Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m² day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1–5 kGy) and it was revealed that PS values were reduced significantly (p≤0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1–1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1–5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p≤0.05) with the rise of radiation dose.     

Effect of gamma radiation on the physico-chemical properties of alginate-based films and beads

Alginate solution (3%, w/v) was prepared using deionized water from its powder. Then the solution was exposed to gamma radiation (0.1?25 kGy). The alginate films were prepared by solution casting. It was found that gamma radiation has strong effect on alginate solution. At low doses, mechanical strength of the alginate films improved but after 5 kGy dose, the strength started to decrease. The mechanism of alginate radiolysis in aqueous solution is discussed. Film formation was not possible from alginate solution at doses >5 kGy. The mechanical properties such as puncture strength (PS), puncture deformation (PD), viscoelasticity (Y) coefficient of the un-irradiated films were investigated. The values of PS, PD and Y coefficient of the films were 333 N/mm, 3.20 mm and 27%, respectively. Alginate beads were prepared from 3% alginate solution (w/v) by ionotropic gelation method in 5% CaCl₂ solution. The rate of gel swelling improved in irradiated alginate-based beads at low doses (up to 0.5 kGy).     

Effectiveness of silane monomer and gamma radiation on chitosan films and PCL-based composites

Chitosan films were prepared by casting from its 1% (w/w) solution. Tensile strength (TS) and tensile modulus (TM) of chitosan films were found to be 30 MPa and 450 MPa, respectively. Silane monomer (3-aminopropyl tri-methoxysilane) (0.25%, w/w) was added into the chitosan solution (1%, w/w) and films were casted. Then films were exposed to gamma radiation (5–25 kGy) and mechanical properties were investigated. It was found that at 10 kGy, the values of TS and TM were improved significantly. Silane grafted chitosan film reinforced poly(caprolactone) (PCL)-based tri-layer composites were prepared by compression molding. Silane improved interfacial adhesion between chitosan and PCL in composites. Surface of the films was investigated by scanning electron microscope (SEM) and found better morphology for silane grafted films.     

Fabrication and mechanical characterization of biodegradable and synthetic polymeric films: Effect of gamma radiation

Chitosan (1 wt%, in 2% aqueous acetic acid solution) and starch (1 wt%, in deionised water) were dissolved and mixed in different proportions (20–80 wt% chitosan) then films were prepared by casting. Tensile strength and elongation at break of the 50% chitosan containing starch-based films were found to be 47 MPa and 16%, respectively. It was revealed that with the increase of chitosan in starch, the values of TS improved significantly. Monomer, 2-butane diol-diacrylate (BDDA) was added into the film forming solutions (50% starch-based), then casted films. The BDDA containing films were irradiated under gamma radiation (5–25 kGy) and it was found that strength of the films improved significantly. On the other hand, synthetic petroleum-based polymeric films (polycaprolactone, polyethylene and polypropylene) were prepared by compression moulding. Mechanical and barrier properties of the films were evaluated. The gamma irradiated (25 kGy) films showed higher strength and better barrier properties.     

Formation of monomer residues in PS,PC, PA-6 and PVC upon γ-irradiation

Food packaging polymers, polystyrene (PS), polycarbonate (PC), polyamide-6 (PA-6), and polyvinylchloride (PVC), were irradiated with dose in the range 5–200 kGy. The quantities of corresponding monomer residues (styrene monomer, bisphenol-A, ε-caprolactam, vinyl chloride) released from target materials were analyzed using a SIM mode of GC/MSD. Styrene monomer in PS showed a slight increase from 740 to 777 ppm at 5–30 kGy and then decreased as the dose increased from 30 to 200 kGy. Bisphenol-A in PC was dose independent at the low doses, 5, 10 and 30 kGy, but its level increased from 173 to 473 ppm at 30 kGy and thereafter remained unchanged through 200 kGy. ε-Caprolactam in PA-6 was also dose independent, in the range of 5–200 kGy, but its level (122–164 ppm) was found to be higher than those (71 ppm) of non-irradiated sample. As for PVC, the quantity of vinyl chloride tended to increase from 8 to 18 ppm at 5–200 kGy.     

Radiation grafting of N,N′-dimethylacrylamide and 2-hydroxyethylmethacrylate onto polypropylene films by one step method

The work presented herein reports on polypropylene films grafted with N,N′-dimethylacrylamide and 2-hydroxyethylmethacrylate. The grafted films were obtained by an oxidative pre-irradiation method in one step using a gamma source of ⁶⁰Co. The optimal conditions such as reaction time, monomer concentrations and radiation doses were investigated. Characterization of the grafted polymers was carried out through FTIR-ATR, TGA, DSC, and swelling. Grafts onto polymeric films between 10 and 850% were obtained at doses from 20 to 150 kGy and a dose rate of 8.3 kGy/h.     

Radiation-induced grafting of styrene into poly(vinylidene fluoride) film by simultaneous method with two different solvents

Radiation-induced grafting of styrene into poly(vinylidene fluoride) (PVDF) films with 0.125 mm thickness at doses of 1 and 2.5 kGy in the presence of a styrene/N,N-dimethylformamide (DMF) solution (1:1, v/v) and at doses of 20, 40 and 80 kGy in presence of a styrene/toluene solution (1:1, v/v) at dose rate of 5 kGy h^?1 was carried out by the simultaneous method under nitrogen atmosphere and room temperature, using gamma rays from a Co-60. The films were characterized before and after modification by calculated grafting yield (GY %), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG). GY results shows that grafting increases with dose, and the grafting of styrene was confirm by FT-IR due to the new characteristic peaks and by the TG and DSC attributed to changes in thermal behavior of the grafted material. Results showed that the system allows the controlled grafting of styrene into PVDF using gamma rays at doses as low as 1 kGy in DMF.     

Effects of different matrixes on the dosimetric response of α-terthiophene films from the kGy to MGy range

Films of polymethylmethacrylate (PMMA) and polystyrene (PS) containing α-terthiophene (3T) undergo a radiochromic effect when exposed to electrons and gamma rays. The films turn either red–green or red, due to the formation of oligomeric radical cations. In both matrixes, absorbance at 465 nm grows linearly with dose when α-terthiophene concentration reaches 12%. Explored range goes up to ∼2×10⁶ Gy, with dose rates spanning over three orders of magnitude. Concerning their application as dosimeters, a higher sensitivity characterises the 3T–PMMA moiety, suggesting its suitability from the kGy range up to 1 MGy. Above this value films become fragile. 3T–PS films are less sensitive, but more radiation resistant. Therefore they better suit the medium-to-high dose dosimetry range. Dose rate influences the response sensitivity in a complex way, however above 80 and up to 3.6×10⁴ Gy/min an approximate linearity exists between log(dose rate) and sensitivity, as in the analogous cellulose triacetate system.     

Effects of electron beam irradiation on the photoelectrochemical properties of TiO2 film for DSSCs

TiO₂ has been widely utilized for various industrial applications such as photochemical cells, photocatalysts, and electrochromic devices. The crystallinity and morphology of TiO₂ films play a significant role in determining the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, the preparation of nanostructured TiO₂ films by electron beam irradiation and their characterization were investigated for the application of DSSCs. TiO₂ films were exposed to 20–100 kGy of electron beam irradiation using 1.14 MeV energy acceleration with a 7.46 mA beam current and 10 kGy/pass dose rates. These samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) analysis. After irradiation, each TiO₂ film was tested as a DSSC. At low doses of electron beam irradiation (20 kGy), the energy conversion efficiency of the film was approximately 4.0% under illumination of simulated sunlight with AM 1.5 G (100 mW/cm²). We found that electron beam irradiation resulted in surface modification of the TiO₂ films, which could explain the observed increase in the conversion efficiency in irradiated versus non-irradiated films.     

Modification of mechanical and thermal property of chitosan–starch blend films

Chitosan–starch blend films (thickness 0.2 mm) of different composition were prepared by casting and their mechanical properties were studied. To improve the properties of chitosan–starch films, glycerol and mustard oil of different composition were used. Chitosan–starch films, incorporated with glycerol and mustard oil, were further modified with monomer 2-hydroxyethyl methacrylate (HEMA) using gamma radiation. The modified films showed improvement in both tensile strength and elongation at break than the pure chitosan–starch films. Water uptake of the films reduced significantly than the pure chitosan–starch film. Thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) showed that the modified films experience less thermal degradation than the pure films. Scanning electron microscopy (SEM) and FTIR were used to investigate the morphology and molecular interaction of the blend film, respectively.     

Advanced oxidation of aromatic VOCs using a pilot system with electron beam–catalyst coupling

The decomposition of volatile organic compounds (VOCs) using a pilot system of electron beam (EB)–catalyst coupling was investigated. Two aromatic VOCs, toluene (1800 ppmC) and o-xylene (1500 ppmC), were irradiated with a dose range of 0–10 kGy at room temperature. The removal efficiencies for toluene and o-xylene were 92.4% and 94.5%, respectively, under a 10 kGy absorbed dose condition, which were higher than the results of 45.7% and 52.3% when EB-only was used, respectively. The CO₂ selectivity approached 100% for both toluene and o-xylene using the EB-catalyst coupling system, while the concentrations of O₃ formed were 0.02 ppm (toluene) and 0.003 ppm (o-xylene) at 10 kGy. The aerosol concentration was also measured as 43.2 μg/m³ (toluene) and 53.4 μg/m³ (o-xylene) at 10 kGy absorbed dose.     

Effect of gamma irradiation on physico-mechanical properties of spice packaging films

Physico-mechanical properties of two types of laminated films, commercially used for spice packaging, are investigated after gamma irradiation at 8, 10 and 15 kGy. Data showed that polyethylene terephthalate/polyethylene terephthalate/linear low density polyethylene (PET/PET/LLDPE) was more resistant to radiation compared to biaxially oriented polypropylene/cast polypropylene (BOPP/CPP) and its barrier properties slightly improved up to 15 kGy. Oxygen transmission rate of BOPP/CPP was increased by 25%, and the melting peak temperature was decreased by 3.9% at 15 kGy, which may lead to oxidation of packaged spices and loss of their aroma/flavour, respectively.     

Membrane structure control of BTDA-TDI/MDI (P84) co-polyimide asymmetric membranes by wet-phase inversion process

The formation process and morphology of BTDA-TDI/MDI co-polyimide (P84, CAS#: 58698-66-1) asymmetric flat sheet membranes have been studied. Experimental results indicated that the weight ratio of H₂O and N-methyl-2-pyrrolidone (NMP, CAS#: 872-50-4) at cloud point curve (above critical point) was a constant (7.66/92.34 (w/w)) for the P84/NMP/H₂O system. For two different casting solutions (21 wt.% P84 in pure NMP; 15 wt.% P84 in H₂O/NMP: 6.0/94.0 (w/w)), the approaching ratio α strongly dominated the formation of finger-like structure rather than the viscosity of casting solution. The formation of finger-like structure in P84 co-polyimide asymmetric membranes was due to the hydrodynamically unstable viscous fingering developed when the casting solution was displaced by a polymer-lean phase. Three types of membrane morphologies, finger-like structure, transition structure and sponge-like structure can be expected with various approaching ratio α of casting solutions. The critical approaching ratio α^* was initially defined to describe the sharp change of membrane morphology from finger-like to sponge-like structure. The casting temperature also influenced the membrane morphology. For some casting solutions (e.g. 15 wt.% P84 in H₂O/NMP: 6.4/93.6 (w/w)), the membrane morphology changed from sponge-like to finger-like structure with an increase in casting temperature. Meanwhile, the critical approaching ratio α^* also increased with an increase in casting temperature.     

Reinforcement of natural rubber/high density polyethylene blends with electron beam irradiated liquid natural rubber-coated rice husk

Coating of rice husk (RH) surface with liquid natural rubber (LNR) and exposure to electron beam irradiation in air were studied. FTIR analysis on the LNR-coated RH (RHR) exposed to electron beam (EB) showed a decrease in the double bonds and an increase in hydroxyl and hydrogen bonded carbonyl groups arising from the chemical interaction between the active groups on RH surface with LNR. The scanning electron micrograph showed that the LNR formed a coating on the RH particles which transformed to a fine and clear fibrous layer at 20 kGy irradiation. The LNR film appeared as patches at 50 kGy irradiation due to degradation of rubber. Composites of natural rubber (NR)/high density polyethylene (HDPE)/RHR showed an optimum at 20–30 kGy dosage with the maximum stress, tensile modulus and impact strength of 6.5, 79 and 13.2 kJ/m², respectively. The interfacial interaction between the modified RH and TPNR matrix had improved on exposure of RHR to e-beam at 20–30 kGy dosage.     

Effect of ionizing radiation on physicochemical and mechanical properties of commercial monolayer and multilayer semirigid plastics packaging materials

Tensile testing, overall migration tests and sensory tests were used to evaluate the effects of gamma irradiation (5–60 kGy) on six commercial semirigid packaging materials. The monolayer and multilayer materials in sheet or bottle form were: polystyrene (PS), polypropylene (PP), polyvinyl chloride/high-density polyethylene (PVC/HDPE), polyethylene terepthalate (PET), HDPE/polyamide (HDPE/PA) and HDPE. In terms of mechanical strength, PET was the most radiation-resistant material, while the HDPE monolayer and multilayer showed some degradation after 60 kGy. PS was slightly affected after 30 kGy, whereas PP was severly degraded and became very brittle. Generally, there was no change in overall migration at lower doses; at higher doses migration from PP tended to increase, while migration from HDPE/PVC tended to decrease. Odor and taste transfer as well as discoloration were observed with most plastics, especially at higher doses, and it is concluded that these tests are a sensitive and important quality control tool for evaluating irradiated packaging materials.     

Effect of gamma irradiation on cell lysis and polyhydroxyalkanoate produced by Bacillus flexus

Bacillus flexus cultivated on sucrose and sucrose with plant oil such as castor oil produced polyhydroxybutyrate (PHB), a homopolymer of polyhydroxyalkanoate (PHA) and PHA copolymer (containing hydroxybutyrate and hexanoate), respectively. Gamma irradiation of these cells (5–40 kGy) resulted in cell damage and aided in the isolation of 45% and 54% PHA on biomass weight, correspondingly. Molecular weight of PHB increased from 1.5×10⁵ to 1.9×10⁵ after irradiation (10 kGy), with marginal increase of tensile strength from 18 to 20 MPa. At the same irradiation dosage, PHA copolymer showed higher molecular weight increase from 1.7×10⁵ to 2.3×10 ⁵ and tensile strength from 20 to 35 MPa. GC, GC–MS, FTIR and ¹H NMR were used for the characterization of PHA. Gamma irradiation seems to be a novel technique, to induce cross-linking and molecular weight increase of PHA copolymer and aid in easy extractability of intracellular PHA, simultaneously.     

Degradation behavior of poly (l-lactide-co-glycolide) films through gamma-ray irradiation

Gamma-ray irradiation is a very useful tool to improve the physicochemical properties of various biodegradable polymers without the use of a heating and crosslinking agent. The purpose of this study was to investigate the degradation behavior of poly (l-lactide-co-glycolide) (PLGA) depending on the applied gamma-ray irradiation doses. PLGA films prepared through a solvent casting method were irradiated with gamma radiation at various irradiation doses. The irradiation was performed using 60Co gamma-ray doses of 25–500 kGy at a dose rate of 10 kGy/h.The degradation of irradiated films was observed through the main chain scission. Exposure to gamma radiation dropped the average molecular weight (M_n and M_w), and weakened the mechanical strength. Thermograms of irradiated film show various changes of thermal properties in accordance with gamma-ray irradiation doses. Gamma-ray irradiation changes the morphology of the surface, and improves the wettability. In conclusion, gamma-ray irradiation will be a useful tool to control the rate of hydrolytic degradation of these PLGA films.     

Effect of gamma irradiation on the expressed proteins in the foodborne pathogen Staphylococcus aureus

A capillary electrophoresis method with UV detection was developed to analyze protein composition of the foodborne pathogen Staphylococcus aureus. Bacterial samples containing 10⁹ CFU/ml, obtained after two cycles of incubations of 24 h, were gamma irradiated at different doses of 1.2, 3.5 and 2.9 kGy to respectively create damage cells, to kill cells and to provoke viable but non cultivable cells (VBNC). It was observed that an irradiation at a sensitive dose of 1.2 kGy caused a significantly increase in the protein with molecular weight (MW) of 17.7 kDa (from 0.61% to 1.2%). This treatment also caused decreases in the expressed proteins with the MWs of 16.3 kDa (from 6.2% to 5.3%) and of 23.4 kDa (from 4.0% to 2.30%). Irradiation at a VBCN dose of 2.9 kGy caused increases in expressed proteins with the MWs of 17.7 kDa (from 0.61% to 3.43%), 18.7 kDa (from 1.04% to 4.30%), 19.5 kDa (from 0.71% to 2.30%), 21.1 kDa (from 1.20% to 3.80%). Moreover, this treatment (2.9 kGy) also caused significantly decreases (P≤0.05) in the expressed proteins with the MW of 30.7 kDa (from 8.6% to 5.15%), 36.3 kDa (from 3.1% to 2.7%) and 40.5 kDa (from 11.3% to 8.5%). Finally, for the irradiation at a lethal dose of 3.5 kGy, it can be found that the expressed proteins with the MW of 17.7 kDa, 18.7 kDa and 19.5 kDa were increased less than that of expressed proteins at the VCNC dose (2.9 kGy) and these might be the very important proteins which are responsible for the survival of the S. aureus. Further, there were also the decreases in expressed proteins with the MW of 30.7 kDa, 36.3 kDa and 75.1 kDa at this dose of treatment (3.5 kGy) which can be expected that these proteins are seriously affected at high dose of γ-irradiation treatment.     

Fabrication and characteristics of polyHEMA artificial skin with improved tensile properties

PolyHEMA-based hydrogel synthesized by the UV-radiation induced polymerization technique is used to prepare the strength-proved artificial skin in order to improve the handling procedure for curing the burned wound. The tensile strength of the artificial skin membrane is measured following the ASTM standard. The strength decreases with increasing amount of the initial water added to the mixture of HEMA (2-hydroxyethyl methacrylate) monomer, ethylene glycol dimethacrylate (EGDMA) cross linker and benzoin isobutyl ether (BIE) initiator. The maximum strength of the artificial skin membrane reaches 9 kg/cm², as the hydrogel contains equilibrium water around 30 wt%. The artificial skin so fabricated presents several additional characteristics including good wettability, complete transparency and dimensional change during water absorption and evaporation.     

Predicting optimal conditions to minimize quality deterioration while maximizing safety and functional properties of irradiated egg

Irradiation is an excellent method for improving the safety and functional properties of egg. However, the internal quality of egg can be deteriorated due to a rapid decrease in Haugh units. In this study, the optimal conditions for maintaining the quality and maximizing the safety and functional properties of egg were determined when combination of irradiation and chitosan coating was treated using response surface methodology (RSM). Independent degradation parameters—irradiation dose (0–2 kGy) and concentration of chitosan coating (0–2%) were assigned (?2,–1, 0, 1, 2), and 10 intervals were set on the basis of central composite design for the degradation experiment. The dependant variables within a confidence level less than 5% were Haugh units, foaming ability, foam stability, and number of Salmonella typhimurium. The predicted maximum values of Haugh units and foaming ability were 82.7 (irradiation dose 0.0006 kGy and concentration of chitosan solution 1.03%) and 62.2 mm (1.99 kGy and 0.86%), respectively. S. typhimurium inoculated on the egg surface was not detected after 1.86 kGy and 0.48%. Based on superimposing four-dimensional RSM with respect to freshness (Haugh units), functional property (foaming capacity and foam stability), and reduction of S. typhimurium, the predicted optimum ranges for irradiation dose and chitosan solution concentration were 0.35–0.65 kGy and 0.25–0.85%, respectively. The predicted optimum values were obtained from 0.45 kGy and 0.525%. This methodology can be used to predict egg quality and safety when different combination treatments were applied.