Value-Added Upcycling of PET to 1,4-Cyclohexanedimethanol by a Hydrogenation/Hydrogenolysis Relay Catalysis

We present an innovative process for directly transforming poly(ethylene terephthalate) (PET), a polymer extensively used in food and beverage packaging, into trans-isomer-enriched 1,4-cyclohexanedimethanol (CHDM), a key ingredient in advanced specialty polymers. Our approach leverages a dual-catalyst system featuring palladium on reduced graphene oxide (Pd/r-GO) and oxalate-gel-derived copper-zinc oxide (og-CuZn), utilizing hydrogenation/hydrogenolysis relay catalysis. This method efficiently transforms PET into polyethylene-1,4-cyclohexanedicarboxylate (PECHD), which is then converted into CHDM with an impressive overall yield of 95 % in a two-stage process. Our process effectively handles various post-consumer PET plastics, converting them into CHDM with yields between 78 % and 89 % across different substrates. Additionally, we demonstrate the applicability and scalability of this approach through a temperature-programmed three-stage relay process on a 10-gram scale, which results in purified CHDM with an isolated yield of 87 % and a notably higher trans/cis ratio of up to 4.09/1, far exceeding that of commercially available CHDM. This research not only provides a viable route for repurposing PET waste but also enhances the control of selectivity patterns in multistage relay catalysis.

Biosynthesis of aliphatic plastic monomers with amino residues in Yarrowia lipolytica

Introduciton: The α,ω-diamines (NH₂-(CH₂)_n-NH₂) and ω -amino fatty acids (NH₂-(CH₂)_n-COOH) have been widely used as building blocks in polymerindustries. Medium- to long-chain (C₈ to C₁₈) fatty acid monomers with amino residues are almost exclusively produced via chemical processes that generate hazardous waste and induce severe environmental problems, such as global warming and pollution. Here, we present the construction platformstrains of Yarrowia lipolytica a cheese-ripening yeast, for direct biotransformation of hydrocarbons into medium- to long-chain α,ω-diamines and ωamino fatty acids using metabolic engineering of endogenous fatty acid ω- and β-oxidation pathways and introducing heterologous ω-transaminase in Y. lipolytica. Methods: We deleted six genes encoding the acyl-CoA oxidase (ACO1-6) and four fatty aldehyde dehydrogenase genes (FALDH1-4), which catalyze fatty acid β-oxidation and downstream oxidation of fatty aldehydes in Y. lipolytica, respectively. The ω-transaminase from Chromobacterium violaceum DSM30191 was introduced into the genome of the ΔPOX ΔFALDH strain under the control of Y. lipolytica-derived EXP1 promoters. Results and Discussion: The ΔPOX ΔFALDH strains with ω-CvTA successfully accumulated the corresponding C12 αω-diamines into a shaking culture medium with dodecane or dodecanol. In addition, these strains accumulated C₁₂ ω-amino fatty acids from dodecanoic acid. With the commercially available α,ω-diacid bioprocess, this yeast biosynthesis producing medium- and longchain α,ω-diamines and ω-amino fatty acids could complete the yeast platform technology generating all medium- and long-chain aliphatic polyamide monomers, α,ω-biofunctionalized with one or both carboxylic acid and amino residues.

Synthesis, characterization and biodegradation studies of polyurethanes: Effect of unsaturation on biodegradability

The presence of unsaturation in the main chain of the polymer promotes the biodegradation process. To elucidate this hypothesis, one unsaturated polyurethane (PUU) and another saturated polyurethane (PUS) were synthesized and then biodegraded, and evidence was found to support this hypothesis. The polyurethanes were synthesized by a polycondensation reaction with yields up to 97%. It is important to note that both polyurethanes were constituted only by the recalcitrant hard segment and showed low crystallinity and molecular weight. Spectroscopic, thermal, and chromatographic techniques were used for physical and structural characterization. Both polyurethanes were biodegraded by the BP8 microbial community and the Cladosporium tenuissimum A3.I.1 fungus during a two-month period. A postbiodegradation characterization revealed the detriment of properties in both materials, indicating successful biodegradation. As a general trend, more efficient biodegradation was observed by the Cladosporium tenuissimum fungus A3.I.1 than by the BP8 microbial community. Specifically, with the fungus, the infrared analysis showed a decrease in the characteristic bands as well as the appearance of new carboxylic acid signals (approximately 1701 cm^-1), suggesting the enzymatic cleavage of the urethane group. By comparison to polyurethanes, PUU showed superior biodegradation; using the fungus, a 51% decrease in molecular weight (M_w) for PUU was achieved, in contrast with 36% achieved for PUS. Despite the low crystallinity and molecular weight, the determining factor in biodegradation was the presence of unsaturations along the main chain. Thus, a more efficient oxidative attack is carried out by microorganisms on double bonds. The novel PUU showed similar biodegradation to the known polyester-type PU with highly hydrolysable groups. Consequently, PUU represents a green alternative to conventional polyurethanes and is a key material to achieve biorecycling.

Study on Flexural Behavior of Glass Fiber Reinforced Plastic Sandwich Composites Using Liquid Thermoplastic Resin

Experimental and numerical studies of composite sandwich structures are warranted to reap the benefits of these materials when they are well designed. In the current research, new liquid thermoplastic and epoxy resins were used to fabricate four composite sandwich panels with two additional foam types and different densities in the wind turbine industry. A comprehensive comparison of three-point bending test results was made. Finite-element-based simulations using the ABAQUS program with Hashin’s damage criterion were conducted to examine the failure behavior of the GFRP sandwich composites. The flexural behavior of the glass-fiber-reinforced plastic (GFRP) sandwich panels was investigated and compared with the experiments. The results show that the GF/PVC/Elium composite panel gives the highest load absorption, flexural strength, flexural modulus, core shear ultimate strength, and facing stress due to effect of the core foam and resin types. For the PVC foam core sandwich panel, using thermoplastic resin increased the flexural strength by 18% compared to that of the epoxy resin. The simulation results show excellent agreement between the finite-element-predicted failure loads and the experimental results.

Ferulic Acid as Building Block for the Lipase-Catalyzed Synthesis of Biobased Aromatic Polyesters

Enzymatic synthesis of aromatic biobased polyesters is a recent and rapidly expanding research field. However, the direct lipase-catalyzed synthesis of polyesters from ferulic acid has not yet been reported. In this work, various ferulic-based monomers were considered for their capability to undergo CALB-catalyzed polymerization. After conversion into diesters of different lengths, the CALB-catalyzed polymerization of these monomers with 1,4-butanediol resulted in short oligomers with a DP_n up to 5. Hydrogenation of the double bond resulted in monomers allowing obtaining polyesters of higher molar masses with DP_n up to 58 and M_w up to 33,100 g·mol⁻¹. These polyesters presented good thermal resistance up to 350 °C and T_g up to 7 °C. Reduction of the ferulic-based diesters into diols allowed preserving the double bond and synthesizing polyesters with a DP_n up to 19 and M_w up to 15,500 g·mol⁻¹ and higher T_g (up to 21 °C). Thus, this study has shown that the monomer hydrogenation strategy proved to be the most promising route to achieve ferulic-based polyester chains of high DP_n. This study also demonstrates for the first time that ferulic-based diols allow the synthesis of high T_g polyesters. Therefore, this is an important first step toward the synthesis of competitive biobased aromatic polyesters by enzymatic catalysis.