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Abstract This study aims to develop a series of cation exchange hydrogel resins via gamma irradiation technique through copolymerizing styrene sodium sulfonate with three acrylamide derivatives (designated as poly(X-co-styrene sodium sulfonate), where X refers to acrylamide (PAASS), methacrylamide (PMASS), and isopropyl acrylamide (PIASS)). The prepared hydrogel resins were characterized and tested for the adsorption removal of hard/scale metal cations (e.g., Ca2+, Mg2+, Ba2+, and Sr2+) from saline water under varying conditions. Results demonstrated that PMASS and PIASS displayed closed porous networks with a significant pH-responsive swelling behavior, increasing from 1.41 to 5.62 g/g in acidic conditions and approximately 41.49 to 45.83 g/g under neutral conditions swelling ratios, while PAASS exhibited an open porous network structure with the stable swelling ratio of around 35 g/g within mild and neutral pH ranges. All hydrogel resins also showed rapid initial adsorption of Ca2+ > Mg2+ > Ba2+ > Sr2+, depending on ionic metal size, with adsorption equilibrium within 3–6 h. Maximum removal was achieved at neutral-basic pH when sulfonate groups were fully deprotonated with a total capacity of about ~ 147–175 mg/g overall mixed metal ions. When exposed to lower concentration solutions, about 87% of metal ions were effectively removed.

This study aims to develop a series of cation exchange hydrogel resins via gamma irradiation technique through copolymerizing styrene sodium sulfonate with three acrylamide derivatives (designated as poly(X-co-styrene sodium sulfonate), where X refers to acrylamide (PAASS), methacrylamide (PMASS), and isopropyl acrylamide (PIASS)). The prepared hydrogel resins were characterized and tested for the adsorption removal of hard/scale metal cations (e.g., Ca2+, Mg2+, Ba2+, and Sr2+) from saline water under varying conditions. Results demonstrated that PMASS and PIASS displayed closed porous networks with a significant pH-responsive swelling behavior, increasing from 1.41 to 5.62 g/g in acidic conditions and approximately 41.49 to 45.83 g/g under neutral conditions swelling ratios, while PAASS exhibited an open porous network structure with the stable swelling ratio of around 35 g/g within mild and neutral pH ranges. All hydrogel resins also showed rapid initial adsorption of Ca2+ > Mg2+ > Ba2+ > Sr2+, depending on ionic metal size, with adsorption equilibrium within 3–6 h. Maximum removal was achieved at neutral-basic pH when sulfonate groups were fully deprotonated with a total capacity of about ~ 147–175 mg/g overall mixed metal ions. When exposed to lower concentration solutions, about 87% of metal ions were effectively removed. [ABSTRACT FROM AUTHOR]

This research utilized organic acids in different concentrations as crosslinking agents with polyvinyl alcohol (PVA) to induce an esterification reaction for lindur (Bruguiera gymnorrhiza) fruit flour-based hydrogels. The aim was to discover the impact of different organic acids, namely lactic and acetic acids, on physical, mechanical, and antibacterial activity against Staphylococcus aureus on hydrogels. The concentration variations of lactic acid and acetic acid used were 6%, 8%, and 10% (w/v). The characteristics of the physical properties test (swelling index, gel fraction, pH, thickness) indicate its classification as a superabsorbent material. The characteristics of the mechanical properties test (tensile strength, elongation, foldability) indicate that hydrogels meet mechanical standards for human skin. Adding lactic acid demonstrated the most significant bacterial inhibition against S. aureus among the analyzed hydrogels. Hydrogel, with the addition of organic acids, especially lactic and acetic acids, holds the promise of enhancing the inherent qualities of hydrogels for potential application as a wound dressing. [ABSTRACT FROM AUTHOR]

In order to determine the influence of the nature of the solvent on the molecular weight, copolymers of styrene and maleic anhydride (SMA) and terpolymers of styrene, maleic anhydride and acrylonitrile (SMN) were synthesized. The synthesis was carried out by the method of radical polymerization in individual solvents or their mixtures, having solvent parameters according to Hildebrand δi in the range of 18.3÷20.55 MJ-0.5m-1.5. The research objects were selected due to the presence of reactive anhydride cycles in the polymer chains. It is shown that the degree of polymerization of the synthesized compounds can be estimated by the closeness of the contributions of the associative solubility parameters δa/δ to the corresponding solubility parameters of the polymer δ2 and the solvent δ1. The value of the solubility parameters was calculated based on the three-dimensional concept of the solubility parameter of M. Hansen and using the method of A. Askadskii. On the basis of synthesized polymer compounds and commercial block copolymers of ethylene oxide and propylene oxide, film flexible materials with ion exchange properties were obtained, in which the static exchange capacity is (4.28÷6.37) meq/g. It was determined that the content of the gel fraction of the materials is (86÷97)% and depends on the nature of the solvent from which the films are obtained, and the increase in the content of the gel fraction is facilitated by the closeness of the δα/δ values of the solvent and SMA/SMN. The ability of film materials to swell was investigated. It was determined that at pH > 6, the degree of swelling increases in leaps and bounds, and the dynamics of swelling and its maximum value depends on the static exchange capacity and the content of oxyethylene component links in the mesh structure. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Poly (vinyl alcohol) is blended with ethylene glycol by casting method to form PVA-EG blend films. These films were irradiated by both N2 ion beam extracted from dc ion source at different ion fluences and γ-rays with various irradiation doses. The effects of ion beam and γ-rays irradiation on the thermal, micro-hardness, and gel fraction properties of PVA-EG blend films were investigated. The gel fraction % and micro-hardness increase with increasing the γ-rays doses up to 150 kGy and then decreased, where they increased at all fluences of ion beam irradiation. The improvement in the gel fraction percentage and micro-hardness suggest that PVA-EG blend films exhibited a crosslink density. The thermal behavior was examined by thermogravimetric analysis and it shows different thermal patterns depending on the type and dose of radiation. The thermal stability parameters of γ-rays- and ion beam-irradiated PVA-EG samples were evaluated using the Ti, Ts, T0.5, Tf temperatures, and activation energy (Ea) values. The thermal stability parameters were dependent on both the type and extent of irradiation dose and fluence. Finally, there is a good agreement between the obtained results from different measurement techniques. [ABSTRACT FROM AUTHOR]

A versatile one‐step synthesis of surface‐attached polymer networks using small bifunctional gelators (SBG), namely 4‐azidosulfonylphenethyltrimethoxysilane (4‐ASPTMS) and 6‐azidosulfonylhexyltriethoxysilane (6‐ASHTES) is reported. A thin layer (≈200 nm) of a mixture comprising ≈90% precursor polymer and 10% of 4‐ASPTMS or 10% 6‐ASHTES on a silicon wafer is deposited. Upon UV irradiation (≈l–254 nm) or annealing (>100 °C) layers, sulfonyl azides (SAz) release nitrogen by forming singlet and triplet nitrenes that concurrently react with any C─H bond in the vicinity resulting in sulfonamide crosslinks. Condensation among tri‐alkoxy groups (i.e., methoxy or ethoxy) in bulk connects the SBG units, which completes the crosslinking. Concurrently, when such functionalities react with hydroxyl groups at the surface, which enable the covalent attachment of the crosslinked polymer chains. A systematic investigation on reaction mechanism and gel formation using spectroscopic ellipsometry (SE) and Fourier‐transform infrared spectroscopy in the attenuated total reflection mode (FTIR‐ATR) is performed. Analogous thermally initiated gelation for both 4‐ASPTMS and 6‐ASHTES is found. The 6‐ASHTES is UV inactive at ≈l–254 nm, while the 4‐ASPTMS is active and forms gels. The difference is attributed to the aromatic nature of 4‐ASPTMS that absorb UV light at ≈l–254 nm due to π–π* transition. [ABSTRACT FROM AUTHOR]

Superabsorbent polymers (SAPs) were synthesized by aqueous solution polymerization of carboxymethyl cellulose (CMC)/acrylic acid (AAc) and polyvinyl alcohol (PVA)/AAc blend using benzoyl peroxide as an initiator. SAPs were synthesized by a facile method under mild conditions. A comparative study was done between CMC/AAc as a biodegradable superabsorbent and PVA/AAc copolymer. The effects of cross-linking, reaction time, temperature, and initiator molar ratio on water absorbency were studied herein. The highest swelling capacity was obtained for CMC/AAc biodegradable superabsorbent composite. The water absorption capacity of SAPs increased with increases in benzoyl peroxide content, immersion time, and reaction temperature of polymerization. The gel fraction of SAPs decreased with increases in the amounts of N, N ′-methylenebisacrylamide as a cross-linker. Fourier-transform infrared spectroscopy was used to examine the molecular interactions. The morphology and structure of superabsorbent composites were investigated by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The possibility of using of alkoxysilanes, containing various functional groups, as structuring agents of ethylene copolymers was studied and their influence on the properties of binary and ternary ethylene copolymers was revealed. [ABSTRACT FROM AUTHOR]

The influence of bentonite concentration on the main physicochemical and physicomechanical properties is studied for nanocomposites based on primary polyethylene and high-density polyethylene functionalized with methacrylic acid. The sizing of bentonite nanoparticles with γ-aminopropyltriethoxysilane is shown to substantially improve the operational characteristics of nanocomposites. [ABSTRACT FROM AUTHOR]

Graphical abstract Stacked actuators with 30 layers based on a customized silicone elastomer and carbon black have been fabricated and deeply investigated in terms of electromechanical properties. From 0.01 Hz, to 10 Hz the fabricated actuators show excellent electromechanical response even though the actuator is loaded with 5 kg. Highlights • Silicone elastomer with Young's modulus as low as 0.07 MPa. • Gel fraction impact on electromechanical response. • Comparative evaluation of different planar actuators. • The actuator Young's modulus depends on applied voltage. • Silicone-based actuator can lift substantial weights. Abstract Dielectric elastomer transducers (DETs) consisting of thin elastomeric membranes trapped between two electrodes are emerging technology for electromechanical soft actuators, sensors and energy harvesters. Among the current challenges in DE actuators are the reduction of driving voltage by acting on the mechanical and dielectric properties of the active membrane, by ensuring a good dielectric-electrode compliance or by optimal configuration of the device. Taking into account the significant influence of the Young's modulus on the actuation strain, in this paper, a silicone elastomer customized in terms of molecular weight and crosslinking pattern was prepared and characterized. By appropriate testing, it was found the optimal carbon black-based electrode formulation and both single layer and 30-layer stacked actuators (DET-Si-cb-30) were built. While the former was electromechanically evaluated by measuring the lateral actuation strain, the contractive actuation strain was measured for the stacked array. The stacked arrangement was evaluated by two nonconventional protocols for the DETs field: shearing behavior using a "resonant column" and actuation force by attachment of different weights. Comparison of results with those obtained on similar configurations based on recognized dielectric elastomers (Elastosil and VHB-4910) as references, evaluated under identical conditions, highlights superior capabilities of DET-Si actuator. Thus, DET-Si-cb-30 can lift 250 times its weight at only 20 V·µm−1 while Elastosil-cb-30 can lift 220 times and VHB-200%-cb-30 10 times its weight. [ABSTRACT FROM AUTHOR]

Dissolved oil palm empty fruit bunch (EFB) cellulose in NaOH/urea solvent was mixed with sodium carboxymethylcellulose (NaCMC) to form a green regenerated superabsorbent hydrogel. The effect of concentration of epichlorohydrin (ECH) as the crosslinker on the formation, physical, and chemical properties of hydrogel was studied. Rapid formation and higher gel content of hydrogel were observed at 10% concentration of ECH. The superabsorbent hydrogel was successfully fabricated in this study with the swelling ability >100,000%. Hydrogel with higher concentration of ECH showed opposite trend by having higher superabsorbent property than that of lower concentration. The covalent bond of C O C was observed with Attenuated total reflectance fourier transform infrared (ATR-FT-IR) spectroscopy to confirm the occurrence of crosslinking. The physical and chemical properties of hydrogel were affected by swelling phenomenon. Hydrogel with higher degree of swelling exhibited lower moisture retention and higher transparency. Moreover, the weight of the superabsorbent hydrogel increased with the decrement of pH value of external media (distilled water). This study provided substantial information on the effect of different percentage of ECH as crosslinker on hydrogel basic properties. Furthermore, this study affords correlation of many essential driving forces that affected hydrogel superabsorbent property. [ABSTRACT FROM AUTHOR]

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of the total absorbed radiation dose on the content of the gel fraction of polymer hydrogels, received by radiation co-polymerizing of N-vinylpyrrolidone and methacrylatein in the presence of a di-vinyl cross-linking agent, and ion exchange resins, has been studied. It is shown that at the absorbed dose of 35 kGy the maximum degree of monomers conversion is achieved, which is 85 – 88 % for ion-exchange polymers and 97.5 % for base co-polymer. Quantitative estimation of hydrogels expansionhas been performed and shows that in the absorbed doses in the range from 25 to 40 kGy the parameters of three-dimensional grid do not change.

Ultra-high pressure water jet is proposed for recycling of vulcanized waste rubber, and cavitation desulfurization in the recycling process is analyzed. The chemical effects of mechanical shearing, pyrolysis, free radical oxidation, and supercritical oxidation produced by bubble collapse are considered the main causes of desulfurization. Scanning electron microscopy, Fourier transform infrared spectrometry, differential scanning calorimetry, nuclear magnetic resonance test, and X-ray photoelectron spectroscopy are used to determine the performance of rubber powder. Gel fraction of rubber powder is measured to analyze the effect of jet pressure on desulfurization. Results indicate that the vulcanized rubber could achieve partial desulfurization. The glass transition temperature of the rubber powder slightly increases after crushing. With the increase of jet pressure, the gel fraction of rubber powder initially decreases and then increases, as well as achieves a minimum value at the jet pressure of nearly 220 MPa, which is ideal for desulfurization. [ABSTRACT FROM AUTHOR]

A hybrid organic-organic urethane acrylate oligomer was synthesized by the reaction of polypropyleneglycol (PPG),2,4-toluene diisocyanate (TDI) and 2-hydroxyethyl methacrylate (HEMA) using dibutyltin dilaurate (DBTDL) as a catalyst.The urethane acrylate oligomer’s structure was characterized by nuclear magnetic resonance (NMR) and Fourier transforminfrared spectroscopy (FT-IR). Two UV-curable coatings were prepared by blending the urethane acrylate oligomer, a reactivemonomer (1,6- hexanediol diacrylate (HDDA) or trimethylol propane triacrylate (TMPTA)) and a photoinitiator (2,2-dimethoxy-2-phenyl acetophenone). The UV curing process of such coatings was monitored by FT-IR and determination of thegel fraction. It was found that as the UV dose increased, the specific peaks at 1635 cm-1 and 810 cm-1, related to the carboncarbondouble (C=C) bond, decreased. Gel fraction of the cured coating film was found to increase with increasing radiationtime. Thermal properties of the cured coating were also investigated using differential scanning calorimetry (DSC) andthermal gravimetric analysis (TGA).

Investigation of the effect of electron radiation and triallyl isocyanurate (TAIC) on the mass melt flow rate, average molecular weight, density, mechanical properties, as well as formation of the gel fraction of poly(butylene adipate-co-terephthalate) (PBAT) was the main objective of the present work. It was found that irradiation of PBAT by electron radiation causes mutual linking of PBAT macromolecules at chain ends or create branched structures. At the same time, the gel fraction does not form and inhibition of flow does not occur. It was also found that PBAT irradiated in the presence of TAIC underwent crosslinking resulting in formation of a significant amount of the gel fraction. Moreover, TAIC by itself does not cause crosslinking of this polymer. It grows also tensile strength and density of irradiated samples containing TAIC, and the elongation at break decreased. The extent of observed changes essentially depends on the magnitude of the electron radiation dose. [ABSTRACT FROM AUTHOR]

The efficiency of polyfunctional monomers as cross-linking co-agents on the chemical properties of natural rubber vulcanized by electron beam irradiation was studied. The following polyfunctional monomers were used: trimethylolpropane-trimethacrylate, zinc-diacrylate, ethylene glycol dimethacrylate, triallylcyanurate and triallylisocyanurate. The electron beam treatment was done using irradiation doses in the range of 75 kGy-300 kGy. The gel fraction, crosslink density and effects of different aqueous solutions, by absorption tests, have been investigated as a function of polyfunctional monomers type and absorbed dose. The samples gel fraction and crosslink density were determined on the basis of equilibrium solvent-swelling measurements by applying the modified Flory-Rehner equation for tetra functional networks. The absorption tests were done in accordance with the SR ISI 1817:2015 using distilled water, acetic acid (10%), sodium hydroxide (1%), ethylic alcohol (96%), physiological serum (sodium chloride 0.9%) and glucose (glucose monohydrate 10%). The samples structure and morphology were investigated by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy techniques. [ABSTRACT FROM AUTHOR]

Comparison of some changes occurring in polylactide (PLA) due to high energy β-radiation and addition of triallyl isocyanurate (TAIC) was the main objective of the present study. It was found that irradiation of PLA by high energy β-radiation causes essential changes in its properties, that undergoes mainly degradation, to form a porous structure. The PLA degradation can be diminished by introduction into the polymer matrix of a low-molecular mass multifunctional compound like TAIC. Upon the electron radiation, effective crosslinking of PLA by TAIC occurs. Application of TAIC favorably influences hindering of the PLA degradation or, when the doses are very large, diminishes worsening of the PLA functional qualities. It was also found that the optimum crosslinking of PLA is obtained when the electron radiation doses of the range of 40–200 kGy are applied and the amount of TAIC equal 3–5 wt% is used. [ABSTRACT FROM AUTHOR]

Far-infrared absorption spectra were measured for low density polyethylene in a frequency range from 3.0 to 120 THz. When the polyethylene was cross-linked using vinyl silane, the absorption was found to increase in proportion to the cross-linking degree at 13.2, 30.9, and 32.7 THz, where absorption attributable to Si-O bonds appears. Therefore, the degree of cross-linking of polyethylene by vinyl silane can be estimated by far-infrared absorption spectroscopy. [ABSTRACT FROM PUBLISHER]

The effect of multifunctional monomers or oligomers (MFM/O) additives on electron beam (E-beam) radiation induced crosslinking of poly (styrene- block -isoprene/butadiene- block -styrene) (SIBS) was studied. Ten types of MFM/O were investigated, including trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), triallyl cyanurate (TAC), polybutadiene diacrylate (PB-diacrylate), ethylene glycol dimethylacrylate (EGDMA), butylene glycol dimethacrylate (BGDMA), 1,2-polybutadiene. The effects of MFM/O concentration and E-beam radiation dose on properties of SIBS were studied including tensile strength, elongation-at-break, modulus, gel content, equilibrium swelling and crosslink density. TMPTA significantly improved the tensile modulus and crosslink density of SIBS. SIBS with TMPTMA and TMTPMA with inhibitor showed a 50% increase in tensile strength. The solubility of MFM/O in SIBS was also investigated by a selective swelling method. The MFM/O were found to be soluble in both phases of SIBS. The viscosity of SIBS with methacrylate type MFM/O was stable at 200 °C. [ABSTRACT FROM AUTHOR]

Alginate tubular fiber has been successfully prepared via coaxial fluid crosslink mode, which is potentially used for the construction of vascularized tissue engineering scaffolds (VTES). However, its elastic and smooth surface is negative for the adhesion of fibers. In this study, the gel fractions were controlled in a novel way of two-step crosslink process in order to meet the needs of each processing link. Based on such consideration, an appropriate formulation was selected to direct write single fiber, which ensured the tubular structure with enough gel portion as well as adhesion between fibers with the reserved sol. Finally, the integrity of the scaffolds had a further development within the 2nd crosslink bath process, which would help to solve the question of poor shear resistance for hydrogel scaffolds. [ABSTRACT FROM AUTHOR]

Investigation of the effect of electron radiation on the flow rate and average molecular weight of poly( ε-caprolactone) (PCL) as well as on formation of the gel fraction of this polymer being irradiated in the presence of triallyl isocyanurate (TAIC) was the aim of the present paper. It was found that PCL macromolecules upon the electron radiation underwent both degradation and linking, because of which the polymer molecular weight increased. The processes associated with elongation of the polymer chains prevailed over the degradation ones. It was also found that PCL irradiated in the presence of TAIC underwent crosslinking resulting in formation of a significant amount of the gel fraction. The largest amount of this fraction was created upon the radiation with the dose of 60 kGy, which was confirmed by the results of determination of the swelling index. Changes in properties of PCL, occurring because of the electron radiation, are important for controlling viscosity of polymeric materials during processing of these materials. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Superabsorbent polymers (SAPs) were synthesised from an aqueous solution of a carboxymethylcellulose (CMC)/acrylic acid (AAc) blend followed by neutralisation with alkali using Co-60 γ-irradiation source at room temperature (~27°C). The preparation conditions, such as the irradiation dose and the variation of the CMC to AAc ratio (10:1.5, 1.0:2.0 and 1.0:3.0) in the feed solution, were investigated. Fourier Transform Infra-Red (FTIR) spectroscopy was used to investigate the molecular interactions of CMC/AAc SAP. The influence of the radiation dose and the concentration of AAc on the gel content and the swelling behaviour was also investigated. The gel fraction of SAP increases with an increase in the radiation dose and the concentration of each component and attains maximum value at a 5 kGy radiation dose. The water absorption capacity of SAP decreases with an increased radiation dose and AAc content. SAP enhances the water retention of sand and soil. SAP also influences germination of wheat and lady's finger seeds and the growth of young plants. The biodegradation of SAPs was also investigated. [ABSTRACT FROM AUTHOR]

Ultra high molecular weight polyethylene (UHMWPE) containing benzophenone (BP) is photocrosslinked under continuous UV irradiation. BP addition as low as 0.77 mol% per repeating unit of UHMWPE is enough to increase the gel fraction up to 99.8 %. The crosslinks are formed through the recombination of methine radicals generated from the hydrogen abstraction of UHMWPE by the excited BP. The heat of fusion of UHMWPE reduces substantially and the peak decomposition temperature increases as much as 15.8 oC due to the crosslinked network, coupled with slight decrease in crystallinity. The tensile strength, modulus and toughness of the crosslinked UHMWPE film are significantly improved with increasing crosslinking density. The wear rate of the UHMWPE also remarkably decreases from 10.2 mg/million cycles to 1.9 mg/million cycles, which can minimize the wear of total hip joint anthroplasty bearings. [ABSTRACT FROM AUTHOR]

Poly(ethylene oxide) (PEO) films are photocrosslinked by continuous UV irradiation without photoinitiators. Maximum gel fraction and swelling of the photocrosslinked PEO films reach up to about 38.8% and 2824%, respectively. From NMR analysis, the photocrosslinking mechanism of PEO can be attributed to recombination between methine radicals, which are generated from the polymer chain by hydrogen abstraction. However, the relatively low degree of crosslinking is attributed to more facile photooxidation of the generated radicals and concomitant photo-scission of the crosslinks. Depth-gradient crosslinked structure can be formed by inherent UV absorption and successive photoscission of the crosslinked polymer surface, which can be made uniform by adjusting UV energy. The photocrosslinked PEO shows the higher glass transition temperature as much as 7.3°C coupled with significantly enhanced storage modulus and thermal stability. The lower crystallinity causes by the reduced recrystallizability of the crosslinked polymer chains in melt. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Thin films of 1,2–polybutadiene were crosslinked by exposure to filtered UV (ultraviolet) radiation at 365 nm in the presence of benzophenone (BP) as photoinitiator. By means of FTIR (Fourier transform infrared) spectra recorded during irradiation, the partial loss of both unsaturation and allylic hydrogen was observed. The photoreduction of BP was continuously monitored through the infrared absorption of its carbonyl bonds at 1665 cm−1. The presence of a labile hydrogen atom, as well as of the vinyl group, ensured different reactivity toward triplet BP and led to a structural variety of the photoproducts, from which the main chemical reactions leading to photocrosslinking of 1,2-polybutadiene could be deduced. It was found that the homopolymerization of vinyl groups takes place simultaneously with the BP—induced crosslinking and that all BP originating products are bonded into the network of crosslinked chains. The obtained networks were characterized with respect to their insolubility and structural properties. [ABSTRACT FROM PUBLISHER]

A hybrid organic-organic urethane acrylate oligomer was synthesized by the reaction of polypropyleneglycol (PPG), 2,4-toluene diisocyanate (TDI) and 2-hydroxyethyl methacrylate (HEMA) using dibutyltin dilaurate (DBTDL) as a catalyst. The urethane acrylate oligomer's structure was characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR). Two UV-curable coatings were prepared by blending the urethane acrylate oligomer, a reactive monomer (1,6- hexanediol diacrylate (HDDA) or trimethylol propane triacrylate (TMPTA)) and a photoinitiator (2,2-dimethoxy-2-phenyl acetophenone). The UV curing process of such coatings was monitored by FT-IR and determination of the gel fraction. It was found that as the UV dose increased, the specific peaks at 1635 cm-1 and 810 cm-1, related to the carbon- carbon double (C=C) bond, decreased. Gel fraction of the cured coating film was found to increase with increasing radiation time. Thermal properties of the cured coating were also investigated using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). [ABSTRACT FROM AUTHOR]

Abstract: The effect of gamma ray irradiation on ultra-high molecular weight polyethylene (UHMW-PE) fibre was investigated for the change of gel fraction, mechanical properties, and morphology of crystallites. In the case of irradiation in air, the oxidation was limited to the fibre surface where the gel fraction decreased by chain scission, and the depth of the oxidation area from the surface was estimated to be 2μm. Tensile tests showed similar stress–strain curves for irradiation in vacuum or in air, but the elongation at break decreased more obviously for irradiation in air. The oxidation products, such as carboxylic acids, were detected by FTIR measurement. However, the DSC and XRD analyses indicated little change of crystallinity on irradiation in vacuum or in air. The oxidation was limited to a thin surface area on irradiation in air due to a low migration rate of the radicals trapped in the crystallite in the UHMW-PE fibre. [ABSTRACT FROM AUTHOR]

Abstract: 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 1–7phr CNT were prepared using the solvent casting method and the nanocomposites were radiated at doses of 50–200kGy. The change in mechanical properties, especially, tensile strength (Ts), elongation at break (Eb), hardness and tensile modulus at 100% elongation (M 100) 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, M 100 and the hardness of the SMR/CNT nanocomposites significantly increased with radiation dose; the elongation at break exhibited an increase up to 100kGy, and a downward trend thereafter. Results on gel fraction further confirmed the crosslinking of SMR/CNT nanocomposites upon radiation. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol) was used as base material for hydrogel preparation. The water absorption, gel fraction, and density of different gels prepared by the freezing/thawing method were studied. [ABSTRACT FROM AUTHOR]

Abstract: A new superabsorbent hydrogel has been prepared from tragacanth and polyethylene oxide (PEO) by gamma radiation at room temperature. Tragacanth solutions with different concentrations (1%, 3% and 5%) have been blended with 5% aqueous solution of PEO at a ratio of 1:1 and irradiated at doses 5–20kGy. The properties of the prepared composite hydrogels were evaluated in terms of the gel fraction and the swelling behavior. An unexpected growth of the gel fraction was observed in PEO/tragacanth hydrogels irradiated at 5kGy. Incorporation of 5% tragacanth into the aqueous PEO increased significantly the swelling percent of the hydrogels to more than 14,000% and thus makes it a superabsorbent material. [Copyright &y& Elsevier]

Abstract: A typical vinylester resin, Derakane 411-350, was electron-beam (EB) cured without initiators. The curing process was investigated by gel-fraction testing, FTIR and Raman spectroscopies. Both dynamic numerical analysis and positron annihilation life spectroscopy were utilized to analyze the microstructure of resin samples irradiated with different doses and dose rates. Resin irradiated with the same dose at a low dose rate achieved a higher degree of cure than those samples irradiated with a high dose rate. Resin irradiated with low dose rates had a lower free-volume fraction with smaller interstices and a more uniform microstructure. The glass-transition temperature of the resin increased with increasing irradiation dose. The mechanical properties of the EB-cured resin confirmed the analysis of changes in microstructure arising from irradiation. [Copyright &y& Elsevier]

Abstract: Nitrile rubber with 18% acrylonitrile content in presence and absence of polyfunctional monomers like trimethylolpropane triacrylate (TMPTA), tripropyleneglycol diacrylate (TPGDA), tetramethylolmethane tetraacrylate (TMMT) and m-phenylene bismaleimide was subjected to electron beam irradiations at different temperatures. The structural changes with different doses of radiations were investigated with the help of FTIR spectroscopy (in the ATR mode), dynamic mechanical thermal analysis and sol–gel analysis. There was a decrease in the concentration of olefinic groups for this elastomer on radiation at high temperature as compared to the room temperature. The increase in crosslinking at elevated temperature was also revealed by the increase in % gel content and dynamic storage moduli with radiation dose. The lifetime of spurs, an important criterion for overlapping of spurs, was determined for both grafted and ungrafted nitrile rubber using a mathematical model. The ratio of scissioning to crosslinking for nitrile rubber was determined using Charlesby–Pinner equation. The mechanical properties were studied and the tensile strength was found to increase with grafting of polyfunctional monomers on irradiation at high temperature. [Copyright &y& Elsevier]

Shear sensitivity measurements with variation of ingredients in a synthetic sludge can be related to biosolids' structural properties and particulate amount. The shear sensitivity is primarily controlled by the gel fraction, with alginate and the associated cations increasing the gel-like behavior. However the effect of particulate fraction on shear sensitivity should also be taken into account. Shear sensitivity is thus a complex parameter including two types of response: the resistance to dispersed mass concentration into centrate, and the maintenance of desired strength while the solids concentration increases in the shear field. [ABSTRACT FROM AUTHOR]

This article reports on the curing performance of UV-curable acrylic binders prepared with trifunctional monomers and a photoinitiator. The curing reaction was achieved by direct excitation of pressure-sensitive adhesives (PSAs) by irradiation with a 100-W high-pressure mercury lamp with different UV doses. The curing performance of PSAs was studied by photo-differential scanning calorimetry (photo-DSC), gel-fraction determination and Fourier transform infrared–attenuated total reflection (FTIR–ATR) spectroscopy. The reaction rate and extent of UV curing were found to be strongly dependent on the curing rates of the trifunctional monomers, trimethylolpropane triacrylate (TMPTA) and trimethylolpropane ethoxylated (6) triacrylate (TMPEOTA), which have different molecular weights. Exothermic areas increased with increasing acrylic acid concentration. Moreover, gel fractions sharply increased after UV irradiation and then remained constant with prolonged UV exposure. TMPTA blends had higher gel fractions than TMPEOTA blends because of TMPTA's fast curing rate. Also, the gel fractions of TMPTA blends showed no variation with acrylic acid concentration. However, the FTIR–ATR absorption peak areas representing the relative concentration of C=C bonds showed more conspicuous trends for the curing reaction. Although the gel fractions of TMPTA blends showed no differences, the relative concentrations of C=C bonds increased with increasing acrylic acid concentration. In addition, TMPTA blends showed higher relative concentrations of C=C bonds because of the faster curing rate of TMPTA. [ABSTRACT FROM AUTHOR]

The effect of fenugreek seeds (Trigonella foenum graecum) compared with ranitidine was studied on aspirin-induced gastric ulcer. The gel fraction isolated from the seeds showed significant ulcer protective effect. The cytoprotective effect of the seeds seemed to be not only due to the anti-secretory action but also due to the effects on mucosal glycoproteins. The fenugreek seed gel also prevented the rise in lipid peroxidation induced by aspirin presumably by enhancing antioxidant potential of the gastric mucosa thereby lowering mucosal injury. Histological studies revealed that the soluble gel fraction prevents lesion formation and is effective as ranitidine. These observations show that fenugreek seeds possess antiulcer potential. [ABSTRACT FROM AUTHOR]

Abstract: The influence of two aqueous acidic environments on two types of pure ethylene-propylene-diene (EPDM) rubber (i.e., elastomer) thin films is studied. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) results revealed the formation of several oxygenated species on the surface after exposure. Raman spectroscopy along with ATR-FTIR results confirmed the vulnerability of the olefinic double bonds (Cthylidene-2-norbornene (ENB) in acidic environments. In addition, the aggressive nature of 20% Cr(VI)/H2SO4 was also observed through an increase in oxygenated species formation on the surface of EPDM rubbers compared to 20% H2SO4 under identical conditions. Complex formation on the surface of EPDM samples exposed to 20% Cr(VI)/H2SO4 through reactions of carboxylic groups (generated due to EPDM degradation) with Cr(III) (formed due to reduction of Cr(VI)) was also evident in ATR-FTIR. Finally, all the oxygenated species combined to form crosslinking as observed by the increase in gel fraction with exposure time. Effect of molar mass on chemical changes was noticed as samples with higher molar masses were found to form relatively higher amount of gel upon exposure. However, no significant effect of long chain branching was noticed. On this basis, plausible surface degradation mechanisms are proposed. [Copyright &y& Elsevier]

In the present work, the silane grafting and water cross-linking of low density polyethylene (LDPE) were investigated. The grafting reaction was carried out in an internal mixer and polyethylene cross-linking was done in hot water. The effect of silane, peroxide, catalyst, carbon black, cross-linking time, and cross-linking temperature on the grafting and cross-linking processes are reported. Vinyl trimethoxy silane (VTMO) and di-cumyl peroxide (DCP) were selected as grafting agent and initiator respectively. Silane grafting on polyethylene was determined using Fourier transform infrared (FTIR) spectroscopy and torque monitoring of the mixer. Absorption peak due to –Si–OCH 3 groups in FTIR and torque increasing due to silane grafting in the mixer illustrated that silane-grafting reactions occurred. The FTIR data demonstrated that the extent of silane grafting was increased as the concentration of silane and peroxide was increased. Thermogravimetry analysis (TGA) determined that the thermal stability of LDPE increased by increasing the amount of silane grafting. Gel fraction increased with silane and peroxide concentration. As the percent of of catalyst increase the time scale for specified gel content shifted to shorter times. Incorporation of carbon black into LDPE decreased the extent of silane grafting and gel fraction. Water temperature increasing in cross-linking stage reduced the time to maximum degree of cross-linking. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol) (PVA) can be modified to polymer hydrogels by radiation crosslinking and can be used in different biomedical applications. A study was done on the optimization of ingredients concentration for preparing good quality PVA hydrogels with natural polysaccharides. The synthesized hydrogels were also characterized by measuring the different physical properties e.g. gel fraction, swelling and absorption rate. Besides these, sterility test were also performed. Good quality hydrogels were obtained from PVA and natural polysaccharides solutions with 27 kGy radiation dose. There is an influence of natural polysaccharides on the gel fraction of hydrogel. The increase in the amount of polysaccharide causes a decrease in gel fraction that is decrease in the crosslinking density of PVA hydrogel network. The prepared hydrogels were found to be sterile. [ABSTRACT FROM AUTHOR]

Cost-efficient ceramic SiCN fibers were produced by the precursor route consisting of four processing steps: synthesis of the polymer, melt-spinning, curing via electron beam (e-beam) and subsequent pyrolysis at 1100°C in a nitrogen atmosphere. A special solid and meltable fiber polymer, the so-called polycarbosilazane ABSE has been developed for this purpose, which is easily curable by e-beam. In this article the influence of the curing dose and the molecular weight of the used precursor on polymer cross-linking are discussed. The degree of cross-linking of the e-beam treated precursor ABSE is characterized by the gel fraction and the pyrolysis behavior. The gel fraction increases with the e-beam dose as well as with higher molecular weight of the used precursor fraction. By an optimal adjustment of the e-beam dose on the molecular weight of the precursor the curing treatment leads to unmeltable polymer fibers at reduced costs as well as to an improved flexibility of the green fibers which is very important for the continuous pyrolysis process to ceramic fibers. [ABSTRACT FROM AUTHOR]