Fraunhofer-Institut für Silicatforschung ISC Neunerplatz 2, 97082 Würzburg www.isc.fraunhofer.de
Biodegradable barrier hybrid materials
Class I hybrid Class II hybrid
biodegradable polymer
ORMOCER®
covalent bonding
Development of biodegradable functional coatings for food packaging
Susanne Koch1,2, Daniela Collin2, Sabine Amberg-Schwab2, Gerhard Sextl1,2
1 Universität Würzburg, Lehrstuhl für Chemische Technologie der Materialsynthese, Röntgenring 11, 97070 Würzburg, Deutschland 2 Fraunhofer-Institut für Silicatforschung, Neunerplatz 2, 97082 Würzburg, Deutschland
Contact: Dr. Sabine Amberg-Schwab [email protected] Daniela Collin [email protected] Susanne Koch [email protected]
Summary • Incorporation of modified biodegradable polymers into a high-barrier ORMOCER® • Perpetuation of good barrier properties after insertion of biodegradable polymers • First biodegradation results are promising
Outlook • Optimization of barrier behavior and biodegradability • Development of further functional properties of the coatings
Chitosan
Acknowledgement This work has been part of the EU project DIBBIOPACK and was partially funded by a grant of Stiftung Industrieforschung (S. Koch). Additionally, the authors want to thank J. Prieschl, A. Burger and H. Bleicher for their practical support.
Literature [1] S. Amberg-Schwab in S. Sakka: Handbook of Sol-Gel Science and Technology, Kluwer Academic Publisher, Massachusetts, 2005, Vol. III: 455-478.
Barrier properties
Introduction
Polycaprolactone triol triethoxysilane (PCLTT)
Solution of ORMOCER® precursors
ORMOCER® sol
Hydrolysis and condensation
Incorporation of the chitosan solution
Doctor blading
Transparent coating (film thickness: 2 – 3 µm)
Solution of ORMOCER® precursors
PCLTT- ORMOCER®
sol
Hydrolysis and condensation
PCLTT Doctor blading
Organic & inorganic network formation,
densification, thermal curing
Organic & inorganic network formation, densification,
thermal curing
Oxygen transmission rates* (DIN 53380-3) (50 % relative humidity, 23 °C) in [cm3/(m2·d·bar)]
0
0,1
0,2
0,3
0
0,05
0,1
0,15
Water vapor transmission rates* (DIN 53122-2) (90 % relative humidity, 38 °C) in [g/(m2·d·bar)]
Transparent coating (film thickness: 2 – 3 µm)
0 µm 4 µm I I
Biodegradation via composting
Height profiles of the coating surfaces (laser scanning microscopy):
High-barrier coating materials based on ORMOCER®s (Trademark of the Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. in München) in combination with inorganic SiOx-layers provide an excellent barrier against water vapor and oxygen. These inorganic-organic hybrid polymers are synthesized via the sol-gel process and have strong covalent bonds between the inorganic and the organic moieties. However, ORMOCER® materials are not adequate for the utilization as functional coatings for
biodegradable packaging as these state of the art materials exhibit a poor biodegradability. Therefore, within this contribution a new class of ORMOCER® coating materials was developed, which shows biodegradability and high-barrier properties. These novel hybrid materials consist of an ORMOCER® coating modified by the biodegradable polymers chitosan and polycaprolactone.
30 wt.-% chitosan in ORMOCER® on PET-film
6 weeks …
10 µm © Fraunhofer ISC
10 µm © Fraunhofer ISC
10 µm © Fraunhofer ISC
200 µm © Fraunhofer ISC
200 µm © Fraunhofer ISC
200 µm © Fraunhofer ISC
200 µm © Fraunhofer ISC
© Fraunhofer ISC
State of the art ORMOCER® on PET-film
6 weeks
200 µm 200 µm © Fraunhofer ISC © Fraunhofer ISC © Fraunhofer ISC © Fraunhofer ISC
200 µm 200 µm
10 µm 10 µm © Fraunhofer ISC © Fraunhofer ISC
60 wt.-% PCLTT in ORMOCER® on PET-film
10 µm © Fraunhofer ISC
200 µm © Fraunhofer ISC
200 µm © Fraunhofer ISC
Coating shows cracks and delamination
All coatings had been coated on PET/SiOx-films. For comparison reasons the transmission rates in the case of the pure substrate and a state of the art ORMOCER® on PET/SiOx are shown as well. Compared to the state of the art high-barrier ORMOCER® the barrier of the novel coatings only decreases slightly. Therefore the coatings can be utilized for food packaging applications.
OH
OH
OH
+ OCN Si
OO
O
O
O
NH Si
OO
O
OH
OH80 °C, 18 h
PCLT
Hetero-atoms E = Al, Zr, Ti, …
Functional groups
Inorganic silicate network
Organic crosslinking
S i O
O
O
E
S i
O
O O
O
O
O
S i O
R
O S i
ORMOCER® structure Synthesis of PCLTT
Functional groups for covalent coupling to the inorganic
ORMOCER® network
Incorporation of PCLTT into the ORMOCER® as precursor
200 µm 200 µm
10 µm
© Fraunhofer ISC © Fraunhofer ISC
© Fraunhofer ISC
6 weeks
*For each sample two measurements were carried out.
No observable degradation
No observable degradation yet
…
…
Dissolution of chitosan
Incorporation of chitosan into the ORMOCER®-sol as additive
