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Large Scale Self-Assembly of Smectic Nanocomposite Films by Doctor Blading versus Spray Coating: Impact of Crystal Quality on Barrier Properties
journal contribution
posted on 2017-05-16, 00:00 authored by Evgeny
S. Tsurko, Patrick Feicht, Frederik Nehm, Kevin Ament, Sabine Rosenfeldt, Ines Pietsch, Konrad Roschmann, Hussein Kalo, Josef BreuFlexible
transparent barrier films are required in various fields
of application ranging from flexible, transparent food packaging to
display encapsulation. Environmentally friendly, waterborne polymer–clay
nanocomposites would be preferred but fail to meet in particular requirements
for ultra high water vapor barriers. Here we show that self-assembly
of nanocomposite films into one-dimensional crystalline (smectic)
polymer–clay domains is a so-far overlooked key-factor capable
of suppressing water vapor diffusivity despite appreciable swelling
at elevated temperatures and relative humidity (R.H.). Moreover, barrier
performance was shown to improve with quality of the crystalline order.
In this respect, spray coating is superior to doctor blading because
it yields significantly better ordered structures. For spray-coated
waterborne nanocomposite films (21.4 μm) ultra high barrier
specifications are met at 23 °C and 50% R.H. with oxygen transmission
rates (OTR) < 0.0005 cm3 m–2 day–1 bar–1 and water vapor transmissions
rates (WVTR) of 0.0007 g m–2 day–1. Even in the most challenging environments (38 °C and 90% R.H.),
values as low as 0.24 cm3 m–2 day–1 bar–1 and 0.003 g m–2 day–1 were found for OTR and WVTR, respectively.
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Large Scale Self-AssemblyDoctor Bladingbarrier filmsnanocomposite filmsfood packagingspray coatingwater vapor barrierscmWVTRBarrier Propertiesdoctor bladingoxygen transmission ratesR.HCrystal Qualitybarrier performancewater vapor diffusivitypolymerwater vapor transmissions ratesdisplay encapsulationbarrier specificationsSmectic Nanocomposite FilmsSpray CoatingwaterborneOTR
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