Semi-crystalline thermoplastic polymers from polyaryletherketones family such as polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) as well as thermoplastic polyimides (TPI) are known for their outstanding mechanical properties (with Young’s modulus approx. 4.0 GPa), high melting points and low flammability. Furthermore, they show a high resistance to most of the common solvents but at temperatures above the glass transition temperature, these polymers can be dissolved in high boiling point aprotic solvents. However, these polymers, especially PEKK and PEEK, are intrinsically difficult to foam, because of the low melting strength. Commonly, porous PEKK and PEEK are produced by gas blowing or use of porogens like sodium chloride to create porous structure. These processes have some disadvantages like high energy consumption. Furthermore the resulting materials have an inhomogeneous close-cells structure and a porosity of only 50-60%.<br/>The question is how we can push more air into them?<br/>Thermally induced phase separation (TIPS) of polymer solutions at low temperatures is a common method to produced polymer foams. However, so far it has not been adopted for manufacturing monolithic PEEK, PEKK and TPI foams. Here we present our first high porosity PEEK, PEKK and TPI foams obtained by a modifidy TIPS process, which is based on the temperature dependence solubility of PEEK, PEKK and TPI in specific aprotic high boiling point solvents like diphenylketone. After dissolving various amount of polymer, we adjust the morphology of the resulting PEEK, PEKK and TPI foams by changing process parameters like the cooling rate; homogeneous networks of highly interconnected pores (Fig. 1) with pore sizes of approx. 1-3 µm have been achieved. Most importantly, however, for the first time, we have been able to produce mechanically strong, macroporous PEEK, PEKK and TPI monoliths with porosities of up to 90%.

High performance polymer foams: How to push lots of air into PEEK, PEKK and TPI

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.