A surface modification of polylactic acid composites for additive manufacturing with modified chopped carbon fiber and modified nano‐hydroxyapatite

摘要

Abstract Polylactic acid (PLA) composites parts obtained by fused deposition modeling (FDM) three‐dimensional (3D) printing have obvious fusion interfaces. The printed parts have low strength and poor plastic toughness, limiting their application in clinical degradable load‐bearing implants. In this article, first, the nano‐hydroxyapatite (n‐HA) was modified by PLA to obtain a core‐shell structure with PLA coating. The micron chopped carbon fiber (CF) was modified by nitric acid to obtain a rich oxygen‐containing functional group structure. Second, the above two modified materials of n‐HA and CF were coated on the surface of the PLA filament by ultrasonic impregnation to obtain the PLA/n‐HA/CF composite filament. Finally, tensile samples were manufactured by FDM 3D printing with the PLA/n‐HA/CF composite filament, and the tensile test was conducted. The results show that the surface‐modified n‐HA particles form a regular spherical core‐shell structure with good dispersibility. It can be combined with a matrix of PLA filament by the PLA coating layer, while a silane coupling agent combines the PLA coating layer and the core of n‐HA. The modified chopped CF treated with 68 nitric acid for 6 h has an ideal etch pits with moderate depth and distribution producing firm combination with the PLA matrix. The surface of modified chopped CF has abundant –COOH and –OH functional groups. It can be combined with a matrix of PLA filament through an esterification reaction. Among all the tensile samples, PLA_5 n‐HA_6 CF, with 5 modified n‐HA and 6 modified chopped CF, respectively, improves the bonding strength between the fused interfaces with the two reinforcement materials well‐distributed in the fuse interface area.