Effects of electron beam irradiation on poly(butylene adipate)diol

Effects of electron beam (EB) irradiation on poly(butylene adipate)diol (PBAD) were studied by means of GPC, DSC, and X-ray diffractometry. Below 5 Mrad, chain scission predominantly occurs, while above 10 Mrad, crosslinking and chain scission take place in parallel. Structure of EB-irradiated PBAD is mainly characterized by the main reactions, degradation and crosslinking. Crystallinity of PBAD increased by EB irradiation. This phenomenon was explained by reorganization due to high molecular mobility of EB-irradiated PBAD. But, increment of crystallinity decreased with increasing dose because of formation of crosslinking, excessive degradation and thermal effect of EB. As the result, the crystallinity of EB-irradiated PBAD with a high dose becomes lower than that of original PBAD by thermal treatment.     

Synergistic effect of 4,4′‐bis(maleimido) diphenylmethane and zinc oxide on the vulcanization behavior and thermo‐mechanical properties of chlorinated isobutylene–isoprene rubber

It is well known that the vulcanization of chlorinated isobutylene–isoprene rubber (CIIR) with ZnO alone is very slow and the resulting vulcanizate shows low crosslinking density as well as poor mechanical and thermal properties. For these problems to be addressed, 4,4′‐bis(maleimido) diphenylmethane (BMDM) has been applied along with ZnO to cure CIIR. The curing behavior was investigated using oscillating disk rheometer and differential scanning calorimetry analysis. The crosslinking densities, mechanical, dynamic mechanical, and thermal properties of the vulcanizates were also evaluated as a function of BMDM content. From the rheometer and differential scanning calorimetry analysis, it has been confirmed that the rate of curing, as well as the extent of curing between CIIR and ZnO, has remarkably increased in the presence of BMDM. The Diels–Alder reaction between the in situ formed conjugated diene butyl from CIIR/ZnO with the maleic moieties of BMDM has been identified as a primary reason for the higher rate and state of cure. The crosslinking densities of the vulcanizate CIIR/ZnO have significantly increased with increase in the content of BMDM. As a result, the compression set of the vulcanizate was remarkably decreased at elevated temperature. Moreover, the vulcanizates contain BMDM that has exhibited high thermal degradation temperature and good retention of the mechanical properties even after 7 days of thermal ageing. Copyright © 2016 John Wiley & Sons, Ltd.     

Characterization of electron beam irradiation blends based on metallocene ethylene‐1‐octene copolymer

Binary blends using metallocene ethylene‐1‐octene copolymer as matrix were prepared and subjected to electron beam (EB) irradiation (50, 100, and 200 kGy). Gel content and melt flow index values indicated that the blends were crosslinking. Fourier transform infrared‐ATR spectroscopy was used to study the crosslinking and oxidative degradation of the blends via tertiary carbon and carboxyl group formation, respectively. Thermal and mechanical properties were studied showing that the crystallinity of both matrix and dispersed phase decreased with irradiation dose, and that the thermoplastic elastomers with good mechanical properties may be obtained by EB irradiation. Chain branching and scission were also detected at all irradiation doses, although at the highest doses (200 kGy) a crosslinking reaction was the most predominantly observed effect. The successive self‐nucleation annealing technique was used to determine the EB irradiation effects on crystallization of some blends in which crosslinking and chain branching take place, modifying the chain's structure and therefore crystalline regions in the matrix and the dispersed phase. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2432–2440, 2007     

IR Spectroscopic Study of Chemical Transformations upon Irradiation of the Poly(vinyl chloride)–Triallyl Cyanurate System

Chemical transformations resulting from irradiation of the poly(vinyl chloride) (PVC)–triallyl cyanurate (TAC) system were studied by IR spectroscopy. It was shown that crosslinking was accompanied by scission of the network structure formed in the initial dose range, and the scission process occurred even at small irradiation doses. The scission is assumed to be localized at the interface boundary between PVC and poly(iso-TAC) or poly(TAC).     

Characterization of irradiation-induced crosslink of epoxidised natural rubber/ethylene vinyl acetate (ENR-50/EVA) blend

The effect of irradiation on tensile, dynamic mechanical properties, thermal properties and morphology of ENR-50, EVA and ENR-50/EVA blend was investigated. All the samples were irradiated using a 3.0 MeV electron beam (EB) machine with doses ranging from 20 to 100 kGy. Results indicate that the gel fraction of ENR-50, EVA and ENR-50/EVA blend increases with irradiation dose. Concerning tensile properties, it can be seen that EB radiation increases the tensile strength of all the samples, increases the elongation at break of ENR-50 and ENR-50/EVA blend, reduces the elongation at break of EVA, increases M200 (modulus at 200% strain) of ENR-50 and EVA, while decreases M200 of the ENR-50/EVA blend. For dynamic mechanical studies, it was found that EB radiation increases the T_g of all the samples due to the effect of irradiation-induced crosslinking. The compatibility of ENR-50/EVA blend also found to be improving upon irradiation. In the case of thermal properties, it was detected that T_m, T_c and the degree of crystallinity of ENR-50/EVA blend increase with an increase in irradiation dose. This was due to the perfection in the crystal growth occurring upon radiation. Morphology changes play a major role in the changes of the properties of ENR-50/EVA blend. Finally, it can be concluded that ENR-50/EVA blend can be vulcanized by EB radiation.     

A 2-D tetrazole-based Zn(II) coordination polymer: crystal structure,dielectric constant,and luminescence

A tetrazole-based Zn(II) coordination polymer, [Zn(TMPT)₂] _n (1) (TMPT?=?5-(4-((1H-1,2,4-triazol-1-yl)methyl)phenyl)-2H-tetrazole), was synthesized by in situ reaction of 4-((1H-1,2,4-triazol-1-yl)methyl)benzonitrile, Zn(NO₃)_2?·?6H₂O, and NaN₃ under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Complex 1 contains π–π stacking interactions between tetrazole rings and phenyl rings of the 2-D ordered layered structural framework, which contribute to the dielectric response. In addition, 1 was demonstrated to display strong blue fluorescence emissions in the solid state at room temperature.     

Liquid natural rubber (LNR) as a compatibiliser in NR/LLDPE blends—II: the effects of electron-beam (EB) irradiation

Electron-beam (EB) irradiation technique has been used to improve the properties of 60/40 blends of NR/LLDPE in the presence of compatibilisers such as LNR-6 and LNR-16. Improvement in the physical properties of the blend correspond with the increase in the interactions created by EB irradiation as measured by gel content. For this blend ratio, the radiation dose of 200 kGy is found to be optimum. While LNR-6 shows some complimentary effects when it is used together with EB irradiation technique; LNR-16, however, causes an imperfection effect in the blend. The crosslinking process that takes place as a result of EB irradiation occurs at the expense of crystalline arrangement of the semi-crystalline LLDPE. For the morphological fixation purposes EB irradiation technique is found to be very effective.     

The effect of light intensity,film thickness,and monomer composition in styrene-based bioinspired polymers

Abstract

The effect of irradiation light intensity, film thickness, and polymer composition upon photo-irradiation of water-soluble polymers containing thymine was studied by ultraviolet (UV)-vis spectroscopy. Coatings of aqueous solution of the polymer on PET substrates were exposed to UV light at 254 nm through a standard mask. The effect of irradiation dose is similar to the typical behavior of photo-resists: the degree of crosslink increases over the time until it reaches saturation. The polymer composition effect shows an expected trend on the curing process, the more vinylbenzylthymine (VBT) content in the copolymer the higher the degree of crosslinking, a situation that agrees with the fact the VBT is the monomer playing the main role in the photo-reaction. It was observed that the effect of film thickness was as expected, the thicker the film the slower the immobilization of the polymer on the substrate. It was demonstrated that by varying these parameters one could control the crosslinking rate of the polymer.     

Photocrosslinking of polyethylene. I. Photoinitiators,crosslinking agent,and reaction kinetics

High density polyethylene has been photocrosslinked in the melt by using 4-chlorobenzophenone (4-CBP) as photoinitiator and triallylcyanurate (TAC) as crosslinking agent. Various factors affecting the crosslinking process (photoinitiator used and its concentration, irradiation temperature and time, atmosphere, UV light source, light intensity) were examined. By optimizing the irradiation conditions, it was found that samples up to 2 mm thick could readily be crosslinked to high gel content (≈ 90%) with satisfactory homogeneity within very short irradiation times (≈ 15 s). The kinetic analysis of the crosslinking process showed a linear relation between log S and log t (S is the sol fraction t is the irradiation time). An induction period was observed, the length of which decreased with increasing concentration of 4-CBP and increasing light intensity. An upper limit of gel content was also found for long irradiation times at a level depending on the concentration of 4-CBP. The crosslinking rate was proportional to the second order of light intensity at lower intensity and changed to first order at higher light intensity. A mechanism based on the recombination of chain radicals through both allyl and alkyl type radicals of TAC was proposed.     

Effect of electron beam radiation dose on the foam formation in pre-ceramic polymer

Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9 MGy and dose rate of 2.8 kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the poly-condensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0 MGy radiation dose. Methylsilicone foams were pyrolysed in N₂ atmosphere at temperatures of 1200 and 1500 °C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of ~84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300 μm and density of about 0.31 g cm^?3.     

Modelling molecular weight changes induced in polydimethylsiloxane by gamma and electron beam irradiation

A commercial linear polydimethylsiloxane (PDMS) was subject to gamma irradiation under vacuum and in air, as well as to accelerated electron beam radiolysis (EB). All irradiation treatments were done at room temperature. The molecular weight changes induced by the radiation processes have been investigated using size exclusion chromatography (SEC) with refraction index (RI) and multi angle laser light scattering (MALLS) detectors to obtain the number and weight average molecular weights of the irradiated samples.

The analysis of the data indicates that crosslinking reactions predominated over scission reactions in all cases. Gamma irradiation under vacuum was the most efficient process within the analyzed dose range, reaching the gel point earlier. Irradiation in the presence of oxygen induces oxidative effects, both in gamma and EB irradiations. A previously developed mathematical model of the irradiation process that accounts for simultaneous scission and crosslinking and allows for both H and Y crosslinks fitted well the measured molecular weight data.     

Preparation of N-doped and oxygen-deficient TiO2 microspheres via a novel electron beam-assisted method

Nitrogen-doped and oxygen-deficient TiO₂ microspheres (NT) with large specific surface were prepared by a solvothermal method and following with electron beam (EB) irradiation under various doses (140–500 kGy). XPS results show that under the EB irradiation, nitrogen ions have been doped into the TiO₂ lattice successfully, as well as part of Ti⁴⁺ on the surface of the samples changed to Ti³⁺. Photocatalytic performance was tested by decomposing Rhodamine B in the aqueous phase under visible light irradiation. The prepared materials under the EB irradiation at dose of 140 kGy (NT-140) exhibit the best visible light photocatalytic activity. It is attributed to the large specific surface (138.4 m²/g) and a synergistic effect between substitutional nitrogen dopants and oxygen defects in NT-140. The results obtained may provide a new sight for the application of EB-assisted preparation of nanomaterials.     

RADIATION INDUCED ACRYLAMIDE/CITRIC ACID HYDROGELS AND THEIR SWELLING BEHAVIORS

Citric acid (CAc) moieties containing acrylamide (AAm) hydrogels were prepared by gamma irradiation of their aqueous solutions. A possible polymerization and crosslinking mechanism for acrylamide/citric acid (AAm/CAc) hydrogels is proposed. The effects of irradiation dose and citric acid content on swelling behavior were investigated. Swelling took place in water at 25°C and was followed gravimetrically. Incorporation of a relatively low amount of citric acid to acrylamide hydrogel increased its swelling up to 950% from 700%. The diffusion of water into AAm/CAc hydrogels was found to be a non-Fickian type. Diffusion coefficients of AAm/CAc hydrogels found as 5 × 10^?7? 10 × 10^?7 cm² sec^?1. It has also been found that the number average molar mass between crosslinks is increased with the CAc content and decreased with irradiation dose.     

Degradation and stability of polyaniline on exposure to electron beam irradiation (structure-property relationship)

Polyaniline (PAni) was prepared by electrochemical polymerization and subjected to different doses of electron beam (EB) irradiation. The effect of EB irradiation causes both chain scission and cross-linking process in PAni, which depends on irradiation dose. The degree of chain scission and cross-linking in PAni by EB irradiation is characterized through XRD, TGA, DSC, solubility, EPR and electrical properties measurement. The results reveal that with increase in EB irradiation dose from 0 to 150 kGy DC and AC conductivity and dielectric constant are found to increase mainly due to the chain scission or further doping in PAni. Due to irradiation there is change in the structure of PAni, such as decrease in the d-spacing, inter-chain separation, thermal stability and T_g but increase in the percent crystallinity and solubility. With further increase in the EB irradiation dose from 150 kGy onwards the DC and AC conductivity and dielectric constant are decreased due to the cross-link formation or dedoping in PAni, which causes the decrease in percentage of crystallinity and solubility and increase in d-spacing, inter-chain separation, thermal stability and T_g of PAni.     

Optimization of electron beam crosslinking of wire and cable insulation

The computer simulations based on Monte Carlo (MC) method and the ModeCEB software were carried out in connection with electron beam (EB) radiation set-up for crosslinking of electric wire and cable insulation. The theoretical predictions for absorbed dose distribution in irradiated electric insulation induced by scanned EB were compared to the experimental results of irradiation that was carried out in the experimental set-up based on ILU 6 electron accelerator with electron energy 0.5–2.0 MeV.The computer simulation of the dose distributions in two-sided irradiation system by a scanned electron beam in multilayer circular objects was performed for various process parameters, namely electric wire and cable geometry (thickness of insulation layers and copper wire diameter), type of polymer insulation, electron energy, energy spread and geometry of electron beam, electric wire and cable layout in irradiation zone. The geometry of electron beam distribution in the irradiation zone was measured using CTA and PVC foil dosimeters for available electron energy range. The temperature rise of the irradiated electric wire and irradiation homogeneity were evaluated for different experimental conditions to optimize technological process parameters. The results of computer simulation are consistent with the experimental data of dose distribution evaluated by gel-fraction measurements. Such conformity indicates that ModeCEB computer simulation is reliable and sufficient for optimization absorbed dose distribution in the multi-layer circular objects irradiated with scanned electron beams.     

Radiation crosslinking of polymethylhydrogensiloxane containing methoxy groups

The bulk viscosity of polymethylhydrogensiloxane containing methoxy groups (PMHS-A) was measured before and after irradiation. The gel point was then determined from the variation of viscosity by irradiation by comparing it with methoxy-free polymethylhydrogensiloxane (PMHS-B) and polydimethylsiloxane blocked by methoxyldimethylsilyl (PDMS-C) or trimethylsilyl (PDMS-D). The following results were obtained: (1) The G value of crosslinking by irradiation is 167, 52, 25, and 3 for PMHS-A, PMHS-B, PDMS-C, and PDMS-D, respectively. (2) The scission of the SiO? CH₃ bond is easier than that of the Si? H, Si? CH₃, or SiCH₂? H bond. The SiO? CH₃ bond is PMHS-A is severed from SiO· and ·CH₃ to induce chain reactions at the initial stage by irradiation. (3) It was confirmed that the commercial PMHS is at present free of methoxy groups. To replace the hydrogen of Si? H in the commercial PMHS with methoxy groups heat treatment with methanol was performed by which the G value of crosslinking was increased.     

Effect of organoclay loading and electron beam irradiation on the physico‐mechanical properties of low‐density polyethylene/ethylene‐vinyl acetate blend

The influence of electron beam (EB) irradiation and organoclay (OC) loading on the properties of low‐density polyethylene (LDPE)/ethylene‐vinyl acetate (EVA) blends was investigated. The samples were subjected to the EB irradiation with the dose values of 50 and 250 kGy. X‐ray diffraction (XRD), gel content, mechanical, thermal, and electrical properties were utilized to analyze the characteristics of the LDPE/EVA blends with and without OC at different irradiation dosages. Gel content analysis showed that the OC promotes considerably the insoluble part so that the LDPE/EVA blends filled with OC become fully crosslinked at 250 kGy; possibly through the formation of further crosslinks between OC and polymer chains. The samples irradiated by EB showed enhanced mechanical properties due to the formation of three‐dimensional networks. In addition, thermogravimetric analysis indicated that combined OC loading and radiation‐induced crosslinking improved thermal stability of LDPE/EVA blends considerably. Copyright © 2011 John Wiley & Sons, Ltd.     

γ-radiation-induced crosslinking of polystyrene

The γ-radiation-induced crosslinking of polystyrene was studied at 30–100°C in vacuo with a dose rate of 6.35 × 10⁵ rad/hr. The amount of hydrogen formation increased with increasing irradiation time, and the rate of the formation decreased with the time. The results were well described by the zero-order formation kinetics with respect to the hydrogen concentration combined with the first-order disappearance. The apparent rate constant for the formation of hydrogen increased somewhat with rising irradiation temperature, and the one for the disappearance was little affected by the temperature. The gel fraction increased with the time by the irradiation beyond the critical time for incipient gel formation, and the rate of gel formation decreased with the time. The gel formation was retarded by rising irradiation temperature, and only a little gel fraction was observed at 100°C. The G values for the crosslinking and main-chain scission were obtained from the gel data by using the Charlesby–Pinner equation. On the basis of these results, the mechanism of the γ-radiation-induced crosslinking of polystyrene was discussed.     

Comparison of electron beam and gamma ray irradiations effects on ruminal crude protein and amino acid degradation kinetics,and in vitro digestibility of cottonseed meal

This study was conducted to compare effects of electron beam (EB) and gamma ray (GR) treatments at doses of 25, 50 and 75 kGy on ruminal degradation kinetics of crude protein (CP), amino acid (AA), and in vitro digestibility of cottonseed meal (CSM). Ionizing radiations of EB and GR had significant effects (P<0.05) on CP and AA ruminal degradability characteristics of CSM. Effective ruminal degradability (ERD) of CP was lower in EB and GR irradiated CSM (P<0.05) than in unirradiated CSM. GR and EB treatments had the same effects on ERD decreasing of CP (P>0.05). Irradiation processing caused decrement in AA degradation after 16 h of ruminal incubation (P<0.05). EB irradiation was more effective than GR irradiation in lessening the ruminal degradability of AA (P<0.05). EB and GR treatments at a dose of 75 kGy increased in vitro digestibility of CSM numerically. This study showed that EB could cause CP and AA bypass rumen as well as GR. Therefore, ionizing irradiation processing can be used as an efficient method in improving nutritional value of CSM.     

Oxidation of gaseous styrene by electron beam irradiation

In this research, the absorbed dose, background gases, relative humidity, and initial concentrations were selected as control factors to discover decomposition characteristics of styrene using electron beam irradiation. It was confirmed that a considerable amount of styrene was removed by primary electrons as well as radicals and ions, which were produced after the electron beam irradiation. Moreover, the removal efficiencies of styrene were observed to rise when the initial concentration was lower, moisture content was higher, and the absorbed dose increased. For instance, 50 ppmv styrene showed extremely high removal efficiency (over 98%) at a condition of 2.5 kGy. A small amount of styrene oxide, benzaldehyde, aerosol, CO, and CO₂ were produced as by-products after EB irradiation.