Effect of fibrous TiO2 filler on the structural, mechanical, barrier and optical characteristics of biodegradable maize starch/PVA composite films

High-performance carboxymethyl starch/PVA based intelligent packaging films engineered with Cu-Trp nanocrystal as functional compatibilizer

A spindle-like Cu-based framework (Cu-Trp, Trp = L-Tryptophan) nanocrystal with ammonia-responsiveness was fabricated via simple aqueous solution approach, and it was subsequently explored as a functional compatibilizer of carboxymethyl starch/polyvinyl alcohol (CMS/PVA) blend toward constructing high-performance intelligent packaging films. The results showed that incorporation of Cu-Trp nanocrystal into CMS/PVA blend resulted in significant promotions regarding to the compatibility, mechanical strength (42.92 MPa), UV-blocking (with UV transmittance of only 2.4%), and water vapor barrier effectiveness of the blend film. Besides, the constructed CMS/PVA/Cu-Trp nanocomposite film exhibited superb long-term color stability, favorable antibacterial capacity (over 98.0%) toward both E. coli and S. aureus bacteria, as well as color change ability under ammonia environment. Importantly, the application trial confirmed that the CMS/PVA/Cu-Trp nanocomposite film is capable of visually monitoring shrimp spoilage during storage. These results implied that the CMS/PVA/Cu-Trp nanocomposite film holds tremendous potential as an intelligent active packaging material.

A review of starch/polyvinyl alcohol (PVA) blend film: A potential replacement for traditional plastic-based food packaging film

In recent years, the development of environmentally friendly packaging materials using biodegradable polymers has emerged as a key challenge for scientists and consumers in response to resource depletion and environmental issues caused by plastic packaging materials. Starch and polyvinyl alcohol (PVA) are being recognized as excellent candidates for producing biodegradable food packaging films. Polymer blending has emerged as a practical approach to overcome the limitations of biopolymer films by developing films with unique properties and enhancing overall performance. This review briefly introduces the molecular structure and properties of starch and PVA, summarizes the common preparation methods and properties of starch/PVA blend films, and focuses on different strategies used to enhance starch/PVA blend films, including nanoparticles, plant extracts, and cross-linking agents. Additionally, this study summarizes the application of starch/PVA blend films as active and smart packaging in food preservation systems. This study demonstrates that starch and PVA blends have potential in manufacturing biodegradable food films with excellent properties due to their excellent compatibility and intermolecular interactions, and can be used as packaging films for a variety of foods to extend their shelf life.

Tapioca-starch-based bionanocomposites with fructose and titanium dioxide for food packaging and fertilization applications

Bionanocomposites offer a promising solution to the plastic waste crisis. Although tapioca starch shows potential as a bioplastic material, it is characterized by low mechanical properties, poor thermal stability, and high water absorption owing to its hydrophilic nature. To increase the flexibility of the material and reduce the transmission rate of oxygen and water vapor, additives such as fructose and titanium dioxide (TiO2) can be incorporated into the material. TiO2 nanoparticles are commonly utilized in agriculture to enhance nutrient release and promote plant growth. In this study, X-ray diffraction analysis revealed that TiO2 reduced crystal size while increasing the crystallinity of bionanocomposites. Fourier-transform infrared spectroscopy analysis revealed an absorption peak at 3397 cm-1, indicating hydrogen bonding between TiO2 and starch-OH groups, and a peak at 773 cm-1, indicating an increase in the intensity of Ti-O-Ti stretching vibrations with the incorporation of TiO2. Water absorption rate results confirmed that TiO2 addition enhanced bionanocomposite resistance to water vapor and moisture, evidenced by increased tensile strength from 0.11 to 0.49 MPa and Young's modulus from 2.48 to 5.26 MPa, as well as decreased elongation at break from 21.46 % to 2.36 % in bionanocomposites with TiO2. Furthermore, with TiO2 addition, the biodegradation rate of the bionanocomposites decreased, which is beneficial for enhancing plant nutrient content.

Novel intelligent packaging films based on starch/PVA with Cu-ICA nanocrystal as functional compatibilizer for monitoring food freshness

Considering public health and environmental safety, the development of reliable and efficient monitoring methods is essential to ensure food quality and safety. Herein, a new Cu-based metal organic framework (Cu-ICA) nanocrystal with ammonia-sensitive performance was built up and then introduced as a functional compatibilizer of starch/polyvinyl alcohol (STA/PVA) blend to develop high-performance intelligent packaging films for food freshness monitoring. The introduction of Cu-ICA upgraded the compatibility, mechanical strength (42.9 MPa), UV-protection (with UV transmittance of only 2.8 %), and moisture/oxygen barrier performances of STA/PVA film. Furthermore, the developed STA/PVA/Cu-ICA films presented long-term colour stability, outstanding antibacterial efficacy (over 99.5 %) toward both Escherichia coli and Staphylococcus aureus bacteria, as well as remarkable ammonia-sensitive discoloration capability. The STA/PVA/Cu-ICA films possessed visually identifiable colour change during the monitoring of shrimp spoilage. These findings indicate that the developed STA/PVA/Cu-ICA film possesses tremendous potential as an intelligent active packaging material.

Nacre-inspired starch-based bioplastic with excellent mechanical strength and electromagnetic interference shielding

Bioplastics have aroused significant interest in researchers to relieve the serious environmental pollution caused by the ubiquity of petroleum-based plastics. However, it remains a great challenge to construct functional bioplastics with excellent mechanical strength, water resistance, and heat resistance. Inspired by the interesting structure of nacre, a novel starch-based bioplastic was prepared via a self-assembly technique, using 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers modified starch, nano-montmorillonite, and reduced graphene oxide as raw materials. Due to the unique layered structure and rich interfacial interaction, the starch-based bioplastic exhibited excellent mechanical properties, while the tensile strength was up to 37.39 MPa. Furthermore, it represented outstanding water resistance, heat resistance, repairability, renewability and biodegradability. Especially, the starch-based bioplastic demonstrated a strong electromagnetic interference shielding effectiveness (EMI SE), which was higher than 35 dB with a thickness of 0.5 mm. These powerful properties provided the possibility for functional applications of starch-based bioplastics.

Smart packaging films based on corn starch/polyvinyl alcohol containing nano SIM-1 for monitoring food freshness

There is at present an acute need for the construction of biopolymer-based smart packaging material that can be applied for the real-time visual monitoring of food freshness. Herein, a nano-sized substituted imidazolate material (SIM-1) with ammonia-sensitive and antibacterial ability was effectively manufactured and then anchored within corn starch/polyvinyl alcohol (CS/PVA) blend to construct biopolymeric smart active packaging material. The structure, physical and functional performances of CS/PVA-based films with different content of SIM-1 (0.5, 1.0 and 2.0 wt% on CS/PVA basis) were then explored in detail. Results revealed that the incorporated SIM-1 nanocrystals were equally anchored within the CS/PVA matrix owing to the establishment of potent hydrogen-bonding interactions, which produced an obvious improvement in the compatibility of CS/PVA blend film, as well as its mechanical strength, water/oxygen barrier and UV-screening performances. The constructed CS/PVA/SIM-1 blend films further demonstrated superior long-term color stability property, ammonia-sensitive and antibacterial functions. Furthermore, the CS/PVA/SIM-1 blend films were utilized for effectively monitoring the deterioration of shrimp via observable color alteration. The above findings suggested the potential applications of CS/PVA/SIM-1 blend films in smart active packaging.

A novel, robust mechanical strength, and naturally degradable double crosslinking starch-based bioplastics for practical applications

The increasing number of petroleum-based plastics has caused severe environmental pollution, which has attracted great research interest in the development of low-cost, renewable, and degradable starch-based bioplastics. However, developing starch-based bioplastics with robust mechanical strength, excellent water resistance, and thermal resistance remains a great challenge. In this study, we presented a simple and efficient method for preparing high-performance novel starch-based bioplastics with chemical and physical double crosslinking network structures filled with 2,2,6,6-tetramethylpiperidine 1-oxy-oxidized cellulose nanofibers and zinc oxide nanoparticles. Compared with pure starch-based bioplastics, the tensile strength of the novel robust strength starch-based bioplastics increased by 431.2 %. The novel starch-based bioplastics exhibited excellent mechanical properties (tensile strength up to 24.54 MPa), water resistance, thermal resistance, and biodegradability. In addition, the novel starch-based bioplastics could be reused, crushed, dissolved, and re-poured after use. After recycling, the novel starch-based bioplastics could be discarded in the soil to achieve complete degradation within six weeks. Owing to these characteristics, the novel starch-based bioplastics are good alternatives used to replace traditional petroleum-based plastics and have great development prospects.

Reuse of used paper egg carton boxes as a source to produce hybrid AgNPs- carboxyl nanocellulose through bio-synthesis and its application in active food packaging

The proper disposal of disposable synthetic plastic food packaging materials presents a significant challenge for both the environment and the solid waste management community. To address this issue, an antibacterial-based high-strength bio-composite serves as the optimal alternative to conventional packaging materials. This study aims to produce a hybrid material of AgNPs-carboxyl cellulose nanocrystals (AgNPs-CCNCs), obtained from used egg carton boxes (UECBs), through bio acid hydrolysis and an in-situ generation process. Furthermore, AgNPs- carboxyl cellulose nanofibers (AgNPs-CCNFs) will be synthesized through a combination of bio acid hydrolysis and ball milling, followed by an additional in-situ generation step. The AgNPs-carboxyl nanocellulose (AgNPs-CCNCs, and AgNPs-CCNFs) exhibited excellent crystallinity index, morphology, thermal, and antibacterial properties. The morphological analysis was performed by electron microscopy, and the results showed the uniform distribution and spherical form of AgNPs appearing over the carboxyl nanocellulose through the in-situ generation process, which was confirmed through XRD analysis. The study further explores the impact of AgNPs-carboxyl nanocellulose on the mechanical, chemical, antibacterial, and thermal properties of the PVA matrix. The results demonstrate that the bio-nanocomposite film offers opportunities for utilization in active packaging applications.

Characterization of Nano-SiO2/Zein Film Prepared Using Ultrasonic Treatment and the Ability of the Prepared Film to Resist Different Storage Environments

This study has developed, ultrasound-assisted, a novel food packaging film (U-zein/SiO2) for food packaging applications. Incorporating an optimal concentration of 18 mg/mL of nano-SiO2 and subjecting the film to 10 min of ultrasonic treatment resulted in a remarkable increase of 32.89% in elongation at break and 55.86% in tensile strength. In addition, the incorporation of nano-SiO2 effectively reduces the water content and solubility of the composite film, resulting in improved water/oxygen barrier properties. These physiochemical properties were further improved with the application of ultrasound. The analysis of attenuated total reflectance-Fourier transform infrared, X-ray diffraction, differential scanning calorimetry, and scanning electronic microscope demonstrated that the ultrasound treatment improved the hydrogen bonds, improved thermal stability, molecular arrangement, structure stability, and intermolecular compatibility of the composite film, resulting in enhanced physio-mechanical properties of the film. In addition, the ultrasound treatment led to a smoother film surface and reduced the pores on the film's cross-section. Moreover, the U-zein/SiO2 film exhibited excellent mechanical and water/oxygen barrier properties in different storage environments over a period of 30 days. These results offer sound theoretical support for the practical application of the prepared preservative film.

Metal-Based Nanoparticles in Food Packaging and Coating Technologies: A Review

Food security has continued to be a topic of interest in our world due to the increasing demand for food. Many technologies have been adopted to enhance food supply and narrow the demand gap. Thus, the attempt to use nanotechnology to improve food security and increase supply has emerged due to the severe shortcomings of conventional technologies, which have made them insufficient to cater to the continuous demand for food products. Hence, nanoparticles have been identified to play a major role in areas involving food production, protection, and shelf-life extensions. Specifically, metal-based nanoparticles have been singled out to play an important role in manufacturing materials with outstanding properties, which can help increase the shelf-life of different food materials. The physicochemical and biological properties of metal-based nanoparticles, such as the large surface area and antimicrobial properties, have made them suitable and adequately useful, not just as a regular packaging material but as a functional material upon incorporation into biopolymer matrices. These, amongst many other reasons, have led to their wide synthesis and applications, even though their methods of preparation and risk evaluation remain a topic of concern. This review, therefore, briefly explores the available synthetic methods, physicochemical properties, roles, and biological properties of metal-based nanoparticles for food packaging. Furthermore, the associated limitations, alongside quality and safety considerations, of these materials were summarily explored. Although this area of research continues to garner attention, this review showed that metal-based nanoparticles possess great potential to be a leading material for food packaging if the problem of migration and toxicity can be effectively modulated.

Preparation technology and preservation mechanism of γ-CD-MOFs biaological packaging film loaded with curcumin

To prevent food spoilage caused by microbial infection, the development of an environmentally friendly antimicrobial preservation material is crucial. Here, the microporous γ-CD-MOFs was utilized to encapsulate the hydrophobic active substance curcumin, resulting in the preparation of a non-toxic antimicrobial material (Cur-CD-MOFs). The results revealed that curcumin encapsulation in Cur-CD-MOFs occurred primarily in the carbonyl group, benzene ring, and enolic side ring of curcumin. The Cur-CD-MOFs had a 100% bactericidal effect on Escherichia coli and Staphylococcus aureus at 4 h and 8 h, and a strong inhibitory effect on aerial mycelium of Penicillium expansum and Botrytis cinerea. Furthermore, the incorporation of Cur-CD-MOFs improved the Pul/Tre film barrier and mechanical properties. The effectiveness of Cur-CD-MOFs-Pul/Tre in retaining fruit freshness was validated using Centennial Seedless grapes. This study confirmed that Cur-CD-MOFs is a promising antibacterial material, and Cur-CD-MOFs-Pul/Tre will be a potent candidate for food preservation.

Copper-based nanoparticles for biopolymer-based functional films in food packaging applications

This review summarizes the latest developments in the design, fabrication, and application of various Cu-based nanofillers to prepare biopolymer-based functional packaging films, focusing on the effects of inorganic nanoparticles on the optical, mechanical, gas barrier properties, moisture sensitivity, and functional properties of the films. In addition, the potential application of Cu-based nanoparticle-added biopolymer films for fresh food preservation and the effect of nanoparticle migration on food safety were discussed. The incorporation of Cu-based nanoparticles improved the film properties with enhanced functional performance. Cu-based nanoparticles such as copper oxide, copper sulfide, copper ions, and copper alloys affect biopolymer-based films differently. The properties of composite films containing Cu-based nanoparticles depend on the concentration of the filler, the state of dispersion, and the interaction of the nanoparticles with the biopolymer matrix in the film. The composite film filled with Cu-based nanoparticles effectively extended the shelf life by maintaining the quality of various fresh foods and securing safety. However, studies on the migration characteristics and safety of copper-based nanoparticle food packaging films are currently being conducted on plastic-based films such as polyethylene, and research on bio-based films is limited.

High performance biopolymeric packaging films containing zinc oxide nanoparticles for fresh food preservation: A review

Biodegradable food packaging films (FPFs) assembled from sustainable biopolymeric materials are of increasing interest to the food industry due to pollution and health risks resulting from the use of conventional plastic packaging. However, the functional performance of these FPFs is often poorer than that of plastic films, which limits their commercial application. This problem may be partly overcome by incorporating nano-additives like zinc oxide nanoparticles (ZNPs) into the films. The incorporation of ZNPs into FPFs can improve their functional performance. The properties of these films depends on the concentration, dispersion state, and interactions of ZNPs with the biopolymeric matrix in the films. ZNPs-loaded films and coatings are highly effective at preserving a variety of fresh foods. Studies of ZNPs migration through FPFs have shown that the zinc is mainly transported in an ionic form and the amount entering foods is below safety standards. This article reviews recent developments in the design, fabrication, and application of ZNPs-loaded FPFs based on biopolymers, focusing on the impacts of ZNPs on the optical, barrier, mechanical, water sensitivity, and antimicrobial properties of the films. The potential applications of ZNPs-loaded FPFs for fresh food preservation is also discussed.

Environmental Properties and Applications of Biodegradable Starch-Based Nanocomposites

In recent years, the demand for environmental sustainability has caused a great interest in finding novel polymer materials from natural resources that are both biodegradable and eco-friendly. Natural biodegradable polymers can displace the usage of petroleum-based synthetic polymers due to their renewability, low toxicity, low costs, biocompatibility, and biodegradability. The development of novel starch-based bionanocomposites with improved properties has drawn specific attention recently in many applications, including food, agriculture, packaging, environmental remediation, textile, cosmetic, pharmaceutical, and biomedical fields. This paper discusses starch-based nanocomposites, mainly with nanocellulose, chitin nanoparticles, nanoclay, and carbon-based materials, and their applications in the agriculture, packaging, biomedical, and environment fields. This paper also focused on the lifecycle analysis and degradation of various starch-based nanocomposites.

Enhanced Antibacterial Performance of Chitosan/Corn Starch Films Containing TiO2/Graphene for Food Packaging

Chitosan (CTS)/corn starch (CSH)/nano-TiO₂/graphene (Gr) antibacterial active packaging films were prepared by ultrasonic-assisted electrospray deposition and solution-casting methods, and the effects of the TiO₂:Gr mass ratio and ultrasonication power on their morphology and mechanical, optical, thermal, barrier, and antibacterial properties were investigated. The film fabricated at a TiO₂:Gr ratio of 6:4 and an ultrasonication power of 160 W exhibited a uniform distribution of the nanofillers in the CTS/CSH matrix and significantly enhanced the mechanical, barrier, and water-resistance properties. Furthermore, this film demonstrated superior ultraviolet and visible light-shielding characteristics as compared with those of the non-filled CTS/CSH film, while its Escherichia coli and Staphylococcus aureus inhibition efficiencies were equal to 96.67 ± 0.09% and 99.85 ± 0.13%, respectively. Therefore, the film can effectively prevent food spoilage, indicating its potential for food-packaging applications.

High-performance multifunctional polyvinyl alcohol/starch based active packaging films compatibilized with bioinspired polydopamine nanoparticles

Bioinspired polydopamine (PDA) nanoparticles were synthesized and explored as functional compatibilizers in polyvinyl alcohol/starch (PVA/ST) matrix to develop high-performance multifunctional packaging film. The effect of the addition of PDA on the microstructural, mechanical, thermal, water vapor barrier, ultraviolet (UV)/high-energy blue light (HEBL) blocking, thermal insulating and antioxidant properties of PVA/ST composite films was fully investigated. Results demonstrated that the added PDA nanoparticles were evenly dispersed in the PVA/ST matrix, providing compact and dense nanocomposite films due to their compatibilization effect. Compared with virgin PVA/ST film, the resulting PVA/ST/PDA nanocomposite films exhibited greatly improved tensile strength, toughness, thermal stability, and water vapor barrier ability. Furthermore, the presence of PDA endowed PVA/ST composite film with excellent UV/HEBL blocking, thermal insulating as well as antioxidant functions. Thus, such high-performance multifunctional nanocomposite films hold the potential of protecting food quality against photothermal oxidative deterioration and extend food shelf life.

Structural and Physicomechanical Properties of an Active Film Based on Potato Starch, Silver Nanoparticles, and Rose Apple (Syzygium samarangense) Extract

In the current research work, active films were made from potato starch (PS) and AgNP solution comprising of silver nanoparticles (AgNPs) and rose apple extract (RE) via the casting method at various concentrations. AgNP solution in the PS matrix significantly altered the physical properties such as opacity, water vapor permeability mechanical property, solubility, and swelling index of the films. The influence of AgNP solution on the properties of the films was deeply examined. The results found that the 15% AgNP solution films exhibited better physicochemical properties. The presence of AgNP solution in the PS matrix significantly improved the properties of active films which is evident from the results of FTIR and SEM. Results show that AgNPs and PS were uniformly mixed and formed continuous and homogenous films without bubbles and cracks. In addition, the AgNP solution in the films significantly improved the antibacterial activity against S. aureus than P. aeruginosa in the films.

Fabrication of highly transparent and multifunctional polyvinyl alcohol/starch based nanocomposite films using zinc oxide nanoparticles as compatibilizers

This work explored biodegradable polyvinyl alcohol/starch (PVA/ST) film compatibilized by rod-like ZnO nanofillers as multifunctional food packaging materials. The influence of rod-like ZnO nanofillers on the microstructural, UV-shielding, antibacterial, mechanical, thermal, together with water barrier performances of PVA/ST composite films was fully studied. Results revealed that rod-like ZnO nanofillers could be uniformly distributed into the PVA/ST matrix, playing the role of compatibilizers to provide compact and dense nanocomposite films. The resulting nanocomposite films presented greatly improved mechanical and water vapor barrier properties as compared to virgin PVA/ST film. Moreover, the well distributed ZnO endowed PVA/ST film with excellent antimicrobial activity against both E. coli and S. aureus, together with outstanding UV-shielding capability meanwhile retaining highly optical transparency (approximately 90%). The developed PVA/ST/ZnO films were tested for packaging fresh-cut carrot slices to prevent microbial infection and prolong their shelf life. These results indicated that the developed highly transparent and multifunctional PVA/ST/ZnO nanocomposite films possess broad application prospects in active food packaging field.

Biocompatible and Antimicrobial Cellulose Acetate-Collagen Films Containing MWCNTs Decorated with TiO2 Nanoparticles for Potential Biomedical Applications

This research focuses on the synthesis of multi-walled carbon nanotubes (MWCNTs) decorated with TiO₂ nanoparticles (NPs) and incorporated in cellulose acetate-collagen film in order to obtain a new biomaterial with potential biomedical applications and improved antimicrobial activity. The successful decoration of the MWCNTs with TiO₂ NPs was confirmed by several structural and morphological analysis, such as Fourier transformed infrared spectroscopy, Raman spectroscopy, X-ray diffraction and transmission electron microscopy. The obtained nanocomposites were further incorporated into cellulose acetate-collagen films, at different concentrations and absorption kinetics, antimicrobial activity and in vitro biocompatibility of the obtained films was investigated. The antimicrobial tests sustained that the presence of the nanocomposites into the polymeric matrix is an important aspect in increasing and maintaining the antimicrobial activity of the polymeric wound dressings over time. The biocompatibility and cytotoxicity of the obtained films was evaluated using cellular viability/proliferation assay and fluorescent microscopy which revealed the ability of the obtained materials as potential wound dressing biomaterial.

Ultrasonication effects on physicochemical properties of biopolymer-based films: A comprehensive review

Biopolymeric films manufactured from materials such as starch, cellulose, protein, chitosan, gelatin, and polyvinyl alcohol are widely applied due to their complete biodegradability. While biopolymer-based films exhibit good gas barriers and optical properties when used in packaging, poor moisture resistance and mechanical properties limit their further application. Ultrasonication is a promising, effective technology for resolving these shortcomings, with its high efficiency, environmentally friendly nature, and safety. This review briefly introduces basic ultrasonication principles and their main effects on mechanical properties, transparency, color, microstructure, water vapor permeability, and oxygen resistance. We also describe the thermal performance of biopolymeric films. While ultrasonication has many positive effects on the physicochemical properties of biopolymeric films, many factors influence their behavior during film preparation, including power density, amplitude, treatment time, frequency, and the inherent properties of the source materials. This review focuses on biopolymers as film-forming materials and comprehensively discusses the promotional effects of ultrasonication on their physicochemical properties.

A novel Ag2O-TiO2-Bi2WO6/polyvinyl alcohol composite film with ethylene photocatalytic degradation performance towards banana preservation

In this research, the Ag₂O-TiO₂-Bi₂WO₆(ATB) ternary heterojunction photocatalyst was synthesized by hydrothermal and surface deposition method, and the ATB/PVA composite film with ethylene photocatalytic degradation performance was constructed by the casting method. The structure and properties of ATB and ATB/PVA films were characterized and applied to banana preservation. The results showed that the addition of ATB could improve the mechanical properties, thermal stability, oxygen and moisture resistance, and reduce the crystallinity and light transmittance of PVA films. Compared with TiO₂, Bi₂WO₆ and TB photocatalysts, ATB had the best photocatalytic degradation effect of ethylene under LED light. Compared with blank group, the ethylene concentration decreased by 17.17%. This was mainly attributed to the formation of heterostructure among Ag₂O, TiO₂ and Bi₂WO₆, which promoted the separation and transfer of photogenerated carriers. The ATB/PVA composite coating could effectively prevent the respiration of the bananas by inhibiting gas exchange and degrading ethylene, which reduced the weight loss, inhibited glycogen decomposition, improved the pulp hardness, increased titratable acid content, reduced the PPO activity, hindered the phenol oxidation and keep better apparent color of bananas. The safety study suggested that the ATB/PVA film is safe for bananas packaging application.

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.

Titanium content influence on the optical response characteristics of TiO2/ormosils composite films doped with azobenzene

TiO₂-based organic-inorganic composite films doped with azobenzene and photosensitive groups were prepared by combining a low-temperature solgel technique and a spin-coating method. The influence of TiO₂ content on the optical and structural properties of the composite films including the film thickness, the refractive index, the transmission loss, the thermal gravity analysis, and Fourier transform infrared spectroscopy spectra was studied. Photoisomerization and optical switching characteristics of the composite film were investigated under the irradiation of 365 nm ultraviolet light and 450 nm visible light. Results indicate that several micrometer thick films can be easily obtained at room temperature and there is a proportional relationship between the refractive index value and the TiO₂ content. In addition, the composite films have a low optical propagation loss of about 0.1 dB/cm. The composite films with 0.2 M TiO₂ content have an obvious photoisomerization and good optical switching properties. Finally, the hexagonal microlens array was fabricated in the composite films by using an ultraviolet nanoimprint technology. All these results above indicate that the as-prepared TiO₂-based organic-inorganic composite film has potential applications in optical switching devices and photonic elements.

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

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

Plasticized Starch/Agar Composite Films: Processing, Morphology, Structure, Mechanical Properties and Surface Hydrophilicity

Natural biopolymers, which are renewable, widely available, biodegradable, and biocompatible, have attracted huge interest in the development of biocomposite materials. Herein, formulation–property relationships for starch/agar composite films were investigated. First, rapid visco analysis was used to confirm the conditions needed for their gelation and to prepare filmogenic solutions. All the original crystalline and/or lamellar structures of starch and agar were destroyed, and films with cohesive and compact structures were formed, as shown by SEM, XRD, and SAXS. All the plasticized films were predominantly amorphous, and the polymorphs of the composite films were closer to that of the agar-only film. FTIR results suggest that the incorporation of agar restricted starch chain interaction and rearrangement. The addition of agar to starch increased both tensile strength and elongation at break, but the improvements were insignificant after the agar content was over 50 wt.%. Contact angle results indicate that compared with the other samples, the 4:6 (wt./wt.) starch/agar film was less hydrophilic. Thus, this work shows that agar dominates the structure and properties of starch/agar composites, and the best properties can be obtained with a certain starch/agar ratio. Such composite polysaccharide films with tailored mechanical properties and surface hydrophilicity could be useful in biodegradable packaging and biomedical applications (wound dressing and tissue scaffolding).

A thermoreversible crosslinking hot-melt adhesive: reversibility and performance

The need to improve the environmental friendliness and achieve the recycling of resins is an ongoing process for hot-melt adhesive technology. In this work, a new type of thermoreversible crosslinking hot-melt adhesive-based Diels Alder (DA) reaction was prepared. The critical idea was to efficiently initiate the esterification to yield furoic acid (FA)-grafted poly(vinyl alcohol) (PVA-g-FA), and then PVA-g-FA was mixed with N,N′-(4,4′-methylenediphenyl)dimaleimide (MDI) to finally obtain the thermoreversible crosslinking adhesive (PVA-g-FA/MDI). The experimental results indicated that the reversibility of the DA reaction between the furan rings and the maleimide groups allowed PVA-g-FA/MDI to be dynamically crosslinked. It was able to crosslink at a temperature of 80 °C and decrosslink at 120 °C. Moreover, the performances of hot-melt adhesive were investigated. The PVA-g-FA/MDI had a better peeling strength (43.33 N mm⁻¹), bond strength (11.84 MPa), and thermal conductivity (0.263 W m⁻¹ K⁻¹) than PVA resins. The light-transmittance and haze value were 52.8% and 12.24‰, respectively. The PVA-g-FA/MDI resin could be reused more than two times.

The need to improve the environmental friendliness and achieve the recycling of resins is an ongoing process for hot-melt adhesive technology.

A photo-reversible crosslinking resin for additive manufacturing: reversibility and performance

Improving the adhesion between layers and achieving the recycling of resins are challenges in additive manufacturing (AM) technology. In this work, a new type of photo-reversible crosslinking resin based on polyvinyl alcohol (PVA) and coumarin (HMC) was prepared via grafting reaction. The critical idea was to create a coumarin based photo-reversible crosslinking resin by carefully tailoring the photo-crosslinking time and temperature, so that the resin could be extruded through the nozzle and then maintain the proper shape during UV-curing. Photo-reversible crosslinking of AM resin was realized without the use of monomers, photo-initiators or propagating. A reasonable irradiation time with 354 nm (crosslink) or 254 nm UV light (cleavage) of 10 min was critical for photo-reversible crosslinking of PVA-g-HMC at 120 °C. An important result of this work was that the developed photo-reversible crosslinked resin could be reused and the printed resin exhibits excellent adhesion properties, thermal conductivity and oxygen barrier performance.

Use of Titanium Dioxide (TiO2) Nanoparticles as Reinforcement Agent of Polysaccharide-Based Materials

In recent years, a strong interest has emerged in polysaccharide-hybrid composites and their potential applications, which have interesting functional and technological properties. This review summarizes and discusses the reported advantages and limitations of the functionalization of conventional and nonconventional polysaccharides by adding TiO2 nanoparticles as a reinforcement agent. Their effects on the mechanical, thermal, and UV-barrier properties as well as their water-resistance are discussed. In general, the polysaccharide–TiO2 hybrid materials showed improved physicochemical properties in a TiO2 content-dependent response. It showed antimicrobial activity against bacteria (gram-negative and gram-positive), yeasts, and molds with enhanced UV-protective effects for food and non-food packaging purposes. The reported applications of functionalized polysaccharide–TiO2 composites include photocatalysts (dye removal from aqueous media and water purification), biomedical (wound-healing material, drug delivery systems, biosensor, and tissue engineering), food preservation (fruits and meat), cosmetics (sunscreen and bleaching tooth treatment), textile (cotton fabric self-cleaning), and dye-sensitized solar cells. Furthermore, the polysaccharide–TiO2 showed high biocompatibility without adverse effects on different cell lines, indicating that their use in food, pharmaceutical, and biomedical applications is safe. However, it is necessary to evaluate the structural changes promoted by the storage conditions (time and temperature) on the physicochemical properties of polysaccharide–TiO2 hybrid composites to guarantee their stability during a determined time.

Effects of Ultrasonication Time on the Properties of Polyvinyl Alcohol/Sodium Carboxymethyl Cellulose/Nano-ZnO/Multilayer Graphene Nanoplatelet Composite Films

Ultrasonication-assisted solution casting was used to prepare polyvinyl alcohol (PVA)/sodium carboxymethyl cellulose (CMC)/nano-ZnO/multilayer graphene nanoplatelet (xGnP) composite films; the performances (mechanical properties, water vapor permeability (WVP), biodegradability and antibacterial activity) of these films were investigated as a function of the ZnO NPs:xGnP mass ratio and ultrasonication time. Intermolecular interactions among ZnO NPs, xGnP and the PVA/CMC matrix were shown to improve WVP, while X-ray diffraction and scanning electron microscopy analyses revealed that the internal reticular structure of ultrasound-treated PVA/CMC/ZnO NPs/xGnP composite films was in a fluffier state than that of the untreated composite films and the PVA/CMC film. The incorporation of ZnO NPs and xGnP into the composite film reduced its tensile strength and elongation at break, and increased antibacterial activity and biodegradability. In addition, we carried out the experiment of strawberry preservation and measured weight loss ratio, firmness, content of total soluble solids and titration acid. Finally, the composite film of 7:3 had the best preservation effect on strawberries. Thus, the obtained results paved the way to develop novel biodegradable composite films with antimicrobial activity for a wide range of applications.

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.

Chitosan-TiO2: A Versatile Hybrid Composite

In recent years, a strong interest has emerged in hybrid composites and their potential uses, especially in chitosan–titanium dioxide (CS–TiO₂) composites, which have interesting technological properties and applications. This review describes the reported advantages and limitations of the functionalization of chitosan by adding TiO₂ nanoparticles. Their effects on structural, textural, thermal, optical, mechanical, and vapor barrier properties and their biodegradability are also discussed. Evidence shows that the incorporation of TiO₂ onto the CS matrix improves all the above properties in a dose-dependent manner. Nonetheless, the CS–TiO₂ composite exhibits great potential applications including antimicrobial activity against bacteria and fungi; UV-barrier properties when it is used for packaging and textile purposes; environmental applications for removal of heavy metal ions and degradation of diverse water pollutants; biomedical applications as a wound-healing material, drug delivery system, or by the development of biosensors. Furthermore, no cytotoxic effects of CS–TiO₂ have been reported on different cell lines, which supports their use for food and biomedical applications. Moreover, CS–TiO₂ has also been used as an anti-corrosive material. However, the development of suitable protocols for CS–TiO₂ composite preparation is mandatory for industrial-scale implementation.