MATERIALS | PLASTIC POUCHES N R


Right: Bern- hardt has developed a pouch concept that can purify water to make it suitable for drinking


of contamination – and are suitable for fine melt filtration extrusion – while the aluminium is recovered with over 95% metal content and only 2% oxidation, he said.


Water purification Plastic pouches are most typically used for food packaging. However, a new concept developed by Bernhardt-Deltasacs, uses them to purify water to make it suitable for drinking. Its water purification bag uses a


combination of solar radiation and heat to purify water. A coloured back film heightens the heat level in the bag to around 60°C, though it must also be highly transparent – to allow UV light to enter. The 4-litre container needs to be usable for a complete year (400 cycles). The concept, called SaWa, kills more than 99.9%


of dangerous pathogens, said Pierre-Emmanuel Grandjean, managing director at the company. The initial brief, to use PE-only, risked UV


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deterioration and tests showed that multi-layer structures using cast extrusion combining PP, PA and PE could work. “The external PP face is


heat stable and ensures good sealability,” he said. “We included UV-additives using the experience of our suppliers in films used for agriculture in Spain.” The back film’s coloration is achieved with a masterbatch.


The pouch is assembled from two asymmetric films, which involves careful


synchronisation and tension management.


Also, a 38mm HDPE spout needs to be inserted. The product has achieved an 80% pass rate in a


0.8m drop test. To improve this, the company is looking to use stronger, better material combinations. The project has now been running for nearly


four years – and more than 600,000 bags have been distributed in Eastern Africa and India. “But there’s still a long way to go address a target group of 2 billion people,” he said.


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