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Unformatted text preview: Epoxy, ZnO, and PTFE nanocomposite: friction and wear optimization N.L. McCook, B. Boesl, D.L. Burris and W.G. Sawyer* Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL , 32611, USA Received 6 February 2006; accepted 9 June 2006 To lower the friction coecient and increase the wear resistance of epoxy, nanoparticles of zinc oxide and polytetrauoro- ethylene (PTFE) were added in small volume percents to an epoxy matrix. Tribological testing of the samples in this study was completed on a linear reciprocating tribometer with a 250 N normal load and a 50.8 mm/s sliding speed. Several samples were made and tested following a modified Simplex Method optimization procedure in order to find a volume percent for optimized wear resistance and friction coecient. The sample with the optimum wear rate consisted of 1 volume percent of zinc oxide nanoparticles and 14.5 volume percent of PTFE nanoparticles. It had a wear rate of k = 1.79 10 ) 7 mm 3 /Nm; 400 more wear resistant than neat epoxy. The sample with the optimum friction coecient consisted of 3.5 volume percent of zinc oxide nanoparticles and 14.5 volume percent of PTFE nanoparticles and had a friction coecient of l = 0.113, which is almost a 7 decrease in friction coecient from neat epoxy. KEY WORDS: PTFE, epoxy, zinc oxide, nanocomposites, optimization, Simplex Method, wear rate, friction coecient 1. Introduction Epoxy alone has a high friction coecient in most applications, as well as poor wear resistance compared to epoxy containing composites. Fillers have been added to reduce both friction coecient and wear rate. Studies with epoxy and micron-scale fillers by Burroughs et al . , Zhang et al . , and Chang et al . , show a monotonic reduction in wear rate with increased filler loading up to 30 volume percent (vol%). Nanoscale fillers such as, TiO 2 [2,3], SiO 2 , Al 2 O 3 [5,6], and Si 3 N 4  have also been shown to reduce friction and wear in epoxy matrix composites. Chang et al .  used TiO 2 , polytetrauoroethylene (PTFE), short carbon fiber, and graphite as fillers in an epoxy matrix, and was able to decrease the friction coecient to l = 0.35 and decrease the wear rate 10 with 10 vol% TiO 2 . Shi et al .  saw a 0.4 decrease in friction coecient, from l = 0.58 to l = 0.35, and 10 decrease in wear resis- tance with the addition of 2.0 vol% nanoscale Al 2 O 3 to epoxy, and Wetzel et al .  saw a 2 decrease in wear resistance with the addition of small amounts of nano- Al 2 O 3 . Shi et al .  also saw decreases in friction coef- ficient, from l = 0.7 to l = 0.32 with the addition of up to 2.25 vol% of nano-Si 3 N 4 ....
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