The Effect of Coating Process and Additives on EVA Coated Tyvek^® for Gas Sterilizable Medical Packaging Applications

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.