Assessment of crosslink network and network defects of unfilled and filled ethylene‐propylene‐diene terpolymer using solid state nuclear magnetic relaxation spectroscopy

Reinforced rubbers are complex compared to unfilled systems. There are differences in the mechanisms affecting network molecular structure as well as properties of the rubber materials. In this article investigation of crosslink network and untied network defects on a molecular level of unfilled and carbon black filled ethylene‐propylene‐diene terpolymer was carried out using proton solid‐state double‐quantum NMR spectroscopy. The results show that the filled system demonstrates lower cure efficiency in conjunction with more noncoupled network defects than the unfilled one. In addition, the filled system yields the greater spatial heterogeneity because of the localization of the free radicals at the rubber–filler boundary. These strongly influence the mechanical properties of the filled rubber. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44224.     

Structural determination of ethylene‐propylene‐diene rubber (EPDM) containing high degree of controlled long‐chain branching

This work highlights an attempt to characterize the degree and nature of long‐chain branching (LCB) in an unknown sample of ethylene‐propylene‐diene rubber (EPDM). Two EPDM rubbers selected for this study were comparable in comonomer compositions but significantly different with respect to molar mass and the presence of LCB. Both rubbers contained 5‐ethylidene‐2‐norbornene (ENB) as diene. Solution cast films of pure EPDM samples were used for different characterization techniques. ¹H‐NMR, and ¹³C‐NMR were used for assessing the comonomer ratios and LCB. Size exclusion chromatography (SEC) equipped with triple detector system was used to determine the molar mass (both absolute and relative) and polydispersity index (PDI). Presence of branching was also detected using sec‐viscometry. Rheological analysis has also been used for characterizing LCB. Finally, on the basis of the experimental findings and the available theories, an attempt was made to identify the chemical nature and degree of LCB. This study reveals the possibility of detailed characterization of molecular architecture of EPDM containing LCB by comparing with an essentially linear EPDM in light of an existing theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

The miscibility of polymers is not only an important basis for selecting a proper blending method, but it is also one of the key factors in determining the morphology and properties of the blends. The miscibility between ethylene‐propylene‐diene terpolymer (EPDM) and polypropylene (PP) was explored by means of dynamic mechanical thermal analysis, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results showed that a decrease in the PP content and an increase of the crosslinking density of EPDM in the EPDM/PP blends caused the glass‐transition temperature peaks of EPDM to shift from a lower temperature to higher one, yet there was almost no variance in the glass‐transition temperature peaks of PP and the degree of crystallinity of PP decreased. It was observed that the blends prepared with different mixing equipment, such as a single‐screw extruder and an open mill, had different mechanical properties and blends prepared with the former had better mechanical properties than those prepared with the latter. The TEM micrographs revealed that the blends were composed of two phases: a bright, light PP phase and a dark EPDM phase. As the crosslinking degree of EPDM increased, the interface between the phases of EPDM and PP was less defined and the EPDM gradually dispersed in the PP phase became a continuous phase. The results indicated that EPDM and PP were both partially miscible. The mechanical properties of the blends had a lot to do with the blend morphology and the miscibility between the blend components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 315–322, 2002     

Effect of orientation and content of carbon based fillers on thermal conductivity of ethylene‐propylene‐diene/filler composites

In this study, synthetic graphite, carbon fiber, and carbon nanotube were used as thermal conductive fillers and ethylene‐propylene‐diene (EPDM) as matrix. Oriented EPDM/filler composites were prepared with two‐roll mill, and the effects of orientation and content of carbon based fillers on thermal conductivity and tensile strength of the composites were investigated. Parallel thermal conductivity of the oriented composites is significantly higher than normal thermal conductivity of the oriented composites. Especially, at 31.6% graphite content, parallel thermal conductivity of oriented composites is 7.14 W/mK. Very high thermal conductivity was achieved for oriented EPDM/graphite composites. Orientation of the fillers using two‐roll mill significantly improves the thermal conductivity in the orientation direction. For all the EPDM/filler composites, tensile strength of orientation direction is higher than that of normal direction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41000.     

Effect of adhesive‐coated glass fiber in natural rubber (NR), acrylonitrile rubber (NBR), and ethylene–propylene–diene rubber (EPDM) formulations. I. Effect of adhesive‐coated glass fiber on the curing and tensile properties of NR,NBR, and EPDM formulations

Adhesive‐coated glass fibers (3 and 6 mm in length) were added at loadings of 10, 20, and 30 phr in natural rubber (NR), nitrile rubber (NBR), and ethylene–propylene–diene comonomer (EPDM) formulations in both plain and carbon black mixes. The compounds were mixed in a two‐roll mill and were characterized for their cure properties, tensile, tear, and Mullin's effect. In NR mixes, all of the formulations showed reversion in cure behavior, suggesting that NR remained unaffected. In NBR and EPDM mixes, almost all of the mechanical properties of the fiber improved. The result was more significant in EPDM than in NBR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1111–1123, 2004     

Photocrosslinking of an ethylene–propylene–diene terpolymer and the characterization of its structure and mechanical properties

An ethylene–propylene–diene terpolymer (EPDM) was photocrosslinked under UV irradiation with benzil dimethyl ketal (BDK) as a photoinitiator and trimethylolpropane triacrylate (TMPTA) as a crosslinker. The efficiency of the photoinitiated crosslinking system EPDM–BDK–TMPTA, various factors affecting the crosslinking process (the photoinitiator and crosslinker and their concentrations, the irradiation time, the temperature, the atmosphere and UV‐light intensity, and the depth of the UV‐light penetration), and the mechanical properties of photocrosslinked EPDM were examined extensively through the determination of the gel contents, infrared spectra, and mechanical measurements. EPDM samples 3 mm thick were easily crosslinked with a gel content of about 90% after 30 s of UV irradiation under optimum conditions. The photoinitiating system of a suitable initiator combined with a multifunctional crosslinker such as BDK–TMPTA enhanced the efficiency of the photocrosslinking reaction, especially by increasing the initial rate of crosslinking. The gel content of photocrosslinked EPDM, which was determined by the content of diene in EPDM, the depth of the UV‐light penetration, and the light intensity, played a key role in increasing the mechanical properties of the photocrosslinked samples in this work. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1837–1845, 2004     

Stable superhydrophobic surface based on low‐density polyethylene/ethylene‐propylene‐diene terpolymer thermoplastic vulcanizate

Stable superhydrophobic surface based on low‐density polyethylene (LDPE)/ethylene–propylene–diene terpolymer (EPDM) thermoplastic vulcanizate (TPV) was successfully fabricated by using etched aluminum foil as template. The etched aluminum template consisted of micropores and step‐like textures, was obtained by the metallographic sandpaper sanding and the subsequent acid etching. The surface morphology and hydrophobic properties of the series molded TPV surfaces were researched by varying the weight ratio of the LDPE/EPDM TPV. The superhydrophobic LDPE/EPDM TPV surfaces exhibited the microstructures consisting of step‐like textures obtained via molding with etched aluminum template and a large number of fiber‐like structures resulted from the plastic deformation of LDPE matrix. The obtained TPV (LDPE/EPDM weight ratio = 70/30) surface exhibited the remarkable superhydrophobicity, with a contact angle of 152.0° ± 0.7° and a sliding angle of 3.1° ± 0.8°. The molded TPV surface had excellent environmental stability when the pH of water solution was in the range of 1 to 14; moreover, the surface also showed the excellent resistance to various organic solvents. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46241.     

Ethylene–propylene‐diene terpolymer/halloysite nanocomposites: Thermal,mechanical properties,and foam processing

Ethylene–propylene‐diene terpolymer (EPDM)/halloysite nanotube (HNT) nanocomposites were prepared by melt mixing in an internal mixer using a commercially available maleated semicrystalline EPDM and HNT. Transmission electron microscopy analysis of the EPDM/HNT composites revealed that the HNTs are uniformly dispersed at a nanometer scale in the matrix. Differential scanning calorimeter studies indicated that the HNT caused an increase in the nonisothermal crystallization temperature of the EPDM. Tensile and dynamic mechanical analysis exhibited that a small amount of the HNTs effectively enhanced the stiffness of the EPDM without adversely affecting its elongation‐at‐break. The EPDM/HNT nanocomposites were used to produce foams by using a batch process in an autoclave, with supercritical carbon dioxide as a foaming agent. The nanocomposite foams showed a smaller cell size and higher cell density as compared to the neat EPDM foam, and the nanocomposite with 10 phr HNT produced a microcellular foam with average cell size as small as 7.8 μm and cell density as high as 1.5 × 10¹⁰ cell/cm³. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40307.     

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

The 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.     

Effect of ultrasound on extrusion of polypropylene/ethylene–propylene–diene terpolymer blend: Processing and mechanical properties

The effects of ultrasonic irradiation on extrusion processing and mechanical properties of polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM) blends are examined. Results show that appropriate irradiation intensity can prominently decrease die pressure and apparent viscosity of the melt, increase output, as well as increase toughness of PP/EPDM blends without harming rigidity. In case the blends are extruded with ultrasonic irradiation twice, the impact strength of the blend rises sharply at 50–100 W ultrasonic intensity, and amounts to more than 900 J/m, 1.5 times as high as that of blend without ultrasonic irradiation. Scanning electron microscopy observation shows that with ultrasonic irradiation, morphology of uniform dispersed EPDM phase and good adhesion between EPDM and PP matrix was formed in PP/EPDM blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3519–3525, 2003     

Conducting blends of poly(o‐toluidine) and ethylene–propylene–diene terpolymer

Poly(o‐toluidine) (POT) is an electroactive polymer with poor mechanical and thermal characteristics. We examined the scope for improving such properties by making blends of POT with ethylene–propylene–diene rubber (EPDM). We prepared POT–EPDM blends containing different weight fractions of POT by intimately mixing known volumes of separate solutions of the two polymers (POT in THF and EPDM in toluene). Films of EPDM and POT–EPDM blends in solution were obtained by spreading, solvent evaporation, and film casting techniques. POT, EPDM, and their blends were characterized in solution by ultraviolet‐visible spectroscopy, and the respective dried samples were analyzed by Fourier transform infrared spectroscopy and thermogravimetry. The polymer samples were further analyzed morphologically by scanning electron microscopy, and their tensile strengths were also evaluated. Spectroscopic and thermal studies of the blends indicated some sort of interaction between the two constituent polymers. The direct current electrical conductivity of the blends in increasing order of POT loading (12.5–100%) was in the range 9.9 × 10^?5 to 11.6 × 10^?2 S cm^?1. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2550–2555, 2003     

Dynamic mechanical analysis of ethylene–propylene–diene monomer rubber and styrene–butadiene rubber blends

The effects of blend ratio, crosslinking systems, and fillers on the viscoelastic response of ethylene–propylene–diene monomer (EPDM)/styrene–butadiene rubber (SBR) blends were studied as functions of frequency, temperature, and cure systems. The storage modulus decreased with increasing SBR content. The loss modulus and loss tangent results showed that the EPDM/SBR blend vulcanizate containing 80 wt % EPDM had the highest compatibility. Among the different cure systems studied, the dicumyl peroxide cured blends exhibited the highest storage modulus. The reinforcing fillers were found to reduce the loss tangent peak height. The blend containing 40 wt % EPDM showed partial miscibility. The dispersed EPDM phase suppressed the glass‐transition temperature of the matrix phase. The dynamic mechanical response of rubbery region was dominated by SBR in the EPDM–SBR blend. The morphology of the blend was studied by means of scanning electron microscopy. The blend containing 80 wt % EPDM had small domains of SBR particles dispersed uniformly throughout the EPDM matrix, which helped to toughen the matrix and prevent crack propagation; this led to enhanced blend compatibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of anhydride‐modified ethylene–propylene–diene rubber and ethylene–vinyl acetate copolymers on the compatibilization of nitrile rubber/ethylene–propylene–diene rubber blends

The effects of maleic anhydride modified ethylene–propylene–diene rubber (EPDMMA) and maleic anhydride modified ethylene–vinyl acetate (EVAMA) on the compatibilization of nitrile rubber (NBR)/ethylene–propylene–diene rubber (70:30 w/w) blends vulcanized with a sulfur system were investigated. The presence of EPDMMA and EVAMA resulted in improvements of the tensile properties, whereas no substantial change was detected in the degree of crosslinking. The blend systems were also analyzed with scanning electron microscopy and dynamic mechanical thermal analysis. The presence of EVAMA resulted in a blend with a more homogeneous morphology. The compatibilizing effect of this functional copolymer was also detected with dynamic mechanical analysis. A shift of the glass‐transition temperature of the NBR phase toward lower values was observed. The presence of EPDMMA and EVAMA also increased the thermal stability, as indicated by an improvement in the retention of the mechanical properties after aging in an air‐circulating oven. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2408–2414, 2003     

Effects of peroxide and phenolic cure systems on characteristics of the filled ethylene–propylene–diene monomer rubber (EPDM)

The effects of three curing systems, peroxide, peroxide–phenolic combination, and phenolic on selected properties of cured carbon black‐filled ethylene–propylene–diene monomer rubber (EPDM) were investigated. The cured rubbers immersed in hot amine solution to evaluate their suitability for seal and gasket industry at elevated temperature and amine environments. These tests were essential for evaluating the durability of the gasket in a gas refinery. The Fourier transform infrared spectroscopy spectrums revealed that the phenolic crosslink was constructed between rubber macromolecules during the curing process. The changing curing system from peroxide to peroxide–phenolic and phenolic increased the glass transition temperature of the filled cured rubbers between 3 and 5 °C. There was not any significant difference between thermogravimetric analysis thermographs of the selected cured rubbers with various cure systems and the residues ranged between 45% and 47%. Unlike of peroxide curing system, a dual phase was observed from scanning electron microscopy micrographs for peroxide–phenolic and phenolic cure systems. The phenolic cure system was not beneficial for rubber curing although, it reduced scorch time of the curing process. For the most studied mechanical properties, phenolic cure system deteriorated mechanical properties for both, aged and unaged cured rubbers. Increasing the amount of diene monomer in EPDM structure was beneficial for phenolic rubber cure system. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46213.     

Viscosities of ethylene–propylene–diene terpolymer blends in oil

Viscosities were obtained on oil solutions of two ethylene–propylene–diene terpolymers (EPDMs) and their blends. For the amorphous terpolymer with 59 mol% ethylene, intrinsic viscosities were constant between–10 and 40°C. The viscosities decreased rapidly at low temperature for blends of this material with as little as 20 wt % of a slightly crystalline EPDM with 79 mol% ethylene. Dynamic viscosity measurements on 1.0% solutions of blends likewise gave considerably smaller values at low temperature than measurements on an amorphous EPDM of similar molecular weight. The data are in agreement with the view that longer ethylene sequences that crystallize in the bulk polymer can organize in oil into ordered domains that interfere less with flow than the disordered amorphous polymer regions. © 1993 John Wiley & Sons, Inc.     

Effects of EPDM‐g‐MAH compatibilizer and internal mixer processing parameters on the properties of NR/EPDM blends: An analysis using response surface methodology

This study evaluates the effects of ethylene‐propylene‐diene‐monomer grafted maleic anhydride (EPDM‐g‐MAH) and internal mixer melt compounding processing parameters on the properties of natural rubber/ethylene‐propylene‐diene rubber (NR/EPDM) blends. Using Response Surface Methodology (RSM) of 2⁵ two‐level fractional factorial, we studied the effects of NR/EPDM ratio, mixing temperature, Banbury rotor speed, mixing period, and EPDM‐g‐MAH contents in NR/EPDM blends. The study found that the presence of EPDM‐g‐MAH in NR/EPDM blends had a predominant role as a compatibilizing agent, which affected the processability and properties of the final material. We also determined the model fitting with constant determination, R² of 99.60% for tensile strength (TS) response with a suggested combination of mixing process input parameters. The reproducibility of the proposed mixing strategy was then confirmed through model validation with a minor deviation at +2.303% and higher desirability of 0.960. This study is essential in providing a process design reference for NR/EPDM blends preparation by melt‐blending and the role of a compatibilizer from the systematic Design of Experiment (DOE) approach. The experimental findings were further supported with swelling and cross‐link density measurements, differential scanning calorimetry analysis, and observation of fracture morphology using a scanning electron microscope. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42199.     

Effect of formulation variables on cure kinetics,mechanical, and electrical properties of filled peroxide cured,ethylene‐propylene‐diene monomer compounds

Peroxide crosslinkable ethylene–propylene–diene monomer (EPDM) compounds are formulated systems in which the base polymer generally comprises only a small fraction of the total composition. Knowledge of the intercomponent dependency is therefore crucial for successful product development. In this study, we have investigated the effect of formulation components on key material properties of cured, filled, and oil extended EPDM. In studying the impact of individual components, the clay filler was found to have a significant and negative effect on cure performance and to a lesser extent on the dielectric strength as well. On the other hand, the oil plasticizer was found to have a positive effect on recovery of the cure efficiency in filled compounds. It was also found that the interaction of the filler, the plasticizer oil, and the peroxide impacted both the mechanical properties as well as the dielectric strength. Given the complexity of the system, a statistical experimental design method was adopted to study the interactions of the components and their impact of final properties. For selected compositions, the cure behavior and the evolution of properties with extent of cure were studied. The cure was also modeled and compared to previously proposed models available in the literature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Degradation kinetics of vulcanized ethylene–propylene–diene terpolymer residues

In this study, ethylene–propylene–diene terpolymer residues (EPDM‐r) from the automotive industry were analyzed by thermogravimetric analysis (TGA) for determination of the activation energy (E_a) of decomposition by the Flynn‐Wall‐Ozawa (FWO) method. The degradation mechanism was determined by the method of Criado et al. Analysis of the nonvulcanized EPDM gum (EPDM‐g) and paraffinic oil used in the composition of the compound was also carried out. The E_a values for the decomposition of the EPDM‐g and paraffinic oil remained constant with the conversion, but for the EPDM‐r decomposition, they changed due to the initial oil elimination followed by decomposition of the EPDM fraction. It was observed that removal of the paraffinic oil occurred less easily in the tridimensional vulcanized network, and there were differences in the elimination mechanism. The EPDM degradation mechanism was also affected by vulcanization and the fillers present in the compound. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and performances of ethylene–propylene–diene terpolymer/acrylic rubber reinforced with a dough‐modeling compound

A novel composite was prepared by the addition of a dough‐modeling compound (DMC) reinforcement and an ethylene–propylene–diene terpolymer (EPDM)/acrylic rubber (ACM) matrix. We studied the DMC/EPDM/ACM mass ratio and vulcanizing process by testing the tensile strength, Shore A hardness, elongation at break, and wear and thermal properties. The results show that the mechanical properties, thermal properties, and wear resistance of the composites were good when the DMC/EPDM/ACM mass ratio was 70/25/75 and the cure conditions were 180°C under 10 MPa for 25 min. The crosslinking structure of the composites was studied by IR, and this further proved the interaction between DMC, ACM, and EPDM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of blend ratio on cure characteristics,tensile properties,thermal and swelling properties of mica‐filled (ethylene‐propylene‐diene monomer)/(recycled ethylene‐propylene‐diene monomer) (EPDM/r‐EPDM) blends

(Ethylene‐propylene‐diene monomer)/(recycled ethylene‐propylene‐diene monomer) (EPDM/r‐EPDM) blends filled with constant mica loading were compounded at various blends ratios (i.e., 90/10, 80/20, 70/30, 60/40, and 50/50). Results indicated that scorch time decreased with increasing r‐EPDM content, whereas curing time, minimum torque, and maximum torque show the opposite trend. The tensile strength, stress at 100% elongation, and elongation at break value increased with increasing r‐EPDM loading in the blend systems and the optimum properties occurred at 70/30 EPDM/r‐EPDM blends ratio. The thermal stability of EPDM/r‐EPDM blends increased with increasing r‐EPDM content in the blends but the swelling percentage showed the opposite trend with a greater addition of r‐EPDM content in the blends. J. VINYL ADDIT. TECHNOL., 21:1–6, 2015. © 2014 Society of Plastics Engineers