The modern era is all about the technology, especially nanotechnology have given tremendous opportunities to the researchers and technologists to the developments of innovative materials in various fields, especially in Polymers and Composites area. This yields momentous developments in the field of agricultural food. Particularly in the case of food packaging area, where tremendous advances in ‘Nano-reinforcement’ of bio-based polymers provided a solid base towards enhance the economic and technical support of renewable bio-polymers, for the developments of different bio-based polymer applications. From the last decades, the use of plastics in various sectors has been significantly increased, especially in the food packaging area. In fact, now days, the plastics packaging is a one of the largest applications among others in polymer field, and within this range, the food packaging concerns, as largest plastics application. This is because plastics bring enormous properties, and advantages like, flexibility, thermosealability, lightness, and the low coast.
The study of fabrication, synthesis, production, characterization, and application of materials, systems, and devices controlling the shape and size of the Nano scale termed Nanotechnology, where Nano scale considered covering the range of 1-100 nm. Nanotechnology is a field where things are measured in a nanometer, where nanometer is (10-9) the one billionth of a meter or about a thousand times smaller than a red blood cell, or about half the size of the diameter of DNA, or the one hundred thousand times smaller than the diameter of a human hair.
Nanotechnology also defined as the exploitation of structures with at least one dimension of the nanometer size for the construction of new materials, systems, and devices with different and significantly improved properties due to their Nano-size structured. This technique can top be described as activities at the atomic and molecular level of that have the applications which can be applicable. The products which are made up as the resulting efforts of Nanotechnology are called Nanomaterial’s, consisting of nanoparticles, where nanoparticles defined as: a particle having diameter less than 100 nanometers. Scientifically, nanotechnology is engaged to describe materials, devices and systems with structures and components presenting new and expressively improved biological, physical and chemical properties at Nano scale.
These changes in properties are due to increase in the surface area and dominance of quantum effects, which is linked with the large surface area to volume ratio, and very small sizes. For example, copper is opaque at macro scale but, at Nano scale it becomes transparent. Platinum become catalyst at Nano scale instead of inert at normal. Stable aluminium is combustible, while at Nano scale insulator, silicon, becomes a conductor. Material’s magnetic, thermal, optical and electrical properties determined at Nano scale by the quantum effect. It is predictable, that the cost of the material will be cheaper at Nano scale due to the less quantity consumed of a material.
Role of Nanotechnology in nature
There are a lot of evidences of nanotechnology in nature, based upon its ability to work at the atomic and molecular levels. Mainly the mechanism of the physical and biological world operates at the range of 1 – 100 nm. A molecule, for example water molecule may be made up of 20 to 30 atoms and its diameter is about 1 nm, Hydrogen’s atom diameter is about 0.1 nm, DNA’s molecule width is about 2.5 nm, and Protein is between 1 – 20 nm, the thickness of human hair is about 10,000 nm.
Nanotechnology for Packaging applications
Nanotechnology is a creation and successively utilization of Nano-structures which creates the novel properties, that cannot be displayed by bulk materials or isolated molecules. Since, the researchers from ‘Toyota’ in 1980’s predicts the thermal, mechanical, and barrier properties of nylon-nanoclay, the properties of composite dramatically improved by the reinforcing with a smaller amount, less than (5%) of nanoclay, there was wide-ranging research had been performed, in the field of nano-composites, especially in the food packaging area.
Nano-composite refers to the composite material, which contains low additions of nanoparticles. In food bio-packaging area, nano-composites refers, the material containing, 1-7 (wt. %), of nanoclays. For the purpose of reinforcement, the highly appreciable interaction between the matrix and filler is required. The observation from the research is that, the interaction between the matrix and the filler is significantly improved, when reduced size reinforcing agent is properly dispersed in material. Therefore, transforming from micro to nano sized particles embedded into polymeric matrices, large surface area to volume ratio, and very small sizes of nanoscale structures yields, improved properties and performance of composite materials.
In the field of Bioplastics nanotechnology, the nano-composites have taken more attention, in that, nanoclay nano-composites are on top interest. It has been reported by various researches, that the embedment of nano-layered particles, i.e. nanoclays, to Bioplastics can affect the material properties, such as thermal stability, mechanical behavior, Ultraviolet visible protection, processability, gas barrier, vapor barrier, and conductivity.
Moreover, the issues which are associated to Bioplastics, i.e. non-intended migration can be reduced by use of nanoclays of plastics components to the foods, and, recently development in nanoclays study offers the great advantages, in formulation of the active packaging techniques which based on the Bioplastics, such as, oxygen scavenging, more effective antioxidant, antimicrobial bio-packaging, these increases the safety, and quality of packaged foods, the performance of Bio-polyesters in standings of oxygen barrier, is improved, by addition of nanoclays, but food contact complying.
Nanoclay — enhanced matrix
Nanoclay Bioplastic composites have been produced, in which use of the Nanoclay, as reinforcement agent for the polymeric matrix. This addition of nanoclay enhances the stiffness of resin. The major benefit of this addition is that, to provide the strength to the composite, which may reduce as the result of the influence in shear modulus of polymeric matrix. Figure shows the compressive strength of the S2 (GF) glass fiber, (Vf = 35%), which reinforced, the resin of ‘vinyl ester’ by addition of the particles of nanoclay.
In the field of Bioplastics, Laminar clays nano-composites play a vital role for the development of better properties of composite, especially for the packaging industry, there are also other nano-composites which are essential to this field, i.e. carbon nanotubes (CNT), and the nanoparticles of different metals oxides. There are also some other reinforcing agents, i.e. the nanostructures, which are obtained by the electro-spinning, and the ‘cellulose nano-whiskers’ biodegradable (CNW), these nano-fillers are promising nanoparticles in many applications.
Another advantage to use of biopolymer nano-fillers is to reinforcement of Bioplastics this yields the value of generating the fully bio-based formulations of the composite. These nano-bio-fillers or particles, like electro-spinning nanoparticles and cellulose nano-whiskers (CNW) have large surface to volume ratios, meanwhile to 103 greater than the micro-fiber, this property large surface to volume ratios gives good flexibility, outstanding mechanical strength, edibility, and lightness. Other advantages of embedment of nano-fillers in Bioplastics are the controlled release of the bioactive and other active compounds in the applications of food packaging, and for nano-encapsulation of the food additives in the packaging materials.
Challenges and strategies
In the Bioplastics field the two main challenges are associated with functionality, specifically generating reproducible performance of Bioplastics as petroleum-based counterparts, and achieving truly positive life-cycle analysis, i.e. achieving the goal of carbon neutral materials or minimizing fossil energy consumption. Regarding nanoparticles, it is reckoned that to achieve the level of performance associated to the use of nanotechnology, high dispersion should be achieved in the Bioplastics matrix. Hence, nanoparticles dispersion still remains a challenge for the full delivery of the expected properties as announced by the early modeling work.
There are several technologies to achieve Nano-dispersion in bio-packaging materials being the most common, in situ polymerization, dispersion in solution and dispersion via melt-blending. Despite the two formers being more efficient in achieving Nano-dispersion in most cases, the latter route, less efficient in achieving dispersion, is without doubt the most demanded technology from an applied viewpoint, because it makes use of industry available machinery and processes to convert plastics into final articles. Other emerging processing routes to achieve Nano-dispersion are ball milling, multiple Nano-layer extrusion and vapor deposition Nano-coatings.
A chemical and/or physical modification is needed to both compatibilist highly hydrophilic clays with the more organic polar chemical constitution of most thermoplastic bio-polyesters and to increase the clay inter-gallery space (basal space between adjacent layers), hence facilitating both intercalation and exfoliation, i.e. Nano-dispersion, of the clay laminar components in the matrix during compounding. In the food chain, special caution is needed because the modifications should comply with the stringent migration regulations, i.e. functional barrier status, and preferably make use of food-contact approved substances as valid modifiers. Currently, many of the existing Nano-additives, such as those modified with some ammonium salts which are commercially available.
There is a lack of knowledge about the impact of Nanomaterial’s when inserted into Bioplastics during service. For instance, very little is known about their stability during processing and potential toxicity issues related to decomposition and/or migration and also as to how they will affect the actual inherent Bioplastics migration levels and the current establishment of afterlife disposal channels such as incineration, composting or recycling. However, and regarding this issue, the prospects for natural additives such as food-contact complying nanoclays, essentially microparticles, and nanobiofibers due to edibility and/or resorbability or biocompatibility may not be of so much concern in biopackaging.
For instance, regarding the afterlife disposal, it has found that nanoclays in biodegradable matrices do not delay biodegradation during composting, since it is a process that occurs from the outside towards the inside and that the nanoclays, due to their inherent high surface energy, re-attach to each other to become microparticles of soil once the polymer matrix disappears Regarding inherent nanoparticle hazard assessment, due to their small size, nanoparticles are generally much more reactive than their corresponding macro-counterparts. But it is also true that as a result of this, much smaller filler loadings are typically required, and hence added to the matrix, to achieve the desired properties.
The large surface area of nanoparticles allows a greater contact with cellular membranes, as well as greater capacity for absorption and migration. Therefore, assessment of the effects of nanoparticles in food packaging materials such as migration to foods, and potential bioaccumulation needs to be considered in the expected dosages.