Effect of humidity on mechanical, thermal and barrier properties of EVOH films

Effect of Graphene Oxide Localization on Morphology Development and Rheological and Mechanical Properties of Poly(lactic acid)/ethylene vinyl Alcohol Copolymer Blend Composites: A Comprehensive Study

This study investigates the rheological, morphological, and mechanical properties of melt-processed polylactide/ethylene vinyl alcohol (70PLA/30EVOH) blend composites containing 0.25, 0.5, and 1 wt.% of graphene oxide (GO) nanoplates. Thermodynamic-based suggested the localization of nanoparticles in EVOH, SEM studies showed that the introduction of GO to the blend increased dispersed droplet size, which was attributed to the localization of GO within EVOH, as confirmed by TEM. The rheology results indicated a decrease in the elasticity for the composite containing 0.25 wt.% of GO compared to the neat blend, which was attributed to the sliding effect of the added GO nanoplatelets. However, samples containing higher amounts of GO nanoplatelets exhibited more excellent elasticity than the neat blend. The increased elasticity was suggestively attributed to the dominance of hydrodynamic interactions, the physical network of added nanoplatelets, and polymer/GO interactions over the sliding role of the GO nanoplatelets at higher loadings. In addition, the effect of the order of mixing was investigated, and the premixing of PLA and GO exhibited a decrease in the droplet radius compared to the neat blend. It was ascribed to the localization of GO nanosheets in the PLA and interface, which was confirmed by rheological results and mechanical assessments.

Polycaprolactone composite films infused with hyperbranched polyester/reduced graphene oxide: influence on biodegradability, gas/water transport and antimicrobial properties for sustainable packaging

Biodegradable polymers have gained great interest as ecofriendly packaging materials. However, addition of suitable fillers to the polymer matrix enhances their barrier and mechanical properties besides gaining new features such as bactericidal activity. This work deals with investigation of mechanical, gas/water transport properties and biodegradability performance of films based on polycaprolactone (PCL) reinforced by 1wt% of reduced graphene oxide (RGO) or modified graphene (mRG). To achieve this goal, nanosheets of RGO were firstly prepared then their surfaces were modified through in situ polymerization of hyperbranched polyester (PES) to obtain mRG. Then PCL was loaded with both fillers, and the nanocomposite films were prepared by a casting technique. Studying of the thermal properties of the films showed that the addition of RGO or mRG had no influence on the crystallinity of the PCL matrix. Although the mechanical characteristics of the PCL did not change when either filler was added, there was an increase in permeability and diffusivity in the presence of the fillers regardless of their composition. Nevertheless, the nanocomposites demonstrated antimicrobial properties against S. aureus and E. coli as models for Gram-positive and Gram-negative bacteria, respectively. The biodegradability test performed on the prepared film PCL, and those containing 1% of the filler, PCL/RGO, and PCL/mRG, emphasized that the film degradation became pronounced after three months for all samples.

Recent Progress of Biodegradable Polymer Package Materials: Nanotechnology Improving Both Oxygen and Water Vapor Barrier Performance

Biodegradable polymers have become a topic of great scientific and industrial interest due to their environmentally friendly nature. For the benefit of the market economy and environment, biodegradable materials should play a more critical role in packaging materials, which currently account for more than 50% of plastic products. However, various challenges remain for biodegradable polymers for practical packaging applications. Particularly pertaining to the poor oxygen/moisture barrier issues, which greatly limit the application of current biodegradable polymers in food packaging. In this review, various strategies for barrier property improvement are summarized, such as chain architecture and crystallinity tailoring, melt blending, multi-layer co-extrusion, surface coating, and nanotechnology. These strategies have also been considered effective ways for overcoming the poor oxygen or water vapor barrier properties of representative biodegradable polymers in mainstream research.

Effect of Temperature and Humidity on the Water and Dioxygen Transport Properties of Polybutylene Succinate/Graphene Nanoplatelets Nanocomposite Films

Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on the crystalline microstructure. Moisture sorption at 10 °C, 25 °C, and 40 °C were analyzed and modeled using the Guggenheim, Andersen, and De Boer (GAB) equation and Zimm-Lundberg theory, allowing for a phenomenological analysis at the molecular scale. An understanding of the transport sorption properties was proposed by the determination of the molar heat of sorption (ΔH_s), and the activation energy of the diffusion (E_d) of water in the matrix since both solubility and diffusion are thermo-activable properties. Both ΔH_s and E_d showed a good correlation with the water clustering theory at high water activity. Water and dioxygen permeabilities (PH2O and PO2) were determined as a function of temperature and water activity. PH2O and PO2 decreased with the addition of a small amount of GnP, regardless of the studied temperature. Moreover, the evolution of PH2O as a function of water activity was driven by the solubility process, whereas at a given water activity, PH2O was driven by the diffusion process. Activation energies of the permeability (E_p) of water and dioxygen showed a dependency on the nature of the permeant molecule. Finally, from the ΔH_s, E_d, and E_p obtained values, the reduction in water permeability with the addition of a low content of GnP was attributed mainly to a tortuosity effect without diffusive interfaces rather than a significant change in the transport property mechanism.

Effect of membrane performance variability with temperature and feed composition on pervaporation and vapor permeation system design for solvent drying

BACKGROUND

The presence of water in organic solvents and biofuels can complicate their production and reuse because many hydrophilic solvents form difficult-to-separate mixtures with water (e.g., azeotropes). Pervaporation (PV) and vapor permeation (V⋅P) remove water from such mixtures via selective solution-diffusion transport through a membrane material. A recent article reviewed design factors that impact the effectiveness of PV/V⋅P solvent dehydration processes (J. Chem. Technol. Biotechnol 95: 495-512 (2020)). For the sake of simplicity, the earlier work assumed constant membrane permeabilities. The objective here is to explore the impact of variable permeabilities on predictions of PV/V⋅P system performance.

RESULTS

A multiparameter expression relating permeability to process conditions was incorporated into the spreadsheet calculators from the previous work. Use of the expression was demonstrated with literature ethanol/water PV data for a NaA zeolite material and two poly (vinyl alcohol) (PVA) membranes. The variable permeabilities of the membranes yielded membrane area requirements that were 20-30% different from those calculated using permeances fixed at either end of the target water range. The impact of composition-dependent permeabilities was most pronounced on the fraction of ethanol transferred to the permeate for the NaA membrane.

CONCLUSION

The inclusion of membrane permeabilities that vary with fluid composition and temperature noticeably altered predictions of the membrane area required to carry out water removal from ethanol by PV and of the transfer of ethanol to the permeate stream. Unless a PV/V⋅P process is expected to operate at a constant temperature and in a narrow concentration range, process performance estimates would be improved by inclusion of concentration- and temperature-dependent permeabilities or permeances.

Controlled release antimicrobial sachet prepared from poly(butylene succinate)/geraniol and ethylene vinyl alcohol coated paper for bread shelf-life extension application

This research aims to develop white bread shelf-life extension sachet with controlled release of antimicrobial agent prepared from multicomponent bio-based materials. The structure of antimicrobial sachet consists of two major parts i.e., controlled release part and active part. The first part produced from paper coated with ethylene vinyl alcohol (EVOH). The second one was an active part which produced from biodegradable poly(butylene succinate) (PBS) and geraniol essential oil blend. Inhibition clear zone test results showed that a suitable geraniol concentration, encapsulated in PBS, was 10 wt%. Based on the water vapor transmission test, coating paper with EVOH for three times (around 450 μm) was an optimal condition for the use as a controlled release part. Release test indicated that geraniol migration concentration increased with increasing the relative humidity (RH) in the package which correlated to the moisture liberated from bread slice. Shelf-life extension study informed that the spoilage of bread stored with antimicrobial sachet was delayed by more than three weeks. In summary, this antimicrobial sachet could be used in food shelf-life extension purpose which easily placed in any food container. This is an alternative way of food waste minimization.

Influence of the Graphene Filler Nature on the Morphology and Properties of Melt Blended EVOH Based Nanocomposites

In this study, ethylene vinyl alcohol (EVOH) nanocomposites elaborated by melt blending with four different fillers were investigated. Two graphene and two graphite fillers displaying various shapes were selected. The morphology, microstructure, thermal, mechanical, and barrier properties of the nanocomposite films prepared for 2 wt% fillers were analyzed with the aim to establish structure–function properties relationships. The nanocomposites properties significantly depended on the nature of the incorporated filler. The nanocomposite film prepared with the expanded graphite filler exhibited the highest Young modulus value (E = 1430 MPa) and the best barrier properties. Indeed, barrier properties, rarely studied at high water activities, evidenced a significant improvement with a decrease of the water vapor permeability by a factor 1.8 and of the oxygen permeabilities by a factor close to 2, for a critical water activity higher than 0.95. An increase of the thermal stability was also evidenced for this nanocomposite. It was shown that for all studied nanocomposites, the properties could be related to the dispersion state of the fillers and the simultaneous increase of the crystallinity of the matrix. A specific equation was proposed to take into account these both parameters to accurately predict the nanocomposite barrier properties.

Comparative Analysis of Machine Learning Methods to Predict Growth of F. sporotrichioides and Production of T-2 and HT-2 Toxins in Treatments with Ethylene-Vinyl Alcohol Films Containing Pure Components of Essential Oils

The efficacy of ethylene-vinyl alcohol copolymer films (EVOH) incorporating the essential oil components cinnamaldehyde (CINHO), citral (CIT), isoeugenol (IEG), or linalool (LIN) to control growth rate (GR) and production of T-2 and HT-2 toxins by Fusarium sporotrichioides cultured on oat grains under different temperature (28, 20, and 15 °C) and water activity (a_w) (0.99 and 0.96) regimes was assayed. GR in controls/treatments usually increased with increasing temperature, regardless of a_w, but no significant differences concerning a_w were found. Toxin production decreased with increasing temperature. The effectiveness of films to control fungal GR and toxin production was as follows: EVOH-CIT > EVOH-CINHO > EVOH-IEG > EVOH-LIN. With few exceptions, effective doses of EVOH-CIT, EVOH-CINHO, and EVOH-IEG films to reduce/inhibit GR by 50%, 90%, and 100% (ED₅₀, ED₉₀, and ED₁₀₀) ranged from 515 to 3330 µg/culture in Petri dish (25 g oat grains) depending on film type, a_w, and temperature. ED₉₀ and ED₁₀₀ of EVOH-LIN were >3330 µg/fungal culture. The potential of several machine learning (ML) methods to predict F. sporotrichioides GR and T-2 and HT-2 toxin production under the assayed conditions was comparatively analyzed. XGBoost and random forest attained the best performance, support vector machine and neural network ranked third or fourth depending on the output, while multiple linear regression proved to be the worst.

Improvement of Barrier Properties of Biodegradable Polybutylene Succinate/Graphene Nanoplatelets Nanocomposites Prepared by Melt Process

Polybutylene Succinate (PBS)/Graphene nanoplatelets (GnP) nanocomposites over a range of GnP from 0 to 1.35 wt.%. were prepared by a melt process. A mixture of individual graphene nanosheets and aggregates was obtained by the addition of GnP in the PBS matrix. The presence of these fillers did not significantly modify the morphology, crystalline microstructure of the matrix or its thermal stability. However, a slight reinforcement effect of PBS was reported in the presence of GnP. The water sorption isotherm modelling with Guggenheim, Andersen and De Boer (GAB) equation and Zimm-Lundberg theory allowed a phenomenological analysis at the molecular scale. The presence of GnP did not modify the water sorption capacity of the PBS matrix. From a kinetic point of view, a decrease of the diffusion coefficient with the increasing GnP content was obtained and was attributed to a tortuosity effect. The influence of water activity was discussed over a range of 0.5 to 1 and 0 to 0.9 for water and dioxygen permeability. Improvement of the barrier properties by 38% and 35% for water and dioxygen permeability respectively were obtained.

Manufacturing of Food Packaging Based on Nanocellulose: Current Advances and Challenges

Nowadays, environmental pollution due to synthetic polymers represents one of the biggest worldwide challenges. As demonstrated in numerous scientific articles, plant-based nanocellulose (NC) is a biodegradable and nontoxic material whose mechanical, rheological, and gas barrier properties are competitive compared to those of oil-based plastics. However, the sensitivity of NC in humid ambient and lack of thermosealability have proven to be a major obstacle that hinders its breakthrough in various sectors including food packaging. In recent years, attempts have been made in order to provide a hydrophobic character to NC through chemical modifications. In addition, extensive works on nanocellulose applications in food packaging such as coating, layer-by-layer, casting, and electrospinning have been reported. Despite these enormous advances, it can easily be observed that packaging manufacturers have not yet shown a particular interest in terms of applicability and processability of the nanocellulose due to the lack of guidelines and guarantee on the success of their implementation. This review is useful for researchers and packaging manufacturers because it puts emphasis on recent works that have dealt with the nanocellulose applications and focuses on the best strategies to be adopted for swift and sustainable industrial manufacturing scale-up of high-performance bio-based/compostable packaging in replacement of the oil-based counterparts used today.

Antioxidant Packaging Films Based on Ethylene Vinyl Alcohol Copolymer (EVOH) and Caffeic Acid

The main objective of this research activity was to design and realize active films with tunable food functional properties. In detail, caffeic acid (CA), a polyphenol with high antioxidant effect, was used as active ingredient in poly (vinyl alcohol-co-ethylene) (EVOH) films at 5 wt.% and 15 wt.% and successfully realized by means of the solvent casting process. Optical, morphological, thermal and mechanical studies were considered to define the effect of the presence of the CA component on the structural properties of the matrix. In addition, moisture content and antioxidant activity were evaluated, to have clear information on the CA effect in terms of functional characteristics of realized food packaging systems. Results from tensile tests showed increased values for strength and deformation at break in EVOH_CA based films. Results from colorimetric and transparency analysis underlined that the presence of caffeic acid in EVOH copolymer induces some alterations, whereas the addition of the active ingredient determined a positive radical scavenging activity of the formulations, confirming the possibility of practically using these polymeric systems in the food packaging sector.

Chronic wound healing: A specific antibiofilm protein-asymmetric release system

Chronic infection is a major cause of delayed wound-healing. It is recognized to be associated with infectious bacterial communities called biofilms. Currently used conventional antibiotics alone often reveal themselves ineffective, since they do not specifically target the wound biofilm. Here, we report a new conceptual tool aimed at overcoming this drawback: an antibiofilm drug delivery system targeting the bacterial biofilm as a whole, by inhibiting its formation and/or disrupting it once it is formed. The system consists of a micro/nanostructured poly(butylene-succinate-co-adipate) (PBSA)-based asymmetric membrane (AM) with controlled porosity. By the incorporation of hydrophilic porogen agents, polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG), we were able to obtain AMs with high levels of porosity, exhibiting interconnections between pores. The PBSA-PEG membrane presented a dense upper layer with pores small enough to block bacteria penetration. Upon using such porogen agents, under dry and wet conditions, membrane's integrity and mechanical properties were maintained. Using bovine serum albumin (BSA) as a model protein, we demonstrated that protein loading and release from PBSA membranes were affected by the membrane structure (porosity) and the presence of residual porogen. Furthermore, the release curve profile consisted of a fast initial slope followed by a second slow phase approaching a plateau within 24 h. This can be highly beneficial for the promotion of wound healing. Cross-sectional confocal laser scanning microscopy (CLSM) images revealed a heterogeneous distribution of fluorescein isothiocyanate (FITC) labeled BSA throughout the entire membrane. PBSA membranes were loaded with dispersin B (DB), a specific antibiofilm matrix enzyme. Studies using a Staphylococcus epidermidis model, indicate significant efficiency in both inhibiting or dispersing preformed biofilm (up to 80 % eradication). The asymmetric PBSA membrane prepared with the PVP porogen (PBSA-PVP) displayed highest antibiofilm activity. Moreover, in vitro cytotoxicity assays using HaCaT and reconstructed human epidermis (RHE) models revealed that unloaded and DB-loaded PBSA-PVP membranes had excellent biocompatibility suitable for wound dressing applications.

Active Role of ZnO Nanorods in Thermomechanical and Barrier Performance of Poly(vinyl alcohol-co-ethylene) Formulations for Flexible Packaging

Poly(vinyl alcohol-co-ethylene) (EVOH) films containing zinc oxide nanorods (ZnO Nrods) at 0.1, 0.5, and 1 wt%, were realized by solvent casting. The effect of ZnO Nrods content on morphological, thermal, optical, mechanical, and oxygen permeability properties were analyzed. In addition, moisture content and accelerated-aging test studies were performed, with the intention to determine the influence of zinc oxide nanofillers on the functional characteristics of realized packaging systems. Tensile properties showed increased values for strength and deformation-at-break in EVOH-based formulations reinforced with 0.1 and 0.5 wt% of zinc oxide nanorods. Results from the colorimetric and transparency investigations underlined that the presence of ZnO Nrods in EVOH copolymer did not induce evident alterations. In addition, after the accelerated-aging test, the colorimetric test confirmed the possibility for these materials to be used in the packaging sector. This behavior was induced by the presence of zinc oxide nanofillers that act as a UV block that made them useful as an efficient absorber of UV radiation.

Bio- and Fossil-Based Polymeric Blends and Nanocomposites for Packaging: Structure⁻Property Relationship

In the present review, the possibilities for blending of commodities and bio-based and/or biodegradable polymers for packaging purposes has been considered, limiting the analysis to this class of materials without considering blends where both components have a bio-based composition or origin. The production of blends with synthetic polymeric materials is among the strategies to modulate the main characteristics of biodegradable polymeric materials, altering disintegrability rates and decreasing the final cost of different products. Special emphasis has been given to blends functional behavior in the frame of packaging application (compostability, gas/water/light barrier properties, migration, antioxidant performance). In addition, to better analyze the presence of nanosized ingredients on the overall behavior of a nanocomposite system composed of synthetic polymers, combined with biodegradable and/or bio-based plastics, the nature and effect of the inclusion of bio-based nanofillers has been investigated.

Electrospun Poly(ethylene-co-vinyl alcohol)/Graphene Nanoplatelets Composites of Interest in Intelligent Food Packaging Applications

Graphene nanoplatelets (GNPs) were synthetized from graphite powder and, thereafter, embedded in poly(ethylene-co-vinyl alcohol) (EVOH) fibers by electrospinning in the 0.1–2 wt.-% range. The morphological, chemical, and thermal characterization performed on the electrospun nanocomposite fibers mats revealed that the GNPs were efficiently dispersed and rolled along the EVOH fibrilar matrix up to contents of 0.5 wt.-%. Additionally, the dielectric behavior of the nanocomposite fibers was evaluated as a function of the frequency range and GNPs content. The obtained results indicated that their dielectric constant rapidly decreased with the frequency increase and only increased at low GNPs loadings while the nanocomposite fiber mats became electrically conductive, with the maximum at 0.5 wt.-% GNPs content. Finally, the electrospun mats were subjected to a thermal post-treatment and dark films with a high contact transparency were obtained, suggesting that the nanocomposites can be used either in a nonwoven fibers form or in a continuous film form. This study demonstrates the potential of electrospinning as a promising technology to produce GNPs-containing materials with high electrical conductivity that can be of potential interest in intelligent packaging applications as “smart” labels or tags.

Temperature dependent separation of immiscible polymer blend in a melted state

The density and the spectral fingerprint of a compounded blend or composite vary widely depending on the type of the components and their composition. However, the currently used polymer separation techniques, such as density-based and optical sorting systems are not suitable for recovering these materials fully due to the physical-chemical bonding between the components. The application of a novel separation principle creates the opportunity to enrich the blend fractions to neat, homogeneous zones in a melted state by utilising centrifugal force. In this study three different types of plastics: high density polyethylene, polystyrene and polyethylene terephthalate were deeply investigated in order to understand the separability of their blends as a function of rotation time and melt temperature. The results showed that the separation of polymer mixtures and blends depends strongly on the viscosity and bulk density at a given temperature, and the initial particle size also has a significant impact.