Additive Manufacturing of Polyetherketoneketone (Pekk): Enhancing 3d-Printed Part Performance Through Optimized Crystallization Protocol

Abstract

Material extrusion (ME) of semi-crystalline polymer with fast crystallization kinetics is a challenge in additive manufacturing of high-performance thermoplastics. As a result, polymers with slower crystallization kinetics such as Amorphous Polyetherketoneketone (A-PEKK) are preferred with a final product in an amorphous state. However, a post-processing heat treatment is required to enhance the mechanical performance of the 3D-printed part through a cold crystallization process. This study aims to establish a pathway for improving the performance of PEKK parts produced via fusion deposition modeling (FDM) in a minimum amount of time at the lowest applicable temperature to reach maximum crystallization. A method based on standard tests was used to optimize crystallization by simulating annealing conditions using differential scanning calorimetry (DSC) and finite element analysis (FEA) of the sample during annealing. After addressing manufacturing challenges, regular and annealed samples were compared through mechanical testing and thermomechanical analysis to assess the effects of optimized annealing. By applying a simulated annealing process at the optimal temperature and minimum time, tensile strength increased by 29.5% and flexural strength by 17.3%. The relative crystallinity rose by 7.2% after the FDM process and 27.3% in total after optimized annealing. Additionally, dynamic mechanical analysis (DMA) revealed a 51.4°C increase in the heat deflection temperature. Through this methodology, one can have the ease of manufacturing of amorphous thermoplastic like Polyetherimide (PEI) while having high mechanical performance such as Polyetheretherketone (PEEK), making it a competent material for aerospace applications.

Keywords: PEKK, Fused Deposition Modeling, Annealing, Optimization, manufacturing