Today new packaging development has been emerging in the market and a big chunk of this new market trend goes to multilayer barrier films. It has been proven that increasing the number of layers is among the most significant factor that affects mechanical properties of film, in addition improved barrier properties, better physical properties, and the ability to manufacture many different film structures, especially when comes to
barrier film products.
Flexible packaging converters are always looking for innovations, to create new structures to increase the shelf life of foodstuffs, improve the appearance of products and provide new substances for use in packaging. They are working to develop ways to enhance packing efficiency and the possibility of reducing the thickness of film without sacrificing the quality.
The current advancement in nano-layer offers flexibility in the film structure and leads to a greater choice for products in terms of mechanical propriety, optical properties and quality.
Latest nano-layer technology was a result of development in layer-sequence repeating technology, which has provided new market niches for heavy-duty film using for form-fill-seal applications as well as shrinkable barrier film.
Thanks to moves in nano-layer technology related to the modular disk die, Alpha Marathon has expanded its collaboration with BBS Corporation and developed high-output blown film systems for these applications, using its proprietary Alpha Plus Double Bubble technology.
Today's rapidly developing market for shrinkable barrier film, involving the design and fabrication of ultra-thin and highly constrained barrier polymer layers, drives the need for a fundamental understanding of micro- and nano-layer technology.
The double bubble process is done in two stages. First, the extruded tube is quenched and rapidly cooled and nipped in the water bath; then the tube passes through an IR (infra-red) oven for reheating and stretch prior to re-blowing of the second bubble. This is a much colder biaxial stretching that results in a higher shrink force as well as films with higher tensile strength.
In this technology, water rapidly has an effect on the film structure by quickly cooling the film and creates a more amorphous structure that improves the mechanical and optical qualities of the film.
The results of ongoing research and development with double bubble film shows that nano-layers increase orientation ratios from five up to seven times in biaxial directions. This means that thinner but tougher shrink films are made with higher tear resistance and higher tensile strength compared to a conventional three-layer bi-oriented shrink film.
Because the layer-sequence repeater has many tiny slots to alternate, the pressure inside layers is very relaxed, and due to being parallel against metal surfaces have very slow flow. Thus the flowing melts have better alignment but less molten orientation compared with normal layers. This means significantly more polymer is available for stretching.
In die technology for the production of micro and nano-layers, the layer-sequence repeater is created by simply building a melting sequence in general using two different materials.
Separate cell modules allow micro-layers of an arbitrary number of materials, as many as 12, in any desired position, in general up to 25 layers. This is done by controlling the relative thicknesses of the structural layers by extrusion rate.
Each section of nano-layer consists of 25 layers, replacing two melts. This number could be made more or less when the layersequence repeater is assembled. With 25 being an odd number means that one of the materials will always be the outer layer of any layer combination. In addition, this provides for a lower pressure requirement and minimising overall use of each of the two materials. In addition, this provides for a lower pressure, insures adequate back pressure for overall delivery rate of each of the two materials
In case of using Ethylene vinyl alcohol (EVOH) for multilayer barrier film, highly crystalline layers are brittle and usually stress cracking could be seen, resulting in loss of barrier performance in the product shelf life.
Nano-layers of EVOH, which is coextruded by PA6/66, typically result in lower crystallinity near the interface. This will improve flex-crack resistance and therefore maintain barrier properties in the product life-cycle.
In Combination, nano-layer technology with double bubble technology reduces the capital and facility costs to establish production, reduce operating costs and significantly increase production output. Consequent improvements in the physical properties enable a reduction in the film thickness without compromising packaging performance, resulting in lower resin input cost per package, further improving profitability with the added benefit of lower shipping costs per unit Products of the double bubble blown film line are widely used for packaging fresh meat. Shrink film/bags are convenient since standard sized bags adapt themselves to the individual sizes of each portion. They provide clarity and enhance the appearance of the packaged meat. They are tamper evident and maintain product quality.
Alpha Marathon's offers double bubble lines with co-extrusion or nano-layer which produce highest quality shrink barrier films for superior packaging needs.
1- Nano-layer – Micro-layer Structural Advances in Shrink Films, Henry G. Schirmer, BBS Corporation, Spartanburg, SC, USA
Jean-Francois Glez, Bollore, Quimper, France - Dr. Mark Pucci, Soarus LLC, Arlington Heights, IL, USA
2- H.Wang, Confine Crystallazation, Crystalline phase deformation and their effects on the properities of
Crystalline Polymer – PHD. Thesis – Case Western Reserve University - 2009
written by Matt Tabassi M.Eng.