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Type: Text × Subject: Electron beam ×

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Now showing 1 - 5 of 5
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    A new way of toughening of thermoset by dual-cured thermoplastic/thermosetting blend
    (Basel : MDPI, 2019) Khatiwada, Shankar P.; Gohs, Uwe; Lach, Ralf; Heinrich, Gert; Adhikari, Rameshwar
    The work aims at establishing the optimum conditions for dual thermal and electron beam curing of thermosetting systems modified by styrene/butadiene (SB)-based triblock copolymers in order to develop transparent and toughened materials. The work also investigates the effects of curing procedures on the ultimate phase morphology and mechanical properties of these thermoset-SB copolymer blends. It was found that at least 46 mol% of the epoxidation degree of the SB copolymer was needed to enable the miscibility of the modified block copolymer into the epoxy resin. Hence, an electron beam curing dose of ~50 kGy was needed to ensure the formation of micro- and nanostructured transparent blends. The micro- and nanophase-separated thermosets obtained were analyzed by optical as well as scanning and transmission electron microscopy. The mechanical properties of the blends were enhanced as shown by their impact strengths, indentation, hardness, and fracture toughness analyses, whereby the toughness values were found to mainly depend on the dose. Thus, we have developed a new route for designing dual-cured toughened micro- and nanostructured transparent epoxy thermosets with enhanced fracture toughness. © 2019 by the authors.
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    Radiation-Induced Graft Immobilization (RIGI): Covalent Binding of Non-Vinyl Compounds on Polymer Membranes
    (Basel : MDPI, 2021) Schmidt, Martin; Zahn, Stefan; Gehlhaar, Florian; Prager, Andrea; Griebel, Jan; Kahnt, Axel; Knolle, Wolfgang; Konieczny, Robert; Gläser, Roger; Schulze, Agnes
    Radiation-induced graft immobilization (RIGI) is a novel method for the covalent binding of substances on polymeric materials without the use of additional chemicals. In contrast to the well-known radiation-induced graft polymerization (RIGP), RIGI can use non-vinyl compounds such as small and large functional molecules, hydrophilic polymers, or even enzymes. In a one-step electron-beam-based process, immobilization can be performed in a clean, fast, and continuous operation mode, as required for industrial applications. This study proposes a reaction mechanism using polyvinylidene fluoride (PVDF) and two small model molecules, glycine and taurine, in aqueous solution. Covalent coupling of single molecules is achieved by radical recombination and alkene addition reactions, with water radiolysis playing a crucial role in the formation of reactive solute species. Hydroxyl radicals contribute mainly to the immobilization, while solvated electrons and hydrogen radicals play a minor role. Release of fluoride is mainly induced by direct ionization of the polymer and supported by water. Hydrophobic chains attached to cations appear to enhance the covalent attachment of solutes to the polymer surface. Computational work is complemented by experimental studies, including X-ray photoelectron spectroscopy (XPS) and fluoride high-performance ion chromatography (HPIC).
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    Controlled electron-beam synthesis of transparent hydrogels for drug delivery applications
    (Basel : MDPI, 2019) Glass, Sarah; Kühnert, Mathias; Abel, Bernd; Schulze, Agnes
    In this study, we highlight hydrogels prepared by electron-beam polymerization. In general, the electron-beam-polymerized hydrogels showed improved mechanical and optical transmittances compared to the conventional UV-cured hydrogels. They were more elastic and had a higher crosslinking density. Additionally, they were transparent over a broader wavelength range. The dependence of the mechanical and optical properties of the hydrogels on the number of single differential and total irradiation doses was analyzed in detail. The hydrogels were prepared for usage as a drug delivery material with methylene blue as a drug model. In the first set of experiments, methylene blue was loaded reversibly after the hydrogel synthesis. Electron-beam-polymerized hydrogels incorporated twice as much methylene blue compared to the UV-polymerized gels. Furthermore, the release of the model drug was found to depend on the crosslinking degree of the hydrogels. In addition, electron-beam polymerization enabled the irreversible binding of the drug molecules if they were mixed with monomers before polymerization.
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    An electron beam profile instrument based on FBGs
    (Basel : MDPI AG, 2014) Sporea, D.; Stǎncǎlie, A.; Becherescu, N.; Becker, M.; Rothhardt, M.
    Along with the dose rate and the total irradiation dose measurements, the knowledge of the beam localization and the beam profile/energy distribution in the beam are parameters of interest for charged particle accelerator installations when they are used in scientific investigations, industrial applications or medical treatments. The transverse profile of the beam, its position, its centroid location, and its focus or flatness depend on the instrument operating conditions or on the beam exit setup. Proof-of-concept of a new type of charged particle beam diagnostics based on fiber Bragg gratings (FBGs) was demonstrated. Its operating principle relies on the measurement of the peak wavelength changes for an array of FBG sensors as function of the temperature following the exposure to an electron beam. Periodically, the sensor irradiation is stopped and the FBG are force cooled to a reference temperature with which the temperature influencing each sensor during beam exposure is compared. Commercially available FBGs, and FBGs written in radiation resistant optical fibers, were tested under electron beam irradiation in order to study their possible use in this application.
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    Cold atmospheric pressure plasma and low energy electron beam as alternative nonthermal decontamination technologies for dry food surfaces: A review
    (Amsterdam [u.a.] : Elsevier Science, 2018) Hertwig, Christian; Meneses, Nicolas; Mathys, Alexander
    Background: Dry food products are often highly contaminated, and dry stress-resistant microorganisms, such as certain types of Salmonella and bacterial spores, can be still viable and multiply if the product is incorporated into high moisture food products or rehydrated. Traditional technologies for the decontamination of these products have certain limitations and drawbacks, such as alterations of product quality, environmental impacts, carcinogenic potential and/or lower consumer acceptance. Cold atmospheric pressure plasma (CAPP) and low energy electron beam (LEEB) are two promising innovative technologies for microbial inactivation on dry food surfaces, which have shown potential to solve these certain limitations. Scope and approach: This review critically summarizes recent studies on the decontamination of dry food surfaces by CAPP and LEEB. Furthermore, proposed inactivation mechanisms, product-process interactions, current limitations and upscaling potential, as well as future trends and research needs for both emerging technologies, are discussed. Key findings and conclusions: CAPP and LEEB are nonthermal technologies with a high potential for the gentle decontamination of dry food surfaces. Both technologies have similarities in their inactivation mechanisms. Due to the limited penetration depth of both technologies, product-process interactions can be minimized by maintaining product quality. A first demonstrator with Technology Readiness Level (TRL) 7 for LEEB has already been introduced into the food industry for the decontamination of herbs and spices. Compared with LEEB, CAPP is at the advanced development stage with TRL 5, for which further work is essential to design systems that are scalable to industrial requirements. © 2018 The Authors