Dose-dependent degradation and long-term ageing effects in electron beam-irradiated natural rubber latex catheters

Sterilization of polymer-based medical catheters using electron beam (EB) irradiation is effective but may compromise long-term material stability. This study investigates the effects of EB doses (25–100 kGy) on the structural, thermal, and chemical properties of natural rubber latex Foley catheters, both immediately after exposure and following 20 months of ambient ageing. Catheters were characterized using Environmental Scanning Electron Microscopy (E-SEM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). Results show that low-dose irradiation (25 kGy) induced minimal changes, whereas higher doses (≥50 kGy) produced surface fissures, elevated glass transition temperatures, and enhanced crystallinity, consistent with radiation-induced crosslinking. Ageing amplified these effects, broadening the Tg region, reducing viscoelastic stability, and introducing oxidative degradation, evidenced by carbonyl and hydroxyl group formation in FTIR spectra. XRD confirmed dose-dependent crystallinity increases in aged samples, supporting heterogeneous structural rearrangements detected by DSC. Microbiological assays of aged catheters showed no detectable bacterial, yeast, or coliform growth in EB-irradiated samples, indicating effective microbial suppression under the conditions tested even after prolonged storage. Together, these findings highlight the dual role of EB irradiation in sterilization and structural modification, emphasizing the need to balance sterilization efficacy with long-term performance in natural rubber latex–based medical devices. • Dose-dependent EB effects (25–100 kGy) linked to crosslinking and chain scission. • Long-term ambient ageing reveals accelerated oxidative degradation. • Multi-technique analysis (DSC, DMA, FTIR, XRD, E-SEM) shows structural evolution. • Findings guide sterilization dose optimization for safer medical device longevity.