Production of thermoplastic starch and poly (butylene adipate-co-terephthalate) films assisted by solid-state shear pulverization

Gelatinized Cassava Starch Obtained via Low Molar Ratio Hydroxypropylation Reaction

Hydroxypropylated starch was successfully synthesized, aiming to address the limitations of native starch, such as poor mechanical properties and water sensitivity, which hinder its application in biodegradable polymers. The modification process, conducted at 115-135 °C with propylene oxide (PO) molar ratios of 0.4-0.8 [PO molecule per OH of starch], effectively disrupted the native starch structure. FTIR and 13C NMR confirmed methyl group incorporation, with lower temperatures and higher PO ratios yielding greater modification. SEM and XRD analyses demonstrated complete gelatinization; although some short-range order structures are present, long-range structures were eliminated, while DSC confirmed the absence of gelatinization peaks. TGA revealed the integration of lower molecular weight molecules, suggesting PPO homopolymerization within the starch granules. These structural transformations enhance the feasibility of producing hydroxypropylated starch films with reduced plasticizer content and energy requirements, offering a novel approach to improving starch-based materials for biodegradable applications.

Reactive extrusion fabrication of thermoplastic starch with Ca2+ heterodentate coordination structure for harvesting multiple-reusable PBAT/TPS films

Creating multiple-reusable PBAT/TPS (PT) films presents a novel solution to reduce carbon emissions from disposable packaging, addressing challenges like the high creep of PBAT and the glycerol migration of TPS. Consequently, adopting reactive extrusion to fabricate reversible cross-linking TPS with high shape memory performance, low migration, and homogeneous dispersion in PBAT matrix was a fascinating strategy. Herein, starch, glycerol and CaCl2 (calcium chloride) were extruded to fabricate TPS-Ca with Ca2+ heterodentate coordination structure and confirmed by XPS, 1H NMR and temperature-dependent FTIR. The results of DMA, dynamic rheology, flow activation energy and SEM revealed that TPS-Ca exhibited significant temperature-sensitive reversible properties and robust melt flow capability, enabling micro-nano scale dispersion in PBAT. Noteworthy, PBAT/TPS-Ca (PT-Ca) would recover 100 % length within 20 s by microwave heating after being loaded under the hygrothermal environment. Meanwhile, the migration weight of glycerol decreased from 2.5 % to 1.2 % for the heat-moisture-treated PBAT/TPS (HPT) and PBAT/TPS-Ca (HPTCa). Remarkably, the tensile strength and elongation at the break of HPT-Ca increased to 20.0 MPa and 924 %, respectively, due to reduced stress concentration sites in the phase interface. In summary, our study provides a streamlined strategy for fabricating multiple-reusable PT, offering a sustainable solution to eliminate carbon emissions linked to disposable plastic.

Development of cinnamon essential oil-loaded PBAT/thermoplastic starch active packaging films with different release behavior and antimicrobial activity

The poly (butylene adipate-co-terephthalate)/thermoplastic starch (PBAT/TPS) active packaging films containing cinnamon essential oil (CEO) were fabricated by melting blending and extrusion casting method. The effects of TPS content (0 %, 10 %, 20 %, 30 %, 40 % and 50 %) on the properties of the films and their application in largemouth bass preservation were studied. As TPS content increased from 0 % to 50 %, the water vapor permeability increased from 7.923 × 10-13 (g•cm/(cm2•s•Pa)) to 23.967 × 10-13 (g•cm/(cm2•s•Pa)), the oxygen permeability decreased from 8.642 × 10-11 (cm3•m/(m2•s•Pa)) to 3.644 × 10-11 (cm3•m/(m2•s•Pa)), the retention of CEO in the films increased. The release rate of CEO from the films into food simulant (10 % ethanol) accelerated with increasing TPS. The films exhibited different antibacterial activity against E. coli, S. aureus, and S. putrefaciens. It was closely related with the release behavior of the CEO. The films containing CEO could efficiently inhibit the decomposition of protein and the growth of microorganisms in largemouth bass. It showed that the higher TPS in the films, the better inhibitory effect. This study provided a new idea for developing PBAT/TPS active films with different release behavior of active agents and different antibacterial activity for food packaging.

Improvement of UV stability of thermoplastic starch matrix by addition of selected lignin fraction - Photooxidative degradation

This paper examines the additivation of thermoplastic starch (TPS) matrix by selected fractions of kraft lignin (KL) and correlates its structure-performance when exposed to photooxidative degradation. KL from Eucalyptus urograndis wood was refined by a sequential fractionation process in ethyl acetate (EtOAc). Films were prepared by mixing lignin fractions as additive in TPS matrix by casting and pressing. The lignin employed were KL, fraction of KL insoluble in EtOAc (INS) and fraction of KL soluble in EtOAc (SOL). The samples were exposed to accelerated aging with Ultraviolet-C light (UV-C) for 432 h. Structural changes were measured by FTIR (Fourier-Transform Infrared) spectra. Thermal properties, such as melting enthalpy, glass transition temperature and thermal decomposition, were evaluated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry). Morphology of the films was obtained by SEM (Scanning Electron Microscopy). Surface property of wettability was measured by contact angle. Mechanical properties were explored before and after exposure to UV-C light. It was observed that the least photodegraded films were those resulting from the addition of the lignin fraction with higher phenolic hydroxyl group content. According to structural and morphological observations, the soluble fraction (TSOL) presented the highest photoprotection and stabilizing effect as an UV-C light blocker additive on TPS matrix.

Melt-processed poly (vinyl alcohol)/corn starch/nanocellulose composites with improved mechanical properties

Corn starch (CS) and cellulose nanofibrils (CNFs) were incorporated into biodegradable poly (vinyl alcohol) (PVA) to prepare mechanically robust and sustainable composites through melt-processing. Based on the regulation and control of hydrogen bonding network, CS and CNFs can extend the processing window and improve the thermoplasticity of PVA composites. Fourier transform infrared spectroscopy and Raman spectra analysis indicate that the intra- and inter-molecular hydrogen bonds of PVA are broken, accompanied by the formation of new hydrogen bonds among PVA, CS and CNFs during the melt-processing treatment. Thermal analysis shows that the processing window of PVA composite is significantly broadened to 131.46 °C. The tensile strength, modulus and elongation at break of the composites reach to 28.19 MPa, 1572.54 MPa and 10.72% by the incorporation of 10 wt% CS and 10 wt% CNFs. This strategy is not only expected to provide a direction for preparing complex three-dimensional products of PVA by melt-processing, but also provide a method to enhance the mechanical properties of other biodegradable plastics.