Irradiated EVA Research Articles

Monitoring of Peroxide in Gamma Irradiated EVA Multilayer Film Using Methionine Probe.

In this study, the oxidation of methionine is used as a proxy to model the gamma radiation-induced changes in single-use bags; these changes lead to the formation of acids, radicals, and hydroperoxides. The mechanisms of formation of these reactive species and of methionine oxidation are discussed. With the help of reaction kinetics, the optimal conditions for the use of these single-use bags minimizing the impact of radical chemistry are highlighted. Biopharmaceutical bags gamma irradiated from 0 kGy to 260 kGy and aged from 0 to 36 months were filled with a methionine solution to follow the oxidation of the methionine. The methionine sulfoxide was measured with HPLC after different storage times (0, 3, 10, 14, 17, and 21 days). Three main results were analyzed through a design of experiments: the oxidative induction time, the methionine sulfoxide formation rate, and the maximum methionine sulfoxide concentration detected. A key aspect of the study is that it highlights that methionine is oxidized not necessarily directly by hydro(gen) peroxide but throughperacid, and likely peracetic acid. The answers to the design of experiments were considered to obtain the desirability domain for the optimization of the conditions of use for the single-use bags limiting the oxidation of methionine as well as the release of reactive species thereof.

Effect of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of intumescent flame retardant ethylene-vinyl acetate copolymer

Ethylene vinyl acetate copolymer (EVA) flame retarded by ammonium polyphosphate (APP) and pentaerythritol (PER) was cross-linked by electron beam irradiation. The effects of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of EVA composites were investigated. The volatilized products of EVA/APP/PER composites were characterized by thermogravimetric analysis/infrared spectrometry. As VA content increased, the volatilized products increased in the second decomposition step, but decreased in the third decomposition step. For all samples, the increase of irradiation dose could improve both the gel content and the Limit Oxygen Index (LOI, the minimum oxygen concentration by volume for maintaining the burning of a material) values of irradiated composites. The mechanical and thermal properties of the irradiated EVA composites were also evidently improved at appropriate irradiation dose as compared with those of unirradiated EVA composites, whereas these properties decrease at higher irradiation dose because of the electron beam irradiation-induced oxidative degradation or chain scission.

Enhancement on physical properties of flame retarded ethylene-vinyl acetate copolymer/ferric pyrophosphate composites through electron beam irradiation

Ferric pyrophosphate (FePP) with silica-gel microencapsulated ammonium polyphosphate (MCAPP) and char forming agent (CFA) in the flame retardation of ethylene-vinyl acetate copolymer has been studied through LOI and UL-94 test. The UL-94 data show that EVA with 20wt.% IFR only has V-2 rating. However, with the addition of 1wt.% FePP and 19wt.% IFR, it can reach V-0 rating. The properties of the composites before and after the electron beam irradiation are compared. The volume resistivity, mechanical and thermal properties of the irradiated EVA composites are also evidently improved at appropriate irradiation dose as compared with those of un-irradiated ones. The tensile strength of EVA/IFR/FePP composites with 160kGy irradiation is 21.8Mpa, which is much higher than that of un-irradiated one (12.7MPa). Furthermore, the thermal aged test and water resistance test results demonstrate that EVA/IFR/FePP composites have good thermal aging property and water durability.

Effect of electron beam irradiation on the mechanical and thermal properties of intumescent flame retarded ethylene-vinyl acetate copolymer/organically modified montmorillonite nanocomposites

Ethylene-vinyl acetate copolymer (EVA) flame retarded by a combination of intumescent flame retardants (IFR) and organically modified montmorillonite (OMMT) have been crosslinked by high-energy electron beam irradiation. The structure was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of electron beam irradiation on the thermal, mechanical and dynamic mechanical properties of the irradiated EVA nanocomposites were investigated. The XRD and TEM results demonstrated that the OMMT was well dispersed in the EVA nanocomposites. The LOI and UL-94 results showed that a synergistic effect on the flame retardancy of EVA nanocomposite existed between the IFR and OMMT. With the addition of 1 wt% OMMT and 24 wt% IFR, the LOI value of EVA/IFR/OMMT nanocomposite increased from 30.5 % to 33.5 %. The mechanical properties of the irradiated EVA nanocomposite were evidently improved at 160 kGy dosage with the increase in the tensile strength to 18.5 MPa. Thermal oxidative degradation of the flame-retardant EVA/IFR/OMMT nanocomposites was characterized by thermogravimetric analysis/infrared spectrometry (TG–IR) and real-time Fourier transformed infrared spectroscopy (RT-FTIR).

Effect of irradiation on mechanical and structural properties of ethylene vinyl acetate copolymers hollow fibers

AbstractEffect of irradiation on mechanical and structural properties of ethylene vinyl acetate copolymers (EVA) hollow fibers was studied by the tests such as determination of gel content, density, tensile, FTIR, SEM, and DMA. These effects were discussed based on dose and irradiation environment. The results of gel content depicted that irradiated EVA in ambient conditions had tendency to chain scission while the crosslinking overcame in irradiated samples under nitrogen. Density insignificantly enhanced with irradiation dose. In tensile test, irradiation induced increase in tensile strength and decrease in elongation at break (especially in samples irradiated in nitrogen). Also, changing in layer orientation could be observed by SEM images. In addition, irradiation caused altering peak intensity in FTIR spectrum. DMA results demonstrated that irradiation broaden the elastic zone. Totally, irradiation enhances features especially in irradiated EVA18 in nitrogen. Since, according to stabilization of induced deformation and improvement of mechanical properties (that created by radiation), the irradiated samples can be used in different applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Approaches to the Flame Retardancy of Polymers. I.: Electron-Beam Pre-Irradiation and Grafting of Acrylic Monomers onto EVA Copolymers

An attempt has been made in the paper to impart flame retar dancy to polymers with grafting induced by the electron-beam (EB) pre- irradiation technique. Based on EVA copolymers with different VA contents (%), the authors have tried to use EB pre-irradiation under atmosphere fol lowed by grafting with/without subsequent saponification expediting the char ring of polymers upon heating. Characterization of the flammability of the irra diated EVA copolymers grafted with acrylic monomers (MAA, AA, and AAm) indicates that this approach turns out to be promising and worth pursuing in research and/or in applications.

Structural analysis of electron beam irradiated ethylene‐vinyl acetate copolymer (EVA) film (II)

AbstractThe crosslinked structure of irradiated ethylene‐vinyl acetate copolymer (EVA) film was examined by means of ESR, IR and pyrolysis‐gas chromatography. The ESR spectrum of 35 Mrad irradiated EVA film with 95g kg−1 vinyl acetate content consisted of a three‐line component with an intensity ratio of 1:2:1, a hyperfine structure coupling of 22.4 G and g factor of 2.0049. Therefore, the spectrum was assigned to the methylene radical with two α protons on the same plane; this radical is formed by loss of a hydrogen atom from the acetoxymethyl group.In pyrolysing EVA films at 500°C, the yield of acetic acid from 10 Mrad‐150 g kg−1 film significantly decreased compared with that of unirradiated film, and it decreased with increasing crosslinking density.By measuring the IR spectra of methanolysed EVA films, the following results were obtained: the absorbances at 1740, 1250 and 1050cm−1, attributed to the CO, OCOR and COC groups, respectively, had a marked decrease, whereas the three peaks for 20Mrad film were much stronger than those of unirradiated film. On the basis of these findings, it is suggested that the crosslinking reaction in electron beam irradiated EVA film with lower doses takes place between the acetoxy groups and the main chains.

Sorption of volatile compounds into electron beam irradiated EVA film in the vapour phase

AbstractIn order to investigate the sorption of volatile compounds by electron beam irradiated ethylene/vinyl acetate copolymer (EVA) films, permeation measurements in the vapour phase were carried out. The diffusion coefficients of octane, ethyl hexanoate, octanal, octan‐1‐ol and d‐limonene increased with an increase in the irradiation dose. The sorption of all volatile compounds in this study was depressed in electron beam irradiated film: the decreases in solubility coefficients for 20 Mrad EVA film were 15% for octane and ethyl hexanoate, 45% for octan‐1‐ol and octanal, and 50% for d‐limonene. The enthalpy change in sorption (ΔH) of ethyl hexanoate was −13·4 kJ mol−1 for 50 g kg−1 EVA film at a dose of 20 Mrad compared with −27·6 kJ mol−1 for the unirradiated one. In a homologous series of aliphatic alcohols, sorption was significantly depressed with increasing carbon chain length. Judging from both heat‐seal strength and sorption behaviours, the most appropriate irradiation dose for the practical usage of irradiated EVA film was less than 15, 10 and 5 Mrad for 50, 95 and 150 g kg−1 EVA film, respectively.