Enhancement of thermal,mechanical,and barrier properties of ethylene vinyl alcohol copolymer by incorporation of graphene nanosheets

For the application of high gas barrier coatings on polymeric film, ethylene vinyl alcohol (EVOH) copolymer-based nanocomposites were prepared by the incorporation of two different graphene oxide (GrO) nanosheets with high and low levels of chemical functionalization via a solution blending method. We attempted the evaluation of compatibility between EVOH with amphiphilic nature and GrO dispersed in the nanocomposite by investigating the effect of the degree of functionalization of GrO on the morphology and properties of the nanocomposites. The highly functionalized GrO (HGrO) was observed to cause a more homogeneous dispersion of highly intercalated or exfoliated graphene nanosheets in the nanocomposite as well as a more stable dispersion without sedimentation in the suspension, compared with the GrO with low functionality (LGrO). The incorporation of graphene nanosheets at only 0.5 wt% into the EVOH matrix was revealed to increase the glass transition and crystallization temperatures and remarkably improve the mechanical tensile moduli for the nanocomposite films, regardless of graphene type. In addition, GrO/EVOH nanocomposite-coated biaxially oriented polypropylene films showed substantially improved oxygen barrier properties, while retaining fairly good transparency. As a result, the enhancement in the thermal, mechanical, and barrier properties of the GrO/EVOH nanocomposites was more pronounced when HGrO was incorporated into the EVOH resin, suggesting that GrO nanosheet with high level of functionalization would be more compatible with EVOH and would ultimately be capable of achieving a high-performance EVOH-based nanocomposite.