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To improve the oxygen and water vapor barrier properties of ethylene vinyl alcohol, EVOH/EFG nanocomposite films under high humidity conditions, we successfully prepared highly exfoliated graphite (EFG) containing a monolayer or a few layers of graphene via rapid heating treatment and ultrasonication as confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), elemental analysis (EA), and nitrogen adsorption–desorption analysis. Six different EVOH/EFG nanocomposite films containing as‐prepared EFG were prepared via a solvent blend method and their physical and barrier properties at different relative humidities were investigated as a function of EFG content. Depending on the EFG content, oxygen transmission rate (OTR) decreased from 3.7 to 0.1 cc/m2/day at dry condition, and the difference in OTR between dry condition and humid condition decreased from 6.5 to 2.3 cc/m2/day. Barrier properties of the EVOH/EFG nanocomposite films were strongly dependent on their chemical structure and morphology. Crystallinity, tortuous path length, and hydrophobicity of EVOH/EFG nanocomposite films were enhanced by the addition of EFG. However, the thermal stability and glass transition temperature of the nanocomposite films were not improved by incorporation of EFG due to the weak interaction between EVOH and EFG. To maximize the performance of EVOH/EFG nanocomposite films, the compatibility of the polymer matrix and fillers needs to be improved. POLYM. COMPOS., 35:644–654, 2014. © 2013 Society of Plastics Engineers

Ethylene-vinyl alcohol copolymer (EVOH)/exfoliated graphite (EFG) nanocomposite films were prepared by precoating EFG on the EVOH surface and conducting a successive melt-extrusion process. Their physical properties were strongly dependent on the EFG content and the mixing method, which strongly affected the morphology and surface properties of the nanocomposite films. The hydrophobicity and water resistance property of EVOH increased by incorporating hydrophobic EFG and their effects were more pronounced in the precoating method, which is related to good dispersion of EFG in EVOH and an enhanced crystalline structure. The incorporation of EFG into EVOH by the precoating method more effectively diminished the dependence of the relative humidity on the oxygen transmission rate of pure EVOH and increased the oxygen barrier properties of EVOH at a high relative humidity. The incorporation of EFG into EVOH by the precoating method also induced relatively more enhanced thermal stability. These results suggest the feasibility of the application of moisture-sensitive EVOH resin for food packaging films. POLYM. COMPOS., 37:1744-1753

Tyvek®, as an ethylene oxide (EtO) gas sterile medical packaging material with a high‐gas permeation and serving as an excellent microbial barrier, must be coated with heat‐sealable adhesives to thermally seal various plastic packaging trays or films. Tyvek® sheet coated with heat‐sealable adhesives must have both porous structure and good sealing strength to various substrates. In this study, an acid pre‐coating method was distinctively introduced to minimize reactions between the blowing agent and acid during mixing, to resultantly generate ethyl vinyl acetate (EVA) layers with porous structure on Tyvek® sheets. To determine the feasibility of applying the as‐prepared coated Tyvek® as a sterile medical packaging material, we investigated the properties of the coating solution and coated Tyvek® as a function of process and additive composition. Finally, EtO gas sterilization tests were performed, and property changes in the coated Tyvek® were investigated. Properties of the coated Tyvek® were strongly dependent on the pre‐coating process and the composition of various additives. Pre‐coating with citric acid led to less of a reaction between citric acid and ammonium carbonate as a blowing agent during mixing and resulted in both good seal strength and air permeation for the coated Tyvek® sheets. The coated Tyvek® sheets, composed of a water‐based EVA emulsion solution with various additives, were not affected by the EtO sterilization process and yielded good resistance to humidity, EtO gas and vacuum cycles. The coated Tyvek® sheets prepared by applying an acid pre‐coating may be a promising candidate for gas sterilizable medical device packaging materials. Copyright © 2017 John Wiley & Sons, Ltd.