Films | Flexibles | Bags
Films | Flexibles | Bags Compostable New Performance Profiles Article contributed by Stefano Facco New Business Development Manager Novamont S.p.A. Novara, Italy The demand for compostable bioplastics has been steadily growing for many years at an annual rate of between 20 and 30%. The research related to these polymers derived from RRM (Renewable Raw Materials), which in the case of Novamont swallows up 10% of its turnover, today permits the production of a large range of consumer products. These include food and non-food packaging, hygiene products, bags and sacks, agricultural tools and food-service ware, all with a positive environmental impact (End of Life options) and a positive effect on product performance. An interesting growth rate has been noticed within the area of films and flexibles, especially multilayer structures. At the beginning of the 1990‘s Novamont had already started to understand that the use of compostable biopolymers would be taking a growing market share in the area of flexibles, as the following article will describe. The latest expansion of Novamont’s production capacity is also a demonstration of the steady growth of this market sector. Environmental Impact Novamont’s main mission is to offer original solutions both from the technical and environmental points of view, starting from renewable raw materials. Mater-Bi is a generation of established biodegradable and compostable polymers, continuously evolving, containing compostable polyesters (based on synthetic and renewable monomers), starch and other renewable resources. They are able to significantly reduce the environmental impact in terms of energy consumption and greenhouse effect in specific closed-loop applications (such as food packaging, catering items, mulch films, bags for kitchen use and garden waste, etc). They perform as traditional plastics when in use, and completely biodegrade within a composting cycle through the action of living organisms when they have been engineered to be biodegradable and compostable. The technology that stands behind these new materials has evolved over the years in various steps: the first based purely on the complexing of starch, and later the continuous improvement of the environmental profile of Novamont‘s polymers through the increased use of non-food renewable resources in various steps, the backwards integration into production of polyesters and their monomers from RRM’s. Today we find flexible industrial applications in the areas of waste bags and liners, shopping bags, loop handles, T-shirts, packaging based on single and multilayer films, either coextruded or laminated, and of course hygiene and agricultural applications. Various process technologies are available, for monolayer or multilayer structures. The latter variant is used in order to combine different substrates with each other and to obtain very specific and tailored properties. There are quite different film families available, which offer very specific properties (such as puncture resistance, oxygen barrier etc) and, when combined, suddenly open up a completely new application profile. Suitable new 20 bioplastics MAGAZINE [06/09] Vol. 4
Films | Flexibles | Bags Film Structures, for Food and Non-Food technologies, such as extrusion coating and lamination, are fast growing at a similar pace as that of the new multilayer (coex) films. Processing Processing is nowadays no longer subject to critical discussion, as in the early 90‘s. Today converting these materials may be carried out on standard extruders, such as LDPE film blowing lines (minimum thickness in the range of 10-12µm). Productivity, if the line is specifically designed for Mater-Bi, is similar to that obtained with conventional polyolefines. Other converting aspects, such as sealing and printing, are also comparable with standard materials. Recycling is done conventionally by most of the converters. Their properties are also very much comparable to those of standard polyolefines, except some very special properties in the area of OTR (oxygen transmission rate) and WVTR (water vapour transmission rate): MFR (g/10 min) 3.5 – 7 ASTM D 1338 E Modulus (MPa) 90 - 700 ASTM D 882 Stress at break (MPa) 22 – 36 ASTM D 882 Elongation at break (%) 250 – 600 ASTM D 882 COF 0.1 – 0.6 DIN 53375 A Haze (%) 26 - 90 ASTM D 1003 WVTR (g·30μm/m2·24h) 200 – 900 ASTM E 96; 38°C 90% RH OTR (cc·30μm)/(m2·24h·atm) 500 - 2000 ISO 15105-1; 23°C 50% RH Extrusion Coating and Lamination Newly developed applications are based on the extrusion coating and lamination processes. In this case special grades do offer the same processability as for given polymers on standard lines, offering excellent adhesion on most of the substrates (paper, cardboard, biopolymers, tissues etc), high line speed, web stability and low gauges. The main applications may be found either in the area of light flexible packaging, such as food wrapping, industrial bags and sacks, or in rigid packaging, such as the one based on heavy cardboard for containers, trays, deep freeze boxes and for foodservice ware such as cups and plates. The barrier to oils and fats is quite good, average WVTR is in the range of 250 g/m²·24h (23°C, 50% RH) Coextruded films also offer a good barrier against fats and oil (compared to polyolefines), with WVTR ranging from 300 – 800 g·30μm/m²·24h and OTR in the range of 700 – 2.000 cc·30μm/m²·24h (23°C, 50%RH). Special sealing layers are used, characterised by a ∆T above 50°C, which allow easy running on most of the packaging lines, whether they be VFFS (Vertical Form Fill Seal) or flowpack. Specific film grades are available here, with improved toughness, modified COF (coefficient of friction) or transparency. In addition some unique ‘Home Compostable‘ solutions are available, intended for use in specific markets in which this property might be specifically requested. bioplastics MAGAZINE [06/09] Vol. 4 21
