Structural and morphological evaluation of CNC reinforced PVA/Starch biodegradable films

Enhanced pH-sensitive anthocyanin film based on chitosan quaternary ammonium salt: A promising colorimetric indicator for visual pork freshness monitoring

An intelligent pH response indicator film is an easy-to-use device for the real-time monitoring of meat freshness during transport and storage. Therefore, a novel pH-sensitive anthocyanin indicator film composed of polyvinyl alcohol-blueberry anthocyanin (BA)-2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) called PAH-2.0 with 1.2 mg/mL HACC to monitor meat freshness using HACC as the colorimetric enhancer has been developed. BA and HACC were mixed and immobilized in the polyvinyl alcohol matrix by hydrogen bonds, as confirmed via Fourier-transform infrared spectroscopy and X-ray diffraction. The inclusion of HACC improved the color stability and antioxidant and antibacterial properties of the PAH-2.0 film. When applied to pork for freshness monitoring at 4 °C, three freshness stages, including fresh, sub-fresh, and spoiled, could be clearly distinguished based on the color variations of the PAH-2.0 film. The distinct hierarchical color change from purple to blue-violet and finally to grayish-blue was highly correlated with the indicators of pork freshness: pH values, total volatile basic nitrogen, and total viable count. This study provides a simple and promising approach for fabricating meat freshness indicator films with high color recognition accuracy, thereby offering new possibilities for visual meat freshness monitoring.

Green and renewable thermoplastic polyvinyl alcohol/starch blend film fabricated by melt processing

In this study, the PVA/starch blend films were prepared by dry melting method. The microstructure showed that the starch existed in the continuous PVA matrix in granular structure. When the amount of starch was 30 wt%, the tensile strength increased from 12.8 to 14.7 MPa, and the elastic modulus increased from 15.4 to 20.5 MPa, and the water absorption increased by about 2 %. The addition of starch increased the Tmax by 8.1-29.64 °C compared to pure PVA. Considering the mechanical, hydrophilic and optical properties of the blend films, PVA/starch at 7:3 was the most promising packaging material. Notably, the blend films exhibit great reusability and renewability. Overall, these findings highlight the potential of PVA/starch blend films as environmentally friendly materials with enhanced properties.

Fabrication of high performance poly(vinyl alcohol)/straw composite film used for package via melt casting and biaxial stretching

A high performance poly(vinyl alcohol)/straw (PVA/SP) composite film for package was fabricated in this study by using thermal processing technology of PVA established in our research group and biaxial stretching technology. The introduction of SP disrupted the original hydrogen bonds in modified PVA by forming new hydrogen bonds with the hydroxyl groups of each component in modified system, thus promoting the stable melt casting of PVA/SP composites and also endowing the obtained PVA/SP precursor sheets with good drawability. Upon biaxial stretching, SP reinforced the crystalline structure and orientation of PVA through their hydrogen bonds with PVA, improving the mechanical strength, crystallinity and thermal stability of PVA/SP films. The film with 3.0 × 3.0 stretching ratios demonstrated the exceptional tensile strength (62.2 MPa), tear strength (119.7 kN/m), low heat shrinkage (5.2 %), and oxygen permeability coefficient (1.38 × 10-16 cm3·cm/cm2·s·Pa), which surpassed most conventional plastic films used in food packaging field. This research not only pioneered an environmentally friendly packaging solution, but also offered a novel strategy for solid-state high-value, large-scale and economical utilization of waste crop straw, greatly avoiding the adverse effects of its burning on the environment.

Carboxymethyl cellulose-based photothermal film: A sustainable packaging with high barrier and tensile strength for food long-term antibacterial protection

Traditional packaging materials feed the growing global food protection. However, these packaging materials are not conducive to environment and have not the ability to kill bacteria. Herein, a green and simple strategy is reported for food packaging protection and long-term antibacterial using carboxymethylcellulose-based photothermal film (CMC@CuS NPs/PVA) that consists of carboxymethyl cellulose (CMC) immobilized copper sulfide nanoparticles (CuS NPs) and polyvinyl alcohol (PVA). With satisfied oxygen transmittance (0.03 cc/m2/day) and water vapor transmittance (163.3 g/m2/day), the tensile strength, tear strength and burst strength reached to 3401.2 N/m, 845.7 mN and 363.6 kPa, respectively, which could lift 4.5 L of water. The composite film had excellent photothermal conversion efficiency and photothermal stability. Under the irradiation of near infrared (NIR), it can rapidly heated up to 197 °C within 25 s. The antibacterial analysis showed that the inhibition rate of composite film against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) could all reach >99 %. Furthermore, the synthesized CuS NPs was well immobilized and the residual rate of copper kept 98.7 % after 10 days. Noticeably, the composite film can preserve freshness of strawberries for up to 6 days. Therefore, the composite film has potential application for food antibacterial protection.

Fabrication of a ternary biocomposite film based on polyvinyl alcohol, cellulose nanocrystals, and silver nanoparticles for food packaging

Silver nanoparticles (AgNPs) were loaded on deprotonated cellulose nanocrystals (CNCd) and incorporated into polyvinyl alcohol (PVA) to develop novel active food packaging films. The AgNPs were fabricated using the liquid phase chemical reduction method using the sodium borohydride reductant of AgNO3. The analysis using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), and Ultraviolet-visible spectroscopy (UV-Vis) showed that the CNCd surface had a homogeneous distribution of AgNPs with a diameter of about 100 nm. Additionally, CNCd/Ag was successfully incorporated into the PVA film. The developed PVA/CNCd/Ag film showed significantly improved mechanical properties, thermal stability, and UV barrier properties compared to a neat PVA film. The PVA/CNCd/Ag composite film could significantly preserve bananas for 14 days, preventing deterioration and allowing extended storage periods. This composite film generally shows promise in food packaging and prolongs food's shelf life.

Fabrication of nano filler doped PVA/starch biodegradable composites with enhanced thermal conduction, water barrier and antimicrobial performance for food industry

In this work there was investigated the synergistic effect of the nanomaterials-the Montmorillonite (MMT) and the vanadium pentoxide (V2O5) on the polyvinyl alcohol (PVA)/starch composite. The composite films were prepared by the solvent casting method. The characterization of the composites showed that the addition of the MMT and the V2O5 to PVA/starch composite decreased the water solubility and water absorption capacity of the film. Both of the reinforcement materials enriched values of thermal conductivity and thermal stability of the composite. The TG/DTA and universal testing machine (UTM) analysis exhibited that MMT and V2O5 augmented the thermal robustness and tensile strength of composites and decreased the strain to break. It was also observed that greater MMT concentration accelerates mechanical strength deterioration of the film owing to agglomeration. The scanning electron microscopy (SEM) analysis reflected great change in the surface morphology of the films in the presence and absence of MMT and V2O5. This was due to the interaction amid constituents of the composite. The chemical interaction between the PVA, Starch, MMT and the V2O5 was also established via Fourier-transform infrared spectroscopy (FTIR) analysis, which revealed fluctuations in the absorbance position and intensity of the PVA/Starch. Antimicrobial activities against seven different cultures of bacteria (both-gram positive and -negative) and one fungus (Candida albicans), exposed that antimicrobial performance of the PVA amplified upon addition of the starch, MMT and V2O5, making these composites prospective candidates for the biodegradable packaging materials.

Biodegradable and multifunctional black mulch film decorated with darkened lignin induced by iron ions for "green" agriculture

High-value utilization of bleached lignin has been widely used in different fields, whereas the investigation on darkened lignin in composite materials was often ignored. In this work, a sort of eco-friendly and structurally robust sodium carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA)/sodium lignosulfonate (SLS) black composite mulch film was elaborately designed. The chelation and redox reaction effect between Fe ions and SLS lead to the formation of a more quinones structure on lignin, darkening both lignin and the mulch films. The chelation effect between Fe ions and biopolymer formed three-dimensional structures, which can be used as sacrifice bonds to dissipate energy and improve the mechanical properties of the composite films. In particular, the maximum elongation at break and toughness increased from 48.4 % and 1141 kJ/m3 for the CMC/PVA film to 210.9 % and 1426 kJ/m3 for the optimized CMC/PVA/SLS/Fe black mulch film, respectively. In addition, the optimized black mulch film also possesses good soil water retention, thermal preservation effect, controlled urea release, and well biodegradability. This work offered a novel strategy for designing eco-friendly black mulch with reinforced mechanical strength, slow-release urea, soil moisture retention, and heat preservation performances.

Development of smart packaging film incorporated with sodium alginate-chitosan quaternary ammonium salt nanocomplexes encapsulating anthocyanins for monitoring milk freshness

This study focused on the preparation, functionality, and application of smart food packaging films based on polyvinyl alcohol (PVA) and anthocyanins (ACNs) -loaded sodium alginate-chitosan quaternary ammonium salt (HACC-SA) nanocomplexes. The average encapsulation rate of anthocyanins-loaded nanocomplexes reached 62.51 %, which improved the hydrophobicity and water vapor barrier of the PVA film. FTIR confirmed that the nanocomplexes were immobilized in the PVA film matrix by hydrogen bonding, which improved the mechanical properties of the film. The SEM and XRD results demonstrated that the HACC-SA-ACNs nanocomplexes were uniformly distributed in the film matrix and the crystallinity of PVA was decreased. The P/HACC-SA-ACNs film showed a significant response to buffers of pH 2-13 and high color stability after 21 days of storage compared to the P/ACNs film. Furthermore, the color of the composite film changed from purple to red as the milk freshness decreased during 72 h of milk freshness monitoring, indicating that the P/HACC-SA-ACNs films were suitable and promising for application as smart packaging materials.

Fabrication of biodegradable and cold-water-soluble starch/polyvinyl alcohol films as inner packaging materials of pesticides: Enhanced emulsification, dispersibility, and efficacy

Developing environmentally friendly film materials for packaging pesticides is significant yet challenging. The use of native starch for preparing inner packaging materials of pesticides is limited by its physicochemical properties. In this study, a novel strategy of synergetic mechanical activation (MA)-enhanced solid-phase esterification of starch and cooperative combination of starch and polyvinyl alcohol (PVA) was proposed to fabricate biodegradable and cold-water-soluble starch (St)/PVA films. The appropriate esterification of starch and favorable compatibility between starch and PVA contributed to the production of St/PVA films by the extrusion-blowing method. The as-prepared film with St/PVA ratio of 4:6 exhibited outstanding mechanical properties (tensile strengths of 21.0 MPa; elongation at break of 213.9 %), cold-water solubility (dissolution time of 90 s), and oxygen barrier performance (oxygen transmission rate of 1.41 cm3/(m2·day·bar)). The dissolved St/PVA films with amphiphilic groups were conducive to the emulsification of butachlor (a fat-soluble liquid pesticide) and the dispersibility of oxyfluorfen (a fat-soluble solid pesticide). Furthermore, a mechanism of the interaction between pesticides and the surface of weed leaves was proposed to reveal the enhanced efficacy of St/PVA films-packaged pesticides. The strategy based on MA-enhanced esterification and PVA blending is efficient to produce starch-based films suitable for inner packaging materials of pesticides.

High transparency, water vapor barrier and antibacterial properties of chitosan/carboxymethyl glucan/poly(vinyl alcohol)/nanoparticles encapsulating citral composite film for fruit packaging

Utilizing antibacterial packaging material is an effective approach to delay fruit rotting and spoilage thereby minimizing financial losses and reducing health harm. However, the barrier and mechanical properties of biodegradable antibacterial packaging materials are barely compatible with transparency. Herein, antimicrobial nanoparticles encapsulating citral (ANPs) were first prepared by emulsification under the stabilization of oxidized dextran (ODE) and ethylene diamine. Then, composite films with high transparency, good water vapor barrier, and mechanical and antibacterial properties for fruits packaging were prepared from chitosan (CS), carboxymethyl-glucan (CMG), poly(vinyl alcohol) (PVA), and ANPs by solvent casting strategy. The synergistic effects of electrostatic interaction and hydrogen bonding could regulate crystalline architecture, generating high transparency of the composite films (90 %). The mechanical properties of the composite film are improved with elongation at break up to 167 % and stress up to 32 MPa. The water vapor barrier property of the film is appropriate to the packed fruit for less weight loss and firmness remaining. Simultaneously, the addition of ANPs endowed the film with excellent antimicrobial and UV-barrier capabilities to reduce fruit mildew, thereby extending the shelf life of fruits. More importantly, the composite polymer solution could be sprayed or dipped directly on fruits as a coating for food storage to improve food shelf life, substantially expanding its ease of use and scope of use.

Synthesis and Characterization of Cellulose Microfibril-Reinforced Polyvinyl Alcohol Biodegradable Composites

The pursuit of an environmentally sustainable manufacturing process requires the substitution of less damaging and recyclable solutions for harmful reagents. This study aims to assess the effectiveness of using cellulose microfibrils synthesized via different hydrolysis reactions as reinforcing agents in polyvinyl alcohol (PVA) at varying concentrations. The investigation explores the morphology, thermal properties, and chemical behavior of the cellulose particles. The cellulose microfibrils (CMFs) produced using citric acid exhibited the highest yield and aspect ratio. Notably, particles from organic acids demonstrated greater thermal stability, with oxalic acid-derived particles displaying the maximum thermal degradation temperature. Subsequently, cast films of PVA reinforced with the cellulose microfibrils underwent comprehensive analyses, including Fourier transfer infrared (FTIR) spectroscopy, thermal degradation temperature (Td), differential scanning calorimetry (DSC), and tensile strength tests. The thermal behavior of cast films experienced notable changes with the addition of cellulose particles, evidenced by increased melting and crystallinity temperatures, along with a rise in the degree of crystallinity. The incorporation of cellulose particles led to a substantial improvement in mechanical properties. Films containing CMF displayed higher Young's modulus, and the sample incorporating 5% CMF derived from citric acid exhibited the most significant increase in modulus.

Development, characterization and application of starch-based film containing polyphenols of piper betle L. waste in chicken meat storage

The current study aimed to develop a sustainable solution to extend the shelf life of chicken meat by developing starch-based functional film embedded with polyphenolic extract of waste petioles of betel leaf (BLP). The results showed that loading of the extract significantly (p < 0.05) improved flexibility, thickness, water solubility, DPPH radical scavenging activity, and UV light protection ability by enhancing intermolecular interactions among potato starch, guar gum, and the extract. The developed film showed optimum mechanical and water barrier properties at a 4% BLP extract concentration computed through TOPSIS method (A multi-criteria decision-making approach). During the shelf life study, the extract embedded film maintained the quality of chicken meat for up to 12 days at refrigerated temperature. Biodegradation time of the extract-blended films was considerably decreased to 14 days from 28 days for the native film, indicating suitable alternative to non-biodegradable film for storing the raw meat.

Fabrication of Bio-Nanocomposite Packaging Films with PVA, MMt Clay Nanoparticles, CNCs, and Essential Oils for the Postharvest Preservation of Sapota Fruits

Sapota is an important climacteric fruit with limited shelf life. A special system must be employed to extend the shelf life of sapota fruits. In the present study, polyvinyl alcohol (PVA) and montmorillonite clay (MMt)-based bio-nanocomposite films (BNFs) were integrated at various concentrations (2%, 4%, 6%, and 8%) into cellulose nanocrystals (CNCs), produced from garlic peels (GPs). The BNF loaded with 8% CNC has a better crystallinity index and mechanical properties than the other concentrations of CNC. Therefore, the 8% CNC-incorporated BNF (BNF-8) was selected for further packaging studies. The combined effect of BNF-8 with ajwain essential oil (AO) and oregano essential oil (OO) vapors and BNF-8 with carbendazim (commercial fungicide-CARB) were investigated. In this study, the BNF-based packagings are categorized into five types, viz: BNF+8% CNC (BNF-8), BNF-8+AO, BNF-8+OO, BNF-8+CARB and the non-packaged fruits (control). The shelf-life duration, antioxidant activity, firmness, decay index, and sensory quality were evaluated in order to identify the effectiveness of packaging treatment on sapota fruits. BNF-8+CARB, BNF-8+AO, and BNF-8+OO packaging extended the shelf life of sapota fruits to up to 12 days and maintained the overall physiochemical parameters and sensory qualities of the fruits. Therefore, the BNF-8+AO and BNF-8+OO packaging materials are appropriate alternatives to commercial fungicides for the preservation of sapota during postharvest storage.

Direct-Writing Flexible Metal Circuit with Polymer/Metal Precursor Ink and Interfacial Reaction

In this study, flexible metal circuits are fabricated with polymer/metal precursor ink and an interfacial reaction by direct-writing technology. Poly(vinyl alcohol) (PVA) is selected as one component of ink, which could be a flexible composite in a metal circuit and an adhesive layer to connect the flexible metal circuit with the flexible substrate. Silver nitrate (AgNO₃) is added to the ink as a source of metal. After the direct-writing structure was placed in contact with an ascorbic acid (VC) aqueous solution with an adjustable process, silver nanoparticles (AgNPs) with 100-400 nm uniform size could be generated on the direct-writing PVA skeleton. The resistivity of the composite silver layer could reach 10^-6 Ω·m without any postprocessing. Meanwhile, the resistance change could keep within 20% with 180° bending after 10 000 repeat times. Patterned flexible metal circuits could be facilely fabricated by direct-writing technology, which presented excellent electrical conductivity and flexibility.

Formulation and stabilization of high internal phase emulsions: Stabilization by cellulose nanocrystals and gelatinized soluble starch

In this work, high internal phase emulsions (HIPEs) stabilized by naturally derived cellulose nanocrystals (CNC) and gelatinized soluble starch (GSS) were fabricated to stabilize oregano essential oil (OEO) in the absence of surfactant. The physical properties, microstructures, rheological properties, and storage stability of HIPEs were investigated by adjusting CNC contents (0.2, 0.3, 0.4 and 0.5 wt%) and starch concentration (4.5 wt%). The results revealed that CNC-GSS stabilized HIPEs exhibited good storage stability within one month and the smallest droplets size at a CNC concentration of 0.4 wt%. The emulsion volume fractions of 0.2, 0.3, 0.4 and 0.5 wt% CNC-GSS stabilized HIPEs after centrifugation reached 77.58, 82.05, 94.22, and 91.41 %, respectively. The effect of native CNC and GSS were analyzed to understand the stability mechanisms of HIPEs. The results revealed that CNC could be used as an effective stabilizer and emulsifier to fabricate the stable and gel-like HIPEs with tunable microstructure and rheological properties.

Multifunctional nanocomposite based on polyvinyl alcohol, cellulose nanocrystals, titanium dioxide, and apple peel extract for food packaging

Although polyvinyl alcohol (PVA) is a potential biodegradable food packaging material, it has several critical limitations: low mechanical strength, poor ultraviolet (UV) and water vapor barrier properties, and lack of antioxidant and antimicrobial properties. Previous studies have used cellulose nanocrystals (CNCs) to improve the mechanical and water vapor barrier properties of the PVA matrix. In this study, a multifunctional nanocomposite for food packaging applications was developed by incorporating titanium dioxide (TiO₂) and apple peel extract (APE) into a PVA/CNC matrix. The combination of TiO₂ and APE in the nanocomposites not only enhanced multifunctionality but also improved mechanical and barrier properties. The mechanical strength and water vapor barrier properties of PVA/CNC/TiO₂/APE (5 wt% TiO₂ and 20 wt% APE in the PVA/CNC matrix containing 5 wt% of CNCs) increased by 49.9 % and 36.6 % compared to PVA. Furthermore, PVA/CNC/TiO₂/APE exhibited an excellent UV barrier (UV-protection factor of 1012.73) and high antioxidant and antimicrobial properties. In food packaging tests with fresh cherry tomatoes and potatoes, PVA/CNC/TiO₂/APE effectively protected samples from external influences and prolonged their self-life, demonstrating the potential use of this nanocomposite as a biodegradable and multifunctional food packaging material.

Nanobacterial Cellulose Production and Its Antibacterial Activity in Biodegradable Poly(vinyl alcohol) Membranes for Food Packaging Applications

Nanobacterial cellulose (NBC) was produced and incorporated into biodegradable poly(vinyl alcohol) (PVA) in different weight ratios to obtain polymer nanocomposite membranes. The physicochemical properties of the membranes were studied using Fourier transform infrared (FTIR) spectroscopy, a universal testing machine (UTM), thermogravimetric analysis (TGA), wide-angle X-ray diffraction (WAXD) techniques, and field emission scanning electron microscopy (FESEM). FTIR confirmed the consolidation of NBC into PVA by exhibiting significant changes in the peaks compared to NBC and PVA individually. The highest tensile strength of 53.33 MPa and 235.30% elongation at break of the membrane M-10 mass % NBC was obtained, illuminating that NBC provides stiffness and PVA imparts elasticity. WAXD revealed that the crystalline nature of the membrane increases up to 10 mass % and decreases beyond it. The effect of NBC on the poly(vinyl alcohol) membranes for food packaging was investigated systematically. Among all the membranes, M-10 mass % NBC was found to be the most suitable for packaging applications. Membranes had antimicrobial activity against food microbes and showed degradability behavior in the soil. The tests on membranes for packaging revealed that fruits were protected from spoilage caused by microorganisms. Hence, the prepared membranes could be used as an alternative to conventional plastics for packaging applications.

Optimizing Biodegradable Starch-Based Composite Films Formulation for Wound-Dressing Applications

This paper utilizes response surface methodology (RSM) design-based analyses to optimize starch-based wound dressings that were characterized based on weight loss (WL%), swelling index (SI%), and mechanical strength (TS). The wound-dressing materials were prepared by employing a modified casting method, using various concentrations of starch (0.5-2 w/w%), polyvinyl alcohol (PVA) (0.5-2 weight%), citric acid (1.5-4 weight%), and glycerol (1.5-4 weight%) to yield wound-dressing films with appropriate combinations of in vitro degradation, swelling index, and tensile strength. As a result of the response surface method-based analysis, the swelling index, in vitro degradation, and tensile strength were linearly related to variations in the formulation of organic components. Based on our experimental investigations, the optimized film (formulation: 1 weight% PVA, 2 weight% starch, 1.5 weight% citric acid, and 1.5 weight% glycerol) exhibited an outstanding swelling index (343.52%), suitable in vitro degradation (53.22%), and excellent tensile strength (8.82 MPa). The response surface plots for the dependent variables, swelling index (SI%), weight loss (WL%), and mechanical strength (TS), showed that in all dual relations, the PVA-starch combination significantly affected all dependent variables; however, the PVA-citric acid interaction showed the most excellent effect on the swelling index. As a result, every component of the resulting film had a lesser amount of all ingredients to achieve better properties at a lower material cost. Starch-based/PVA films have been identified in this paper as optimal and more affordable wound-dressing films.

Effects of starch/polyvinyl alcohol active film containing cinnamaldehyde on the quality of large yellow croaker (Pseudosciaena crocea) proteins during frozen storage

This study aimed to investigate the effects of starch/polyvinyl alcohol (starch/PVA) film containing cinnamaldehyde (CIN) with different humidity treatment on the quality changes of large yellow croaker (Pseudosciaena crocea) under vacuum packaging during frozen storage. It was evaluated by measuring the water loss, water migration, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), free amino acids (FAA) content, myofibril secondary and tertiary structure and microstructure of large yellow croaker. Compared with control group, the starch/PVA films could inhibit the water loss, water migration, protein degradation, lipid oxidation and microstructure damage of fish. The film containing CIN with higher humidity treatment showed the best protective effect for large yellow croaker. The film with higher humidity treatment showed better to maintain the quality of fish than that with low humidity treatment. Therefore, starch/PVA active film containing CIN with high humidity treatment showed good fresh-keeping potential in the frozen storage of aquatic products.

Enteromorpha cellulose micro-nanofibrils/poly(vinyl alcohol) based composite films with excellent hydrophilic, mechanical properties and improved thermal stability

This study presents the preparation of cellulose micro-nanofibrils (CMNFs) from Enteromorpha (EP) and the application in PVA/acetylated distarch phosphate (ADSP)/CMNFs composite films. The Micro-nano scale, hydrophilicity, and strong hydrogen bond characteristics of CMNFs prepared form EP by acid hydrolysis were confirmed through the granular statistics, XRD analysis and chemical structure analysis. With the addition of CMNFs, the ultimate tensile strength and elongation at break of composite films are increased by 42.4 % and 90.3 %. An original Weibull statistical analysis shows the impact of CMNFs' added amount on strength distribution and ultimate stress. SEM and polarizing microscope images show the CMNFs' dispersion state in that films is optimal, when their addition was to be 2 %-3 % of total dry weight of PVA/ADSP matrix， which is consistent with the results of Weibull modulus analysis. The main thermal weight-loss process of the composite film is divided into four stages, CMNFs can significantly increase the thermostability at 280 °C to 400 °C. The experiment of water contact angle and water vapor transmission rate of the composite films confirmed that CMNFs can improve films' hydrophilicity. This study provides basis for the preparation of hydrophilic CMNFs and mechanism of modification study PVA-based composites.

Antibacterial and hemostatic capacities of cellulose nanocrystalline-reinforced poly(vinyl alcohol) electrospun mats doped with Tiger 17 and pexiganan peptides for prospective wound healing applications

Infection is a major issue in chronic wound care. Different dressings have been developed to prevent microbial propagation, but an effective, all-in-one (cytocompatible, antimicrobial and promoter of healing) solution is still to be uncovered. In this research, polyvinyl alcohol (PVA) nanofibrous mats reinforced with cellulose nanocrystal (CNC), at 10 and 20% v/v ratios, were produced by electrospinning, crosslinked with glutaraldehyde vapor and doped with specialized peptides. Crosslinking increased the mats' fiber diameters but maintained their bead-free morphology. Miscibility between polymers was confirmed by Fourier-transform infrared spectroscopy and thermal evaluations. Despite the incorporation of CNC having reduced the mats' mechanical performance, it improved the mats' surface energy and its structural stability over time. Pexiganan with an extra cysteine group was functionalized onto the mats via hydroxyl- polyethylene glycol 2-maleimide, while Tiger 17 was physisorbed to preserve its cyclic conformation. Antimicrobial assessments demonstrated the peptide-doped mat's effectiveness against Staphylococcus aureus and Pseudomonas aeruginosa; pexiganan contributed mostly for such outcome. Tiger 17 showed excellent capacity in accelerating clotting. Cytocompatibility evaluations attested to these mats' safety. C90/10 PVA/CNC mats were deemed the most effective from the tested group and, thus, a potentially effective option for chronic wound treatments.

Tiger 17 and pexiganan as antimicrobial and hemostatic boosters of cellulose acetate-containing poly(vinyl alcohol) electrospun mats for potential wound care purposes

In this research, we propose to engineer a nanostructured mat that can simultaneously kill bacteria and promote an environment conducive to healing for prospective wound care. Polyvinyl alcohol (PVA) and cellulose acetate (CA) were combined at different polymer ratios (100/0, 90/10, 80/20% v/v), electrospun and crosslinked with glutaraldehyde vapor. Crosslinked fibers increased in diameter (from 194 to 278 nm), retaining their uniform structure. Fourier-transform infrared spectroscopy and thermal analyses proved the excellent miscibility between polymers. CA incorporation incremented the fibers swelling capacity and reduced the water vapor and air permeabilities of the mats, preventing the excessive drying of wounds. The antimicrobial peptide cys-pexiganan and the immunoregulatory peptide Tiger 17 were incorporated onto the mats via polyethylene glycol spacer (hydroxyl-PEG2-maleimide) and physisorbed, respectively. Time-kill kinetics evaluations revealed the mats effectiveness against Staphylococcus aureus and Pseudomonas aeruginosa. Tiger 17 played a major role in accelerating clotting of re-calcified plasma. Data reports for the first time the collaborative effect of pexiganan and Tiger 17 against bacterial infections and in boosting hemostasis. Cytocompatibility data verified the peptide-modified mats safety. Croslinked 90/10 PVA/CA mats were deemed the most promising combination due to their moderate hydrophilicity and permeabilities, swelling capacity, and high yields of peptide loading.

Effect of Melissa officinalis L. Essential Oil Nanoemulsions on Structure and Properties of Carboxymethyl Chitosan/Locust Bean Gum Composite Films

This study aimed to develop active films based on carboxymethyl chitosan (CMCS)/locust bean gum (LBG) films containing Melissa officinalis L. essential oil (MOEO) nanoemulsions. The results showed that the active films incorporated with MOEO nanoemulsion resulted in an increase in the elongation of break, water resistance and improved the film hydrophilicity. Elongation of break increased from 18.49% to 27.97% with the addition of 4% MOEO nanoemulsion. Water resistance was decreased from 56.32% to 25.43%, and water contact angle was increased from 75.13 to 83.86 with the addition of 4% MOEO nanoemulsion. However, the water vapor barrier properties and tensile strength decreased with the addition of MOEO nanoemulsions. The scanning electron microscopic images and Fourier transform infrared spectroscopy results showed that the MOEO was very compatible with the film materials and dispersed evenly in the films. At the same time, the addition of MOEO nanoemulsion significantly enhanced antioxidant and antibacterial activities of C/L-MOEO films. The antioxidant and antimicrobial activities of C/L-MOEO films were increased from 7.16% to 33.81% and 3.52% to 54.50%, respectively. In general, C/L-MOEO film has great application prospects.

Polyvinyl alcohol/cellulose nanocrystals/alkyl ketene dimer nanocomposite as a novel biodegradable food packing material

Polyvinyl alcohol (PVA) is used in many applications because of its excellent physicochemical properties, non-toxicity, and biodegradability. However, its relatively low water resistance, poor water vapor/ultraviolet (UV) barrier properties, and poor mechanical properties compared with conventional polymers limit its applications in food packaging. In this study, cellulose nanocrystals (CNCs) and alkyl ketene dimer (AKD) were used to overcome these issues. The mechanical properties, water resistance, and barrier properties of the developed PVA/CNC/AKD films were significantly improved relative to those of a neat PVA film. The mechanical strength of a PVA/CNC/AKD 15% film (15 wt% AKD in a PVA/CNC matrix of 5 wt% CNCs) was 64.6% and 37% higher than those of PVA and PVA/CNC films, respectively. The water vapor transmission rate, water absorption, and solubility of PVA/CNC/AKD 15% were 41.2%, 61.1%, and 92.9%, respectively (lower than those of the neat PVA film). In addition, the UV barrier properties and soil degradation of the PVA/CNC/AKD films were significantly improved.

Effect of Plasticizer Content on Mechanical and Water Vapor Permeability of Maize Starch/PVOH/Chitosan Composite Films

Packaging materials based on biodegradable polymers are a viable alternative to replace conventional plastic packaging from fossil origin. The type of plasticizer used in these materials affects their functionality and performance. The effect of different plasticizers such as glycerol (GLY), sorbitol (SOR), and poly(ethylene glycol) (PEG) in concentrations of 5%, 10%, and 15% (w/w) on the structural features and functional properties of starch/PVOH/chitosan films was evaluated. The incorporation of a plasticizer increased the thickness of the biodegradable composite films. Furthermore, the material plasticized with 30% (w/w) sorbitol had the highest elongation at break, lowest water vapor permeability, and better thermal resistance. The results obtained in this study suggest that maize starch/PVOH/chitosan biodegradable composite films are a promising packaging material, and that sorbitol is the most suitable plasticizer for this formulation.

Compatibilization of Starch/Synthetic Biodegradable Polymer Blends for Packaging Applications: A Review

The health and environmental concerns of the usage of non-biodegradable plastics have driven efforts to explore replacing them with renewable polymers. Although starch is a vital renewable polymer, poor water resistivity and thermo-mechanical properties have limited its applications. Recently, starch/synthetic biodegradable polymer blends have captured greater attention to replace inert plastic materials; the question of ‘immiscibility’ arises during the blend preparation due to the mixing of hydrophilic starch with hydrophobic polymers. The immiscibility issue between starch and synthetic polymers impacts the water absorption, thermo-mechanical properties, and chemical stability demanded by various engineering applications. Numerous studies have been carried out to eliminate the immiscibility issues of the different components in the polymer blends while enhancing the thermo-mechanical properties. Incorporating compatibilizers into the blend mixtures has significantly reduced the particle sizes of the dispersed phase while improving the interfacial adhesion between the starch and synthetic biodegradable polymer, leading to fine and homogeneous structures. Thus, Significant improvements in thermo-mechanical and barrier properties and water resistance can be observed in the compatibilized blends. This review provides an extensive discussion on the compatibilization processes of starch and petroleum-based polymer blends.

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.

Development and characterization of PVA-starch incorporated with coconut shell extract and sepiolite clay as an antioxidant film for active food packaging applications

An active antioxidant film was fabricated by using polyvinyl alcohol (PVA) and corn starch (ST) and incorporated with and 3, 5, 10, and 20% (v/v) coconut shell extract (CSE) and sepiolite clay (SP) for the first time. The microstructure and physical properties of prepared films were characterized and examined. The addition of sepiolite clay to PVA improved the elongation break 15.57 to 69.24%, and water vapor permeability increased with the addition of CSE. In addition to CSE to films, the antioxidant activity properties of the films were enhanced up to 80%. Further, increasing the amount of CSE slightly affected the color of the active films. The thermal properties of films were enhanced with the addition of CSE and SP. The dispersion of SP in the PVA matrix was affected by an increase in CSE concentration in the PVA matrix. Remarkably, PVA-ST film-based sachets successfully improved the oxidative stability of packaged soybean oil. Our results suggest PVA-ST film containing CSE and sepiolite clay can be utilized as a novel antioxidant packaging material in the food processing industry.

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.

Self-assembling crystals of an extract of Flos Sophorae Immaturus for improving the antioxidant, mechanical and barrier properties of a cassia gum film

A novel antioxidative film was prepared by drying a film-forming solution containing the Flos Sophorae Immaturus extract (FSIE) (0-3.5%) and cassia gum (CG). Scanning electron microscopy (SEM) showed that FSIE was successfully compounded with CG. Although the addition of FSIE slightly increased the water vapor permeability (WVP) and O₂ permeability (OP) of the film, it also improved its ability to block ultraviolet light significantly. The appropriate amounts of FSIE increased the tensile strength (TS) from 20.9 MPa to 30.2 MPa but reduced the elongation at break (EB) from 38.7% to 27.6%. The films doped with FSIE exhibited strong antioxidative activity and high rates of free radical scavenging. Total phenols exhibited a positive trend as the amount of FSIE increased in 50% of ethanol. The practical application of these composite films was investigated by evaluating the quality of lard wrapped in the films. After 25 d, the acid value (X_AV) and peroxide value (POV) of lard packaged in CG/FSIE2% were lower than the values for lard packaged in CG/FSIE0% and plastic bag. These results showed that the CG/FSIE film had superior antioxidative activity compared to films made from plastic and pure CG.

Development and characterization of corn starch/PVA active films incorporated with carvacrol nanoemulsions

An active film was prepared by corn starch (CS), polyvinyl alcohol (PVA) and carvacrol nanoemulsions (CNE). The microstructure and properties of CNE/corn starch/PVA (CNE/CSP) films were characterized and investigated. Scanning electron microscopy (SEM) revealed the uniform distribution of CNE and discontinuity of the film matrix. Fourier transform infrared (FT-IR) and rheological analysis indicated that CNE could weaken molecular interaction of the film matrix. X-ray diffraction (XRD) show that the films are amorphous and CNE has no effect on crystal structure of the films. Incorporation of CNE significantly increased the tensile strength, Young's modulus, elongation at break, barrier (water vapor and ultraviolet), antioxidant and antifungal activity. With the CNE incorporated, the optimal tensile strength, Young's modulus, elongation at break and antioxidant activity of the films can reach 12 MPa, 11 MPa, 133%, 81%, respectively. Minimum water vapor permeability was 3.1 × 10^-12 gd^-1m^-1Pa^-1. Notably, films incorporated with CNE (≥20%) had good DPPH free radical scavenging ability (>50%) when stored up to 6 days. Films with 25% CNE exhibited excellent antifungal activity against Trichoderma sp. and its inhibitory zone was 47 mm. Overall, the CSP films loaded with CNE (>15%) could be used as food packing materials with good antioxidant and antimicrobial activities.

Evaluation of multifunctional properties of gallic acid crosslinked Poly (vinyl alcohol)/Tragacanth Gum blend films for food packaging applications

The natural polymer Tragacanth Gum is less explored as a supporting matrix, there are very less studies conducted using this polymer in literature. So the present study aims to explore the consequences of different weight percent (wt.%) of gallic acid (GA) on physicochemical properties of Poly (vinyl alcohol)/Tragacanth Gum blend films. The incorporation of GA resulted in more strengthened but less flexible films as confirmed by tensile tests. DSC studies confirmed the miscibility of composite films in the given composition range and TGA studies revealed increased thermal stability. The morphological studies revealed a homogeneous distribution of GA at lower wt.% in the blend system. X-Ray Diffraction study depicted; the added GA lost crystalline structure after incorporating it into the blend. The Water Vapor Transmission Rate (WVTR) was improved after the incorporation of GA into the blend system. Overall migration studies revealed the limited release of GA from the matrix into food simulants. Soil degradation rate increased as the wt.% of GA increased. The composite films presented strong antioxidant activity; therefore, prepared composite films could be used as an alternative to current packaging materials.