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05 | 2008

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Bottle Applications PLA

Bottle Applications PLA Bottles the gas barrier performance of EcoSield and EcoSield- WO compared to a PET bottle. The barrier performance is only 1/8 (water vapor) and only 1/9 (oxygen) of that of PET. The EcoSield-WO however, has a slightly improved water vapor barrier performance over the PET bottle. Compared to existing PLA bottles an excellent gas barrier advantage for both water vapor and oxygen can be seen. With these barrier enhancements EcoSield-WO is suitable for oxygen and water vapor sensitive contents, just as a PET bottle. Figure 3 shows the storage temperature dependency on the water vapor barrier performance of EcoSield, EcoSield- WO and the PET bottle. As can be seen, EcoSield-WO has the same water vapor barrier performance as the PET bottle at temperatures of up to 45°C. Thus, EcoSield-WO will be suitable for water vapor sensitive contents similar to a PET bottle. With regard to biodegradability, Toyo Seikan is looking at two points, namely reduction of plastic waste and ease of disposal for each household to achieve a positive contribution to society. EcoSield is biodegradable under certain circumstances. Figure 4 shows the degradation results in an electrically powered house-hold-composter 1 , as it is used in Japanese households. As the picture shows EcoSield can be broken down within 32 hours in such a ‘home-composting unit’ 1 . In addition, the biodegradability was determined by measuring the carbon dioxide generated (ISO 14855 part 2) by the reaction with microorganisms using standard compost and EcoSield at 58°C. EcoSield can be biodegraded within 45 to 50 days, which means that the biodegradability of EcoSield is rapid in controlled compost conditions. With regards to these results, the advantages in disposing of PLA bottles make it possible to promote a change in the way societies approach waste collection and processing. If this bottle becomes more widely used throughout the world the environment would naturally become cleaner. Toyo Seikan seriously hopes that the EcoSield technology will be able to contribute to reducing global warming as much as possible. Fig. 2: Thermal stability 25 Fig. 3: Gas barrier property of water vapor Table 1: Gas barrier performance Start End Over flow volume reduction (%) Water vapor permeation (g/m 2 day) 20 15 10 5 PLA bottle Purchased from Market 0 1.0 2.0 3.0 4.0 5.0 d-isomer content (%) Sample condition: Mold temperature 30 ºC Storage condition: 55 ºC Storage period: 7 days 30 25 20 15 10 5 EcoSield TM (Standard) EcoSield-WO TM (High Barrier) PET 0 0 10 20 30 40 50 Storage temperature (ºC) EcoSield-WO TM (Under development) Bottles H 2 O O 2 PET 1.0 1.0 EcoSield TM (Standard: PLA only) EcoSield-WO TM (High Barrier) 1 / 8 x 1 / 9 x 1.3 x 1.0 x EcoSield-WO TM (Under development) Barrier performance has been improved by Toyo Seikan’s unique gas barrier technology. After 20 treatments (80Hr) After 4 treatments (16Hr) After 16 treatments (64Hr) After 12 treatments (48Hr) After 8 treatments (32Hr) 1: This has nothing in common with what is usually referred to as “home composting”. In such an electric home-composter, temperatures of approx. 80°C are applied to reduce the volume of kitchen waste. Fig. 4: Degradation by ‘home composting’ 1 process bioplastics MAGAZINE [05/08] Vol. 3 25

Bottle Applications Impact of Dry and Wet Sterilisation on PLA Bottles shrinkage of volume in % 7 6 5 4 3 2 1 0 4 6 8 time of rinsing [s] Fig. 1: Bottle shrinkage during 60°C rinsing process remaining H 2 O 2 [ppm] 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 conventional blow molding process optimized blow molding process uncoated PLASMAX coated 1 after treatment after 1 day time after 3 days Fig.2: Residuals for dry sterilization 1: no residuals detectable with PLASMAX Article contributed by Lars von Carlsburg, Application Engineer, KHS Plasmax GmbH, Hamburg, Germany If aseptic cold filling is required to ensure the quality and shelf life of juice, ice tea, dairy products or flavoured water the impact of either dry or wet sterilisation on the container prior to filling also needs to be considered. A known issue with aseptic cold filling is that, depending on the specific conditions of the sterilisation process as well as the technology applied, some sterilisation media might migrate into the container material. After filling, the sterilisation medium in the container wall can partially remigrate into the product. This issue causes, for example, an initial vitamin reduction in fruit juices. Using the barrier coating technology offered by KHS Plasmax, which covers the entire internal surface of the bottle with a thin glass layer, it has already been shown that for PET bottles any migration of H 2 O 2 into the bottle material and subsequent remigration into the product is totally eliminated. Since the material properties of PLA are quite different from those of PET it makes sense to verify the suitability of PLA for the aseptic cold filling process. Properties of PLA bottles During the wet or the dry sterilisation process the bottles are exposed to higher temperatures. This has no significant influence in the case of PET bottles due to their high glass transition temperature. The PLA material however is much more sensitive to higher temperatures because of its lower glass transition and crystallisation temperatures. This can ultimately lead to higher bottle shrinkage. To minimise this shrinkage of PLA bottles and to reach a similar level as seen in PET bottles KHS Corpoplast has optimised the blow moulding process. These optimised PLA bottles were for instance, rinsed with hot water at 60°C to simulate the wet sterilisation. A substantial reduction of the resulting shrinkage from 6% to below 1% was achieved (Fig. 1). Comparison of remigration To determine the possible sterilisation medium residuals for PLA, and to evaluate the benefit of the PLASMAX internal coating, KHS Plasmax tested the remigration in both processes – dry and wet sterilisation on coated and uncoated 330 ml, 35g PLA bottles. These bottles were manufactured using the optimised blow moulding process. 26 bioplastics MAGAZINE [05/08] Vol. 3

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