Use of graphene-polymer composites to improve barrier resistance of polymers to liquid and gas permeants

A packaging material or product formed from a polymer with improved barrier resistance to a permeant, wherein the packaging material or product is prepared by a method comprising:

• (a) distributing graphite microparticles into a molten thermoplastic polymer phase of the polymer, wherein at least 50 wt % of the graphite in the graphite microparticles consists of multilayer graphite crystals between 1.0 and 1000 microns thick along the c-axis direction;
• (b) applying a succession of shear strain events to the molten polymer phase so that the shear stress within the molten polymer phase is equal to or greater than the Interlayer Shear Strength (ISS) of the graphite microparticles and the molten polymer phase mechanically exfoliates the graphite successively with each event until the graphite is at least partially exfoliated to form a distribution in the molten polymer phase of single- and multi-layer graphene nanoparticles less than 10 nanometers thick along the c-axis direction, thereby forming a graphene-reinforced polymer matrix composite within the polymer;
• and
• (c) forming a packaging material or product with improved barrier resistance for gas or liquid permeant,
• wherein the mechanically exfoliated graphite produces reactive edges on the single- and/or multi-layer graphene nanoparticles that react with thermoplastic polymers to provide a composite where thermoplastic polymer chain are directly covalently bonded to, and inter-molecularly cross-linked by, the single- and/or multi-layer graphene nanoparticles.