Do High Performance Polyamides Beat Hard to Process PEEK?
Channel: General ideas and needs in the field of additive manufacturing
High performance plastic materials, such as PEEK (Polyether ether ketone) and PPS (Polyphenylene sulfide), offer lightweight alternatives for metal part replacement in injection moulding (IM) markets. Due to their fast crystallising and high temperature nature 3D printing articles thereof is challenging, particularly in selective laser sintering (SLS). For instance, PEEK, a material with high heat resilience and tensile strengths of 120-140 MPa, struggles to be processed by SLS, yielding parts of low-isotropy and poor mechanical strength (~70-90 MPa). Such poor SLS processability of materials such as PEEK and PPS can be explained by two factors:
1) The printer: SLS printers cannot reach high enough print temperatures giving poor sintering
2) The material: The fast crystallization speeds cause delamination, curling and warpage
Recent advances in SLS may have provided a means to overcome these challenges that warrant exploration:
Commercial SLS printers can now achieve build temperatures of 280-300°C (e.g. Farsoon ST 252 P, EOS Integra 450 P). Although not high enough for PEEK, other high performance materials such as high temp polyamides (PA6I/T) become of interest. Fast crystallising polyamides, notably PA66 (TM: 266°C), can decrease their crystallisation speeds when blended with amorphous polyamides (TR/G). These compounds enable better processability with minimal impact on properties, but the hydrophilicity of PA66 limits its potential. Polymers of type PA6I/T (based on hexamethyldiamine and aromatic diacids), are interesting candidates for high temperature SLS processability as they are hydrostable, thermally appropriate (TM: 260-320 °C) and can reach IM tensile strengths of 120-260 MPa (depending on reinforcement – e.g. Carbon/Glass). Excitingly, they are also compatible with amorphous polyamides (TR/G) with minimal influence on mechanical performance (in IM).
This project aims to screen two PA6I/T types for their general printability on a Farsoon ST 252 P SLS printer. Based on these results the best candidate will be blended with a compatible amorphous polyamide (e.g. EMS-GRIVORY TR/G grades) to determine if processability by SLS can be improved. The outcome of this research would lay the foundation for implementation projects with both material supplier and end users (e.g. Automotive internal components, Formula 1 exterior parts), specifically where higher heat deflection temperatures and mechanical strengths are paramount.
