EPDM Vulcanizates Research Articles

Nylon 66 short fiber reinforcement in EPDM power transmission belting: A path to enhanced mechanical performance

AbstractV‐belts are commonly used to transmit power between two distant pulleys. Therefore, a strong reinforcement for dimensional stability and thermomechanical properties are essential in power transmission belts. The influence of resorcinol formaldehyde resin (RFL) treated nylon short fibers in EPDM peroxide‐cured formulations was investigated, with concentrations ranging from 0 to 30 parts per hundred rubber (phr) in increments of five. The incorporation of nylon short fibers resulted in improved tensile and mechanical properties in EPDM vulcanizates. Specifically, the tensile stress at 100% elongation increased by 177% to (10.8 MPa), and the improvement in tear strength to 16.2% (75.7 N/mm) was observed. Among other functional requirements in a weak rubber like EPDM, enhanced tear strength is significant for its application in power transmission. Substantial reinforcement between the fiber‐elastomer matrix was confirmed via scanning electron microscopy, as evidenced by increased storage modulus (E′). Notably, there were no considerable effects on the curing rate or low‐temperature properties. Significant improvement in heat stability is observed through thermogravimetric analysis. These enhancements in mechanical and thermal properties might play a role in increased durability and performance in actual V‐ribbed belt applications.Highlights This manuscript describes the effect of treated nylon 66 short fiber on EPDM V‐belt compound. A significant increase in storage modulus, tear strength, and thermal stability. A belt is made using the experimental formulation and it meets the performance requirement. Low fiber content (<15 phr) compounds are unsuitable for dimensional stability. High fiber content (>25 phr) compounds pose processing challenges.

Enhancement of aging resistance ofEPDMrubber by naturalrubber‐g‐N(4‐phenylenediamine) maleimide as a grafted antioxidant

AbstractA new antioxidant was prepared by graft copolymerization ofN(4‐phenylenediamine) maleimide (pPDAM) onto natural rubber (NR). Fourier transform infrared technique was used to confirm the grafting of (pPDAM) onto the NR backbone. The grafted copolymer (NR‐g‐pPDAM) was incorporated into the ethylene propylene diene monomer rubber (EPDM) rubber mix as an antioxidant. For comparison purposes, a widely used antioxidantN‐(1,3‐dimethylbutyl)‐N′‐phenyl‐p‐phenylenediamine (6PPD) was used in addition to a blank sample without antioxidant. The rheometric characteristics of EPDM vulcanizates were determined using an oscillating disc rheometer. Different mechanical properties of the EPDM vulcanizates were measured before and after exposure to thermal and ultraviolet/ozone (UV/O3) accelerated aging. The results revealed that the grafted antioxidant NR‐g‐pPDAM is more efficient, for EPDM rubber vulcanizates than the commercial antioxidant (6PPD). EPDM containing grafted (NR‐g‐pPDAM) antioxidant exhibited promising properties, such that it is expected to fulfill major requirements of industrial, automotive, and construction applications.

Effects of Basalt and Carbon Fillers on Fire Hazard, Thermal, and Mechanical Properties of EPDM Rubber Composites.

Due to growing restrictions on the use of halogenated flame retardant compounds, there is great research interest in the development of fillers that do not emit toxic compounds during thermal decomposition. Polymeric composite materials with reduced flammability are increasingly in demand. Here, we demonstrate that unmodified graphene and carbon nanotubes as well as basalt fibers or flakes can act as effective flame retardants in polymer composites. We also investigate the effects of mixtures of these carbon and mineral fillers on the thermal, mechanical, and rheological properties of EPDM rubber composites. The thermal properties of the EPDM vulcanizates were analyzed using the thermogravimetric method. Flammability was determined by pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry.

Task-Specific Ionic Liquids with Lactate Anion Applied to Improve ZnO Dispersibility in the Ethylene-Propylene-Diene Elastomer.

Task-specific ionic liquids (TSILs) are ionic liquids with structures and, consequently, properties and behaviors designed for particular applications. In this work, task-specific ILs with alkylammonium or benzalkonium cations and carboxyl groups in the form of lactate anions were used to promote the homogeneous dispersion of the curatives in the elastomer matrix. The reaction of carboxyl groups of TSILs with zinc oxide, which acts as a vulcanization activator, was confirmed. This interaction improved the solubility and dispersibility of zinc oxide particles in the ethylene-propylene-diene (EPDM) monomer matrix, which consequently affected the curing characteristics of rubber compounds. Most importantly, TSILs increased the efficiency of vulcanization by shortening the time, lowering the temperature and increasing the enthalpy of this process, while maintaining safe processing of elastomer composites. EPDM vulcanizates containing TSILs with lactate anion were characterized by satisfactory functional properties.

A potential utilization of end-of-life tyres as recycled carbon black in EPDM rubber

End-of-life (EOL) tyres and their decomposition present severe environmental concern due to their resistance to moisture, oxygen, natural degradation, etc. Pyrolysis is considered to be the most effective and sustainable process for recycling, due to its eco-friendly process. The current work studied the effect of recycled carbon black (rCB), obtained from the pyrolysis of EOL tyres, on the properties of ethylene propylene diene rubber (EPDM). The rCB was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and chemical methods. rCB was incorporated solely, into a conventional EPDM formulation and also in combination with N550 carbon black. The physico-mechanical properties of the EPDM vulcanizates, before and after aging, were succinctly studied by SEM, TGA, Differential Scanning Calorimetry (DSC), tensile tests and cross-link density. The average particle size of rCB was observed to be 8 µm and the ash content was observed to be higher when compared to the conventional N550 carbon black, which was evident, by the TGA and SEM-EDX analyses. The reinforcing effect and the cross-link density of the rCB-filled vulcanizates were found to be marginally inferior in comparison to the conventional carbon black (N550). The morphology of the tensile- and tear-fractured surfaces were studied by SEM and it was observed that the breaking mechanism follows the rubber chain detachment from the surface mode.

Study on Thermo-Oxidative Aging of EPDM Vulcanizates : Relationship between Tensile Breaking Stretch Ratio and Average T<sub>2</sub> Relaxation Time of Rubber Phase

Study on Thermo-Oxidative Aging of EPDM Vulcanizates : Relationship between Tensile Breaking Stretch Ratio and Average T<sub>2</sub> Relaxation Time of Rubber Phase

PEROXIDE CROSS-LINKING OF EPDM USING MOVING DIE RHEOMETER MEASUREMENTS. II: EFFECTS OF THE PROCESS OILS

ABSTRACT A series of compounds based on peroxide-cured ethylene–propylene–diene monomer rubber (EPDM) was prepared with varying amounts of paraffinic process oil, such as Sunpar 2280, squalane, and dodecane. The cross-linked network composition of EPDM vulcanizates, which correlated directly with the structure and the concentration of process oils, was successfully carried out by either an exponential or a linear fitting procedure. It was found that an increase in process oil concentration caused a decrease in total cross-link density, which could be quantitatively divided into the effect of dilution and chemical effect of oil, represented as a linear and an exponential function of process oil concentration, respectively. Experimental results indicated that whether dilution effect or chemical effect, the addition of Sunpar 2280 affected the decrease of cross-link densities of EPDM vulcanizates most obviously, followed by squalane, and then dodecane, which was the weakest. On the other hand, at lower squalane loading, the chemical effect of squalane dominated the decrease of cross-link density of peroxide-cured EPDMs compared with the dilution effect of oils. Gel permeation chromatography spectra confirmed squalane could consume the free radicals derived from peroxide, forming dimers and trimers, and the variation of squalane content did not affect the activation energy of the cross-linking reaction calculated based on the Kissinger method. The cross-linking efficiency of peroxide and physical entanglement density both linearly decreased with the increase of squalane content.

Improvement of hardness and compression set properties of EPDM seals with alternating multilayered structure for PEM fuel cells

In Proton Electrolyte Membrane (PEM) fuel cells, seals are used to keep intimate contact between all components as well as to keep the reactant gases and liquid within their respective regions. Suitable seal materials should be chosen and designed to sustain the long term operation. In this paper, EPDM seal materials with soft and hard alternating multilayered structure are fabricated through the multilayered co-extrusion system. The structure and morphology of multilayered and blended EPDM vulcanizates were observed by Scanning electron microscopy (SEM). The results of tensile, hardness, compression set and compression stress relaxation test show that multilayered vulcanizates have lower tensile strength and compression set but higher hardness than blended one. The hardness of multilayered vulcanizates increases with the increase of the layer number, leading to higher sealing force and better dimensional stability. The compression set of multilayered vulcanizates decreases with the increase of the layer number, indicating better sealing capacity and longer working life. The permeability test shows that multilayered materials have nearly same gas permeability property as blended one. The results of aging test reveal that the mechanical properties of EPDM seal materials decrease with time, but multilayered vulcanizates still have lower compression set than blended one after aging.

EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

ABSTRACTThe theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

Mechanism of formation of fine rubber powder from ternary ethylene–propylene–diene vulcanizates

The process of comminution of EPDM vulcanizates with different content of plasticizer (paraffin oil) is studied. A sol–gel analysis is performed, and the crosslink density in the rubber powders obtained is determined. The surface morphology of these rubber powders is examined by scanning electron microscope. The surface of the particles shows characteristic regions of plastic and brittle fracture. A model of the structure of particles of rubber powders is proposed.

Rheological properties of ethylene-propylene-diene elastomers

The processing of rubbers comprises a combination of complicated processes which realization almost always requires knowledge of their rheological behavior. The goal of the present work is to describe the rheological behavior of the EPDM vulcanizates via rotational rheometry. The effect of the cross-linking density and plasticizer content on the rheological behavior of the EPDM vulcanizates is described. The viscoelastic characteristics of the samples are defined from the frequency dependences of elasticity modulus G' and loss modulus G".

Effects of Co-Agents on the Properties of Peroxide-Cured Ethylene-Propylene Diene Rubber (EPDM)

ABSTRACTThe influence of three different co-agents, triallyl isocyanurate (TAIC), trimethylol propane trimethacrylate (TMPTMA) and high vinyl poly(butadiene) (HVPBd), on the curing characteristics, including the cure kinetics, of peroxide-cured EPDM compounds and the mechanical properties of the resulting EPDM vulcanizates were studied. The results showed that the addition of each co-agent could improve the cure extent of the EPDM samples; the hardness and modulus of the EPDM vulcanizates were also improved. In particular, the compound containing TAIC obtained the highest cure extent. However, the addition of TMPTMA negatively affected the scorch safety, especially below 165°C. From the cure kinetics of the EPDM compounds, obtained by using the cure data from a moving die rheometer, it was found that the Deng–Isayev, first-order and Hsich models showed better agreement with experimental data compared to the Kamal–Sourour model. The reaction rate constants were gradually increased with the elevated temperature, and TMPTMA could significantly promote the curing reaction rate, TAIC secondly, while HVPBd showed no effect. In addition, the apparent activation energy of all EPDM compounds, calculated by the Deng–Isayev model, was estimated slightly higher than that of the other three kinetic models. However, due to the addition of the three co-agents, the activation energy of the curing reaction decreased, with the EPDM compound with TAIC showing the lowest activation energy.

Mechanical and dismantlement adhesion properties of grafted EPDM-silica hybrid

This study was carried out to confirm the effects of functional groups that could derive secondary bonding and silica contents on mechanical properties and thermo-reversible characteristics of grafted EPDM-silica composites, which was produced by blending silica or introducing silica hybrid through ionic bonding after grafting methacrylic acid onto EPDM. The storage modulus of graft copolymer had appeared to be higher than cross-linked EPDM vulcanizate at room temperature, and decreased by a gentle slope as temperature increased, and then began to decrease more sharply as secondary bonding force became weaker at higher temperature. When silica hybrid was introduced through ionic interaction, storage modulus and mechanical properties were found to be higher due to not only hydrogen and ionic bonding, but also nanosized silica particles, which were bonded to the elastomer structure in uniformed distribution. When the graft copolymer had only hydrogen bonding, recycling of the elastomer caused mechanical properties to be reduced by 20–30%. However, the recycling characteristics of elastomers having both hydrogen and ionic bonding were excellent as more than 90% of their initial mechanical properties were maintained even after five times of reprocessing. Graft copolymer composite had better adhesion strength with other rubber due to increased polarity than EPDM, and dismantlement of bonded adherends was possible by applying heat treatment of microwave.

카르복시산을 포함하는 Grafted EPDM의 접착특성에 관한 연구

EPDM에 카르복시산을 포함하는 아크릴 단량체인 methacrylic acid (MA)가 도입된 grafted EPDM을 합성하여 MA의 grafting ratio가 탄성체의 물성과 다른 고무와의 접착특성에 미치는 영향을 연구하였다. Grafted EPDM의 storage modulus는 특정온도까지는 sulfur로 가교한 EPDM vulcanizate보다 높게 유지되다가 온도가 더 높아지면 2차 결합력이 약해지면서 급격하게 감소되는 것이 관찰되었다. EPDM에 수소결합을 유도할 수 있는 반응기를 도입했을 때 grafted EPDM 분자들 간의 aggregate 형성과 그라프트된 MA의 결정성으로 인해 우수한 기계적 물성을 나타내었다. EPDM 자체는 극성이 낮고 다른 종류의 고무와 분자간 결합력이 약해서 접착이 제대로 이루어지지 않았으며 그라프트된 MA의 함량이 증가할수록 접착강도가 더 높아졌으며 MA의 grafting ratio가 10% 이상일 때에는 접착평가 시 고무시편이 부분적으로 파괴될 정도로 접착력이 우수하였다. The effect of the grafting ratio on the mechanical property and adhesion property of the grafted EPDM modified with methacrylic acid (MA) was investigated. The storage modulus of MA-grafted EPDM was maintained higher than that of cross-linked EPDM vulcanizate by sulfur, but it was observed that the storage modulus was decreased at elevated temperature because of the weakened secondary bonding. When the functional group for hydrogen bonding was introduced in EPDM, it had excellent mechanical properties by the aggregate between grafted EPDM molecules and crystallinity of MA. The bonding strength between EPDM and other rubbers was very low because EPDM has nonpolar property and low molecular interaction to others. The bonding strength was increased as increasing grafting ratio and it was excellent enough to break the rubber during the peel test when the grafting ratio was more than 10%.

The influence of hybrid phosphate–alumina pigments on properties of Ethylene-propylene-diene rubber composites

In this work Ethylene-propylene-diene (EPDM) rubber vulcanizates were pigmented with a new hybrid pigment containing nano-phosphate layer deposited on surface of micronized alumina. This new pigment contains both single and double-ion phosphates. Different rheological, chemical and physical properties of the nano-pigmented EPDM vulcanizates were studied and compared to the non-pigmented EPDM composites. These pigmented composite properties were studied in the presence and absence of maleic anhydride (MAH) which was employed as a compatibilizer. The bound rubber and cross-linking density were calculated. The results revealed that composites pigmented with 3Zn·1Ca phosphate/alumina/EPDM and 1Zn·3Ca phosphate/alumina/EPDM exhibited the best properties compared to other pigmented composites.

AC conductivity and positive temperature coefficient effect in microcellular EPDM vulcanizates

AbstractDielectric relaxation spectra of conductive carbon black reinforced microcellular EPDM vulcanizates were used to study their relaxation behavior in the frequency range of 0.01–105 Hz over a wide range of temperature from 30 to 120°C. The effect of variation in filler loading and blowing agent loading (density) on dielectric characteristics such as impedance, dielectric constant, and conductivity has been studied. The experimental results show that the relative dielectric permittivity of the composites depends strongly on the extent of carbon black and blowing agent concentrations. The frequency dependence of AC conductivity has been investigated by using Percolation theory. The permittivity and conductivity of the microcellular composites have been analyzed based on scaling theory at increasing temperatures. The applicability of Lichtenecker‐Rother's “rule of mixture” to describe the complex permittivity of the composite has also been investigated. Irrespective of the blowing agent loading and temperature, the percolation threshold as studied by DC conductivity was found to be at 40 phr loading of the filler. Scanning electron microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Impedance analysis and electromagnetic interference shielding effectiveness of conductive carbon black reinforced microcellular EPDM rubber vulcanizates

AbstractThe effect of processing variables (filler and blowing agent loadings) and operating variables (frequency and sample thickness) on the impedance and electromagnetic interference (EMI) shielding effectiveness of excess conductive carbon black reinforced solid and microcellular EPDM vulcanizates has been investigated. Increasing frequency showed a decrease in real part of complex impedance for both filler and blowing agent loadings, whereas the imaginary part showed a slight peak in the range of 9–10 GHz followed by a subsequent decrease. The measured impedance values were plotted as Nyquist plots (Argand diagrams) and a Resistor–Capacitance model was assumed. Increasing blowing agent loadings showed a marginal increase in the bulk resistivity, whereas increasing filler loadings had a significant decrease. The EMI shielding effectiveness increased monotonically with filler loading and showed a maximum of around 75 dB at 60 phr loadings, thus making them suitable for shielding applications. Increasing blowing agent loadings showed an increase in shielding effectiveness at low loadings (2 phr) whereas further increase showed a rapid decrease. This has been explained on the basis of formation of voids in the composite, which affect the absorbance capacity of the microcellular vulcanizates. However, the microcellular composites showed sufficiently high values in the range of 50–60 Db, thus making Vulcan XC 72 reinforced microcellular EPDM vulcanizates as ideal packaging material for EMI shielding applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Modification In Situ of EPDM Filled with Carbon Black by Glycidyl Methacrylate

A method of chemical modification in situ of ethylene-propylene-diene rubber (EPDM) filled with carbon black was studied. A bifunctional monomer, glycidyl methacrylate (GMA), was used as the modifier to improve the dispersibility of carbon black in the rubber and to enhance the mechanical properties of EPDM vulcanizates. The effects of GMA on the structure and properties of EPDM vulcanizates such as determination of cross-linking density and vulcanizing properties as well as mechanical properties were investigated by FT-IR, SEM, and DMTA. The results showed the addition of GMA into carbon black filled EPDM compounds could remarkably improve the mechanical properties of the vulcanizates. The optimum content of GMA was about 5.0 phr when the content of carbon black was 50 phr. The reason for improvement of the mechanical properties might be attributed to the chemical combinations between rubber macromolecular chains and carbon black surfaces by GMA. The action of GMA was similar to a cocuring agent and a coupling agent.

Dielectric relaxation of Ensaco®350G reinforced microcellular EPDM vulcanizates

AbstractThe dielectric relaxation characteristics of microcellular EPDM vulcanizates has been studied as a function of variation in filler and blowing agent loadings in the frequency range of 100–106 Hz. The dielectric constant ε′ increases with increasing filler loadings at all frequencies. This has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium. The effect of variation in filler and blowing agent loadings on the complex and real parts of impedance was distinctly visible. Which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. The phenomenon of percolation in the composites has been discussed based on the measured changes in electric conductivity and morphology of composites at different concentrations of the filler. The percolation threshold as studied by DC conductivity occurred near 40 phr of filler loading. SEM microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. POLYM. COMPOS., 28: 657–666, 2007. © 2007 Society of Plastics Engineers

Relaxation behavior of conductive carbon black reinforced EPDM microcellular vulcanizates

AbstractDynamic mechanical analysis and dielectric relaxation spectra of conductive carbon black reinforced microcellular EPDM vulcanizates were used to study the relaxation behavior as a function of temperature (−90 to +100°C) and frequency (0.01–105 Hz). The effect of filler and blowing agent loadings on dynamic mechanical and dielectric relaxation characteristics has been investigated. The effect of filler and blowing agent loadings on glass transition temperature was marginal for all the composites (Tg value was in the range of −39 to −35°C), which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. Strain‐dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.07–5%. The nonlinearity in storage modulus has been explained based on the concept of filler–polymer interaction and interaggregate attraction (filler networking) of carbon black. The variation in real and complex part of impedance with frequency has been studied as a function of filler and blowing agent loading. Additionally, the effect of crosslinking on the dielectric relaxation has also been reported. POLYM. ENG. SCI., 47:984–995, 2007. © 2007 Society of Plastics Engineers