Effect of crosslink density on some properties of electron beam-irradiated styrene–butadiene rubber

Crosslink densities of electron beam (EB)-irradiated styrene–butadiene rubber (SBR) samples were measured by using a novel magnetic resonance crosslink density spectrometer (MRCDS). With 1,1,1-trimethylolpropane triacrylate (TMPTA) loading increasing, the crosslink density of EB-irradiated SBR increases up to a certain level, and then decreases in the irradiation dose range 50–200 kGy. Tensile strength, elongation at break, thermal stability and pyrolysis products of the EB-irradiated SBR samples with different crosslink densities were also studied in this paper.     

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.     

Electron beam crosslinking of poly(ethylene-co-vinyl acetate)/clay nanocomposites

Effect of electron beam irradiation on the thermal and mechanical properties of poly(ethylene-co-vinyl acetate) (EVA)/clay nanocomposites prepared by melt blending method has been investigated. The hot set test results show that elongation at high temperature under static load decreased with the increase of irradiation dose. The tensile modulus increased continuously with increasing dose. While the tensile strength increased up to 100 kGy, it decreased with further increase in dose. The elongation at break decreased continuously with increasing dose. Thermogravimetric analysis showed that thermal stability of the EVA/clay nanocomposites improved with increasing dose. The improvement in the mechanical and thermal properties is attributed to the formation of radiation-induced crosslinking as evidenced by the gel content results.     

Effect of crystallinity on electrical properties of electron beam irradiated LDPE and HDPE

Two sets of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) sheets were prepared using warm press system. Each set consisted of three subsets which were made in different cooling rate procedures: fast cooling with cassette; exposing in open air; and exposing in 0 °C water, to investigate the crystallinity effects. The samples were irradiated with 10 MeV electron beam in the dose range of 0–370 kGy using a Rhodotron accelerator system. The variation of electrical properties of all samples such as breakdown voltage, surface and volume resistivity were measured and graphed against the dose values. The radiation induced cross-linking and cooling procedure effects were investigated and compared in the obtained results.     

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 electron irradiation on nitrofurans and their metabolites

Research on the degradation of aqueous furazolidone, nitrofurantoine and semicarbazide (SC) solutions, and 3-amino-2-oxazolidinone (AOZ) residues in tissues of chicken and crucian under electron beam irradiation have been carried out. Results showed that about 75% furazolidone and 70% nitrofurantoine degraded at 6 kGy dose, and SC with the initial concentration of 667 μg/L degraded by 94% at 12 kGy dose. While AOZ in the crucian and chicken degraded by 22.5% and 20.7%, respectively, after being irradiated at 12 kGy. The degradation conditions were investigated to provide a reference to improve irradiation techniques.     

Electron beam irradiations of polypropylene syringe barrels and the resulting physical and chemical property changes

Mechanical, thermal, chemical decomposition and electron spin resonance (ESR) methods were used to study electron beam irradiated polypropylene syringe barrels that were irradiated to a total fractionated dose of 0, 20, 40, 60, and 80 kGy (in steps of 20 kGy). Dose mapping was conducted to determine dose to and through the syringe barrel. Analysis of these data indicated that degradation of the polypropylene syringes increased with an increase in electron beam irradiation.     

The role of medium radiation dose on microbiological safety and shelf-life of some traditional soups

Irradiation at medium doses in combination with cryogenic condition along the process to ensure the safety, quality and to extend the shelf-life of prepared meals have been investigated. Semi-concentrated black, ox-tail, chicken vegetable and chicken sweet corn soups were individually packed in a dry laminate pouch of PET 12 μ/LDPE adh.2 μ/Al–foil 7 μ/LDPE adh/LLDPE (C₄) 50 μ under vacuum followed by freezing for 24 h at −18 °C prior to irradiation with doses of 1, 3, 5 and 7 kGy at cryogenic condition (−79 °C), respectively. Both the non-irradiated and irradiated prepared meals were then stored in refrigerator at 5±2 °C. Non-irradiated and the irradiated samples at 1 kGy were mostly damaged after a week of storage. Gamma irradiation at doses of 5–7 kGy for the soups could reduce microbial load by about 2–3 log cycles, respectively, without affecting the physical–chemical parameters and palatability within 2–3 months while the unirradiated samples could only withstand for 1 month storage time.     

1-Chloronaphthalene decomposition in different gas mixtures under electron beam irradiation

The decomposition by electron beam (EB) irradiation of 1-chloronaphthalene in different gas matrices (air, N₂) was studied. Over 80% 1-chloronaphthalene was decomposed in air at 58 kGy dose when the initial concentration of 1-chloronaphthalene was 12–30 mg/Nm³. Over 50% 1-chloronaphthalene was decomposed in nitrogen when the initial concentration of 1-chloronaphthalene was 15–42 mg/Nm³.     

Evaluation of time-accelerated irradiation method of elastomer by modulus–ultimate elongation profile

“Generalized modulus–ultimate elongation profile” was induced from the relationship between the modulus and the ultimate elongation of an elastomer that was quantitatively added crosslinking and scission. This profile can be used to evaluate the time-accelerated irradiation methods of ethylene-propylene-diene elastomer. The irradiation under low dose rate (0.33 kGy/h) at room temperature was the reference condition. The short-time irradiation condition was 4.2 kGy/h in 0.5 MPa oxygen at room temperature and 5.0 kGy/h in air at 70 °C. The former tended to bring about the higher ratio of scission than the reference condition; the latter tended to bring about the higher ratio of crosslinking.     

Development of silicon nitride fiber from Si-containing polymer by radiation curing and its application

A silicon nitride fiber (Si₃N₄) was synthesized from polycarbosilane (PCS) fiber by radiation application. PCS fibers were cured by electron beam (EB) irradiation in a helium gas atmosphere prior to the pyrolysis. The cured PCS fiber was converted to Si₃N₄ ceramic fiber with flexibility by nitridation in ammonia gas at a high temperature of 500–1000°C. The obtained Si₃N₄ fibre showed a high heat resistance up to 1300°C, a high tensile strength of 2 GPa and excellent electrical resistivity of 10¹³ Ω cm. The ceramic fiber was fabricated to cloth and applied for electric wire insulator. The wire cable is flexible and can be applied at a high temperature atmosphere of around 1000°C.     

Effect of gamma radiation on the performance of jute fabrics-reinforced polypropylene composites

Jute fabrics-reinforced polypropylene (PP) composites (50% fiber) were prepared by compression molding. Composites were fabricated with non-irradiated jute fabrics/non-irradiated PP (C-0), non-irradiated jute fabrics/irradiated PP (C-1), irradiated jute fabrics/non-irradiated PP (C-2) and irradiated jute fabrics/irradiated PP (C-3). It was found that C-3 composite performed the best mechanical properties over other composites. Total radiation dose varied from 250–1000 krad and composites made of using 500 krad showed the best results. The optimized values (C-3 composites) for tensile strength (TS), bending strength (BS) and impact strength (IS) were found to be 63 MPa, 73 MPa and 2.93 kJ/m², respectively.     

Optimization of the curing conditions of PVC plastisols based on the use of an epoxidized fatty acid ester plasticizer

The use of an epoxidized fatty acid ester (EFAE) as a natural-based plasticizer for plasticized PVC (P-PVC) has been evaluated in this work. The effect of the curing conditions has been studied by following several test techniques such as mechanical properties, thermal behavior, color changes, solvent migration and microstructure. Different curing processes at isothermal conditions (ranging from 160 °C to 220 °C) have been carried at curing times in the 6–16 min range. The optimum mechanical response (tensile strength values in the 9–10 MPa range and elongation at break close to 250%) is obtained for plastisols cured at 200 and 220 °C for 12 and 8 min curing times, respectively. These curing conditions also offer the lowest migration in n-hexane (lower than 11%) which is indicative of plasticizer total absorption. Furthermore, the use of these curing conditions does not lead to thermal degradation as confirmed by color measurements.     

Polypropylene nanogel: “Myth or reality”

The objective of this work is the investigation of the nanogel and microgel formation in modified PP. The modified PP in pellets was synthesized by gamma irradiation of pristine PP under a crosslinking atmosphere of acetylene in dose of 5, 12.5 and 20 kGy, followed by thermal treatment for radical recombination and annihilation of the remaining radicals. The thin film gel of the polypropylenes was obtained by extraction in boiling xylene for period of 12 h at 138 °C, followed by decantation in beaker at room temperature of 25 °C with the total volatilization of the xylene and deposition of dried material film on glass substrate under agitation by Settling process. The thin film gel formed of pristine PP and modified PP (i.e., irradiated) was characterized using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and differential scanning calorimetry (DSC). The PP morphology indicated the nanogels and microgel formation with increase of spherulitic concentration and crystallinity at dose of 12.5 kGy.     

Evaluating of reinforcing effect of Ceratonia Siliqua for polypropylene: Tensile,flexural and other properties

The aim of this study is to investigate the reinforcing effect of Ceratonia siliqua (CS) powder as a novel natural filler for polypropylene (PP) based composites. CS powder up to 20 wt% was filled into PP matrix by using high speed thermo kinetic mixer. Mechanical and thermal properties of CS filled PP based composites were investigated by tensile and three point bending test, dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry analysis, fourier transform infrared analysis, and thermomechanical analysis. Morphology of the composites was also investigated by scanning electron microscopy. By filling 5% and 10% of CS into PP, tensile strength and flexural strength of PP increased by about 32 and 23%, respectively. This indicates that CS has a great potential to be used as reinforcing filler for PP composites. CS filling into PP led to lower coefficient of thermal expansion values which could help preventing the thermal expansion.     

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.     

Thermal and mechanical properties of irradiated poly(vinyl chloride)/calcium carbonate composite

A composite consisting of PVC and CaCO₃ particles was irradiated with different doses of Gamma rays or electron beam in order to compensate the tensile strength decreases by filler addition. The deployment of irradiation process on the composite improved significantly the tensile strength by about 10–20 % using E-beam and Gamma irradiation at a dose of 250 kGy, respectively. Moreover, the irradiated composite exhibited higher thermal stability. Two thermal dehydrochlorination processes after irradiation have been observed instead of three thermal process before. The calculation of the activation energy of each step showed that initiation step consumed about 60 % of the used energy.     

Isolation of cellulose fibers from kenaf using electron beam

Cellulose fibers were isolated from a kenaf bast fiber using a electron beam irradiation (EBI) treatment. The methods of isolation were based on a hot water treatment after EBI and two-step bleaching processes. FT-IR spectroscopy demonstrated that the content of lignin and hemicellulose in the bleached cellulose fibers treated with various EBI doses decreased with increasing doses of EBI. Specifically, the lignin in the bleached cellulose fibers treated at 300 kGy, was almost completely removed. Moreover, XRD analyses showed that the bleached cellulose fibers treated at 300 kGy presented the highest crystallinity of all the samples treated with EBI. Finally, the morphology of the bleached fiber was characterized by SEM imagery, and the studies showed that the separated degree of bleached cellulose fibers treated with various EBI doses increased with an increase of EBI dose, and the bleached cellulose fibers obtained by EBI treatment at 300 kGy was separated more uniformly than the bleached cellulose fiber obtained by alkali cooking with non-irradiated kenaf fiber.     

Degradation of poly(carbonate urethane) by gamma irradiation

Poly(carbonate urethane) (PCU), is a valuable commercial engineering polymer. In order to understand the possible use of PCU in radioactive waste management as a solidifying agent or as a disposal container, radiation stability of the PCU is studied by Co-60 gamma irradiations at two different dose rates of 1540 and 82.8 Gy/h. The total dose of irradiation was up to 6.24 MGy. Degradation nature was tested by studying the changes in mechanical and thermal properties with rate and total dose of irradiation. Ultimate tensile strength and toughness first increased and then decreased with the irradiation dose. Half value dose (HVD) for elongation was 4010 kGy and for tensile strength 6010 kGy at the dose rate of 1540 Gy/h. The non-irradiated PCU transparent color changed to yellow and then brown with increased irradiation dose. The FTIR spectral analysis showed a random scission of polymer with irradiation. From the experimental observation, it was shown that PCU can be used for embedding radioactive waste for about 300 years.     

Correlation of processing parameters and in situ temperatures for electron beam irradiated polycarbonate

Temperature measurements were performed for polycarbonate samples under electron beam irradiation for a total dose of 200 kGy at different dose fractionations. The samples were irradiated with a commercial electron beam accelerator and total dose was applied at different number of passes under the beam. Peak temperatures by beam heating obtained during irradiation varied significantly with different amounts of energy deposited per pass. For one-pass irradiation (200 kGy), the peak temperature recorded exceeded the polycarbonate's glass transition temperature.