Wetting dynamics and adhesion of polyether ether ketone

Better understanding of how thermoplastics like polyether ether ketone (PEEK) spread on fiber surfaces within a composite, or themselves during fused filament fabrication is crucial for high-quality part production. Yet, due to its high melting temperature, the properties of molten PEEK have been rarely investigated. In this study, the viscosity, surface tension, and spreading dynamic behavior of molten PEEK on different substrates (glass, silicon wafer, and steel) were systematically explored. The analysis of the contact angle dynamics showed that both the classical hydrodynamics approach (HD) and molecular-kinetic theory (MKT) could model the experimental data satisfactorily. The relative contribution of the viscosity, as depicted by the MKT, to the energy dissipation process was found to dominate the contact-line friction contribution. In addition, a good agreement was found when calculating the physical work of adhesion between PEEK and the substrates in three different ways: at high temperatures (molten state), at room temperature (solid state), and using a combination of both states. This is a promising result indicating that the bonding ability of PEEK during processing could be predicted by characterizing its surface properties in the solid state.