Wetting and friction behavior of chemically bonded PA‐PTFE‐oil compounds

Abstract

Polyamide (PA), polytetrafluoroethylene (PTFE), and olefinic oils are incompatible. High‐energy radiation in the presence of oxygen can break the PTFE chain, generating hydrophilic functional groups (COF, COOH) and peroxy‐radicals. Based on the functional groups and radicals, it is possible to establish a chemical bond between PA and PTFE as well as between PTFE and olefinic oil molecules. This study prepared PA‐PTFE‐oil‐cb compounds (cb: chemically bonded) by reactive extrusion. The compounds wetting behavior are analyzed by contact angle measurement. Additionally, the sliding properties of the compound are investigated by micro friction testing against stainless steel. Due to good fragmentation and dispersion of PTFE in PA12 matrix, the PA12‐MP1100‐cb and PA12‐MP1100‐MO‐cb compounds show a slight change in wetting behavior compared to virgin PA12. In contrast, the wetting behavior of compounds based on PA46 increases dramatically compared to virgin PA46. Moreover, due to the chemical bonding, the PA‐PTFE‐cb compound surface is significantly smoother than a physical blend used as a model compound. Similarly, the compounds based on PA12 and PA66‐matrix show improved tribological properties compared to PA46‐based compounds. COF values for PA66 and PA12‐Z7321 are 0.69 and 0.55, respectively. In comparison, PA66‐MP1100‐MO‐cb and PA12‐MP1100‐MO‐cb (Z7321) have COF value of 0.34 and 0.38, respectively.