01 | 2008

Foam
PLA foams for
packaging applications
Article contributed by Cesare Vannini,
Packaging System R&D
Coopbox Europe SpA,
Reggio Emilia, Italy
Foams are very common material structures. Wood has a
foam structure, bones are also foams, bread is a foam,
and many other natural materials are foams. Why? The
reason is clear: a foam is a simple way to obtain a structure with
good mechanical properties and low weight. The prime property
of foam is weight reduction. This characteristic is very important
in packaging applications where foams are used to produce
trays, cups, containers, boxes, etc. In all of these products the
weight reduction is between 30 and 50% compared with alternative
rigid materials.
Many retailers have stated their intention to reduce the total
amount of packaging used in their stores, and so a foam seems
the right solution for rigid food packaging applications, independently
of the plastic material selected.
Coopbox is a major producer of foam food packaging, and
has developed this activity within the growing retail industry as
a privileged partner at national and European level for the production
of polystyrene trays.
Today Coopbox, by focusing on the clients‘ needs and on service
and product innovation, has developed a deep understanding
of fresh food packaging systems with different materials: PS,
PET, and recently PLA. Each of these different polymers permits
us to produce packaging systems with specific characteristics:
• NATURALBOX ® with PLA: packaging systems using only
renewable resource that comply with European standard
EN13432 for compostable packaging.
• DRYMAX ® PS: an open cell foam structure for absorbing liquid
in fresh meat and fish packaging
• AERPACK ® PS: foam barrier trays for fresh meat and fish
• DOT ® : crystallised PET foam for heat resistant containers in
ready meals packaging
All of these different materials are processed on a tandem
extruder using different physical foaming gases such as nitrogen
or butane, depending on the required behaviour of the final
package. Specific tooling design and modifications are necessary,
especially for low melt strength materials such as PET or
PLA where the semicrystalline properties require perfect temperature
control to avoid the formation of gels during the extrusion
process.
14 bioplastics MAGAZINE [01/08] Vol. 3