Mechanical, chemical, and bio-recycling of biodegradable plastics: A review

The extensive use of petroleum-based non-biodegradable plastics for various applications has led to global concerns regarding the severe environmental issues associated with them. However, biodegradable plastics are emerging as green alternatives to petroleum-based non-biodegradable plastics. Biodegradable plastics, which include bio-based and petroleum-based biodegradable polymers, exhibit advantageous properties such as renewability, biocompatibility, and non-toxicity. Furthermore, certain biodegradable plastics are compatible with existing recycling streams intended for conventional plastics and are biodegradable in controlled and/or predicted environments. Recycling biodegradable plastics before their end-of-life (EOL) degradation further enhances their sustainability and reduces their carbon footprint. Since the production of biodegradable plastic is increasing and these materials will coexist with conventional plastics for many years to come, it is essential to identify the optimal recycling options for each of the most prevalent biodegradable plastics. The substitution of virgin biodegradable plastics by their recyclates leads to higher savings in the primary energy demand and reduces global warming impact. This review covers the current state of the mechanical, chemical, and bio-recycling of post-industrial and post-consumer waste of biodegradable plastics and their related composites. The effects of recycling on the chemical structure and thermomechanical properties of biodegradable plastics are also reported. Additionally, the improvement of biodegradable plastics by blending them with other polymers and nanoparticles is comprehensively discussed. Finally, the status of bioplastic usage, life cycle assessment, EOL management, bioplastic market, and the challenges associated with the recyclability of biodegradable plastics are addressed. This review gives comprehensive insights into the recycling processes that may be employed for the recycling of biodegradable plastics.

Modelling and Scaling-Up of a Supercritical Fluid Extraction of Emulsions Process

Supercritical CO2 (scCO2) is utilized in the supercritical fluid extraction of emulsions (SFEE) to swiftly extract the organic phase (O) from an O/W emulsion. The dissolved substances in the organic phase precipitate into small particles and remain suspended in the water (W) with the aid of a surfactant. The process can be continuously conducted using a packed column in a counter-current flow of the emulsion and scCO2, at moderate pressure (8–10 MPa) and temperature (37–40 °C). To ensure the commercial viability of this technique, the organic solvent must be separated from the CO2 to facilitate the recirculation of both streams within the process while minimizing environmental impact. Thus, the aim of this work was to design a plant to produce submicron materials using SFEE, integrating the recovery of both solvents. First, experimental equilibrium data of the ternary system involved (CO2/ethyl acetate/water) were fitted with a proper thermodynamic model. Then, simulations of the whole integrated process at different scales were carried out using Aspen Plus®, along with economical evaluations. This work proposes the organic solvent separation with a distillation column. Thus, the two solvents can be recovered and recycled to the process in almost their entirety. Furthermore, the particles in the aqueous raffinate are produced free of solvents and sterilized for further safe use. The costs showed an important economy scale-up. This work could ease the transfer of the SFEE technology to the industry.

Investigation of Molecular Weight, Polymer Concentration and Process Parameters Factors on the Sustained Release of the Anti-Multiple-Sclerosis Agent Teriflunomide from Poly(ε-caprolactone) Electrospun Nanofibrous Matrices

In the current work, a series of PCL polyesters with different molecular weights was synthesized and used for the fabrication of nanofibrous patches via electrospinning, as sustained release matrices for leflunomide’s active metabolite, teriflunomide (TFL). The electrospinning conditions for each sample were optimized and it was found that only one material with high Mn (71,000) was able to produce structures with distinct fibers devoid of the presence of beads. The successful preparation of the fibers was determined by scanning electron microscopy (SEM).TFL (10, 20 and 30 wt%) in three different concentrations was incorporated into the prepared nanofibers, which were used in in vitro drug release experiments. The drug-loaded nanofibrous formulations were further characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and powder X-ray diffractometry (XRD).It was found that TFL was incorporated in an amorphous form inside the polymeric nanofibers and that significant molecular interactions were formed between the drug and the polyester. Additionally, in vitro dissolution studies showed that the PCL/TFL-loaded nanofibers exhibit a biphasic release profile, having an initial burst release phase, followed by a sustained release until 250 h. Finally, a kinetic analysis of the obtained profiles revealed that the drug release was directly dependent on the amount TFL incorporated into the nanofibers.