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).     

Polymerization of calcium caseinates solutions induced by gamma irradiation

Solutions of calcium caseinate (5%) combined with propylene glycol (PG) or triethylene glycol(TEG) (0, 2.5% and 5%) and used for the development of edible films and coatings, were irradiated at doses between 0 to 128 kGy. Solutions were chromatographed through toyopearl HW 55F resin to observe the effect of irradiation on cross-link reactions. In unirradiated calcium caseinate solutions, two peaks could be observed (fractions 30 and 37) while samples irradiated at 64 kGy and 128 kGy showed one shifted peak at fraction 32 and 29 respectively. No effect of the plasticizers was observed. According to proteins standards of knowed molecular weights, the molecular weight of calcium caseinate increased approximately 10 times when irradiated at 128 kGy and 5 times when irradiated at 64 kGy. The physico-chemical properties of bio-films prepared with the irradiated solutions, demonstrated that tensile strength at break increased with increase of irradiation dose. A maximum dose was obtained at 16 kGy.     

Mechanical and thermal properties of irradiated films based on Tilapia (Oreochromis niloticus) proteins

Proteins are considered potential material in natural films as alternative to traditional packaging. When gamma radiation is applied to protein film forming solution it resulted in an improvement in mechanical properties of whey protein films. The objective of this work was the characterization of mechanical and thermal properties of irradiated films based on muscle proteins from Nile Tilapia (Oreochromis niloticus). The films were prepared according to a casting technique with two levels of plasticizer: 25% and 45% glycerol and irradiated in electron accelerator type Radiation Dynamics, 0.550 MeV at dose range from 0 to 200 kGy. Thermal properties and mechanical properties were determined using a differential scanning calorimeter and a texture analyzer, respectively. Radiation from electron beam caused a slightly increase on its tensile strength characteristic at 100 kGy, while elongation value at this dose had no reduction.     

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.     

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.     

Investigation of polymer degradation by addition of magnesium

The effect of alkali metal magnesium on polymer degradation of physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of Mg of different concentrations (0–30 ppm) to natural rubber latex and irradiation with various radiation doses (0–20 kGy). The radiation doses were optimized (12 kGy), and the adverse effect of Mg was studied against a reference film prepared without metal. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films were decreased with increasing metal ion concentrations and decreasing radiation doses. The mechanical properties of the films were reduced by nearly 10% for 30 ppm Mg ions and at the optimum dose. In contrast, elongation at break, permanent set, and swelling ratio of the films were increased at the same conditions. The maximum tensile and tear strengths of irradiated rubber films without additive were 29.33 MPa and 47.95 N/mm, respectively, at a radiation dose of 12 kGy, and these values were about six times higher than those of blank samples. With the addition of Mg, the corresponding values decrease continuously, and the minimum values were found to be 26.35 MPa and 42.675 N/mm, respectively. The effect of divalent alkali metal on polymer chain scission can be explained by the classical electron concept reported in this article.     

Mechanical response of high density polyethylene to gamma radiation from a Cobalt-60 irradiator

The response of High Density Polyethylene (HDPE) to gamma irradiation is important for a variety of applications, from the durability of hip replacements after gamma sterilization to the degradation of power cable insulation that guides the licensing and regulation of nuclear power plants. HDPE samples are irradiated with up to 58.8 kGy from a Cobalt-60 gamma irradiator, and mechanical properties are examined using models assuming exponential behavior. Increasing the radiation dose led to increases to the ultimate strength and the Rockwell hardness with a corresponding reduction in the maximum elongation at ultimate strength, supporting the hypothesis that the samples increased their strength and brittleness.     

STUDY ON THE PROPERTIES OF BLEND OF NATURAL RUBBER LATEX/METHYL METHACRYLATE GRAFTED RUBBER LATEX BY GAMMA RADIATION

Natural rubber latex(NRL)and methyl methacrylate(MMA)grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature.The tensile properties, swelling ratio and permanent set were measured.The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy.Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose.Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends.The decreasing trend of permanent set is high up to 5 kGy absorbed dose,and beyond that dose,it becomes almost flat.     

EFFECT OF GAMMA RAYS IN THE PREPARATION OF POLYMER AND HYDROGEL FROM ACRYLAMIDE MONOMER

The formation of polymer and hydrogel from aqueous solutions having 20, 30 and 40% concentrations ofacrylamide monomer by γ-ray irradiation processing in the dose range 0.06-30 kGy using a Co-60 source and theircharacterization have been observed. Polymer conversion and gel fraction are found to depend on radiation doses. Polymerconversion increases with the increase of dose, depending on the solution concentration, where maximum conversion isachieved at 0.18, 0.16 and 0.10 kGy for 20%, 30% and 40% concentrations, respectively. On the other hand, gel fractionincreases with dose from the gel point (0.12 kGy) for all concentrations, where 100% conversion of gel occurs at doses≥5 kGy. Tensile strength, viscosity and molecular weight (M_w) of polymer samples increase with both the dose and theconcentration, showing a high value of M_w up to≈10~8. Swelling of hydrogels under water with respect to time varies due tothe variation of cross-linking density formed in the gels and the maximum swelling mainly occurs within 24 h. A remarkable change of surface morphology reveals characteristic features of monomer, polymer and hydrogel films.     

Irradiation of Crosslinked, Poly(Vinyl Alcohol) Blended Hydrogel for Wound Dressing

In order to obtain a more ideal hydrogel wound dressing, crosslinked hydrogel films blended with polyvinyl alcohol (PVA), polyvinyl pyrrolidone, kappa-carrageenan (KC), and powder silk were prepared by electron beam, and their physiochemical properties were investigated as a combination of function factors. The experimental results showed that the gel fraction of the hydrogel films depended mainly on irradiation dose and the monomer concentration of the polymers, the properties of hydrogel could be greatly extended or improved by blending homopolymers. The rate of gel formation of the hydrogel was raised, and the water evaporation from hydrogel could be retarded after mixing with KC, while the tensile strength of hydrogel films were obviously increased after mixing with silk. Toxicity and healing effect of PVA/PVP/KC/silk blended hydrogel films as wound dressings were evaluated. The irradiated blended hydrogel showed satisfactory properties for wound dressing, the hydrogel did not induceany acute general toxic effects, and it is effective for fast healing of wound.     

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.     

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.     

Effects of gamma radiation on the photoluminescence properties of polycarbonate matrices doped with terbium complex

Luminescent films containing terbium complex [Tb(acac)₃(H₂O)₃] (acac=acetylacetonate) doped into a polycarbonate (PC) matrix were prepared and irradiated at low-dose gamma radiation with ratio of 5 and 10 kGy. The PC polymer was doped with 5% (w/w) of the Tb³⁺ complex. The thermal behavior was investigated by utilization of differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). Changes in thermal stability due to the addition of doping agent into the polycarbonate matrix. Based on the emission spectra of PC:5% Tb(acac)₃ film were observed the characteristic bands arising from the ⁵D₄→⁷F_J transitions of Tb³⁺ ion (J=0–6), indicating the ability to obtain the luminescent films. Doped samples irradiated at low dose of gamma irradiation showed a decrease in luminescence intensity with increasing of the dose.     

Role of Divalent Metals in Polymer Degradation

The role of divalent metals in the degradation of the physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of metals (Cu, Mg, etc.) of different concentrations (0–30ppm) to natural rubber latex and irradiated with various radiation doses (0–20kGy). The radiation doses were optimized (12kGy), and the adverse effect of metal ions was studied against a reference film prepared with no metal ions. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films decreased with increasing metal ion concentrations and decreasing radiation doses. The mechanical properties of the films were reduced by 10–15% for 30ppm metal ions and at the optimum dose. In contrast, elongation at break, permanent set, and swelling ratio of the films increased at the same conditions. The relative effect of metal ions can be explained by the classical electron concept, reported in this article.     

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.     

k-型卡拉胶/聚乙烯吡咯烷酮共混水凝胶的辐射制备及性质研究

采用辐射技术制备了κ-型卡拉胶(KC)/聚乙烯基吡咯烷酮(PVP)共混水凝胶,研究了共混凝胶内KC含量、PVP的分子量和辐照剂量等对KC/PVP共混水凝胶性质的影响.实验发现,KC与高分子量的PVP(k-90)共混后在一定剂量范围内辐照可得到高强度、高溶胀行为的KC/PVP共混水凝胶,随着共混凝胶内KC含量的增加,凝胶强度及溶胀性能均显著提高.分析表明,KC与高分子量的PVP共混后,在较低剂量下KC的降解被抑制,从而获得一种由物理交联的KC和化学交联的PVP形成的互穿网络(IPN)凝胶.     

K-型卡拉胶/聚乙烯吡咯烷酮共混水凝胶的辐射合成

采用辐射技术合成了K 型卡拉胶 (KC) /聚乙烯吡咯烷酮 (PVP)共混水凝胶 ,研究了天然高分子KC、单体N 乙烯基吡咯烷酮 (N VP)、交联剂二甲基丙烯酸十四甘醇酯 ( 1 4G) ,辐照剂量以及剂量率等对辐射合成的KC/PVP共混水凝胶性质的影响 .实验发现 ,KC与适当比例的N VP共混后在一定剂量范围内辐照可得到高强度、高溶胀行为的KC/PVP共混水凝胶 ,随着共混凝胶内KC含量的相对增加 ,凝胶强度及溶胀性的能均显著提高 ,但合成该共混凝胶的最佳剂量却相对提前 ;加入 1 4G后降低了KC/PVP共混凝胶辐射合成最佳剂量 ,同时使KC/PVP共混凝胶的强度进一步提高 ;剂量、剂量率对KC/PVP共混凝胶的性质亦有很大的影响 .分析表明 ,KC与N VP共混后 ,在较低剂量下KC的降解被抑制 ,从而获得一种由物理交联的KC和化学交联的PVP形成的互穿网络 (IPN)凝胶     

Gamma-Irradiated Gelatin-Based Films Modified by HEMA for Medical Application

The present article describes the synthesis and characterization of bi-component polymer systems based on gelatin films incorporated with 2-hydroxyethyl methacrylate (HEMA) monomer, developed for medical application. Gelatin films were prepared by the addition of HEMA of different concentrations (0–30 wt.%) and irradiated with various radiation doses (0–5 kGy). Tensile strength and tear strength of the irradiated gelatin films were found to increase with increasing HEMA up to 20 wt.% as well as radiation doses (1 kGy) as optimized. The maximum tensile and tear strengths of irradiated gelatin films with HEMA were found to be 79.1 MPa and 83.2 N/mm, respectively, at the optimum conditions, and these values were about double that of a reference film prepared without additives. In addition, morphological analysis was done by scanning electron microscopy (SEM) and showed how HEMA cemented and was covered with gelatin in the blend. Thermomechanical analysis was carried out to investigate the shifting of glass transition temperature (T_g) towards higher temperature due to HEMA addition, and the effect of this film was tested on the human body in order to determine whether it can be applied for medical purposes.     

Studies on the methods of identification of irradiated food I. Seedling growth test

A seedling growth test for the identification of gamma irradiated edible vegetable seeds was described. The identification of gamma irradiated grape and the other seeds has been investigated. The purpose of this study was to develop an easy, rapid and practical technique for the identification of irradiated edible vegetable seeds. Seven different irradiated edible vegetable seeds as: rice ( ), peanut ( ), maize ( ), soybean ( ), red bean ( ), mung bean ( ) and catjang cowpea ( ) were tested by using the method of seedling growth. All of the edible vegetable seeds were exposed to gamma radiation on different doses, O(CK), 0.5, 1.0, 1.5, 2.0, 3.0, 5.0 kGy. After treatment with above 1.0 kGy dose to the seeds, the seedling rate was less than 50% compared with the control. Although the seedling rate of rice seeds can reached 58%, the seedling growth was not normal and the seedling leaves appeared deformed. The results by this method were helpful to identify gamma treatment of the edible vegetable seeds with above 1.0 kGy dose.     

Effect of Manganese on Radiation Vulcanization of Natural Rubber

Manganese was added as a promoter to investigate physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films. RVNRL films were prepared by the addition of Mn with the concentration range 0–30 ppm to natural rubber latex and irradiated with various radiation doses (0–20 kGy). Tensile strength, tear strength, and cross-linking density of the irradiated rubber films increased with increasing the concentration of Mn ions as well as radiation doses. In contrast, elongation at break, permanent set, and swelling ratio of the films were decreased under the same conditions. The concentration of Mn ions and radiation doses were optimized and found to be 20 ppm and 12 kGy, respectively. The maximum tensile and tear strengths of irradiated rubber films were observed as 29.12 MPa and 44.78 N/mm, respectively at the optimum conditions. The mechanical properties of the films increased markedly with the addition of Mn until they attained the highest values of 33.88 MPa and 54.77 N/mm, respectively. These enhancements, which reached approximately 20% at the most favorable conditions, can be explained by the effect of transition metals in view of Fajan’s rules regarding the covalent character of ionic bonds and suggest that the higher the difference in charges between cation and anion, the higher the ability to form distortion or polarization of ions.