Waterproof and Wear-Resistant Surface Treatment on Printed Parts of Polyamide 12 (PA12) by Selective Laser Sintering Using a Large Pulsed Electron Beam

Porosity is an unavoidable problem of products in powder bed fusion-based additive manufacturing. This hinders underwater applications of printed products due to water absorption by capillary force. This study reports the surface treatment of polyamide 12 (PA12) manufactured by selective laser sintering using large pulsed electron beam (LPEB) irradiations as an ecofriendly postprocessing technique. With the optimal conditions of LPEB, the surface roughness and porosity were reduced after the melting and resolidification of unmelted particles and pores without generating any dusts and using any chemicals. The surface roughness reduction increased static contact angle (CA) on the surface. From a chemical wettability investigation, the reduction of hydrophilicity after the LPEB irradiation was obtained and attributed to the elimination of hydrophilic functional groups on the surface. Due to the harmonic effects of roughness and hydrophilicity reduction, the CA on LPEB-treated surfaces was achieved around 95°. The pore-closing effect of LPEB irradiation and hydrophobic transition of PA12 protected the surface from water absorption, eliminating the capillary effect. The waterproof performance on the surface was demonstrated by releasing droplets on the surface and immersing them in ink-dispersed distilled water. The result showed potential applications of rapidly sintered PA12 in underwater.