Influence of pearlescent pigments on mechanical properties and crystallization behavior of polylactic acid

Lipase etching effects-induced interaction between betanin nanocomplexes and polylactic acid and its 3D printing for food packaging

Etching effects by lipase on polylactic acid (PLA) could induce the exposure of active sites and promote the attachment of betanin nanocomplexes (BR-Ch) to obtain red color. 3D printing, regarded as emerging, innovative packaging fabrication technique, was applied to potentially develop creative, red PLA products for food application. BR-Ch was prepared based on betanin and nano chitin via electrostatic interaction and hydrogen bonding, obtaining nanocomplexes with excellent thermal stability. Pre-treatments mattered greatly in PLA functionalization, and especially, lipase pre-treatment 30 min promoted BR-Ch modification on PLA. Final PLA exhibited excellent red color characteristics (CIElab, Hue-Saturation-Brightness, K/S and CMYK), elongation at break and stable thermal resistance, ultimately achieving outstanding dyeing effect. This work indicates that BR-Ch can potentially replace synthetic pigments to functionalize lipase-pretreated PLA, and the dyed PLA demonstrate the excellent packaging application prospects in food field by 3D-printed products.

Recycling of waste crab shells into reinforced poly (lactic acid) biocomposites for 3D printing

To promote natural waste resource utilization, a novel biocomposite, composed of waste crab shells and poly (lactic acid) matrix, was developed by combining chemical treatment and 3D printing. A crab shell powder (ISCSP) with an abundant porous structure and a high specific surface area was obtained by treatment with hydrochloric acid and sodium hydroxide. Importantly, under the optimal printing parameters determined by the finite element analysis, test samples, and porous bones were successfully printed using CSP/PLA composites by a commercial fused deposition modeling (FDM) 3D printer. The morphology, mechanical and thermal properties, antibacterial properties, and biocompatibility of the CSP/PLA composites were then assessed. Our results revealed that the tensile strength and flexural strength of the ISCSP/PLA composites reached 58.71 and 90.11 MPa, which were 28.6 % and 28.8 % higher than that of pure PLA, respectively. The glass transition and melting temperatures of the composites remained similar to those of pure PLA. Interestingly, the addition of CSP increased PLA crystallinity, which could be attributed to the nucleation effect of CSP in the system. The antibacterial activity of the PLA-1.5ESCSP composite samples against Escherichia coli (E. coli) was greater than 99 %. More importantly, the live/dead assay showed that the CSP/PLA composites possessed excellent biocompatibility. Therefore, the developed CSP/PLA biocomposites are potential feedstocks for 3D printing in bone tissue engineering and may be used as graft substitutes in reparative and reconstructive surgery. They are especially beneficial due to their superior mechanical and thermal properties, excellent antibacterial activities, and significant biocompatibility.