Abstract:
Hexagonal boron nitride is promising gas barrier material due to higher aspect ratio,
effective corrosion resistant and Hydrophobic nature. Liquid phase exfoliated, size
selected, defect free hexagonal boron nitride (hBN) nanosheets are dispersed in
thermoplastic polyurethane (TPU) via solution processing. Aspect ratio is an important
parameter along with the volume fraction of filler in relation to the gas permeation of
polymer composites. The range of hBN volume in polymer matrix is fraction 0-1 vol. %.
The aspect ratio of hBN is estimated to be ~331 with the help of transmission electron
microscope. With the inclusion of minute level of hBN, the permeation reduction levels
are considerably enhanced for Co2 in hBN-TPU composites. By addition of just 0.011
vol% nanosheets, permeability is reduced up to 54%. By addition of 0.054 vol%
permeability is fell up to 82%, the maximum attained permeation reduction achieved for
current work. Further increase in the hBN concentration (0.5-1 vol. %) in TPU slightly
reduces the gas retention but still maintains a permeation level of 76-80% as compared
to the base polymer. The reduction in gas retention may be due to the aggregation of
filler inside polymer. X-ray diffraction and tensile testing have validated the aggregation
phenomena. The maximum ultimate tensile strength and Young’s modulus are also
achieved at 0.05 vol. % BN-TPU composites; beyond this loading the mechanical
properties are compromised. Theoretical models predict well the experimental results at
low BN concentrations with Neilson model being the closest but at higher loadings the
results are compromised probably due to restacking of fillers. The enhancement in the
barrier properties for CO2 and the mechanical robustness may pave a way for utilization
of these composites in application like food packaging, biological membranes and in
natural gas transmission pipelines where CO2 causes corrosion due to its acidic nature
