Effect of types of carbon black and cure conditions on dynamic mechanical properties of elastomers

The dynamic mechanical properties of natural rubber and bromobutyl rubber (used in automotive suspension parts) were investigated to determine the effect of particle size of carbon black filler and state of cure of the rubber matrix. The results indicate that state of cure has little effect on storage modulus (hardness and stiffness). However, elastomers with a desirable storage modulus, with low sensitivity to temperature change, can be developed using a filler with a small particle size.     

A Comparison Study on the Magneto-Responsive Properties and Swelling Behaviors of a Polyacrylamide-Based Hydrogel Incorporating with Magnetic Particles

This work investigates the mechanical properties, microstructures, and water-swelling behavior of a novel hydrogel filled with magnetic particles. The nanoparticles of magnetite (Fe₃O₄) and the micro-particles of carbonyl iron (CI) were selected and filled into a polyacrylamide (PAAM) hydrogel matrix to create two types of magnetic hydrogels. The isotropy and anisotropy of magnetic hydrogels are also presented in this study. The isotropic samples were cured without applying a magnetic field (MF), and the anisotropic samples were cured by applying an MF in the direction perpendicular to the thickness of the samples. The effects of the size, content, and inner structures of magnetic particles on the magneto-responsive and swelling properties of magnetic hydrogels were investigated. It was found that the magnetorheological (MR) effect of anisotropic samples was apparently higher than that of isotropic samples, and the hydrogels with CI exhibited a noticeable MR effect than those with Fe₃O₄. The storage modulus can be enhanced by increasing the filler content and size, forming an anisotropic structure, and applying an external MF. In addition, the magnetic hydrogels also have a swelling ability that can be tuned by varying the content and size of the particle fillers.     

Influence of polyurethane properties on mechanical performances of magnetorheological elastomers

Magnetorheological elastomers (MREs) are mainly composed of magnetizable particles and elastic polymer. The polymer matrix plays an important role in mechanical performances of MREs. In this study, the polyurethane (PU), which is synthesized by using toluene diisocyanate (TDI) and poly (propylene glycol) (PPG‐220), is selected as a matrix because it has better degradation stability than natural rubber and higher mechanical stability than silicone rubber. Four different MRE samples were fabricated by adjusting the reaction molar ratio of TDI to PPG to change the property of PU matrix. Structural characterization of the PU matrix was described by Fourier transform infrared analysis. The microstructures of samples were observed by using an environmental scanning electron microscope. The mechanical performances of samples, including shear modulus, magnetorheological effect (MR) effect, loss factor, and glass transition temperature (T_g), were characterized with dynamic mechanical analyzer. The results show that the shear modulus, the relative magnetic residual shear modulus and glass transition temperatures of samples increase with the increment of toluene diisocyanate, while the relative MR effects and loss factors decrease steadily. The experimental results indicate that optimal molar ratio (TDI : PPG) is 3 : 1. The field‐induced shear modulus of sample with molar ratio 3 : 1 is 4.9 MPa, and the relative MR effect is 121% under an external magnetic field of 800 mT at room temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and thermal behavior of styrene butadiene rubber composites reinforced with silane-treated peanut shell powder

Biocomposites of styrene butadiene rubber (SBR) reinforced with silane-treated peanut shell powder (SPSP) of different filler loadings and particle sizes were prepared by two roll mixing mills with sulfur as a vulcanizing agent. The cure characteristics of composites were studied, and they vulcanized at 160 °C. Test samples were prepared by compression moulding, and their physicomechanical properties, such as tensile strength tear strength, modulus, hardness, and abrasion resistance of SBR vulcanizates, were studied with filler loading 0, 5, 10, 15, and 20 parts per hundred rubber (phr). Composites with 10 phr filler having small particle size exhibited better properties. The interfacial adhesion between filler and matrix has a major role in the properties of composites. Surface modification of PSP was done by silane coupling agent to improve the interfacial adhesion and it characterised by FTIR, XRD, TGA, UV, and SEM. Better properties are shown by the composites with SPSP. Thermal stability of the composites was also determined using thermogravimetric analysis.     

磁敏橡胶材料弹性模量的测试与研究

研究了磁敏橡胶超声测试的基本方法和参数,测量了各向同性和颗粒成链磁敏橡胶材料的纵向模量。对含铁颗粒填料体积分数不同的磁敏橡胶样本进行了三点弯曲试验,计算出磁敏橡胶样本的弹性模量,并与相关理论预测模型进行了对比,结果表明,对于各向同性磁敏橡胶,随着含铁颗粒填料体积分数的增加,其弹性模量和剪切模量增大。颗粒成链磁敏橡胶的弹性模量很大程度上依赖于测量的方向,含铁颗粒填料体积分数超过15 ％时,在平行和垂直于颗粒链方向所测得的弹性模量有显著的不同。这是因为含铁颗粒填料体积分数超过15 ％时,磁敏橡胶的颗粒成链结构不具有立体对称性。     

Nonlinear rheological study of magneto responsive soft gels

Swollen physical magnetorheological (MR) gels were obtained by self-assembly of triblock copolymers containing dispersed magnetic particles. We carry out a detailed investigation of the nonlinear rheological properties of MR gels under large amplitude oscillatory shear flow. A strong Payne effect is observed for strains above 0.05% which is the limit of linear viscoelastic region. The onset strain for the transition from linear to nonlinear viscoelastic behaviour is much smaller than in the absence of a magnetic field. We show that the magnetic Payne effect strongly depends on the magnetic flux density, the particle volume fraction, the sample's initial particle distribution and viscoelastic properties of the matrix.The rheological response of MR gels is strongly related to the ability for rearrangement of the particles in the presence of the magnetic field. Upon sudden application of a magnetic field, the particle network embedded in a soft matrix becomes more anisotropic than is the case in a hard matrix since the resistance of the matrix to particle rearrangement is smaller. The induced anisotropic particle network parallel to the field provides larger absolute rheological response.     

Rubber-filler interaction effects on the solid state dynamic mechanical properties of polyethylene/EPDM/calcium carbonate composites

Composites of polyethylene, ethylene propylene diene rubber (EPDM), and calcium carbonate are milled and analyzed by solid state dynamic mechanical spectroscopy. The torsion pendulum measurements show that the multicomponent composites exhibit complex viscoelastic behavior. In composites of polyethylene and calcium carbonate, the experimentally observed modulus enhancement is greater than that expected from the properties of the constituent materials, assuming well-dispersed inclusions. In composites of polyethylene, rubber, and calcium carbonate, interactions of the rubber with the filler surface are significant. Specifically, maleic anhydride modification of the EPDM results in rubber-filler interactions that drastically influence the properties of the composite. The maleic anhydride modification results in a morphology with more rubber around the filler particles and thus an enhanced rubber glass transition peak. The rubber-filler interaction has been attributed to salt formation at the filler surface. The interaction was also detected by solid state proton nuclear magnetic resonance (NMR) relaxation experiments. Treatment of the filler surface with gamma-aminopropyltriethoxysilane (γ-APS) or gamma-methacryloxypropyltrimethoxysilane (γ-MPS) has significant influence on the dynamic mechanical properties.     

Effect of nano clay on the constrained polymer volume of chlorobutyl rubber nanocomposites

The dynamic mechanical properties of chlorobutyl rubber nanocomposites containing different varieties of clay have been investigated. The clay moieties have been chosen so that they vary in their organic modification, modifier concentration, and d spacing. The viscoelastic properties such as storage modulus, damping behavior, and loss modulus of polymer composites depends on matrix filler interaction, crystallinity, and extent of crosslinking. The prepared composites were characterized by X Ray Diffraction, and the extend of exfoliation/intercalation was studied. It has been observed that the storage modulus of the composites increased with the addition of filler due to the enhancement in stiffness of the material. The damping behavior was found to decrease with the addition of filler and this was attributed to the restricted movement of the polymer segments. The higher surface area to volume ratio of the layered silicate resulted in the better interaction between the polymer matrix and filler. The variation of loss as well as storage modulus of the nanocomposites were evaluated as a function of filler loading, and a comparison of the properties of the rubber nanocomposites containing different organic clay was also carried out. Finally, a calculation of constrained volume of polymer chains was done in the nanocomposites. POLYM. COMPOS., 36:2135–2139, 2015. © 2014 Society of Plastics Engineer     

Preparation and properties of magnetorheological elastomers based on silicon rubber/polystyrene blend matrix

Magnetorheological (MR) elastomers, which are mainly composed of magnetic particles and elastic polymer, are a new kind of smart materials whose modulus can be controlled by changing the strength of magnetic fields. In this article, MR elastomers based on immiscible silicon rubber/polystyrene (SR/PS) blend matrix were fabricated successfully via cosolvent method and the MR effect, electric and mechanical properties, and the microstructures of the corresponding materials were studied. SEM studies showed that the dispersion of iron particles in blend matrix were different from that in single polymer, which could be further proved by the different electric conductivity. The MR effect of MR elastomers based on blend matrix varied with the different ratios of SR and PS, which was discussed in detail from the special dispersion of iron particles and of zero‐modulus of MR elastomers. In addition, the MR elastomers based on SR/PS blend matrix had enhanced mechanical properties, which made them more hopeful to be applied in practice. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3143–3149, 2007     

Effect of particle morphology on viscoelastic and flexural properties of epoxy–alumina polymer nanocomposites

Nanocomposites were synthesised by dispersing two different types of alumina nanoparticles in epoxy matrix by ultrasonication. Alumina nanoparticles of two shapes, rod and spherical were selected to investigate the effect of particle morphology on viscoelastic and flexural properties of nanocomposites. Specific surface area of both the selected nanoparticles was kept in the similar range. Good dispersion of nanoparticles was observed through transmission electron microscopy. The addition of nanoparticles in epoxy had significant enhancement in the viscoelastic properties and moderate improvement in flexural properties of composites. Composites having alumina nanorods showed higher improvement both in storage modulus as well as in flexural properties in comparison to composites having spherical alumina nanoparticles. Efficacy of Mori-Tanaka method was explored in modelling storage modulus of nanocomposites. Assorted size of alumina nanorods based on particle size distribution was used to model composites with nanorods to see the effect of size assortment on storage modulus.     

Viscoelastic and thermal properties of natural rubber low-density polyethylene composites with boric acid and borax

The influence of boric acid (BA) and borax (BO) neutron-absorbing fillers on thermal stability and viscoelastic behavior of natural rubber (NR) low-density polyethylene composites has been studied. The thermal degradation and dynamic mechanical properties of the composites have been analyzed as a function of temperature. The results revealed the enhancement of thermal stability of the composites by the addition of BA and BO fillers. The flame resistance of the material was improved by the addition of both the fillers. The storage modulus was found to be dependent upon the temperature and nature of the filler. The amount of NR chains immobilized by filler particles has been quantified from dynamic mechanical analysis and secondary filler/filler interactions have been verified by the Payne effect analysis. Finally, the experimental results have been compared with theoretical predictions.     

Filler and mobility of rubber matrix molecules

Filler surfaces in elastomers influence mobility of rubber matrix molecules. Mobility of rubber matrix molecules then determines elastomer properties and behaviour of rubber products in applications. Effect of filler in elastomer–filler system is usually characterized by different properties: Modulus seem to depend mainly on filler cluster size and filler network behaviour but effect of mobility of rubber matrix molecules is also evident. Bound rubber characterize fraction of rubber immobilized on filler particle surfaces, however, can be obtained only for uncured rubber–filler compounds. As it is shown in this paper, the permeability coefficient of permanent gas in rubber–filler system could characterize mobility of rubber matrix molecules around the filler particles and the activation energy of its permeation could characterize strength of physical bonds between the rubber matrix molecules and surface of filler particles.     

On the Role of Both Polypropylene Fibers and Silica Nanoparticles on the Viscoelastic Behavior of Silicone Rubber Nanocomposites

In the present study, silica nanoparticles and polypropylene fibers were added to silicone rubber matrix and their effect was investigated on the viscoelastic behavior of silicone rubber composites by dynamic mechanical analysis and compression set test. Bonding of the reinforcements with silicone rubber matrix was studied by Fourier transform infrared spectroscopy (FTIR). The results proved that the role of silica particles on the elastic modulus of silicone rubber was more effective than that of polypropylene at room temperature because of higher stiffness and also partial interaction of polypropylene with matrix.     

Dynamic mechanical properties of magnetorheological elastomers based on polyurethane matrix

Magnetorheological elastomers (MRE) are mainly composed of soft magnetic particles and rubber‐like matrix. Previous studies have shown that the matrix has a greater impact on mechanical properties of MRE. In this article, a new kind of polyurethane material was fabricated and used as the matrix of MRE. The effect of several factors on the mechanical properties of MRE samples was experimentally studied, such as fabrication condition, content of iron particles, different weight ratio of castor oil and diphenylmethane diisocyanate, plasticizer. Their microstructures were observed, and the mechanical properties were measured using a testing system in the presence of an external magnetic field. The experimental results demonstrate that these factors have different impact on shear storage modulus, magneto‐induced modulus, MR effect and damping property. In addition, the damping property of these MRE is also higher than that of MRE based on the other matrix. This study can hopefully be applied to optimize the mechanical properties of MRE. POLYM. COMPOS., 37:1587–1595, 2016. © 2014 Society of Plastics Engineers     

Dynamic mechanical behaviour of polyamide 11/Barium titanate ferroelectric composites

Dynamic mechanical analysis and tensile test have been used to characterize the mechanical behaviour of hybrid composites. Barium titanate (BaTiO₃) is the submicron filler and polyamide 11 (PA 11) the matrix. The influence of volume fraction and particles size (ranging from 100 nm to 700 nm) of the inorganic phase on the composites mechanical properties have been checked. BaTiO₃ dispersion in the matrix increases the tensile modulus of the composites and an evolution from ductile to fragile is observed for volume fractions above 12 vol%. The volume fraction dependence of the glassy shear modulus is well described by the Hashin and Shtrikman model indicative of an interaction lack between the organic and inorganic phases. The decrease of the glassy shear modulus with the filler size has been associated with the existence of softer organic/inorganic interfaces, in agreement with the previous hypothesis. The non linear variation of the rubbery modulus versus particles content is well described by the rubber elasticity model applied to a hydrogen bond network.     

Viscoelastic properties of natural rubber composites reinforced by defatted soy flour and carbon black co‐filler

Filler mixtures of defatted soy flour (DSF) and carbon black (CB) were used to reinforce natural rubber (NR) composites and their viscoelastic properties were investigated. DSF is an abundant and renewable commodity and has a lower material cost than CB. Aqueous dispersions of DSF and CB were first mixed and then blended with NR latex to form rubber composites using freeze‐drying and compression molding methods. A 40% co‐filler reinforced composite with a 1 : 1 DSF : CB ratio exhibited a 90‐fold increase in the rubber plateau modulus compared with unfilled NR, showing a significant reinforcement effect by the co‐filler. The effect, however, is lower than that observed in the carboxylated styrene–butadiene rubber composites reported earlier, indicating a significant effect from the rubber matrix. The co‐filler composites have elastic moduli between those of DSF and CB reinforced composites. Stress softening and recovery experiments indicated that the co‐filler composites with a higher CB content tend to have a better recovery behavior; however, this can not be simply explained from the recovery behaviors of the single filler (DFS and CB) composites. CB composites prepared by freeze‐drying show a strain‐induced reorganization of fillers. Strain sweep experiment data fit with the Kraus model indicates the co‐filler composites with a higher CB content are more elastic, which is consistent with the recovery experiments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Dynamic mechanical properties of poly(vinyl chloride)–xonotlite composite system

The filler effect of xonotlite (6CaO.6SiO₂.H₂O; needle-shaped) on dynamic mechanical properties, such as storage modulus (E′), loss modulus (E″), and tan δ was studied for the PVC—xonotlite composite system. And the properties of the system containing mechanically or chemically disaggregated particle of xonotlite were compared with those of the system-filled aggregates. The dynamic mechanical properties obviously depends on the dispersion condition of xonotlite particle. The aggregates of xonotlite produces a remarkably high modulus, an increase in T_g, and a decrease in mechanical damping near T_g in the system. On the other hand, the disaggregates, especially the chemical disaggregate one, bring softer or more rubbery properties in these systems. The interaction between matrix and filler was the strongest in the aggregates system and decreases in the order, mechanical disaggregates system, chemical disaggregates system.     

Flow properties of natural rubber composites filled with defatted soy flour

The linear and nonlinear viscoelastic properties of natural rubber composites reinforced with defatted soy flour (DSF) were studied. DSF is an abundant, renewable commodity, and its rigid nature makes it suitable as a reinforcement phase in rubber composites. At small strain, the elastic modulus of a 30% filled composite was about 20 times higher than the unfilled rubber. Greater reinforcement was observed for carbon black filled composites than for DSF filled composites at filler concentrations of 10 and 20%. At high strain, values of the relaxation modulus dropped more rapidly for highly filled DSF composites. At high shear rates in a capillary viscometer, a small reinforcement effect remained for all composites, and lower die swell was observed for DSF composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of Rice Husk Filler on the Mechanical and Thermal Properties of Liquid Natural Rubber Compatibilized High-Density Polyethylene/Natural Rubber Blends

Natural rubber/high-density polyethylene (NR/HDPE) blend with rice husk (RH) filler and liquid natural rubber (LNR) as the compatibilizer was prepared using an internal mixer at 140°C and 50 rpm. The reinforcing effect and compatibilizing performance of the added reagents in the composites were evaluated from the mechanical and thermal properties, and blend homogeneity. The tensile and impact strength decreased with RH loadings in the matrix, while the tensile modulus and hardness showed an opposite trend. The weak filler–matrix interaction, resulting in poor filler dispersion and large agglomerated particle size, caused those properties to decrease. However, the mechanical properties of the composites improved with the addition of NR or LNR into the matrix. The dissolution effect caused interactions between the phases, leading to an improvement in the compatibility in the blend. Changes in morphology resulted in the shift of T _g of the amorphous part of NR to higher temperatures, as observed in differential mechanical analysis (DMA) thermograms. Scanning electron microscopy (SEM) micrographs of the fractured surface had also revealed the good RH–matrix interaction and, thus, the dispersion of particles in samples with added LNR.