| 1. |
- Avella, Angelica, 1995, et al.
(författare)
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Organo-Mediated Ring-Opening Polymerization of Ethylene Brassylate from Cellulose Nanofibrils in Reactive Extrusion
- 2024
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Ingår i: ACS Sustainable Chemistry & Engineering. - 2168-0485. ; 12:29, s. 10727-10738
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Tidskriftsartikel (refereegranskat)abstract
- Ethylene brassylate is a renewable macrolactone from castor oil that can be polymerized via ring-opening polymerization (ROP) to obtain a fully biosourced biodegradable polyester. ROP mediated by organometallic catalysts leads to high molar mass poly(ethylene brassylate) (PEB). However, the use of metal-free organocatalysis has several advantages, such as the reduction of toxic and expensive metals. In this work, a novel cellulose nanofibril (CNF)/PEB nanocomposite fabrication process by organocatalysis and reactive extrusion (REx) is disclosed. Here, ROP was carried out via solvent-free REx in the presence of CNFs using organic 1,5,7-triazabicyclo[4.4.0]dec-5-ene as a catalyst. Neat or lactate-esterified CNFs (LACNF) were used as initiators to investigate the effect of surface topochemistry on the in situ polymerization and the properties of the nanocomposites. A molar mass of 9 kDa was achieved in the presence of both unmodified and LACNFs with high monomer conversion (>98%) after 30 min reaction in a microcompounder at 130 °C. Tensile analysis showed that both nanofibril types reinforce the matrix and increase its elasticity due to the efficient dispersion obtained through the grafting from polymerization achieved during the REx. Mechanical recycling of the neat polymer and the nanocomposites was proven as a circular solution for the materials’ end-of-life and showed that lactate moieties induced some degradation.
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| 2. |
- Avella, Angelica, 1995, et al.
(författare)
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Reusable, Recyclable, and Biodegradable Heat-Shrinkable Melt Cross-Linked Poly(butylene adipate-co-terephthalate)/Pulp Biocomposites for Polyvinyl Chloride Replacement
- 2024
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Ingår i: ACS Sustainable Chemistry & Engineering. - 2168-0485. ; 12:13, s. 5251-5262
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Tidskriftsartikel (refereegranskat)abstract
- Heat-shrinkable films are widely used as disposable secondary packaging but are conventionally made from fossil-based and nonbiodegradable polyvinyl chloride or polyethylene. To lower the environmental impact of such products, this work reports the development of recyclable, biodegradable, and partially biosourced heat-shrinkable biocomposites that are cost-competitive with existing shrink wraps. Poly(butylene adipate-co-terephthalate), a growing biodegradable thermoplastic, was simultaneously reinforced with pulp fibers and partially cross-linked in a single-step reactive melt processing. The designed peroxide-initiated reaction led to a 55 wt % cocontinuous insoluble gel incorporating all the pulp fibers into a cross-linked polymer network. In the solid state, the cross-linked biocomposite shows 60% elongation at break with a 200% increase in Young’s modulus, while the only addition of pulp fibers stiffens and embrittles the matrix. Creep tests in the melt state indicated that the cross-linked network induces homogeneous shrinking even during the loading phase, demonstrating the potential use of the biocomposites as heat-shrinkable films. The shrinking also promotes the shape-memory of the biocomposite, which retains its dimensions after four cycles. The circularity of the materials was assessed by mechanical recycling and industrial composting, which have proven feasible end-of-life options for heat-shrinkable biocomposites.
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| 3. |
- De Cristofaro, Giuseppa Anna, et al.
(författare)
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Interface interactions driven antioxidant properties in olive leaf extract/cellulose nanocrystals/poly(butylene adipate-co-terephthalate) biomaterials
- 2024
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Ingår i: International Journal of Biological Macromolecules. - 0141-8130 .- 1879-0003. ; 272
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Tidskriftsartikel (refereegranskat)abstract
- Functional packaging represents a new frontier for research on food packaging materials. In this context, adding antioxidant properties to packaging films is of interest. In this study, poly(butylene adipate-co-terephthalate) (PBAT) and olive leaf extract (OLE) have been melt-compounded to obtain novel biomaterials suitable for applications which would benefit from the antioxidant activity. The effect of cellulose nanocrystals (CNC) on the PBAT/OLE system was investigated, considering the interface interactions between PBAT/OLE and OLE/CNC. The biomaterials' physical and antioxidant properties were characterized. Morphological analysis corroborates the full miscibility between OLE and PBAT and that OLE favours CNC dispersion into the polymer matrix. Tensile tests show a stable plasticizer effect of OLE for a month in line with good interface PBAT/OLE interactions. Simulant food tests indicate a delay of OLE release from the 20 wt% OLE-based materials. Antioxidant activity tests prove the antioxidant effect of OLE depending on the released polyphenols, prolonged in the system at 20 wt% of OLE. Fluorescence spectroscopy demonstrates the nature of the non-covalent PBAT/OLE interphase interactions in π-π stacking bonds. The presence of CNC in the biomaterials leads to strong hydrogen bonding interactions between CNC and OLE, accelerating OLE released from the PBAT matrix.
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| 4. |
- Gammino, Michele, et al.
(författare)
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Chemical-free Reactive Melt Processing of Biosourced Poly(butylene-succinate-adipate) for Improved Mechanical Properties and Recyclability
- 2024
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Ingår i: ACS Applied Polymer Materials. - 2637-6105. ; 6:10, s. 5866-5877
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Tidskriftsartikel (refereegranskat)abstract
- Biosourced and biodegradable polyesters like poly(butylene succinate-co-butylene adipate) (PBSA) are gaining traction as promising alternatives to oil-based thermoplastics for single-use applications. However, the mechanical and rheological properties of PBSA are affected by its thermomechanical sensitivity during its melt processing, also hindering PBSA mechanical recycling. Traditional reactive melt processing (RP) methods use chemical additives to counteract these drawbacks, compromising sustainability. This study proposes a green reactive method during melt compounding for PBSA based on a comprehensive understanding of its thermomechanical degradative behavior. Under the hypothesis that controlled degradative paths during melt processing can promote branching/recombination reactions without the addition of chemical additives, we aim to enhance PBSA rheological and mechanical performance. An in-depth investigation of the in-line rheological behavior of PBSA was conducted using an internal batch mixer, exploring parameters such as temperature, screw rotation speed, and residence time. Their influence on PBSA chain scissions, branching/recombination, and cross-linking reactions were evaluated to identify optimal conditions for effective RP. Results demonstrate that specific processing conditions, for example, twelve minutes processing time, 200 °C temperature, and 60 rpm screw rotation speed, promote the formation of the long chain branched structure in PBSA. These structural changes resulted in a notable enhancement of the reacted PBSA rheological and mechanical properties, exhibiting a 23% increase in elastic modulus, a 50% increase in yield strength, and an 80% increase in tensile strength. The RP strategy also improved PBSA mechanical recycling, thus making it a potential replacement for low-density polyethylene (LDPE). Ultimately, this study showcases how finely controlling the thermomechanical degradation during reactive melt processing can improve the material’s properties, enabling reliable mechanical recycling, which can serve as a green approach for other biodegradable polymers.
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| 5. |
- Wohlert, Jakob, et al.
(författare)
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Acetylation of Nanocellulose: Miscibility and Reinforcement Mechanisms in Polymer Nanocomposites
- 2024
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Ingår i: ACS Nano. - 1936-086X .- 1936-0851. ; 18:3, s. 1882-1891
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Tidskriftsartikel (refereegranskat)abstract
- The improvement of properties in nanocomposites obtained by topochemical surface modification, e.g., acetylation, of the nanoparticles is often ascribed to improved compatibility between the nanoparticle and the matrix. It is not always clear however what is intended: specific interactions at the interface leading to increased adhesion or the miscibility between the nanoparticle and the polymer. In this work, it is demonstrated that acetylation of cellulose nanocrystals greatly improves mechanical properties of their nanocomposites with polycaprolactone. In addition, molecular dynamics simulations with a combination of potential of mean force calculations and computational alchemy are employed to analyze the surface energies between the two components. The work of adhesion between the two phases decreases with acetylation. It is discussed how acetylation can still contribute to the miscibility, which leads to a stricter use of the concept of compatibility. The integrated experimental-modeling toolbox used has wide applicability for assessing changes in the miscibility of polymer nanocomposites.
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