Issue 06/2020

Films/Flexibles/Bags
By:
Silvia Kliem, Research Associate
Christian Bonten, Professor
Institut für Kunststofftechnik
Univ. Stuttgart, Germany
By:
Silvia Kliem, Research Associate
Christian Bonten, Professor
Institut für Kunststofftechnik
Univ. Stuttgart, Germany
Biodegradable blown film with biodegradable softener
in isolated pieces of film with high film thickness. The
compounds with 5 % citrate allowed at least temporarily
a continuous extrusion and the inflation of a film tube, film
gauges of about 50 µm could be achieved. Only the compound
with 10 % citrate could be processed in a stable and continuous
process, the average film thickness was below 25 µm. Due to
the high crystallinity of PHBV, the films are semitransparent.
In contrast to films based on pure PLA, which are often
criticized for their loud crackling, they resemble commercially
available plastic films made of PE in terms of haptics. The
tensile test of the films in Figure 2 shows a clearly changed
elongation behavior of the modified compounds towards an
elastic behavior with a maximum elongation of just over 5 %.
Conclusion
Especially in the agricultural sector, there is a great demand
for biodegradable films. In addition to suitable polymers,
attention must also be paid to the use of environmentally
friendly additives. In this project, it was possible for the first
time to produce blown films with a mass portion of almost
70 % of very well biodegradable PHBV. By using biobased
and biodegradable citric acid ester as plasticizer and a small
percentage of PLA as blending partner it can be assumed
that the films presented here can be completely metabolized
in our environment without leaving residues in the form
of microplastics in the soil. Besides an optimization of the
formulation and the transfer to industrial scale, the proof of
this degradability in further investigations is of great interest.
Acknowledgements
This project was supported by Jungbunzlauer Ladenburg
GmbH. We thank the project partners for the good cooperation.
A more detailed version of this article was already published
in the magazine “Kunststoffe”, issue 09/2020.
www.ikt.uni-stuttgart.de
60
Figure 2: Stress-strain diagram of the blown films produced
50
Stress in MPa
40
30
20
PHBV+PLA
5 % Citrate
10 % Citrate
10
0
0 1 2 3 4 5
Strain in %
bioplastics MAGAZINE [06/20] Vol. 15 15