Ethylene Propylene Diene Terpolymer Research Articles

A Polyolefin Elastomer Encapsulant Modified by an Ethylene-Propylene-Diene Terpolymer for Photovoltaic Applications.

In this study, a newly designed adhesion promoter, a modified ethylene-propylene-diene terpolymer (m-EPDM), was constructed via a simple thiol-ene click reaction between the ethylene-propylene-diene terpolymer (EPDM) and 3-mercaptopropyltrimethoxysilane (MPTS) to employ polyolefin elastomer (POE) encapsulants in photovoltaic modules. The grafting reaction of MPTS on an EPDM backbone (thiol-ene click reaction) was verified using 1H NMR, 29Si NMR, and SEM/EDX. The thermal and mechanical characteristics of the POE compounds did not significantly change with an increasing m-EPDM content irrespective of the cross-linking state. Interestingly, the adhesion strength to the glass substrate increased linearly with an increasing m-EPDM content until 9 phr. Also, the POE compounds containing more than 12 phr m-EPDM showed cohesion failure of the encapsulant layer, remaining as a residue of the encapsulant layer on the glass surface after peel testing. The damp-heat test was conducted to evaluate the long-term durability of the photovoltaic module encapsulated with m-EPDM, and no significant power loss was found even after 1000 h under the test conditions.

Effect of silica filler on peroxide cured ethylene propylene diene terpolymer insulation for large rocket motors

AbstractNon‐compatibility with double base propellant and nitrate ester plasticized polyether based propellant and poor aging resistance limit the overall life of sulfur cured EPDM insulation and warranted the development of peroxide cured EPDM insulation in order to reap the full benefits of EPDM insulation. This article describes the effect of silica filler on the physical, mechanical, thermal, and ablative properties of peroxide cured EPDM insulation, free from chlorosulphonated polyethylene and filled with conventional precipitated silica, which has been validated for the requirements of large composite rocket motor casing. Significant findings, which have been corroborated by instrumental techniques viz. DSC, TGA, FTIR, and SEM are presented in this article.

The effect of cross-linking system and reinforcement on the cross-linking reaction of peroxide vulcanized ethylene-propylene-diene terpolymer (EPDM) matrix

In this work, the effect of using of dicumyl-peroxide (DCP) (2, 5 & 8 phr) and co-agent triallyl-cyanurate (TAC) (2, 4 & 6 phr) as cross-linking system as well as multi-walled carbon nanotubes (MWCNTs) (5, 8 και 10 phr) as a filler, for ethylene-propylene-diene terpolymer (EPDM) was investigated. Differential scanning calorimetry (DSC) was employed in order to study the progress of the cross-linking reaction, based on the exothermic vulcanization peaks of isothermal (at 160, 170, 180, 190 °C) and non-isothermal experiments (with heating rates 5, 10, 25, 50 °C min−1). The autocatalytic model was successfully applied to the results of isothermal experiments and the activation energy (Ea) of the reaction was calculated, based on the Arrhenius equation. The Ozawa-Kissinger equations were also applied to the data obtained from the non-isothermal study. From the results obtained from isothermal DSC experiments, an increase was observed in the reaction rates accompanied with a decrease in Ea with the increase of DCP content, whereas a proportional relationship between TAC content and the enthalpy and Ea of the reaction was recorded. The incorporation of MWCNT’s in EPDM increased its Ea. From the non-isothermal DSC experiments, a significant increase in the enthalpy and Ea of the cross-linking reaction was observed at higher DCP content, whereas TAC content did not show any notable effect on the reaction. Based on the results of this research, it is concluded that the increase of peroxide content facilitates the vulcanization of EPDM, whereas inhibition was observed by the incorporation of MWCNT’s.

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.

Critical conditions for liquid chromatography of statistical polyolefins: Evaluation of diene distribution in EPDM terpolymers

Liquid chromatography at critical conditions is of interest as it may unravel molecular information on macromolecular structures not accessible by any other analytical techniques. Yet so far, such conditions have never been experimentally established for copolymers, where a particular need for such information exists. Toward this goal, critical conditions for statistical ethylene propylene copolymers were identified. In the first approach the composition of the binary mobile phase was varied at a constant temperature, and secondly by modulating the adsorption-desorption temperature at constant mobile phase composition. Solvents for both methods were identified by using a novel approach that combines structure retention relationships with Hansen Solubility Parameters. As a result, for the first time, the heterogeneity of an ethylene propylene diene terpolymer sample with regard to the pendant double bond of the diene could be determined. The novel chromatographic approach was validated by measuring the composition of fractions taken over the chromatographic run offline by nuclear magnetic resonance. In summary, this work gave the first experimental evidence for the existence of critical conditions for polyolefin random copolymers, as postulated by Brun. This novel chromatographic approach holds immense potential to engineer complex polymers towards future applications by making use of the now-accessible molecular information.

Optimization of silane modification and moisture curing for EPDM toward improved physicomechanical properties

The silane modification by melt mixing and the subsequent moisture curing of ethylene propylene diene terpolymer (EPDM) was optimized based on the Design of Experiments (DOE). The optimum moisture-cured Si-EPDM samples displayed a 101.7% and 36.5% improvement in the tensile strength and modulus, respectively, compared to the pristine EPDM. The cured Si-EPDM even had higher tensile strength than the conventionally sulphur-vulcanized EPDM. Overall, the mechanical properties of the cured Si-EPDM mainly depended on the crosslinking density. However, when there was too much crosslinking, the uneven distribution, byproduct-induced defects and restrictions to the chain re-orientations would negatively affect the tensile strength. The optimum moisture-cured Si-EPDM also displayed higher thermomechanical properties than the pristine EPDM.

Preparation and anti‐migration performance of ethylene propylene diene terpolymer composites modified with GO‐SiO2 hybrid nanomaterials

AbstractThe anti‐migration ethylene propylene diene terpolymer (EPDM) inhibitor coating was prepared by using EPDM as a composite matrix and silicon‐functionalized graphene oxide (GO‐SiO2) as modifiers to prevent the migration of energetic plasticizers in propellants. The anti‐migration performance at different temperatures was analyzed by investigating the diffusion of dioctyl sebacate (DOS) using thermal analysis and immersion tests. After adding 1.0 wt% GO‐SiO2, the overall performance of the inhibitor coating was the best, and the concentration of DOS that migrated into the inhibitor coating at 30°C was reduced from 45.1% to 38.8% (13.9% decrease). The results confirmed that the introduction of GO‐SiO2 prevented the migration of dioctyl sebacate to the EPDM inhibitor coating. The scanning electron microscopy results showed that GO‐SiO2 was well‐dispersed in the inhibitor coating, and the tensile strength increased from 1.80 to 2.11 MPa. Migration kinetics analysis showed that the anti‐migration performance was closely related to the crosslink density.

Elucidation of the role of ZnO in sulfur cure in novel EPDM-CTS blends

A new concept is introduced in this study, suggesting the role played by the ZnO crystal in sulfur crosslinking polymers, particularly, rubber blends of EPDM-CTS. The study is conducted in a polymer blend of ethylene propylene diene terpolymer (EPDM) and cyclic tetrasulfide (CTS). CTS is a reactive low molecular weight polymer, which can act as a sulfur donor. It is proposed that the sulfur crosslinking occurs at the surface of the ZnO crystals. A reaction site is created on the surface of the ZnO crystal by the reaction with stearic acid, which creates a “template” or active site on the surface as a catalytic site for the CTS reaction to take place. Various experiments are performed to substantiate the newly proposed role the crystalline ZnO structure plays in influencing the initiation of the sulfur crosslinking. The investigation is conducted in rubber compounds in the absence of fillers and other additives and additionally in chemical model studies. The analyses conducted in rubber compounds are performed on fully or partially cured rubber to study the evolution of the chemical process involved in the CTS reaction and the curing of the rubber blends. Step-cured compound allows analyses of the transformation of the ZnO crystal size during the sulfur crosslinking process, and the ability to gauge the step transformation that the ZnO crystal is undergoing during the crosslinking process. Additional chemical model studies are used in the study of the influence of the ZnO crystal on sulfur crosslinking, to confirm the reaction path and by-products of reaction. Lastly, quantum mechanical (QM) and molecular mechanics (MM) calculations are applied in support of the suggested mechanism of reaction.

Mechanical Properties and Equilibrium Swelling Characteristics of Some Polymer Composites Based on Ethylene Propylene Diene Terpolymer (EPDM) Reinforced with Hemp Fibers.

EPDM/hemp fiber composites with fiber loading of 0–20 phr were prepared by the blending technique on a laboratory electrically heated roller mill. Test specimens were obtained by vulcanization using a laboratory hydraulic press. The elastomer crosslinking and the chemical modification of the hemp fiber surface were achieved by a radical reaction mechanism initiated by di(tert-butylperoxyisopropyl)benzene. The influence of the fiber loading on the mechanical properties, gel fraction, swelling ratio and crosslink degree was investigated. The gel fraction, crosslink density and rubber–hemp fiber interaction were evaluated based on equilibrium solvent-swelling measurements using the Flory–Rehner relation and Kraus and Lorenz–Park equations. The morphology of the EPDM/hemp fiber composites was analyzed by scanning electron microscopy. The water absorption increases as the hemp fiber loading increases.

Electrical Conductivity of Rubber Composites with Varying Crosslink Density under Cyclic Deformation.

Studies addressing electroconductive composites based on rubber have attracted great interest for many engineering applications. To contribute to obtaining useful materials with reproducible behavior, this study focused on understanding the mechanism of conductivity changes during mechanical deformation for rubber composites based on styrene-butadiene rubber (SBR) or ethylene-propylene-diene terpolymer (EPDM) vulcanized for various times. The composites were characterized by static electrical conductivity, tensile testing, dynamic mechanical thermal analysis (DMTA), and crosslink density measurements. The tensile strength and Young’s modulus were found to increase significantly with rising vulcanization time. Higher static conductivity values of the composites were observed with the increase in vulcanization time. The most important aspect of this investigation consisted in the electrical current measurement online with recording the stress-strain curves, revealing the details of the uniaxial cyclic deformation effect on changes in the structure of conductive pathways indirectly. The electrical conductivity during five runs of repeated cyclic mechanical deformations for SBR composites increased permanently, although not linearly, whereas EPDM composites showed a slight increase or at least a nearly constant current, indicating healing of minor defects in the conductive pathways or the formation of new conductive pathways.

Effects of plastic deformation and failure on the folding behavior of non‐crosslinked ethylene propylene diene terpolymer composites

Effects of plastic deformation and failure on the folding behavior of non‐crosslinked ethylene propylene diene terpolymer composites

Polylactic acid/UV-crosslinked in-situ ethylene-propylene-diene terpolymer nanofibril composites with outstanding mechanical and foaming performance

Polylactic acid (PLA) is a promising biomass and biodegradable polymer but suffers from its brittle feature and poor foaming ability. Thus, many ductile polymers have been used to modify PLA through compounding. Although some of them can improve the toughness, the strength and rigidness of PLA are seriously scarified due to the large dosage, poor dispersion, and see-island structures. Herein, UV-crosslinking-assisted in-situ fibrillation was developed to fabricate ethylene-propylene-diene terpolymer (EPDM) nanofibril-reinforced PLA composites. Twin-screw compounding followed by melt blowing was used to stretch EPDM phase into nanofibrils, while UV-crosslinking was proposed to stabilize the EPDM nanofibrils in the final PLA/EPDM composites. Thanks to UV-crosslinking, EPDM nanofibrils with an average diameter of 94.3 nm were achieved in PLA. Due to the heterogeneous nucleating effect of UV-crosslinked EPDM nanofibrils, the crystallization rate of PLA was significantly enhanced, and refined crystal morphology with fibrous structures was obtained. Surprisingly, merely 3 wt% of UV-crosslinked EPDM nanofibrils remarkably enhanced the mechanical properties of PLA. The tensile toughness and impact strength were increased by 620% and 440%, respectively, without sacrificing strength and rigidness. Moreover, the UV-crosslinked EPDM nanofibrils also significantly improved the foaming ability of PLA. The PLA/UV-crosslinked EPDM foam with an expansion ratio of up to 28-fold was achieved for the first time by mold-opening microcellular injection molding. With the presence of UV-crosslinked EPDM nanofibrils, the expansion ratio and cell population density of the foams can be increased by 470% and 5 orders of magnitude, respectively. Owing to the super-high expansion ratio and unique micro/nanoscale structures on cell walls, the 28-fold expanded PLA/EPDM foam exhibited outstanding thermally insulating performance with a thermal conductivity of as low as 26.3 mW/m∙K.

Improved joint strength between friction-stir welded plates of Al alloy and thermoplastic vulcanizate

Nowadays, metal-polymer composites are used to reduce automobile's weight. However, welding nonpolar polymers to metals is difficult due to the lack of polar groups in molecular chains. The paper put forward an innovative strategy to solve this problem: by adding magnesium methacrylate (MDMA) changes the physical and chemical properties of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) TPV, which improves the compatibility of TPVs and metals. Moreover, the simulation experiments are carried out on plate vulcanization machine. It is found that the addition dosage and order of MDMA have a certain effect on the welding strength. Furthermore, friction stir welding (FSW) replicates the results of simulation experiments, and the ultimate tensile shear strength of P7-E3M1/aluminum alloy (AA6061-T6) reaches 24 MPa. Finally, the welding strength variation regularity with time shows that the properties of metal-TPVs become stable after 10 days. This work introduces a feasible and effective strategy that can be applied to weld various metals to polymers.

Solvent Selection for Liquid Adsorption Chromatography of Ethylene–Propylene–Diene Terpolymers by Combining Structure–Retention Relationships and Hansen Solubility Parameters

Solvent Selection for Liquid Adsorption Chromatography of Ethylene–Propylene–Diene Terpolymers by Combining Structure–Retention Relationships and Hansen Solubility Parameters

Heterogeneous network design strategy toward mechanically robust and recyclable elastomers

It is well-accepted that thermoplastic vulcanizates (TPVs) integrate the fascinating recyclability of thermoplastics and the mechanical robustness comparable to nano-filled elastomers, deriving from the particular heterogeneous network structure. However, the elasticity of TPVs is inferior to covalently cross-linked elastomers, since the irreversible deformation or even collapse of plastic phases of TPVs will certainly give rise to considerable hysteresis loss and therefore deteriorate the elasticity. Herein, we proposed a facile network design strategy toward covalently cross-linked elastomer with mechanical robustness and recyclability by engineering heterogeneous blend networks into diene-rubber system. Specifically, two conventional diene-rubbers, ethylene propylene diene terpolymer (EPDM) and styrene-butadiene rubber (SBR), were adopted as thermodynamic incompatible pair and then directly admixed. Due to the significant difference in the cross-linking reactivity between the pair, the resulting system assembled into a microphase-separated structure with strong interfacial adhesion upon in situ co-cross-linking. Upon deformation, the overall chain orientation of the networks is promoted by the efficient interfacial stress transfer and a striking reinforcement of the networks is achieved accordingly. More importantly, by virtue of the slightly cross-linking attribute of EPDM component, the resulting system featured with desirable recyclability and high elasticity in comparison with conventional TPVs. We envisage that this work will provide important inspiration for the non-filling reinforcement of elastomers and the development of a new generation of thermoplastic vulcanizates with considerably low hysteresis through manipulating the covalent network heterogeneity.

FOAMING AND MOISTURE CROSSLINKING OF VINYL TRIETHOXY SILANE GRAFTED ETHYLENE–PROPYLENE–DIENE TERPOLYMER

ABSTRACT Moisture crosslinking of polyolefins has attracted increasing attention because of its high efficiency, low cost, and easy processing. However, the crucial shortcoming of moisture crosslinking is that the side reaction of peroxide scorch (precrosslinking) simultaneously occurs in silane grafting. It has been recognized that making peroxide precrosslinking useful is an effective way to broaden the application of moisture crosslinking. A novel foaming process combined with moisture crosslinking is proposed. The matrix of ethylene–propylene–diene terpolymer grafted with silane vinyl triethoxysilane (EPDM-g-VTES) was prepared by melt grafting, with dicumyl peroxide as initiator. Foaming was then carried out with azodicarbonamide (AC) as the blowing agent by making use of precrosslinking. Subsequently, the EPDM-g-VTES foams were immersed in a water bath to achieve moisture crosslinking with dibutyl tin dilaurate as the catalyst. The results showed that VTES was grafted onto EPDM and the EPDM-g-VTES foams were successfully crosslinked by moisture. The EPDM-g-VTES compounds with AC obtained great cells by compression molding with the help of precrosslinking. The mechanical property of the EPDM-g-VTES foam was improved by moisture crosslinking. The moisture-cured foam with 4 wt% AC had an expansion ratio of about three times, which could bear large deformation and showed a high energy-absorption effect.

Scalable production of crosslinked rubber nanofibre networks as highly efficient toughening agent for isotactic polypropylene: Toughening mechanism of Non-traditional anisotropic rubber inclusion

Incorporation of homogenous rubber microparticles is a widely adopted toughening method for extending the range of applications of polypropylene (PP). Herein, a new toughening strategy with nano-structured rubber inclusion is devised and its efficiency is evaluated against the classical counterpart. The presented methodology integrates two well-established processes, namely vulcanization and in situ fibrillation, to allow scalable fabrication of PP nanocomposites toughened with crosslinked ethylene-propylene-diene terpolymer (EPDM) nanofibrils, which is otherwise technologically challenging. Morphological observation of the PP nanocomposites, supported by the drastic change in rheological behaviour under shear flow, substantiates the self-assembly of physical EPDM network nanostructure throughout the entire composite system above their rheological percolation threshold. The distinct morphology imparts unique characteristics that are vastly different from classical PP blends produced with the equivalent material composition. Massive improvement in macroscopic fracture behaviour is observed as the tensile fracture toughness is markedly enhanced at a comparatively low EPDM loading while the yield strength and elastic modulus are only marginally decreased. In our attempt to explain the superior toughening efficiency of crosslinked EPDM nanofibrillar network, we propose a collective toughening mechanism which is possibly triggered by several micro-scale mechanisms in play. This industrially relevant process potentially opens up a new avenue in material design for high-volume/lost-cost applications in the transportation sectors where excellent strength/toughness balance is indispensable.

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.

The effect of polyhedral oligomeric silsesquioxanes (POSSs) incorporation in ethylene-propylene-diene-terpolymer (EPDM): a thermal study

A series of ethylene-propylene-diene-terpolymer (EPDM)/polyhedral oligomeric silsesquioxane (POSS) composites at different percentage of POSS were prepared and subjected to γ-irradiation. Both irradiated and non-irradiated EPDM and composites were investigated by the means of thermal analysis to verify if the presence of POSS molecules is able to reduce the oxidation level of free radicals generated during the degradation and to evaluate the effects of the irradiation. EPDM composites at 1, 3 and 5 mass% of POSS were thus degraded in a thermogravimetric (TG) balance in dynamic heating conditions (25–700 °C), in both inert and oxidative atmosphere by flowing nitrogen and air respectively. Thermal characterization was then completed by carrying out Differential Scanning Calorimetry (DSC) analysis from sub-ambient to better highlight the melting of the polymer and polymer composites occurring just above the room temperature. FTIR spectroscopy was also performed for the prepared samples to check the presence of the molecular filler in the composites and for the TG’s residue at 700 °C, in order to evaluate its nature. DSC and TGA parameters were detected and discussed to have information about the effect of the degradation’s environment, the effect of irradiation on polymer stabilization and the effect of POSS content in the polymer matrix.

Stabilization Effects of Natural Compounds and Polyhedral Oligomeric Silsesquioxane Nanoparticles on the Accelerated Degradation of Ethylene-Propylene-Diene Monomer.

In this work the analysis on the stabilization activities of some natural antioxidants (rosemary extract, capsaicin, quercetin or oleanolic acid) is presented. A similar contribution of an inorganic structure—polyhedral oligomeric silsesquioxane (POSS) nanoparticles—is also evaluated. The stabilization effects on the oxidation protection were investigated for several formulations based on ethylene-propylene-diene-terpolymer (EPDM). The samples were examined in pristine state or after γ-irradiation, when the accelerated degradation scission of polymer macromolecules followed by the mitigation of oxidation. Three evaluation procedures: chemiluminescence, FTIR spectroscopy and thermal analysis were applied for the characterization of stability efficiency. The delaying effect of oxidative aging in EPDM matrix is illustrated by the values of activation energy, which are correlated with the type and concentration of embedded compounds. The durability of studied EPDM formulations is discussed for the assessment of material life. The improved behavior of structured hybrids useful for the optimization application regimes is essentially based on the antioxidant properties of polyphenolic components in the cases of natural antioxidants or on the penetration of free radical intermediates into the free volumes of POSS.