Enhancement of the kinetics of the aeration of ethylene oxide sterilized polymers using microwave radiation.

Abstract

Ethylene oxide (EO) is used extensively to sterilize medical supplies that are heat sensitive. EO residues in materials post sterilization can present a hazard to patients at the point of use. Protracted aeration (i.e. degassing) times are necessary post sterilization to reduce EO residues to an accepted level. The sorption of EO into polyvinylchloride was found to be an active process given that at sorption equilibrium (i.e. when the net flow of diffusant into the host material has reduced to zero) the number of molecules of EO per unit volume was greater in PVC than in its external environment. The diffusion coefficient (D) was concentration (c) dependent and the relationship which best describes this dependence was D(c) alpha ln c. The diffusion of EO was dramatically accelerated (as evidenced by a time saving in degassing of up to 400%) if microwave heating (2.45 GHz) was used instead of conventional heating for the same macroscopic temperature. The values of activation energy for diffusion were obtained from the respective Arrhenius plots of diffusion coefficient versus inverse temperature for each process. In general, even small reductions in activation energy can greatly increase the specific rate of reaction. The relative efficacy of microwaves in eliminating EO residues as evidenced by this data occurs as a result of microwaves reducing the activation energy for diffusion by almost a factor of two. The relative efficiency of microwave desorption compared to conventional aeration offers considerable gains in the cost-effectiveness of gas sterilization since it will permit a much greater throughput of material, thereby obviating the need for excessively large inventories of equipment.

AI evidence extraction

Main findings

Microwave heating at 2.45 GHz accelerated diffusion/desorption of ethylene oxide from polyvinylchloride compared with conventional heating at the same macroscopic temperature, with reported degassing time savings of up to 400%. The abstract reports that microwaves reduced the activation energy for diffusion by almost a factor of two, based on Arrhenius plots of diffusion coefficient versus inverse temperature.

Outcomes measured

• ethylene oxide (EO) residue elimination/degassing time
• diffusion coefficient of EO in polyvinylchloride (PVC)
• activation energy for diffusion (Arrhenius relationship)

Limitations

• No sample size or experimental design details provided in the abstract.
• No exposure metrics beyond frequency (e.g., power density, field strength, SAR) are reported.
• Findings are specific to EO diffusion/desorption in PVC and may not generalize to other polymers or conditions.

{
    "study_type": "engineering",
    "exposure": {
        "band": "microwave",
        "source": "microwave heating",
        "frequency_mhz": 2450,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "ethylene oxide (EO) residue elimination/degassing time",
        "diffusion coefficient of EO in polyvinylchloride (PVC)",
        "activation energy for diffusion (Arrhenius relationship)"
    ],
    "main_findings": "Microwave heating at 2.45 GHz accelerated diffusion/desorption of ethylene oxide from polyvinylchloride compared with conventional heating at the same macroscopic temperature, with reported degassing time savings of up to 400%. The abstract reports that microwaves reduced the activation energy for diffusion by almost a factor of two, based on Arrhenius plots of diffusion coefficient versus inverse temperature.",
    "effect_direction": "benefit",
    "limitations": [
        "No sample size or experimental design details provided in the abstract.",
        "No exposure metrics beyond frequency (e.g., power density, field strength, SAR) are reported.",
        "Findings are specific to EO diffusion/desorption in PVC and may not generalize to other polymers or conditions."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "ethylene oxide",
        "sterilization",
        "aeration",
        "degassing",
        "polyvinylchloride",
        "diffusion coefficient",
        "activation energy",
        "microwave heating",
        "2.45 GHz"
    ],
    "suggested_hubs": []
}

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