Issue 04/2018

Coffee capsules & pods
Bio-PBS to
increase
benefits
of PLA coffee
capsules
BIO PBS
Flexible
Higher
Faster
Translucent
Higher
Lower
Lower
By:
Fabien Resweber & Pissapak Srihaphan
PTT MCC Biochem Company Limited
Bangkok, Thailand
Flexibility
Impact strength
Biodegradability
Heat resistance
Process temp.
Heat-seal temp.
Transparency
Rigid
Lower
Slower
Lower
Higher
Higher
PLA
Transparent
The coffee capsules sold by one major brand in 2013 alone
created enough waste to encircle the earth more than
ten times. The high fraction of water and coffee grounds
makes them difficult to incinerate or recycle, a problem that
could easily be circumvented by using compostable capsules
based on BioPBS. The benefits of BioPBS were introduced
during a presentation at two separate Single Serve Capsules
conferences, one last year in Berlin, the other this year in Chicago,
in which the outstanding compostability of this material
was highlighted.
BioPBS reduces cycle time while increasing HDT
and Izod Impact strength
One key benefit of blending BioPBS with PLA for injection
moulding is that the degree of crystallinity of the matrix
increases. PLA is an amorphous material with
a very long cooling time. Adding BioPBS can
therefore significantly shorten its cycle time. In a
PLA blend with 20% BioPBS, the crystallization
process is accelerated, reaching a percentage of
crystallinity of 50 %; in a 40/60 blend of BioPBS/PLA
a peak level of 80 % can be reached. Cycle time
can be cut in half compared to cPLA , without
compromising capsule mould productivity.
Increasing the BioPBS content to 60 % or higher
also improves the thermal properties of PLA,
allowing the HDT A (0.45 MPa) value to be increased to
almost 100 °C. As a result, BioPBS-based capsules
will not twist or lose their shape during use, nor clog
up the coffee machine. Increasing the BioPBS ratio
from 20 to 40 has the additional advantage of improving
the Izod impact strength of the material. Even better
results are achieved if a 60/40 blend of BioPBS/PLA is used.
Basically, the more BioPBS that is added, the more flexibility
that can be expected from the compound. On the other hand,
the PLA component increases the biobased content and adds
solidity to the cap body.
BioPBS meets new challenges for coffee capsules
Previously, compostable coffee capsules had a limited
oxygen barrier and required secondary packaging for
wrapping. New solutions for compostable oxygen barriers
now exist for all coffee capsule designs, decreasing the
total amount of packaging needed. Barrier solutions mainly
include the use of compostable IML (In-Mould-Labelling) or
a compostable barrier layer injection molded in a co-injection
process, and are perfectly compatible with BioPBS-based
compostable capsules.
In countries or cities where organic waste is collected, fully
compostable capsules can be included in that composting
stream, increasing the amount of waste being recycled through
this organic recycling process. However, since industrial
composting facilities are not yet accessible worldwide, there
is now a strong market demand for a coffee capsule that will
biodegrade in a home composting environment at ambient
temperatures. BioPBS offers a way to make this possible,
as this material provides a fast degrading polymer matrix,
even at ambient temperature. BioPBS is increasingly gaining
acceptance and is used as the raw material in various global
sustainable coffee capsule brands for injection
moulded and mesh parts.
Total solution for compostable coffee
capsules
BioPBS can be applied in all the various parts
of the coffee capsule, depending on the grade
used. BioPBS lidding film (BioPBS sealant +
barrier cellulose) provides an excellent oxygen
barrier; BioPBS body or cap offers flexibility,
heat resistance, and reduced cycle time. Finally,
BioPBS can be used in a mesh (nonwoven filter)
part on the bottom of the capsule to retain the
ground coffee.
The burgeoning popularity of single serve coffee
capsules is cause for concern, as their use generates
a vast amount of waste. Changing to a BioPBS capsule
could definitely help solve this waste problem.
Environmental benefits
Formulating a coffee capsule material with a high BioPBS
content can contribute to the reduction of non-recyclable
waste and decrease the impact on the environment. Capsules
made with BioPBS can be treated as organic waste, which
means they can be disposed of in the organic waste bin (where
available and permitted) without separating them from the
coffee grounds. In applications like this, where it is impossible
to re-use or recycle, compostable materials definitely
contribute to cleaner end-of-life options and lower disposal
costs.
www.pttmcc.com
40 bioplastics MAGAZINE [04/18] Vol. 13