Ethylene Propylene Diene Terpolymer Rubber Research Articles

Ageing tests closer to real service conditions using hyper-sensitive microcalorimetry, a case study on EPDM rubber

Accelerated thermal ageing (ATA) coupled to mechanical testing is widely used to predict the lifetime of polymeric products. ATA implies that the mechanisms of ageing are the same at accelerated and service conditions, which may often not be the case. Hence, ageing closer to service conditions is of high importance, but require very sensitive tools. Therefore, a high sensitivity microcalorimetry (MC) method was applied here to assess if it can be a possible tool for lifetime/ageing prediction closer to service conditions. We chose to focus on a complex, yet commonly used, ethylene-propylene-diene terpolymer (EPDM) rubber. Arrhenius extrapolation of the heat flow data indicated two regimes at low and high temperature, with the former having the lower activation energy. The heat flow values measured by the MC revealed contributions from processes such as the melting of the antioxidant, its consumption at low temperature and the breakdown of residual peroxide. MC tests on the EPDM indicated a very low degree of oxidation appearing above 100 °C, too low to be observed with infra-red spectroscopy (FTIR), but noticeable with MC. The high sensitivity of the MC techniques enabled detection of early signs of polymer degradation/ageing and other thermally activated processes that take place at or close to service temperatures (such as those in nuclear power plants). The MC tests were combined with other techniques, such as scanning electron microscopy/energy dispersive X-ray spectroscopy, gas chromatography techniques, differential scanning calorimetry and FTIR to further understand the degradation mechanisms.

Influence of permanent deformation on the fitting quality and the simulation prediction of filled elastomers

This work deals with the consequence of fitting hyperelastic material models to quasi-static multi-hysteresis test data with and without the correction of permanent deformation. Multi-hysteresis experiments are performed in different deformation states with equivalent amplitudes and equivalent strain rates. The investigations are performed on a carbon black filled ethylene propylene diene terpolymer rubber (EPDM). A second order polynomial hyperelastic material model was used to investigate the effect of elimination of permanent deformation during the fitting process. We find that the elimination of permanent deformation leads to a prediction of a stiffer material behavior. The validation of the obtained fitting parameters in the double-sided shear and uniaxial tension–compression loadings clearly shows that the elimination of the permanent deformation has a huge influence on the predicted stress field and strain field.

Crack growth angle prediction of an internal crack under mixed mode load for unfilled elastomer using the strain energy density factor

ABSTRACTThis article investigates the prediction of the crack growth angle of an existing internal crack under mixed mode loading at the crack tip for an unfilled ethylene propylene diene terpolymer rubber (EPDM). For the realization of mixed mode loading, the cracks of the uniaxial loaded specimens were oriented with different angles to the loading direction. The energy density factor was used as a potential criterion for determining the crack growth angle. The determination of the strain energy density factor was carried out simulatively in Abaqus. The second‐order Ogden model was used to describe the rubber‐like material behavior. The relative local minimum of the strain energy density factor provides the possible growth angle. The experimental investigations show that the initial cracks grow orthogonally to the loading direction for the different crack orientation angles. For the crack orientation angle parallel to the load direction, the crack growth was observed because the strong stretching of the specimen caused strong necking in the crack region. The crack growth for the remaining crack orientation angles were induced due to shear loading at the crack tip. The predictive angle of different crack orientation angles shows very good accordance to the measured crack growth angles.

A nitrile functionalized graphene filled ethylene propylene diene terpolymer rubber composites with improved heat resistance

Abstract Ethylene propylene diene terpolymer rubber (EPDM) is susceptible to temperature, and heat can greatly increase the molecular mobility which degrades the mechanical properties of a rubber part. To overcome this problem, EPDM composites containing various nitrile functionalized graphene (GN-CN) were prepared and investigated for the effects of surface modification on the mechanical properties under low and high temperature. Results indicated that, the tensile strength of 3phr GN-CN filled EPDM composite reaches 11.8 and 6.0 MPa at 25 °C and 70 °C, respectively, which is 63.9% and 100% higher than that of unfilled one. Meanwhile, the strength loss of the EPDM/GN-CN composite under 70 °C is 49.1%, which is 9.2% lower than that of EPDM. It was demonstrated that, the reaction of the nitrile groups is benefit to the tensile strength and heat resistance improving of EPDM.

Effect of gamma radiation on the physicomechanical characters of EPDM rubber/modified additives nanocomposites

Ethylene propylene diene terpolymer (EPDM) rubber nanocomposites have been prepared by incorporating 10 phr of organically modified montmorillonite (OMMT) nanoclay and various percentages of fumed silica (10, 20, and 30 phr) onto EPDM rubber composite using two roll mill and crosslinked by gamma radiation. The effect of radiation dose on the mechanical properties namely tensile strength and elongation at break and the physical properties namely solubility and swelling were investigated. Thermogravimetric analysis was carried out to analyses the thermal stability of the nanocomposites. Volume resistivity of the nanocomposites was also measured. The results showed that the mechanical, volume resistivity, and thermal properties of the irradiated EPDM rubber containing OMMT were increased by adding of the fumed silica. The effect of N,N‐m‐phenylenedimaleimide coagent on the mentioned properties of the EPDM rubber nanocomposites was studied. The results showed that the physical, mechanical, and thermal properties of the irradiated EPDM rubber nanocomposites improved with the addition of the coagent due to the increase of the crosslinking density. The inclusion of both the 30 phr fumed silica and the coagent in the nanocomposite irradiated to 50 kGy leads to a synergistic effect. J. VINYL ADDIT. TECHNOL., 23:E188–E200, 2017. © 2016 Society of Plastics Engineers

Synergistic effect of graphene nanoplatelets and carbon black in multifunctional EPDM nanocomposites

Ethylene–propylene–diene terpolymer rubber (EPDM)-based nanocomposites containing carbon black (CB), graphene nanoplatelets (GNPs), and mixtures of the two fillers were prepared. The influence of the relative amounts of the two fillers on the dynamic and static friction coefficients was examined. The static analysis of the coefficient of friction suggests that the partial substitution GNPs into the EPDM/CB blend did not produce a significant variation of the surface grip. The sample comprising EPDM/CB composite and an effective amount of GNPs dispersed in the matrix provides an increase of the thermal conductivity, damping (i. e. shock absorbing properties) and mechanical properties of the nanocomposites. The field-emission scanning electron microscopy and micro tomography analyses showed that the replacement of CB with GNPs reduces the CB aggregation and, hence, improving the percolation of the hybrid fillers and the interface resistance of the composite. The development of thermally conducting elastomeric nanocomposites could envisage their utilization in the processing of rubber blends satisfying the increasing demand to reduce both the duration of the vulcanization process and thus the cost of the vulcanized rubbers.

Effect of borax on the thermal and mechanical properties of ethylene‐propylene‐diene terpolymer rubber‐based heat insulator

ABSTRACTThe effect of Borax on the mechanical and ablation properties of three different ethylene‐propylene‐diene terpolymer (EPDM) compounds containing 20 phr carbon fiber, 20 phr Kevlar or 10 phr/ 10 phr carbon fiber/ Kevlar was investigated. All formulations contained 30 phr fumed silica powder and 10 phr paraffinic oil. It was found that adding Borax to the composite samples containing carbon fiber or Kevlar fiber or their mixture with an equal ratio can increase the tensile strength, elastic modulus and hardness with a slightly decrease in the elongation at break of the rubber samples. The results of thermogravimetry analysis (TGA) on the various samples showed significant increase in the char yield at 670°C by adding Borax to the rubber compounds. Moreover, ablation resistance of samples was also improved by increasing Borax content. Meanwhile, density and thermal conductivity of the insulator were also reduced up to about 10% when the carbon fiber was replaced with the Borax. The results indicated that composites containing Kevlar have high storage modulus and produce compact and stable char. EPDM rubber composite containing Borax (20 phr), carbon fiber (10 phr), and Kevlar (10 phr) showed thermal and ablative properties comparable with those of the asbestos‐ filled EPDM. The thermal conductivity and ablation rate of the above‐ mentioned sample were 0.287 W/m/K and 0.13 mm/s respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 41936.

Correlation of crosslink densities using solid state NMR and conventional techniques in peroxide-crosslinked EPDM rubber

Peroxide-crosslinked ethylene propylene diene terpolymer (EPDM) elastomer samples were prepared with various types and concentrations of peroxide, with and without co-agent. The variation of crosslink density, the spatial distribution of the crosslinks in the network and the presence of network defects in EPDM rubber were investigated on a molecular level using proton low-field solid-state double-quantum (DQ) NMR spectroscopy. The results reveal that types and concentrations of peroxides do not affect the overall rather inhomogeneous spatial distribution of the crosslinks, but do affect significantly the average crosslink density. The introduction of a co-agent leads to higher crosslink densities and increased levels of spatial crosslinking inhomogeneity as well as non-elastic defects. Apparent crosslink densities as measured by DQ NMR, solvent swelling, linear and non-linear stress-strain measurements (Mooney–Rivlin analysis), and the curemeter, are correlated and discussed. While most of the results can be interpreted consistently and in agreement with the usual assumptions concerning the effect of (trapped) entanglements, a previously unnoticed, decisively non-linear correlation of the NMR results with the linear-regime modulus indicates a large influence of the substantial crosslinking inhomogeneities on the mechanical behaviour. Also, the data suggest a rather efficient trapping of entanglements, possibly because of reduced chain slippage due to the bulky norbornene comonomers.

DEVELOPMENT OF AN ECO-EFFICIENT PRODUCT/PROCESS FOR THE VULCANISING INDUSTRY

This paper presents the development of an eco-efficient product/process, which has improved mechanical properties from the introduction of natural fibres in the EPDM (Ethylene-Propylene-Diene-Terpolymer) rubber formulation. The optimisation analysis is made by a fractional factorial design 2 11-7 . Different formulations were evaluated using a multi-response desirability function, with the aim of finding efficient levels for the manufacturing time-cycle, improving the mechanical properties of the product, and reducing the raw material costs. The development of an eco-efficient product/process generates a sustainable alternative to conventional manufacturing.

EPDM/silicone blend layered silicate nanocomposite by solution intercalation method: Morphology and properties

Ethylene–propylene–diene terpolymer (EPDM)/silicone blend nanocomposites are prepared by solution method for the first time. EPDM and silicone rubber in their 50:50 (by weight) blend is intercalated within the silicate sheets of organically modified montmorillonite. Organic modification to the pristine sodium montmorillonite (Na‐MMT) surfaces is carried out by ion‐exchange reaction using hexadecyl ammonium chloride. The incorporation of such organic functional group makes Na‐MMT hydrophobic and expands the interlayer spacing between silicate sheets. The intercalated structure of EPDM/silicone blend nanocomposites is characterized by the X‐ray diffraction. Transmission electron microscopic characterization visualized the presence of both exfoliated and intercalated layered silicate in the polymer nanocomposites. The mechanical properties of the nanocomposites show a maximum improvement in tensile strength and elongation at break of 23 and 68%, respectively, compared with EPDM/silicone blend. The dielectric measurement demonstrates the increase in relative permittivity for the nanocomposite than the pure blend. The increase in the onset temperature of the thermal degradation of nanocomposites (∼52°C) corresponding to 1 wt% decomposition indicates the enhancement of thermal stability of (EPDM)/silicone blend due to interaction with silicates. POLYM. COMPOS., 35:1834–1841, 2014. © 2014 Society of Plastics Engineers

A new approach to rubber reinforcement

In this paper, we report the highly efficient reinforcement of dynamically cross-linked silane-modified phenol formaldehyde resin (SMPF) in ethylene-propylene diene terpolymer rubber (EPDM). Only 5 phr of SMPF is able to greatly improve the tensile strength of EPDM from 5 MPa to 28 MPa, which is 55% higher than that of EPDM filled with 30 phr of carbon black N330, and it still retains a high elongation of more than 600%. The scanning electron microscopy and X-ray diffraction results reveal the reinforcement mechanism of EPDM. SMPF is uniformly dispersed in the EPDM matrix by a conventional Banbury mixer and is dynamically cross-linked to form a greatly expanded hard phase comprising the interpenetrating polymer networks of EPDM and SMPF during the mixing process, which leads to a high modulus. The high tensile strength is attributed to the strain-induced crystallization of EPDM at high strain according to the X-ray diffraction patterns of the stretched EPDM–SMPF composites. These results reveal the high efficient reinforcement of the thermoset resin in rubber, demonstrate a new mechanism of rubber reinforcement and suggest a new direction for rubber reinforcement.

Pyroshock testing on graphene based EPDM nanocomposites

Ethylene–propylene–diene terpolymer rubber (EPDM) and graphene nanoplatelets (GNPs) nanocomposites were prepared via a vulcanization process. The mechanical and thermal properties of the nanocomposites were studied. Curing studies demonstrated the increase in maximum torque for the GNP loaded EPDM compounds compared to carbon black loaded EPDM. A high magnitude and a high frequency transient loading, a pyroshock event, was applied to the prepared samples. The acceleration time history measured in the impact excitation test and a simplified analysis model based on the frequency response analysis, were established for evaluating the shock response of the nanocomposites. Experimental results indicated that the interfacial interaction between GNPs and EPDM matrix results in enhancements in damping property. This experimental approach can be used to test the potential utilization of such polymer nanocomposites to be used for space or military components subjected to high-frequency, high-magnitude shock pulses.

Structural characteristics of some high density polyethylene/EPDM blends

Blends of ethylene propylene diene terpolymer rubber (EPDM) with high density polyethylene were obtained by melt mixing. Mechanical properties of the composites, tensile strength, hardness, resilience, elongation at break, 100% modulus and tear strength were determined. Differential scanning calorimetry and wide angle x-ray diffraction were employed to study melting behavior and crystalline structure. The surface properties were analyzed using contact angle determinations. Also, compatibilization with PE-g-MA or dynamical vulcanization using phenolic resins was applied to obtain improved mechanical properties. It was found that the crystalline structure of HDPE was not changed during blending. The vulcanized composite presents a lower degree of crystallinity. Elongation at break and hardness were significantly increased for composites containing compatibilizing agent. The morphology of EPDM composites was studied by atomic force microscopy.

Mechanical Properties and Tensile Deformation Behavior of Polyamide 6/Maleated and Unmaleated Ethylene Propylene Diene Terpolymer/Nano-CaCO3 Ternary Composites

Ternary composites composed of polyamide 6 (PA6), a mixture of maleated (EPDM-g-MA) with unmaleated ethylene propylene diene terpolymer (EPDM) rubber at weight ratio 80/20 (defined as EPDM-M), and nano-calcium carbonate (nano-CaCO3) were prepared by a two-step compounding route. Sandbag microstructure, in which nano-CaCO3 agglomerates were embedded EPDM-M, were observed by scanning electron microscopy (SEM). Deformation of the composites was studied by video-aided tensile tests during uniaxial tension. The microstructural morphology and interfacial interaction were investigated through SEM and dynamic mechanical analysis (DMA). Compared to PA6/EPDM-M/nano-CaCO3 ternary composites without sandbag microstructure (E2), the microstructural morphology of PA6/EPDM-M/nano-CaCO3 ternary composites with sandbag microstructure (E3) showed that numerous microfibrils and cavitations were formed by simultaneously stretching and debonding of nano-CaCO3 agglomerates and EPDM-M in the sandbag microstructure, which resulted in a higher volume strain and larger quantity of energy dissipation. Additionally, better interfacial interaction between the sandbag microstructure and PA6 matrix in E3 caused a lower α-relaxation temperature and easier external energy transmission than E2 without sandbag microstructure. Consequently, the presence of the sandbag particles in PA6/EPDM-M/nano-CaCO3 ternary composites changed the tensile yield deformation of PA6 from a more deviatoric plasticity to a more dilatational plasticity.

Effect of aluminium hydroxide, chlorinated polyethylene, decabromo biphenyl oxide and expanded graphite on thermal, mechanical and sorption properties of oil-extended ethylene–propylene–diene terpolymer rubber

Oil-extended EPDM composites with different flame retardant fillers like aluminium hydroxide (ATH), chlorinated polyethylene (CPE), decabromobiphenyl oxide (DBBO) and expanded graphite (EG) were prepared by conventional mill mixing. Thermal, mechanical and sorption characteristics of the vulcanizates were studied. The effect of different fillers on the flammability of the composites was measured using Limiting Oxygen Index (LOI) and UL-94 HB tests. Scanning Electron Microscopic (SEM) studies of the composites were also conducted. ATH and CPE improve the thermal stability of the composite substantially. Among the four fillers ATH has the highest reinforcing effect on the EPDM rubber. Sorption studies of the composite showed that ATH reduced the swelling rate of the microcomposite considerably. All the four fillers were effective in improving the flame retardant property. Filler dispersion studies and SEM images point to a uniform dispersion of filler in the matrix which is in good agreement with significant improvement in mechanical properties.

Permeation of Chlorinated Hydrocarbon Vapors through High Density Polyethylene/Ethylene Propylene Diene Terpolymer Rubber Blends

Polymer membranes were prepared by blending high density polyethylene (HDPE) with ethylene propylene diene terpolymer rubber (EPDM) and were tested for vapor permeation characteristics. The variation in sorption, diffusion, and permeation coefficients with blend composition has been studied and it was found that in these blends the permeability coefficient and sorption coefficients increased with increase in EPDM concentration. The permeation rate decreased with the increase in molecular mass of the penetrants. The permeability of the HDPE/EPDM blends vulcanized with three different vulcanizing systems has been studied and found that as the degree of crosslinking increases, the permeability decreases. The permeability measurements provide useful information on the morphology changes with composition of the blends and on the composition corresponding to the maximum level of co-continuity of the two phases.

Electron-induced reactive processing of thermoplastic vulcanizate based on polypropylene and ethylene propylene diene terpolymer rubber

Thermoplastic vulcanizate (TPV) was prepared by in situ cross-linking of the rubber phase by high-energy electrons during melt mixing with a thermoplastic. The electron accelerator was directly coupled with the mixing device to cross-link the rubber phase in situ. The effect of the electron energy and absorbed dose per rotation on the properties and morphology of the TPV was studied. An absorbed dose of 100 kGy and a dose per rotation of 90 kGy per rotation resulted in a TPV with the best set of mechanical properties, as confirmed by morphological analysis too. The effect of different blend ratios was also studied, and it was found that a 50:50 blend ratio produced TPV with superior mechanical properties compared with 30:70 blends, as confirmed by the morphological analysis. A mechanism for the observed improvement in mechanical properties was proposed, based on the viscosity ratio of the blend components and the blend ratio. Finally, the effect of the premixing time of the blend components on the mechanical properties and morphology before the electron-induced reactive processing (EIReP) was studied. A premixing time of 14 min was required to achieve the optimum dispersion of the rubber phase in the thermoplastic phase before in situ cross-linking. EIReP of ethylene propylene diene monomer (EPDM)/polypropylene (PP) blends presents a novel approach where the EPDM phase is cross-linked and grafted to PP by high-energy electrons without any coagent during melt mixing with PP. In the present work, the effect of absorbed dose, absorbed dose per rotation, and of different blend ratios on the properties and morphology of PP-EPDM TPVs is discussed in detail. The effect of premixing time is also discussed to observe its influence on the morphology and final properties of the TPVs prepared.

Transport behavior of aromatic hydrocarbons through high density polyethylene/ ethylene propylene diene terpolymer blends

Membrane based separation technology is currently regarded as a new frontier of chemical engineering and widely used for the purification, concentration and fractionation of fluid mixtures. Polymer blend membranes are promising materials that can overcome the difficulties associated with homopolymer systems and hence the selection of polymer blend membrane as a novel material for various applications is worth probing. Transport properties of aromatic hydrocarbons through a new class of membranes from blends of high density polyethylene (HDPE) and ethylene propylene diene terpolymer rubber (EPDM) have been investigated at different temperatures to understand the effect of physical and chemical nature of the polymer blend on the transport phenomena. The effects of blend ratio, temperature and penetrant size on the sorption properties were studied. The equilibrium solvent uptake decreases with an increase in concentration of HDPE, in the blends. Relationship between transport behavior and the morphology of the system was examined. The mechanism of transport has been analyzed and found that the mode of transport is close to Fickian. The sorption data have been used to estimate the transport coefficients and various kinetic parameters of sorption.

Roofing Assembly Simulated Heat and Light Test

Abstract The goal of this project is to search for a testing procedure for roof covering products that will radiate both heat and light onto a roof covering and then measure the impact that a given roof covering product has on heat transfer through the entire roofing assembly. Identical roof assemblies were built with ethylene propylene diene terpolymer (EPDM) rubber roof membrane over a wood deck. Sixteen heat lamps were positioned 1.14 m [45 in.] above the roof covering product to provide both heat and light. Thermocouples were placed on the underside of the wood deck and were insulated from outside air. The roofing assembly and the roof covering temperatures were brought to 18°C to 21°C prior to testing. Heat and light were radiated onto the roof coverings for 360 min and the under deck temperature was recorded at 1 min intervals for 600 min. Tested roof coverings included gravel, growing media, coatings, and panels in the form of concrete, ceramic foam, and rubber. The results of the tests have shown data similar to that which were recorded during warm, sunny days. As expected, the highest temperatures were achieved by the uncovered and uncoated black EPDM roof assembly. The temperature of this assembly diminished almost immediately upon the removal of the heat and light source. Thicker layers of growing media and ceramic foam block did not reach the peak temperature until several hours after the heat lamps were turned off. The roof assembly covered with reflective coating showed realistic resistance to the heat and light source. This is a significant advancement in the effort to provide equitable data for all roof coverings. The test provides a standard method of collecting data for traditional roof coverings as well as emerging technology roof covering materials to evaluate a roofing assemblies’ thermal performance from solar heat gain.

Transport properties of high-density polyethylene/ethylene propylene diene terpolymer blends

Polymer blends based on high-density polyethylene and ethylene propylene diene terpolymer rubber (EPDM) were prepared. The sorption and diffusion of four aliphatic hydrocarbons through the blends were studied in the temperature range of 28–58 °C. Sulfur, dicumyl peroxide (DCP), and a mixture of sulfur and DCP (mixed) were used as cross-linking agents for the blends. Of the three systems, the peroxide vulcanized blends were found to exhibit the lowest penetrant uptake. This has been explained based on the higher rigidity of the –C–C– networks than the polysulfide linkages. The aliphatic liquid penetration through the matrix increased with increase in the EPDM content in the blend. The experimental observations were correlated with the morphology of the blends. Diffusion and permeation coefficients were calculated from the sorption data. A slight deviation from the Fickian trend was observed for the mechanism of transport with an increase in EPDM in the blends. The molar mass between cross-links and thermodynamic parameters of sorption was determined from the swelling data. The experimental observations were compared with various theoretical models.