Poly(ether ether ketone)-bischromenes: Synthesis, characterization, and influence on thermal, mechanical, and thermo mechanical properties of epoxy resin

Poly(ether ether ketone) s with terminal propargyl groups (PEEK-PR) were synthesized from hydroxyl terminated PEEK (PEEKTOH) and characterized. The heat-triggered polymerization of PEEK-PR to poly bischromenes having PEEK backbone was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetric studies. PEEK-PR was blended with a bisphenol based epoxy resin-diamino diphenylsulphone system in different proportions and cured to form PEEK-bischromene-interpenetrated-epoxy-amine networks. Tensile strength and elongation of the cured blends increased up to 10-phr loading of PEEK-PR and then declined. Tensile moduli of all formulations were comparable. Fracture toughness increased by a maximum of 33%, and the fractured surface morphology showed a ductile fracture. The blends exhibited slightly lower glass transition temperature to that of the neat epoxy-amine system. A reference sample of epoxy-amine was processed with the optimum loading of the precursor polymer, PEEKTOH, and compared its properties with the PEEK-PR incorporated epoxy systems. In this way, it is found that the incorporation of addition curable propargylated PEEK increases the strength characteristics with adequate thermal stability and fracture toughness for high-performance structural applications.