Nanotechnology contributes to the ultra-high barrier properties of Tera-Barrier’s novel “micro-pore-plugging” film that also provides transparency and stretchability for applications in food, medical and other packaging markets
The hot button of nanotechnology is advancing in a number of innovations across the manufacturing spectrum in markets including packaging. An interesting example of the latter is that of Tera-Barrier film, which claims to offer moisture barrier performance 10 times better than transparent oxide barrier films that have been used in food and medical packaging applications.
Senthil Ramadas, director and chief technology officer, Tera-Barrier Films Pte, Ltd. (TBF), Singapore, answers our packaging-related questions about the new Tera-Barrier film, which has several patents associated with it.
What kind of a breakthrough does this represent?
Ramadas: The breakthrough in our research is a protective film that creates the highest barrier performance against moisture and oxygen permeation.
Conventional plastic films—even when coated with a metal oxide (such as aluminum oxide, silicon oxide or silicon nitride) to improve their barrier properties—are inadequate due to well-known imperfections such as pinholes, cracks and grain boundaries that mar their performance. We developed an innovative approach to resolving the “pore effect” by literally plugging the defects (at the nano scale) in barrier oxide films using reactive and non-reactive nanoparticles. The nanoparticles used in the barrier film have a dual function: They not only seal the defects, but also actively react with and retain moisture and oxygen.
In the course of the development, we could successfully encapsulate each nanoparticle with a different material including polymers and oligomers. These encapsulated nanoparticle layer or films can be used in a multilayer barrier stack that can provide different functional properties, such as sealing the defects and enhancing barrier, anti-reflection and ultraviolet (UV) filter properties when appropriate nanoparticles and encapsulation materials are selected.
We have successfully scaled up this technology and demonstrated barrier properties of 0.0001 g/meter2/day to 0.000001 g/m2/day at 39 deg C and 90% relative humidity (RH).
Tera-Barrier’s barrier films have met all the requirements with independently validated specifications for barrier performance, flexibility and transparency using a cost effective production technique. Major corporate investors have demonstrated their confidence in the technology with an investment in Series A and B funding rounds.
How did this development come about?
Ramadas: Flexible barrier packaging films are extensively used in packaging of various types of food, medical and electronics applications. These films should be of high quality in terms of barrier properties to ensure preservation of aroma and also extend the shelf life of the food. At the same time, the films should be manufactured at low cost.
Another critical issue in food, medical and electronics packaging is that of migration and permeability of oxygen or water vapor. No packaging material, such as plastic film or barrier coated plastic film, is completely impermeable to atmospheric gasses.
Aluminum foil has been the industries chosen structure for decades, as it has excellent high barrier and provides extended shelf life as compared to transparent oxide films and metallized films. Foil is an energy-intensive manufacturing process. Therefore it is higher in cost than transparent oxide films.
In addition, aluminum foil is losing out to barrier-coated films because it is not transparent, and cannot be used in packaging that has to undergo metal detection or radio-frequency identification (RFID) integration.
Plus, these foils are non-stretchable.
Multilayered barrier laminates is another approach to enhance the moisture barrier properties [measured in the water vapor transmission rate or WVTR] up to 0.05g/m2/day. Examples of multilayer packaging materials are PET/aluminum foil/polyamide/polyethylene and PET/aluminum foil/PE. Non-aluminum foil multilayer laminates have not shown significant performance as compared to transparent oxide-coated barrier plastics.
Metallized aluminum and transparent oxide-coated plastics are widely used as moisture and oxygen barrier films. Inorganic films (such as aluminum, Al2Ox, SiOx and SiN) produced by puttered processes or Atomic Layer Deposition (ALD) may be a good alternate to aluminum foil, but they are generally not cost effective and have low production throughput.
However, low-cost inorganic thin films (aluminum, Al2Ox and SiOx) used in food packaging and medical packaging produced by high throughput vapor deposition processes have only achieved WVTR properties of 1g to 0.5g /m2/day at 38 deg C and 90% RH conditions. It is one order in magnitude lower than aluminum foil barrier properties.
The global consumption of transparent barrier films using inorganic barrier coatings are forecast to grow during the period of next four years at an annual rate of 8.2%, which is almost double the rate of the transparent barrier films market as a whole. Inorganic barrier coatings are applied almost exclusively to food packaging, such as retort and microwavable packaging, lidding for meat packs, dry foods and stand-up pouches. However, the limitations of transparent barrier films are its lower oxygen and moisture barrier properties (WVTR and OTR) and its non-stretchability.
How does your technology work?
Ramadas: The encapsulated nanoparticles layer consists of nanoparticles, 700nm in size, which are encapsulated by organic species by a self-assembly method in which the nanoparticle concentration is high, up to 70% to 80% by weight. Therefore, the encapsulated nanoparticle layer has high packing density and has strong bonding between the particles and the substrate due to the encapsulated organic material. The ratio of nanoparticles to organic species is critical for the desired transmittance properties. In this concept, the focus is to reduce the amount or thickness of organic species to the minimum thickness as low as a few nanometers and the encapsulation may be partial or complete.
The encapsulated nanoparticle layer coating onto the polymer substrate enhances the barrier properties by two means. Firstly, the high packing density of nanoparticles is creating a long tortuous path for moisture and oxygen diffusion. The result is a longer mean path for gas diffusion through the encapsulation material. Secondly, nanoparticles could actively react with oxygen and moisture since nanoparticles increase the surface area. Therefore, the overall permeation through the encapsulated nanoparticle layer is minimized.
The present concept provides a barrier layer (encapsulated nanoparticle layer), which is completely, or at least substantially, devoid of a polymer matrix. The polymer may become porous, thereby leading to a pathway for oxygen and moisture and reducing the lifetime of the devices or food substances. Thus, by reducing or eliminating the polymers in encapsulated nanoparticle layers, a higher barrier performance is achieved.
What market needs does it address?
Ramadas: Our films could provide lower WVTR properties comparable to aluminum, and good light transmittance and stretchability up to 5% to 10%. If required, we can tune the nanoparticle to act as a UV filter.
What are the alternatives and why is this better?
Ramadas: Aluminum has very low moisture vapor transmission rate (MVTR) and oxygen transmission rate (OTR) properties, but it is higher cost, opaque, non-stretchable, interferes with metal detection inside a package and it is difficult to integrate into RFID devices.
Inorganic oxide barrier coatings are cost effective and transparent, but have inferior MVTR and OTR properties as compared to aluminum foil. It is also non-stretchable.
TBF’s encapsulated nanoparticle layer provides higher gas barrier properties as compared to inorganic oxide barrier films and is an excellent alternate to aluminum foil. TBF strategy is to bridge the gap between aluminum foil and transparent oxide films to create new packaging structures for niche applications in food, medical, pharmaceuticals and electronics market.
Are there any special methods needed to convert nanomaterials?
Ramadas: No special precautions or equipment/modifications are required. Commercially available equipment used for food packaging/medical packaging can be used.
Also, there is no problem in storage or handling or machinability from any conventional films.
How would you respond to concerns over nanomaterials?
Ramadas: We are using nanomaterials that have already been used in consumer applications. Therefore, we do not have concerns.
What is the commercial status and interest?
Ramadas: We received more than 400 inquiries after a January 2014 press release for food, medical and electronics applications and for a number of unique applications as well.
We are in pilot scale production. We can provide roll sample with 300-mm wide for validation purposes only. We are expecting to set up manufacturing plant in mid-2015; commercial products will be available only in end 2015.
Also, TBF has an agreement with KISCO (Asia), a subsidiary of Japanese parent company KISCO Ltd. (www.kisco-net.com/english), to commercialize and distribute the barrier films in the Asia Pacific region.
Tera-Barrier Films Pte Ltd. +65 6592 0574
Senthil Ramadas can be reached by email at [email protected].
Note: The company website, www.tera-barrier.com, is under construction.