Comparison of γ-radiation and electron beam irradiation effects on gelatin

Gelatin is a heterogeneous mixture of water-soluble proteins of high average molecular weight derived by hydrolytic action from collagen, a protein of mammal external protective tissues. There are many characteristics of a material that can indicate its quality or performance in its intended use. The knowledge of a material's rheological characteristics is valuable to predict its pourability, its performance in a dipping or coating operation or the ease with which it may be handled, processed or used. In this work bovine powder gelatin was submitted to γ-radiation from a ⁶⁰Co source, dose rate about 7 kGy/h and to electron beam irradiation, dose rate about 11 kGy/s. The doses applied were 5, 10, 20 and 50 kGy. The radiation effects were measured following viscosity changes at 40°C of gelatin powder 10% aqueous solutions. The relationship between the decrease in viscosity of gelatin solutions and radiation dose presented close comparable values for both irradiation processes.     

The influence of radiation sterilization on thiamphenicol

The effect of ionising radiation, applied in the form of an electron beam, in the doses of 25, 100 and 400 kGy on the physical and chemical properties of thiamphenicol in solid phase has been studied by organoleptic analysis (form, colour, smell, solubility, clarity) and spectroscopic methods (UV, IR, EPR), chromatography (TLC), SEM observations, X-ray diffraction, polarimetry and thermal method (DSC). The above-discussed results have proved that on irradiation with a dose of 25 kGy no significant changes appear in thiamphenicol, apart from the formation of free radicals of the lifetime of over 352 days. On irradiation with much higher doses (100 and 400 kGy) no changes were observed in the IR spectra but the UV line intensities slightly increased at lambda(max)=266 and 273 nm, the colour of the powder changed, the radiolysis products appeared as detected by TLC, changes were also observed in the XRD, SEM pictures, the melting point values (DSC) and optical rotation. On the basis of DSC results a linear relation was found between the irradiation dose and the decrease in the melting point and increase in the enthalpy of melting, characterised by high correlation coefficients of r=0.9839 and 0.9622, respectively. Moreover, a linear relation was established between the optical rotation angle and the irradiation dose, alpha(D) ( degrees )=f(dose), characterised by the correlation coefficient r=0.9874. The results obtained indicate that thiamphenicol can be safely subjected to radiation sterilization by the standard dose of 25 kGy.     

Advancements in accuracy of the alanine dosimetry system. Part 2. The influence of the irradiation temperature

Systematic measurements of the temperature coefficient for alanine electron paramagnetic resonance (EPR) response have been performed for irradiation in the temperature range (10–50)°C and in the absorbed dose range (1–100) kGy at the dose rate 9.5 kGy/h. During the ⁶⁰Co-ray irradiation, -l-alanine dosimeters were kept in a sealed aluminum holder that provided an effective heat exchange with the temperature-controlled environment. The time between the irradiation and signal measurements was standardized, and a reference sample fixed in the resonant cavity was used to correct the signals for small variations in the spectrometer sensitivity. The temperature coefficient for each dose was determined from approximately 30 experimental points processed by the weighted least-squares technique after the necessary statistical tests were done. The temperature coefficients thus determined were considerably lower than previously reported. The dose dependence of the temperature coefficient features a minimum at (20–30) kGy (about 0.135%/K) with higher values at 1 kGy (0.17%/K) and at 100 kGy ((0.175–0.19) %/K). With the exception of very high doses, no significant distinction was found between the temperature coefficients of Bruker and NIST dosimeters, which differ in shape and binder content.     

The effect of gamma irradiation on mechanical, and thermal properties of recycling polyethylene terephthalate and low density polyethylene (R-PET/LDPE) blend compatibilized by ethylene vinyl acetate (EVA)

A study has been made on the compatibility of recycled polyethylene terephthalate (R-PET) and low density polyethylene (LDPE) blend in the presence of ethylene vinyl acetate (EVA) as a compatibilizing agent prepared by extrusion hot stretching process. EVA content in the blend as a compatibilizing agent was an enhancement effect on radiation crosslinking of R-PET/EVA/LDPE blends and the highest radiation crosslinking was obtained when the EVA content was reached at 10 % EVA when irradiated by gamma irradiation. Blends containing different (EVA) ratios were irradiated to different doses of gamma irradiation 25, 50 and 100 kGy. The effect of the compatibilizer and radiation on mechanical, thermal properties of R-PET together with LDPE and morphology has been investigated. It was found that gamma irradiation together with the presence of compatibilizing agent (EVA) has positive effect on the mechanical and thermal properties of R-PET/LDPE blend. The structural properties of R-PET/LDPE modified by gamma irradiation and EVA as compatibilizing agent was examined by SEM. Also, it was found that the optimum concentration of EVA and gamma irradiation dose was found to be 10 % EVA and 100 kGy, respectively.     

Thermal study of four irradiated imidazoline derivatives in solid state

Four imidazoline derivatives: antazoline (AN), naphazoline (NN), tymazoline (TM), xylometazoline (XM), in the form of hydrochlorides in solid phase have been subjected to high energy e-beam irradiation from an accelerator (~10 MeV) at a dose varied from 25 to 200 kGy. The effects of the irradiation have been assessed by DSC, X-ray diffraction, FTIR, EPR and TLC. The standard sterilisation dose of 25 kGy has been found to produce changes in the properties of one derivative (XM), two other ones (AN and TM) have been found sensitive to doses >100 kGy, whereas NN has been resistant to irradiation in the whole range studied (25–200 kGy). EPR results indicated that the changes taking place in the therapeutic substances studied are related to radical formation. The irradiation induced changes in colour, a decrease or increase in the melting point, changes in the XRD pattern, small changes in the shape of FTIR peaks and the presence of radiolysis products. The XM compounds cannot be sterilised by irradiation because of the radiation induced changes in its physico-chemical properties.     

Thermal and spectroscopic analysis of florfenicol irradiated in the solid-state

The study has been undertaken to check the effect of ionising radiation on the physical and chemical properties of florfenicol, an antibiotic of a wide range of antibacterial activity. The solid-state samples were subjected to an electron beam generated by accelerator corresponding to the doses of 25, 100 and 400 kGy, and the effect of the exposure was analysed by the methods not requiring changes in the state (with no preliminary treatment), such as SEM, DSC, FTIR, XRD, EPR and HPLC. Florfenicol irradiated with a dose of 25 kGy has not changed the form or colour, however, a small increase in intensity of some absorption bands in the FTIR spectrum and of some peaks in the XRD pattern, a decrease in the melting point by 0.6°C, the appearance of free radicals and a loss in the FF content within the error of the method (0.91%) have been observed. After irradiation with greater doses (100 and 400 kGy) the changes have intensified, yellow discolouration appeared and the loss of FF content has increased to 6.39%. As follows from the results, the compound studied in solid-state undergoes radiolysis after e-beam irradiation in the doses ≥25 kGy, but lower doses (15–20 kGy) can be applied for its decontamination or sterilization with no adverse effect on its physico-chemical properties.     

Comparative study of effect of low and medium dose rate of γ irradiation on microporous polysulfone membrane using spectroscopic and imaging techniques

The effect of low (LDR) and medium dose rate (MDR) of γ irradiation at low doses (0-100 kGy) on the structural and chemical changes of microporous polysulfone (PSf) membrane has been studied using UV-vis, FTIR, SEM and dead-end filtration techniques. PSf membrane was cast by phase inversion method. Irradiation was done at room temperature in air media. The doses chosen were 0-100 kGy for LDR and 0-50 kGy for MDR; they were below and above sterilization dose. Analysis of UV-vis and IR spectra and SEM images obtained suggested that chain scissions and crosslink had occurred simultaneously in the irradiated membranes in both cases. This radio-oxidation effects observed start at a very low dose i.e. 1.66 kGy and increase with increase in dose. It is supported by the flux values obtained; it is increased with increase in dose. The results indicate that a very low dose γ irradiation was able to change the physicochemical characteristics of microporous PSf membrane which depend on dose rate of exposure.     

Effect of Electron Beam Irradiation on the Properties of High Styrene Rubber/Styrene Butadiene Rubber Blends

High styrene rubber (HSR)/styrene butadiene rubber (SBR) blends at different ratios were exposed to various doses of electron beam irradiation. The effect of irradiation dose and blend ratios on the mechanical properties and shape memory characteristics in terms of strain fixation) rate (R_f) and strain recovery rate (R_r) was investigated. The results revealed that rich styrene blends displayed higher tensile strength and hardness than low styrene content blends at all irradiation doses. However, elongation at break, and toughness were lower for rich styrene content. Also, it was observed that for most specimens, the tensile strength, elongation at break and hardness increases up to100 kGy. Increasing irradiation doses resulted in slight deterioration in some mechanical properties only for low styrene content at150 kGy. According to the normalized tensile stress at 25% elongation, it was found that the contribution of irradiation in enhancing the mechanical properties is higher for rich butadiene blends. On the other hand, it was observed that rich styrene content blends possess higher R_f and R_r at all the irradiation doses and stretching temperatures. However, the increase of irradiation dose decreases R_f values; the extent of this decrease depends on the blend ratios. Conversely, for all blends, R_r were increased by increasing irradiation dose and styrene content ratios.     

Thermal analysis in evaluation of the radiochemical stability of some fungicidal drugs

Four azole derivatives showing antimycotic activity (Miconazole, Ketoconazole, Clotrimazole, Fluconazole) in solid phase were exposed to beta irradiation at the dose of 20-200 kGy and then alterations in the physicochemical properties of the above derivatives were studied using the methods: scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. It was found that the compounds irradiated with sterilising doses (20-50 kGy) showed no significant alterations in their physicochemical properties, while application of doses >50 kGy resulted in small changes in the X-ray diffraction patterns and in the course of DSC curves, including a decrease in the melting points and enthalpy of the process. For Miconazole and Fluconazole, a linear and relatively strong correlation was found (from r =0.9782 to r =0.9003) between the size of the dose of irradiation and the decrease in the melting point and enthalpy value. This revised version was published online in July 2006 with corrections to the Cover Date.     

Radiation-induced crosslinking of collagen gelatin into a stable hydrogel

Gelatin, the low molecular weight collagen derivative from porcine skin was transformed into a stable permanent hydrogel by γ-radiation. A series of samples with 3% gelatin solution in water were irradiated at doses of 12, 25, 50, 100, 150, 200 kGy at room temperature in the absence of air with a dose rate of 2.2 kGy/h. At low dose gelatin hydrogels incorporating all the available water were obtained. At higher doses above 50 kGy, the gelatin hydrogel samples show a curious shrinking phenomenon due to the relatively high crosslinking density level achieved, so part of the available water is squeezed out from the gel cage. The gelatin hydrogel samples were studied by mass fractionation analysis, by spectrophotometric and polarimetric analysis. Further characterization was made by FT-IR spectroscopy and by thermal analysis (DSC, DTA and TGA) of the dried gelatin samples after irradiation in comparison to a reference untreated sample.     

Gamma radiation curing of nitrile rubber/high density polyethylene blends

Nitrile butadiene rubber (NBR) was mixed with high density polyethylene (HDPE) thermoplastics with different ratio namely (100/20), (100/40), (100/60) and (100/80). The obtained blends were subjected to gamma irradiation with varying dose from 50 to 250 kGy. The induced crosslinking and hence the improvement in the different properties were followed up as a function of irradiation dose. Mechanical properties as tensile strength, tensile modulus at 50 % elongation, elongation at break percent, permanent set and hardness were carried out as a function of irradiation dose and blend ratio. Moreover, physical properties namely, gel fraction % and swelling number were found to improve with the increase of irradiation dose up to 250 kGy and with the increase of the content of HDPE in blend. Moreover, presence of NBR enhances the shrinking properties of the obtained blend which can be used as a good heat shrinkable material.     

Effect of electron beam irradiation on dynamic mechanical,thermal and morphological properties of LLDPE and PDMS rubber blends

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and poly dimethyl siloxane rubber (PDMS) prepared over a wide range of compositions starting from 70:30 to 30:70 (LLDPE: PDMS) by varying the radiation doses from 50 to 300 kGy has been studied. The dynamic modulii and dielectric strength of the blends increase on irradiation at 100 kGy as compared to that for the unirradiated blends. Degree of crystallinity and melting behaviour remain unchanged upon irradiation upto a dose of 100 kGy, beyond which it decreases. Thermal stability increases with increase in the proportion of PDMS rubber in the blend as well as on irradiation at 100 kGy. The phase morphology of the blends examined under the SEM exhibit two phase morphology before electron beam irradiation, whereas single phase morphology is observed after electron beam irradiation due to intra- as well as inter-molecular crosslinking leading to a miscible system.     

Poly(N-vinylpyrrolidone) hydrogels: 1.Radiation polymerization and crosslinking of N-vinylpyrrolidone

POLY(N-VINYLPYRROLIDONE) HYDROGELS: 1 RADIATION POLYMERIZATION AND CROSSLINKING OF N-VINYLPYRROLIDONE). The effects of irradiation dose on the conversion of vinylpyrrolidone (VP) with various concentration and other characteristics such as Gelation Dose (Dg), Degree of Swelling (DS) and Equilibrium Water Content (EWC) have been investigated. Aqueous solution of vinylpyrrolidone with several concentrations such as 5, 10, 20, 40, 60, 80 and 100 Wt % were irradiated by using gamma rays of Cobalt-60 source with a dose rate of 0. 139 Gy/s. After irradiation, parameters such as conversion of vinylpyrrolidone, gelation dose, degree of swelling, and equilibrium water content were analyzed. Results show that the conversion of VP to PVP was almost 100% at a dose of 2 kGy. The gelation dose of PVP depends on initial content of monomer. Degree of swelling of gels with concentration of 10 % was 55 at the dose of 10 kGy and 30 at the dose of 40 kGy. The lowest value of degree of swelling is 15. At the range of irradiation dose of 10 to 40 kGy the EWC of gel was found to be 98 to 94 %.     

Gamma irradiation improves the antioxidant activity of Aloe vera (Aloe barbadensis miller) extracts

Aloe has been widely used in food products, pharmaceuticals, and cosmetics because of its aromatic and therapeutic properties. In the present study, the ethanolic extracts of aloe gel were gamma-irradiated from 10 to 100 kGy. After gamma irradiation, the color of the ethanolic extracts of aloe gel changed to red; this color persisted up to 40 kGy but disappeared above 50 kGy. Liquid chromatography/mass spectrometry analysis demonstrated the production of a new, unknown compound (m/z=132) after gamma irradiation of the ethanolic extracts of aloe gel. The amount of this unknown compound increased with increasing irradiation up to 80 kGy, and it was degraded at 100 kGy. Interestingly, it was found that gamma irradiation significantly increased the antioxidant activity, as measured by the 1,1-diphenyl-2-picrylhydrazyl-radical scavenging capacity. The antioxidant activity of aloe extract was dramatically increased from 53.9% in the non-irradiated sample to 92.8% in the sample irradiated at 40 kGy. This strong antioxidant activity was retained even at 100 kGy. These results indicate that gamma irradiation of aloe extract can enhance its antioxidant activity through the formation of a new compound. Based on these results, increased antioxidant activity of aloe extracts by gamma rays can be applied to various industries, especially cosmetics, foodstuffs, and pharmaceuticals.     

High-velocity (detonation-like) traveling wave regime of cryocopolymerization of acetaldehyde with hydrogen cyanide

The effect of initiation conditions on the self-sustained-wave regime of copolymerization of acetaldehyde with hydrogen cyanide has been studied. The local brittle failure in the bottom of the sample makes it possible to implement the high-velocity (detonation-like) traveling wave regime of copolymerization. The velocity of propagation of the reaction wave front achieves 1870 mm/s at an irradiation dose of 55 kGy. However, the copolymer formed in the course of preliminary irradiation at 77 K changes the properties of the solid matrix of the reagents and, at high irradiation doses, the high-velocity traveling wave regime of copolymerization degenerates. The velocity of propagation of the copolymerization wave decreases, and, at an irradiation dose of 200 kGy, it is as low as 50 mm/s. The same velocity of propagation is observed when the reaction is initiated by the brittle failure in the top of the sample.     

Radiation aging and chemi-crystallization processes in polyoxymethylene

The radiochemical degradation of a polyoxymethylene homopolymer (POM) was used to study the effects of molar mass changes in the crystalline structure. The dose rate was 20 kGy h⁻¹ with doses of up to 30 kGy used. Both WAXS and SAXS were used to analyse the structures. Results showed that, under irradiation, the polymer undergoes random chain scission. The radiochemical yield was found to be G = 1.6 chain scission events per 100 eV. It was found that no crosslinking occurs and that only one chain scission mechanism, leading to the formation of formate groups, operates. Proof for the existence of chemi-crystallization is evidenced by (i) an increase in the crystallinity ratio as well as (ii) a decrease in the amorphous layer thickness. Simple models, derived from Rault’s theory, are used to predict both (i) and (ii) from molar mass values.     

Physicochemical and sensory properties of irradiated dry-cured ham

To determine the effect of different irradiation doses on ready-to-eat (RTE) dry-cured shoulder hams, physicochemical and sensory attributes were analyzed during 8 weeks of refrigerated storage. The results show that irradiation reduced the redness value and increased the 2-thiobarbituric acid-reactive substance (TBARS) value as well as the irradiation aroma during storage. However, ham samples irradiated with 2.5 and 5.0 kGy did not show significant changes in lightness values compared to the control sample during 8 weeks of storage. TBARS values were lower in the sample irradiated with 2.5 kGy than in the other irradiated samples. The total plate counts of the 5.0 kGy-irradiated samples were not measured after 0 weeks. Sensory panels found that the 2.5- and 5.0 kGy-irradiated samples had better overall acceptability scores than the other irradiated samples. It was concluded that treatments with lower levels of irradiation (≤5.0 kGy) can enhance the microbial safety and sensory acceptance of dry-cured shoulder hams.     

Co γ-ray irradiation effect and degradation behaviors of a carbon nanotube and poly(ethylene-co-vinyl acetate) nanocomposites

This paper describes the process of manufacturing a new nanocomposite material, which involves adding a carbon nanotube (CNT) to improve EVA's physical characteristics such as weak radiation resistance and thermal properties. We irradiated the prepared samples with doses of 50 kGy, 100 kGy and 200 kGy at a dose rate of 5 kGy/h and examined their thermogravimetric characteristics, activation energy, degradation progress, and CNT dispersion using a thermogravimetric analyzer (TGA), chemiluminescence (CL), and a field emission scanning electron microscope (FESEM). Experimental results indicated that the samples with a CNT had higher DTG 2nd peak temperatures than those without a CNT. Activation energy of the samples reduced as the irradiation dose and the CNT content increased. In the second CL experiment, the CL intensity rapidly declined as the temperature, irradiation dose and the CNT content increased. Finally, examination of the fracture surfaces in the FESEM experiment indicated that the lamella structure of the EVA changed as the irradiation dose increased. We were also able to observe that samples with a CNT were aggregated and dispersed in numerous lumps.     

Spectroscopic analysis of pindolol irradiated in the solid state

Pindolol ((2RS)-(1-(1H-indol-4-iloxy)-3- [(1-metyloetylo)amino]-2-propanol) in substantia was exposed to ionising radiation emitted by high energy electrons from an accelerator, in the standard sterilisation dose of 25 kGy and in higher doses from the range 50–400 kGy. The effects of irradiation were checked by spectrometric methods (UV, MS, FT-IR, EPR) and hyphenated methods (HPLC-MS) and the results were referred to those obtained for non-irradiated sample. EPR results indicated the presence of free radicals in irradiated samples, in the amount of 1.36 × 10¹⁶ spin g^?1 for 25 kGy and 3.70×10¹⁶ spin g^?1 for 400 kGy. The loss of pindolol content determined by HPLC was 1.34% after irradiation with 400 kGy, while the radiolytic yield of the total radiolysis for this dose of irradiation was 2.69×10⁷ mol J^?1. By means of HPLC-MS it was possible to separate and identify one product of radiolytic decomposition, which probably is 2-((R)-3-(1H-indol-4-yloxy)-2-hydroxypropylamino)propan-1-ol formed upon oxidation. In the range of sterilisation doses (25–50 kGy), pindolol was found to show high radiochemical stability and would probably be safely sterilised by the standard dose of 25 kGy.