FDM 3D Printing and Soil-Burial-Degradation Behaviors of Residue of Astragalus Particles/Thermoplastic Starch/Poly(lactic acid) Biocomposites

Abstract

Astragalus residue powder (ARP)/thermoplastic starch (TPS)/poly(lactic acid) (PLA) biocomposites were prepared by fused-deposition modeling (FDM) 3D-printing technology for the first time in this paper, and certain physico-mechanical properties and soil-burial-biodegradation behaviors of the biocomposites were investigated. The results showed that after raising the dosage of ARP, the tensile and flexural strengths, the elongation at break and the thermal stability of the sample decreased, while the tensile and flexural moduli increased; after raising the dosage of TPS, the tensile and flexural strengths, the elongation at break and the thermal stability all decreased. Among all of the samples, sample C—which was composed of 11 wt.% ARP, 10 wt.% TPS and 79 wt.% PLA—was the cheapest and also the most easily degraded in water. The soil-degradation-behavior analysis of sample C showed that, after being buried in soil, the surfaces of the samples became grey at first, then darkened, after which the smooth surfaces became rough and certain components were found to detach from the samples. After soil burial for 180 days, there was weight loss of 21.40%, and the flexural strength and modulus, as well as the storage modulus, reduced from 82.1 MPa, 11,922.16 MPa and 2395.3 MPa to 47.6 MPa, 6653.92 MPa and 1476.5 MPa, respectively. Soil burial had little effect on the glass transition, cold crystallization or melting temperatures, while it reduced the crystallinity of the samples. It is concluded that the FDM 3D-printed ARP/TPS/PLA biocomposites are easy to degrade in soil conditions. This study developed a new kind of thoroughly degradable biocomposite for FDM 3D printing.

Innovative Polymer Composites with Natural Fillers Produced by Additive Manufacturing (3D Printing)—A Literature Review

“…By mixing a biodegradable matrix with a biofibre reinforcement, it is practically possible to produce a biocomposite, a fully biodegradable material [19]. Work on biofibre-based PLA composites has shown some advantages such as high processability, high specific elasticity, compostability, high durability, renewability and recyclability [19,78].…”

“…It also has a longer degradation time. Therefore, there is an urgent need to reduce the cost of PLA and improve its degradability [78]. Biofibre reinforced PLA composites have received Wood and lignocellulosic components can also be used as additives and reinforcements in composites [15].…”

Three-Dimensional Printing of Multifunctional Composites: Fabrication, Applications, and Biodegradability Assessment

“…Thermal analysis of the degraded samples revealed interesting results. The thermal stability of the composites improved, which may indicate the rapid degradation of starch and fibers in the soil, increasing the number of PLA crystalline domains in the composite [206]. Hydrophilic additives that can absorb water improve the biodegradability of PLA.…”

Obtaining and Characterizing New Types of Materials Based on Low-Density Polyethylene and Thermoplastic Starch

“…Several studies have shown that, by mixing TPS with other non-biodegradable synthetic polymers, new materials can be obtained with low cost, good mechanical properties, and improved biodegradability in various environmental conditions [15,16]. Thus, several researchers have obtained and characterized mixtures based on TPS with polycaprolactone [17], polybutyrate adipate terephthalate [18,19], polylactide [20,21], polyethylene [22,23], polypropylene [24], etc. Of these, most studies have been performed on plasticized starch and low-density polyethylene (LDPE) mixtures, which can be used in packaging [25] and in other industrial applications [26].…”