Rubber Formulations Research Articles

Some Synergistic Effects of Antioxidants in Natural Rubber

Some synergistic effects of antioxidants in natural rubber were investigated considering results obtained by differencial scanning calorimetry (DSC). Rubber formulations were obtained with mixtures of diaminic(DPPD, IPPD, HPPD) and monoaminic (ADPA, PBN) stabilizers and evaluated. The samples containing the mixture diamine/ADPA stabilizers showed synergistic effects while, for those containing diamine/PBN, no effect was observed. Additionally, the diffusion constants determined by use of vulcanized rubber disks confirmed the molar mass dependence of the stabilizer.

Slow release rubber formulations containing ZnSO 4

Styrene butadiene (SBR) and natural rubber (NR) can be used as binding matrices to control the release of zinc (Zn) which is a micro-nutrient for plants. The leaching rate of zinc in an aqueous medium depends on the concentration of zinc sulphate loaded in the two types of rubber used, the temperature of the surrounding environment and the pH of the aqueous medium. Water uptake was increased with increasing concentration of ZnSO 4. The sustained release of zinc ions from the investigated formulations was prolonged for over five months. The mechanical properties of the vulcanizates were affected as the concentration of zinc sulphate changed.

Development and comparison of test methods for evaluating formation of biofilms on silicones

Silicone rubber formulations used for outdoor high voltage insulation are sometimes reported to be colonized by microorganisms. Different formulations show different sensitivity towards biological growth. In this study five rubbers were tested. Two standard practices were used, ASTM G21-90 and IEC 68-2-10. In addition a new method was developed to measure the rate of colonisation of a sample by biological growth. Results showed that the tested rubbers supported fungal growth when an external carbon source was available. Thus none of the silicones can be called bio-resistant. However the materials are not biodegradable either. This was clearly shown when mould spores were added to the samples in clean water, when none of the rubbers was contaminated. Some of the materials did, however, support growth when only nutrient salts, no carbon source, was added. The most bioresistant formulations contained the flame retardant zinc borate, indicating that this additive suppresses fungal growth. Further investigation with the new method supported that theory.

Influence of different curing systems on the physico-mechanical properties and stability of SBR and NR rubbers

The physical properties of radiation, sulfur and peroxide-cured styrene–butadiene rubber (SBR) and natural rubber (NR) were compared. The dependence of the mechanical properties of the radiation-vulcanized SBR and NR on the coagent concentration and radiation dose was studied. The effect of thermal aging on the mechanical properties of the different rubber formulations was discussed. The radiation-cured formulations of SBR have superior mechanical properties and thermal stability compared with those of the chemically vulcanized compounds. Whereas, the radiation-cured formulations of NR have similar mechanical properties but superior thermal stability (based on the % change in E after thermal aging), when compared with those of the sulfur-vulcanized compounds and slightly better than those of the peroxide-vulcanized compounds.

Controlled release of migration of molluscicidal saponin from different types of polymers containing Calendula officinalis

AbstractTriterpene saponins of marigold (Calendula officinalis; family compositae) were hydrolyzed and examined for their molluscicidal activity. It was found that 10.25 mg l−1 of the partially hydrolyzed saponin was lethal to 100% of snails after 24 h, while 50 mg l−1 of the intact saponin produced the same effect. Natural rubber, styrene–butadiene rubber, and starch were used as binding matrices for the bioactive natural products (C. officinalis) for releasing saponin in minute amounts over long periods of time. The rate of release of saponin varied according to the type of polymer matrix, the type of fillers, and the filler concentration. The rate of release extended to over 3 months when the physico‐mechanical properties of styrene–butadiene rubber formulations were improved by the presence of black and white fillers. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 305–311, 2001

Computer aided optimum design of rubber recipe using uniform design

The application of Uniform design in rubber formulation and its corresponding Group Methods of Data Handling modeling and Simulated Annealing optimization methodology are investigated. The example of NR/VBR (vinyl polybutadiene rubber with 80% of vinyl content) blend in tyre tread shows that Uniform design can distribute the experiment points evenly so as to establish mathematical models of high precision. With computer aided modeling and optimization technology, the optimum formulation can be predicted.

Acrylate‐based liquid rubber as impact modifier for epoxy resin

AbstractCarboxyl‐terminated poly(2‐ethyl hexyl acrylate) (CTPEHA) having various molecular weights were synthesized by bulk polymerization in the form of liquid rubber. The liquid rubbers (LR‐1 to LR‐4) were characterized by 13C‐NMR spectroscopic analysis, nonaqueous titration, and vapor‐pressure osmometry (VPO). The liquid rubber having the lowest molecular weight (M̄n = 3600) was prereacted with the epoxy resin and the modified epoxy networks were made by curing with an ambient temperature curing agent. The modified epoxy networks containing different concentrations of CTPEHA were evaluated with respect to their thermal and impact properties. The optimum properties were obtained at about 10–15 phr of CTPEHA concentration (phr stands for parts per hundred parts of epoxy resin). Fracture surface analysis by scanning electron microscopy (SEM) indicated the presence of a two‐phase microstructure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1792–1801, 2001

Adhesion improvement of SBR rubber by treatment with trichloroisocyanuric acid solutions in different esters

Ethyl, propyl and butyl acetates (EA, PA, BA, respectively) were used as solvents for trichloroisocyanuric acid (TCI) to chlorinate styrene–butadiene rubber (SBR). Characterization of the treated surfaces was carried out using ATR-IR spectroscopy, scanning electron microscopy (SEM), and contact angle measurements. Stress-strain measurements were also carried out to determine the mechanical properties of the treated rubber. Adhesion properties were studied using a polyurethane adhesive and the failed surfaces obtained after performing T-peel tests were analyzed in order to precisely locate the joint failure. The results showed that the solvent is a key factor in the effectiveness of the chlorination of R2 rubber. The solvents with slower evaporation rate led to more pronounced modifications on the R2 rubber surface. But these solvents could favour the migration of wax from the bulk rubber to the surface creating a weak antiadherent layer that prevented adhesion. The increase in TCI percentage in the chlorinating solution produced more marked modifications on the R2 rubber surface, avoiding the migration of wax. The solvent in the chlorinating solution also affects the effectiveness of the zinc stearate elimination from the R1 rubber surface; however, good adhesion was obtained even though this compound was not completely removed, indicating that the presence of zinc stearate in the rubber formulation did not produce a detrimental effect in the adhesion of SBRs.

Parameters Affecting the Migration of Molluscicidal Saponin from Styrene Butadiene Rubber Formulations Containing Phytolacca Dioica L.

Discs of SBR containing Phytolacca dioica L. plant can be used to release saponin of the plant which has an efficient toxic effect on Bimpholaria alexandrine snails, the intermediate hosts of Schistosomiasis. Such a snail control system is used to protect the human beings from schistosomiasis. Schistosomiasis is a major health problem of increasing severity, especially in the developing countries. High abrasion furnace black (HAF) and hydrated silica (HISIL) are some inert fillers which improve the properties of rubber, and they play an important role in controlling the porosity of controlled release styrene butadiene rubber formulations containing Phytolacca dioica L. plant. Also, the leaching rate of saponin depends on the concentration of filler, type of water, temperature of the environment as well as surface to volume ratio of the discs. The scanning electron micrographs illustrate the cracks and pore structure which are formed after release of saponin. The leaching rate of saponin from SBR/HAF filled formulation is greater than the leaching rate from SBR/HISIL filled formulation.

Effect of epoxidised liquid natural rubber on nitrile/butadiene rubber based mixes

Epoxidised liquid natural rubber (ELNR) constitutes a new family of polymers chemically derived from natural rubber. It is a highly viscous rubber of low molar mass generally used as plasticiser or processing aid, especially during processing of natural rubber and styrene/butadiene rubber stocks.The effect of incorporating this polymer rather than a standard plasticiser in a nitrile/butadiene rubber based mix has been investigated. The retention in mechanical properties following air and oil aging of the vulcanisates was also studied. Satisfactory processability of compounded stocks, mechanical properties, and aging resistance was maintained following incorporation of ELNR into nitrile/butadiene rubber formulations even at the lowest plasticiser concentrations. The improvement in aging behaviour was more pronounced when 25 mol-% ELNR was used at concentrations above 15 pphr.

Thermochemical processing of rubber waste to liquid fuel

Liquid obtained from solid rubber waste via a thermochemical conversion process is expected to play an important role in the future of energy as high value energy carriers and value added chemicals. The energy density of liquid is higher than raw rubber waste because of both chemical and physical characteristics. The Association of South East Asian Nations (ASEAN) coun tries, especially Malaysia and Indonesia, generate a significant amount of solid waste in the form of natural rubber. Leading on from the elemental composition and thermal characteristics (obtained via thermogravimetric analysis) of solid rubber waste, the production of pyrolysis liquid oil by a fixed bed pyrolysis technique has been attempted. This is both energy recovery and protection of the environment. The liquid oil may be used directly as raw fuel in diesel engines. The liquid oil was characterised by Fourier transform infrared and gas chromatography–mass spectrometry techniques for its detailed chemical composition. The fuel properties of the derived oil were also analysed and compared with petroleum products.

Diffusion of amine stabilizers in vulcanized natural rubber compositions used in tires

The diffusion of amine stabilizers in vulcanized natural rubber formulations used in tires was investigated. Experiments were undertaken using a “sandwich” system composed of a sample disk containing the additive (source disk) between two external disks of nonadditivated rubber (reception disks). Diffusion coefficients (D) were calculated from the experimental migration curves following the Boltzman–Matano model. Theoretical diffusion curves for the additives were obtained according to the limited extension source in an infinite medium. Experimental data showed reasonable fitting with the theoretical curves, suggesting that D does not depend on the additive concentration. Thermooxidative stability data for the vulcanized rubber containing the additives showed no correlation to the diffusion process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 670–676, 2000

Structure of natural rubber/emulsion butadiene rubber (NR/EBR) vulcanizates

Diblock amorphous topological structure of a filled vulcanizate network made of natural rubber (NR) and Emulsion Butadiene Rubber (EBR) was found. These blocks differ in the transition temperatures about 200°C. Dual transitions of such rubbers have been assigned as a motion of the mixed soft block [low glass transition temperature (Tg )] in the glassy state and the motion in elements of a network around physical and chemical crosslinking sites in a rigid block (high Tg ), respectively. Compaction of the topological structure of a high-temperature block during curing (manifested by the growth of Tg ) was noticed. The molecular weight distribution of the chains between the junctions of the network and shares of these amorphous blocks in the structure of the rubber network vs curing time were calculated using the methodology shown. Introduction of Perkalink 900 at constant quantity of sulfur changes a structure of the junctions in the tested rubber network from mixed (10–15% of chemical bonds, and remaining are cluster type and topological junctions) into practically all chemical bonds. Optimal curing time evaluated by the thermomechanical analysis, at which molecular structures formed in both blocks reflect the equilibrium state of adsorption layers of two rubbers introduced into the compound, is close to that evaluated by the vulcametric tests. The location of the molecular weight distribution curve in both blocks one against another depends on rubber formulation. Also, a fact that crosslinks are gathered, as was predicted by Vilgis and Heinrich calculations, was confirmed experimentally. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 732–742, 2000

Detection of Casting Material on Historical Violins by Infrared Spectroscopy and Total Reflection X-Ray Fluorescence Spectrometry

Infrared spectroscopy and total reflection X-ray fluorescence spectrometry are used for the analysis of historical varnishes. Total reflection X-ray fluorescence spectrometry is used in the analysis of the elemental composition; infrared spectroscopy is used to determine the inorganic and organic molecules of the binding media, pigments and additives. On historical violins made by A. Guarneri and L. Widhalm silicon and tin were found by total reflection X-ray fluorescence spectrometry. Silicon was proved to be present in the form of silicon rubber by infrared spectroscopy. A further experiment confirmed that the treatment of a violin with silicon rubber casting material is detectable.

Effects of fillers on mechanical properties of a water-swellable rubber

The mechanical properties of the water-swellable rubber prepared by blending polychloroprene with precipitated silica, crosslinked sodium polyacrylate, polyethylene oxide, and vulcanizing agents—such as stress at break, strain at break, modulus, energy at break, and hardness—were studied before and after swelling with water. The results showed that the addition of the reinforcing filler (precipitated silica) increased the mechanical properties, while adding crosslinked sodium polyacrylate decreased the mechanical properties, although it could improve water-absorbent properties of the water-swellable rubber. If some polyethylene oxide was included in the rubber formulation, the water-absorbent properties and the mechanical properties of the rubber both increased; but, with the increase of more polyethylene oxide, the mechanical properties decreased. Wide-angle X-ray diffracting analysis was conducted to study the crystalline behavior of the rubber, which showed that the crystallinity of the vulcanized polychloroprene increased first and then decreased with an increase in the amount of polyethylene oxide. The crosslink density of the rubber was calculated by the Flory–Rehner equation. The mechanical strength of the rubber significantly decreased after swelling with water, compared with that before swelling with water. The morphology of blends was shown by scanning electron microscopy graphs. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 577–584, 1999

集合住宅における乾式二重床の重量床衝撃音レベル低減量に関する研究

In case of dry double floorings, it is different from measured and predicted values. We measured for height of floor, rubber form and hardness, the method of supporting edge of floor, an opening space, effect of absorption material, the method of construction, and the area of floor. We proved that these factors influenced to heavy weight floor impact sound. Then, we improved the edge of joists and rubber and purposed the dry double floorings that was able to construct by the level of business and confirmed it was able to maintain performance equal to that of naked slabs.

Effect of blend ratio on Mooney scorch time of rubber blends

The Mooney scorch times of three rubber blends [epoxidized natural rubber (ENR) 50/SMR L, ENR 50/styrene butadiene rubber (SBR), and Standard Malaysian Rubber SMR L/SBR] were studied in the temperature range of 120–160°C using an automatic Mooney viscometer. N-Cyclohexyl-2-benzothiazyl sulfenamide was used as the accelerator, and the rubber formulation was based on the conventional vulcanization system. Results for the blends investigated indicate that a negative deviation of scorch time from the interpolated value was observed, especially for temperatures lower than 130°C. This observation was attributed to the induction effect of the ENR 50 in the ENR 50/SMR L and ENR 50/SBR blends to produce more activated precursors to crosslinks, thus enhancing interphase crosslinking. To a lesser extent, SMR L also exhibited such an induction effect in the SMR L/SBR blend. At 120°C, maximum induction effect occurred at around a 40% blend ratio of ENR 50 and SMR L in the respective blends. For the filled stock at 140°C, carbon black exhibited less effect on the scorch property of the blends compared to silica. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1301–1305, 1998

Studies on the Processability of Different Forms of Natural Rubber UsingTorque-rheometer

Haake-Rheocord-90 instrument has been used to study the rheological behaviour of different forms of natural rubber. Since the design of the mixing head of the equipment is similar to that of and internal mixer, the behaviour of the rubber in actual processing can be estimated.

Nitrosamine Formation in Rubber: I. Influence of Mixing History

Abstract Despite much published research, the influence of fillers on nitrosamine formation in accelerated sulphur vulcanization is not well understood. This paper studies N-nitrosodimethylamine (NDMA) formation in a range of TMTD-accelerated, black-filled rubber formulations encompassing EPDM, SBR, NR, and NBR rubbers. Two levels of TMTD and carbon black were variables in this study as was the type of carbon black used (N330 and N550). The use of statistical experimental design has shown how reliable data on nitrosamine formation in vulcanizates can be obtained by paying strict attention to process history, and has revealed, for the SBR, NR, and NBR rubbers studied, a correlation between the temperatures reached on mixing with the level of nitrosamine generated on subsequent vulcanization. For these rubbers the effect of this process history outweighs that of any ingredient variable. While allowing new insights to be gained on nitrosamine formation in rubber, these findings allow the development of a self-consistent mechanism for nitrosation processes where the reactions in diene rubbers mirror those in air.

Design of Novel Treated Silica Xerogels: Synthesis, Property and Reinforcement in Silicone Elastomers

ABSTRACTTreated silica xerogels with controlled porosity and surface area were prepared by the in-situ treatment of hydrogels with hexamethyldisiloxane in the presence of isopropyl alcohol. The resulting hydrogels were hydrophobic and readily transferred to organic solvents allowing their isolation. The surface area and porosity of the xerogel were controlled by varying the pH, time and temperature used to aggregate the hydrogel prior to treatment. The treated xerogels were evaluated as reinforcing fillers in silicone rubber formulations. When the bases were crosslinked with peroxides, silicone elastomers with acceptable mechanical properties were obtained. The relationship between the surface area, porosity and the type and degree of surface treatment of the xerogel, and its reinforcing ability was studied. In general, the mechanical properties of the elastomer increased as the filler structure increased; however, xerogels with higher surface areas were more difficult to incorporate and gave higher plasticity bases.