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Compostable packaging material

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Scientists develop foamable particles that are based on renewable resources

2017-04-25

Thanks to a new processing technique, foamable particles that are based on renewable resources can be processed into individual molded parts, e. g. for utilization as packaging material. Subsequent to use, the foam parts are compostable.

 - Molded foam parts glued together with water.
© Fraunhofer UMSICHT
Molded foam parts glued together with water.

Due to their product properties – light-weight, insulating, form-fitting –, particle foams can be utilized, among other areas, in the automotive, logistics, and packaging sectors. Conventional foams, made of – for example – EPS (expanded polystyrene) or EPP (expanded polypropylene), are based on fossil source materials and are manufactured in molding machines with the help of steam and the effects of temperature and pressure.

Sustainable particles

Jointly with industry project partners as well as the Institute for Food and Environmental Research (ILU e. V.), Fraunhofer UMSICHT has developed an alternative that consists primarily of vegetable starch and water. Additional additives can supplement the formulation. “Our task was to manufacture starch particles that are as sustainable and biodegradable as possible that correspond to conventional, petro-chemically based particles in their properties’ profile,” explained Dr. Stephan Kabasci, Head of the Department Bio-based Plastics at Fraunhofer UMSICHT. With an eye on the existing packaging market, the pricing also had to be taken into consideration in the selection of the components of the formulation.

In multiple series of tests with the novel starch particles, different foaming processes were tested. In direct comparison, a temperature-controlled slab press provided for the best results. For this, the starch particles are filled into a forming tool and fixated between two slabs for a specified time under pressure. So-called injection compression molds and/or die tools that feature a punch protruding into the negative mold are being utilized. This allows for a direct build-up of pressure in the direction of the particles located in the mold. For the expansion effect of the material, the pressure is a decisive factor in addition to the correct temperature-control that effects the formation of steam.

Compact molded parts

Then the distance between the two slabs is being increased and the cooling off of the die tool is being initiated. This cooling-down process is carried out under counter-pressure so that the starch particles can expand, however not beyond the desired geometry of the molded part. “This way, we can manufacture compact molded parts with a closed and flat surface,” said Kabasci.

Through water pressure and contact pressure, multiple molded parts can be glued to one another and additional geometries can be realized through cutting. Areas of use are, for example, edge protection for the transport of goods that are sensitive to shock, product-protecting spacers in packaging, or the replacement of polystyrene-based floral arrangement foams.