A review on polymer–layered silicate nanocomposites

The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene vinyl alcohol. At higher RH’s, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5–10 nm, although some larger aggregates were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure formed by the nanofibers resulted in superior oil barrier properties.

Oxygen and oil barrier properties of microfibrillated cellulose films and coatings

Cellulose nanocrystals are unique nanomaterials derived from the most abundant and almost inexhaustible natural polymer, cellulose. These nanomaterials have received significant interest due to their mechanical, optical, chemical, and rheological properties. Cellulose nanocrystals primarily obtained from naturally occurring cellulose fibers are biodegradable and renewable in nature and hence they serve as a sustainable and environmentally friendly material for most applications. These nanocrystals are basically hydrophilic in nature; however, they can be surface functionalized to meet various challenging requirements, such as the development of high-performance nanocomposites, using hydrophobic polymer matrices. Considering the ever-increasing interdisciplinary research being carried out on cellulose nanocrystals, this review aims to collate the knowledge available about the sources, chemical structure, and physical and chemical isolation procedures, as well as describes the mechanical, optical, and rheological properties, of cellulose nanocrystals. Innovative applications in diverse fields such as biomedical engineering, material sciences, electronics, catalysis, etc, wherein these cellulose nanocrystals can be used, are highlighted.

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Cellulose nanocrystals: synthesis, functional properties, and applications.

Flexible barrier films preventing permeation of gases and moistures are important for many industries ranging from food to medical and from chemical to electronic. From this perspective, graphene has recently attracted particular interest because its defect-free monolayers are impermeable to all atoms and molecules. However, it has been proved to be challenging to develop large-area defectless graphene films suitable for industrial use. Here we report barrier properties of multilayer graphitic films made by gentle chemical reduction of graphene oxide laminates with hydroiodic and ascorbic acids. They are found to be highly impermeable to all gases, liquids and aggressive chemicals including, for example, hydrofluoric acid. The exceptional barrier properties are attributed to a high degree of graphitization of the laminates and little structural damage during reduction. This work indicates a close prospect of graphene-based flexible and inert barriers and protective coatings, which can be of interest for numerous applications.

/pdf/impermeable-barrier-films-and-protective-coatings-based-on-2hogy7rzj0.pdf

Impermeable barrier films and protective coatings based on reduced graphene oxide

In modern society, polymer packaging plays a critical role in the preservation and distribution of perishable goods such as food and prescription medicines. [ 1 , 2 ] Since the effectiveness of poly mer packaging materials in preventing product degradation is directly dependent upon their impermeability to degradative gases [ 3 ] and their opacity to high-energy light, [ 4 ] signifi cant efforts have been devoted to improving these properties. [ 5 ]

Crumpled graphene nanosheets as highly effective barrier property enhancers.

The barrier solutions presently available on the market all have their drawbacks, e.g. cost, water-sensitivity, opacity or perceived environmental bad-will. At the same time there is a trend to use more plastic-based packaging materials for different applications, e.g. as replacements for metal and glass containers. This situation has stimulated the industry to provide new, more efficient barrier solutions. The innovations go along five major lines: (a) thin, transparent vacuum-deposited coatings; (b) new barrier polymers as discrete layers; (c) blends of barrier polymers and standard polymers; (d) organic barrier coatings; and (e) nanocomposite materials. This paper provides a comprehensive review of the different approaches, outlining the principle behind each barrier technology, its performance, its potential and the companies developing and producing the materials. Copyright © 2003 John Wiley & Sons, Ltd.

Recent innovations in barrier technologies for plastic packaging—a review

Nanotechnology has been considered to have high potential for food packaging applications very early on The ability to provide additional consumer benefits through the improvement of key properties of packaging materials and the creation of new functionalities means that the increased use of nanomaterials and nanotechnologies is highly likely It has however up to now failed to reach the widespread use that was initially expected, mainly because of remaining uncertainties on the safety of these materials during the various stages of their life-cycle, which limit legal and consumer acceptance

This paper aims at presenting the latest developments in the field of nanotechnologies for food packaging applications, describing the legal framework linked to their usage and attempts to clarify the current knowledge of the safety of these materials both for the consumer and the environment

It is shown that particulate migration into foodstuff is absent in many applications, which drastically reduces the potential risk during the use phase of packaging materials, ie the exposure of the consumer to nanoparticles Other release routes are also evaluated, showing that, although safe in normal use conditions, prudence should still be used, especially with regard to release after disposal of the materials Copyright © 2016 The Authors Packaging Technology and Science Published by John Wiley & Sons Ltd

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pts.2221

Outlook and Challenges of Nanotechnologies for Food Packaging

Three different techniques for experimentally determining the bending stiffness of flexible films and laminates have been evaluated using a number of different packaging materials. The results showed that a cantilever test was the best, giving reliable data for all kinds of films and laminates. A three-point bending test proved to be sensitive to misalignment, whereas a bending-under-own-weight test was incapable of handling curled samples and generally gave lower stiffness values. A model for predicting the bending stiffness of multilayer laminates from the elastic modulus of the constituents was developed and used to examine the influence of layer position and composition on the overall bending stiffness. Model calculations showed that thin layers, such as adhesives, print and barrier coatings, can have a large influence on the bending stiffness and that the influence often goes against what would be intuitively expected. The calculations also showed that layer modulus often is less important than layer thickness and that the position of the layer in the laminate can have a major influence on the overall stiffness. Copyright © 2001 John Wiley & Sons, Ltd.

Predicting and determining the bending stiffness of thin films and laminates

Since the early days of the specialty coffee movement, freshness has been one of its central pillars. Freshness is best defined as having original unimpaired qualities. In coffee, it is most often seen as freshly roasted, ground within a few days, immediately extracted, and consumed. But despite this pivotal role of freshness for high quality coffee, the objective and scientific measurement of freshness have often been vague and elusive. How can one measure the level of freshness of coffee? In this chapter we will outline two approaches. One is based on the degassing of the freshly roasted coffee and the other on the evolution of its aroma profile during storage. In terms of the evolution of the aroma profile, we will introduce one particular freshness index: the ratio of dimethyl disulfide to methanethiol, suited to assess the evolution of freshness of roasted coffee during storage. Although this ratio has been shown to increase during storage, the speed at which this freshness index increases depends on the packaging and storage temperature. This has opened the possibility to use this index to assess the freshness of roasted coffee and compare the quality of different packaging materials for preserving the freshness of the coffee inside.

Protecting the flavors : freshness as a key to quality

For paper-based dry pet food packaging, one of the main requirements is a high resistance against staining from the fat in the product. For both development and quality control, rapid and reliable standardized test procedures assessing this property are needed. Although a number of tests are available, they either apply only to certain types of packaging materials and show limited correlation with field behaviour, or employ non-standard testing substances, long testing times and complicated equipment. In response to this situation, a new testing procedure that reflects field behaviour but without the drawbacks of the existing tests has been developed. The new test shows high reproducibility and good correlation with field performance for a wide range of multiwall bag and folding box materials with different types of grease resistance treatment. Copyright © 2002 John Wiley & Sons, Ltd.

Yves Wyser

Papers

Recent innovations in barrier technologies for plastic packaging—a review

Outlook and Challenges of Nanotechnologies for Food Packaging

Predicting and determining the bending stiffness of thin films and laminates

Protecting the flavors : freshness as a key to quality

Novel method for testing the grease resistance of pet food packaging

Yves Wyser

Papers

Recent innovations in barrier technologies for plastic packaging—a review

Outlook and Challenges of Nanotechnologies for Food Packaging

Predicting and determining the bending stiffness of thin films and laminates

Protecting the flavors : freshness as a key to quality

Novel method for testing the grease ­resistance of pet food packaging

Novel method for testing the grease resistance of pet food packaging