mechanical properties of NR and SBR considerably. For example, 16 phr of 20 kGy EB-irradiated gel-filled NR showed a tensile strength of 3.53 MPa compared to 1.85 MPa of virgin NR. Introduction of gels in NR shifted the glass transition temperature to a higher temperature. A similar effect was observed in the case of NR gel-filled SBR systems. Morphology of the gel-filled systems was studied with atomic force microscopy. The NR gels also improved the processability of the virgin rubbers greatly. Both the shear viscosity and the die swell values of EB-irradiated gel-filled NR and SBR were lower than their virgin counterparts as investigated by capillary rheometer.
Emerging Advances in Rubber Technology by the Suitable Application of Sol-Gel Science and Technology
Rubber Chemistry and Technology, 2021
In recent years, the application of sol-gel science to industrial polymer research has offered advancements in rubber technology. The use of sol-gel–synthesized materials for the development of highly reinforced rubber composites is the most commonly adopted and popular method exercised by rubber scientists. This article comprehensively reviews the recent progress regarding preparation and properties of sol-gel–synthesized nanoparticles-based rubber composites. The pragmatic consequences of sol-gel–synthesized nanoparticles in rubber compounds are systematically described through rheological, mechanical, and thermal properties. Emphatic focus is given to understanding the reinforcement mechanism of rubber composites by the use of sol-gel–derived alkoxide silica as filler. The properties of rubber nanocomposites are usually dependent on the dispersion of sol-gel–synthesized nanoparticles into the rubber matrix. The results reviewed from prolific studies suggested that sol-gel science...
Development in Organic-Inorganic Hybrid Elastomers Prepared by the Sol-Gel and Related Processes
1995
hybrid materials are described from a viewpoint of using elas- tomeric matrix to accommodate inorganic rigid component and the sol-gel reactions to obtain hybrid mate- rials. In the development of inorganic fillers for the reinforcement of rubbers, silane coupling agents be- came used for a better adherence of the interface between organic matrix and inorganic filler surface. Moisture curing by 3-aminopropyl triethoxysilane of halogen-containing rubbers in the presence of silica particles enabled us to conduct curing and reinforcement simultaneously. In situ formation of silica particles in elastomeric matrix was achieved by conducting the sol-gel process of tetraethoxysilane (TEOS) in the rubbery matrix. Increase of modulus and tensile strength at break was recognized, which suggests inclusion of silica particles in vulcanizates. The sol-gel process on TEOS and triethoxysilyl-ter- minated polyethers resulted in the formation of organic-inorganic hybrid gels, the structure and dynam...
Tensile Stress Relaxation Studies of TiO 2 and Nanosilica Filled Natural Rubber Composites
Industrial & Engineering Chemistry Research, 2009
Composites of natural rubber were prepared with TiO 2 and nanosilica. The stress relaxation behavior of the composites under tension was studied with reference to the filler loading and strain level. It was observed that the rate of stress relaxation increases with increase in filler loading. The rate of stress relaxation was found to be higher for silica-filled NR compared to TiO 2 -filled NR. This is due to the high degree of agglomeration in silica compared to titanium dioxide filler. The effect of ageing on the stress decay was also investigated and the rate of stress relaxation was found to decrease after ageing. The experimental curves were fitted with the stretched Kohlrausch equation. From the fitting parameters, the relaxation time and the stretching exponent were estimated in order to understand the mechanism of the relaxation processes in the filled natural rubber composites.
Reinforcing Mechanisms of Starch Nanocrystals in a Nonvulcanized Natural Rubber Matrix
Biomacromolecules, 2011
Unfilled elastomers are known to exhibit linear viscoelastic behavior at shear strains up to 10À20%. 1 To enhance the mechanical properties of elastomers, most of them are reinforced with fillers, notably carbon black, silica, or clays such as montmorillonite. 2,3 It has been shown that unlike unfilled elastomers, reinforced materials exhibit a nonlinear viscoelastic behavior at shear strains as low as a few percent, generally described in terms of Mullins or Payne effects. The Mullins effect or "stress softening effect" is characterized by a pronounced lowering of the storage modulus (or stress) when elastomers are sheared a second time. 4 The Payne effect characterizes the decrease in the real part of the elastic modulus with increasing strain amplitude. This nonlinear behavior has been first evidenced for natural rubber filled with carbon black 2 and has been confirmed by many authors for reinforced synthetic elastomers. 1,5À9 This behavior is of great practical importance and essential for tire applications. It has been related to usage properties, and, in particular, to the rolling resistance or the wet skid resistance of tires. Various mechanisms have been proposed in the literature to explain the origins of the reinforcement of elastomers. They include molecular surface slippage or rearrangements, particle displacements, interparticle chain breakage, strong and weak surface binding, and other network particle surface phenomena. 8 During the last decade, the increase in fossil energy costs and environmental issues has resulted in the development of biodegradable materials from renewable resources. In parallel, polymer nancomposites have attracted considerable interest in both academia and industry, owing to their outstanding mechanical properties like elastic stiffness and strength while using only a small amount of nanoparticles. The enhanced properties include not only mechanical performances but also barrier resistance, flame retardancy, as well as optical and electrical properties. In this context, waxy maize starch nanocrystals have been used as filler in a nonvulcanized natural rubber (NR). 11,12 The NR matrix was not cross-linked to keep the biodegradability and recyclability of such biosourced materials. Waxy maize starch nanocrystals appeared to display interesting barrier properties and to be an effective reinforcing filler for NR at temperatures higher than T g of the matrix. Dynamic mechanical analysis performed in the linear viscoelastic region has shown that the relaxed modulus at room temperature of nanocomposites containing 10, 20, and 30 wt % (around 6.7, 13.4, and 20.1 vol %) of filler was about 10, 75, and 200 times higher, respectively, than the one of the unfilled ABSTRACT: A phenomenological modeling approach was developed to try to understand the reinforcing mechanism of starch nanocrystals in a nonvulcanized natural rubber matrix. Natural rubber was not cross-linked to maintain the biodegradability of the biosourced materials. Nonlinear dynamic mechanical experiments highlighted the significant reinforcing effect of starch nanocrystals and the presence of the Mullins and Payne effects. Two models were used to predict the Payne effect considering that either fillerÀfiller (Kraus model) or ma-trixÀfiller (Maier and G€ oritz model) interactions are preponderant. The use of the Maier and Goritz model demonstrated that phenomena of adsorption and desorption of NR chains on the filler surface governed nonlinear viscoelastic properties, even if the formation of a percolating network for filler contents >6.7 vol % was evidenced by the Kraus model.
Stress relaxation and hysteresis of nanocomposite gel investigated by SAXS and SANS measurement
Polymer, 2012
The stress relaxation phenomena of nanocomposite gel (NC gels) after uniaxial elongation was investigated by time-resolved small-angle scattering techniques of neutrons and X-rays. Nanocomposite gels consist of clay platelets and poly(N-isopropylacrylamide). It was found that clay oriented instantly and polymer chains were elongated along the stretching direction by elongation, followed by gradual process of peeling-off of adsorbed polymer chains on the clay platelets. When the specimen was held in the deformed state, stress relaxation was observed. This was mainly ascribed to peeling-off of polymer chains. When the strain of the specimen was removed, the polymer chains tended to be adsorbed again to the surface of the clay platelets. The deformation mechanism of NC gels is discussed on the emphasis of the peeling-off and peeling-on process of polymer chains.
Mechanical Properties of Rubber Nanocomposites: How, Why... and Then
HAL (Le Centre pour la Communication Scientifique Directe), 2010
Through the review of literature, this chapter will first recall the typical mechanical behaviour of rubber filled with nanofillers, from the viscoelastic linear behaviour to the large deformation one, including the ultimate properties. Then we will highlight the main filler parameters and how they seem to control these properties. In particular, we will focus on the role of filler-filler and filler matrix interactions, which are necessarily important when dealing with fillers with such high specific surface (up to several hundreds of meter square per gram). We will also see the influence of these fillers on the matrix properties, since, for instance, the filler presence can modify the matrix crosslinking kinetic or induce crystallization. Then, this description will be completed by the introduction of different modelling approaches developed to account for and eventually predict the role of nanofillers in the mechanical behaviour of these rubber nanocomposites.
Rubber network in elastomer nanocomposites
European Polymer Journal, 2007
The influence of inorganic nanoparticles on crosslinking mechanism of elastomers has been evaluated by applying the tube model on equilibrium statistical mechanics. The results have shown that a highly ordered structure with a huge amount of entanglements, wherein the polymer is nanoscopically confined, is formed by the addition of nanoparticles. These physical links exhibit freedom of movement under stretching, but in a lower volume because of confinement. That is, network molecular parameters such as lateral tube dimensions or average molecular mass of the chains decreased in presence of nanoparticles.