PTFE-modified waterborne copolyester composite coating with a soft–hard structure for enhanced wear resistance in photovoltaic backsheets

In this study, a polytetrafluoroethylene (PTFE)-modified waterborne copolyester composite coating was developed by uniformly incorporating PTFE into an environmentally friendly waterborne copolyester matrix. The waterborne copolyester offers distinct eco-friendly advantages, along with excellent adhesion to PET substrates and high flexibility, making it particularly suitable for photovoltaic module backsheets. The microstructure, tribological properties, and environmental service reliability of the resulting coating were systematically investigated. The PTFE effectively reduced the coefficient of friction between the coating and the counterpart ball and promoted the formation of a stable transfer film, thereby enabling a continuous reduction in wear. Compared with the pure waterborne copolyester coating, the wear rate of the PTFE-modified coating decreased by 19.1%. This enhanced tribological performance is attributed to a continuous film-forming network established by PTFE within the waterborne copolyester matrix. Furthermore, PTFE synergistically reinforced the matrix, generating a “soft–hard” composite structure. At the optimal 10% PTFE content, the soft and hard phases were uniformly distributed, delivering the greatest friction reduction and wear resistance. Combining the intrinsic environmental benefits, strong PET adhesion, and high flexibility of the waterborne copolyester, this approach provides a promising new strategy for developing high-performance wear-resistant coatings for photovoltaic module backsheets.