Issue 01/2017

Foam
Starch based particle foam for
biodegradable packaging
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.
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. Jointly with the project partners
Loick Biowertstoff and Storopack Deutschland as well as
the Institute for Food and Environmental Research (ILU),
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 Stephan Kabasci, Head of the
Department Biobased 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.
Temperature-controlled slab press
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.
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, productprotecting
spacers in packaging, or the replacement of
polystyrene-based floral arrangement foams.
www.umsicht.fraunhofer.de
Molded foam parts glued together with water.
Bisected molded foam part made of starch particles.
fill conclude press expand remove
(Photos and graph by Fraunhofer UMSICHT
32 bioplastics MAGAZINE [01/17] Vol. 12