Thermal decomposition kinetics and properties of grafted barley husk reinforced PVA/starch composite films for packaging applications

Fabrication of poly(vinyl alcohol)/sulfonated itaconic starch blend film with enhanced antibacterial performance and soil absorption capacity for environment-friendly packaging

Plastic packaging is widely used due to its light weight, ease of processing, and cost-effectiveness, but improper disposal causes environmental pollution and resource waste. Developing environment-friendly packaging materials is urgent. Herein, a water-soluble poly(vinyl alcohol) (PVA)/starch blend film was proposed by combining modification and thermal processing, and its performance was evaluated. Starch was modified via a three-step process-acid hydrolysis, itaconic anhydride esterification, and sodium bisulfite sulfonation-to produce sulfonated itaconic starch. The introduction of carboxyl and sulfonic groups improved the hydrophilicity of PVA/starch blends. The water contact angle of the modified blend film was notably decreased in comparison to that unmodified one. The blend films also demonstrated an enhancement in UV shielding properties, effectively reducing rhodamine B photodegradation under extended UV exposure. Besides, the incorporated groups improved the antibacterial performance of the blend film, exhibiting the efficient enhancement on the antibacterial effects on both E. coli and S. aureus. Moreover, the film exhibited the good soil absorption capacity, dissolving completely in soil within 12 h, highlighting its potential for environment-friendly food packaging applications.

Uranium Extraction from Seawater: A Novel Approach Using Aluminum Fumarate-Based Metal-Organic Framework Aerogels

Efficient extraction of uranyl ions from seawater is crucial for the commercialization of nuclear technology. Metal-organic frameworks (MOFs), with their superior uranium extraction properties, face challenges in large-scale applications due to their powdery nature and the difficulty of assembling them into mechanically stable macroscopic composites. To address this, successfully synthesized 90 wt % nanoMOF (aluminum fumarate) loaded directional aerogels (AlFA-3-10) using polyvinyl alcohol (PVA) as an adhesive, which demonstrates robust strength longitudinally and transversely. Our uranium adsorption experiments reveal that at a pH of 8 (akin to that of seawater), the AlFA-3-10 achieves a maximum adsorption capacity of 1146.25 mg g-1, maintaining this exceptional performance over five cycles. Notably, in simulated seawater, AlFA-3-10 exhibits high selectivity for uranyl ions with minimal interference from other ions. The directional pores within AlFA-3-10 facilitate fluid transmission and exchange, ensuring optimal contact between the MOF and uranyl ions, thereby enhancing electrostatic attraction and electron transport for improved capture efficiency. This streamlined approach maximizes the intrinsic potential of nano-MOFs and heralds a new era for their integration into macroscopic composite materials.

Engineered environment-friendly multifunctional food packaging with superior nonleachability, polymer miscibility and antimicrobial activity

This study was conducted primarily to develop an environment-friendly food packaging boasting several advantages, including good water vapor barrier, UV resistance, antimicrobial activity, non-leachability, and polymer miscibility. Initially, the starch-based antimicrobial agent (OCSI) was synthesized through a simple esterification reaction between oxidized corn starch (OCS) and indoleacetic acid (IAA). Subsequently, OCSI was further blended separately with environmentally-friendly materials (PVA, PBAT, PCL), and a series of environment-friendly packaging films were successfully prepared. The resulting films exhibited desirable thermal stability and 100 % barrier against both UV-A and UV-B rays. Moreover, the films presented effective barriers against water vapor, antioxidant, and antimicrobial activity against E. coli and S. aureus. Meanwhile, the films could significantly inhibit the deterioration of fresh fruits and prolong shelf life, considerably expanding their utilization in safe packaging. The environment-friendly packaging not only realized the sustainable utilization of green polymers, but also offered novel insights into the exploration of sustainable packaging.

Characterization of corn starch/chitosan composite films incorporated with amino-, carboxyl-，and hydroxyl-terminated hyperbranched dendrimers: A comparative study

Bio-based materials are gaining traction as sustainable plastic replacements, but their performance in terms of mechanics, antibacterial action, and water resistance is often subpar. Our research sought to enhance these attributes by integrating nanoscale dendrimers into a starch/chitosan (SC) matrix. We introduced three varieties of dendrimers-amino-, carboxyl-, and hydroxyl-terminated-at a modest 2.5 % w/w concentration to fabricate NSC, CSC, and HSC films. Comprehensive analyses revealed that the dendrimers fostered intermolecular interactions, prompting an order-disorder shift in the matrix. This interaction textured the film surface and bolstered its thickness, opacity, and tensile strength. The HSC films achieved the highest tensile strength (9.96 MPa) and substantial elongation (254.30 %), attributed to their more disordered structure. The HSC films also showcased enhanced thermal stability and reduced moisture absorption. Notably, NSC films exhibited excellent antibacterial effects against S. aureus and E. coli. The performance improvement of CSC film is mediocre. This study underscores the promise of dendrimer-fortified SC films in the realm of biodegradable materials.

Polyvinyl alcohol/collagen composite scaffold reinforced with biodegradable polyesters/gelatin nanofibers for adipose tissue engineering

Breast cancer has become the most diagnosed cancer type, endangering the health of women. Patients with breast resection are likely to suffer serious physical and mental trauma. Therefore, breast reconstruction becomes an important means of postoperative patient rehabilitation. Polyvinyl alcohol hydrogel has great potential in adipose tissue engineering for breast reconstruction. However, its application is limited because of the lack of bioactive factors and poor structural stability. In this study, we prepared biodegradable polylactic acid-glycolic acid copolymer/polycaprolactone/gelatin (PPG) nanofibers. We then combined them with polyvinyl alcohol/collagen to create tissue engineering scaffolds to overcome limitations. We found that PPG fibers formed amide bonds with polyvinyl alcohol/collagen scaffolds. After chemical crosslinking, the number of amide bonds increased, leading to a significant improvement in their mechanical properties and thermal stability. The results showed that compared with pure PVA scaffolds, the maximum compressive stress of the scaffold doped with 0.9 g nanofibers increased by 500 %, and the stress loss rate decreased by 40.6 % after 10 cycles of compression. The presence of natural macromolecular gelatin and the changes in the pore structure caused by nanofibers provide cells with richer and more three-dimensional adsorption sites, allowing them to grow in three dimensions on the scaffold. So, the hydrogel scaffold by reinforcing polyvinyl alcohol hydrogel with PPG fibers is a promising breast reconstruction method.

Kinetics Study of PVA Polymer by Model-Free and Model-Fitting Methods Using TGA

Thermogravimetric Analysis (TGA) serves a pivotal technique for evaluating the thermal behavior of Polyvinyl alcohol (PVA), a polymer extensively utilized in the production of fibers, films, and membranes. This paper targets the kinetics of PVA thermal degradation using high three heating rate range 20, 30, and 40 K min-1. The kinetic study was performed using six model-free methods: Freidman (FR), Flynn-Wall-Qzawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink (STK), Kissinger (K), and Vyazovkin (VY) for the determination of the activation energy (Ea). TGA showed two reaction stages: the main one at 550-750 K and the second with 700-810 K. But only the first step has been considered in calculating Ea. The average activation energy values for the conversion range (0.1-0.7) are between minimum 104 kJ mol-1 by VY to maximum 199 kJ mol-1 by FR. Model-fitting has been applied by combing Coats-Redfern (CR) with the master plot (Criado's) to identify the most convenient reaction mechanism. Ea values gained by the above six models were very similar with the average value of (126 kJ mol-1) by CR. The reaction order models-Second order (F2) was recommended as the best mechanism reaction for PVA pyrolysis. Mechanisms were confirmed by the compensation effect. Finally, (∆H, ∆G, and ∆S) parameters were presented and proved that the reaction is endothermic.

Pre-gelatinized high-amylose starch enables easy preparation of flexible and antimicrobial composite films for fresh fruit preservation

While high-amylose starch (HAS) possesses advantageous properties such as high resistant starch content and favorable mechanical attributes, its gelatinization constraints have limited its applicability. This study enhances its versatility by focusing on pre-gelatinized (PG) HAS with exceptional rehydratability, achieved by disorganizing native HAS granules (with amylose contents of 55 % and 68 %, respectively) using a 33 % CaCl2 solution, followed by water-ethanol precipitation and freeze-drying. The resulting PG-HAS exhibited elevated amylose content (61 % and 75 %) with minimal changes in amylose molecular weight. PG-HAS displayed superior water-absorption index (WAI) and water-soluble index (WSI) compared to native HAS, further improved by 2 % CaCl2 solution incorporation. Furthermore, composite films were prepared by mixing PG-HAS with PVA at a 6:4 (w/w) ratio. The PG-G50 (61 % amylose content)/PVA composite film exhibited remarkable elongation (131.1 ± 5.4 %), nearly three times that of a normal corn starch (NCS, with 27 % amylose)/PVA film, attributed to improved starch dispersity and higher amylose content. Nonetheless, the PG-G70 (75 % amylose content)/PVA film at the same ratio showed lower elongation (54.7 ± 8.0 %), potentially due to strong cohesive forces between amylose chains that impede starch-PVA interactions. Moreover, the PG-HAS/PVA composite films, enriched with antibacterial agents, demonstrated effective antibacterial properties with a gradual and sustained release of active compounds. Notably, the PG-G50/PVA/tannic acid (TA) film effectively preserved fresh apple slices by inhibiting bacteria growth and preventing browning. These findings underscore the excellent rehydration of PG-HAS and its potential as an inner packaging material for irregularly shaped foods, such as sliced fruits or meats, due to its nontoxic nature, softness and flexibility, which allows the film to maintain close contact with food surfaces.

Sheath-core structured Ca-alginate/PVA aerogel fibers via directed freezing wet-spinning

Biomass-based aerogel fibers have attracted increasing attention due to their renewable nature. However, their disadvantages, such as low mechanical strength, poor long-range order, and easy combustion, are still significant challenges. Herein, a directed freezing-assisted forced stretching strategy is developed to fabricate sheath-core structured Ca-alginate/polyvinyl alcohol (Ca-A/PVA) aerogel fibers with Long-range-ordered pores. The Ca-A/PVA aerogel fibers (3:2 m/m) exhibit the best comprehensive mechanical properties in terms of low thermal conductivity of 0.0524 W·m^-1·K^-1, a density of 0.1614 g·cm^-3, a porosity of 89.9 %, a tensile strength of 8.72 MPa, a tensile modulus of 249.7 MPa, a toughness of 1.98 MJ∙m^-3, and a self-extinguishing time from the fire of <1.2 s. The Ca-A/PVA fabrics showed a maximum absolute temperature difference of 11.4 °C at -20 °C and 14.0 °C at 60 °C compared to the plate temperature. The presented strategy is generalizable to other alginate-based aerogel fibers (e.g., alginate/guar gum).

Ag@MOF-loaded p-coumaric acid modified chitosan/chitosan nanoparticle and polyvinyl alcohol/starch bilayer films for food packing applications

Developing novel bilayer food packing film having the ability to prevent bacterial infections and capable of inhibiting oxidation is utmost important, since bacterial infections and oxidation can cause food spoilage. Ag-Metal-organic framework loaded p-coumaric acid modified chitosan (P-CS/Ag@MOF) or chitosan nanoparticles (P-CSNPs/Ag@MOF) and polyvinyl alcohol/starch (PVA/ST) were used as the upper film and lower layer film to successfully prepare a bilayer composite film. The microscopic morphology, water resistance, oil resistance, oxidation resistance, optical properties, cytotoxicity and antibacterial properties of the composite films were compared. The results showed that the surface of P-CS/Ag@MOF bilayer was relatively smooth and its tensile strength (TS) was higher (27.67 MPa). Among them, P-CS/Ag@MOF bilayer films had better oil resistance and oxidation resistance activity. In addition, the P-CS/Ag@MOF bilayer film had good UV-blocking properties and transparency. P-CSNPs/Ag@MOF bilayer film had higher antibacterial activity and cytotoxicity.

Microfibrillated cellulose reinforced starch/polyvinyl alcohol antimicrobial active films with controlled release behavior of cinnamaldehyde

The starch/polyvinyl alcohol (ST/PVA) films incorporated with cinnamaldehyde (CIN) and microfibrillated cellulose (MFC) were developed. The effect of MFC content on the films' properties was studied. The SEM results showed that MFC promoted compatibility among starch, PVA and CIN. With increased content of MFC, the strength of the films was improved and their flexibility reduced, the films' crystallinity degree and hydrophobicity were improved. The oxygen and water vapor permeability of the films both reduced first and then increased as a whole. The release of CIN from films into the food stimulant (10% ethanol) could be controlled by MFC. When MFC content was between 1% and 7.5%, it decelerated the release of CIN but high MFC content exceeded 10% promoted the release of CIN. It revealed that films containing CIN could inhibit growth of S. putrefaciens. It showed a good prospect of using MFC to develop controlled release active ST/PVA films.

Upcycling Biodegradable PVA/Starch Film to a Bacterial Biopigment and Biopolymer

Meeting the challenge of circularity for plastics requires amenability to repurposing post-use, as equivalent or upcycled products. In a compelling advancement, complete circularity for a biodegradable polyvinyl alcohol/thermoplastic starch (PVA/TPS) food packaging film was demonstrated by bioconversion to high-market-value biopigments and polyhydroxybutyrate (PHB) polyesters. The PVA/TPS film mechanical properties (tensile strength (σ_u), 22.2 ± 4.3 MPa; strain at break (ε_u), 325 ± 73%; and Young’s modulus (E), 53–250 MPa) compared closely with low-density polyethylene (LDPE) grades used for food packaging. Strong solubility of the PVA/TPS film in water was a pertinent feature, facilitating suitability as a carbon source for bioprocessing and microbial degradation. Biodegradability of the film with greater than 50% weight loss occurred within 30 days of incubation at 37 °C in a model compost. Up to 22% of the PVA/TPS film substrate conversion to biomass was achieved using three bacterial strains, Ralstonia eutropha H16 (Cupriavidus necator ATCC 17699), Streptomyces sp. JS520, and Bacillus subtilis ATCC6633. For the first time, production of the valuable biopigment (undecylprodigiosin) by Streptomyces sp. JS520 of 5.3 mg/mL and the production of PHB biopolymer at 7.8% of cell dry weight by Ralstonia eutropha H16 from this substrate were reported. This low-energy, low-carbon post-use PVA/TPS film upcycling model approach to plastic circularity demonstrates marked progress in the quest for sustainable and circular plastic solutions.

Metal Organic Frameworks Derived Sustainable Polyvinyl Alcohol/Starch Nanocomposite Films as Robust Materials for Packaging Applications

Bio-nanocomposites-based packaging materials have gained significance due to their prospective application in rising areas of packaged food. This research aims to fabricate biodegradable packaging films based upon polyvinyl alcohol (PVA) and starch integrated with metal-organic frameworks (MOFs) or organic additives. MOFs offer unique features in terms of surface area, mechanical strength, and chemical stability, which make them favourable for supporting materials used in fabricating polymer-based packaging materials. zeolitic imidazolate frameworks (ZIFs) are one of the potential candidates for this application due to their highly conductive network with a large surface area and high porosity. Present research illustrates a model system based on ZIF-67 (C₈H₁₀N₄Co) bearing 2–10 wt.% loading in a matrix of PVA/starch blend with or without pyrolysis to probe the function of intermolecular interaction in molecular packing, tensile properties, and glass transition process. ZIF-67 nanoparticles were doped in a PVA/starch mixture, and films were fabricated using the solution casting method. It was discovered through scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) that addition of ZIF-67 and pyrolyzed ZIF-67 changed and enhanced the thermal stability of the membrane. Moreover, 2–10 wt.% loading of ZIF-67 effected the thermal stability, owing to an interlayer aggregation of ZIF-67. The membranes containing pyrolyzed ZIF-67 showed mechanical strength in the order of 25 MPa in a moderate loading of pyrolyzed ZIF-67 (i.e., at 4 wt.%). The crystallinity enhanced by an increment in ZIF-67 loading. On the other hand, pyrolyzed ZIF-67 carbon became amorphous because of the inert environment and elevated temperature. The surface area also increased after the pyrolysis, which helped to increase the strength of the composite films.

Epoxidized Block and Statistical Copolymers Reinforced by Organophosphorus-Titanium-Silicon Hybrid Nanoparticles: Morphology and Thermal and Mechanical Properties

Glycidyl methacrylate (GMA) and a mixture of alkyl methacrylates (average chain length of 13 carbons; termed C13MA; derived from vegetable oils) were copolymerized by nitroxide-mediated polymerization to form epoxidized statistical and block copolymers with similar compositions (F GMA ∼0.8), which were further cross-linked by a bio-based diamine. Hybrid plate-like nanoparticles containing organophosphorus-titanium-silicon (PTS) with an average size of ∼130 nm and high decomposition temperature (485 °C) were synthesized via a hydrothermal reaction to serve as additives to simultaneously enhance the thermal and mechanical properties of the blend. Nanocomposites filled with PTS were prepared at different filler-loading levels (0.5, 2, 4 wt %). Transmission electron microscopy (TEM) of the cured block copolymer displayed reaction-induced macrophase-separated domains. TEM also showed an effective dispersion of PTS hybrids in the matrix without intense agglomeration. Thermogravimetric analysis at different heating rates revealed the activation energy of poly (GMA-stat-C13MA) at maximum decomposition increased from 143.5 to 327.2 kJ mol-1 with 4 wt % PTS. Decomposition temperature and char residue improved 12 °C and ∼7 wt %, respectively, and T g increased 12 °C by adding 4 wt % PTS. Targeting various PTS concentrations enabled tuning of the tensile modulus (up to 75%), tensile strength (up to 46%), and storage modulus in both glassy state (up to 59%) and rubbery plateau regions (up to 88%). Oscillatory frequency sweeps indicated that PTS makes the storage modulus frequency dependent, suggesting that the inclusion of the nanoparticles alters the relaxation of the surrounding matrix polymer.

Characterization of polyvinyl alcohol/starch composite films incorporated with p-coumaric acid modified chitosan and chitosan nanoparticles: A comparative study

In this paper, polyvinyl alcohol/starch composite films with p-coumaric acid modified chitosan (P-CS) and chitosan nanoparticles (P-CSNPs) at different concentrations were successfully prepared. The films were compared for their mechanical, thermal, physical, antioxidant, antibacterial, cytotoxicity and optical barrier properties. The results suggested that P-CS could significantly increase the tensile strength (TS) of the film from 15.67 MPa to a maximum of 24.32 MPa. The compact structure of P-CSNPs film prevented water diffusion, reducing the water amount within. Both films showed a reduction in water solubility, the extent of swelling, and water vapor transmittance. Specifically, P-CSNPs films showed better thermal stability while P-CS films revealed higher antioxidant activity. Besides, the P-CS films exhibited excellent transparency and good ultraviolet-barrier at 200-280 nm. P-CSNPs films demonstrated higher antibacterial activity on both Gram-negative and Gram-positive bacteria. Additionally, P-CS films were less cytotoxic compared to P-CSNPs films.

Recent trends in the application of modified starch in the adsorption of heavy metals from water: A review

The presence of polyfunctional ligands on the bio-macromolecules acts as an efficient adsorbent for heavy metal ions. Starch is one of the most abundant, easily available and cheap biopolymer of plant origin. However, native starch exhibits significantly low adsorption capacity due to the absence of some essential functional groups like carboxyl, amino or ester groups and is thus modified using various reaction routes like grafting, cross-linking, esterification, oxidation and irradiation for addition of functional groups to increase its adsorption capacity. The present review provides a comprehensive discussion on the above mentioned modification schemes of starch over the last 10-15 years highlighting their preparation methods, physico-chemical characteristics along with their adsorption capacities and mechanisms of heavy metal ions from water.

Lifetime Prediction Methods for Degradable Polymeric Materials-A Short Review

The determination of the secure working life of polymeric materials is essential for their successful application in the packaging, medicine, engineering and consumer goods industries. An understanding of the chemical and physical changes in the structure of different polymers when exposed to long-term external factors (e.g., heat, ozone, oxygen, UV radiation, light radiation, chemical substances, water vapour) has provided a model for examining their ultimate lifetime by not only stabilization of the polymer, but also accelerating the degradation reactions. This paper presents an overview of the latest accounts on the impact of the most common environmental factors on the degradation processes of polymeric materials, and some examples of shelf life of rubber products are given. Additionally, the methods of lifetime prediction of degradable polymers using accelerated ageing tests and methods for extrapolation of data from induced thermal degradation are described: the Arrhenius model, time-temperature superposition (TTSP), the Williams-Landel-Ferry (WLF) model and 5 isoconversional approaches: Friedman's, Ozawa-Flynn-Wall (OFW), the OFW method corrected by N. Sbirrazzuoli et al., the Kissinger-Akahira-Sunose (KAS) algorithm, and the advanced isoconversional method by S. Vyazovkin. Examples of applications in recent years are given.