Effects of thermal aging on degradation mechanism of flame retardant‐filled ethylene–propylene–diene termonomer compounds

Ethylene–propylene–diene termonomer (EPDM) compounds filled with halogenated (Br and Cl) flame retardants (FRs) and Sb₂O₃ were prepared via melt mixing, and their thermal stability, weight loss, and elemental composition were investigated as a function of aging conditions (temperature: 120–380°C, period: ～100 h, and atmosphere: nitrogen and air). The thermal aging was done with thermogravimetic analysis under both isothermal and nonisothermal conditions and a convection oven. Scanning electron microscopy–energy dispersive spectroscopy was used to study the surface morphology and elemental composition of the thermally aged FRs‐filled EPDM compounds. For a better precision of compositional analysis, a laser‐induced breakdown spectroscopy (LIBS) was employed in this study. The thermal degradation behavior of EPDM compounds containing halogenated FRs was strongly dependent on the aging atmosphere (N₂ or air) and type of FRs. The weight loss of the EPDM compounds during thermal aging was found to be quite small in the temperature ranges below 190°C, while it was noticeable above the temperature. The LIBS technique can be an effective and promising analysis tools for analyzing the elemental components in a bulk rubber compound. Two possible mechanisms were proposed for the thermal degradation of the EPDM compounds containing brominated FR and Sb₂O₃. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41324.     

Effects of peroxide and gamma radiation on properties of devulcanized rubber/polypropylene/ethylene propylene diene monomer formulation

Mechanical and thermal properties of devulcanized rubber (DR)/polypropylene (PP)/ethylene propylene diene monomer blends (EPDM) were studied at various concentrations of dicumyl peroxide (DCP) and gamma radiation doses. The blends showed improved mechanical properties for vulcanized sample. The coupling of DR/PP/EPDM with different proportions of DCP was investigated by X‐ray diffraction and scanning electron microscopy techniques. Evaluation of the developed blends, unirradiated and gamma irradiated, was carried out using elastic modulus, tensile strength, elongation at break, thermogravimetric analysis, kinetic analysis, and DSC measurements. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40611.     

Effects of epoxidized natural rubber (ENR‐50) and processing parameters on the properties of NR/EPDM blends using response surface methodology

The effects of epoxidized natural rubber (ENR‐50) and processing parameters on the properties of natural rubber/ethylene–propylene–diene rubber (NR/EPDM; 70 : 30 phr) blends were studied. The compounds were prepared by melt compounding method. Using response surface methodology of two‐level full factorial, the effects of ENR‐50 contents (?1 : 5 phr; +1 : 10 phr), mixing temperature (?1 : 50°C; +1 : 110°C), rotor speed (?1 : 40 rpm; +1 : 80 rpm), and mixing time (?1 : 5 min; +1 : 9 min) in NR/EPDM blends were evaluated. Cure characteristics and tensile properties were selected as the responses. The significance of factors and its interaction was analyzed using ANOVA and the model's ability to represent the system was confirmed using the constant of determination, R² with values above 0.90. It was found that the presence of ENR‐50 has the predominant role on the properties of NR/EPDM blends. The addition of ENR‐50 significantly improved cure characteristics and tensile strength up to 5.12% and 6.48% compared to neat NR/EPDM blends, respectively. These findings were further supported by swell measurement, differential scanning calorimetry, and scanning electron microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40713.     

Self‐reinforcing elastomer composites based on ethylene–propylene–diene monomer rubber and liquid‐crystalline polymer

In this study, the prime factor determining the size, shape, and distribution of liquid‐crystalline polymer (LCP) was the viscosity ratio at the processing conditions. The fiber‐forming capacity of the LCP depended on the viscosity of the ethylene–propylene–diene monomer rubber (EPDM). With increasing LCP content, the tensile and tear strengths did not increase, perhaps because of incompatibility between the EPDM and LCP. The hardness increased because of the hard mesogenic groups in the LCP. The percentage swelling decreased as the LCP content increased. With increasing LCP content, processability became easier because of a lower melt viscosity. The scorch time increased at higher LCP levels. A higher percentage crystallinity was observed with increasing LCP content. Scanning electron microscopy clearly showed the fiber phase formation, which was two‐dimensionally isotropic in nature, confirming fiber formation even in a shear field. The addition of LCP improved the thermal stability. The onset degradation temperatures shifted to higher values with increasing LCP content. Dynamic mechanical thermal analysis revealed that with the addition of LCP, the mechanical damping increased at its lower level. High‐temperature processing increased the effective amorphous zone. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 711–718, 2004     

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     

Preparation and properties of polytetrafluorethylene filled ethylene–propylene–diene monomer composites

Ethylene–propylene–diene monomer/polytetrafluorethylene (EPDM/PTFE) composites based on EPDM and electron beam irradiated PTFE powders (MS‐II, MS‐III, and MS‐V, with mean diameter 5 μm, 1 μm, and 0.1 μm, respectively) were prepared by a mechanical compounding technique. The curing characteristics, morphologies, mechanical properties, and abrasion behaviors of these composites were investigated. The curing measurements indicated that the addition of lower loading of MS‐III or MS‐V enhanced the lubrication of EPDM compounds and delayed the curing process. The morphological structure of the composites demonstrated that the MS‐III and MS‐V were uniformly dispersed in EPDM matrix and the efficient polymer–filler interfacial interactions were constructed. In comparison with EPDM/MS‐II and EPDM/MS‐III, EPDM/MS‐V exhibited outstanding tensile strength, tear strength, elongation at break, and abrasion resistance due to the nanometer particle dimension and good dispersion of MS‐V as well as the stronger interfacial interactions between MS‐V and the EPDM matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Effect of bis(diisopropyl)thiophosphoryl disulfide on the covulcanization of styrene–butadiene rubber and ethylene–propylene–diene (monomer) blends

Covulcanization of elastomer blends constituting styrene–butadiene rubber (SBR) and ethylene–propylene–diene (monomer) rubber (EPDM) was successfully performed in the presence of reinforcing fillers like carbon black and silica by using a multifunctional rubber additive, bis(diisopropyl)thiophosphoryl disulfide (DIPDIS). The polarity of EPDM rubber was increased by a two‐stage vulcanization technique, which allowed the formation of rubber‐bound intermediates. In this way the migration of both curatives and reinforcing fillers in the EPDM–SBR blend could be controlled and cure rate mismatch could be minimized. The process significantly improved the physical properties of the blend vulcanizates. The phase morphology, as evident from the SEM micrographs, was indicative of the presence of a much more compact and coherent rubber matrix in the two‐stage vulcanizates. Different accelerator systems were studied to understand better the function and effectiveness of DIPDIS in developing homogeneity in the blends of dissimilar elastomers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1231–1242, 2004     

Cure and scorch in the processing of ethylene‐propylene‐diene terpolymer (EPDM)

The objective of this work is to ascertain the characteristics of desirable (cure) and especially undesirable (scorch) crosslinking when carbon black filled ethylene propylene diene terpolymer (EPDM) is processed using different peroxide initiators. The mixing temperature and the nature of the peroxide initiator are crucial parameters affecting scorch (undesirably premature crosslinking) in this rubber. Processability and properties of EPDM prepared using various mixer set temperatures have been investigated. Dicumyl peroxide (Luperox DC), di(t‐butylperoxy) diisopropylbenzene (Luperox F), and 2,5‐dimethyl‐2,5‐di(t‐butylperoxy) hexane (Luperox 101) were used as crosslinking initiators. Higher mixing temperatures give shorter scorch times, greater scorch magnitudes, greater heterogeneities in crosslink spatial distribution and poorer tensile properties. However, extreme localization of the unwanted crosslinking at the rubber‐filler interface does have a beneficial effect. Luperox DC offers poorer processability and poorer resulting properties than do Luperox F and Luperox 101, due to its shorter half‐life and greater solubility in the rubber phase. This is the first time that the spatial heterogeneity of crosslinking and scorch has been related to the basic thermodynamics of 3‐component 2‐phase systems. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44523.     

Elastomeric conducting systems based on ethylene–propylene–norbornene composites

This work reports the preparation and structural and electrical characterizations of composites consisting of ethylene–propylene–norbornene, polypropylene, and carbon black (CB) blends, comparing the data obtained from crosslinked and noncrosslinked samples. Structural analysis provided evidence of the reinforcing effect of CB on the properties when present in the initial system, as well as of the excellent conducting properties of CB composites. This, together with their mechanical properties and their extraordinary processing ease, makes them suited as bipolar plates in fuel cells based on polymeric electrolyte. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2136–2145, 2001     

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     

Effects of the compatibilizer structural parameters on microstructural formation in ethylene–propylene–diene monomer rubber/ethylene–propylene–diene monomer rubber‐g‐maleic anhydride/organoclay nanocomposites

Nanocomposite vulcanizates based on ethylene–propylene–diene monomer rubber (EPDM) and organically modified montmorillonite with improved mechanical and barrier properties were prepared via a melt‐mixing process in the presence of maleic anhydride grafted ethylene–propylene–diene monomer rubber (EPDM‐g‐MAH) as an interfacial compatibilizer. The effects of the EPDM Mooney viscosity as the matrix and also the compatibilizer molecular weight and its maleation degree on the developed microstructure were also studied. The annealing of the vulcanized nanocomposites based on a low‐Mooney‐viscosity EPDM matrix and low‐Mooney‐viscosity EPDM‐g‐MAH enhanced the flocculation of the dispersed clay platelets; this implied that the flocculated structure for the clay nanolayers was more thermodynamically preferred in these nanocomposites. This was verified by the decrease in the oxygen permeability of the nanocomposite vulcanizates with increasing annealing time. The tendency of the clay nanosilicate layers to flocculate within the matrix of EPDM was found to be influenced by the clay volume fraction, the maleation degree, and also, the Mooney viscosity of the compatibilizer. Interfacially compatibilized nanocomposites based on high‐molecular‐weight EPDM exhibited a more disordered dispersion of the clay nanolayers, with a broadened relaxation time spectra; this was attributed to the higher shearing subjected to the mix during the melt‐blending process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Abrasion resistance of thermoplastic polyurethane materials blended with ethylene–propylene–diene monomer rubber

The effect of ethylene–propylene–diene monomer rubber (EPDM) as an additive on the abrasion resistance of a thermoplastic polyurethane (TPU) resin was investigated. The mechanical properties and microstructure of the resultant TPU/EPDM composites were evaluated, and the surface morphology of the composites after abrasion testing was examined. The results showed that the addition of EPDM greatly improved both the mechanical properties and abrasion resistance of the TPU resin. A TPU/EPDM composite with 8 wt % EPDM demonstrated the highest tensile strength, the largest elongation at break, and the best overall performance. The abrasion of this composite was 27 mg, whereas that of the pure resin was 73 mg. With the further addition of EPDM, the abrasion resistance of the resultant composites decreased, whereas the viscosity increased. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of the addition of acrylonitrile/ethylene–propylene–diene monomer (EPDM)/styrene graft copolymer on the morphology–properties relationships in poly(styrene‐co‐acrylonitrile)/EPDM rubber blends

Blends of poly(styrene‐co‐acylonitrile) (SAN) with ethylene–propylene–diene monomer (EPDM) rubber were investigated. An improved toughness–stiffness balance of the SAN/EPDM blend was obtained when an appropriate amount of acrylonitrile–EPDM–styrene (AES) graft copolymer was added, prepared by grafting EPDM with styrene–acrylonitrile copolymer, and mixed thoroughly with both of the two components of the blend. Morphological observations indicated a finer dispersion of the EPDM particles in the SAN/EPDM/AES blends, and particle size distribution became narrower with increasing amounts of AES. Meanwhile, it was found that the SAN/EPDM blend having a ratio of 82.5/17.5 by weight was more effective in increasing the impact strength than that of the 90/10 blend. From dynamic mechanic analysis of the blends, the glass‐transition temperature of the EPDM‐rich phase increased from ?53.9 to ?46.2°C, even ?32.0°C, for the ratio of 82.5/17.5 blend of SAN/EPDM, whereas that of the SAN‐rich phase decreased from 109.2 to 108.6 and 107.5°C with the additions of 6 and 10% AES copolymer contents, respectively. It was confirmed that AES graft copolymer is an efficient compatibilizer for SAN/EPDM blend. The compatibilizer plays an important role in connecting two phases and improving the stress transfer in the blends. Certain morphological features such as thin filament connecting and even networking of the dispersed rubber phase may contribute to the overall ductility of the high impact strength of the studied blends. Moreover, its potential to induce a brittle–ductile transition of the glassy SAN matrix is considered to explain the toughening mechanism. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1685–1697, 2004     

Study on the milling behavior of chloroprene rubber blends with ethylene–propylene–diene monomer rubber,polybutadiene rubber,and natural rubber

The viscoelastic properties of the blends of chloroprene rubber (CR) with ethylene–propylene–diene monomer rubber (EPDM), polybutadiene rubber (BR), and natural rubber (NR) at different temperature were studied using rubber processing analyzer (RPA). Mooney viscosities of compounds were measured and tight milling and sheeting appearance were observed on a two‐roll mill. The results showed that Mooney viscosities and the elastic modulus of the blends decreased with the increase of the temperature from 60 to 100°C. And the decreasing trends of pure CR, pure NR, and CR/NR blend compounds were more prominent than that of pure EPDM, pure BR, CR/EPDM, and CR/BR blend compounds. For CR/EPDM blend compounds, the decreasing trend became slower with the increase of EPDM ratio in the blend. Compared with pure CR, pure NR and CR/NR blend compounds, pure EPDM, pure BR compounds, and the blend compounds of CR/EPDM and CR/BR showed less sensibility to temperature and they were less sticky to the metal surface of rolls and could be kept in elastic state at higher temperature, easy to be milled up and sheeted. At the same blend ratio and temperature, the property of tight milling of the blends decreased in the sequence of CR/EPDM, CR/BR, and CR/NR. With the increase of EPDM, BR, or NR ratio in CR blends, its property of tight milling was improved. POLYM. COMPOS., 28:667–673, 2007. © 2007 Society of Plastics Engineers     

Cure characteristics,morphology, and mechanical properties of ethylene–propylene–diene–monomer rubber/acrylonitrile butadiene rubber blends

Blends based on ethylene–propylene–diene monomer rubber (EPDM) and acrylonitrile butadiene rubber (NBR) was prepared. Sulfur was used as the vulcanizing agent. The effects of blend ratio on the cure characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break, hardness, rebound resilience, and abrasion resistance have been investigated. Tensile and tear strength showed synergism for the blend containing 30% of NBR, which has been explained in terms of morphology of the blends attested by scanning electron micrographs. A relatively cocontinuous morphology was observed for 70 : 30, EPDM/NBR blend system. The experimental results have been compared with the relevant theoretical models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermal and mechanical properties of silicon rubber/cis‐polybutadiene rubber/ethylene–propylene–diene monomer blends

Considering the properties of silicon rubber, ethylene–propylene–diene monomer (EPDM), and cis‐polybutadiene rubber (BR), a blend made by a new method was proposed in this article; this blend had thermal resistance and good mechanical properties. The morphology of the blend was studied by SEM, and it was found that the adhesion between the phases of BR, EPDM, and polysiloxanes (silicon rubber) could be enhanced, and the compatibility and covulcanization were good. The influence of the mass ratio of peroxide and silica on the mechanical properties and thermal resistance of the blend was studied. The results showed that the mechanical properties and thermal resistance of the blend were improved when silicon rubber/BR/EPDM was 20/30/50, dicumyl peroxide/sulfur was 2.5/2.5, and the amount of silica was 80 phr. The integral properties of rubber blend had more advantages than did the three rubbers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4462–4467, 2006     

Thermal stability and aging characteristics of (natural rubber)/(waste ethylene‐propylene‐diene monomer terpolymer) blends

Comparative studies of the thermogravimetric analysis and thermo‐oxidative aging of (natural rubber)/(waste ethylene‐propylene‐diene monomer terpolymer) (NR/W‐EPDM) and (natural rubber)/(ethylene‐propylene‐diene monomer terpolymer) (NR/EPDM) blends were carried out. The blends were prepared at five different blend ratios (90/10, 80/20, 70/30, 60/40, and 50/50) on a two‐roll mill. As the pure EPDM or W‐EPDM content in the blends increased, their thermal stability also increased. The thermo‐oxidative aging of these blends was done at 100°C for 48 h. Afterwards, the NR/EPDM blends exhibited better retention of properties than the NR/W‐EPDM blends. Crosslink density measurements of the blends after thermal aging indicated that higher crosslink density was obtained from a higher content of EPDM or W‐EPDM, a result which might be due to the high rate of radical termination leading to crosslinks in the bulk of the polymer. J. VINYL ADDIT. TECHNOL., 20:99–107, 2014. © 2014 Society of Plastics Engineers     

The synergistic effect of aluminum hypophosphide and nanosilica on flame‐retarded ethylene–propylene–diene monomer rubber

The influence of aluminum hypophosphide (AlHPi) and nanosilica on the flame‐retardant and mechanical property of ethylene–propylene–diene monomer (EPDM) rubber was evaluated by limiting oxygen index, and the value of tensile strength and elongation at break. The results show that the introduction of nanosilica into the EPDM/AlHPi blends can not only further improve the flame‐retardant property but also improve the tensile strength and elongation at break significantly, showing a synergistic effect between AlHPi and nanosilica. The flame‐retardant mechanism was further studied by X‐ray diffraction (XRD), thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), and scanning electron microscope (SEM). The results of XRD and TG–DSC indicate that AlHPi will melt along with oxidation at about 337°C, which is helpful to full contact with nanosilica and to enhance the interaction between them; and will further recrystallize above 540°C, which is benefited to enhance the mechanical strength of char layer. The char morphological study by SEM shows that the char layer for the sample with both AlHPi and nanosilica is strong, more uniform and dense, and the scale of the holes in the char layer is smaller compared with the char layer of samples with AlHPi or nanosilica alone. The TG–DSC results show that the sample with both AlHPi and nanosilica has the weakest weight loss rate and heat release rate, compared with the samples with either of them, which is another evidence of the synergistic flame retardant effect between AlHPi and nanosilica. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012