Material Combinations
Material Combinations Bioplastic Material Combinations for Flexible Packaging Flexible plastic films have a long history of high performance in packaging applications and are well established at the forefront of waste reduction. Conventional plastics naturally tend to offer a high barrier to moisture, therefore allowing dry foods to remain dry and wet products to maintain moisture, for a long period of time. Compostable bioplastics however, tend to have a natural permeability to moisture. This makes them a perfect fit for applications such as fresh, short shelf-life products, but less suited to long shelf-life dry foods or liquid packaging. If bioplastic films are to break out from operating only in short shelf-life applications, then solutions need to be found to provide a higher barrier to moisture, without compromising compostability. But this situation is changing as (a) manufacturers develop new higher-barrier products, and (b) as innovative flexible packaging converters start to ‘mix and match’ properties by laminating different biomaterials. Whilst liquid packaging may still be a future dream for bioplastics, dry foods are starting to be successfully packaged now. Given that conventional flexible plastics use small amounts of material to provide excellent shelf-life and therefore lead to a significant reduction in overall waste, one might be tempted to think that biomaterials are not able to offer much potential in this arena. Far from it, for it is at the end-oflife stage when biomaterials potentially come into their own, in a flexible packaging context. Flexible packaging is indeed great for minimising resource use and weight, and brings further benefits in terms of transportation and point-of-sale presentation. However flexible packaging materials are intrinsically very difficult to recycle (mixed and incompatible materials, lightweight and impractical to collect). As a result, incineration, where available and where desired, is the only practical solution for dealing with conventional flexible packaging waste. Whilst bioplastics too are perfectly suited to incineration, they also open up new opportunities such as composting (industrially or at home) and Anaerobic Digestion (AD). AD in particular is starting to excite Government and waste management industries in a number of countries. There are three key benefits to disposing of packaging (including biowaste bags) via AD: I. It can help direct food and horticultural waste away from landfill (where this can create fugitive greenhouse gas emissions) II. It can contribute towards renewable gas generation techniques for energy supply and III. The residual digestate can also replace fossil and mineralbased fertilisers for soil improvement. The key to developing bioplastic solutions for mainstream flexible packaging applications is coming from a combination of innovative bioplastic research and from ‘copying’ (or rather mimicking) the approaches already used by the conventional packaging industry. What consumers do not realise is that a huge proportion of the ‘bit of plastic’ they find around their packaged foods is actually much more technical than they would ever imagine; laminates of different materials, surface coatings, adhesive systems, etc. Let us take one such example: When a consumer buys a bag of ‘fresh ground coffee’ it will actually have been roasted, ground and packed days or even weeks before into a highly developed laminate structure that typically comprises: • A transparent Polyester (PET) film, which is reverse-printed (i.e. printed on the inside, for protection and actually viewed 18 bioplastics MAGAZINE [02/10] Vol. 5
Material Combinations Article contributed by Andy Sweetman Business Development & Sustainability Manager Innovia Films Wigton, Cumbria, UK through the film.) PET is used because high temperatures are needed to seal through the pack and PET offers excellent heat-resistance • A thin layer of adhesive • A thin aluminium foil layer (or Metallised PET), to provide exceptional barrier • Another thin layer of adhesive • A thick Polyethylene (PE) film which is used to provide strong and leak-resistant heatseal properties and also adds further body and resistance to the pack In addition, whilst this type of technical construction is also used in a range of other packaged food applications, in the case of coffee bags, there is also generally a very small valve device incorporated (often almost invisibly) into the structure, to vent-off gases generated by the coffee after roasting. So there we have it; minimum resources, Yes, but maximum difficulty when it comes to dealing with the wrappers after use… However if we could mimic these constructions, but replace the conventional polymers with biopolymers, we could develop solutions that would run on the same conversion and packaging machinery, but which also open up the wider range of end-of-life scenarios we mentioned earlier. So let us imagine our coffee pack ‘turning Bio’…. • The outside PET film can be replaced by a transparent NatureFlex, printed in exactly the same way but with biocompatible inks, providing barrier and heat-resistance properties • Adhesive manufacturers have been working on bioadhesives and the first examples are hitting the market now • The aluminium foil can be replaced by a metallised NatureFlex, providing excellent barrier to moisture and gases • Another bioadhesive • Then finally the PE film on the inside can be replaced by a film manufactured by one of the high seal strength and high renacity materials such as starch based or co-polyester based materials (e.g. Mater-Bi, Ecoflex etc). Additional technologies such as extrusion coating (directly applying molten polymer to heat resistant films or papers) and alternative polymers (PBS, PHAs, PHB, PLA) can also provide building blocks to help the industry further develop such technical solutions. To be truly innovative, the level of communication between co-suppliers of biopolymers has had to increase, not only for each other to appreciate the technical benefits of each polymer, but also to fully understand the end-of-life options that are possible for hybrid materials and how they should be positioned in the market. This role has been partly facilitated by organisations such as European Bioplastics and other similar associations worldwide. Co-operation continues between producers in the bioplastics supply chain and partnerships are constantly emerging to take industry developments to the next level by offering new innovations in packaging. Innovia Films will be announcing several such innovative packaging solutions during this year, which will ensure that sustainable packaging options, using bioplastics, can finally start to offer similar functionality as conventional plastics. www.innoviafilms.com bioplastics MAGAZINE [02/10] Vol. 5 19
