3D-printed wood-polylactic acid-thermoplastic starch composites: performance features in relation to biodegradation treatment

Authors: LEE, DANBEE - Louisiana State University Agcenter; SUN, YUFENG - Louisiana State University Agcenter; YOUE, WON-JAE - National Institute Of Forest Science; GWON, JAEGYOUNG - National Institute Of Forest Science; Cheng, Huai; WU, QINGLIN - Louisiana State University Agcenter

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2021
Publication Date: 6/12/2021
Citation: Lee, D., Sun, Y., Youe, W.-J., Gwon, J., Cheng, H.N., Wu, Q. 2021. 3D-printed wood-polylactic acid-thermoplastic starch composites: Performance features in relation to biodegradation treatment. Journal of Applied Polymer Science. 138(36):50914. https://doi.org/10.1002/app.50914.
DOI: https://doi.org/10.1002/app.50914

Interpretive Summary: 3D printing is becoming an important manufacturing technology, whereby a polymer item is produced layer by layer using a printer, and the layers are then stacked together. Most of the polymers involved with this technology are based on polyacrylates and other synthetic polymers, but biobased polymers, like poly(lactic acid) (PLA), are sometimes used. With increasing public awareness of the danger of microplastics, the biodegradability of these 3D-printed polymers is an issue of concern. In this work, the composites comprising PLA, wood fillers, and thermoplastic starch were used to produce 3D-printed composite filaments. They were then subjected to soil-burial biodegradation treatment. PLA by itself did not biodegrade, but the addition of wood and starch in the composites helped to improve biodegradation. Thus, the addition of wood and starch fillers to PLA is a viable approach to reduce the plastic disposal problem resulting from PLA-based 3D-printed products.

Technical Abstract: In view of the current public concern about microplastics, the biodegradability of 3D printed materials is an important issue. In this work, we studied the effects of soil-burial biodegradation treatment on poly(lactic acid) (PLA)-wood blends with and without thermoplastic starch (TPS) addition. The composites of PLA/wood and TPS were produced and 3D-printed through the fused deposition modeling technique. The analyses studied before and after biodegradation included composite modulus and strength, structure determination, thermal stability, crystallinity, and weight-loss. The TPS addition at 10 and 20 wt% levels to PLA-wood composites led to reduced mechanical and thermal properties compared with those of the original PLA-wood composite. The degradation of the composites was clearly observed from microstructural images of the composites with TPS after the soil-burial test. FTIR data showed prominent characteristic peaks associated with PLA in the composites. The biodegradation treatment decomposed TPS and wood and promoted the degradation of the overall composites (as shown by the reduced sample weights at higher TPS levels). With increasing biodegradation, the treated composites showed increased thermal decomposition temperature, activation energy, and degree of crystallinity due to the increased PLA content in the test samples. Thus, whereas PLA itself was not biodegradable, the addition of TPS and wood fillers to PLA helped improve biodegradation and may be a useful approach to produce more eco-friendly 3D-printed PLA composites.