Showing papers on "Natural rubber published in 2004"

Experimental Research and Modeling of Magnetorheological Elastomers

Abstract: In this paper, new methods for fabricating magnetorheological (MR) elastomers are introduced. Two different MR elastomers, one made of polyurethane and the other made of natural rubber, are successfully fabricated. The experimental results show that the modulus of polyurethane MR elastomers can increase by 28% under a strong magnetic field. Comparatively, the rubber MR elastomer has low modulus change ability. A mathematical model to represent the stress-strain relationship of MR elastomers is presented. The model takes into account all the dipole interactions in a chain and the nonlinear properties of the host composite. The analytical results of the model are in agreement with experimental data.

Factors that affect the fatigue life of rubber: A literature survey

Abstract: Many factors are known to influence the mechanical fatigue life of rubber components. Four major categories of factors are reviewed here: the effects of mechanical loading history, environmental effects, effects of rubber formulation, and effects due to dissipative aspects of the constitutive response of rubber. For each category, primary factors are described, and existing literature is presented and reviewed. Rubber's fatigue behavior is extremely sensitive to both the maximum and minimum cyclic load limits. Other aspects of the mechanical load history are also discussed, including the effects of static loaded periods (“annealing”), load sequence, multiaxiality, frequency, and loading waveform. Environmental factors can affect both the short and long term fatigue behavior of rubber. The effects of temperature, oxygen, ozone, and static electrical charges are reviewed. A great range of behavior is available by proper manipulation of formulation and processing variables. Effects of elastomer type...

Orientation and Crystallization of Natural Rubber Network As Revealed by WAXD Using Synchrotron Radiation

Abstract: Strain-induced crystallization of natural rubber samples with various network-chain densities, ν, was investigated by synchrotron X-ray diffraction measurements. It was found that the onset strain of crystallization was almost independent of ν. Lateral crystallite size and degree of orientational fluctuations of crystallites were also evaluated. These results indicated that stretched molecular chains acted as nuclei while surrounding chains could also contribute to the crystal growth. Deformation of crystal lattice with nominal stress was detected, and the strain-induced crystallites were found to be responsible for the increased modulus upon elongation. The unit cell volume decreased almost linearly with nominal stress. By assuming the deformation mechanism of the rubber network as a pantograph, the reinforcement effect of the crystallites is thought to be brought out not directly by crystallites connected in series but indirectly through the surrounding network chains.

The Reinforcement of Elastomeric Networks by Fillers

Abstract: Summary: The mechanisms involved in rubber reinforcement are discussed. A better molecular understanding of these mechanisms can be obtained by combining characterization of the mechanical behavior with an analysis of the chain segmental orientation accompanying deformation. While the strain dependence of the stress is the most common quantity used to assess the effect of filler addition, experimental determination of segmental orientation can be used to quantify the interfacial interactions between the elastomeric matrix and the mineral inclusions. SEM micrograph of natural rubber containing 10 wt.-% of organomodified clay.

Thermoset rubber/layered silicate nanocomposites. Status and future trends

Abstract: This paper surveys the recent achievements with thermoset rubber/layered silicate nanocomposites considering their production methods, cure characteristics, structure and basic properties (mechanical, thermal and barrier). It was shown that the properties of the “nanoreinforced” rubbers strongly depend on the dispersion state of the silicate. The latter can be influenced by various methods related to the production route (latex, solution or melt compounding), silicate type (natural and artificial origin mostly affecting the aspect ratio), surface modification of the silicate (chemical buildup of the surfactant used for “organophilization”), recipe (curatives, activators, compatibilizers, etc.) and compounding parameters (temperature, time, shear rate, etc.). A peculiar skeleton-type reinforcing structure can be produced by latex compounding. Solution and melt intercalation techniques usually result in nanocomposites containing silicate layers in both intercalated and exfoliated forms. To detect the related structure the combined use of transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques is inevitable. Confinement and deintercalation of the organophilic layered silicates occurring during compounding can be circumvented by the proper selection of the surfactants. Based on the present praxis some tendencies for future R&D activities with rubber nanocomposites were deduced and a strong impetus was forecasted to them owing to the fast development with thermoplastic/layered silicate systems. Polym. Eng. Sci. 44:1083–1093, 2004. © 2004 Society of Plastics Engineers.

Preparation and properties of nanocomposites based on acrylonitrile-butadiene rubber, styrene-butadiene rubber, and polybutadiene rubber

Abstract: Nanocomposites were prepared with different grades of nitrile rubber with acrylonitrile contents of 19, 34, and 50%, with styrene–butadiene rubber (23% styrene content), and with polybutadiene rubber with Na-montmorillonite clay. The clay was modified with stearyl amine and was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies showed an increase in the gallery gap upon the modification of the filler by stearyl amine. The intercalation of the amine chains into the clay gallery gap was confirmed by the presence of some extra peaks (2928, 2846, and 1553 cm−1) in the FTIR spectra. The clay–rubber nanocomposites were characterized by TEM and XRD. The mechanical properties were studied for all the compositions. An improvement in the mechanical properties with the degree of filler loading up to a certain level was observed. The changes in the mechanical properties, with changes in the nature and polarity of the rubbers, were explained with the help of XRD and TEM results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1573–1585, 2004

Industrialization and application development of cyclo-olefin polymer

Abstract: Since its establishment in 1950, ZEON Corporation has contributed to the advancement of Japanese industry, as a chemical company focused on the manufacture of synthetic rubber. Some of our specialty rubber products hold 40–70% of the worldwide market share. ZEON’s exclusive technology is the source of a number of breakthroughs and continues to contribute to today’s polymer industry. In order to maintain the position as a leading company in synthetic rubber business, ZEON strategically planned industrialization of polyisoprene rubber to compete with natural rubber. The main raw material for polyisoprene rubber is isoprene monomer, which was not yet available on the market. ZEON had to first develop isoprene extraction technology from C5 fraction of naphtha successfully. The issue then was C5 fraction contained only 10–15% of isoprene monomer. In order to reduce the total isoprene monomer cost, we had to utilize other components. The components are 1,3-pentadiene (1,3-PDE), dicyclopentadiene (DCPD), and others. So along with polyisoprene business, we launched the 1,3-PDE resins business and DCPD resins business for adhesives and traffic paints in 1970. To fully utilize these extracted components, we still had to develop unique products using residual 1,3-PDE and DCPD. Our cyclo-olefin polymer business was born from this basic strategy to fully utilize those components. This report discusses the development and current status of cyclo-olefin polymer and its precision molding business, including optical film business, realized by the ZEON’s comprehensive utilization of C5 fraction.

Investigation into Waste Tire Rubber-Filled Concrete

Abstract: Over the years, there has been mounting interest in the use of recycled tire rubbers in highway construction. Tire rubber-filled concrete, a rubberized Portland cement concrete with a portion of aggregates replaced by tire rubber particles, represents an alternative of using recycled tire rubbers. It is found that rubberized concrete has very high toughness. However, its strength decreases significantly as the rubber content increases. This limits its application to secondary structural components only. Very little progress has been made in increasing the strength of rubberized concrete due to the lack of understanding of the toughing mechanism. In this study, rubberized concrete was treated as a multiphase particulate-filled composite material. A modified three-layer built-in composite model was proposed based on a previous study on ordinary concrete. Finite element analysis was conducted on the developed composite model. Cylindrical rubberized concrete samples and ordinary concrete samples were prepared and tested to provide basic physical/mechanical properties in the analysis. The effect of various design parameters on the composite strength was evaluated. The finite element analysis validated the test results.

Rubber compounding : chemistry and applications

Abstract: NATURAL RUBBER AND RECYCLED MATERIALS GENERAL-PURPOSE ELASTOMERS SPECIAL-PURPOSE ELASTOMERS BUTYL RUBBER THERMOPLASTIC ELASTOMERS CARBON BLACK SILICA AND SILANES GENERAL COMPOUNDING RESINS ANTIOXIDANTS AND OTHER PROTECTANT SYSTEMS VULCANIZATION COMPOUND DEVELOPMENT AND APPLICATIONS

Rubber Toughened Epoxy

Abstract: Toughening of epoxy resins for improvement of crack resistance has been the subject of intense research interest during the last two decades. Epoxy resins are successfully toughened by blending with a suitable liquid rubber, which initially remains miscible with epoxy and undergoes a phase separation in the course of curing that leads to the formation of a two-phase microstructure, or by directly blending preformed rubbery particle. Unlike the situation for thermoplastics, physical blending is not successful for toughening epoxy resins. Recent advances in the development of various functionalized liquid rubber-based toughening agents and core-shell particles are discussed critically in this review.

Flameproof thermoplastic resin composition

Abstract: The flameproof resin composition according to the present invention comprises (A) 20 to 90 parts by weight of a rubber modified polystyrene resin; (B) 10 to 80 parts by weight of a polyphenylene ether resin; (C) 0.1 to 30 parts by weight of a ring-shaped phosphonic acid compound, per 100 parts by weight of the sum of (A) and (B); and (D) 0 to 25 parts by weight of an aromatic phosphoric acid ester compound, per 100 parts by weight of the sum of (A) and (B).

Melt‐compounded natural rubber nanocomposites with pristine and organophilic layered silicates of natural and synthetic origin

Abstract: Composites based on natural rubber (NR) and containing organophilic and pristine layered silicates of natural and synthetic origin were produced by melt com- pounding and sulfur curing. The curing, thermomechanical, and mechanical properties of the mixes, which contained 10 phr (parts per hundred parts of rubber) silicates, were de- termined. The dispersion of the silicates was studied by X-ray diffraction (XRD) and transmission electron micros- copy (TEM). Organophilic clays accelerated the sulfur cur- ing of NR, which was believed to occur because of a com- plexation reaction in which the amine groups of the clay intercalants participated. The property improvements caused by the fillers were ranked as follows: organophilic clays pristine synthetic layered silicate (sodium fluorohec- torite) pristine natural clay (purified sodium bentonite) precipitated nonlayered silica (used as a reference). This was attributed to partial intercalation of the organophilic clay by NR on the basis of XRD and TEM results and to the high aspect ratio of the fluorohectorite. Apart from interca- lation, severe confinement (i.e., the collapse of the interlayer distance) of the organoclays was observed. This peculiar feature was traced to the formation of a zinc coordination complex, which extracted the amine intercalant of the or- ganoclays, thus causing the collapse of the layers. © 2003

Preparation and properties of styrene–butadiene rubber based nanocomposites: The influence of the structural and processing parameters

Abstract: Rubber-based nanocomposites were prepared with octadecyl amine modified sodium montmorillonite clay and styrene–butadiene rubber with different styrene contents (15, 23, and 40%). The solvent used to prepare the nanocomposites, the cure conditions, and the cure system were also varied to determine their effect on the properties of the nanocomposites. All the composites were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies revealed exfoliation for the modified clay–rubber composites. The TEM photomicrographs showed a uniform distribution of the modified clay in the rubber matrix. The thickness of the particles in the exfoliated composites was around 10–15 nm. Although the FTIR study of the unmodified and modified clays showed extra peaks due to the intercalation of the amine chains into the gallery, the spectra for the rubber–clay nanocomposites were almost the same because of the presence of a very small amount of clay in the rubber matrix. All the modified clay–rubber nanocomposites displayed improved mechanical strength. The styrene content of the rubber had a pronounced effect on the properties of the nanocomposites. With increasing styrene content, the improvement in the properties was greater. Dicumyl peroxide and sulfur cure systems displayed similar strength, but higher elongation and slightly lower modulus values were obtained with the sulfur cure system. The curing of the samples at four different durations at 160°C showed that the cure time affected the properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 698–709, 2004

Morphology and mechanical properties of layered silicate reinforced natural and polyurethane rubber blends produced by latex compounding

Abstract: Natural rubber (NR), polyurethane rubber (PUR), and NR/PUR-based nanocomposites were produced from the related latices by adding a pristine synthetic lay- ered silicate (LS; sodium fluorohectorite) in 10 parts per hundred parts rubber (phr). The dispersion of the LS latices in the composite was studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Further informa- tion on the rubber/LS interaction was received from Fourier transform infrared spectroscopy (FTIR) and dynamic me- chanical thermal analysis (DMTA). Tensile and tear tests were used to characterize the performance of the rubber nanocomposites. It was found that LS is more compatible and thus better intercalated by PUR than by NR. Further, LS was preferably located in the PUR phase in the blends, which exhibited excellent mechanical properties despite the incompatibility between NR and PUR. Nano-reinforcement was best reflected in stiffness- and strength-related proper- ties of the rubber composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 543-551, 2004

Mechanism of Fatigue Crack Growth in Carbon Black Filled Natural Rubber

Abstract: The present paper deals with the fatigue crack growth in a carbon black filled cis-1,4-polyisoprene rubber under relaxing loading conditions. The study focuses on the determination of the scenario of crack growth. For this purpose, an original “microcutting” method is employed to observe microscopic phenomena involved in the growth of the crack with a SEM. It reveals that the cavitation induced by the decohesion between zinc oxides and rubber matrix is the major fatigue damage and that the crack tip is composed of stretched elliptical areas surrounded by highly stretched and crystallized ligaments. Finally, the observations are considered to establish the fatigue crack growth mechanism.

Fly ash particles and precipitated silica as fillers in rubbers. I. Untreated fillers in natural rubber and styrene–butadiene rubber compounds

Abstract: In this study, we investigated the effects of untreated precipitated silica (PSi) and fly ash silica (FASi) as fillers on the properties of natural rubber (NR) and styrene- butadiene rubber (SBR) compounds. The cure characteristics and the final properties of the NR and SBR compounds were considered separately and comparatively with regard to the effect of the loading of the fillers, which ranged from 0 to 80 phr. In the NR system, the cure time and minimum and maximum torques of the NR compounds progressively in- creased at PSi loadings of 30 -75 phr. A relatively low cure time and low viscosity of the NR compounds were achieved throughout the FASi loadings used. The vulcanizate prop- erties of the FASi-filled vulcanizates appeared to be very similar to those of the PSi-filled vulcanizates at silica con- tents of 0 -30 phr. Above these concentrations, the properties of the PSi-filled vulcanizates improved, whereas those of the FASi-filled compounds remained the same. In the SBR sys- tem, the changing trends of all of the properties of the filled SBR vulcanizates were very similar to those of the filled NR vulcanizates, except for the tensile and tear strengths. For a given rubber matrix and silica content, the discrepancies in the results between PSi and FASi were associated with filler- filler interactions, filler particle size, and the amount of nonrubber in the vulcanizates. With the effect of the FASi particles on the mechanical properties of the NR and SBR vulcanizates considered, we recommend fly ash particles as a filler in NR at silica concentrations of 0 -30 phr but not in SBR systems, except when improvement in the tensile and tear properties is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2119 -2130, 2004

Organoclay–natural rubber nanocomposites synthesized by mechanical and solution mixing methods

Abstract: This investigation describes two methods to obtain rubber composites based on natural rubber (NR) and organophilic layered silicates. In order to improve the exfoliation and compatibilization of the organoclays with the rubber matrix, a new approach which involves swelling of the organoclays with an elastomer solution prior to compounding has been used. The effect of the addition during swelling of a coupling agent, namely bis(trietoxysilylpropyl)tetrasulfan (TESPT), on the behaviour of the composites was also investigated. The results show that a low amount of organoclay (10 phr) significantly improves the properties of natural rubber. This suggests a strong rubber–organoclay interaction which is attributed to a high degree of rubber intercalation into the nanosilicate galleries, as was confirmed from X-ray diffraction. In addition, an ulterior improvement in the properties of the nanocomposites prepared by solution mixing is clearly observed, due to the better filler–rubber compatibility. An even further increase in the properties is observed by treating the silicate with a silane coupling agent. The silane functional groups modify the clay surface, thus reducing the surface energy, and consequently improving the compatibility with the rubber matrix. Copyright © 2004 Society of Chemical Industry

Effect of particle size on the properties of Mg(OH)2-filled rubber composites

Abstract: A novel nanomagnesium hydroxide powder and three kinds of micro-Mg(OH)2, with different particle sizes, were chosen as fillers and mixed with ethylene-pro- pylene- diene monomer rubber (EPDM) to form a series of composites by a traditional rubber-processing technique. The results showed that the mechanical properties of com- posites improved with decreasing particle size. The nano- composites were far stronger than the microcomposites, which also supported the view that rubber reinforcement requires nanoreinforcement. The effect of particle size on the fire resistance of composites was investigated by cone calo- rimetry and limiting oxygen index analysis, which showed that the particle size of powder had an impact on the fire resistance of composites. For the composites filled with un- treated powder, the peak value of heat release rate de- creased and Tign increased with decreasing particle size. In conclusion, the fire resistance of nanocomposites was better than that of microcomposites. Surface modification of parti- cles sometimes substantially improved the mechanical prop- erties of nanocomposites, but had no effect on either the mechanical properties of microcomposites or the fire resis- tance of nanocomposites and flame retardance. © 2004 Wiley

Multiaxial Behaviors of Laminated Rubber Bearings and Their Modeling. I: Experimental Study

Abstract: Cyclic behaviors of three types of laminated rubber bearings under multiaxial loading state are studied. First, the characteristics of the restoring forces of these bearings in small amplitude are investigated. The experimental results show that the equivalent stiffness of high damping rubber bearings is increased and the damping ratio is decreased as the increase of the amplitude. In addition, the restoring force of a lead rubber bearing is found to highly depend on the vertical load. Second, a triaxial loading experiment, in which two-directional displacement paths are given to the bearings under a constant vertical load, is conducted. The experimental results indicate that horizontal restoring forces possess the coupling effects. The equivalent stiffness and damping ratio of high damping rubber bearings and natural rubber bearings are increased due to this coupling effect in comparison with the biaxial loading case, while the lead rubber bearing shows a slight decrease in them. Hence it is understood that the effects of the triaxial loading are not negligible and these have to be considered in a rational and reliable design.