Material PropertiesComparison of cure, mechanical, electric properties of EPDM filled with Sm2O3 treated by different coupling agents
Introduction
Ethylene–propylene–diene rubber (EPDM) consisting of ethylene, propylene and unsaturated diene, is one of the popular synthetic rubbers. Due to its saturated backbone, EPDM possesses excellent resistance to heat and oxidation [1], whilst the non-polar structure endows EPDM with excellent electrical resistivity and resistance to polar solvents [2]. Thereby, it has broad application to thermoplastic vulcanizates, electrical insulation, waterproof rolls and so on. In addition, EPDM can not only vulcanize in a peroxide-cured system but also in sulfur-cured systems due to unsaturated diene. Earlier reports showed that rubber vulcanized by sulfur could accommodate more stress and exhibit higher elongation compared with peroxide-cured rubber [3], and that tensile strength and elongation at break of rubber with a mixed-cured system were higher than those of sulfur and peroxide-cured systems [4].
Commonly used fillers for EPDM include carbon black, silica, clay and fiber [5], [6], [7], [8]. The surface functional groups of a filler could influence the cure properties of EPDM and finally affect the overall properties. Earlier reports observed that channel blacks with lots of oxygen functional groups, which were reported to be acid, would retard cure, whilst furnace blacks featuring a slightly alkali characteristic because of low oxygen content would accelerate vulcanization [5], [9]. Pongdhorn et al. concluded that sulfuric atoms on the filler surface introduced by surface treatment would affect cure properties in three sulfur-cured systems, conventional, semi-efficient and efficient system [6].
Sm2O3, a rare earth oxide, with special shell structure, prominent physical, chemical, electrical and magnetic properties is often utilized in surface engineering [10]. So far, there have been few reports about the direct addition of rare earth oxide into a rubber matrix to strengthen mechanical properties. Therefore, it is interesting to incorporate Sm2O3 into EPDM. Considering the poor adhesion between Sm2O3 and EPDM and strong agglomeration among Sm2O3 particles, coupling agents were often selected to modify the surface of particles, since chemical treatment of filler surface has become the most successful method to improve rubber–filler and reduce filler–filler interactions.
Recently, much emphasis has been given to the application of coupling agents which serve, to some degree, to couple a filler to the rubber molecule on a “like-to-like” basis [6], [11], [12]. Generally, coupling agents possess two functionally active end groups, an alkoxy group which is capable of reacting with the hydroxyl group on the surface of common fillers, with the rest of the molecule having functional groups or special atoms, such as amino groups, double bonds and sulfuric atoms, which are compatible with rubber or can participate in vulcanization, leading to strong physical or chemical linkage between coupling agents and rubber molecules [13], [14], [15]. As a consequence, the coupling agent acts as a bridge between filler and rubber that enhances the rubber–filler interaction and the degree of reinforcement.
In this work, Sm2O3 particles were treated with four types of coupling agents containing carboxyl, amino group, P and S atoms to compare the cure, mechanical and electric properties of EPDM containing the treated Sm2O3. The main aim is to investigate the correlation between the functional groups in the coupling agents and properties of composites. The properties of interest included cure characteristics, crosslink density, mechanical properties, morphology of fractured surface by scanning electron microscopy and electrical properties, including dielectric constant, loss and strength, surface and volume resistivity.
Section snippets
Materials
The rubber used in this study was ethylene–propylene–diene monomer (EPDM J-4045) containing 5-ethylidene-2-norbornene (ENB) as diene, which was manufactured by Jilin Petrochem., SINOPEC. The EPDM consisted of 52.0 wt% ethylene, 40.3 wt% propylene and 7.7 wt% ENB. Compounding ingredients, such as dicumyl peroxide (DCP), zinc oxide, stearic acid, 2-mercapto benzimidazole (antioxidant MB) and polymerized 2, 2, 4-trimethyl-1, 2-dihydroquinoline (antioxidant RD) were of reagent grade. The
FT-IR analysis
From Fig. 1, it is observed that the four coupling agents all absorbed bands at 2917 cm−1, 2850 cm−1 and 1464 cm−1 assigned to asymmetric stretching vibration of methylene, symmetric stretching vibration of methylene, and methylene scissoring vibration, respectively [18]. In addition, the characteristic peaks of SA at 1701 cm−1 and 935 cm−1 are assigned to CO stretching vibration and O–H transforming vibration of –COOH, respectively [18]. As for NDZ102, characteristic absorption peak appears at 1050
Conclusions
The surface treatment of Sm2O3 with coupling agents has significant influence on cure, mechanical and crosslinking measurement of EPDM composites with Sm2O3. The reason is that the treatment could result in some functional groups being attached to filler surface. It was found that acidic carboxyl groups could make DCP partly decompose into ions and then retard cure, whereas, the amino groups which are alkali could make DCP decompose more radicals and then enhance crosslink density. The presence
References (35)
- et al.
Effect of vulcanization system on properties of thermoplastic vulcanizates based on epoxidized natural rubber/polypropylene blends
Polym. Test.
(2006) - et al.
The comparative study on microstructure and properties of nano-CeO2 and Sm2O3 particulate reinforced nickel-based composites by laser deposition
Appl. Surf. Sci.
(2008) - et al.
Surface modification of microfibrillated cellulose for epoxy composite applications
Polymer
(2008) - et al.
Enhanced interfacial interaction of rubber/clay nanocomposites by a novel two-step method
Compos. Sci. Technol.
(2008) - et al.
Photo- and thermo-oxidative degradation of photocrosslinked ethylene–propylene–diene terpolymer
Polym. Degrad. Stab.
(2003) - et al.
Aging of ethylene–propylene–diene monomer (EPDM) in artificial weathering environment
Polym. Degrad. Stab.
(2007) - et al.
Improved photovoltage and performance by aminosilane-modified PEO/P(VDF-HFP) composite polymer electrolyte dye-sensitized solar cells
Electrochim. Acta
(2008) - et al.
Rare earth hydroxycarbonate materials with hierarchical structures: preparation and characterization, and catalytic activity of derived oxides
Solid State Sci.
(2008) - et al.
Electrical conductivity and dielectric properties of PMMA/expanded graphite composites
Compos. Sci. Technol.
(2003) - et al.
Characterization of insulating particles by dielectric spectroscopy: case study for CaCO3 powders
Mater. Lett.
(2005)
Effect of Bi-containing superconducting ceramic on the volume resistivity of butyl rubber composites
Polym. Test.
Thermal and oxidative degradation of PE-EPDM blends vulcanized differently using sulfur accelerator systems
Eur. Polym. J.
Fundamentals of compounding EPDM for cost/performance
J. Elastom. Plast.
Cure characteristics and mechanical properties of styrene-butadiene rubber/acrylonitrile butadiene rubber
Mater. Lett.
Effect of rubber ratio, carbon black level, and accelerator level on natural rubber/bromobutyl rubber blend properties
J. Appl. Polym. Sci.
Effect of curing system on reinforcing efficiency of silane coupling agent
Polym. Test.
Clay nanolayer reinforcement of cis-1,4-polyisoprene and epoxidized natural rubber
J. Appl. Polym. Sci.
Cited by (32)
Improvement of mechanical and dielectrical properties of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO<inf>3</inf>) by layered mica and graphite flakes
2017, Composites Part B: EngineeringCitation Excerpt :The content of SG-Si6490 was 1 wt% of BaTiO3, mica and graphite amount. The modification process was carried out according to the previous literature [26,27]. The treated BaTiO3, mica and graphite flakes were then extracted by diethyl ether through soxhlet extractor, according to the literature [2].
Comparison of rheological, mechanical, electrical properties of HDPE filled with BaTiO <inf>3</inf> with different polar surface tension
2016, Applied Surface ScienceCitation Excerpt :The interface between BaTiO3 and HDPE is critical to the processability and overall properties of HDPE composites [11]. In literature, the application of coupling agents can improve the compatibility of inorganic fillers with polymer matrix [12]. In this study, BaTiO3 are modified by three types of coupling agents to introduce different functional groups on the surface of particles.
Surface functionalization of coal powder with different coupling agents for potential applications in organic materials
2014, Applied Surface ScienceCitation Excerpt :During the pulverizing process, OH groups were chemically bonded on the surface of the superfine Cp [23]. The [OCH2] of the NDZ-311 molecules react with the OH groups on the surface of the Cp and form a monolayer of the titanate coupling agent on the surface of the powder [22,26,27]. Scheme 3 shows the mechanism of a monolayer of the titanate coupling agent on the Cp particles.
Formation of C7-species pyrolysis products from ethylene-propylene heterosequences of poly(ethylene-co-propylene)
2011, Journal of Analytical and Applied PyrolysisCitation Excerpt :Hence, it has broad applications to electrical insulation, building construction, and automobile components. Due to their importance, a significant number of studies about EPM and EPDM in various fields have been performed [1–16]. Contents of ethylene and propylene in EPM and EPDM determine their grades.
Reinforcement of EPDM/SmBO<inf>3</inf> and EPDM/ATO composites by three types of POE: Assessment of longer chain content on crystallinity, cure, mechanical and electric properties
2011, Polymer TestingCitation Excerpt :The increased crystallinity of POEs in EPDM/filler/POE composites means more such pathways or channels and easier motion of current carriers in the composites, hence volume resistivity is reduced. According to literature, the dielectric strength is also correlated with the polarity of EPDM composites: the increased polarity could facilitate the electrical penetration in the composites [29]. In this study, the crystallinity of POE in EPDM/filler/POE composites could enhance the interfacial polarity.