摘要:

AbstractThe effect of large dosage irradiationin vacuoon polyethylene was investigated by the method of double irradiation. Polyethylene was first irradiated with γ‐rays to a dosage of several hundred Mradin vacuoat 298°K. The formed radicals were destoryed, and the polymer, changed chemically and morphologically, was irradiated againin vacuoat 77°K with a dose of 12.7 Mrad. The thermal decay of radicals produced in polyethylene by the second irradiation was investigated. The results show that many double bonds are formed in the sample irradiated to several hundred Mrad on the first irradiation. Alkyl radicals produced by the second irradiation react with these double bonds yielded by the first irradiation to form a large number of allyl radicals. These allyl radicals are much more stable than alkyl radicals radicalsin vacuoat 298°K. In a sample not exposed to the first irradiation, almost all radicals formed by the second irradiation decay to form stable products. Crosslinks formed by a large amount of irradiation make the polyethylene matrix more rigid. This rigidity slows down the radical decay. These results suggest that the rate of radical accumulation in polyethylene irradiatedin vacuoincreases as the dosage incr

ISSN:0021-8995    

DOI:10.1002/app.1982.070271101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe large dosage irradiation effect on polyethylene in air was examined by the method of double irradition. Polyethylene was first irradiated with γ‐rays to a dosage of a few hundred Mrad in air at 298°K. The formed radicals were destroyed, and the polymer, changed chemically and morphologically, was irradiated againin vacuoat 77°K with a dose of 12.7 Mrad. The thermal decay of radicals produced in polyethylene by the second irrdiation was investigated. The results were compared with the sample not exposed to the first irradiation. The results were also compared with previous data of polyethylene irradiatedin vacuoto a great extent and then treated in the same manner as that in the present experiment. The results show that scission of the polymer chain by oxidation makes the radical decay faster. Simultaneously, crosslinks formed in polyethylene irradiated in air to a great extent slow down the radical decay. Almost the same number of double bonds was formed in polyethylene irradiated in air as in polyethylene irradiatedin vacuo. These double bonds react with alkyl radicals to form allyl radi

ISSN:0021-8995    

DOI:10.1002/app.1982.070271102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractDielectric relaxation, infrared spectra, and X‐ray diffraction data of polyacrylonitrile (PAN) heat treated at 120°C in air and under vacuum and of the untreated PAN are reported. The heat treatment resulted in (1) lowering of dielectric constant increment, dielectric dissipation factor, and increase in relaxation temperature and glass transition temperature; (2) lowering of the intensity of CN stretching band in the infrared spectra; and (3) increase in degree of order of the X‐ray diffraction results. The changes produced by heat treatment under vacuum are found greater than those produced by heat treatment in air, which suggests that the observed effect is not caused by chemical changes in the PAN molecule under heat treatment. Interpretation of these results is attempted on the basis of the difference in the degree of bound nitrille group pairs (bound through intermolecular dipole–dipole interactions) in the structure of PAN heat treated under the different

ISSN:0021-8995    

DOI:10.1002/app.1982.070271103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractPolystyrene and poly(methyl acrylate) were grafted onto wheat starch by gamma radiation and chemical initiation, respectively. The respective percent add‐on values were 46 and 45;68% of the polystyrene formed was grafted to starch, and the corresponding proportion of poly(methyl acrylate) was 41%. The molecular weight distributions of the homopolymer and graft portions were characterized, and extrusion conditions were established for production of ribbon samples of starch‐g‐PS and starch‐g‐PMA. Both copolymer types were considerably weakened by soaking in water, and this effect was more immediate and drastic for starch‐g‐poly(methyl acrylate). Both graft copolymers regained their original tensile strengths on drying, but the poly(methyl acrylate) specimens did not recover their original unswollen dimensions and retained high breaking elongations characteristic of soaked specimens. Tensile and dynamic mechanical properties of extruded and molded samples of both graft polymers are reported, and the plasticizing effects of water a

ISSN:0021-8995    

DOI:10.1002/app.1982.070271104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractA phosphorus‐ and nitrogen‐containing polyl is prepared by condensing tetrakis(hydroxymethyl)phosphonium chloride with diethanol amine in aqueous medium. The newly synthesized polyol‐bis(hydroxymethyl)‐N,N‐bis(2‐hydroxyethyl)aminomethylphosphine oxide (AMPO) is used in the preparation of rigid polyurethane foams with a various phosphorus content. With the view to comparing their properties, polyurethane foams are also prepared on the basis of the commercially available flame retardant diethyl‐N,N‐bis(2‐hydroxyethyl)aminomethylphosphonate (Fyrol 6). The flammability, thermal stability, and thermoechanical properties of the polyurethane foams obtained are studied. A certain difference in the behavior of the two modified polyurethane foams is observed. The polyurethane foams with AMPO exhibit a slight increase in the resistance to combustion (oxygen index) and a noticeable improvement in the thermal and mechanical properties. These differences probably arise as a result of structural and functional differences between the two types of phosphorus‐containi

ISSN:0021-8995    

DOI:10.1002/app.1982.070271105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractDrawn nylon 6 filaments were subjected to swelling treatment with benzyl alcohol and aqueous solution of phenol and formic acid under slack condition and under tension. The pretreated samples were dyed with a disperse dye Foron Yellow SE‐FL (C.I. Disperse Yellow 42). A considerable increase in the equilibrium dye uptake was observed as a result of swelling treatment. Studies on lateral order by X‐ray methods showed that lateral order has increased considerably as a result of preswelling treatment. This apparent contradiction, viz., increase in lateral order and at the same time increase in dye upstake, is explained as due to increased void volume. Studies on mechanical properties showed that the percentage elongation is increased as a result of swelling treatment under slack condition in spite of increased lateral order. This is explained as due to the slippage of chain‐folded crystal

ISSN:0021-8995    

DOI:10.1002/app.1982.070271106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe pyridine derivatives were combined to poly(styrene) beads with spacer groups or a graft chain. These spacer‐type and graft‐type pyridine beads formed their Cu complexes with high rates and large stability constants; they act as an effective chelating resin. The pyridine residues were more mobile due to the spacer group and the graft chain, compared with the poly(4‐vinylpyridine) p

ISSN:0021-8995    

DOI:10.1002/app.1982.070271107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThermal degradation of polystyrene was performed in a differential scanning calorimeter under nitrogen atmosphere, and the glass transition temperature was measured continuously. From random chain scission kinetics andTg‐molecular weight relationships, the rate constant for random scission was obtained. The rate constant was found to undergo a drastic change at a critical molecular weight (∽45,000), which corresponds to a similar observation in relaxation studies. A viscosity‐dependent mechanism for radical chain end termination is thus sugg

ISSN:0021-8995    

DOI:10.1002/app.1982.070271108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe incorporation of small amounts of a chlorinated hydrocarbon wax into polypropylene (PP) when making mica–PP composites is shown to produce a layer of degraded chlorinated hydrocarbon at the interface between the polymer and the reinforcement. Mica is shown to accelerate the thermal degradation of the chlorinated hydrocarbon, and the chlorinated hydrocarbon, or its degradation products, are shown to react with hydrocarbon analogues of the polymer. As well as modify the chemical nature of the interface, the layer of degraded chlorinated hydrocarbon is shown to modify the morphology of the interface by inhibiting the ability of the mica to nucleate the crystallization of PP from the mel

ISSN:0021-8995    

DOI:10.1002/app.1982.070271109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe alternate current (AC) and direct current (DC) ionic conductivity of hybrid films composed of polyacrylonitrile (PAN), lithium perchlorate (LiClO4), and a plasticizer was studied. Three kinds of the plasticizer [ethylene carbonate (EC), propylene carbonate (PC),N,N‐dimethylformamide (DMF)] were used. Suitability of these hybrid films for lithium battery was investigated. The AC conductivity, which represents bulk ionic conductivity, was dependent on the component and the composition of the hybrid films, ranging from 10−4−10−8Scm−1. The AC conductivity was mainly determined by the molar ratio of [plasticizer]/[LiClO4] in the hybrid films and increased with the increase in this ratio. The effect of the plasticizer on the enhancement in the AC conductivity was in the following order. DMF>EC>PC. The hybrid films with both electrodes of lithium showed the stable DC conductivity of about 1/10 of the AC conductivity, except for the hybrid films containing DMF. The hybrid films were found to be effective as a lithium ionic conductor. The galvanic cell. Li/sample/MnO2, at the discharge current density of 90 μA/cm2showed the stable electromotive force of about 3

ISSN:0021-8995    

DOI:10.1002/app.1982.070271110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY