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Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment.

ABSTRACT: An electron beam was irradiated on polyacrylonitrile (PAN) fibers prior to thermal stabilization. The electron-beam irradiation effectively shortened the thermal stabilization process by one fourth compared with the conventional thermal stabilization process. A comprehensive mechanistic study was conducted regarding this shortening of the thermal stabilization by electron-beam irradiation. Various species of chain radicals were produced in PAN fibers by electron-beam irradiation and existed for a relatively long duration, as observed by electron spin resonance spectroscopy. Subsequently, these radicals were gradually oxidized to peroxy radicals in the presence of oxygen under storage or heating. We found that these peroxy radicals (CO) enabled such an effective shortcut of thermal stabilization by acting as intermolecular cross-linking and partial aromatization points in the low temperature range (100-130?°C) and as earlier initiation seeds of successive cyclization reactions in the next temperature range (>130-140?°C) of thermal stabilization. Finally, even at a low irradiation dose (200?kGy), followed by a short heat treatment (230?°C for 30?min), the PAN fibers were sufficiently stabilized to produce carbon fibers with tensile strength and modulus of 2.3 and 216?GPa, respectively, after carbonization.

SUBMITTER: Park S

PROVIDER: S-EPMC4923868 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment.

Park Sejoon S Yoo Seung Hwa SH Kang Ha Ri HR Jo Seong Mu SM Joh Han-Ik HI Lee Sungho S

Scientific reports 20160628

An electron beam was irradiated on polyacrylonitrile (PAN) fibers prior to thermal stabilization. The electron-beam irradiation effectively shortened the thermal stabilization process by one fourth compared with the conventional thermal stabilization process. A comprehensive mechanistic study was conducted regarding this shortening of the thermal stabilization by electron-beam irradiation. Various species of chain radicals were produced in PAN fibers by electron-beam irradiation and existed for ...[more]

PMID: 27349719

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Project description:Sterilization of biodegradable, collagen-based implants is challenging as irradiation sterilization methods can alter their mechanical properties. Electron beam (EB) irradiation is a terminal sterilization method that has been used for biologically-derived implants. Here, recombinant human collagen type III-phosphorylcholine (RHCIII-MPC) hydrogels were irradiated with EB doses of 17, 19, or 21 kGy and their subsequent biocompatibility and ability to promote regeneration in rabbit corneas was evaluated. Unirradiated hydrogels stored in 1% chloroform in phosphate-buffered saline (C-PBS) were the controls. There were no significant differences between irradiated and non-irradiated samples in optical or physical properties (tensile strength, modulus, elasticity), or the ability to support cell growth. However, irradiated implants were more sensitive to high levels of collagenase than unirradiated controls and the C-PBS implants had increased cell growth compared to EB and controls at 72 h. Corneal implants e-beamed at 17 kGy or e-beamed and subsequently frozen (EB-F) to increase shelf-life showed no adverse biological effects of the irradiation. EB, EB-F, and C-PBS implanted corneas all rapidly re-epithelialized but showed mild neovascularization that resolved over 6 months. The regenerated neo-corneas were transparent at 6 months post-operation. In vivo confocal microscopy confirmed normal morphology for the epithelium, stroma, sub-basal nerves and unoperated endothelium. Histology showed that all the regenerated corneas were morphologically similar to the normal. Immunohistochemistry indicated the presence of a differentiated corneal epithelium and functional tear film. In conclusion, the e-beamed corneal implants performed as well as non-irradiated control implants, resulting in fully regenerated neo-corneas with new nerves and without blood vessels or inflammation that may impede vision or corneal function. Therefore, a complete validation study to establish EB irradiation as an effective means for corneal implant sterilization prior to clinical application is necessary as a next step.

Dataset Information

Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment.

Publications

Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment.

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