Effects of contact pressure, molecular weight, and supplier on the wear behavior and transfer film of polyetheretherketone (PEEK)

Abstract

<p><a href="https://www.sciencedirect.com/topics/engineering/polyetheretherketones" title="Learn more about Polyetheretherketones">Polyetheretherketone</a> (PEEK) is a designation given to materials of the polyaryletherketone family having a characteristic distribution of ether and <a href="https://www.sciencedirect.com/topics/chemical-engineering/ketone" title="Learn more about Ketone">ketone</a> groups in the <a href="https://www.sciencedirect.com/topics/engineering/polymer-backbone" title="Learn more about Polymer Backbone">polymer backbone</a>. PEEK materials have high strength and chemical resistance as well as very <a href="https://www.sciencedirect.com/topics/engineering/high-melting-point" title="Learn more about High Melting Point">high melting points</a> and glass <a href="https://www.sciencedirect.com/topics/engineering/transition-temperature" title="Learn more about Transition Temperature">transition temperatures</a>. Because of this combination of properties, PEEK materials find use for wear application in <a href="https://www.sciencedirect.com/topics/engineering/extreme-environment" title="Learn more about Extreme Environment">extreme environments</a> where they provide a light-weight and corrosion resistant <a href="https://www.sciencedirect.com/topics/engineering/bearing-material" title="Learn more about Bearing Material">bearing material</a> that often does not <a href="https://www.sciencedirect.com/topics/engineering/require-lubrication" title="Learn more about Require Lubrication">require lubrication</a>. This study focused on determining the effects of supplier and molecular weight on the wear of particular PEEK materials, in addition to the effect of <a href="https://www.sciencedirect.com/topics/engineering/contact-pressure" title="Learn more about Contact Pressure">contact pressure</a>. Multidirectional <a href="https://www.sciencedirect.com/topics/materials-science/wear-testing" title="Learn more about Wear Testing">wear testing</a>was performed on four PEEK materials. The materials were obtained from two different suppliers, and two molecular weights were chosen for each supplier. Extensive analysis of transfer films produced during wear testing was performed using <a href="https://www.sciencedirect.com/topics/engineering/optical-microscopy" title="Learn more about optical microscopy">optical microscopy</a>. White light <a href="https://www.sciencedirect.com/topics/chemical-engineering/profilometry" title="Learn more about Profilometry">profilometry</a> was used to measure transfer <a href="https://www.sciencedirect.com/topics/materials-science/film-thickness" title="Learn more about Film Thickness">film thickness</a> in order to calculate a mean film thickness for given experimental conditions. <a href="https://www.sciencedirect.com/topics/engineering/dynamic-mechanical-analysis" title="Learn more about dynamic mechanical analysis">Dynamic mechanical analysis</a>, as well as <a href="https://www.sciencedirect.com/topics/engineering/gel-permeation-chromatography" title="Learn more about Gel Permeation Chromatography">gel permeation chromatography</a> and <a href="https://www.sciencedirect.com/topics/engineering/differential-scanning-calorimetry" title="Learn more about differential scanning calorimetry">differential scanning calorimetry</a> were used to characterize each material's <a href="https://www.sciencedirect.com/topics/engineering/viscoelastic-behavior" title="Learn more about Viscoelastic Behavior">viscoelastic behavior</a>, molecular weight, and <a href="https://www.sciencedirect.com/topics/engineering/crystallinity" title="Learn more about Crystallinity">crystallinity</a>, respectively. It was found that the wear of PEEK materials was significantly affected by both contact pressure and molecular weight, but not by supplier. However, an interaction was observed that showed the low molecular weight material from one of the suppliers was more vulnerable to wear at high contact pressures than the other three materials. Results of transfer film analysis showed that film thickness was greatest in locations where pin sliding direction was perpendicular to the <a href="https://www.sciencedirect.com/topics/engineering/counterface" title="Learn more about Counterface">counterface</a> roughness direction, but that mean transfer film thickness did not <a href="https://www.sciencedirect.com/topics/engineering/correlate" title="Learn more about Correlate">correlate</a> to wear amounts. This work is significant because it highlights the fact that tribologically relevant polymers, such as PEEK materials, vary greatly in terms of their <a href="https://www.sciencedirect.com/topics/materials-science/polymers-processing" title="Learn more about Polymers Processing">polymer morphology and processing</a> history, and this variation must be recognized by investigators when reporting wear data.</p>