3D printing of continuous cotton thread reinforced poly (lactic acid).

This paper purposed to prepare poly (lactic acid)/continuous cotton thread (PLA /CCT) filaments by using prepreg method, and investigated the properties of PLA/CCT filament and their 3D printed composites. Firstly, a prepreg device was home-made to immerse CCT with PLA melts. The effects of the dragging speed and tensioning equipment on the quality of PLA/CCT filament was investigated. The functions of the immersion temperature, diameter of CCT and alkali treatment of CCT to the tensile properties of PLA/CCT filament were inspected. The results showed that when the dragging speed was 12 r/min, the diameter of the PLA/CCT filament equaled to the standard 3D printed diameter (1.75 mm). Increasing the CCT diameter from 0.6 to 1.0 mm, the tensile strength was improved from 44.26 to 52.81 MPa. The alkali treatment reduced the contact angle of PLA dramatically, and further improved the interfacial compatibility between PLA and CCT, and enhanced the tensile properties of filament composites. Secondly, for achieving CCT without any cutting during the 3D printing, an un-cutting off route was planned. Taguchi experiment was used to investigate how the 3D printing processing parameters affect the flexural properties of the 3D printed PLA/CCT composites. Meanwhile, the impact properties of the 3D printed PLA/CCT composites were analyzed. The results showed that the flexural strength and strain of PLA were improved to 135 MPa and 4.39% with 3D parameters (210℃ of nozzle temperature and 6 mm/s of printing speed). The impact strength of PLA was enhanced dramatically by 5.5% times from 2.75 to 18.87 J/mm. Finally, a thermal experiment was carried out and the results showed that PLA did not degrade during the processing and its molecular structure stayed the same at various states. The results of this paper demonstrated that the natural fiber CCT can be used to enforce PLA and lower the cost of PLA, and the PLA/CCT composites have the potential to be applied in fields of 3D printing of light-weight parts.