Journal of Industrial Engineering Research. Tribological Performance of Polymer Composites in Use in Electrical Insulation Applications

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1 IWNEST PUBLISHER Journal of Industrial Engineering Research (ISSN: ) Journal home page: Tribological Performance of Polymer Composites in Use in Electrical Insulation Applications 1 Ahmet Ozel, 2 Abdullah Mimaroglu, 3 Huseyin Unal 1 University of Sakarya, Faculty of Engineering, Esentepe Kampusu, Adapazari, Turkey. 2 University of Sakarya, Faculty of Engineering, Esentepe Kampusu, Adapazari, Turkey. 3 University of Sakarya, Faculty of Technology, Esentepe Kampusu, Adapazari, 54187, Turkey. A R T I C L E I N F O Article history: Received 3 October 2015 Accepted 10 October 2015 Published Online 13 November 2015 Keywords: Tribology, thermoplastics, composites, polyamide A B S T R A C T The present study aims to select the most suitable combination of polymer composite/polymer composite of pair materials in contact with each other in electrical insulating applications and the influences of counterface material and applied load values on the tribological performance of the materials. The materials studied are neat poly-ether-ether-ketone (PEEK), 20% (PEEK+20%SGF), 30%glass fiber reinforced PEEK (PEEK+30%SGF), 30%carbon fiber reinforced PEEK (PEEK+30%CF), 20% glass fiber reinforced poly-tetra-fluoro-ethylene (PTFE+20%SGF), 25% bronze filled poly-tetra-fluoro-ethylene (PTFE+25%bronze), 10%PTFE filled polyamide 66 blend (PA66+10%PTFE), 30%glass fiber reinforced polyamide 66 (PA66+30%SGF) and 30%glass fiber reinforced polyamide 46 (PA46+30%SGF) composites. Friction and wear tests were carried out on a pin-on-disc arrangement at a dry sliding 20, 40 and 60 N loads and 0.5 m/s sliding speed conditions. Tribological tests were performed at. The results showed that, the highest specific wear rate is for PA 46+30%SGF composite with a value of 4.94 x m 2 /N. The lowest wear rate is PTFE+20%SGF composite with a value of 9.03x10-15 m 2 /N. From the point view of tribological performance, PTFE+20%SGF composite against glass fiber reinforced and calcium carbonate filled unsaturated polyester composite counterparts are most suitable combination thermoplastic composite materials for electrical contact breaker applications IWNEST Publisher All rights reserved. To Cite This Article: Ahmet Ozel, Mimaroglu, Huseyin Unal., Tribological Performance of Polymer Composites in Use in Electrical Insulation Applications. J. Ind. Eng. Res., 1(11), 20-24, 2015 INTRODUCTION Unfilled polymers have some disadvantages such as lower mechanical, thermal, tribological properties. Therefore, various reinforcements are frequently added to the unfilled polymers to improve the mechanical, thermal and tribological properties. Polymer based composite materials are preferred for many industrial applications such as automotive, aircraft, electrical/electronic, transportation, sport goods and household applications. These composites are polyether-ether-ketone, polyamide 6, 46 and 66, poly-tetra-fluoro-ethylene with additional fillers such as glass fibre, carbon fibre, graphite and bronze. In fact, a thermoset material consists of unsaturated polyester resin and other additives reinforced with randomly distributed chopped long glass fibre strands. It has evolved into a preferred candidate for the electrical industry, specially, high voltage applications. It offers attractive feature, such as its lower material cost, temperature resistance and dimensional stability. Poly-tetra-fluoro-ethylene is currently finding increasing utility in high performance mechanical seals due to its unique properties like high chemical resistivity, low coefficient of friction and high temperature stability [1,2]. However, poly-tetra-fluoro-ethylene shows poor wear resistance. The wear properties of PTFE can be significantly improved by the addition of suitable filler materials such as glass fibre [3], carbon fibre, graphite [4] and MoS 2 [5]. Tanaka and Kawakami [3] have studied the effect of incorporation of glass fibre and MoS 2 on the tribological performance of poly-tetra-fluoro-ethylene. Poly-ether-ether-ketone engineering polymer has received significant attention in the last couple of the years. Their high strength and modulus, high melting temperature, thermal stability, excellent toughness, easy processing, chemical inertness, wear resistance, make it an ideal material for advanced composites. PEEK also plays a more and more important role as a bearing and a slider material [6-7]. Corresponding Author: Ahmet Ozel, University of Sakarya, Faculty of Engineering, Esentepe Kampusu, Adapazari, Turkey. ozel@sakarya.edu.tr

2 21 Ahmet Ozel et al, 2015 PEEK is promising rubbing materials. So, many studies on the friction and wear of PEEK has been reported [8-10]. The commonly used composites are PEEK, PEEK+20%SGF PEEK+30%SGF, PEEK+30%CF, PTFE+25%bronze, PTFE+20%SGF, PA 66+10%PTFE, PA46+30%SGF and PA66+30%SGF. In addition, in many cases reinforcements such as glass fibre, mineral additives and solid lubricants are added. These additives provide high mechanical, thermal properties, electrical, low friction and low cost. Hutchings [11] and Tewari et al [12] reported that the friction between polymers can be attributed to two main mechanisms which are deformation and adhesion. The deformation mechanism involves a complete dissipation of energy in the contact area. The adhesion component is responsible for the friction of polymer and is a result of breaking of weak bonding forces between polymer chains in the bulk of the material. Researcher [13-14] report that the friction coefficient can be reduced and the wear resistance with polymer sliding against steel improved by selecting the right material combinations. Some of researcher [15] observed that the friction coefficient of polymers rubbing against metals decreases with the increment in load while other researchers [16] showed that its value increases with the increase in load value. Bahadur et al [17] has reported the tribological behaviour of polyamide, HDPE and their composites. They reported that their wear resistance and coefficient of friction is affected greatly by normal load, sliding velocity and temperature. Unal et al. [15] have also reported the sliding wear performance of pure PTFE, carbon, bronze and glass fibre reinforced PTFE composites under dry sliding conditions. They observed that the coefficient of friction is affected greatly by normal load. In this experimental study, the influence of applied load values on the friction and wear behaviour of unfilled poly-ether-ether-ketone, 20% and 30%glass fiber reinforced PEEK, 30%carbon fiber reinforced PEEK, 20% glass fiber reinforced poly-tetra-fluoro-ethylene, 25% bronze filled poly-tetra-fluoro-ethylene, 10%PTFE filled polyamide 66 blend, 30%glass fiber reinforced polyamide 66, and 30%glass fiber reinforced polyamide 46 composite have been studied. Friction and wear tests against long glass fiber reinforced and calcium carbonate filled unsaturated polyester composite counterpart were carried out on a pin on disc arrangement and at dry sliding conditions. Tribological tests were at room temperature, under 20, 40 and 60N loads and at 0.5 m/s sliding speed. Experimental: Measurement of Coefficient of Friction and Wear Resistance: For tribological tests, the 6mm diameter pin materials were moulded by the injection moulding method. 5 mm in thickness discs was moulded by bulk moulding compound. Before wear testing, the pin and the disc surfaces were cleaned with acetone and dried. The schematic pin-on-disc wear test apparatus is shown in Figure 1. As seen in this figure, the apparatus consists of a stainless steel table which is mounted Fig. 1: Schematic diagram of the friction and wear test apparatus on a turntable, a variable speed motor which provide the unidirectional motion to the turntable, so to the disk sample and a pin sample holder which is rigidly attached to a pivoted loading arm. This loading arm is supported in bearing arrangements to allow loads to be applied to the specimen. During the test, friction force was measured by a transducer mounted on the loading arm. The friction force readings were taken as the average of 1500 readings every 60 sec for a period of 33 minute test time. The coefficient of friction (µ) was calculated as follows: µ=f f /F N. The amount of wear was measured by interrupting the sliding test a suitable intervals for weighting the pin to an accuracy of 0,0001 g in a precision balance and converted into volume using the density of the sample. In addition, the specific wear rate (Ws) [m 2 /N] was calculated by:

3 22 Ahmet Ozel et al, 2015 Ws=( m)/(lxρxf N ) Where m the mass loss, ρ the density, F N the normal load and L the sliding distance. Fig. 1: Schematic diagram of the friction and wear test apparatus RESULTS AND DISCUSSIONS It is clear from figure 2 that the mass loss in all polymers and composites used in this investigation increases linearly with the increment of applied load Applied load (N) PA 46+30%SGF PA 66+30%SGF PA 66+10%PTFE PTFE+25%bronze PTFE+20%SGF neat PEEK PEEK+20%SGF PEEK+30%SGF PEEK+30%CF mass loss (g) 0,1 0,01 0,001 0,0001 Fig. 2: Variation of mass loss (log scale) with applied load for PA46+30%SGF, PA66+30%SGF, PA66+10%PTFE, PTFE+25%bronze, PTFE+20%SGF, neat PEEK, PEEK+20%SGF, PEEK+30%SGF and PEEK+30%SCF thermoplastics against unsaturated polyester thermoset composite (sliding speed = 0.5m/s) It is clear from figure 3 that the coefficient of friction decreases linearly with the increment of applied load. It is known that polymers are a visco-elastic materials their deformation under load is viscoelastic. Therefore, for the thermoplastics, the interfacial temperature influences the viscoelastic property in the response of material stress, adhesion and transferring behaviours as well. Hence, the friction heat at the frictional interfaces is proportional to the applied load and sliding velocity. This behaviour and result is in agreement with the results

4 23 Ahmet Ozel et al, 2015 obtained by Bahadur [17]. while the specific wear rate for PA 46+30%SGF is in the order of m 2 /N. The highest specific wear rate is for PA 46+30%SGF with a value of 4.94 x m 2 /N. The lowest wear rate is for PTFE+20%SGF with a value of 9.41x10-15 m 2 /N. The average specific wear rates for both PTFE+20%SGF polymer composite is about 525 times lower than that of PA46+30%SGF. The PA 46 composites showed the highest specific wear rate values. This effect could be explained by the brittleness of the PA 46 matrix and also the higher amount of glass fibres of the PA 46+30%SGF composite. The reason for high wear rates may be explained by the weak bonding between the fibres and the matrix. 1 0,9 0,8 PA 46+30%SGF PA 66+30%SGF PA 66+10%PTFE PTFE+25%bronze PTFE+20%SGF neat PEEK PEEK+20%SGF PEEK+30%SGF PEEK+30%CF Coef f icient of friction** 0,7 0,6 0,5 0,4 0,3 0,2 0, Applied load (N) Fig. 3: Variation of mass loss (log scale) with applied load for PA46+30%SGF, PA66+30%SGF, PA66+10%PTFE, PTFE+25%bronze, PTFE+20%SGF, neat PEEK, PEEK+20%SGF, PEEK+30%SGF and PEEK+30%SCF thermoplastics against unsaturated polyester thermoset composite (sliding speed = 0.5m/s) It is clear from figure 4, the specific wear rate for PTFE+20%SGF is in the order of m 2 /N and the specific wear rate for PEEK polymer, PEEK+20%SGF, PEEK+30%CF, PA66+10%PTFE and PTFE+25%bronze are in the order m 2 /N and the specific wear rate for PA66+30%SGF and PEEK+30%SGF are in the order Conclusions: -It is concluded that generally the coefficient of friction decreases with the increase in applied load values. -The specific wear rate for PTFE+20%SGF is in the order of m 2 /N and the specific wear rate for PA66+10%PTFE, PTFE+25%bronze, PEEK, PEEK+20%SGF and PEEK+20%CF are in the order m 2 /N and the specific wear rate for PA66+30%SGF and PEEK+30%SGF are in the order m 2 /N while the specific wear rate for PA 46+30%SGF is in the order of m 2 /N. - The highest specific wear rate is for PA46+30%SGF with a value of 4.94x10-12 m 2 /N followed by PA66+30%SGF with a value of 2.32 x m 2 /N. - The lowest wear rate is for PTFE+20%SGF with a value of 9.41x10-15 m 2 /N. -Finally the PTFE+20%SGF composite is a convenient engineering thermoplastic for electrical contact breaker applications.

5 24 Ahmet Ozel et al, 2015 Specific wear rate (m 2 /N) 1.0E E E E E N Fig. 4: Variation of specific wear rate with applied load for PA 46+30%SGF, PA66+30%SGF, PA66+10%PTFE, PTFE+25%bronze, PTFE+20%SGF, neat PEEK, PEEK+20%SGF, PEEK+30%SGF and PEEK+30%CF thermoplastics against unsaturated polyester thermoset. REFERENCES [1] Lewis, M.W.J., Lubric. Eng., 42: 152. [2] Blanchet, T.A., F.E. Kennedy, Tribology Trans., 34(3): 327. [3] Tanaka, K., S. Kawakami, Wear, 79(1982): 221. [4] Bijwe, J., C.M. Logani, U.S. Tewari, Wear, 138: 77. [5] Bahadur, S., D. Tabor, Wear, 98: 1. [6] Cogswell, F.N., Butterworth-Heinemann, Oxford. [7] Friedrich (Ed.) K., Composite Materials Series, Elsevier, Amsterdam, 1. [8] Kurokawa, M., Y. Uchiyama, S. Nagai, Tribol. Int. 33: 715. [9] Ovaert., T.C., H.S. Cheng, Wear, 150: 275. [10] Hanchi, J., Jr. N.S Eiss., Tribol. Trans., 38(2): 305. [11] Hutchings, I.M., Tribology Friction and Wear of Engineering Materials, Edward Arnold, London. [12] Tewari, U.S., S.K. Sharma, P.Vasudevan, Rev. Macromolecules Chemical Phys. C 29(1): 1. [13] Hooke, C.J., S.N. Kukureka, P. Liao M, Rao and Y.K.Chen, Wear, 200: 83. [14] Lawrence, C.C. and T.A. Stolarski, Wear, 132: 83. [15] Unal, H., A. Mimaroglu, Materials&Design, 24: 183. [16] Unal, H., A. Mimaroglu, J. Industrial, Lubrication and Tribol., 55(4): 178. [17] Bahadur, S. and D. Tabor, Role of fillers in the friction and wear behaviour of high-density polyethylene in: LH.Lee (Ed), Polymer Wear and its control, ACS Symposium Seri