Films|Flexibles|Bags
Films|Flexibles|Bags Design Your Own Compostable Film Multi-layer systems increasing the opportunities for new markets By B. von Hansen J. Schmeling D. Winkelmann P. Zimmermann FKuR Kunststoff GmbH, Willich, Germany Plastics made from renewable resources offer new opportunities and possibilities for both flexible and durable packaging along with general e.g. injection moulding applications. Each day nature shows us well designed packaging solutions. These solutions can be used as a guideline and implemented in our industrial packaging world. Of course, we have different requirements for industrial packaging compared to nature. Most goods need to be transported, stored and protected against surrounding conditions and some need to withstand a long shelf life. Biopolymers, whether biodegradable, based on renewable resources, or both have a similar natural approach. But sometimes they do not fulfil all of the requirements necessary for industrial packaging, in particular the properties of high barrier and transparency. 14 bioplastics MAGAZINE [06/11] Vol. 6
Films|Flexibles|Bags The packaging requirements for barrier properties are not even able to be achieved with polymers based on crude oil. For both conventional and bioplastics a co-extrusion or the lamination of different polymers is the key to fulfil these requirements of today’s packaging applications. Of course, it is still questionable if such high barriers are necessary but achieving such levels is state of the art in packaging technology. In order to enter new markets and increase the range of applications for bioplastics these resins must follow this trend and need to be co-extruded or laminated. Advantages of compostable multilayer systems for food packaging Plastics used for packaging represent around 39 % [Plastics Europe: Plastics – The Facts 2011] of the total plastic consumption and are by far the largest market segment of all plastics applications. The requirements for plastic films, especially for those used predominantly in food packaging, have been constantly rising over recent years and have now reached a level that can only be achieved by means of intelligent material combinations and well-engineered process procedures. In the beginning, biopolymers were mainly designed for applications such as waste bags and shoppers. Transparency was not a requirement. The content of renewable resources of these resins has been around 20 to 40 %. With the upgrading of properties, the range of applications made from biopolymers is constantly growing. In addition, the content of renewable resources in combination with compostability is gaining importance for all kinds of packaging applications. To enter new markets with biopolymers, new resins and compounds have to be created. The major requirements for such modern packaging include a high content of renewable resource materials (>50%) and compostability combined with good barrier properties and preferably transparency. On the one hand, barrier is a necessity for certain packaging, e. g. MAP (Modified Atmosphere Packaging) and other applications where an oxygen barrier is required. On the other hand, there are applications where high permeation and breathability are required, which is where Bio-Flex ® with its intelligent filler system allows up to perfection. Such applications include back sheet films for diapers along with fresh food packaging where transparency is often a key requirement. One of the largest advantages of compostable films is, whenever it is needed, packed goods and films can be disposed together or can be used in a fermentation plant without separating organic goods and films. In order to meet these challenges FKuR Kunststoff GmbH, Willich, and its cooperation partner Fraunhofer UMSICHT, Oberhausen, both Germany, have developed new Bio-Flex resins which exhibit outstanding characteristics when combined in a multilayer structure. The latest developments are focused on flexibility, transparency and a high content of renewable resources, whether in a mono or multilayer film structure. By co-extrusion it is possible to combine the clear and stiff material Bio-Flex A 4100 CL, used in the outer layers with the new transparent Bio-Flex F 2201 CL or translucent Bio-Flex S 1100 in the mid layer. As both resins are flexible and tough they are able to support Bio-Flex A 4100 CL in a multilayer structure. One of the main advantages is that the properties of this film can be adjusted by the variation of each layer. By using respective layer combinations, e.g. greater stiffness or more elasticity of the film, according to the final requirements, can be reached. This is shown in charts 1 and 2. By combining Bio-Flex A 4100 CL with F 2201 CL, the tensile modulus of A 4100 CL can be significantly reduced, while the elongation at break is still at the level of a pure F 2201 CL. The result of this is a 3-layer structure that not only offers superior toughness and flexibility, but at the same time high transparency. In addition to having high quality clarity, the content of renewable resource materials is outstanding for a blown film application. The content of renewable resource materials of a film made from Bio-Flex A 4100 CL / S 1100 / A 4100 CL is 30 to 50%, depending on the structure, whereas with a film made from Bio-Flex A 4100 CL / F 2201 CL / A 4100 CL the content of renewable resources is between 60 to 80% depending on the final film structure. There are no transparent or flexible blown film types similar to the Bio-Flex resins available today. u Chart 1: Tensile Modulus of Bio-Flex mono and multilayer films (MD = machine direction, TD = transversal direction) Modulus of elasticity MD [MPa] 2000 1750 1500 1250 Bio-Flex A 4100 CL / F 2201 CL / A 4100 CL (20 / 60 / 20 [%], 20µm) 1000 Bio-Flex F 2201 CL 750 Bio-Flex A 4100 CL / F 2201 CL A 4100 CL (15 / 70 / 15 [%], 20µm) 500 Bio-Flex S 1100 0 Bio-Flex A 4100 CL / S 1100 / A 4100 CL (20 / 60 / 20 [%], 20µm) Modulus of elasticity TD [MPa] Bio-Flex A 4100 CL | | | | | | | 500 750 1000 1250 1500 1750 2000 Chart 2: Elongation at Break of Bio-Flex mono and multilayer films Elongation at break MD [%] 350 300 250 200 150 100 50 0 Bio-Flex A 4100 CL / S 1100 / A 4100 CL (20 / 60 / 20 [%], 20µm) Bio-Flex A 4100 CL Bio-Flex F 2201 CL Bio-Flex A 4100 CL / F 2201 CL / A 4100 CL (15 / 70 / 15 [%], 20µm) Bio-Flex A 4100 CL / F 2201 CL / A 4100 CL (20 / 60 / 20 [%], 20µm) Bio-Flex S 1100 | | | | | | 50 100 150 200 250 300 350 Elongation at break TD [%] bioplastics MAGAZINE [06/11] Vol. 6 15
