TECHNOLOGY | FOAM
Right: At Fakuma 2018, bottle openers were produced using the new Plastinum foam moulding process
developed by Linde, KIMW and ProTec
exhibition in Germany in October last year. ProTec demonstrated the process using its Somos Per- foamer system and an Engel E-Victory 310/80 injec- tion moulding machine. In the process, polymer granules are first dried in a conditioner unit, and are then impregnated with the carbon dioxide foaming agent in a pressure vessel (autoclave) upstream of the injection moulding machine. The amount absorbed by the granulate depends on the plastic material, pressure, temperature and impregnation time. The CO2 typically remains in the granulate for a period of more than two hours after it has been loaded and the pressure released. “Plastinum is as flexible as chemical foaming, because it is used with any tool without need for modification, and is as precise and reproducible as physical foaming,” said Pavel Szych, Plastics Applications Expert at Linde, who was speaking at AMI’s Polymer Foam conference in Hamburg, Germany in November. Other injection moulding technologies that are part of Linde’s Plastinum product family are gas injection moulding, mould hotspot cooling, and dry ice blasting to clean moulds. The development project for Plastinum foam injection moulding started from scratch in 2015, said Szych. Process development was jointly conducted with KIMW, while ProTec built the
hardware to enable the Plastinum process. The Perfoamer equipment comprises a conditioner with control unit and an autoclave with buffer tank. A conditioner is necessary because it is important that gas impregnation is not done at too high a temperature as it affects the level of absorption, said Szych. The Plastinum process uses CO2 because it is a commonly available gas and it provided the best absorption compared with nitrogen and other gases when tested during development, he said. Linde says the benefits of Plastinum foam injection moulding include: weight savings of up to 60%; cycle time reductions of up to 50%; clamping force reductions of up to 60%; the production of thin walled parts of less than 2mm; and the ability to use engineering plastics. In the development project, more than 60 polymers were tested, including polycarbonate, ABS and glass-reinforced polyamide. Testing was carried out for two hours at 35 bar, using small injection moulded test plates with 4mm wall thickness. The tests were designed to study gas absorption and weight reduction using different polymers, and Szych said the process and equipment were set up to maximise foaming in the testing, not to achieve certain properties in the moulded part.
Customer trials using Plastinum can be done at
KIMW’s facility, where there are injection moulding machines from a variety of manufacturers. Multiple injection moulding machines can be supplied from one gas supply scheme, said Linde. Depending on volume requirements, the CO2 gas can be supplied from cylinder bundles or a bulk tank. Linde and ProTec designed and developed a special manifold to ensure optimum foaming performance and security of supply by automatically switching from an empty to a full cylinder bundle. If a bulk tank is preferred, Linde said the Presus C is an energy- efficient pressure-boosting unit designed for CO2-based moulding processes. “The entire gas supply, boosting and injection package has been
Above: Image shows the Somos Perfoamer units from ProTec for drying and temperature adjusting polymer pellets, loading them with CO2 under pressure and then feeding them to the injection moulding machine. Photo: ProTec Polymer Processing
32 INJECTION WORLD | March 2019
www.injectionworld.com
PHOTO: KIMW
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