Strain rate sensitivity metrics of PSU and PPSU high-performance polymers in extrusion-based additive manufacturing

• High performance polymers Polysulfone (PSU) and Polyphenylsulfone (PPSU) in material extrusion (MEX) 3D printing • Mechanical performance under tensile loading with 10 to 300 mm/min uniaxial elongation speeds • Both PSU and PPSU exhibit remarkable strain rate sensitivity. • PSU strength decreased at high strain rates, while PPSU increased up to 100mm/min and decreased at higher strain rate. • Parts become more brittle with the increase of the strain rate. High-performance polymers (HPPs), combined with material extrusion (MEX) additive manufacturing (AM), compile a powerful manufacturing system, suitable to meet the challenges of demanding industries. Their ability to undergo high strain rates is not well investigated yet. Herein, two HPPs, i.e., Polysulfone (PSU) and Polyphenylsulfone (PPSU) were engaged to produce filaments, and a large amount of MEX AM fabricated specimens were examined under tensile tests with variable strain rate conditions. The aim was to thoroughly investigate the effect of strain rate (10 to 300 mm/min uniaxial elongation speeds) on the mechanical properties of these two high-performance polymers, considering the 3D printing structure on their response. Τheir yield, strength, modulus, and toughness were evaluated. Besides the thermal evaluation of the filaments, the samples were examined through scanning electron microscopy to document and identify their failure patterns. The findings indicate that both PSU and PPSU exhibit remarkable strain rate sensitivity. For the PSU polymer, the tensile strength decreased by almost 35% (∼20% Young’s modulus) at the highest test speed. For the PPSU, the respective value was ∼16%, at 100mm/min and then decreased at higher strain rates. Young’s modulus increased by almost 30% at 200mm/min and then decreased by almost 20%. The enhanced molecular structure and thermal stability of PPSU enable it to surpass PSU in performance at high strain rates. Samples become more brittle with the increase of the strain rate. These results underscore the necessity for judicious material selection in the 3D printing process when designing components intended for high loading speeds.