On the Selective Enzymatic Recycling of Poly(pentamethylene 2,5-furanoate)/Poly(lactic acid) Blends and Multiblock Copolymers

Among novel renewablefuranoate-based polyesters, poly(pentamethylene2,5-furandicarboxylate) (PPeF) shows outstanding gas barrier propertiesand high flexibility. PPeF blending/copolymerization with anotherwell-known bio-based polymer, poly(lactic acid) (PLA), leads to considerablybetter mechanical and gas barrier properties of the latter, makingit suitable for flexible food packaging applications. In this work,enzymatic depolymerization of PLA/PPeF blends with different compositions(1, 3, 5, 20, 30, and 50 wt % PPeF) and a PLA-PPeF block copolymer(50 wt % PPeF) by cutinase 1 from Thermobifida cellul ositilytica (Thc_Cut1) was investigatedas a possible recycling strategy. Based on quantification of weightloss and high-performance liquid chromatography (HPLC) analysis ofreleased molecules, faster hydrolysis was seen for PLA/PPeF blendswith increasing PPeF content when compared to neat PLA, while theblock copolymer (P(LA50PeF50)) was significantly less susceptibleto hydrolysis. Surface morphology analysis (via scanning electronmicroscopy), Fourier transform infrared spectroscopy, and NMR analysisconfirmed preferential hydrolysis of the PPeF component. Through crystallization,2,5-furandicarboxylic acid was selectively recovered from the depolymerizedfilms and used for the resynthesis of the PPeF homopolymer, demonstratingthe potential of enzymes for novel recycling concepts. The possibilityof selective recovery of 2,5-furandicarboxylic acid from the completelydepolymerized films with a 75% yield could bring further evidenceof the high value of these materials, both in the form of blends andcopolymers, for a sustainable whole packaging life cycle, where PPeFis potentially enzymatically recycled and PLA is mechanically recycled. This work developed a sustainable plasticrecycling approachthat allows the selective depolymerization of one component of a blendand the monomer recovery for the subsequent resynthesis process.