Preparation and Characterization of Antioxidative and UV-Protective Larch Bark Tannin/PVA Composite Membranes

Development of an UV-Resistant Multilayer Film with Enhanced Compatibility between Carboxymethyl Cellulose and Polylactic Acid via Incorporation of Tannin and Ferric Chloride

Carboxymethyl cellulose (CMC) and polylactic acid (PLA) are recognized for their environmental friendliness. By merging them into a composite film, packaging solutions can be designed with good performance. Nonetheless, the inherent interface disparity between CMC and PLA poses a challenge, and there may be layer separation issues. This study introduces a straightforward approach to mitigate this challenge by incorporating tannin acid and ferric chloride in the fabrication of the CMC-PLA. The interlayer compatibility was improved by the in situ formation of a cohesive interface. The resulting CMC/TA-PLA/Fe multilayer film, devoid of any layer separation, exhibits exceptional mechanical strength, with a tensile strength exceeding 70 MPa, a high contact angle of 105°, and superior thermal stability. Furthermore, the CMC/TA-PLA/Fe film demonstrates remarkable efficacy in blocking ultraviolet light, effectively minimizing the discoloration of various wood surfaces exposed to UV aging.

Effect of post-heat treatment on the UV transmittance, hydrophobicity, and tensile properties of PVA/Uncaria gambir extract blend films

The physical and mechanical properties of biopolymers can be improved by heating technologies. In this research, we improved the properties of Polyvinyl alcohol (PVA)/Uncaria gambir extract (UGE) blend films by post-heating method. After post-heating, the blend film exhibited higher resistance to UV light and improved contact angle performance, while water vapor permeability and moisture absorption decreased. The tensile strength and toughness of the PVA/UGE blend film with a post-heating duration of 40 min were 68.8 MPa and 57.7 MPa, respectively, an increase of 131 % and 127 %, compared to films without post-heating. This facile and cost-effective fabrication method, with environmentally friendly properties, can be applied to biodegradable PVA/UGE blend films to achieve desired properties for optical devices or food packaging materials.

Antioxidant and UV-blocking activity of PVA/tannin-based bioplastics in food packaging application

In this study, bioplastics with antioxidant and UV protection properties based on tannin and PVA were created for packaging uses. Using a hot water extraction method at various extraction temperatures (60-100 °C), tannins were removed from the bark of Acacia mangium. Tannins with the best antioxidant activity were extracted at 80 °C. In order to create bioplastic formulations (PVA/Tannins), the extract is then employed. The non-heating bioplastic method's preparation (M3) stage produced the highest levels of antioxidant activity. Therefore, subsequent tests were conducted using the non-heating method (M3). On the opacity, UV protective activity, antioxidant capacity, mechanical strength, thermal stability, and water vapor permeability of the resultant bioplastics, the impact of tannin concentration (0.1-0.5 g) was examined. The findings of the experiments demonstrate that PVA/Tannin bioplastics are less transparent than pure PVA. The PVA/tannin bioplastics that are formed, on the whole, show strong antioxidant and UV protection action. Comparing PVA/Tannin bioplastics to pure PVA also revealed a small improvement in thermal stability and tensile strength. In PVA bioplastics with resistant tannins, moisture content was marginally greater even at low tannin concentrations (0.1 g). Based on the findings, bioplastics made from PVA and the tannin A. mangium have the potential to be used to create packaging that is UV and active antioxidant resistant. It can be applied as the second (inner) layer of the primary packaging to protect food freshness and nutrition due to their antioxidant activity.

Experimental investigations on PVA/chitosan and PVA/chitin films for active food packaging using Oxytenanthera abyssinica lignin nanoparticles and its UV-shielding, antimicrobial, and antiradical effects

This study investigated the effect of adding lignin nanoparticles (LNPs) derived from Oxytenanthera abyssinica via alkali-acid nanoprecipitation method to polyvinyl alcohol/chitosan (PVA/CI) and polyvinyl alcohol/chitin (PVA/CH) films for the active food packaging applications. Adding LNPs at concentrations of 1 % and 3 % improved the films' thermal stability and mechanical properties. The lowest water solubility and moisture content were observed in PVA/CI/LNPs films. LNPs exhibited effective 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, with the highest values observed in PVA/CH/LNPS and PVA/CI/LNPS films with values of 87.47 and 88.74 % respectively. The addition of LNPs also improved the UV-blocking abilities of the films. PVA/CH/LNP3 and PVA/CI/LNP3 have the smallest percentage transmission values of 3.34 % and 0.86 % in the UV range. The overall migration of dietary stimulants was lower in PVA/CI/LNPS and PVA/CH/LNPS films compared to PVA film. Antibacterial tests demonstrated the inhibitory capacity of the synthesized biofilms against both gram-positive and negative bacterial species, with the highest inhibitory value of 26 mm. The study suggests that PVA/CH/LNPS and PVA/CI/LNPS films have potential applications as active food packaging materials and can be explored in other potential applications such as drug delivery, tissue engineering, wound healing, and slow-release urea fertilizer development.

Sustainable Starch/Lignin Nanoparticle Composites Biofilms for Food Packaging Applications

Construction of sustainable composite biofilms from natural biopolymers are greatly promising for advanced packaging applications due to their biodegradable, biocompatible, and renewable properties. In this work, sustainable advanced food packaging films are developed by incorporating lignin nanoparticles (LNPs) as green nanofillers to starch films. This seamless combination of bio-nanofiller with biopolymer matrix is enabled by the uniform size of nanofillers and the strong interfacial hydrogen bonding. As a result, the as-prepared biocomposites exhibit enhanced mechanical properties, thermal stability, and antioxidant activity. Moreover, they also present outstanding ultraviolet (UV) irradiation shielding performance. As a proof of concept in the application of food packaging, we evaluate the effect of composite films on delaying oxidative deterioration of soybean oil. The results indicate our composite film could significantly decrease peroxide value (POV), saponification value (SV), and acid value (AV) to delay oxidation of soybean oil during storage. Overall, this work provides a simple and effective method for the preparation of starch-based films with enhanced antioxidant and barrier properties for advanced food packaging applications.

Recent Advances in the Investigation of Poly(lactic acid) (PLA) Nanocomposites: Incorporation of Various Nanofillers and their Properties and Applications

Poly(lactic acid) (PLA) is considered the most promising biobased substitute for fossil-derived polymers due to its compostability, biocompatibility, renewability, and good thermomechanical properties. However, PLA suffers from several shortcomings, such as low heat distortion temperature, thermal resistance, and rate of crystallization, whereas some other specific properties, i.e., flame retardancy, anti-UV, antibacterial or barrier properties, antistatic to conductive electrical characteristics, etc., are required by different end-use sectors. The addition of different nanofillers represents an attractive way to develop and enhance the properties of neat PLA. Numerous nanofillers with different architectures and properties have been investigated, with satisfactory achievements, in the design of PLA nanocomposites. This review paper overviews the current advances in the synthetic routes of PLA nanocomposites, the imparted properties of each nano-additive, as well as the numerous applications of PLA nanocomposites in various industrial fields.

Qualitative Analysis on the Phytochemical Compounds and Total Phenolic Content of Cissus hastata (Semperai) Leaf Extract

Plant extracts of Cissus hastata, indigenously known as Semperai, have been used as an effective traditional remedy against coughs. Recently, the leaf extract was potentially shown to have anti-hemorrhoid activity, although there is a lack of scientific data due to its folklore usage. Hence, the therapeutic properties of the phytochemicals and metabolites of Semperai remain elusive. Therefore, this study aims to determine the total phenolic content and phytochemical compounds of the plant leaf extract. Total phenolic content and antioxidant activity were determined by the Folin–Ciocalteau method and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, respectively. Phytochemical compounds present in the leaf methanol extract were analyzed by a qualitative method. Results showed the extract comprised a total of 21.3 mg GAE/g of phenolic content with reference to gallic acid. The antioxidant activity was almost absence with an IC50 of 7.80 µg/mL when compared to trolox and gallic acid. Presence of the red to orange precipitate in reference to gallic acid indicate alkaloid content, while the appearance of black-blue/green color in reference to gallic acid are referred to as tannins. The steroids were represented by an upper red layer and a yellowish sulfuric acid with green fluorescence in comparison to cholesterol. Nonetheless, saponin was not detected in the extract, as indicated by the absence of the persisting foam in the test solution when compared with sodium dodecyl sulphate. In conclusion, despite not having an antioxidant property, the methanol extract of Semperai comprised a fair amount of phenolic compounds, including tannins, alkaloids, and steroids, which, potentially, are highly anti-inflammatory towards hemorrhoids.

One-Step Synthesis of Lignin-Based Triblock Copolymers as High-Temperature and UV-Blocking Thermoplastic Elastomers

This work utilizes frustrated Lewis pairs consisting of tethered bis-organophosphorus superbases and a bulky organoaluminum to furnish the highly efficient synthesis of well-defined triblock copolymers via one-step block copolymerization of lignin-based syringyl methacrylate and n-butyl acrylate, through di-initiation and compounded sequence control. The resulting thermoplastic elastomers (TPEs) exhibit microphase separation and much superior mechanical properties (elongation at break up to 2091 %, tensile strength up to 11.5 MPa, and elastic recovery up to 95 % after 10 cycles) to those of methyl methacrylate-based TPEs. More impressively, lignin-based tri-BCPs can maintain TPEs properties up to 180 °C, exhibit high transparency and nearly 100 % UV shield, suggesting potential applications in temperature-resistant and optical devices.

Quantitative Analysis of Solubility Parameters and Surface Properties of Larch Bark Proanthocyanidins

Quantitative characterization of the solubility parameters and surface properties of larch bark proanthocyanidins will lay the foundation for quantitative studies of the interfacial interactions of proanthocyanidin/polymer composites and will improve the compatibility of components, with important practical and scientific significance. Here, the solubility parameters of highly polymerized larch polymeric proanthocyanidins (LPPCs) and less highly polymerized larch oligomeric proanthocyanidins (LOPCs) were determined experimentally by inverse gas chromatography (IGC). These values were then compared with the solubility parameters obtained using molecular dynamics simulations. The experimentally measured solubility parameters of LPPCs and LOPCs (20.5 and 22.09 (J/m⁻³)^0.5, respectively) were in good agreement with the solubility parameters determined by molecular dynamics simulations (20.57 and 22.35 (J/m⁻³)^0.5, respectively. IGC was also used to experimentally determine the total surface energy, which includes the dispersive component of surface energy γsd  and the specific component of surface energy γssp, together with the surface acidity and basicity parameters of LPPCs and LOPCs at different temperatures. The surface properties of proanthocyanidins can be quickly and accurately evaluated by IGC, and both LPPCs and LOPCs were shown to be amphoteric materials. This study provides theoretical and technical support for the use of larch bark proanthocyanidins, which are non-toxic, renewable, and have good ultraviolet resistance, in the field of blending composites. The study also provides a reference for other studies on the interfacial interactions of wood fiber polymer composites.

Tannin-Based Hybrid Materials and Their Applications: A Review

Tannins are eco-friendly, bio-sourced, natural, and highly reactive polyphenols. In the past decades, the understanding of their versatile properties has grown substantially alongside a continuously broadening of the tannins' application scope. In particular, recently, tannins have been increasingly investigated for their interaction with other species in order to obtain tannin-based hybrid systems that feature advanced and/or novel properties. Furthermore, in virtue of the tannins' chemistry and their high reactivity, they either physicochemically or physically interact with a wide variety of different compounds, including metals and ceramics, as well as a number of organic species. Such hybrid or hybrid-like systems allow the preparation of various advanced nanomaterials, featuring improved performances compared to the current ones. Consequently, these diverse-shaped materials have potential use in wastewater treatment or catalysis, as well as in some novel fields such as UV-shielding, functional food packaging, and biomedicine. Since these kinds of tannin-based hybrids represent an emerging field, thus far no comprehensive overview concerning their potential as functional chemical building blocks is available. Hence, this review aims to provide a structured summary of the current state of research regarding tannin-based hybrids, detailed findings on the chemical mechanisms as well as their fields of application.

Very Strong, Super-Tough, Antibacterial, and Biodegradable Polymeric Materials with Excellent UV-Blocking Performance

In this work, inspired by the dynamic sacrificial hydrogen bonds in biological materials, a very strong, super-tough, antibacterial, and cost-effective biodegradable poly(vinyl alcohol) (PVA) nanocomposite material was developed by incorporating the nanoscale antibacterial agent TA@LS-Ag. TA@LS-Ag was prepared from the green biomass tannic acid (TA) and sodium lignosulfonate (LS), and was facilely incorporated into the PVA matrix with a homogeneously interspersed nanoparticle size of about 20 nm. The PVA nanocomposite film with 2 wt % addition of TA@LS-Ag achieved the highest specific toughness of 262 J g^-1 among the PVA-based films to date, which is far higher than that of natural spider silk (150-190 J g^-1 ), as well as a very high tensile strength of 131.6 MPa. The excellent tensile strength and superior toughness were attributed to synergy of the nanophase separation structure and the intense hydrogen-bonding interactions between the nanoparticles and PVA matrix. The PVA/TA@LS-Ag nanocomposite films exhibited good antibacterial properties, despite the extremely low silver content (0.032-0.32 wt ‰). TA@LS-Ag also endowed the PVA films with excellent antioxidant and UV-shielding performance. As the biomass-derived LS and TA and the PVA matrix are all biodegradable, this work offers a facile strategy for preparing high-performance antibacterial and biodegradable polymeric materials.

Effects of cellulose nanofibrils/graphene oxide hybrid nanofiller in PVA nanocomposites

NCF/GO hybrid nanofillers with excellent UV-shielding properties were prepared by using TEMPO-oxidized nanocellulose fibrils (NCF) and graphene oxide (GO) as raw materials; different mass ratios of NCF to GO (2: 1, 4: 1, 8: 1, and 16: 1) were used. The NCF and GO were then combined and used as a hybrid filler to study the synergistic effects on polyvinyl alcohol (PVA) nanocomposites. With 5% hybrid nanofiller, the UV-shielding performance of the PVA/NCF/GO composite film was higher than 90%. The tensile strength and Young's modulus of the PVA/CG-2 composite film increased by 74.5% and 278.0%, respectively, and the water absorption decreased by 59%. Moreover, the thermal stabilities of the nanocomposites also improved. This synergistic effect improved the performance of the hybrid nanofiller by avoiding the agglomeration of nanofillers in the polymer matrix and improving the homogeneity of the dispersion. The synergistic effect between the fillers provides a new idea for the preparation of novel multifunctional nanocomposites.

Antioxidant Properties of Agri-food Byproducts |and Specific Boosting Effects of Hydrolytic Treatments

Largely produced agri-food byproducts represent a sustainable and easily available source of phenolic compounds, such as lignins and tannins, endowed with potent antioxidant properties. We report herein the characterization of the antioxidant properties of nine plant-derived byproducts. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays indicated the superior activity of pomegranate peels and seeds, grape pomace and pecan nut shell. An increase in the antioxidant potency was observed for most of the waste materials following a hydrolytic treatment, with the exception of the condensed tannin-rich pecan nut shell and grape pomace. UV-Vis and HPLC investigation of the soluble fractions coupled with the results from IR analysis and chemical degradation approaches on the whole materials allowed to conclude that the improvement of the antioxidant properties was due not only to removal of non-active components (mainly carbohydrates), but also to structural modifications of the phenolic compounds. Parallel experiments run on natural and bioinspired model phenolic polymers suggested that these structural modifications positively impacted on the antioxidant properties of lignins and hydrolyzable tannins, whereas significant degradation of condensed tannin moieties occurred, likely responsible for the lowering of the reducing power observed for grape pomace and pecan nut shell. These results open new perspectives toward the exploitation and manipulation of agri-food byproducts for application as antioxidant additives in functional materials.

Natural Tannin Wood Extracts as a Potential Food Ingredient in the Food Industry

Wood extracts are one of the most important natural sources of industrially obtained tannins. Their use in the food industry could be one of the biggest (most important) recent innovations in food science as a result of their multiple (many) possible applications. The use of tannin wood extracts (TWEs) as additives directly added in foods or in their packaging meets an ever-increasing consumer demand for innovative approaches to sustainability. The latest research is focusing on new ways to include them directly in food, to take advantage of their specific actions to prevent individual pathological conditions. The present review begins with the biology of TWEs and then explores their chemistry, specific sensorial properties, and current application in food production. Moreover, this review is intended to cover recent studies dealing with the potential use of TWEs as a starting point for novel food ingredients.

Characterization of Ethyl Acetate and Trichloromethane Extracts from Phoebe zhennan Wood Residues and Application on the Preparation of UV Shielding Films

In this work, ethyl acetate (EA) and trichloromethane (TR) extracts were extracted from Phoebezhennan wood residues and the extracts were then applied to the preparation of UV shielding films (UV-SF). The results revealed that substances including olefins, phenols and alcohols were found in both EA and TR extracts, accounting for about 45% of all the detected substances. The two extracts had similar thermal stability and both had strong UV shielding ability. When the relative percentage of the extract is 1 wt% in solution, the extract solution almost blocked 100% of the UV-B (280–315 nm), and UV-A (315–400 nm). Two kinds of UV-SF were successfully prepared by adding the two extracts into polylactic acid (PLA) matrix. The UV-SF with the addition of 24 wt% of the extractive blocked 100% of the UV-B (280–315 nm) and more than 80% of the UV-A (315–400 nm). Moreover, the UV shielding performance of the UV-SF was still stable even after strong UV irradiation. Though the addition of extracts could somewhat decrease the thermal stability of the film, its effect on the end-use of the film was ignorable. EA extracts had less effect on the tensile properties of the films than TR extracts as the content of the extract reached 18%. The results of this study could provide fundamental information on the potential utilization of the extracts from Phoebe zhennan wood residues on the preparation of biobased UV shielding materials.

Low-Cost Ru/C-Catalyzed Depolymerization of the Polymeric Proanthocyanidin-Rich Fraction from Bark To Produce Oligomeric Proanthocyanidins with Antioxidant Activity

A new method has been developed for the high-value utilization of larch bark, which is regarded as a low-value byproduct of the logging industry. Polymeric proanthocyanidins (PPCs) were extracted from the Larix gmelinii bark and depolymerized by catalytic hydrogenolysis, using ruthenium/carbon (Ru/C) as the catalyst. The method has been found that although the molecular weight of the depolymerized product was significantly lower, the basic structural units were not destroyed, and the product retained a condensed flavanol polyphenol structure; the depolymerized product contains very little Ru metal and thus complies with food safety standards; the antioxidant properties of both the depolymerized products and PPCs were better than those of the commonly used antioxidant 2,6-di-tert-butyl-4-methylphenol. The relative molecular weight and steric hindrance of the depolymerized products were lower than those of the PPCs, leading to better antioxidant performance. A new technical route for the depolymerization of PPCs from the L. gmelinii bark is provided. The route offers practical and commercial advantages, and the product could have many applications as an antioxidant.

Recent Developments in the Reduction of Oxidative Stress through Antioxidant Polymeric Formulations

Reactive oxygen and nitrogen species (RONS) are produced endogenously in our body, or introduced through external factors, such as pollution, cigarette smoke, and excessive sunlight exposure. In normal conditions, there is a physiological balance between pro-oxidant species and antioxidant molecules that are able to counteract the detrimental effect of the former. Nevertheless, when this homeostasis is disrupted, the resulting oxidative stress can lead to several pathological conditions, from inflammation to cancer and neurodegenerative diseases. In this review, we report on the recent developments of different polymeric formulations that are able to reduce the oxidative stress, from natural extracts, to films and hydrogels, and finally to nanoparticles (NPs).

ANOVA Design for the Optimization of TiO2 Coating on Polyether Sulfone Membranes

There have been developments in the optimization of polyethersulfone (PES) membranes, to provide antifouling and mechanically stable surfaces which are vital to water purification applications. There is a variety of approaches to prepare nanocomposite PES membranes. However, an optimized condition for making such membranes is in high demand. Using experimental design and statistical analysis (one-half fractional factorial design), this study investigates the effect of different parameters featured in the fabrication of membranes, as well as on the performance of a nanocomposite PES/TiO₂ membrane. The optimized parameters obtained in this study are: exposure time of 60 s, immersion time above 10 h, glycerol time of 4 h, and a nonsolvent volumetric ratio (isopropanol/water) of 30/70 for PES and dimethylacetamide (PES-DMAc) membrane and 70/30 for PES and N-methyl-2-pyrrolidone (PES-NMP) membrane. A comparison of the contributory factors for different templating agents along with a nanocomposite membrane control revealed that F127 triblock copolymer resulted in an excellent antifouling membrane with a higher bovine serum albumin rejection and flux recovery of 83.33%.

Polypropylene Blend with Polyphenols through Dynamic Vulcanization: Mechanical, Rheological, Crystalline, Thermal, and UV Protective Property

Tannin and lignin were blended with polypropylene (PP) through dynamic vulcanization technique. Their influence of mechanical property, crystallinity, thermal stability, as well as ultraviolet (UV) protection property on the PP matrix was investigated and compared with native tannin and lignin. According to our experimental results, tannin and lignin undergo dynamic vulcanization and were more compatible with the PP matrix. Besides, tannin and vulcanized tannin can perform as nucleating agents of PP because of their relatively small particle size. Moreover, vulcanized tannin/lignin have a better performance on the thermal stability of PP compared with native tannin/lignin, especially PP/vulcanized lignin blend. Furthermore, vulcanized tannin/lignin present better UV protective performance, concluded from fewer changes on surface morphology, carbonyl index, crystallinity, viscosity, and tensile property.

Dynamically Cross-Linked Tannin as a Reinforcement of Polypropylene and UV Protection Properties

Tannins were used as reinforcing components for polypropylene with anti-UV properties via dynamic curing extrusion. The influence of cross-linked tannins in different weight fraction and their anti-UV capacity on morphological, mechanical, rheological, crystallize and thermal properties were studied. The experimental results indicated that the cross-linked tannins improve Young's modulus, crystallinity, and thermal stability and reinforce the internal network of polypropylene. After UV accelerated weathering, polypropylene had fewer surface cracks, lower carbonyl index, fewer crystallinity decreases and less mechanical properties loss with increasing tannin content.