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Ethylene propylene diene monomer (EPDM) is a synthetic rubber widely used in industry and commerce due to its high thermal and chemical resistance. Nanotechnology has enabled the incorporation of nanomaterials into polymeric matrixes that maintain their flexibility and conformation, allowing them to achieve properties previously unattainable, such as improved tensile and chemical resistance. In this work, we summarize the influence of different nanostructures on the mechanical, thermal, and electrical properties of EPDM-based materials to keep up with current research and support future research into synthetic rubber nanocomposites.

This study investigated the synergistic effect of carbon black/multi-wall carbon nanotube (CB/MWCNT) hybrid fillers on the physical and mechanical properties of Ethylene propylene diene rubber (EPDM) composites after exposure to high-pressure hydrogen gas. The EPDM/CB/CNT hybrid composites were prepared by using the EPDM/MWCNT master batch (MB) with 10 phr CNTs to enhance the dispersion of CNTs in hybrid composites. The investigation included a detailed analysis of cure characteristics, crosslink density, Payne effect, mechanical properties, and hydrogen permeation properties. After exposure to 96.3 MPa hydrogen gas, the hydrogen uptake and the change in volume and mechanical properties of the composites were assessed. We found that as the MWCNT volume fraction in fillers increased, the crosslink density, filler–filler interaction, and modulus of hybrid composites increased. The hydrogen uptake and the solubility of the composites decreased with an increasing MWCNT volume fraction in fillers. Moreover, after exposure to hydrogen gas, the change in volume and mechanical properties exhibited a diminishing trend with a higher MWCNT volume fraction. We conclude that the hybridization of CB and CNTs formed strong filler–filler networks in hybrid composites, consequently reinforcing the EPDM composites and enhancing the barrier properties of hydrogen gas.

The effects of octaphenylsilsesquioxane (OPS), fumed silica, and silica aerogel on the thermal insulation properties of ethylene propylene diene monomer (EPDM) rubber were studied. On this basis, two kinds of fillers with good performances were selected to study the thermal insulation of an EPDM full-formula system. The results show that the addition of fumed silica or silica aerogel had a positive effect on the thermal insulation performance of EPDM rubber and its composite. A 30 wt% silica aerogel can be well dispersed in the EPDM rubber system and with a lower thermal conductivity compared with fumed silica. EPDM composite with 23.4 wt% fumed silica can produce more char residues at 1000 °C than at 500 °C in a burn-through test and formed the compact and porous char at 1000 °C, which had a lowest thermal conductivity. EPDM composite with fumed silica cannot be burned through 1000 °C burning, and comparison with silica aerogel revealed that it achieved the lowest back temperature and had a temperature of 388 °C after 800 s.

Ground tire rubber (GTR) is a product obtained by grinding worn tire treads before retreading them or via the cryogenic or ambient temperature milling of end-of-life tires (ELTs). The aim of this study is to evaluate if calcium carbonate can be substituted by GTR and, if so, to what extent. Different types of ground tire rubber are incorporated in an EPDM (ethylene–propylene–diene–rubber) model compound as partial or complete substitutes of calcium carbonate. The raw compounds and the vulcanizates are characterized to identify the limits. In general, it is apparent that increasing amounts of GTR and larger particles degrade the mechanical properties. The GTR also influences the vulcanization kinetics by reducing the scorch time up to 50% and vulcanization time up to nearly 80%. This is significant for production processes. The compounds with one-third substitution with the smaller-particle-size GTR show mostly similar or even better properties than the reference.

Ethylene propylene diene monomer (EPDM) is a synthetic rubber widely used in industry and commerce due to its high thermal and chemical resistance. Nanotechnology has enabled the incorporation of nanomaterials into polymeric matrixes that maintain their flexibility and conformation, allowing them to achieve properties previously unattainable, such as improved tensile and chemical resistance. In this work, we summarize the influence of different nanostructures on the mechanical, thermal, and electrical properties of EPDM-based materials to keep up with current research and support future research into synthetic rubber nanocomposites.

Devulcanization represents the recycling of choice for a homogenous rubber waste stream because it allows revulcanization of samples previously devulcanized, making the life of the rubber virtually endless, according to the principles of circular economy. Among the many devulcanization processes, the thermo-mechanical one is the most appealing because it is a continuous process, easy to be industrialized. In this paper a comprehensive set of analyses (FTIR, TGA, DSC, elemental analyses, Py-GC/MS, swelling tests) were carried out on a post-industrial ethylene propylene diene monomer (EPDM), thermo-mechanical devulcanized in a co-rotating twin-screw extruder with different process parameters (thermal and screw profile, rpm). Results of the swelling test according to the Flory–Rehner theory and Horikx analyses show that the higher the thermal profile and the higher the rpm, the higher is the percentage of devulcanization. The quality of the devulcanized sample in terms of sol fraction and percentage of random scissions depends on the process conditions. The screw profile concurs to the efficiency of the devulcanization: the different number of kneading elements and more in general the screw profile composition affects the percentage of devulcanization, making the results in some tests more dependent on the screw speed.

In this paper Ethylene Propylene Diene Monomer rubber (EPDM) foams were filled with different amounts of paraffin, a common phase change material (PCM) having a melting temperature at about 70 °C, to develop novel rubber foams with thermal energy storage (TES) capabilities. Samples were prepared by melt compounding and hot pressing, and the effects of three foaming methods were investigated. In particular, two series of samples were produced through conventional foaming techniques, involving physical (Micropearl® F82, MP, Lehvoss Italia s.r.l. Saronno, Italia) and chemical (Hostatron® P0168, H, Clariant GmbH, Ahrensburg, Germany) blowing agents, while the salt leaching method was adopted to produce another series of foams. Scanning electron microscopy (SEM) and density measurements showed that MP led to the formation of a closed-cell porosity, while a mixed closed-cell/open-cell morphology was detected for the H foamed samples. On the other hand, foams produced through salt leaching were mainly characterized by an open-cell porosity. The qualitative analysis of paraffin leakage revealed that at 90 °C only the foams produced through salt leaching suffered from significant PCM leakage. Consequently, the thermo-mechanical properties were investigated only in samples produced with H and MP. Differential Scanning Calorimetry (DSC) analysis revealed that EPDM/paraffin foams were endowed by good TES properties, especially at higher PCM contents (up to 145 J/g with a paraffin amount of 60 wt%). Tensile and compressive tests demonstrated the addition of the PCM increased the stiffness at 25 °C, while the opposite effect was observed above the melting temperature of paraffin. These results suggest that the EPDM foams produced with H and MP show an interesting potential for thermal management of electronic devices.

Ethylene–propylene–diene monomer (EPDM) composites were usually enhanced with ablative additives to protect solid rocket motor (SRMs) casings. However, the poor thermal insulation caused by the high thermal conductive ablative fillers can lead to rocket motor failure. Herein, the novel EPDM composites containing alternating layers of ablative EPDM (AM) and heat-insulated EPDM (HM) were prepared through layer-multiplying extrusion. Compared with conventional EPDM ablative material, the multilayer composites showed enhanced thermal insulation and mechanical properties that could be further improved by tuning the number of layers. The ablation and thermal insulation properties possessing in AM and HM layers could be combined by forced assembly during co-extrusion, and the alternating multilayer composite was capable of showing the effect of each component. In particular, compared with AM, the maximum back-face temperature with 40 alternating layers of AM/HM decreased from 96.2 °C to 75.6 °C during oxyacetylene test, while the good ablation properties were preserved in the AM component. This significant improvement was attributed to the planar orientation and densification of ablative additives, and the interruption of conductive pathways in the through-plane direction of AM/HM alternating laminate. The anisotropic EPDM composites featuring mechanical robustness, good ablative resistance and thermal insulation suggest considerable potential application in the aerospace industry.

With the increasing interest in hydrogen energy, the stability of hydrogen storage facilities and components is emphasized. In this study, we analyzed the effect of high-pressure hydrogen gas treatment in silica-filled EPDM composites with different silica contents. In detail, cure characteristics, crosslink density, mechanical properties, and hydrogen permeation properties were investigated. Results showed that material volume, remaining hydrogen content, and mechanical properties were changed after 96.3 MPa hydrogen gas exposure. With an increase in the silica content, the crosslink density and mechanical properties increased, but hydrogen permeability was decreased. After treatment, high-silica-content composites showed lower volume change than low-silica-content composites. The crack damage due to the decompression caused a decrease in mechanical properties, but high silica content can inhibit the reduction in mechanical properties. In particular, EPDM/silica composites with a silica content of above 60 phr exhibited excellent resistance to hydrogen gas, as no change in their physical and mechanical properties was observed.

The cross-linking structure of the Ethylene-propylene-diene monomer (EPDM) is made up of a number of cross-linking types, including carbon atoms from the main chain or monomer and ether crosslinks formed during degradation. Through molecular dynamic simulations, the contribution of each type of cross-linked structure to the dynamics and mechanical properties of EPDM, the study’s focus, were investigated. Cross-linking between the tertiary carbons of two main chains, cross-linking at the monomer’s unsaturated position, ether cross-linking after oxidation, and other combinations of target cross-linked carbon atoms from different positions, totaling eight types of cross-linked types, were mixed with EPDM free chains in a 1:1 ratio to form eight types of cross-linked EPDMs. These varieties of cross-linked EPDMs were then compared to an uncross-linked EPDM in terms of density, radius of gyration, free volume, mean square displacement, and uniaxial tensile stress-strain curves. It was found that the cross-linking was always proven to have a favorable influence on mechanical characteristics; however, the relaxation inhibition effect varied. The cross-linking between the diene monomer at the C9 position resulted in a more flexible molecular shape and was more than double the free volume of the uncross-linked EPDM, resulting in an improved diffusion ability. The ether cross-linking produced by the oxidation of the side chain cross-linking improved the positive contribution to stiffness and enhanced the inhibitory impact on diffusion properties, whereas the main chain cross-linking had the opposite effect. The research presented in this study leads to a better knowledge of the microscopic aspects underlying EPDM performance.

This study investigated the synergistic effect of carbon black/multi-wall carbon nanotube (CB/MWCNT) hybrid fillers on the physical and mechanical properties of Ethylene propylene diene rubber (EPDM) composites after exposure to high-pressure hydrogen gas. The EPDM/CB/CNT hybrid composites were prepared by using the EPDM/MWCNT master batch (MB) with 10 phr CNTs to enhance the dispersion of CNTs in hybrid composites. The investigation included a detailed analysis of cure characteristics, crosslink density, Payne effect, mechanical properties, and hydrogen permeation properties. After exposure to 96.3 MPa hydrogen gas, the hydrogen uptake and the change in volume and mechanical properties of the composites were assessed. We found that as the MWCNT volume fraction in fillers increased, the crosslink density, filler-filler interaction, and modulus of hybrid composites increased. The hydrogen uptake and the solubility of the composites decreased with an increasing MWCNT volume fraction in fillers. Moreover, after exposure to hydrogen gas, the change in volume and mechanical properties exhibited a diminishing trend with a higher MWCNT volume fraction. We conclude that the hybridization of CB and CNTs formed strong filler-filler networks in hybrid composites, consequently reinforcing the EPDM composites and enhancing the barrier properties of hydrogen gas.

The effects of octaphenylsilsesquioxane (OPS), fumed silica, and silica aerogel on the thermal insulation properties of ethylene propylene diene monomer (EPDM) rubber were studied. On this basis, two kinds of fillers with good performances were selected to study the thermal insulation of an EPDM full-formula system. The results show that the addition of fumed silica or silica aerogel had a positive effect on the thermal insulation performance of EPDM rubber and its composite. A 30 wt% silica aerogel can be well dispersed in the EPDM rubber system and with a lower thermal conductivity compared with fumed silica. EPDM composite with 23.4 wt% fumed silica can produce more char residues at 1000 °C than at 500 °C in a burn-through test and formed the compact and porous char at 1000 °C, which had a lowest thermal conductivity. EPDM composite with fumed silica cannot be burned through 1000 °C burning, and comparison with silica aerogel revealed that it achieved the lowest back temperature and had a temperature of 388 °C after 800 s.

The EPDM (ethylene-propylene-diene monomer) hybrids with improved thermal and radiation strengths containing 1 and 5 phr of polyhedral oligomeric silsesquioxane (vinyl-POSS, Ov-POSS) and/or 2 phr of microalgae (Chlorella vulgaris (CV) and Spirulinaplatensis (SP)) powders were investigated in respect to their thermal stability after γ-irradiation. The material durability under accelerated degradation was qualified by chemiluminescence and gelation, which prove the contribution of inorganic filler and microalgae extracts on the increase of hybrid thermal stability, as well as the interaction between added components (POSS and CV or SP). The activation energies and the durabilities under accelerated degradation were calculated, indicating their suitable usage as appropriate materials in various applications. The reported results indicate the improvement effect of both microalgal powders on the oxidation strength, but the contribution of Spirulinaplatensis grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulinaplatensis (2 phr), certifying its suitability for the pertinent applications.

In the present literature survey, we focused on the performance of polymeric materials encompassing silicone rubber (SiR), ethylene propylene diene monomer (EPDM) and epoxy resins loaded with micro, nano, and micro/nano hybrid fillers. These insulators are termed as composite insulators. The scope of the added fillers/additives was limited to the synthetic inorganic family. Special attention was directed to understanding the effect of fillers on the improvement of the thermal conductivity, dielectric strength, mechanical strength, corona discharge resistance, and tracking and erosion resistance performance of polymeric materials for use as high-voltage transmission line insulators. The survey showed that synthetic inorganic fillers, which include silica (SiO2) and hexagonal boron nitride (h-BN), are potential fillers to improve insulation performance of high-voltage insulators. Furthermore, nano and micro/nano filled composites performed better due to the better interaction between the filler and polymer matrix as compared to their only micro- or nano filled counterparts. Finally, some aspects requiring future work to further exploit fillers are identified and discussed.

The research and development (R&D) in rubber formulation development require reproducible, repeatable, fast, accurate, and efficient sample preparation. The lab-scale formulation development is conventionally carried out using small-scale internal mixers and two-roll mills. However, high torque laboratory twin-screw micro-compounder, which have been serving the plastic industry for more than 30 years, can be used to formulate new rubber compounds for fast and accurate sample preparation that on top can contribute to the economics of R&D. In this study, we investigated the possibility of using lab-scale 15 mL high torque twin-screw micro-compounder as a tool for new rubber compound development. For this purpose, we formulated EPDM/carbon black and EPDM/silica recipes through conventional way using a Banbury mixer followed by a two-roll mill, and through the possible way using a lab-scale 15 mL twin-screw micro-compounder. We crosslinked both systems via hot press at a predefined temperature and time. The rheological and mechanical properties of the compounds were investigated. Moreover, the dispersion of carbon black and silica in the EPDM matrix was judged by DisperGrader and scanning electron microscope (SEM). The conventional way of sample preparation was compared with a possible sample preparation method based on materials’ parameters and ease of operation.

Silica fume (SF) is a by-product from the production of silicon metal, which has a relatively high silica concentration. The surface modified silica fume (mSF) is treated with (3-mercaptopropyl) trimethoxysilane (MPTMS) as filler in ethylene propylene diene monomer (EPDM) foam. The FTIR spectra of mSF clearly indicated that MPTMS can be successfully bonded to the SF surface. The reinforcing efficiency of mSF-filled EPDM foam insulation indicated that the mechanical properties such as hardness, tensile strength, modulus, and compression set enhanced higher than in case of SF and calcium carbonate. While the cure characteristics such as the maximum torque (MH), the minimum torque (ML) and the differential torque (MH-ML) are increasing in proportion to increasing filler contents, mainly with mSF. For the cure behavior, the mSF-filled EPDM foam insulation showed the fastest cure time (tc90) and scorch time (ts2) due to reduced accelerator adsorption. Whereas, the calcium carbonate-filled EPDM foam insulation increased the cure time (tc90) and scorch time (ts2), therefore, it also prevents compound scorching. The results indicated that the mSF with MPTMS can be used as an alternative filler for EPDM foam insulation.

The compounding of waste EPDM from postindustrial scrap with polypropylene (PP) is a possible way to manufacture thermoplastic elastomers to solve a significant environmental problem. Accordingly, the present study considers the one-step (OS), two-step (TS), and dynamic revulcanization (DR) compounding methods for the manufacturing of PP/EPDM blends at different ratios of components with the aid of an ultrasonic twin-screw extruder (TSE) at various ultrasonic amplitudes. In the OS method, PP and waste EPDM particles were directly compounded using TSE with and without ultrasonic treatment. In the TS and DR methods, the waste EPDM particles were fed into the TSE and devulcanized without and with ultrasonic treatment. Then, in the TS method the devulcanized EPDM was compounded with PP using TSE without the imposition of ultrasound. In the DR method, the devulcanized EPDM after compounding with curatives was mixed with PP and dynamically revulcanized without the imposition of ultrasound in TSE. The die pressure during compounding was recorded and correlated with the rheological properties of compounds. The mechanical properties of the PP/EPDM blends obtained in the OS and TS methods did not show any improvement with ultrasonic treatment. In the DR method, all the PP/EPDM blends showed a significant increase in the tensile strength and elongation with ultrasonic amplitude and a slight decrease in the Young’s modulus. In particular, a tensile strength of 30 MPa and an elongation at break of 400% were achieved at an ultrasonic amplitude of 13 μm for the PP/EPDM blend at a ratio of 75/25. The complex viscosity, storage, and loss moduli of dynamically revulcanized PP/EPDM blends increased with the ultrasonic amplitude while the loss tangent decreased. At the same time, the results for the blends obtained by the OS and TS methods showed an opposite trend in the dynamic property behavior with the ultrasonic amplitude. Optical micrographs indicated that the blends obtained by the DR method at an ultrasonic treatment at 13 μm showed the lowest sizes of dispersed revulcanized EPDM particles in the PP matrix, leading to the excellent performance of these thermoplastic elastomers.

The effect of the strain rate on damage in carbon black filled Ethylene Propylene Diene Monomer rubber (EPDM)stretched during single and multiple uniaxial loading is investigated. This has been performed by analyzing the stress–strain response, the evolution of damage by Digital Image Correlation (DIC), the associated dissipative heat source by InfraRed thermography (IR), and the chains network damage by swelling. The strain rates were selected to cover the transition from quasi-static to medium strain rate conditions. In single loading conditions, the increase of the strain rate yields in a preferential damage of the filler network while the rubber network is preserved. Such damage is accompanied by a stress softening and an adiabatic heat source rise. Conversely, increasing the strain rate in cyclic loading conditions yields in a filler network accommodation and a high self-heating whose combined effect is proposed as a possible cause of the ability of filled EPDM to limit damage by reducing cavities opening during loading, and favoring cavities closing upon unloading.

Composites based on ethylene–propylene–diene terpolymer (EPDM), butyl/halobutyl rubber and nanosilica were prepared by melt mixing and subjected to different doses of electron beam irradiation. The effect of irradiation dose on the mechanical properties, morphology, glass transition temperature, thermal stability and water uptake was investigated. The efficiency of the crosslinking by electron beam irradiation was analyzed by Charlesby–Pinner parameter evaluation and crosslink density measurements. The scanning electron microscopy data showed a good dispersion of nanosilica in the rubber matrix. An improvement in hardness and 100% modulus was revealed by increasing irradiation dose up to 150 kGy. The interaction between polymer matrix and nanosilica was analyzed using the Kraus equation. Additionally, these results indicated that the mechanical properties, surface characteristics, and water uptake were dependent on crosslink characteristics.

Hybrid ethylene-propylene-diene-monomer (EPDM) nanocomposite foams were produced via compression molding with enhanced electromagnetic wave absorption efficiency. The hybrid filler, consisting of 20 phr ferroelectric barium titanate (BT) and various loading fractions of multi-wall carbon nanotubes (MWCNTs), synergistically increased the electromagnetic (EM) wave absorption characteristics of the EPDM foam. Accordingly, while the EPDM foam filled with 20 phr BT was transparent to the EM wave within the frequency range of 8.2–12.4 GHz (X-band), the hybrid EPDM nanocomposite foam loaded with 20 phr BT and 10 phr MWCNTs presented a total shielding effectiveness (SE) of ~22.3 dB compared to ~16.0 dB of the MWCNTs (10 phr). This synergistic effect is suggested to be due to the segregation of MWCNT networks within the cellular structure of EPDM, resulting in enhanced electrical conductivity, and also high dielectric permittivity of the foam imparted by the BT particles. Moreover, the total SE of the BT/MWCNTs loaded foam samples remained almost unchanged when subjected to repeated bending due to the elastic recovery behavior of the crosslinked EPDM foamed nanocomposites.

Ceramifiable ethylene propylene diene monomer (EPDM) composites with fiber network structures were prepared by using aramid fiber (AF), ammonium polyphosphate (APP), and silicate glass frits (SGF). The effect of AF on the curing characteristic of the ceramifiable EPDM composites was studied. The morphology of AF in the composites system was observed by optical microscopy (OM) and scanning electron microscope (SEM). The effects of the observed AF network structures on the solvent resistance, mechanical properties, ablative resistance, self-supporting property, and ceramifiable properties of the composites were investigated. Results suggested that the existence of the AF network structure improved the vulcanization properties, solvent resistance, thermal stability, and ablative resistance of the EPDM composites. An excellent self-supporting property of the EPDM composites was obtained by combining the formation of the AF network and the formation of crystalline phases at higher temperature (above 600 °C). The thermal shrinkage performance of AF and the increased thermal stability of the EPDM composites improved the ceramifiable properties of the EPDM composites.

The need for electromagnetic interference (EMI) shields has risen over the years as the result of our digitally and highly connected lifestyle. This work reports on the development of one such shield based on vulcanized rubber foams. Nanocomposites of ethylene–propylene–diene monomer (EPDM) rubber and multiwall carbon nanotubes (MWCNTs) were prepared via hot compression molding using a chemical blowing agent as foaming agent. MWCNTs accelerated the cure and led to high shear-thinning behavior, indicative of the formation of a 3D interconnected physical network. Foamed nanocomposites exhibited lower electrical percolation threshold than their solid counterparts. Above percolation, foamed nanocomposites displayed EMI absorption values of 28–45 dB in the frequency range of the X-band. The total EMI shielding efficiency of the foams was insignificantly affected by repeated bending with high recovery behavior. Our results highlight the potential of cross-linked EPDM/MWCNT foams as a lightweight EM wave absorber with high flexibility and deformability.

Much effort has been made to enhance the toughness of poly (lactic acid) (PLA) to broaden its possible range of usage in technical applications. In this work, the compatibility of PLA with a partly bio-based ethylene-propylene-diene-rubber (EPDM) through reactive extrusion was investigated. The concentration of EPDM in the PLA matrix was in the range of up to 20%. The reactive extrusion was carried out in a conventional twin-screw extruder. Contact angle measurements were performed to calculate the interfacial tension and thus the compatibility between the phases. The thermal and mechanical properties as well as the phase morphology of the blends were characterized. A copolymer of poly (ethylene-co-methyl acrylate-co-glycidyl methacrylate) (EMAGMA) was used as compatibilizer, which leads to a significant reduction in the particle size of the dispersed rubber phase when compared with the blends without this copolymer. The use of EMAGMA combined with soybean oil (SBO) and a radical initiator enhances the elongation at break of the compound. The results indicate that the reduction of the particle size of the dispersed phase obtained with the compatibilizer alone is not sufficient to improve the mechanical properties of the blend system. The induced radical reactions also influenced the mechanical properties of the blend significantly.

Determining a suitable and reliable end-of-lifetime criterion for O-ring seals is an important issue for long-term seal applications. Therefore, seal failure of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) O-rings aged in the compressed state at 125 °C and at 150 °C for up to 1.5 years was analyzed and investigated under static conditions, using both non-lubricated and lubricated seals. Changes of the material properties were analyzed with dynamic-mechanical analysis and permeability experiments. Indenter modulus measurements were used to investigate DLO effects. It became clear that O-rings can remain leak-tight under static conditions even when material properties have already degraded considerably, especially when adhesion effects are encountered. As a feasible and reliable end-of-lifetime criterion for O-ring seals under static conditions should include a safety margin for slight dimensional changes, a modified leakage test involving a small and rapid partial decompression of the seal was introduced that enabled determining a more realistic but still conservative end-of-lifetime criterion for an EPDM seal.

The effects of electron beam irradiation on the properties of ethylene propylene diene monomer (EPDM)/butyl rubber composites in presence of a polyfunctional monomer were investigated by means of differential scanning calorimetry (DSC), thermal analysis, scanning electron microscopy (SEM), attenuated total reflection absorption infrared spectroscopy (ATR-IR), and mechanical and surface energy measurements. The samples were exposed over a wide range of irradiation doses (20⁻150 kGy). The EPDM matrix was modified with butyl rubber, chlorobutyl rubber, and bromobutyl rubber. The gel content and crosslink density were found to increase with the electron beam irradiation dose. The values of the hardness and modulus increased gradually with the irradiation dose, while the tensile strength and elongation at break decreased with increasing irradiation dose. The EPDM/butyl rubber composites presented a higher thermal stability compared to the initial EPDM sample. The incorporation of butyl rubbers into the EPDM matrix led to an increase in material hydrophobicity. A similar trend was observed when the irradiation dose increased. The greatest change in the surface free energy and the contact angles occurs at an irradiation dose of 20 kGy. The Charlesby⁻Pinner plots prove the tendency to crosslinking as the irradiation dose increases.

Ground tire rubber (GTR) is a product obtained by grinding worn tire treads before retreading them or via the cryogenic or ambient temperature milling of end-of-life tires (ELTs). The aim of this study is to evaluate if calcium carbonate can be substituted by GTR and, if so, to what extent. Different types of ground tire rubber are incorporated in an EPDM (ethylene-propylene-diene-rubber) model compound as partial or complete substitutes of calcium carbonate. The raw compounds and the vulcanizates are characterized to identify the limits. In general, it is apparent that increasing amounts of GTR and larger particles degrade the mechanical properties. The GTR also influences the vulcanization kinetics by reducing the scorch time up to 50% and vulcanization time up to nearly 80%. This is significant for production processes. The compounds with one-third substitution with the smaller-particle-size GTR show mostly similar or even better properties than the reference.

Ethylene/propylene (E/P) and ethylene/propylene/5-ethylidene-2-norbornene (E/P/ENB) copolymers were obtained on rac -Et(2-MeInd) 2 ZrMe 2 activated by a number of isobutylaluminium aryloxides: (2,6- t Bu 2 PhO-)Al i Bu 2 (1-DTBP) (2,6- t Bu 2 ,4-Me-PhO-)Al i Bu 2 (1-BHT), (2,4,6- t Bu 2 PhO-)Al i Bu 2 (1-TTBP), (2,6- t Bu 2 ,4-Me-PhO-) 2 Al i Bu (2-BHT), (2,6- t Bu 2 PhO-)2Al i Bu (2-DTBP), [(2-Me,6- t Bu-C 6 H 3 O)Al i Bu 2 ] 2 (1-MTBP), [(2,6-Ph 2 -PhO)Al i Bu 2 ] 2 (1-DPP). This study shows how the structure of an activator influences catalytic activity and polymer properties, such as the copolymer composition, molecular weight characteristics, and thermophysical and mechanical properties. It has been shown that both the introduction of a bulky substituent in the para-position of the aryloxy group and the additional aryloxy group in the structure of an activator lead to a significant decrease in activity of the catalytic system in all studied copolymerization processes. Moreover, activation by bulkier aryloxides leads to lower levels of comonomer insertion and gives rise to higher molecular weight polymers. Broad or multiple endothermic peaks with different values of melting points are observed on the DSC curves of the copolymers obtained with different catalytic systems. The DSC of the thermally fractionated samples makes it possible to reveal the heterogeneity of the copolymer microstructure, which manifests itself in the presence of a set of lamellar crystallites of different thickness. The results also present the mechanical properties of the copolymers, such as the tensile strength (σ), elongation at break (ε), and engineering strain (EL). The synthesized E/P and E/P/ENB copolymers contain about 1-4 wt.% of the sterically hindered phenols obtained in situ as a residue of the hydrolyzed activators in the course of reaction quenching. This determines the increased thermooxidative stability of the copolymers.

Devulcanization represents the recycling of choice for a homogenous rubber waste stream because it allows revulcanization of samples previously devulcanized, making the life of the rubber virtually endless, according to the principles of circular economy. Among the many devulcanization processes, the thermo-mechanical one is the most appealing because it is a continuous process, easy to be industrialized. In this paper a comprehensive set of analyses (FTIR, TGA, DSC, elemental analyses, Py-GC/MS, swelling tests) were carried out on a post-industrial ethylene propylene diene monomer (EPDM), thermo-mechanical devulcanized in a co-rotating twin-screw extruder with different process parameters (thermal and screw profile, rpm). Results of the swelling test according to the Flory-Rehner theory and Horikx analyses show that the higher the thermal profile and the higher the rpm, the higher is the percentage of devulcanization. The quality of the devulcanized sample in terms of sol fraction and percentage of random scissions depends on the process conditions. The screw profile concurs to the efficiency of the devulcanization: the different number of kneading elements and more in general the screw profile composition affects the percentage of devulcanization, making the results in some tests more dependent on the screw speed.

In this paper Ethylene Propylene Diene Monomer rubber (EPDM) foams were filled with different amounts of paraffin, a common phase change material (PCM) having a melting temperature at about 70 °C, to develop novel rubber foams with thermal energy storage (TES) capabilities. Samples were prepared by melt compounding and hot pressing, and the effects of three foaming methods were investigated. In particular, two series of samples were produced through conventional foaming techniques, involving physical (Micropearl ® F82, MP, Lehvoss Italia s.r.l. Saronno, Italia) and chemical (Hostatron ® P0168, H, Clariant GmbH, Ahrensburg, Germany) blowing agents, while the salt leaching method was adopted to produce another series of foams. Scanning electron microscopy (SEM) and density measurements showed that MP led to the formation of a closed-cell porosity, while a mixed closed-cell/open-cell morphology was detected for the H foamed samples. On the other hand, foams produced through salt leaching were mainly characterized by an open-cell porosity. The qualitative analysis of paraffin leakage revealed that at 90 °C only the foams produced through salt leaching suffered from significant PCM leakage. Consequently, the thermo-mechanical properties were investigated only in samples produced with H and MP. Differential Scanning Calorimetry (DSC) analysis revealed that EPDM/paraffin foams were endowed by good TES properties, especially at higher PCM contents (up to 145 J/g with a paraffin amount of 60 wt%). Tensile and compressive tests demonstrated the addition of the PCM increased the stiffness at 25 °C, while the opposite effect was observed above the melting temperature of paraffin. These results suggest that the EPDM foams produced with H and MP show an interesting potential for thermal management of electronic devices.

Ethylene-propylene-diene monomer (EPDM) composites were usually enhanced with ablative additives to protect solid rocket motor (SRMs) casings. However, the poor thermal insulation caused by the high thermal conductive ablative fillers can lead to rocket motor failure. Herein, the novel EPDM composites containing alternating layers of ablative EPDM (AM) and heat-insulated EPDM (HM) were prepared through layer-multiplying extrusion. Compared with conventional EPDM ablative material, the multilayer composites showed enhanced thermal insulation and mechanical properties that could be further improved by tuning the number of layers. The ablation and thermal insulation properties possessing in AM and HM layers could be combined by forced assembly during co-extrusion, and the alternating multilayer composite was capable of showing the effect of each component. In particular, compared with AM, the maximum back-face temperature with 40 alternating layers of AM/HM decreased from 96.2 °C to 75.6 °C during oxyacetylene test, while the good ablation properties were preserved in the AM component. This significant improvement was attributed to the planar orientation and densification of ablative additives, and the interruption of conductive pathways in the through-plane direction of AM/HM alternating laminate. The anisotropic EPDM composites featuring mechanical robustness, good ablative resistance and thermal insulation suggest considerable potential application in the aerospace industry.

The cross-linking structure of the Ethylene-propylene-diene monomer (EPDM) is made up of a number of cross-linking types, including carbon atoms from the main chain or monomer and ether crosslinks formed during degradation. Through molecular dynamic simulations, the contribution of each type of cross-linked structure to the dynamics and mechanical properties of EPDM, the study's focus, were investigated. Cross-linking between the tertiary carbons of two main chains, cross-linking at the monomer's unsaturated position, ether cross-linking after oxidation, and other combinations of target cross-linked carbon atoms from different positions, totaling eight types of cross-linked types, were mixed with EPDM free chains in a 1:1 ratio to form eight types of cross-linked EPDMs. These varieties of cross-linked EPDMs were then compared to an uncross-linked EPDM in terms of density, radius of gyration, free volume, mean square displacement, and uniaxial tensile stress-strain curves. It was found that the cross-linking was always proven to have a favorable influence on mechanical characteristics; however, the relaxation inhibition effect varied. The cross-linking between the diene monomer at the C9 position resulted in a more flexible molecular shape and was more than double the free volume of the uncross-linked EPDM, resulting in an improved diffusion ability. The ether cross-linking produced by the oxidation of the side chain cross-linking improved the positive contribution to stiffness and enhanced the inhibitory impact on diffusion properties, whereas the main chain cross-linking had the opposite effect. The research presented in this study leads to a better knowledge of the microscopic aspects underlying EPDM performance.

With the increasing interest in hydrogen energy, the stability of hydrogen storage facilities and components is emphasized. In this study, we analyzed the effect of high-pressure hydrogen gas treatment in silica-filled EPDM composites with different silica contents. In detail, cure characteristics, crosslink density, mechanical properties, and hydrogen permeation properties were investigated. Results showed that material volume, remaining hydrogen content, and mechanical properties were changed after 96.3 MPa hydrogen gas exposure. With an increase in the silica content, the crosslink density and mechanical properties increased, but hydrogen permeability was decreased. After treatment, high-silica-content composites showed lower volume change than low-silica-content composites. The crack damage due to the decompression caused a decrease in mechanical properties, but high silica content can inhibit the reduction in mechanical properties. In particular, EPDM/silica composites with a silica content of above 60 phr exhibited excellent resistance to hydrogen gas, as no change in their physical and mechanical properties was observed.

In the present literature survey, we focused on the performance of polymeric materials encompassing silicone rubber (SiR), ethylene propylene diene monomer (EPDM) and epoxy resins loaded with micro, nano, and micro/nano hybrid fillers. These insulators are termed as composite insulators. The scope of the added fillers/additives was limited to the synthetic inorganic family. Special attention was directed to understanding the effect of fillers on the improvement of the thermal conductivity, dielectric strength, mechanical strength, corona discharge resistance, and tracking and erosion resistance performance of polymeric materials for use as high-voltage transmission line insulators. The survey showed that synthetic inorganic fillers, which include silica (SiO 2 ) and hexagonal boron nitride (h-BN), are potential fillers to improve insulation performance of high-voltage insulators. Furthermore, nano and micro/nano filled composites performed better due to the better interaction between the filler and polymer matrix as compared to their only micro- or nano filled counterparts. Finally, some aspects requiring future work to further exploit fillers are identified and discussed.

The EPDM (ethylene-propylene-diene monomer) hybrids with improved thermal and radiation strengths containing 1 and 5 phr of polyhedral oligomeric silsesquioxane (vinyl-POSS, Ov-POSS) and/or 2 phr of microalgae ( Chlorella vulgaris ( CV ) and Spirulina platensis ( SP )) powders were investigated in respect to their thermal stability after γ-irradiation. The material durability under accelerated degradation was qualified by chemiluminescence and gelation, which prove the contribution of inorganic filler and microalgae extracts on the increase of hybrid thermal stability, as well as the interaction between added components (POSS and CV or SP grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulina platensis grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulina platensis (2 phr), certifying its suitability for the pertinent applications.

The research and development (R&D) in rubber formulation development require reproducible, repeatable, fast, accurate, and efficient sample preparation. The lab-scale formulation development is conventionally carried out using small-scale internal mixers and two-roll mills. However, high torque laboratory twin-screw micro-compounder, which have been serving the plastic industry for more than 30 years, can be used to formulate new rubber compounds for fast and accurate sample preparation that on top can contribute to the economics of R&D. In this study, we investigated the possibility of using lab-scale 15 mL high torque twin-screw micro-compounder as a tool for new rubber compound development. For this purpose, we formulated EPDM/carbon black and EPDM/silica recipes through conventional way using a Banbury mixer followed by a two-roll mill, and through the possible way using a lab-scale 15 mL twin-screw micro-compounder. We crosslinked both systems via hot press at a predefined temperature and time. The rheological and mechanical properties of the compounds were investigated. Moreover, the dispersion of carbon black and silica in the EPDM matrix was judged by DisperGrader and scanning electron microscope (SEM). The conventional way of sample preparation was compared with a possible sample preparation method based on materials' parameters and ease of operation.

Silica fume (SF) is a by-product from the production of silicon metal, which has a relatively high silica concentration. The surface modified silica fume (mSF) is treated with (3-mercaptopropyl) trimethoxysilane (MPTMS) as filler in ethylene propylene diene monomer (EPDM) foam. The FTIR spectra of mSF clearly indicated that MPTMS can be successfully bonded to the SF surface. The reinforcing efficiency of mSF-filled EPDM foam insulation indicated that the mechanical properties such as hardness, tensile strength, modulus, and compression set enhanced higher than in case of SF and calcium carbonate. While the cure characteristics such as the maximum torque (M H ), the minimum torque (M L ) and the differential torque (M H -M L ) are increasing in proportion to increasing filler contents, mainly with mSF. For the cure behavior, the mSF-filled EPDM foam insulation showed the fastest cure time (t c90 ) and scorch time (t s2 ) due to reduced accelerator adsorption. Whereas, the calcium carbonate-filled EPDM foam insulation increased the cure time (t c90 ) and scorch time (t s2 ), therefore, it also prevents compound scorching. The results indicated that the mSF with MPTMS can be used as an alternative filler for EPDM foam insulation.

The compounding of waste EPDM from postindustrial scrap with polypropylene (PP) is a possible way to manufacture thermoplastic elastomers to solve a significant environmental problem. Accordingly, the present study considers the one-step (OS), two-step (TS), and dynamic revulcanization (DR) compounding methods for the manufacturing of PP/EPDM blends at different ratios of components with the aid of an ultrasonic twin-screw extruder (TSE) at various ultrasonic amplitudes. In the OS method, PP and waste EPDM particles were directly compounded using TSE with and without ultrasonic treatment. In the TS and DR methods, the waste EPDM particles were fed into the TSE and devulcanized without and with ultrasonic treatment. Then, in the TS method the devulcanized EPDM was compounded with PP using TSE without the imposition of ultrasound. In the DR method, the devulcanized EPDM after compounding with curatives was mixed with PP and dynamically revulcanized without the imposition of ultrasound in TSE. The die pressure during compounding was recorded and correlated with the rheological properties of compounds. The mechanical properties of the PP/EPDM blends obtained in the OS and TS methods did not show any improvement with ultrasonic treatment. In the DR method, all the PP/EPDM blends showed a significant increase in the tensile strength and elongation with ultrasonic amplitude and a slight decrease in the Young's modulus. In particular, a tensile strength of 30 MPa and an elongation at break of 400% were achieved at an ultrasonic amplitude of 13 μm for the PP/EPDM blend at a ratio of 75/25. The complex viscosity, storage, and loss moduli of dynamically revulcanized PP/EPDM blends increased with the ultrasonic amplitude while the loss tangent decreased. At the same time, the results for the blends obtained by the OS and TS methods showed an opposite trend in the dynamic property behavior with the ultrasonic amplitude. Optical micrographs indicated that the blends obtained by the DR method at an ultrasonic treatment at 13 μm showed the lowest sizes of dispersed revulcanized EPDM particles in the PP matrix, leading to the excellent performance of these thermoplastic elastomers.

The effect of the strain rate on damage in carbon black filled Ethylene Propylene Diene Monomer rubber (EPDM)stretched during single and multiple uniaxial loading is investigated. This has been performed by analyzing the stress-strain response, the evolution of damage by Digital Image Correlation (DIC), the associated dissipative heat source by InfraRed thermography (IR), and the chains network damage by swelling. The strain rates were selected to cover the transition from quasi-static to medium strain rate conditions. In single loading conditions, the increase of the strain rate yields in a preferential damage of the filler network while the rubber network is preserved. Such damage is accompanied by a stress softening and an adiabatic heat source rise. Conversely, increasing the strain rate in cyclic loading conditions yields in a filler network accommodation and a high self-heating whose combined effect is proposed as a possible cause of the ability of filled EPDM to limit damage by reducing cavities opening during loading, and favoring cavities closing upon unloading.

Composites based on ethylene-propylene-diene terpolymer (EPDM) , butyl/halobutyl rubber and nanosilica were prepared by melt mixing and subjected to different doses of electron beam irradiation. The effect of irradiation dose on the mechanical properties, morphology, glass transition temperature, thermal stability and water uptake was investigated. The efficiency of the crosslinking by electron beam irradiation was analyzed by Charlesby-Pinner parameter evaluation and crosslink density measurements. The scanning electron microscopy data showed a good dispersion of nanosilica in the rubber matrix. An improvement in hardness and 100% modulus was revealed by increasing irradiation dose up to 150 kGy. The interaction between polymer matrix and nanosilica was analyzed using the Kraus equation. Additionally, these results indicated that the mechanical properties, surface characteristics, and water uptake were dependent on crosslink characteristics.

Hybrid ethylene-propylene-diene-monomer (EPDM) nanocomposite foams were produced via compression molding with enhanced electromagnetic wave absorption efficiency. The hybrid filler, consisting of 20 phr ferroelectric barium titanate (BT) and various loading fractions of multi-wall carbon nanotubes (MWCNTs), synergistically increased the electromagnetic (EM) wave absorption characteristics of the EPDM foam. Accordingly, while the EPDM foam filled with 20 phr BT was transparent to the EM wave within the frequency range of 8.2-12.4 GHz (X-band), the hybrid EPDM nanocomposite foam loaded with 20 phr BT and 10 phr MWCNTs presented a total shielding effectiveness (SE) of ~22.3 dB compared to ~16.0 dB of the MWCNTs (10 phr). This synergistic effect is suggested to be due to the segregation of MWCNT networks within the cellular structure of EPDM, resulting in enhanced electrical conductivity, and also high dielectric permittivity of the foam imparted by the BT particles. Moreover, the total SE of the BT/MWCNTs loaded foam samples remained almost unchanged when subjected to repeated bending due to the elastic recovery behavior of the crosslinked EPDM foamed nanocomposites., Competing Interests: The authors declare no conflict of interest.

Ceramifiable ethylene propylene diene monomer (EPDM) composites with fiber network structures were prepared by using aramid fiber (AF), ammonium polyphosphate (APP), and silicate glass frits (SGF). The effect of AF on the curing characteristic of the ceramifiable EPDM composites was studied. The morphology of AF in the composites system was observed by optical microscopy (OM) and scanning electron microscope (SEM). The effects of the observed AF network structures on the solvent resistance, mechanical properties, ablative resistance, self-supporting property, and ceramifiable properties of the composites were investigated. Results suggested that the existence of the AF network structure improved the vulcanization properties, solvent resistance, thermal stability, and ablative resistance of the EPDM composites. An excellent self-supporting property of the EPDM composites was obtained by combining the formation of the AF network and the formation of crystalline phases at higher temperature (above 600 °C). The thermal shrinkage performance of AF and the increased thermal stability of the EPDM composites improved the ceramifiable properties of the EPDM composites.

The need for electromagnetic interference (EMI) shields has risen over the years as the result of our digitally and highly connected lifestyle. This work reports on the development of one such shield based on vulcanized rubber foams. Nanocomposites of ethylene-propylene-diene monomer (EPDM) rubber and multiwall carbon nanotubes (MWCNTs) were prepared via hot compression molding using a chemical blowing agent as foaming agent. MWCNTs accelerated the cure and led to high shear-thinning behavior, indicative of the formation of a 3D interconnected physical network. Foamed nanocomposites exhibited lower electrical percolation threshold than their solid counterparts. Above percolation, foamed nanocomposites displayed EMI absorption values of 28-45 dB in the frequency range of the X-band. The total EMI shielding efficiency of the foams was insignificantly affected by repeated bending with high recovery behavior. Our results highlight the potential of cross-linked EPDM/MWCNT foams as a lightweight EM wave absorber with high flexibility and deformability.