Preparation Of Nanocellular: Poly(aryl Ether Ketone) Foam

In recent years, polymeric nanoporous materials have been the new frontier forpolymer foams. Their unique cell structure brings them excellent low dielectricproperties, thermal insulation properties, and better mechanical properties comparedwith traditional foam. Among the method used to produce these materials, supercriticalfoaming remains the most attractive one. Poly(aryl ether ketone)s(PAEKs) are a classof important high-performance aromatic polymers with excellent mechanical properties,good solvent resistance, size-accuracy, electrical characteristics, and superior thermalstability, which possess some potential applications in aerospace, automobile,electronics, and other high technology fields. It`s significant to develop nanocellularPAEK foam.The key in the preparation of nano-porous material is to reduce pore size andimprove cell density. Crosslinking is a feasible method to limit cell growth thus controlcell size, however the specific influence of cross-linking on the foaming process hasyet to be studied. In this paper, we successfully produced nanocellular poly(aryl etherketone) by controlling the crosslinking degree. Firstly, PAEK with naphthalene on theside chains was prepared and followed by crosslinking at different temperatures，namely PAEK films with different crosslinking degree were successfully produced. Gasadsorption tests show the increase of crosslinking degree is adversely to the adsorptionof carbon dioxide, while increasing the saturation pressure and extending the saturationtime is favor for the adsorption of carbon dioxide. Secondly, the influences ofcrosslinking degree and other foaming conditions on the foam morphology areinvestigated, the nucleating theory of crosslinking materials is systematically studied.It was first discovered that the stored elastic energy in the system (SE) during nucleationcannot be neglected for a highly viscoelastic polymer matrix, and it is a key factorinfluencing the nucleation rate and foam morphology. Experiments showed that theslight increase of crosslinking degree decreased the cell size and amplified the cell density because it successfully suppressed the cell coalescence. However, furtherincrease of crosslinking degree increased the cell size and lowered the cell densitybecause of the decrease of nucleation rate. By controlling the crosslinking degree andoptimising the processing parameters, nanocellular foam with a cell size of86nm(±11nm) was successfully prepared.