Friction and wear behaviour of electron beam modified PTFE filled EPDM compounds

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Abstract. Tribological properties of Ethylene-Propylene-Diene-rubber (EPDM) containing electron modified Polytetrafluoroethylene (PTFE) have been investiagted with the help of pin on disk tribometer without lubrication for a testing time of 2 hrs in atmospheric conditions at a sliding speed and applied normal load of 0.05 m·s -1 and FN = 1 N, respectively. Radiation-induced chemical changes in electron modified PTFE powders were analyzed using Electron Spin Resonance (ESR) and Fourier Transform Infrared (FTIR) specroscopy to characterize the effects of compatibility and chemical coupling of modified PTFE powders with EPDM on mechanical, friction and wear properties. The composites showed different friction and wear behaviour due to unique morphology, dispersion behaviour and radiation functionalization of PTFE powders. In general, EPDM reinforced with electron modified PTFE powder demonstrated improvement both in mechanical and tribological properties. However, the enhanced compatibility of PTFE powder resulting from the specific chemical coupling of PTFE powder with EPDM has been found crucial for mechanical, friction and wear properties. Vol.3, No.1 (2009) [39][40][41][42][43][44][45][46][47][48] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2009.7 ene (PTFE) with its remarkably low friction coefficient has also gained interest for use in tribological applications [9][10][11][12]. In rubbers, PTFE was initially used as a reinforcing additive in Silicone and Fluorosilicone rubbers [13][14][15] and afterwards in Styrene-butadiene-rubber, Acrylonitrile-butadienerubber and Butyl rubber [16]. New PTFE-based rubber compounds and compounding procedures have been introduced in improving mechanical properties of both low-strength (ethylene propylene, silicone) and high-strength (nitrile) rubbers for O-rings, sealing and valves etc. [17]. However, PTFE especially in rubbers have not been achieved with any commercially significant success. This is mainly due to the intractability of PTFE in providing homogeneous formulation because of its poor wetting and dispersion characteristic. This problem results from the unique properties of PTFE, most probably its highly hydrophobic surface which resists wetting. There is indeed a strong motivation to investigate new techniques and procedures for the use of PTFE powder in rubber compound as solid lubricant for tribological applications. More recently, chemically coupled PTFE-polyamide [18] and PTFE-rubber [19] compounds based on the modification of PTFE powder by high energy electrons has opened a new way in producing materials for tribological applications. Radiation functionalization produces PTFE micropowders containing persistent trapped-radicals radicals and functional groups on the surface of PTFE powder can be easily compounded into elastomers such as EPDM rubber. A detailed characterization related to the mechanical, friction and wear properties of PTFE-based EPDM compounds have been presented by the authors in [20,21]. In previous attemp...

Section: Optimization Of Crosslinking Irradiation Dosecontrasting

confidence: 61%

Section: Optimization Of Crosslinking Irradiation Dosementioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Structure-property effects on mechanical, friction and wear properties of electron modified PTFE filled EPDM composite

Khan¹,

Lehmann²,

Heinrich³

et al. 2009

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“…In the present work the influence of dose-controlled agglomerate size, structural morphology and interfacial compatibility of PTFE nanopowder on the physical properties of the resulting modified PTFE-EPDM blends are presented. These investigations are of extreme importance especially in the development of new rubber compounds which require optimization of both the physical and tribological properties [29][30]. It has been shown that the desired physical properties can be achieved simply by controlled modification of PTFE nanopowder.…”

Section: Introductionmentioning

confidence: 99%

Modification of PTFE nanopowder by controlled electron beam irradiation: A useful approach for the development of PTFE coupled EPDM compounds

Khan¹,

Lehmann²,

Heinrich³

2008

Self Cite

Abstract. Low-temperature reactive mixing of controlled electron beam modified Polytetrafluoroethylene (PTFE) nanopowder with Ethylene-Propylene-Diene-Monomer (EPDM) rubber produced PTFE coupled EPDM rubber compounds with desired physical properties. The radiation-induced chemical alterations in PTFE nanopowder, determined by electron spin resonance (ESR) and Fourier transform infrared (FTIR) spectroscopy, showed increasing concentration of radicals and carboxylic groups (-COOH) with increasing irradiation dose. The morphological variations of the PTFE nanopowder including its decreasing mean agglomerate size with the absorbed dose was investigated by particle size and scanning electron microscopy (SEM) analysis. With increasing absorbed dose the wettability of the modified PTFE nanopowder determined by contact angle method increased in accordance with the (-COOH) concentration. Transmission electron microscopy (TEM) showed that modified PTFE nanopowder is obviously enwrapped by EPDM. This leads to a characteristic compatible interphase around the modified PTFE. Crystallization studies by differential scanning calorimetry (DSC) also revealed the existence of a compatible interphase in the modified PTFE coupled EPDM. Vol.2, No.4 (2008) [284][285][286][287][288][289][290][291][292][293] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2008.34 powder was specially utilized in NBR to expand its utility as wear-resistant material for sealing applications [25]. PTFE micropowders produced by emulsion polymerization are low-molecular weight fine coagulated powder commonly used as an additive in variety of applications [26][27]. In the previous study, PTFE coupled EPDM compounds were produced by reactive mixing of pre-modified PTFE nanopowder with EPDM [28]. In the present work the influence of dose-controlled agglomerate size, structural morphology and interfacial compatibility of PTFE nanopowder on the physical properties of the resulting modified PTFE-EPDM blends are presented. These investigations are of extreme importance especially in the development of new rubber compounds which require optimization of both the physical and tribological properties [29][30]. It has been shown that the desired physical properties can be achieved simply by controlled modification of PTFE nanopowder. Keywords: mechanical properties, PTFE nanopowder, EPDM, electron beam irradiation, compatibility eXPRESS Polymer Letters Materials and experimental MaterialsBoth EPDM (Buna EP G 6850) with ethylidene norbornene (ENB) content 7.7 wt%; ethylene content 51 wt%; Mooney viscosity, ML (1+4) at 125°C, 60; ash content 0.2 wt%; specific gravity, 0.86; and peroxide (Perkadox 14-40 MB GR) were supplied from Lanxess Deutschland GmbH, Germany while coagent (R-20S/Saret 634C) was used from Sartomer, USA. Algoflon L100X an emulsion grade received from Solvay Solexis S.p.A, Italy is an agglomerated white PTFE nanopowder with the bulk density and surface area of 0.25-0.44 g·cm -3 and 26 g·m -2 , respectively. Modification of...

“…With respect to dry or lubricated conditions of polymer sliding, the principles of some commonly used material families have been tested, and the role of adhesion and surface energy has been discussed [13,14]. There have been initiatives to find the correlation between the wear behaviour and the mechanical properties of polymers, but difficult or weak correlations have been found, primarily because of the limited condition of the wear systems and the selected material families [15][16][17][18]. In recent years, research has focused on the surface-modified engineering polymers and nano-composites because of new technology that enhances the tribological behaviour by changing the molecular or matrix structure to change the surface or bulk properties [19][20][21].…”

mentioning

confidence: 99%

An engineering approach to dry friction behaviour of numerous engineering plastics with respect to the mechanical properties

Kalácska¹

2013

The effect of friction on the wear of engineering polymers is a complex and intricate consequence of the micro-and macroscopic interactions of surfaces moving against one another. Friction and the resulting wear are not material properties of plastics; therefore, they cannot be reduced to tabular data of material characteristics that can be found in relevant manuals. Determining friction and the resulting wear involves more complex examination because they are characteristics of a frictional contact system where the effects of the entire system are manifest. Precise knowledge of system conditions is essential to evaluate the friction and resulting wear [1]. These materials have system-dependent tribological behaviour; thus, trends can be defined at a given condition, and the materials can be compared. The system approach is well-known from the literature [2, 199 An engineering approach to dry friction behaviour of numerous engineering plastics with respect to the mechanical properties G. Kalácska Abstract. Twenty-one different commercial-grade engineering polymers, including virgin and composite types, were selected for testing, based on mechanical engineering practices. Three groups were formed according to typical applications: 1) Sliding machine element materials; 2) Mechanically load-carrying machine element materials that are often subjected to friction and wear effects; and 3) Additional two amorphous materials used as chemically resistant materials that have rare sliding load properties. The friction running-in state was tested using a dynamic pin-on-plate test rig. During steady-state friction tests, two pv regimes (0.8 and 2 MPa"ms -1 ) were analysed by a pin-on-disc test system. Based on the measured forces on ground structural steel, surface friction coefficients were calculated and analysed with respect to the mechanical effects of friction. The friction results were evaluated by the measured mechanical properties: yield stress, Shore D hardness, Young's modulus and elongation at the break. The three material groups exhibited different trends in friction with respect to changing mechanical properties. Linear (with varying positive and negative slopes), logarithmic and exponential relationships were observed, and occasionally there were no effects observed. At steady-state friction, the elongation at the break had less effect on the friction coefficients. The dynamic sliding model, which correlates better to real machine element applications, showed that increasing hardness and yield stress decreases friction. During steady-state friction, an increase in pv regime often changed the sign of the linear relationship between the material property and the friction, which agrees with the frictional theory of polymer/steel sliding pairs.