Study of the mechanical behavior of gamma-irradiated single-use bag seals

Abstract

• Seal resistance under strain maintained whatever the gamma irradiation dose. • Seal integrity unchanged in PE and EVA bags whatever the gamma irradiation dose. • Same tensile behavior of all the PE bag seals. • Seal mechanical behavior depending on the seal location on the EVA bag. To protect from the external environment the solutions stored in the single use plastic bags used in the biopharmaceutical industry, perfect sealing of the bag is necessary to maintain confinement integrity. These single use plastic bags are manufactured from two different multilayer films, an EVA (ethyl vinyl acetate)/EVOH (ethyl vinyl alcohol)/EVA film and a PE (polyethylene)/EVOH/PE film. The EVA or PE contact layer provides chemical biocompatibility with the bag content (biological solution, food, etc.) in contact with the plastic while the EVOH layer provides oxygen barrier properties. Our first objective was to study the impact of the gamma irradiation dose (from 0 kGy to 270 kGy) on the mechanical tensile behavior of the seals. Our second objective was to evaluate the impact of the location of the seals on their tensile properties. The study showed that the seals are never impacted during tensile testing: this evaluation reveals that in fine cracking of the film occurs before any modification of the seal. Its function of closure and content protection from the external environment is fully achieved, whatever the gamma irradiation dose and the seal location. Only the multilayer film on both sides of the seal is altered after 100 % elongation strain. The EVA/EVOH/EVA and the PE/EVOH/PE multilayer films showed no degradation for a y-irradiation dose up to 115 kGy whereas they were altered at 270 kGy. The seals at different locations on the EVA bag showed different film mechanical behaviors, in correlation with the orientation of the polymer film extrusion process.