Coating cellulose nanocrystals on polypropylene and its film adhesion and mechanical properties

Abstract

In this work, we investigated conditions to deposit cellulose nanocrystal (CNC) films onto polypropylene (PP) by spin coating, and studied the adhesion, mechanical property, and oxygen permeability properties of the CNC-coated PP films. It was found that CNC films maintained proper adhesion on UV ozone-treated PP even when deformed, but cracked when bent beyond a critical radius of curvature or scratched with excessive force. We also exposed CNC films to various forms of mechanical strain in order to determine the CNC films’ strength and durability as a coating under different humidity conditions, and found that the film’s scratch resistance increased with longer exposure to humidity. Additional oxygen permeability tests showed that a thin CNC coating film with a thickness of less than 1 μm on UV ozone-treated PP reduced oxygen permeation by 39%. We conclude that CNC films can be coated simply on hydrophobic PP, and the enhanced gas barrier properties of CNC-coated PP could find application in the food packaging industry.