Utilization of hydroxyl-compatible fillers in citric acid-crosslinked thermoplastic starch foam: Communication of strengths and limitations

Waste from non-degradable packaging materials poses a serious environmental risk and has led to interest in developing sustainable bio-based packaging materials. Sustainable packaging materials have been made from diverse naturally derived materials such as bamboo, sugarcane, and corn starch. In this study, we made a sustainable packaging film using chitosan extracted from the biomass of yellow mealworm (Tenebrio molitor) shell waste. The extracted chitosan was used to create films, cross-linked with citric acid (CA) and with the addition of glycerol to impart flexibility, using the solvent casting method. The successful cross-linking was evaluated using Fourier-Transform Infrared (FTIR) analysis. The CA cross-linked mealworm chitosan (CAMC) films exhibited improved water resistance with moisture content reduced from 19.9 to 14.5%. Improved barrier properties were also noted, with a 28.7% and 10.2% decrease in vapor permeability and vapor transmission rate, respectively. Bananas were selected for food preservation, and significant changes were observed over a duration of 10 days. Compared to the control sample, bananas packaged in CAMC pouches exhibited a lesser loss in weight because of excellent barrier properties against water vapor. Moreover, the quality and texture of bananas packaged in CAMC pouch remained intact over the duration of the experiment. This indicates that adding citric acid and glycerol to the chitosan structure holds promise for effective food wrapping and contributes to the enhancement of banana shelf life. Through this study, we concluded that chitosan film derived from mealworm biomass has potential as a valuable resource for sustainable packaging solutions, promoting the adoption of environmentally friendly practices in the food industry.

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

Background: Thermoplastic expandable microspheres (TEMs) are spherical particles that consist of a polymer shell encapsulating a low boiling point liquid hydrocarbon that acts as the blowing agent. When TEMs are heated at 80-190 °C, the polymer shell softens, and the hydrocarbon gasifies, causing the microspheres to expand, leading to an increase in volume and decrease in density. TEMs are used in food packaging, elastomeric cool roof coatings, shoe soles, fiber and paper board, and various applications in the automotive industry. It is noted that TEMs are known by their brand name ‘Expancel’, which is also used to refer TEMs in this paper. Objective: The objective of this work was to develop and characterize forms prepared from TEMs with/without carbon nanofibers (CNFs) coatings to study the effect of CNFs on structural, thermal, and mechanical properties. Method: Sonochemical method was used to coat TEMs with various weight percentages (1, 2, and 3%) of CNF. Neat foam (without CNF) and composite foams (TEMs coated with various wt.% of CNF) were prepared by compression molding the TEMs and TEMs-CNF composites powders. Thermal and mechanical properties of the neat and composite foams were investigated. Result: The mechanical properties of the composite foam were notably improved, which is exhibited by a 54 % increase in flexural modulus and a 6% decrease in failure strain with the TEMs-(2 wt.% CNF) composite foam as compared to the neat foam. Improvement in thermal properties of composite foam was demonstrated by a 38% increase in thermal stability at 800ºC with the TEMs-( 1 wt.% CNF) composite foam as compared to the neat foam. However, no change in the glass transition of TEMs was observed with the CNF coating. SEM-based analysis revealed that CNFs were well dispersed throughout the volume of the TEMs matrix, forming a strong interface. Conclusions: Straightforward sonochemical method successfully triggered efficient coating of TEMs with CNFs, resulting in a strong adhesion interface. The mechanical properties of composite foams increased up to 2% of CNFs coating and then decreased with the higher coating, presumably due to interwoven bundles and aggregation of CNFs, which might have acted as critical flaws to initiate and propagate cracking. Thermal properties of foams increased with the CNFs coating while no change in glass transition temperature was observed due to coating.

Over the last two decades, there has been growing interest from all stakeholders (government, manufacturers, and consumers) to make packaging more sustainable. Paper is considered one of the most environmentally friendly materials available. A qualitative study investigating consumers’ expectations and opinions of sustainable paper-based packaging materials was conducted where 60 participants took part in focus group sessions organized in two stages. In the first stage, participants expressed their opinions about currently available packages in the market and their expectations about a sustainable packaging material. In the second stage of the study, they evaluated five paper-based prototype packages for two product categories (biscuits and meat). Too much plastic and over-packaging were the key issues raised for current packages. Price and quality were the main driving forces for consumers’ purchase intent. While participants were impressed by the sustainable nature of the prototypes, the design did not necessarily meet their expectations, and they were not willing to pay more for a sustainable package. The key message that emerged from the discussions was the “3Rs”—Reduce, Reuse, and Recycle”—which should be the main points to consider when designing a sustainable packaging.

Flexible poly(butylene adipate-co-butylene terephthalate) enabled high-performance polylactide/wood fiber biocomposite foam

The aim of this study has been to develop processing techniques for novel bioresorbable thermoplastic cellular composites, reinforced with continuous inorganic fibres, for use as biodegradable scaffolds for bone tissue engineering. As the implanted composite scaffold starts to degrade, it should be progressively replaced by natural bone tissue, which should consequently support increasing proportions of the applied mechanical loads. In order to simulate natural high performance porous structures such as bone or light wood, composites with simultaneous gradients in fibre content and porosity were studied. In order to carry out investigations over wide ranges of fibre content and porosity and to ensure biocompatibility and bioresorbability, it was decided to focus on foamable poly(L-lactic acid) (PLA) and continuous glass fibres. As well as improved mechanical reinforcement due to the high aspect ratio, the use of continuous glass fibres offers the possibility of achieving higher loadings than with short fibres or particles, increasing the potential range of mechanical properties. For processing the composites, a fibre winding technique developed in house was used to prepare unidirectional preforms with gradient structures tailored at the fibre bundle level. PLA fibre bundles, containing 36 monofilaments were prepared on a spinning line, and mingled with glass fibre bundles comprising 250 or 1000 monofilaments. During the winding process, the PLA fibres were intimately mixed with the reinforcing fibres, to ensure a good impregnation during subsequent processing steps. Moreover it was possible to maintain the relative positions of the fibres during pre-consolidation of graded composites. The resulting preforms had a porosity of 25% and could be further consolidated to decrease the porosity, or foamed in an autoclave to obtain cellular composites (foams) with porosities of up to 90%. It was observed that, independently of the applied foaming conditions, the presence of continuous fibres reduced the porosity by an amount equivalent to twice the fibre volume fraction. This processing method provided composites with a simultaneous gradient in fibre content and porosity. In order to predict the Young's modulus and the collapse strength of the cellular composites a model was proposed, which combines the buckling of composite columns within a porous structure with the property predictions for neat polymer foams. In neat foams with a porosity of 60%, the Young's modulus was calculated to be 0.25 GPa. By adding a fibre volume fraction of 14% the modulus reached 1.2 GPa. The respective collapse strengths were 5 MPa and 16 MPa. Experimental results were consistent with the predictions and validated the model. The model determines the fibre content required for composites with a given porosity and stiffness. Gradient cellular composites were obtained with a range of porosity between 50% to 90% and a range of stiffness between 100 and 1500 MPa. Furthermore the processing parameters can be adjusted to maintain a desired porosity when fibres are added. Thus, composites that fulfill the mechanical requirements for bone scaffolds can be achieved in a rational manner. The long term behaviour of the foams was tested under physiological conditions. Viscoelasticity tests provided evidence for the important role of the unidirectionally oriented fibres. Whereas the cells in neat foams collapsed after at most two days when loaded at 0.69 MPa, the fibre reinforced foams resisted longer and their creep strain was well described by a power law. The fatigue properties were compared to reported values of natural trabecular bone. None of the neat foams with a porosity of 74% resisted to the first load cycle of 7.3 MPa. With a fibre volume fraction of 11% and a comparable porosity of 72%, the composite scaffolds resisted for at least 11'000 loading cycles. To compare, trabecular human bone failed after 1909 cycles, when loaded with 8.5 MPa. It was concluded that the reinforced composites have the potential to replace natural bone. Preliminary in vitro results with human foetal osteoblasts and in vivo tests on femurs of rats were promising because the cells proliferated well on the composite substrates. Further investigations for applications in bone tissue engineering can be planned. Furthermore, the studied process and the obtained results are envisaged for other material systems to prepare cellular composites for novel lightweight applications in transportation and building industry.

Preparation and characterization of carbon nanotubes/chitosan composite foam with enhanced elastic property

A novel composite foam material for blocking air leakage in coal mine was developed. In order to examine the performance of the new composite foam, the foaming property, mechanical property, microstructure, thermal stability, and flame resistance of the composite foams, polyurethane foams, phenolic foams, and urea-formaldehyde foams were investigated. The results show that the composite foam had the biggest compressive strength, thermal stability, and flame resistance. Moreover, composite foam had the lowest foaming temperature and shrinkage, indicating that it had small risk in causing spontaneous combustion of coal, and it exhibited good air leakage blocking effect. Field application showed that composite foam could effectively block air leakage in goaf. Thus, composite foam materials were considered to be the potential candidates for blocking air leakage in coal mines to prevent spontaneous combustion of coal.

Polyurethane (PU) composite foams were successfully reinforced with different concentrations (1 wt%, 2 wt%, 5 wt%) of nutmeg filler. The effect of nutmeg filler concentration on mechanical, thermal, antimicrobial and anti-aging properties of PU composite foams was investigated. PU foams were examined by rheological behavior, processing parameters, cellular structure (Scanning Electron Microscopy analysis), mechanical properties (compression test, impact test, three-point bending test, impact strength), thermal properties (Thermogravimetric Analysis), viscoelastic behavior (Dynamic Mechanical Analysis) as well as selected application properties (thermal conductivity, flammability, apparent density, dimensional stability, surface hydrophobicity, water absorption, color characteristic). In order to Disc Diffusion Method, all PU composites were tested against selected bacteria (Escherichia coli and Staphylococcus aureus). Based on the results, it can be concluded that the addition of 1 wt% of nutmeg filler leads to PU composite foams with improved compression strength (e.g. improvement by ~19%), higher flexural strength (e.g. increase of ~11%), improved impact strength (e.g. increase of ~32%) and comparable thermal conductivity (0.023–0.034 W m−1 K−1). Moreover, the incorporation of nutmeg filler has a positive effect on the fire resistance of PU materials. For example, the results from the cone calorimeter test showed that the incorporation of 5 wt% of nutmeg filler significantly reduced the peak of heat release rate (pHRR) by ca. 60% compared with that of unmodified PU foam. It has been also proved that nutmeg filler may act as a natural anti-aging compound of PU foams. The incorporation of nutmeg filler in each amount successfully improved the stabilization of PU composite foams. Based on the antibacterial results, it has been shown that the addition of nutmeg filler significantly improved the antibacterial properties of PU composite foams against both Gram-positive and Gram-negative bacteria.

In this study, we report an optimization study on fig foam composition and hot air/microwave‐assisted foam mat drying (FMD) at different conditions to produce fig powder. The effects of foam composition on foam stability and capacity were evaluated. The optimum ratio of fig, egg white, carboxymethyl cellulose, and maltodextrin was determined as 52.9, 28.9, 0.8, and 17.4% (wt/wt), respectively, targeting maximum foam capacity and minimum drainage volume, that is, maximum foam stability. The effects of drying methods and their conditions were investigated on the drying rate of fig foam and physicochemical properties of fig powder. Moisture content, water activity, particle and bulk properties, and hydroxymethylfurfural and total phenolic contents of FMD fig powder were analyzed to understand the effect of drying methods and conditions on the physicochemical properties of fig powder.Practical applicationsAlthough fig fruit is generally dried as a whole, the ready‐to‐eat foods in the food market are mostly in powder form. That is why the powdering fig fruit by an appropriate drying method is essential. In this study, we report the foam mat‐dried (FMD) fig fruit powder. The fig foam composition was optimized. The fig foam was dried through hot air and microwave separately. The results showed that the foam capacity and stability of the fig powder highly depend on the foam composition. Microwave drying method was found more efficient than the hot air in the sense of time. Besides, the higher foam thickness provided more hydroxymethylfurfural content in the fig powder. The drying method and conditions were found to be important to produce a high‐quality FMD fig powder.

Perspectives on sustainable food packaging:– is bio-based plastics a solution?

Polyurethane (PU) foam is most commonly used in thermal insulation in cold storage applications but it lacks thermal energy storage characteristics. In the present work, a phase change material (PCM) n‐tetradecane is microencapsulated with poly(methyl methacrylate‐co‐methacrylic acid) using oil‐in‐water emulsion polymerization followed by incorporation into the PU foam formulation to fabricate composite foam. The purpose of the study was to combine thermal insulation along with thermal energy storage characteristics into PU foam. The phase change enthalpy of PU foam was improved from 22.43 to 55.46 J g−1 by changing the microcapsule loading fraction from 10% to 30%. The composite PU foam exhibits good thermal reliability even after 100 thermal cycling tests. The morphological observation confirms a decrease in cell size while increasing the microcapsule content. It is found that microcapsule addition has no effect on the thermal stability of PU foam. A prototype has been fabricated and tested, showing an enhancement in the thermal energy storage capacity of PU composite foam. This performance makes this PU‐PCM system feasible for cold energy storage applications. © 2022 Society of Industrial Chemistry.

Reducing the use of petrochemical-based polyurethane foams in thermal insulation applications is necessary to reduce environmental impacts.Natural fibers as fillers have emerged as promising ecological alternatives, promoting environmentally friendly and sustainable material practices.This study aimed to evaluate the mechanical and thermal properties of eco-friendly polyurethane foam composites containing bagasse fiber (BF) and rice husk (RH) waste.Rigid polyurethane foam (PUR) composites with BF and RH waste particles were prepared at different filler loading levels (20%, 30%, and 40%).Density, mechanical properties, thermal conductivity, thermal stability, and morphology of the composites were evaluated.The results showed that the density of the PUR composites with the BF and RH particles increased along with filler addition.Higher composite density led to increased thermal conductivity.The mechanical properties, bending strength, and bending modulus of the PUR composites with BF and RH were lower than those of pure PUR and decreased further with filler content.However, combining both fillers increased the mechanical properties by up to 172%.Thermal conductivity analysis indicated that thermal resistance decreases as filler content increases.However, the thermal conductivity values (0.0275-0.0393W/mK) demonstrate competitive performance, comparable to conventional insulation materials, while supporting sustainability through waste utilization and reduced PUR consumption.This material shows strong potential as a thermal insulation solution for buildings and sustainable construction, particularly in the regions with abundant agricultural waste.

There is an ongoing unmet global need to manufacture novel sustainable liquid packaging materials, that are not based on plastic film or aluminum foil. Superhydrophobic coating technologies have been proposed for developing more sustainable packaging materials. In this study, the underlying engineering principles for fabricating superhydrophobic surfaces proposed for liquid packaging are investigated, including but not limited to the substrates used and engineering properties of the surfaces. Specifically, to improve the engineering performance of superhydrophobic paper for use in packaging, the feasibility of combining platy montmorillonite (MMT, for its barrier properties) and nano-rolling-pin-shaped precipitated calcium carbonate (PCC, for its superhydrophobicity) into multifunctional coating layers is investigated. Water droplet evaporation experiments are performed to identify how subtle changes in the morphological structures of as-prepared superhydrophobic paper samples can produce a useful roughness structure for packaging applications. Paperboard, which is widely utilized in packaging, is chosen as a substrate to study the challenges of fabricating superhydrophobic paperboards for use in packaging. The results of this study provide engineering principles for using sustainable paper-based materials with a dual-scale roughness structure and barrier properties in liquid packaging applications.Graphical abstract

Preparation of Ag/TiO 2 composite foams via Pickering emulsion for bactericide and photocatalysis