Transport of ethylene oxide through polymer films

Abstract

SynopsisThe transport of gaseous ethylene oxide (EtO) in several polymer f i l m s is studied using the carrier gas method of measurement. Permeability, solubility, and diffusion coefficients describing ethylene oxide (EtO) transport in polypropylene, polyvinylchloride, Teflon-FEP copolymer, and polyethylene films have been obtained over a 30 Celsius degree range at a low concentration of EtO using the carrier gas method of measurement. The results indicate that the diffusion of EtO in polyethylene is independent of penetrant concentration over the range of concentrations used.However, concentration-independent d i e o n could not be verified directly for the other films studied. Two different techniques of determining difwion coefficients were used, and within the precision of the data both yield the same result. An excess enthaIpy of solution for the solubility of EtO in Teflon-FEP copolymer was calculated, an observation that suggests that dual-mode sorption may be taking place.

Solvent or thermal extraction of ethylene oxide from polymeric materials: Medical device considerations

“…Of all the polymers described here, the glassiest is PC ( T g = 147°C), having a reported diffusion constant D ∼ 1.2 × 10 −9 . The least glassy is HDPE ( T g = −125°C), with a reported diffusion constant ∼10 −7 cm 2 /s.13, 16–18 Importantly, the thicknesses of all the polymer samples are greater than the respective thicknesses that would have allowed equilibrium absorption, based on literature values for diffusion coefficients . Since equilibrium absorption is precluded, amounts of EO extracted can be normalized using surface area, with the polymers considered semi‐infinite slabs.…”

“…The least glassy is HDPE (T g 5 21258C), with a reported diffusion constant 10 27 cm 2 /s.13, 16-18 Importantly, the thicknesses of all the polymer samples are greater than the respective thicknesses that would have allowed equilibrium absorption, based on literature values for diffusion coefficients. 13,[16][17][18] Since equilibrium absorption is precluded, amounts of EO extracted can be normalized using surface area, with the polymers considered semiinfinite slabs. After EO sterilization, triplicate samples of each polymer were extracted for each set of conditions.…”

“…From the fields of transport phenomena and thermodynamics, we know that there are two factors which determine the uptake of EO into polymers. One is the diffusion kinetics, which determines how quickly an EO molecule moves through a 3D network of polymer chains . Crystalline and glassy polymers afford the slowest diffusion kinetics, while less glassy materials allow for faster diffusion kinetics.…”

“…One is the diffusion kinetics, which determines how quickly an EO molecule moves through a 3D network of polymer chains. 13,[16][17][18] Crystalline and glassy polymers afford the slowest diffusion kinetics, while less glassy materials allow for faster diffusion kinetics. Temperature also affects the phase and morphology of polymers, as well as the diffusion coefficient of the EO molecule.…”

“…In this multifactorial space, we will explore whether the thermodynamic nature of the polymer-EO-solvent system can be used to discern trends in exhaustive extraction data. While such an approach does not explicitly quantitatively call out the intricacies of diffusion kinetics (beyond the scope of this manuscript and covered by other sources 13,[16][17][18] ), we hope to identify a useful framework that will inform decisionmaking in medical device manufacturing. For example, it may help a device manufacturer decide (1) between materials, (2) whether to use EO as a sterilant, or (3) on the appropriate conditions for assessing residual EO.…”