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Bottle Applications

Bottle Applications Extrusion Blow Moulding Fig 1: oval and round bottle made by W. Müller, Troisdorf, Germany By Michael Thielen Besides films and bags, rigid packaging such as trays or clamshells, and bottles, are all part of the huge range of packaging applications where bioplastics are increasingly being used. However, when talking about bioplastic bottles most people immediately think of stretch blow moulded PLA bottles, which look very similar to PET bottles. The first bottles that appeared on the supermarket shelves in the early 1990s were however, extrusion blow moulded shampoo-bottles. Under the brand name Sanara the German company Wella marketed a shampoo that was packed in extrusion blow moulded PHBV (Biopol by ICI, see bM 02/2009). After market introduction in Japan in 1991 and the USA in 1995 these applications disappeared. Since then I have seen an increasing number of bottle samples that have been extrusion blow moulded from different types of biopolymer. Having worked in the blow moulding industry for almost 15 years I am prepared to say that most of the bottles that came into my hands were of a rather poor quality in terms of rigidity, wall thickness distribution or surface appearance. The most recent example that I found did however really attract my interest. This generic oval bottle (shampoo or ketchup style) was made from a mix of different grades of Bio-Flex ® (PLA/Copolyester blend) developed by FKuR/ Fraunhofer UMSICHT in Germany. The bottles are not yet in the market for any commercial application, but I was impressed by their nice pearlescent, slightly glossy surface, their perfect wall thickness distribution - and the subjective rigidity that comes close to conventional HDPE bottles. It all started when a sales manager from W. Müller GmbH of Troisdorf, Germany (a supplier of extruders, heads and auxiliaries for blow moulding machines) came across the BioFlex resins from FKuR. For test runs on W. Müller‘s own brand laboratory machine an existing ketchup bottle mould and a small round bottle mould were chosen. In order to find the optimum grade for this kind of application, two types of BioFlex were blended in different ratios. Firstly, not all thermoplastic materials can be extrusion blow moulded - a certain melt strength is needed because the extruded tube-like parison needs to hang freely below the die-head of the blow moulding machine. However, even the softer grade BioFlex F 2110 could be processed into a parison and subsequently inflated into the mould to form a bottle. This bottle was, however, rather soft. So, in the next steps, BioFlex F 2110 was dry blended with the more rigid BioFlex F 6510. The most promising results were achieved with a mix of 80% BioFlex F 6510 and 20% BioFlex F 2110. 22 bioplastics MAGAZINE [04/09] Vol. 4

Bottle Applications of Bioplastics The W. Müller WMB 4-100 single station blow moulding machine is a shuttle type machine equipped with a continuous single parison head S1/60 (60mm max. die diameter). The 40mm extruder (L/D=25) was run with a standard PE-screw and a smooth barrel. “Basically the BioFlex resins can be processed on standard blow moulding equipment without any hardware modifications, “says Michael Lang, Laboratory Manager at W. Müller, “The only issue that needs attention is the temperature profile in the extruder and head,“ he adds. The temperatures were all in the range of 170-180°C. The final bottles are currently being tested in different longterm evaluations. Company Joh. Sieben from Heinsberg, Germany blow moulded the square bottle shown in Fig 2. Mr. Karl Schütt, Technical Manager of Joh. Sieben told bioplastics MAGAZINE that even bottles made from 100% BioFlex F 6510 easily survived a droptest from a height of 1.5 m. One well known challenge for BioFlex in this kind of application is its limited barrier against water vapour and (depending on the product to be filled) against other media such as oxygen or aromatic compounds. However, the production of a multilayer structure, for instance with a barrier layer embedded between an inner and outer layer of the base material, is technologically an easy task in extrusion blow moulding. And there are already a few biodegradable barrier materials available. Such materials are, for example, Nichigo-G (an amorphous vinyl alcohol, see page 30), PGA and others. Future experiments will be carried out to determine whether these resins are suitable for use in improving the barrier properties. Even if today‘s bioplastic bottles are almost exclusively stretch blow moulded from PLA, extrusion blow moulding with its tremendous versatility with regard to possible shapes and freedom of design for hollow articles - not only for packaging applications - offers a huge potential for bioplastics applications. Fig 2: Square Bottle made by Joh. Sieben, Heinsberg, Germany Fig 3: Piggy bank blow moulded from 100% BioFlex F 6510 on a Kautex KEB 5 at Dr. Reinold Hagen Stiftung Bonn, Germany In any case, most of the 120 customers at W. Müller‘s open house a few weeks ago were as impressed as I was when the BioFlex F bottles were presented for the first time to a broader public. In addition W. Müller showed a 3-layer bottle made from HDPE as the inner and outer layers and with a middle layer made from a starch based biopolymer by Cardia Bioplastics ® of Australia. bioplastics MAGAZINE [04/09] Vol. 4 23

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