Green Processing of Neat Poly(lactic acid) Using Carbon Dioxide under Elevated Pressure for Preparation of Advanced Materials: A Review (2012–2022)

Abstract

This review provides a concise overview of up-to-date developments in the processing of neat poly(lactic acid) (PLA), improvement in its properties, and preparation of advanced materials using a green medium (CO2 under elevated pressure). Pressurized CO2 in the dense and supercritical state is a superior alternative medium to organic solvents, as it is easily available, fully recyclable, has easily tunable properties, and can be completely removed from the final material without post-processing steps. This review summarizes the state of the art on PLA drying, impregnation, foaming, and particle generation by the employment of dense and supercritical CO2 for the development of new materials. An analysis of the effect of processing methods on the final material properties was focused on neat PLA and PLA with an addition of natural bioactive components. It was demonstrated that CO2-assisted processes enable the control of PLA properties, reduce operating times, and require less energy compared to conventional ones. The described environmentally friendly processing techniques and the versatility of PLA were employed for the preparation of foams, aerogels, scaffolds, microparticles, and nanoparticles, as well as bioactive materials. These PLA-based materials can find application in tissue engineering, drug delivery, active food packaging, compostable packaging, wastewater treatment, or thermal insulation, among others.

Characterization of Biodegradable Polymers for Porous Structure: Further Steps toward Sustainable Plastics

“…Conversely, PHBV exhibits interconnected open pores with thicker walls, as demonstrated in other studies that utilized alternative approaches to achieve controlled foam structures [ 74 ]. PLA reveals small, closed pores with a combination of both thin and thick walls, which aligns with observations reported in other studies on PLA foams [ 75 ]. These variations in morphological features highlight the material-specific responses during the fabrication process using carbon dioxide as a foaming agent.…”

Incorporation of canola meal as a sustainable natural filler in PLA foams

“…The CO 2 was chosen as a gas for impregnation because it is non-toxic, non-flammable, acts as a plasticizer, is available in high purity, and has a good solubility of PLA compared to N 2 (Villamil Jiménez et al 2024 ). Further, CO 2 is a green solvent that can be completely removed at ambient conditions from the foam (Milovanovic et al 2023 ). Typically, at the start of the impregnation around 22 wt% of CO 2 was absorbed by all formulations except sample # 2.1 (Fig.…”

“…The dissolved CO 2 molecules increase the intermolecular distance causing PLA polymer to swell, increasing specific volume, and decreasing the overall density of all pre-foamed PLA formulations (Milovanovic et al 2023 ). After 3 s of pre-foaming, the densities were in the range of 110–150 g/L, and after 30 s densities reached lower than 50 g/L (Fig.…”

Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives

“…Several additives can be added to PLA to improve the flame retardancy properties of PLA foams and broaden its fields of application [233][234][235][236]. Milovanovic et al [237] published a concise overview of the main developments in the processing of neat PLA using CO 2 under elevated temperatures that covers the last decade. Table 1 shows some usages of PLA in foaming processing.…”