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.     

Effects of electron-beam irradation on some structural properties of granulated polymer blends

The aim of this article was to show the effects of the electron radiation dose and presence of a compatibiliser on the peak melting temperature (T_pm) of the crystalline phase, crystallinity (X_c), and melt flow rate (MFR) of granulated blends of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) as well as of blends of LDPE, HDPE, and PP. The purpose of applying the high-energy electron radiation with doses up to 300 kGy and of adding a compatibiliser was to enhance mechanical properties of the studied blends and, at the same time, to investigate the possibility of using this technique in the processes of recycling polymeric materials. As the compatibilisers, the styrene–ethylene/butylene–styrene elastomer grafted with maleic anhydride (SEBS-g-MA) and trimethylol propane trimethacrylate (TMPTA) were utilised; they were added at the amounts of 5, 10, and 15 wt% and 1, 2, and 3 wt%, respectively. The enhancement of mechanical properties was accompanied by the following effects, discussed in this article: (i) a decrease in the peak melting temperature upon the electron radiation for the crystalline phase of LDPE, HDPE, and PP that constituted the studied granulated blends and (ii) changes in MFR upon both the electron radiation and the addition of compatibilisers.     

Cationic concentration effects on electron beam cured of carbon-epoxy composites

Electron beam (e-beam) curing is a technology that offers advantages over the thermal curing process, that usually requires high temperature and are time-consuming. E-beam curing is faster and occurs at low temperatures that help reduce residual mechanical stresses in a thermoset composite. The aim of the present study is to analyze the effects of cationic initiator (diaryliodonium hexafluoroantimonate) ranged from 1 to 3 wt% in DGEBA (diglycidyl ether of bisphenol A) epoxy resin when cured by a 1.5 MeV electron beam. The specimens were cured to a total dose of 200.4 kGy for 40 min. Analyses by dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) show that the e-beam irradiated samples with 2 wt% cationic initiator were 96% cured obtained a glass transition temperature (tan δ) of 167 °C. The same epoxy resin, thermally cured for 16 h with an anhydride hardener, reached a T_g (tan δ) of 136 °C. So, the irradiated sample had its T_g increased approximately 20% and the curing process was much less time consuming.     

Study of the morphology,thermal and mechanical properties of irradiated isotactic polypropylene films

Thin films of isotactic polypropylene (iPP) are of great economical importance and their production is quite challenging due to the need of very fast uniaxial or biaxial expansion. During the expansion, critical problems usually arise, like structure disruption, shear thinning, causing material, energy and time losses. This work aims to study the surface morphology and compare the thermal, mechanical properties of PP films irradiated by gamma ray in an acetylene atmosphere after uniaxial expansion. PP films were made by compression molding at 190 °C with cooling in water at room temperature and irradiated by gamma ray, at (5, 12.5 and 20 kGy) under acetylene atmosphere. After irradiation the samples were submitted to thermal treatment at 90 °C for 1 h and then stretched out at 170 °C using an Instron machine. The surface of PP films, pristine and modified, (i.e., irradiated), was studied using optical microscopy (OM) and scanning electron microscopy (SEM). The changes in morphology, crystallinity and tensile parameters, like yield stress, rupture stress and elongation strain of the PP with irradiation dose were investigated. The results showed some evidences of gel formation due to crosslinking and/or long chain branching induced by radiation.     

Preparation and properties of new flame retardant unsaturated polyester nanocomposites based on layered double hydroxides

The preparation of new layered double hydroxides/unsaturated polyester (LDH/UP) nanocomposites was performed and the effect of LDH on the resin properties was studied. Two different organo-LDHs have been prepared, adipate-LDH (A-LDH) and 2-methyl-2-propene-1-sulfonate-LDH (S-LDH); in order to evaluate the influence of these nanofillers, samples with two different concentrations were dispersed in the matrix. The physical, thermal, mechanical and fire reaction properties of nanocomposites were studied. Intercalated layered structures were observed for the different organo-LDH loadings (1 and 5 wt%). Mechanical properties studied under flexural tests show that incorporation of organo-LDH in the resin reduces the flexural strength of polyester resin while the flexural modulus is unchanged for the S-LDH/UP composites and increased with 1 wt% of A-LDH. Adding 1 wt% of A-LDH to the resin produces an important reduction on the flexural strength, but an increase of the flexural modulus. The study of fire reaction properties, using cone calorimeter, suggested a significant reduction in the UP flammability, by 46 and 32%, by incorporating 1 wt% of A-LDH and 5 wt% S-LDH, respectively. Mass loss curves show enhanced char formation with the different loads tested while the amount of evolved smoke remains quite unchanged.     

Effect of radiation dose on the properties of natural rubber nanocomposite

Effect of radiation dose and carbon nanotubes (CNT) on the mechanical properties of standard Malaysian rubber (SMR) was investigated in this study. SMR nanocomposites containing 1–7 phr CNT were prepared using the solvent casting method and the nanocomposites were radiated at doses of 50–200 kGy. The change in mechanical properties, especially, tensile strength (Ts), elongation at break (Eb), hardness and tensile modulus at 100% elongation (M₁₀₀) were studied as a function of radiation dose. The structure and morphology of reinforced natural rubber was investigated by FESEM, TEM and AFM in order to gain further evidence on the radiation-induced crosslinking. It was found that the Ts, M₁₀₀ and the hardness of the SMR/CNT nanocomposites significantly increased with radiation dose; the elongation at break exhibited an increase up to 100 kGy, and a downward trend thereafter. Results on gel fraction further confirmed the crosslinking of SMR/CNT nanocomposites upon radiation.     

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.     

Swelling characteristics and application of gamma-radiation on irradiated SBR-carboxymethylcellulose (CMC) blends

Blends of styrene butadiene rubber (SBR) with varying loading degree from 60 wt% to 100 wt% of carboxymethylcellulose (CMC) have been prepared. Gamma radiation vulcanization of prepared blends was carried out with doses varying between 50 kGy and 250 kGy. Mechanical properties, namely, tensile strength (Ts), elongation at break (E_b) and hardness were followed up as a function of loading degree of CMC and gamma irradiation dose. Moreover, physical properties, specifically swelling number (SN) and gel fraction % (GF%) were undertaken. Results obtained showed an improvement in mechanical as well as in physical properties with increasing either CMC content or dose of irradiation. Thermal properties namely thermo gravimetric analysis (TGA) was carried out.     

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.     

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).     

Characterization of a power bipolar transistor as high-dose dosimeter for 1.9–2.2 MeV electron beams

Results of the characterization studies on a power bipolar transistor investigated as a possible radiation dosimeter under laboratory condition using electron beams of energies from 2.2 to 8.6 MeV and gamma rays from a ⁶⁰Co source and tested in industrial irradiation plants having high-activity ⁶⁰Co γ-source and high-energy, high-power electron beam have previously been reported. The present paper describes recent studies performed on this type of bipolar transistor irradiated with 1.9 and 2.2 MeV electron beams in the dose range 5–50 kGy. Dose response, post-irradiation heat treatment and stability, effects of temperature during irradiation in the range from –104 to +22 °C, dependence on temperature during reading in the range 20–50 °C, and the difference in response of the transistors irradiated from the plastic side and the copper side are reported. DLTS measurements performed on the irradiated devices to identify the recombination centres introduced by radiation and their dependence on dose and energy of the electron beam are also reported.     

Thermal,tensile and rheological properties of linear low density polyethylene (LLDPE) irradiated by gamma-ray in different atmospheres

The aim of this paper is to investigate structural changes of linear low density polyethylene (LLDPE) modified by ionizing radiation (gamma rays) in different atmospheres. The gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical–chemical and mechanical properties. Gamma irradiation originates free radicals which can induce chain scission or recombination, providing its annihilation, branching or crosslinking. This polymer was irradiated with gamma source of ⁶⁰Co at doses of 5, 10, 20, 50 or 100 kGy at a dose rate of 5 kGy/h. The changes in molecular structure of LLDPE, after gamma irradiations were evaluated using thermogravimetric analyzer (TGA) and tensile machine and oscillatory rheology. The results showed the variations of the properties depending on the dose at each atmosphere.     

Some composting and biodegradation effects of physically or chemically crosslinked poly(lactic acid)

Polylactide (PLA) crosslinked by using both triallyl isocyanurate (TAIC) and electron radiation or using dicumyl peroxide (DCP) was studied with the aim of examining the behaviour of the modified polymer under various environmental conditions. Thus, the polymer samples were subjected to composting in an industrial pile, exposed to proteinase K, or incubated in sea water. The number-average molecular weight (M_n), melt flow index (MFI), crystallinity (χ), tensile strength (σ_M) and mass loss (in the case of samples treated with proteinase K) were determined. It was found that neat PLA irradiated with high-energy electrons underwent degradation that increased during composting. As a result, the value of M_n of this polymer dramatically decreased. It appeared that PLA crosslinked with TAIC and electron radiation contained, in addition to the crosslinked phase, a phase strongly degraded by this radiation, which facilitated hydrolytic degradation during composting. The σ_M value of PLA crosslinked with TAIC and electron radiation rapidly decreased during composting, whereas that of PLA crosslinked chemically and composted for three weeks slightly increased. As the electron radiation dose increased, the mass loss of PLA containing TAIC and treated with proteinase K decreased, which indicated that the physical crosslinking of PLA hindered enzymatic degradation of this polymer. Important changes in both neat and physically crosslinked PLA incubated in sea water for nine weeks were not detected.     

Large-scale synthesis of silver nanoparticles using Ag(I)–S12 polymer through electron beam irradiation

Size-controlled large scale synthesis of silver nanoparticles was performed using Ag(I)–S12 inorganic-organic hybrid polymer with supramolecular structures though electron beam irradiation. The Ag(I)–S12 polymer was simply prepared by mixing dodecanethiol with the solution of silver salts. The silver nanoparticles with various sizes were prepared from Ag(I)–S12 polymer with an electron beam voltage from 0.3 MeV to 2 MeV, current from 0.06 mA to 0.48 mA, and/or irradiation time from 1 to 10 min. The morphology and chemical composition of the irradiated samples were characterized by transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR).     

Electron beam combined with hydrothermal treatment for enhancing the enzymatic convertibility of sugarcane bagasse

The use of microbial cellulolytic enzymes is the most efficient process to liberate glucose from cellulose in biomass without the formation of fermentation inhibitors. A combination of pretreatment technologies is an alternative way to increase the access of enzymes to cellulose, and consequently, the conversion yield. In this way, the present study reports on the enzymatic hydrolysis of SCB submitted to three kinds of pretreatment: electron beam processing (EBP), and EBP followed by hydrothermal (TH) and diluted acid (AH) treatment. SCB samples were irradiated using a radiation dynamics electron beam accelerator, and then submitted to thermal and acid (0.1% sulfuric acid) hydrolysis for 40 and 60 min at 180 °C. These samples were submitted to enzymatic hydrolysis (EH) using commercial preparations, including Celluclast 1.5 L and beta-glycosidase. The addition of diluted acid improved TH treatment allowing for a shorter application time. EBP with 50 kGy increased the enzymatic hydrolysis yield of cellulose by 20% after TH and 30% after AH.     

Effect of gamma irradiation on the antimicrobial and free radical scavenging activities of Glycyrrhiza glabra root

The efficacy of gamma irradiation as a method of decontamination for food and herbal materials is well established. In the present study, Glycyrrhiza glabra roots were irradiated at doses 5, 10, 15, 20 and 25 kGy in a cobalt-60 irradiator. The irradiated and un-irradiated control samples were evaluated for phenolic contents, antimicrobial activities and DPPH scavenging properties. The result of the present study showed that radiation treatment up to 20 kGy does not affect the antifungal and antibacterial activity of the plant. While sample irradiated at 25 kGy does showed changes in the antibacterial activity against some selected pathogens. No significant differences in the phenolic contents were observed for control and samples irradiated at 5, 10 and 15 kGy radiation doses. However, phenolic contents increased in samples treated with 20 and 25 kGy doses. The DPPH scavenging activity significantly (p<0.05) increased in all irradiated samples of the plant.     

Effects of electron beam irradiated natural casings on the quality properties and shelf stability of emulsion sausage

The effect of electron beam irradiated hog and sheep casings (1, 3, and 8 kGy) on the physicochemical properties and shelf stability of emulsion sausage was evaluated. There were no significant differences in pH, instrumental color, sensory properties (overall acceptability), and hardness between all the samples. The cooking yields for the irradiated treated samples were larger than that of the yields obtained for the non-irradiated samples for both the hog and sheep casing. The irradiated natural casings accelerated lipid oxidation, and inhibited the formation of volatile basic nitrogen and the increase in total aerobic bacteria. In conclusion, the natural casings irradiated below at a dose of 3 kGy had no effect on physicochemical and sensory properties of the emulsion sausages, however, that improved the shelf-stability over 5 weeks. Therefore, natural casings irradiated at moderate doses are suitable for sausage production.     

Electron irradiation of polyurethane using UV spectroscopy,GPC and swelling analyses

Investigation has been performed on thermoplastic and aromatic polyetherurethane (ETPU) irradiated by an electron beam of 200 keV energy. The changes in chemical structure resulting from the irradiation and particularly the development of polyene sequences were studied using UV spectroscopy. Moreover, structural transformations have been characterized by GPC for soluble samples and by the swelling technique for insoluble samples. An increase in crosslinking rate of the polymer is observed and analyzed. The results of the chemical and structural modifications show that the development of polyene sequences and the crosslinking of the ETPU reached a maximum at about 200 μm, and that these effects increased with the fluence. Moreover, it also appeared that the increase in temperature has induced an increase in crosslinking, but the scission process has prevailed to the crosslinking with the increase in electron flux.     

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.     

Advanced oxidation process by electron-beam-irradiation-induced decomposition of pollutants in industrial effluents

Electron-beam irradiation considered on advanced oxidation process induces the decomposition of pollutants in industrial effluent. Experiments were conducted using a radiation dynamics electron beam accelerator with 1.5 MeV energy and 37 kW power. The effluent samples from an industrial complex were irradiated using the IPEN's liquid effluent irradiation pilot plant. The experiments were conducted using one sample from each of eight separate industrial units and five samples of a mixture of these units. The physical–chemical characterization of these samples is presented. The electron beam irradiation was efficient in destroying the organic compounds delivered in these effluents, mainly, chloroform, dichloroethane, methyl isobutyl ketone, toluene, xylene and phenol. The necessary dose to remove 90% of the most organic compounds from industry effluent was 20 kGy. The removal of organic compounds from this complex mixture was explained by the destruction G value (Gd) that was obtained for those compounds with different initial concentrations and was compared with literature.