Exploring the interactions between starches, bentonites and plasticizers in sustainable barrier coatings for paper and board

BREEN, Christopher, CLEGG, Francis, THOMPSON, Simon, JARNSTROM, Lars and JOHANSSON, Caisa (2019). Exploring the interactions between starches, bentonites and plasticizers in sustainable barrier coatings for paper and board. Applied Clay Science, 183, p. 105272.

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Link to published version:: https://doi.org/10.1016/j.clay.2019.105272


Effective food packaging is a major factor in the current global drive to minimise food waste. Starch is an excellent oxygen barrier for packaging but it is brittle and moisture sensitive. The addition of layered minerals and plasticizers can significantly improve the moisture barrier and flexibility of the resulting composite. Some combinations of starch and plasticizer are incompatible but our results show that the addition of bentonite ensures the formation of coherent starch films with much improved moisture barrier regardless of the starch-plasticizer compatibility. It was clearly demonstrated that improvement of the moisture barrier was critically dependent on the layer charge of the bentonite used. Starch was readily accommodated in the interlayer space of bentonites with a layer charge of <0.4 electrons per formula unit but was not adsorbed if the layer charge was above this value. Starch-bentonite-plasticizer coatings prepared using bentonites with the lower layer charge routinely produced higher barriers to water vapour. The water vapour transmission rate (WVTR) of the base paper was reduced from 780 to 340 ± 20 g m2 day−1 when coated with starch alone. This was further reduced to 48 or 66 g m2 day−1 if glycerol or lower charge bentonite, respectively, was added to the starch. Optimised coatings of starch-lower charge bentonite-plasticizer provided WVTR values of ≤10 g m2 day−1 whereas WVTR values for comparative coatings prepared using the higher charge bentonites were three to four times higher (35 ± 7 g m2 day−1). Scanning electron micrographs provided clear evidence for the presence of 60 nm thick supramolecular layers formed from starch-bentonite-plasticizer in the samples coated on either glass or paper. The WVTR values for these low-eco footprint coatings are competitive with proprietary coatings prepared using petroleum derived resins.

Item Type: Article
Uncontrolled Keywords: Civil Engineering; 04 Earth Sciences; 09 Engineering
Identification Number: https://doi.org/10.1016/j.clay.2019.105272
Page Range: p. 105272
SWORD Depositor: Symplectic Elements
Depositing User: Symplectic Elements
Date Deposited: 28 Oct 2019 12:56
Last Modified: 17 Mar 2021 22:00
URI: https://shura.shu.ac.uk/id/eprint/25350

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