Thermal, mechanical and viscoelastic properties of citric acid-crosslinked starch/cellulose composite foams

Impact of citrus pectin on the foaming behavior, structures, and barrier properties of the starch foam blocks

The starch foam displays weak barrier properties under humid storage, which limits its applications in the food industry. In this study, citrus pectin was loaded to strengthen the starch foam. Results showed that the pectin (4 wt% ∼ 8 wt%) effectively modified the cell structures of the starch foam block. This was attributed to the increased viscosity of the starch melt during foaming and the enhanced cell stability during cooling, which was promoted by the formation of entanglements, hydrogen bonds, and ester bonds between pectin and starch, as confirmed by FTIR and DSC. Moreover, the pectin-starch foam displayed improved mechanical properties under wet storage conditions, mainly due to the limited moisture adsorption and water migration. The foam containing 4 wt% of pectin exhibited the highest compression-recovery ratio (76.7 %) and a reduced adsorbed moisture content (19.22 %) under 95 % RH. Overall, citrus pectin could improve the starch foaming process and the foam blocks barrier properties.

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

Development of High-Efficiency Fertilizer by Hydrogels Obtained from Cassava Starch and Citric Acid for Slow Release of Ammonium and Potassium

Fertilizers with enhanced efficiency or high-efficiency fertilizers increase the nutrient availability, minimize losses, and reduce costs, thereby increasing crop yields and food production while mitigating environmental impacts. This research evaluates the synthesis of biodegradable hydrogels from cassava starch and citric acid for agrochemical applications. Hydrogels were synthesized using water as the solvent and applied for the controlled release of macronutrients (N and K). Four concentrations of nutrient-containing salts were tested (0.5 to 10.0% w/w). Materials were analyzed using ATR-FTIR spectroscopy and swelling studies. The presence of nutrients reduced both the crosslinking efficacy and the water absorption capacity, with the latter dropping from 183.4 ± 0.6% to 117.9 ± 3.7% and 157.4 ± 25.0% for hydrogels loaded with NH4Cl and KCl, respectively. The cumulative release of K and N from the hydrogel was monitored for 144 h and examined using kinetics models, revealing that the releases follow Fickian's diffusion and anomalous diffusion, respectively. Additionally, the material was formed using cassava with peel previously milled to reduce the production costs, and its potential for nutrient-controlled delivery was evaluated, with the finding that this hydrogel decreases the release rate of nitrogen. The results suggest that these biomaterials may have promising applications in the agrochemical industry in the making of high-efficiency fertilizers.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives

The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials.

Comprehensive enhancement of flame retardant starch/cellulose/diatomite composite foams via metal-organic coordination

In recent years, considerable attention has been given to the utilization of biomass for producing bio-based foams, such as starch-based foams. Despite their renewability and widespread availability, these foams still present certain drawbacks regarding their poor mechanical properties and flammability. To tackle these concerns, a metal ion cross-linking strategy was employed by incorporating calcium ions (Ca2+) solution into foamed starch/cellulose slurry. Followed by ambient drying, starch/cellulose composite foam was successfully fabricated with a remarkable enhancement in various properties. Specifically, compared to the control sample, the compressive strength and modulus increased by 26.2 % and 123.0 %, respectively. Additionally, the Ca2+ cross-linked starch/cellulose composite foam exhibited excellent heat resistance, water stability, and flame retardancy. The limiting oxygen index (LOI) reached 52 %, with a vertical combustion rating of V-0. Along with the addition of 2 phr diatomite, it demonstrated a significant enhancement on flame retardancy with a LOI of 65 %, although the apparent density of the composite foam was not low enough. This study indicated a green and simple method to obtain starch-based composite foams with enhanced comprehensive properties including thermal, water stability, mechanical, and flame retardancy, expanding their potential applications in areas such as building materials and rigid packaging.

Effects of crosslinking agents on properties of starch-based intelligent labels for food freshness detection

The impact of citric acid, carboxymethyl cellulose, carboxymethyl starch, sodium trimetaphosphate, or soybean protein on the crosslinking of starch-based films was examined. These crosslinking starch films were then used to create pH-sensitive food labels using a casting method. Blueberry anthocyanins were incorporated into these smart labels as a pH-sensitive colorimetric sensor. The mechanical properties, moisture resistance, and pH responsiveness of these smart labels were then examined. Crosslinking improved the mechanical properties and pH sensitivity of the labels. These different crosslinking agents also affected the hydrophobicity of the labels to varying degrees. Soybean protein was the only additive that led to labels that could sustain their structural integrity after immersion in water for 12 h. Because it increased the hydrophobicity of the labels, which decreased their water vapor permeability, moisture content, swelling index, and water solubility by 47 %, 29 %, 52 % and 10 %, respectively. The potential of using these labels to monitor the freshness of chicken breast was then examined. Only the films containing soybean protein exhibited good pH sensitivity, high structural stability, and low pigment leakage. This combination of beneficial attributes suggests that the composite films containing starch and soybean protein may be most suitable for monitoring meat freshness.

A comprehensive review on starch: Structure, modification, and applications in slow/controlled-release fertilizers in agriculture

This comprehensive review thoroughly examines starch's structure, modifications, and applications in slow/controlled-release fertilizers (SRFs) for agricultural purposes. The review begins by exploring starch's unique structure and properties, providing insights into its molecular arrangement and physicochemical characteristics. Various methods of modifying starch, including physical, chemical, and enzymatic techniques, are discussed, highlighting their ability to impart desirable properties such as controlled release and improved stability. The review then focuses on the applications of starch in the development of SRFs. It emphasizes the role of starch-based hydrogels as effective nutrient carriers, enabling their sustained release to plants over extended periods. Additionally, incorporating starch-based hydrogel nano-composites are explored, highlighting their potential in optimizing nutrient release profiles and promoting plant growth. Furthermore, the review highlights the benefits of starch-based fertilizers in enhancing plant growth and crop yield while minimizing nutrient losses. It presents case studies and field trials demonstrating starch-based formulations' efficacy in promoting sustainable agricultural practices. Overall, this review consolidates current knowledge on starch, its modifications, and its applications in SRFs, providing valuable insights into the potential of starch-based formulations to improve nutrient management, boost crop productivity, and support sustainable agriculture.

Risedronate-loaded aerogel scaffolds for bone regeneration

Sugarcane bagasse-derived nanofibrillated cellulose (NFC), a type of cellulose with a fibrous structure, is potentially used in the pharmaceutical field. Regeneration of this cellulose using a green process offers a more accessible and less ordered cellulose II structure (amorphous cellulose; AmC). Furthermore, the preparation of cross-linked cellulose (NFC/AmC) provides a dual advantage by building a structural block that could exhibit distinct mechanical properties. 3D aerogel scaffolds loaded with risedronate were prepared in our study using NFC or cross-linked cellulose (NFC/AmC), then combined with different concentrations of chitosan. Results proved that the aerogel scaffolds composed of NFC and chitosan had significantly improved the mechanical properties and retarded drug release compared to all other fabricated aerogel scaffolds. The aerogel scaffolds containing the highest concentration of chitosan (SC-T3) attained the highest compressive strength and mean release time values (415 ± 41.80 kPa and 2.61 ± 0.23 h, respectively). Scanning electron microscope images proved the uniform highly porous microstructure of SC-T3 with interconnectedness. All the tested medicated as well as unmedicated aerogel scaffolds had the ability to regenerate bone as assessed using the MG-63 cell line, with the former attaining a higher effect than the latter. However, SC-T3 aerogel scaffolds possessed a lower regenerative effect than those composed of NFC only. This study highlights the promising approach of the use of biopolymers derived from agro-wastes for tissue engineering.

Tensile Strength Improvements of Ramie Fiber Threads through Combination of Citric Acid and Sodium Hypophosphite Cross-Linking

Ramie (Boehmeria nivea) is believed to be one of the strongest natural fibers, but it still remains behind synthetic materials in terms of tensile strength. In this study, ramie materials were prepared to evaluate the modification crosslinking effect of natural fiber. The aim is to optimize various concentrations of citric acid (CA) crosslinking by adding Sodium hypophosphite (NaPO2H2), which is activated at different temperatures, to obtain the highest tensile mechanical strength. This crosslinking effect has been confirmed by FTIR to show the esterification process in the molecular structure of cellulose. The changes in the character of the fiber surface were analyzed by SEM. The tensile strength increased from 62.33 MPa for 0% CA to 124-172.86 MPa for decorticated fiber with a CA concentration of 0.75-1.875% (w/w). A significant increase in tensile strength was observed more than 19 times when CA/SHP 1% was treated at an activation temperature of 110 °C with a superior tensile strength of 1290.63. The fiber crosslinked with CA/SHP should be recommended for application of Natural Fiber Reinforced Polymer Composite (NFRPC), which has the potential to use in functional textile and industrial sector automotive or construction.

Effect of Heating and Citric Acid on the Performance of Cellulose Nanocrystal Thin Films

Cellulose nanocrystals (CNCs) were extracted from bleached cotton by sulfuric acid hydrolysis. Thin films were prepared from the aqueous suspension of CNCs by casting and evaporation with 15% glycerol as a plasticizer. Our research aimed to create stable films resistant to water. The structure and the interactions of the films were modified by short (10 min) heating at different temperatures (100, 140, and 160 °C) and by adding different amounts of citric acid (0, 10, 20, and 30%). Various analytical methods were used to determine the structure, surface properties, and mechanical properties. The interaction of composite films with water and water vapor was also investigated. Heat treatment did not significantly affect the film properties. Citric acid, without heat treatment, acted as a plasticizer. It promoted the disintegration of films in water, increased water vapor sorption, and reduced tensile strength, resulting in flexible and easy-to-handle films. The combination of heat treatment and citric acid resulted in stable liquid-water-resistant films with excellent mechanical properties. A minimum heating temperature of 120 °C and a citric acid concentration of 20% were required to obtain a stable CNC film structure resistant to liquid water.

Real-time monitoring of the starch cross-linking with citric acid by chemorheological analysis

Cross-linking has been used as a strategy to improve the mechanical properties of starch films. However, the concentration of the cross-linking agent and the cure time and temperature determine the structure and properties of the modified starch. This article, for the first time, reports the chemorheological study of cross-linked starch films with citric acid (CA) through monitoring the storage modulus as a function of time G'(t). In this study, a CA concentration of 10 phr showed a pronounced increase of G'(t) during the cross-linking of starch, followed by a constant plateau. Analyses of infrared spectroscopy validated the result chemorheological. In addition, the mechanical properties showed a plasticizing effect of the CA at high concentrations. This research demonstrated that chemorheology is a valuable tool in the study of starch cross-linking, which becomes a promising technique to evaluate the cross-linking of other polysaccharides and cross-linking agents.

A Prospective Review on the Research Progress of Citric Acid Modified Starch

Citric acid (CA) treatment is a convenient, mild and environmentally friendly strategy to modify the composition, structure and function of starch through hydrolysis and esterification, which expands the application of starch in industry. In this paper, the effects of CA modification on amylose content, amylopectin chain length distribution, microscopic morphology, solubility and swelling ability, thermodynamic properties, gelatinization properties, digestibility properties, texture properties and the film-forming properties of starch were summarized. The application status and development trend of CA modified starch were reviewed, which has important implications for the targeted utilization of CA modified starch in the future.

Preparation of Bio-Based Foams with a Uniform Pore Structure by Nanocellulose/Nisin/Waterborne-Polyurethane-Stabilized Pickering Emulsion

Bio-based porous materials can reduce energy consumption and environmental impact, and they have a possible application as packaging materials. In this study, a bio-based porous foam was prepared by using a Pickering emulsion as a template. Nisin and waterborne polyurethane (WPU) were used for physical modification of 2,2,6,6-tetramethyl piperidine-1-oxyl-oxidized cellulose nanocrystals (TOCNC). The obtained composite particles were applied as stabilizers for acrylated epoxidized soybean oil (AESO) Pickering emulsion. The stability of the emulsion was characterized by determination of the rheological properties and microscopic morphology of the emulsion. The emulsion stabilized by composite particles showed better stability compared to case when TOCNC were used. The porous foam was obtained by heating a composite-particles-stabilized Pickering emulsion at 90 °C for 2 h. SEM (scanning electron microscopy) images showed that the prepared foam had uniformly distributed pores. In addition, the thermal conductivity of the foam was 0.33 W/m·k, which was a significant decrease compared to the 3.92 W/m·k of the TOCNC foam. The introduction of nisin and WPU can reduce the thermal conductivity of the foam, and the physically modified, TOCNC-stabilized Pickering emulsion provides an effective means to preparing bio-based porous materials.

Gellan gum/bacterial cellulose hydrogel crosslinked with citric acid as an eco-friendly green adsorbent for safranin and crystal violet dye removal

In this study, ex-situ crosslinked gellan gum (GG)/bacterial cellulose (BC) hydrogels have been investigated as good absorbents for the removal of safranin and crystal violet dye pollutants. The preparation involves a cost-effective and easy-to-perform crosslinking procedure, using citric acid (CA) as a green crosslinker. The physicochemical and mechanical properties of the crosslinked hydrogels were examined by FTIR, TGA, SEM, XRD, and unconfined compression analyses. The swelling capacity of the hydrogels as a function of pH was investigated. CA depicted to improve structural stability as a crosslinker. The dye removal capacity of the hydrogels as good adsorbents was explored and showed higher efficiency in the removal of safranin dye as compared to crystal violet with optimum adsorption capacities obtained as 17.57 and 13.49 mg/g, respectively. Adsorption kinetics and isotherm models as well as thermodynamics examined. Results showed the adsorption process well fitted the pseudo 2nd-order kinetic and Langmuir-Freundlich models while temperature dependence study depicted to be exothermic. Furthermore, no significant loss of removal efficiency of the hydrogel adsorbent was observed even after five adsorption-desorption cycles. Based on the revealed results, the prepared hydrogel may serve as an effective adsorbent for the removal of dyes from the aqueous phase.

Cellulose Nanocrystals Crosslinked with Sulfosuccinic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications

Nanocellulose is a sustainable material which holds promise for many energy-related applications. Here, nanocrystalline cellulose is used to prepare proton exchange membranes (PEMs). Normally, this nanomaterial is highly dispersible in water, preventing its use as an ionomer in many electrochemical applications. To solve this, we utilized a sulfonic acid crosslinker to simultaneously improve the mechanical robustness, water-stability, and proton conductivity (by introducing -SO₃⁻H⁺ functional groups). The optimization of the proportion of crosslinker used and the crosslinking reaction time resulted in enhanced proton conductivity up to 15 mS/cm (in the fully hydrated state, at 120 °C). Considering the many advantages, we believe that nanocellulose can act as a sustainable and low-cost alternative to conventional, ecologically problematic, perfluorosulfonic acid ionomers for applications in, e. fuel cells and electrolyzers.

Fabrication and Properties of Tree-Branched Cellulose Nanofibers (CNFs) via Acid Hydrolysis Assisted with Pre-Disintegration Treatment

In this paper, the novel morphology of cellulose nanofibers (CNFs) with a unique tree-branched structure was discovered by using acid hydrolysis assisted with pre-disintegration treatment from wood pulps. For comparison, the pulps derived from both softwood and hardwood were utilized to extract nanocellulose in order to validate the feasibility of proposed material fabrication technique. The morphology, crystalline structures, chemical structures, and thermal stability of nanocellulose were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), as well as thermogravimetric analysis (TGA). Prior to acid hydrolysis, softwood and hardwood pulps underwent the disintegration treatment in the fiber dissociator. It has been found that nanocellulose derived from disintegrated pulps possesses much longer fiber length (approximately 5-6 μm) and more evident tree-branched structures along with lower degree of crystallinity when compared with those untreated counterparts. The maximum mass loss rate of CNFs takes place at the temperature level of approximately 225 °C, and appears to be higher than that of cellulose nanowhiskers (CNWs), which might be attributed to an induced impact of amorphous content. On the other hand, disintegration treatment is quite beneficial to the enhancement of tensile strength of nanocellulose films. This study elaborates a new route of material fabrication toward the development of well-tailored tree-branched CNFs in order to broaden the potential widespread applications of nanocellulose with diverse morphological structures.

Preparation of flexible and UV-blocking films from lignin-containing cellulose incorporated with tea polyphenol/citric acid

Lignin-containing bamboo cellulose, fractionated from a pilot-scale microwave liquefaction of bamboo was dissolved in tetrabutylammonium acetate/dimethyl sulfoxide (TBAA/DMSO) for the fabrication of highly flexible, transparent and UV-blocking films. Tea polyphenol (TP) or citric acid (CA) was added during the dissolving process in order to modify the film's properties. The results showed that the addition of TP obviously improved the elongation at break (triple that of the control) and UV-blocking ability of the films. Both the addition of TP and CA could increase the water contact angle of the films. The films incorporated with TP and CA were much more thermal stable than previously reported similar films. The proposed film fabrication mechanism revealed that stable hydrogen bonds formed between the lignin-cellulose matrix and TP/CA, resulting in the enhancement on the properties of the films. This present study showed that lignin-containing cellulose with the incorporation of TP/CA had great potential in the preparation of films in place of plastic.

A simple preparation of low water-soluble crosslinking starch-based foam containing palm oil: Thermo-physicochemical properties

A simple preparation method was established for a low water-soluble citric acid crosslinking starch-based foam containing palm oil. The method was performed by pouring the boiling citric acid solution into the starch compound unlike the citric acid starch crosslinking by conventional solution casting. Thermo-physicochemical properties of the starch-based foams were examined. The I3300/I1149 intensity ratio of non-citric acid-containing foam was higher, suggesting greater amounts of the available -OH groups. The addition of citric acid into the starch matrix exhibited weaker thermal stability that was attributed to the lower thermal stability of the substituted ester bonds. The increment of citric acid concentration increased thermoplastic starch foams densities as well as their cell wall thickness. No differences in moisture absorption behavior were observed after soaking in water, the non-citric acid-filled foam exhibited dissolution and changed from its original shape upon drying. Experimental results showed a promising alternative methodology to prepare low water-soluble citric acid crosslinked starch-based foam to replace conventional solution casting.

Effect of the addition of fique bagasse microparticles in obtaining a biobased material based on cassava starch

The indiscriminate accumulation of plastic waste has prompted research that leads to obtaining biobased materials. The research aim was to evaluate the effect of incorporating fique bagasse microparticles (FBM) in a cassava starch-based foamed material. First, the FBM extraction conditions were established by acid hydrolysis, for which the effect of acid concentration (5, 10 and 15% H₂SO₄), temperature (70, 80 and 90 °C) and extraction time (3, 5 and 7 h) on particle size, functional groups, color, and thermal properties was evaluated. The addition of FBM to the foamed material was then carried out. To do this, a completely randomized design with five treatments (0, 0.5, 0.75, 1.0 and 1.25% FBM) was evaluated. The response variables were the apparent density, expansion and spring index, compressibility, water absorption, thermal properties and FTIR. The results showed that the acid concentration, temperature and time had an effect on the morphological, chemical and thermal properties of FBM, with 10%, 70 °C and 7 h being the conditions that allowed obtaining the smallest particle size (61.69 ± 12.88 μm²). Moreover, the FBM concentration had a significant effect on the physical and mechanical properties of the foam, unleashing the treatment properties of 0.75%. This indicates that FBM have potential for use in obtaining biobased materials.

Predicting mechanical performance of starch-based foam materials

Variations in mixture proportions of plasticizers, additives, and crosslinking agents have significant impacts on mechanical performance of starch-based foam materials. In particular, starch/ethylene-vinyl acetate (EVA) foam materials have been developed with improved mechanical strength by optimizing the formulation. There is a lack of numerical correlations that could help analyze the effects of components and provide a predictive method for future research. In this study, we develop simple and accurate predictions for tensile strength and resilience based on mixture proportions of components for starch-based/EVA foam materials. The models constructed might be used to help design mixture proportions of starch-based foam materials. By combining optimization results from the Taguchi method and machine learning approaches, it is expected that more quantitative data can be extracted from fewer experimental trials at the same time.

Thermal, mechanical, and rheological properties of micro-fibrillated cellulose-reinforced starch foams crosslinked with polysiloxane-based cross-linking agents

The disposal of non-degradable plastic packaging and plastic pollution are widespread environmental problems. The development of a fully biodegradable alternative foam packaging with excellent water barrier properties from polysaccharides is quite challenging. In this work, micro-fibrillated cellulose fiber-reinforced starch foams (MFC-SFs) were developed by crosslinking with two poly(siloxane)-based crosslinking agents that enhanced their strength and water barrier properties. The polysiloxane crosslinking agents studied were a cationic trimethylsiloxy-terminated poly(aminoethyl aminopropyl methyl siloxane)-co-poly(dimethylsiloxane) or PAEAPS-co-PDMS, and a non-ionic siloxy-terminated poly(dimethylsiloxane) or TMS-t-PDMS. The applied dosage of polysiloxane crosslinking agents was varied from 1.33 to 5.32% to achieve the optimum strength and moisture barrier properties. The results show that the tensile strength increased from 1.78 MPa for the control to 2.76 MPa for the MFC-SF crosslinked with 5.32% PAEAPS-co-PDMS. The corresponding tensile strength for the MFC-SF crosslinked with TMS-t-PDMS was 2.53 MPa, which is still considerably higher than the control MFC-SF. The water absorption also decreased from 326.8% for the control to 102.5% and 79.8% for the MFC-SFs crosslinked with 5.32% PAEAPS-co-PDMS and TMS-t-PDMS respectively. The crosslinking of MFC-SFs with TMS-t-PDMS provided better hydrophobicity compared to the crosslinking with PAEAPS-co-PDMS. The developed packaging could be a promising alternative to non-degradable foam packaging.

Crosslinked starch-coated cellulosic papers as alternative food-packaging materials

In general, during the production of cellulosic materials for food-packaging applications, lignin and other amorphous components are usually removed via the pulping and multilevel bleaching process to entirely separate them from the fiber.

Biobased composites from agro-industrial wastes and by-products

The greater awareness of non-renewable natural resources preservation needs has led to the development of more ecological high-performance polymeric materials with new functionalities. In this regard, biobased composites are considered interesting options, especially those obtained from agro-industrial wastes and by-products. These are low-cost raw materials derived from renewable sources, which are mostly biodegradable and would otherwise typically be discarded. In this review, recent and innovative academic studies on composites obtained from biopolymers, natural fillers and active agents, as well as green-synthesized nanoparticles are presented. An in-depth discussion of biobased composites structures, properties, manufacture, and life-cycle assessment (LCA) is provided along with a wide up-to-date overview of the most recent works in the field with appropriate references. Potential uses of biobased composites from agri-food residues such as active and intelligent food packaging, agricultural inputs, tissue engineering, among others are described, considering that the specific characteristics of these materials should match the proposed application.

Applications of Plant Polymer-Based Solid Foams: Current Trends in the Food Industry

Foams are a type of material of great importance, having an extensive range of applications due to a combination of several characteristics, such as ultra-low density, tunable porous architecture, and outstanding mechanical properties. The production of polymer foams worldwide is dominated by those based on synthetic polymers, which might be biodegradable or non-biodegradable. The latter is a great environmental concern and has become a major waste management problem. Foams derived from renewable resources have aroused the interest of researchers, solid foams made from plant polymers in particular. This review focuses on the development of plant polymer-based solid foams and their applications in the food industry over the last fifteen years, highlighting the relationship between their material and structural properties. The applications of these foams fall mainly into two categories: edible foams and packaging materials. Most plant polymers utilized for edible applications are protein-based, while starch and cellulose are commonly used to produce food packaging materials because of their ready availability and low cost. However, plant polymer-based solid foams exhibit some drawbacks related to their high water absorbency and poor mechanical properties. Most research has concentrated on improving these two physical properties, though few studies give a solid understanding and comprehension of the micro- to macrostructural modifications that would allow for the proper handling and design of foaming processes. There are, therefore, several challenges to be faced, the control of solid foam structural properties being the main one.

Carbon dots crosslinked chitosan/cellulose sponge capture of methyl blue by an adsorption process

For environmental protection, organic dyes and solvents of industrial wastewater must be eliminated. Here, a citric acid-based carbon dots (CA-CDs) crosslinked chitosan/microcrystalline cellulose (CS/MCC/CA-CDs) sponge was synthesized to study its adsorption performance for methyl blue (MB) dye. The morphology of the sponge was a tangled fibre with a bundle formed by hydrogen bonds between CA-CDs and the CS/MCC composite matrix. The abundant amount of tangled fibre bundle units can offer plentiful active adsorption sites to collect the dye molecules. The adsorption capacity of the CS/MCC/CA-CDs sponge toward MB was 306.8 mg/g at pH 10 and a temperature of 298 K. In addition, the pseudo-second-order kinetic model was matched with the adsorption kinetic experimental data, and the adsorption isotherm data can be described by the Langmuir models. This study proposed that the CS/MCC/CA-CDs sponge adsorbent creates tremendous potential application value in wastewater treatment due to its fast kinetics, high adsorption capacity, simple preparation, and eco-friendly properties.

Effect of acetylated starch on the development of peanut skin-cassava starch foams

Cassava starch was modified by acetylation to obtain modified starches with a degree of substitution (DS) of 0.5 and 1.5. The acetylated cassava starches presented a reduction in temperature gelatinization and enthalpy, water solubility, and power swelling, in addition to a loss of crystallinity compared to native cassava starches. Acetylated cassava starch was used to the development of foams based on native cassava starch, 24% (w/w) of peanut skin, and 13% (w/w) of glycerol. It was used blends of native cassava starch and acetylated cassava starch with ratios of 100/0, 90/10, 80/20, 70/30, and 60/40. The foams containing acetylated cassava starch with DS = 0.5 exhibited a reduction in water absorption capacity (WAC) for water contact time of 30 min. Foams containing acetylated cassava starch with DS = 1.5 did not show a significant difference in WAC compared to foams made using only native cassava starch. The use of 30% (w/w) of acetylated cassava starch, independently of DS (0.5 or 1.5), resulted in faster degradation of foams than those without modified starches.

Research of Wood Waste as a Potential Filler for Loose-Fill Building Insulation: Appropriate Selection and Incorporation into Polyurethane Biocomposite Foams

Currently, the recycling potential of wood waste (WW) is still limited, and in a resource efficiency approach, recycling WW in insulation materials, such as polyurethane (PUR), appears as an appropriate solution. It is known that the quality of WW is the main aspect which influences the stability of the final products. Therefore, the current study analyses different WW-based fillers as possible modifiers for polyurethane biocomposite foams for the application as loose-fill materials in building envelopes. During the study of WW-based fillers, it was determined that the most promising filler is wood scobs (WS) with a thermal conductivity of 0.0496 W/m·K, short-term water absorption by partial immersion—12.5 kg/m², water vapour resistance—0.34 m²·h·Pa/mg and water vapour diffusion resistance factor—2.4. In order to evaluate the WS performance as a filler in PUR biocomposite foams, different ratios of PUR binder and WS filler (PURb/WS) were selected. It was found that a 0.40 PURb/WS ratio is insufficient for the appropriate wetting of WS filler while a 0.70 PURb/WS ratio produced PUR biocomposite foams with the most suitable performance: thermal conductivity reduced from 0.0523 to 0.0476 W/m·K, water absorption—from 5.6 to 1.3 kg/m², while the compressive strength increased from 142 to 272 kPa and the tensile strength increased from 44 to 272 kPa.

Highly Stretchable and Flexible Melt Spun Thermoplastic Conductive Yarns for Smart Textiles

This study demonstrates a scalable fabrication process for producing biodegradable, highly stretchable and wearable melt spun thermoplastic polypropylene (PP), poly(lactic) acid (PLA), and composite (PP:PLA = 50:50) conductive yarns through a dip coating process. Polydopamine (PDA) treated and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated conductive PP, PLA, and PP/PLA yarns generated electric conductivity of 0.75 S/cm, 0.36 S/cm and 0.67 S/cm respectively. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the interactions among the functional groups of PP, PLA, PP/PLA, PDA, and PEDOT:PSS. The surface morphology of thermoplastic yarns was characterized by optical microscope and Scanning Electron Microscope (SEM). The mechanical properties of yarns were also assessed, which include tensile strength (TS), Young’s modulus and elongation at break (%). These highly stretchable and flexible conductive PP, PLA, and PP/PLA yarns showed elasticity of 667%, 121% and 315% respectively. The thermal behavior of yarns was evaluated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Wash stability of conductive yarns was also measured. Furthermore, ageing effect was determined to predict the shelf life of the conductive yarns. We believe that these highly stretchable and flexible PEDOT:PSS coated conductive PP, PLA, and PP/PLA composite yarns fabricated by this process can be integrated into textiles for strain sensing to monitor the tiny movement of human motion.

The Effect of Different Plant Oil Impregnation and Hardening Temperatures on Physical-Mechanical Properties of Modified Biocomposite Boards Made of Hemp Shives and Corn Starch

In this study, tung tree and linseed drying oils, as well as semi-drying hempseed oil, were analyzed as the protective coatings for biocomposite boards (BcB) made of hemp shives, corn starch binder, and the performance-enhancing additives. The hydrophobization coatings were formed at 40, 90, and 120 °C temperatures, respectively. The physical-mechanical properties such as the compressive strength, thermal conductivity, dimensional stability, water absorption, and swelling were tested. In addition, scanning electron microscopy (SEM) was employed for the analysis of the board microstructure to visualize the oil fills and impregnation in pores and voids. It was demonstrated that the compressive strength of oil-modified BcBs compared to uncoated BcBs (at 10% of relative deformation) increased by up to 4.5-fold and could reach up to 14 MPa, water absorption decreased up to 4-fold (from 1.34 to 0.37 kg/m²), swelling decreased up to 48% (from 8.20% to 4.26%), whereas the thermal conductivity remained unchanged with the thermal conductivity coefficient of around 0.085 W/m·K. Significant performance-enhancing properties were obtained due to the formation of a protective oil film when the tung tree oil was used.

Preparation and Properties of Cassava Residue Cellulose Nanofibril/Cassava Starch Composite Films

Because of its non-toxic, pollution-free, and low-cost advantages, environmentally-friendly packaging is receiving widespread attention. However, using simple technology to prepare environmentally-friendly packaging with excellent comprehensive performance is a difficult problem faced by the world. This paper reports a very simple and environmentally-friendly method. The hydroxyl groups of cellulose nanofibrils (CNFs) were modified by introducing malic acid and the silane coupling agent KH-550, and the modified CNF were added to cassava starch as a reinforcing agent to prepare film with excellent mechanical, hydrophobic, and barrier properties. In addition, due to the addition of malic acid and a silane coupling agent, the dispersibility and thermal stability of the modified CNFs became significantly better. By adjusting the order of adding the modifiers, the hydrophobicity of the CNFs and thermal stability were increased by 53.5% and 36.9% ± 2.7%, respectively. At the same time, the addition of modified CNFs increased the tensile strength, hydrophobicity, and water vapor transmission coefficient of the starch-based composite films by 1034%, 129.4%, and 35.95%, respectively. This material can be widely used in the packaging of food, cosmetics, pharmaceuticals, and medical consumables.