Material Combinations
Material Combinations Material Combinations or Laminating The demand for compostable bioplastics has grown steadily for ten years at an annual rate of between 20 and 30%. The market share, however, is still very modest, accounting for less than T0.1% of the total plastics market. An interesting level of growth is being seen within the packaging sector. This applies specifically to multilayer structures where different materials are combined. Each material contributes its specific advantages to the whole structure. Article contributed by S. Facco, E. Fanesi, R. Marangon, Novamont SpA., Novara, Italy Novamont’s main mission is to offer original solutions both from a technical and an environmental point of view, starting from renewable raw materials. Mater-Bi is a generation of established, yet continuously evolving, compostable polymers containing compostable polyesters, starch and other renewable resources, and which is able to significantly reduce the environmental impact in terms of energy consumption and green-house effect in specific applications. These polymers will perform the same as, or even better than, traditional plastics when in use and will completely biodegrade within a composting cycle. New sectors are growing in different industrial applications, driven by technical performances, such as in the case of extrusion coating/lamination. The first laminated structures were developed in Europe at the beginning of the 1990s, when films with a specific ‘soft touch’ were glue laminated onto cardboard in order to produce rigid office folders. These were the first attempts at combining two different compostable structures. Already at that time the main issue was to present new material combinations that were able to offer an alternative recycling option (composting). Of course the paper repulping process was always taken into consideration and thoroughly evaluated. Beside lamination onto rigid cardboard substrates, because of their very high Water Vapour Transmission Rate (WVTR) these films started to arouse interest amongst producers of hygiene products, such as diapers, overalls etc. Specific requirements were a soft, noiseless and highly breathable material. Water vapour transmission rates in the range of 1,000 g/m²/30µ/24h were considered quite interesting, specifically for diapers, where industry was struggling to find alternatives to the high percentage of superabsorbers used in the absorbent padding of the diaper. Highly breathable backing sheets were considered to be a solution in order to reduce the quantity of the superabsorbers mentioned above. However the materials were not performing as requested, especially considering the gauge of the film. Products used in the 1990s were based on gauges in the range of 20-24µm. Today there are applications in which a 10µm Mater 12 bioplastics MAGAZINE [03/09] Vol. 4
Material Combinations by Extrusion Coating New compostable film structures, offering completely new performance profiles in the food and non-food areas Bi is laminated onto cellulose and viscose non-woven substrates. The main applications may be found in bed linen, mattress covers and overalls as used in clean rooms (in this case it is not only the breathability which offers an added value, it is also its intrinsic antistatic property). Today various process technologies are available to combine layers of different substrates in order to obtain very specific and tailored properties. There are quite different film families available which offer very individual properties and, when combined, suddenly open up a completely new application profile. One of these processes is extrusion coating, which consists of extruding a thin web through a vertical flat die onto various substrates, such as paper, cellulose films, PLA, aluminium, nonwovens etc. Extrusion lamination is very similar to extrusion coating and requires the same equipment: in this case the molten polymer is used as an adhesive, in order to bind (‘glue’) two substrates together. Various tests are being carried out and are very close to becoming industrially viable. There are specific structures, where high barrier properties and specific processing performances (on FFS lines) have been achieved. Oxygen and water barrier properties achieved by combining various compostable film structures (such as Mater Bi with coated or surface treated cellulose film) have demonstrated not only that they offer similar food integrity to that offered by standard materials, but processing on FFS lines is significantly faster. such ‘sharp’ edged products as Müsli flakes. The reverseprinted external cellulose film, which has excellent optical properties, is combined with a high tenacity Mater Bi film in order to obtain packaging material which fully covers the mechanical, organoleptic and processing needs of such products. Still one of the unique combinations on the market, it is able to offer compostability under industrial conditions. Other laminated structures are under evaluation, targeting high barrier properties and still maintaining their compostability. There are several developments ongoing, which soon will be introduced onto the market. Mater Bi has demonstrated that it is perfectly compatible with other substrates, enhancing dramatically most of the properties and maintaining key properties such as repulpability. The latest developed technologies in extrusion coating and lamination have up to now demonstrated that this technology will broaden many application areas, particularly food packaging, in which the physical, chemical, mechanical and organoleptic protection are of the utmost importance. www.novamont.com Depending on the application, these converting techniques provide a very efficient and versatile way to build specific, tailor-made, multi-layer structures. One of the first industrial, multilayer compostable and certified products was introduced in the UK by a major Organic Müsli producer. A market leader in packaging, based in Dublin, was able to combine a Mater Bi polymer with a cellulose film, obtaining a structure which offers a suitable barrier property, excellent organoleptic properties and very high mechanical properties in terms of toughness and tear resistance - properties which are needed to pack bioplastics MAGAZINE [03/09] Vol. 4 13
