The Influence of the Structural Architecture on the Swelling Kinetics and the Network Behavior of Sodium-Alginate-Based Hydrogels Cross-Linked with Ionizing Radiation.

The present work discusses the influence of the structural architecture of sodium alginate-co-acrylic acid-poly(ethylene) oxide hydrogels, crosslinked through electron beam (e-beam) radiation processing. The most important properties of the hydrogels were studied in detail to identify a correlation between the architecture of the hydrogels and their properties. Furthermore, the effect of sodium alginate (NaAlg) concentration, the amounts of the polymer blend, and the size of the samples on hydrogel properties were investigated. The results show that the hydrogels cross-linked (0.5% and 1% NaAlg) with 12.5 kGy exhibit improved physicochemical properties. High gel fraction levels (exceeding 83.5-93.7%) were achieved. Smaller hydrogel diameter (7 mm) contributed to a maximum swelling rate and degree of 20.440%. The hydrogel network was dependent on the hydrogels' diameter and the amount of polymer blend used. The hydrogels best suited the first-order rate constants and exhibited a non-Fickian diffusion character with diffusion exponent values greater than 0.5. This study indicates that the cross-linked hydrogel has good properties, particularly because of its high degree of swelling and extensive stability (more than 180 h) in water. These findings show that hydrogels can be effectively applied to the purification of water contaminated with metals, dyes, or even pharmaceuticals, as well as materials with a gradual release of bioactive chemicals and water retention.

Water Absorption Kinetics in Composites Degraded by the Radiation Technique.

Rubber-based wastes represent challenges facing the global community. Human health protection and preservation of environmental quality are strong reasons to find more efficient methods to induce degradation of latex/rubber products in order to replace devulcanization, incineration, or simply storage, and electron beam irradiation is a promising method that can be can be taken into account. Polymeric composites based on natural rubber and plasticized starch in amounts of 10 to 50 phr, obtained by benzoyl peroxide cross-linking, were subjected to 5.5 MeV electron beam irradiation in order to induce degradation, in the dose range of 150 to 450 kGy. A qualitative study was conducted on the kinetics of water absorption in these composites in order to appreciate their degradation degree. The percentages of equilibrium sorption and mass loss after equilibrium sorption were found to be dependent on irradiation dose and amount of plasticized starch. The mechanism of water transport in composites was studied not only through the specific absorption and diffusion parameters but also by the evaluation of the diffusion, intrinsic diffusion, permeation, and absorption coefficients.

Radiation Processing and Characterization of Some Ethylene-propylene-diene Terpolymer/Butyl (Halobutyl) Rubber/Nanosilica Composites.

Composites based on ethylene-propylene-diene terpolymer (EPDM), butyl/halobutyl rubber and nanosilica were prepared by melt mixing and subjected to different doses of electron beam irradiation. The effect of irradiation dose on the mechanical properties, morphology, glass transition temperature, thermal stability and water uptake was investigated. The efficiency of the crosslinking by electron beam irradiation was analyzed by Charlesby-Pinner parameter evaluation and crosslink density measurements. The scanning electron microscopy data showed a good dispersion of nanosilica in the rubber matrix. An improvement in hardness and 100% modulus was revealed by increasing irradiation dose up to 150 kGy. The interaction between polymer matrix and nanosilica was analyzed using the Kraus equation. Additionally, these results indicated that the mechanical properties, surface characteristics, and water uptake were dependent on crosslink characteristics.

New Materials Based on Ethylene Propylene DieneTerpolymerand Hemp Fibers Obtained by Green Reactive Processing.

The paper presents the obtaining of new green polymeric composites using a sustainable reactive processing method, namely electron beam irradiation. EPDM rubber mixtures were reinforced with different amounts of short hemp fibers, which were then irradiated at doses between 75 and 600 kGy. The samples were analyzed by determination of physical-mechanical properties, sol-gel analysis, crosslink density (using the well-known modified Flory-Rehner equation for tetra functional networks), determination of rubber-fiber interactions (using the Kraus equation), water uptake test and FTIR analysis. The obtained results indicate an improvement of the hardness, the tensile and tear strength as the quantity of hemp fibers increases. As the irradiation dose increases, there is an increase in the degree of crosslinking and the gel fraction. Analyzing the behavior of the irradiation samples using the Charlesby-Pinner equation, it is observed that all the samples tend to crosslink by irradiation, the share of degradation reactions being low. For these reasons, the new materials can be used in the food, pharmaceutical or medical field, because the obtained products are sterile and can be easily resterilized by irradiation. They have high elasticity values and can be used to make packaging, seals and other consumer goods.

Combined microwave and electron beam exposure facilities for medical studies and applications.

The paper presents two radiation exposure facilities (REFs) which permit separate and simultaneous irradiation with microwaves (MW) of 2.45 GHz and electron beams (EB) of 6.23 MeV for malignant melanoma (MM) cell investigations, in vitro (MW+EB-REF-vitro) and in vivo (MW+EB-REF-vivo). The REFs are specifically designed for the following medical studies: 1) The effects of separate and combined (successive and simultaneous) MW and EB irradiation on the B16F10 mouse--MM cell cultures without/with drugs incubation, 2) The effects of separate and combined MW and EB irradiation on human blood components irradiated in samples of integral blood from healthy donors and from donors with MM; 3) The effects of separate and combined MW and EB whole body irradiation on the C57 BL/6 mice bearing MM without/with drugs administration. Several representative results obtained by experiments with REFs in vitro and in vivo are discussed. The most important conclusion of the experimental results is that low dose-total body MW+EB irradiation combined with drugs administration could present a valuable potential for an advanced study in malignant melanoma therapy.

Cell investigations simultaneously with exposure to 2.45 GHz microwaves.

The paper presents two microwave (MW) exposure systems (MWESs) that permit observations and measurements on cell cultures during their exposure to MW of 2.45 GHz: MWES-1 and MWES-2. MWES-1 is designed for the measurement of the cell membrane fluorescence anisotropies (MFA) simultaneously with MW exposure. MWES-2 is designed for the cells culture exploration under an inverted microscope before, during and after MW exposure. MWES-1 consists mainly of a 2.45 GHz microwave generator (MWG-2.45 GHz-SAIREM) of 0-25 W, equipped with forward power and reflected power displaying, and an adjustable coaxial antenna immersed directly into the cuvette with the cells-suspension of a Spex type spectrofluorometer. The MW effect on membrane fluidity of B16F10 malignant melanoma (B16F10-MM) cells in suspension were investigated with MWES-1, by MFA measurements. We observed a MW induced transition temperature (ITT) rising strongly during the MW exposure as compared with ITT obtained by classical heating (CH). The MWES-2 consists of the MWG-2.45 GHz-SAIREM generator and a rectangular waveguide applicator with traveling wave placed between the condenser and the objective of a Zeiss Axiovert 200 microscope, equipped with a fluorescence device and image acquisition. The MW effects on shape and apoptosis of the B16F10-MM cells were investigate with MWES-2. The B16F10-MM cells exhibited visible shape changes during MW exposure up to 37 degrees C. The MW exposure induced cells apoptosis/necrosis in several seconds after that MW are applied, beginning with SAR = 1.5 W/sample, compared to CH controls exposed at the same temperature dynamics.

Vaccine preparation by radiation processing.

A new radiation biotechnology for the acquirement of a commercial vaccine, designed for prophylaxis of ruminant infectious pododermatitis (IP), produced by gram negative bacteria Fusobacterium necrophorum (F.n.), is presented. Two different processes for preparing F.n. vaccine are used: a) the inactivation of F.n. bacteria exotoxins by microwave (MW) or/and electron beams (EB) irradiation; b) the isolation of exotoxins from F.n. cultures irradiated with MW or/and EB and the inactivation of isolated F.n. exotoxins with formalin. The EB irradiation of F.n. cultures produced simultaneously with the cells viability decrease an increasing of exotoxin quantity released in the culture supranatant as compared with classical methods. The MW irradiation is able to reduce the cells viability to zero but without an increase of exotoxin quantity in cultures supranatant. Instead of this MW irradiation, for certain conditions, is able to induce an important stimulation degree of the F.n. proliferation in cultures, from two to three log10. Two vaccine types were prepared: A1 vaccine that contains whole cell culture irradiated with MW/EB and A2 vaccine that contains cell-free culture supernatant of an MW/EB irradiated F.n. strain producing exotoxins. Also, other two vaccines are prepared: B1 and B2 that contain the same materials as A1 and A2 respectively, but without using MW/EB exposure. The vaccine efficiency is tested in ruminant farms in which IP evolves. It is expected that this new vaccine to offer a better protection, more than 60%, which is the best presently obtained result in ruminant farms.