Adhesion Of Rubber Research Articles

Utilization of Raw Gypsum as Hydrated Filler in Bagasse Particleboard Bonded with a Formaldehyde-Free Epoxidized Natural Rubber Adhesive

The present study described the feasibility of using raw gypsum as filler to improve the flame retardant and mechanical properties of particleboard (PB) prepared from bagasse. The PB was made with a formaldehyde-free adhesive based on epoxidized natural rubber (ENR) latex via a hot pressing process. The effect of gypsum loading on the mechanical properties of the PB was initially investigated. Both the tensile strength and modulus of rupture (MOR) of the PB tended to increase with increasing gypsum loading and reached the maximum values at 150 phr. The incorporation of gypsum into the PB beyond this loading level brought about a decrease in the corresponding properties. A horizontal burning test was conducted to determine the flame retardant properties of the PB (i.e., elapsed time and burning rate). The PB containing 150 phr of gypsum (PB-150G) was found to have a much shorter elapsed time and a lower burning rate than the PB with no gypsum added. The lower values of the corresponding properties indicated the better flame retardancy of PB. It was also found that the PB-150G exhibited a comparable level of flame retardancy to the PB containing 8 wt% of total flame retardants (i.e., 5 wt% magnesium chloride in combination with 3 wt% antimony trioxide) based on the combined weight of bagasse and ENR contained in the PB. These results revealed that the use of an appropriate amount of gypsum as filler could significantly enhance the flame retardancy with considerable improvement in the mechanical properties of BP.

Effect of cross-linking on adhesion property of benzoyl-peroxide-cured epoxidized natural rubber (ENR 50) adhesives

The loop tack, shear and peel strength of cross-linked epoxidized natural rubber (ENR 50)-based adhesive were investigated. Coumarone–indene resin and toluene were used as the tackifier and solvent, respectively, throughout the study. Benzoyl peroxide was used to cross-link the ENR 50 adhesive at 80°C for 30 min. The dosage of benzoyl peroxide was varied from 1 to 5 parts per hundred parts of rubber (phr). The adhesive was coated on the polyethylene terephthalate substrate at various coating thickness using a SHEEN hand coater. Loop tack, shear and peel strength were determined by a Llyod adhesion tester operating at 30 cm min−1. The result shows that loop tack and peel strength of the ENR 50 adhesives indicate a maximum value at 2 phr of benzoyl peroxide dosage. This observation is attributed to the effect of optimum cross-linking of rubber chains that enhances the cohesive strength of the adhesive system. However, shear strength increases with increasing dosage of benzoyl peroxide, an observation that is associated with the steady increase in the cohesive strength resulting from increasing cross-linking of rubber chains. In all cases, the adhesion properties increase with increasing coating thickness.

Improvement of the adhesion properties of silicone rubber by the incorporation of silane‐modified montmorillonite

AbstractA silicone rubber precursor was amended by the incorporation of γ‐aminopropyl triethoxysilane (APS) into siloxane to prepare an elastomeric thermal insulator adhering to the isocyanate‐group‐containing liner sheets, which are actually used to envelop rocket propellants. This improved adhesion may protect the liners of the rocket motor cases efficiently against the hot combustion gas. Clay was modified by cationic exchange with an amine compound, and the resulting clay was further treated with APS and N‐(2‐aminoethyl)‐3‐aminopropyl trimethoxysilane to introduce amine groups onto the surface of the clay to further improve the adhesion of the silicone rubber to the liner. The neat and modified clays were compounded with the APS‐amended silicone rubber [room‐temperature vulcanizate (RTV)]. The effects of the clay modification on the adhesion properties were explored. The peel strength between the liner and the room‐temperature silicone rubber (RTV) based on siloxane was 0, whereas the peel strength increased to 3.7 N/cm when the silicone rubber was amended with APS. The peel strength between APS–RTV and the liner was lower than 3.7 N/cm when clay was added, whereas the peel strength became higher than 5.7 N/cm so that APS–RTV could not withstand the peeling force and was torn off before the delamination when the amine silane modified clay was added instead of clay. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Determination of partition and diffusion coefficients of components of two rubber adhesives in different multilayer materials

Rubber adhesives both natural and synthetic are widely used in the manufacture of multilayer laminates, commonly used as food packaging. For this reason, it is very important to identify the compounds that could migrate from the laminate into the food. Twenty nine compounds were identified in two different rubber adhesives, some of them with high toxicity levels according to the theoretical model of Cramer such as benzene 4-cyanocyclohexene and benzene isothiocyanate. Partition of these compounds between the adhesive and different substrates and diffusion in both media were experimentally determined obtaining great variability of values depending on the properties of the compounds and the substrates used. Finally, only three compounds were found to migrate: benzene 4-cyanocyclohexene, butylated hydroxytoluene and 2-cyclopentyl-1.3.5-trimethylbenzene, with values of migration of 1.79, 22.9μg/dm2 and 4.57μg/dm2 respectively. These values were below the specific migration limits (SML) enforced by the legislation of the European Union (EU) and the values recommended by Cramer.

Viscoelastic properties of short aramid fibers‐reinforced rubbers

AbstractAmong short fiber‐reinforced composites, those with rubber matrices have gained great importance due to the advantages they have in processing and low cost, coupled with high strength. These composites combine the elastic behavior of rubbers with strength and stiffness of fibers. Reinforcement with short fibers offers attractive features such as design flexibility, high modulus, tear strength, etc. The degree of reinforcement depends upon many factors such as: the nature of the rubber matrix, the type of fiber, the concentration and orientation of the fibers, the fiber to rubber adhesion and fiber length. One of the main features related to this class of composites is their hysteretic properties which are of great importance especially in dynamic applications such as tire treads. In this research, short aramid fibers with different kinds of surface treatments: Standard finish and resorcinol formaldehyde latex (RFL)‐coating, have been applied in two different carbon black filled rubber compounds based on natural rubber (NR) and ethylene propylene diene rubber (EPDM). The dynamic properties of the compounds have been measured as influenced by the different kinds of fiber treatments on rubber‐fiber interaction. Finally, the contribution of the interfaces and/or interphase layers to the loss properties is characterized. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

INVESTIGATION OF THE INFLUENCE OF STEARIC ACID ON RUBBER–BRASS ADHESION

Abstract The influence of stearic acid loading on the adhesion of rubber to brass-plated steel wires was investigated. The so-called squalene method was employed to investigate the adhesion interface built up during the vulcanization reaction. Variation of the stearic acid loading has a direct influence on the bonding interface and at the same time also has a strong influence on the rubber properties. The surface of the sulfidated wires was analyzed using optical, focus variation, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Increasing amounts of stearic acid accelerated the sulfidation reaction. Furthermore the focus variation microscopy data were used to calculate roughness parameters of the sulfidated wires. Rubber properties and adhesion values were measured for natural rubber compounds with variable amounts of stearic acid. In most cases the adhesive strength exceeded the cohesive strength of the rubber.

Improvement of the properties of plasma‐modified ground tire rubber‐filled cement paste

AbstractThe thesis investigated that the adhesion of ground tire rubber (GTR) to cement can be improved by applying surface plasma modification. The hydrophobic surface of GTR powder has been transformed to a hydrophilic one through plasma treatment. Attenuated total reflectance Fourier transform infrared spectral studies showed the increase in peak intensity at the range of 1400–1600 cm−1, indicating the generation of carbon–carbon double bond after plasma treatment on the surface of the GTR powder. The X‐ray photoelectron spectroscopic analysis further confirmed the presence of oxygen‐containing polar functional groups on the surface of the GTR powder after atmospheric plasma treatment. The improvements in plastic deformation and elastic deformation that attributed to the enhanced interfacial interaction between modified GTR powder and cement matrix were observed for the modified GTR‐filled cement paste via triaxial test. The pore size distribution testing manifested a better compactness of plasma GTR‐filled cement paste. Besides, scanning electron microscope illustrated that adhesion of modified GTR powder with cement matrix increased. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

An Analytical Thermodynamic Approach to Friction of Rubber on Ice

ABSTRACT The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.

Rubber Adhesion to Different Substrates and Its Importance in Industrial Applications: A Review

In comparison to traditional industrial uses and applications of rubber compounds, the modern industrial demands have resulted in the development of new rubber compounds with improved heat, chemical, wear and impact resistances. In these applications, the adhesion strength of rubbers to different substrates is very important. In order to achieve maximum rubber adhesion to metals, plastics and fibers, usually a decrease in interfacial tension, and interaction and chemical bonding between rubber chains and substrate molecules are required. In recent years, for increasing the effective specific surface, particles such as silica and nanoclay have been incorporated in the rubber compounds. In this paper, we have focused on important parameters promoting rubber adhesion such as reactivity, compatibility, crosslinking and surface treatments. Also, adhesion theories and mechanisms related to rubber adhesion to different substrates are briefly reviewed.

Electrostatic Interactions: An Effective Mechanism for Rubber Adhesion and Blending

Deryagin introduced electrostatic adhesion many years ago but it was later considered unimportant, largely due to the difficulties in making eproducible electrostatic measurements and to the lack of clear understanding about the mechanisms for insulator electrostatic charging. More recently, electric force microscopy results on latex, polymer latex blends, and nanocomposites have shown the ubiquity of domains with excess charge, in every polymer material. In some cases, excess charge was identified by analytical transmission electron microscopy as the result of excess ions (positive or negative) concentration distributed throughout the coexisting phases and interfaces. Interaction between charged domains within nanostructured rubber blends and composites prepared from aqueous dispersions may thus contribute to their stability and mechanical properties. This article shows charge distribution patterns in one natural rubber blend, together with elemental and electric potential maps for rubber latex films from two commercial sources, evidencing large differences that were not previously reported. Electrostatic adhesion effectiveness in the making of a multicomponent system is demonstrated by casting films from a natural rubber-starch-clay nanocomposite, from aqueous dispersions and without using any sort of chemical modification or compatibilizing agent. Microscopy examination of these films show parallel clay lamellae finely interspersed within polymer, which accounts for the singular macroscopic tensile behavior of this material, with modulus in the 70 MPa range together with 500% elongation.

Synthesis on Modified Chloroprene Rubber Adhesive Dedicated to Bonding UHMWPE and 45# Steel

Methyl methacrylaten (MMA) was used to solution graft onto and modify chloroprene rubber (CR) to improve its adhesive strength. And chlorinated polyethylene (CPE) and magnesium oxide (MgO) were added to the optimum formula system of CR/MMA adhesive to prepare a better adhesive effect of CR/MMA/CPE /MgO adhesive dedicated to bonding UHMWPE and 45# steel. The performance of adhesive film was analyzed by Infrared spectroscope (IR), X-ray diffraction (XRD) and Comprehensive thermal analysis (TG-DTG). The results show that CR being grafted and modified by MMA and adding CPE and MgO in the optimum formula of CR-MMA adhesive can improve itself bonding effect of glue solution and the wetting effect of glue solution onto bonding interface, and all helped to improve bonding strength. Adding 18% of CPE and 8% of MgO (in relation to CR) in the optimum formula of CR-MMA which bonding strength is up to 0.8013MPa could make the prepared composite adhesive’ s bonding strength reach 1.2048MPa and heat resistance temperature be up to about 200°C.

Atmospheric Plasma surface treatment of Styrene-Butadiene Rubber

Thermoplastic rubbers are widely used in a large number of applications (e.g. footwear, adhesives manufacturing, molded or extruded goods). Due to the non-polar nature of these rubbers, poor adhesion is achieved with polar polyurethane (PU) adhesive thus, a surface treatment is required to chemically modify the rubber surface and produce suitable joints. Surface treatments have been demonstrated to be suitable for the improvement of adhesion and wettability properties of non-polar synthetic rubbers. Over the last two decades progresses in adhesion of rubber were achieved by changing of the ingredients in rubber composition or by modifying surfaces by the use of a chemical agent (halogenation, cyclization, etc.) or using high energy irradiation such as bombarding the surface by electron beam or gamma irradiation. Actually, wet-chemical treatments are not well acceptable because of environmental and safety considerations and question on uniformity and reproducibility. Plasma surface treatment process was been proposed as an environmentally friendly and have gained large acceptance because it can be easily integrated into existing production lines and because their effectiveness in the treatment of several materials with different shapes and sizes. The effectiveness of plasma treatment on enhancement of adhesion depends on the gas used to generate the plasma and also on the formulation of the rubber. Vulcanized rubbers like, styrene-butadiene rubber (SBR), are especially difficult to bond due to low molecular weight ingredients in their formulation that may migrate to the rubber surface limiting its interaction with the adhesive. This study attempts to find an alternative treatment to improve the adhesion of SBR surface and PU adhesive. Plasma treatments were performed in an air plasma system from Acxys and were selected three types of SBR rubbers with different percentages of styrene-butadiene which were provided by Procalcado. The effect of experimental variables such as distance, speed and scan number on the adhesion of PU adhesive was evaluated and compared with halogenated SBR rubbers.

Influence of the Treatment with Sulfuric Acid on Adhesion of Natural Rubber and Cast Polyurethane Elastomers

In this study, natural rubber (NR) was treated with sulfuric acid to improve its adhesion properties to polar polymer. T-peel strength tests, scanning electron microscopy, contact-angle measurement (water), Energy Dispersive X-ray Detector were used to analyze the nature of the NR surface modifications which were carried out with sulfuric acid. A noticeable decrease in contact angle was observed on the rubber surface by contact-angle measurements which can be ascribed to the increase of oxidized moieties on the rubber surface. EDX revealed that oxidized moieties were created through treatment with sulfuric acid. The surface modification and mode of bond failure were studied by scanning electron microscopy (SEM). Immersion in sulfuric acid for 15min produced the maximum adhesion strength (10kN/m) and produced a mixed failure mode (interface & rubber failure in the rubber). Treatment with sulfuric acid produced improved wettability as well as chemical (surface oxidation) and morphological modifications (roughness) of the rubber surface.

Influence of the Treatment with Sulfuric Acid on Adhesion of Natural Rubber and Cast Polyurethane Elastomers

In this study, natural rubber (NR) was treated with sulfuric acid to improve its adhesion properties to polar polymer. T-peel strength tests, scanning electron microscopy, contact-angle measurement (water), Energy Dispersive X-ray Detector were used to analyze the nature of the NR surface modifications which were carried out with sulfuric acid. A noticeable decrease in contact angle was observed on the rubber surface by contact-angle measurements which can be ascribed to the increase of oxidized moieties on the rubber surface. EDX revealed that oxidized moieties were created through treatment with sulfuric acid. The surface modification and mode of bond failure were studied by scanning electron microscopy (SEM). Immersion in sulfuric acid for 15min produced the maximum adhesion strength (10kN/m) and produced a mixed failure mode (interface & rubber failure in the rubber). Treatment with sulfuric acid produced improved wettability as well as chemical (surface oxidation) and morphological modifications (roughness) of the rubber surface.

Nylon 6/clay nanocomposite filaments and their cords

AbstractThe present study focuses on the preparation and characterization of nylon 6/clay nanocomposite filaments and their cords. Two different organo modified clays: the ditallodimethyl ammonium salt with bentonite clay (Claytone HY), a commercially available clay from M/S Southern Clay products, USA and silane modified montmorillonite clay (Silane‐MMT), synthesized in the laboratory were used to prepare nylon 6/clay nanocomposite filaments. The nanocomposite filaments were tested for tensile and creep properties and compared with nylon 6/sodium montmorillonite (Na‐MMT) nanocomposite filaments as well as neat nylon 6 filaments. The clay dispersion within the nanocomposite filaments was analyzed by using X‐ray diffraction (XRD), scanning electron (SEM), and transmission electron microscopy (TEM). The creep resistant property of all the nanocomposite filaments showed 10–19% improvement over the neat nylon filament. However, there is a marginal improvement in tenacity in case of nylon 6/silane MMT nanocomposite filament as compared to the neat nylon filament. All the nylon 6/clay nanocomposite filaments were converted into the cords and tested for various tire cord related properties such as tensile strength, rubber to cord adhesion, and fatigue resistance. The nanocomposite cords showed a significant improvement in tensile property (7–21%) as well as cord to rubber adhesion strength (34–55%) over the neat nylon cords, however, the fatigue resistance was inferior in case of nanocomposite cords. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Study on the Thermal Degradation Kinetics of Modified Chloroprene Rubber Adhesive Dedicated to Bonding UHMWPE and 45# Steel

Modified neoprene adhesive dedicated to bonding UHMWPE and 45# steel was prepared. Thermal analysis with TG-DTG curve was determined and its thermal decomposition kinetics was studied. The result show that the thermal degradation process of CR/MMA/CPE/MgO adhesive is a three-step reaction and the its thermal degradation starting temperature is 200°C and complete decomposition temperature is 570°C. The first mass loss stage is 0.6 order chemical reaction and its average activation energy E is 19.21kJ/mol and pre-exponential factor A is 3.68×102. The second mass loss stage is 3 order chemical reaction and its average activation energy E is 82.14kJ/mol and its pre-exponential factor A is 1.52×108. The third mass loss stage is 3 order chemical reaction and its average activation energy E is 55.07kJ/mol and pre-exponential factor A is 1.33×105.

Influence of the Configuration of the Plasma Chamber on the Surface Modification of Synthetic Vulcanized Rubber Treated with Low‐pressure Oxygen RF Plasma

AbstractThree different configurations of RF low‐pressure oxygen plasmas were used to modify the surface of vulcanized styrene–butadiene rubber. Direct, etching and downstream oxygen plasma treatments of the rubber were carried out for length of treatment between 1 and 10 min. The oxygen plasma treated rubber surfaces were characterized by ethylene glycol contact angle measurements, ATR‐IR and XPS spectroscopy and scanning electron microscopy (SEM). Adhesion of the oxygen plasma treated rubber to polyurethane adhesive was carried out by means of T‐peel test and the loci of failure of the joints were characterized by means of ATR‐IR spectroscopy. Three different oxygen plasma configurations obtained by changing the position of the rubber sample in the plasma chamber and by changing the shelves (power, ground, floating) were used to modify the extent of surface modification and the temperature reached on rubber surface. The direct oxygen plasma was the most aggressive treatment and the secondary downstream plasma the less one. The increase in the length of the oxygen plasma treatment allowed the most efficient removal of antiozonant paraffin wax from the as‐received rubber. Furthermore, the oxygen plasma treatments created CO moieties on the rubber surface. On the other hand, only 1 min treatment time was sufficient to decrease noticeably the contact angle value on the rubber surface, irrespective of the oxygen plasma chamber configuration and the length of treatment. Oxygen plasma treatment caused surface oxidation and ablation on the rubber surface, as well as an increase of the temperature that also determined the extent of paraffin wax migration, the migration was favoured for temperature higher than 45 °C. Finally, the migration of paraffin wax was produced for at least 24 h after oxygen plasma treatment and poor adhesion to polyurethane adhesive was obtained, due to the creation of a weak boundary layer of paraffin wax at the rubber–polyurethane interface. The migration of paraffin wax caused during plasma treatment was the dominant factor in decreasing the adhesion of rubber to polyurethane adhesive.magnified image

Toxicity of Methylcyclohexane and Its Effect on the Reproductive System in SD Rats

ObjectivesThere is limited data regarding the toxicity of methylcyclohexane, despite its wide use in rubber adhesives, paint diluents, and cleansing agents. This study aimed to verify the toxicity and influence on the reproductive system of methylcyclohexane after its repeated injection in Sprague Dawley (SD) rats.MethodsMethylcyclohexane was injected subcutaneously into male and female SD rats once a day, five times a week, for 13 weeks at different doses (0, 10, 100, and 1,000 mg/kg/day) for each group. The toxicity of testing material was verified by observing the change in body and organ weight, hematological change, pathological findings, and effect on the reproductive system at each different concentration.ResultsIn the 1,000 mg/kg/day group, there were cases of animal deaths. In animals that survived, hematological changes, including a decrease in the red blood cell count, were observed. A considerable weight gain or loss and pathological abnormalities in the liver, kidney, and other organs were found. However, the 10 and 100 mg/kg/day groups did not cause deaths or other specific abnormalities. In terms of reproductive toxicity, there were changes in hormone levels, including a significant decrease in hormones such as estradiol and progesterone (p < 0.001) in male animals. Menstrual cycle change for female animals did not show concentration dependency.ConclusionWhen injected repeatedly for 13 weeks, methylcyclohexane proved to be toxic for the liver, heart, and kidney at a high dose. The absolute toxic dose was 1,000 mg/kg/day, while the no observed adverse effect level was less than 100 mg/kg/day. The substance exerted little influence on the reproductive system.

Dynamic systems with rubber contacts in technical applications

This work deals with the experimental investigation and modelling of adhesion and friction of rubber. With the recently developed adhesion test rig, the contact partners can rapidly be separated while the contact force is measured. The results reveal a strong influence of the preload duration and preload level. Furthermore, a modular modelling concept for dynamic systems with rubber components undergoing sliding friction is presented and exemplified by a tyre tread block. The model considers the geometry of the rubber component, the parameter dependent friction, the roughness induced non-linear contact stiffness and the wear effects. The measurements of high frequency, self-excited tread block vibrations are performed on a tribometer test rig and compared to corresponding simulations with the proposed model.

Improved adhesion of silicone rubber to polyurethane by surface grafting

AbstractPolyurethane (PU) has widespread applications in implantable devices because of its excellent mechanical and biocompatible properties, whereas weak biostability limits its long‐term implantation. The introduction of silicone rubber (SR) onto the PU surface is an effective method for improving the biostability of PU, but the adhesion of these two polymers is unsatisfactory. In this study, the surface modification of PU via grafting through the introduction of vinyl and SiH groups onto the PU surface was attempted to improve the adhesion of PU to SR. Fourier transform infrared, energy‐dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy were employed to investigate the graft reaction on the PU surface. The interfacial and surface morphology was characterized with scanning electron microscopy. Different PU/SR interfaces after oscillation and shear were compared as well. The results indicated that the PU surface was activated by diisocyanate, which generated free isocyanate groups for the further grafting of vinyl and SiH groups. When addition‐type, room‐temperature‐vulcanized SR was poured onto the PU surface, the vinyl and SiH groups on the PU surface underwent an addition reaction, which improved the adhesion of PU and SR by connecting them with chemical bonds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011