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Ray Irradiation (ray + irradiation)
Selected AbstractsA Facile Route to ZnS,Polymer Nanocomposite Optical Materials with High Nanophase Content via ,-Ray Irradiation Initiated Bulk Polymerization,ADVANCED MATERIALS, Issue 9 2006C. Lü Transparent ZnS/polymer bulk nanocomposites with high particle contents are prepared via ,-ray irradiation initiated polymerization. This strategy involves the design and tailoring of the surface of the nanoparticles and choice of the monomer as well as the selection of the polymerization route. The figure shows a TEM image of a bulk nanocomposite containing mercaptoethanol-capped ZnS with a particle content of 20,wt,%. [source] Improved compatibility of EVOH/LDPE blends by ,-ray irradiationADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009Haihong Li Abstract The change of compatibility of poly(ethylene- co -vinyl alcohol) (EVOH)/LDPE blends induced by,-ray radiation was studied. Gel extraction experiment results show that the gel fraction of blends increases linearly with the content of LDPE and reaches a maximum at 100 kGy, because neat EVOH is difficult to cross-link by irradiation. A comparison of theoretical and experimental gel contents indicates that some EVOH molecular chains enter the LDPE gel network. The peak at 3363 cm,1 on the Fourier transform infrared spectrum of pure blend gel is assigned to typical stretching of an OH bond, which indicates that a "graft" reaction occurs in the interface between EVOH and LDPE phases during the irradiation process. Mechanical property measurement results support such a structural change. The tensile strength of cross-linked blends increases with absorbed dose first, reaches a maximum value at 150 kGy, and then decreases with dose. A similar trend can also be observed in bending tests. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:192,198, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20160 [source] Thermal and rheological properties of poly(vinyl alcohol) and water-soluble chitosan hydrogels prepared by a combination of ,-ray irradiation and freeze thawingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Xiaomin Yang Abstract Poly(vinyl alcohol) (PVA)/water-soluble chitosan (ws-chitosan) hydrogels were prepared by a combination of ,-irradiation and freeze thawing. The thermal and rheological properties of these hydrogels were compared with those of hydrogels prepared by pure irradiation and pure freeze thawing. Irradiation reduced the crystallinity of PVA, whereas freeze thawing increased it. Hydrogels made by freeze thawing followed by irradiation had higher degrees of crystallinity and higher melting temperatures than those made by irradiation followed by freeze thawing. ws-Chitosan disrupted the ordered association of PVA molecules and decreased the thermal stability of both physical blends and hydrogels. All the hydrogels showed shear-thinning behavior in the frequency range of 0.2,100 rad/s. Hydrogels made by freeze thawing dissolved into sol solutions at about 80°C, whereas those made by irradiation showed no temperature dependence up to 100°C. The chemical crosslinking density of the hydrogels made by irradiation followed by freeze thawing was much greater than that of hydrogels made by freeze thawing followed by irradiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Distribution of acrylic acid grafted chains introduced into polyethylene film by simultaneous radiation grafting with water and ethanol as solventsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Zhengchi Hou Abstract The graft copolymerization of acrylic acid onto low-density polyethylene films by simultaneous ,-ray irradiation was carried out. The effect of water and ethanol as grafting solvents on the distribution of grafted poly (acrylic acid) in the low-density polyethylene films was studied with optical microscopy observations of dyed and sliced samples and attenuated total reflection/Fourier infrared spectroscopy analysis. When no vigorous homopolymerization occurred, both polyethylene and poly(acrylic acid) existed in the grafted layer, and the thickness of the grafted layer and the poly(acrylic acid) concentration in the grafted layer increased with an increasing degree of grafting, regardless of the grafting conditions, the former increasing faster than the latter. In comparison with water as the solvent, in the absence of the inhibitor, homopolymerization could be suppressed to a certain degree in the ethanol solvent system, whereas in the presence of the inhibitor, obvious homopolymerization occurred at a lower monomer concentration, and both the degree of grafting and the thickness of the grafted layer were lower. Such differences could be explained by the chain transfer and the relatively low solubility of poly(acrylic acid) in ethanol. In addition, an experimental scheme using optical microscopy to observe the dyed and sliced polymers was optimized. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1570,1577, 2007 [source] Grafting of polymers onto and/or from silica surface during the polymerization of vinyl monomers in the presence of ,-ray-irradiated silicaJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2006Akiko Tsuchida Abstract The effects of radicals on silica surface, which were formed by ,-ray irradiation, on the polymerization of vinyl monomers were investigated. It was found that the polymerization of styrene was remarkably retarded in the presence of ,-ray-irradiated silica above 60 °C, at which thermal polymerization of styrene is readily initiated. During the polymerization, a part of polystyrene formed was grafted onto the silica surface but percentage of grafting was very small. On the other hand, no retardation of the polymerization of styrene was observed in the presence of ,-ray-irradiated silica below 50 °C; the polymerization tends to accelerate and polystyrene was grafted onto the silica surface. Poly(vinyl acetate) and poly(methyl methacrylate) (MMA) were also grafted onto the surface during the polymerization in the presence of ,-ray-irradiated silica. The grafting of polymers onto the silica surface was confirmed by thermal decomposition GC-MS. It was considered that at lower temperature, the grafting based on the propagation of polystyrene from surface radical ("grafting from" mechanism) preferentially proceeded. On the contrary, at higher temperature, the coupling reaction of propagating polymer radicals with surface radicals ("grafting onto" mechanism) proceeded to give relatively higher molecular weight polymer-grafted silica. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2972,2979, 2006 [source] Dithiocarbamate mediated controlled/living free radical polymerization of methyl acrylate under 60Co ,-ray irradiation: Conjugation effect of N -groupJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2004Daoben Hua Abstract The free radical polymerizations of methyl acrylate have been studied under ,-ray irradiation in the presence of the dithiocarbamates with different N -groups. The results indicate that the conjugation structure of the N -group of dithiocarbamate plays an important role in living free radical polymerization. The polymerizations reveal good living characteristics in the presence of dithiocarbamates (benzyl 1H-imidazole-1-carbodithioate, benzyl 1H-pyrrole-1-carbodithioate, benzyl 1H-indole-1-carbodithioate, and benzyl 9H-carbazole-9-carbodithioate) with N -aryl group. In contrast, the polymerization with benzyl N,N -diethyldithiocarbamate cannot be controlled, and the obtained polymer has a broad molecular weight distribution or even crosslink occurs. Moreover, polymerization rate is influenced by the conjugation structure of the N -group of dithiocarbamate, and the aromatic polycyclic structure of the N -group leads to slow polymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5670,5677, 2004 [source] Synthesis of comb-shaped poly(methyl methacrylate)- b -poly(polytetrahydrofuran acrylate) under 60Co ,-ray irradiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2002Tao He Abstract Comb-shaped graft copolymers with poly(methyl methacrylate) as a handle were synthesized by the macromonomer technique in two steps. First, polytetrahydrofuran acrylate (A-PTHF), prepared by the living cationic ring-opening polymerization of tetrahydrofuran, underwent homopolymerization with 1-(ethoxycarbonyl)prop-1-yl dithiobenzoate as an initiator under 60Co , irradiation at room temperature; Second, the handle of the comb-shaped copolymers was prepared by the block copolymerization of methyl methacrylate with P(A-PTHF) as a macroinitiator under 60Co , irradiation. The two-step polymerizations were proved to be controlled with the following evidence: the straight line of ln[M]0/[M] versus the polymerization time, the linear increase in the number-average molecular weight with the conversion, and the relatively narrow molecular weight distribution. The structures of the P(A-PTHF) and final comb-shaped copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3367,3378, 2002 [source] Shrinking Behavior of Surfactant-Grafted Thermosensitive Gels and the Mechanism of Rapid ShrinkingMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2008Kosuke Okeyoshi Abstract Surfactant-grafted hydrogels with a fast response to temperature were prepared. In order to clarify the mechanism of rapid shrinking, the effects of the grafted surfactant and the homogeneity of the main chain were investigated. Poly(NIPAAm- co -S180A) gels prepared using a chemical cross-linker (bis-PNS gels) exhibited rapid shrinking, as did PNS gels prepared by , -ray irradiation (, -PNS gels). This suggested that the rapid shrinking of the PNS gel did not depend on the homogeneity of the main-chain structure. The shrinking kinetics of the bis-PNS gels depended on the amount of the introduced surfactant, which means that shrinking is enhanced by micelle formation as a dynamic driving force. From the analysis by dynamic light scattering (DLS) and scanning microscopic light scattering (SMILS), it was suggested that the micelle structure, which induced rapid shrinking, existed in the bis-PNS gel. [source] The effect of 60Co ,-rays on the crystal structure, melting and crystallization behavior of poly(butylene succinate)POLYMER INTERNATIONAL, Issue 11 2004Jianbin Song Abstract The results obtained for poly(butylene succinate) (PBS) after 60Co ,-ray irradiation, studied by wide-angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC) and polarizing optical microscopy (POM), revealed that the degree of crystallinity, melting temperature and enthalpy decreased with increasing irradiation dose, but that the crystal structure of PBS did not vary when compared to non-irradiated PBS. By using Scherrer equation, small changes occurred in the crystal sizes of L020, L110 and L111. The spherulitic morphology of PBS was strongly dependent on irradiation dose and changed significantly at higher irradiation dosages. The crystallization kinetics of PBS indicated that the Avrami exponent (n) for irradiated PBS was reduced to 2.3, when compared to non-irradiated PBS (3.3). Copyright © 2004 Society of Chemical Industry [source] | ||||||||||