摘要:

AbstractCellulose acetate membranes prepared from latexes containing sodium dodecyl sulfate as a stabilizer were found to undergo phase separation. This phenomenon was studied by different techniques including autoradiography, optical and scanning electron microscopy, mechanical testing, and liquid water permeation. The concentration of sodium dodecyl sulfate in the dry membranes was found essential in controlling their structure and properties, as well as the nature and amount of plasticizer incorporated in the latex system. The method of preparation and the drying duration were also relevant. Depending on whether films were produced by casting or spraying, tensile and permeation values exhibited quite different responses to variations of the sodium dodecyl sulfate content. In Paper II, a thermodynamic framework is proposed that accounts for the redistribution of sodium dodecyl sulfate into small islets, and thus for phase separation.

ISSN:0021-8995    

DOI:10.1002/app.1987.070340801

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

年代:1987

数据来源: WILEY

摘要:

AbstractTrans‐polyoctenylene (TOR), a high‐polymer polymerization product of cyclooctene, has found use as a processing aid in high‐viscosity rubber stocks. We have compared some physical and mechanical properties of a NBR‐compound with TOR with those of the same compound without TOR. Mooney viscosity was lower for the compound with TOR. Cylinders with a height and diameter of 20 mm were molded. It was found that stress–relaxation measured in the common static way was almost the same for the two compounds. Dynamic stress–relaxation occurred much more rapidly for the compound with TOR. The compound with TOR increased in hardness more rapidly when aged in air, and showed a higher swelling in oil. The DSC results imply that TOR is incorporated as a separate phase in the parent rubber. The sealing properties are affected detrimentally when TOR is used as a processing

ISSN:0021-8995    

DOI:10.1002/app.1987.070340802

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

年代:1987

数据来源: WILEY

摘要:

AbstractA series of new polymer precursors such as bismaleimides, bisnadimides, and bismethylnadimides chain‐extended byN,N′‐substituted ureas was synthesized and characterized. They were prepared by reacting a diamine containing ureylene linkages with maleic/nadic/methylnadic anhydride. Another alternative method for preparing these monomers included reaction of a diamine (1 mol) with an equimolar amount of maleic/nadic/methylnadic anhydride, subsequent reaction with a diisocyanate (0.5 mol) followed by cyclodehydration of the itermediate diamic acid. The monomers were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Their thermal polymerization was investigated by differential thermal analysis (DTA). The thermal stability of the polymers was evaluated by dynamic thermogravimetric analysis (TGA) and isothermal gravimetric analysis (IGA). No weight loss was observed when the polymers containing arylureas in their backbone were heated up to 324–334°C in nitrogen or air atmospheres. Their anaerobic char yield at 800°C fluctuated between

ISSN:0021-8995    

DOI:10.1002/app.1987.070340803

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

年代:1987

数据来源: WILEY

摘要:

AbstractIt is demonstrated by the use of spin traps that during the early stages of thermal processing of PVC considerable concentrations (>3 × 10−6mol g−1) of free radicals are produced which are primarily responsible for the initial products (hydroperoxides, unsaturation, and hydrogen chloride) previously shown to be formed in the polymer. From a semiquantitative analysis of these products, it is estimated that more than 50% of the radicals are formed from hydroperoxides and the rest by mechanoscission of the polymer chain. The spin traps are effective processing stabilizers in combination with a tin maleate HC1 scavenger. One of them (2‐methyl‐2‐nitroso propane, MNP) has also been shown to be a photoa

ISSN:0021-8995    

DOI:10.1002/app.1987.070340804

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

年代:1987

数据来源: WILEY

摘要:

AbstractSeries of suspension copolymerization of vinyl chloride with various contents of 1‐butene and 1‐pentene (5–30 mass%) were carried out under the same reaction conditions. By applying a method which utilizes periodic sampling of heterogeneous reaction mixture from the reactor during the reaction and a gas chromatographic determination of unreacted vinyl chloride in the sample, the conversion curves of vinyl chloride were determined and the initial reaction rates were com

ISSN:0021-8995    

DOI:10.1002/app.1987.070340805

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

年代:1987

数据来源: WILEY

摘要:

AbstractPoly(styrene‐co‐methyl methacrylate) copolymers of narrow chemical composition distributions were separated according to composition by linear gradient elution at column temperatures between 10 and 80°C using silica gel as an adsorbent. The initial mobile phase was a mixture of chloroform and ethanol (99.0 : 1.0, v/v) and the final one (95.5 : 4.5). The relationship of retention volume and the composition of the copolymers was obtained. Higher column temperature (and/or less ethanol content in the mobile phase) is preferable for the separation of copolymers having less MMA and vice versa. Molecular weight dependence on retention volume was not observed. The chromatographed copolymers were still chemical heterogeneous: the compositional difference of the front and rear halves of an adsorption chromatogram of a copolymer was 2.1 %. The front half had a higher styrene content and lower molecular weight averages than those for the rear half of the peak. This separation method was reproducible and the relative standard deviation was about 0.6%. Recovery of fractions was 98.2% by isocratic elution and 96.4% by gradient elu

ISSN:0021-8995    

DOI:10.1002/app.1987.070340806

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

年代:1987

数据来源: WILEY

摘要:

AbstractPlasma‐polymerized films of hexamethyldisiloxane were deposited onto various porous substrates having different pore sizes, and the gas permeability of these composite membranes was studied. In each membrane, permselectivity between oxygen and nitrogen was found, but the oxygen permeation rate was different with each substance tested. The minimum thickness of the plasma‐polymerized film needed to plug all pores and show permselectivity is about five times the pore radius of the porous substrate. The maximum oxygen permeation rates of the permselective composite membranes are approximately proportional to the effective areas for the gas permeation and inversely proportional to the pore sizes. The composite membranes show high oxygen permeation rates in cases using porous glass hollow fibers which have small pore sizes and large surface porosity as porous substrates. In cases using polysulfone hollow fibers which have high permselectivity, the composite membranes show much higher permeability ratios of oxygen‐to‐nitrogen than do those of the porous glass hollow

ISSN:0021-8995    

DOI:10.1002/app.1987.070340807

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

年代:1987

数据来源: WILEY

摘要:

AbstractThin‐film composite membranes containing photoreactive groups have been developed. The presence of these groups facilitates the subsequent photochemical conversion of the membrane to include a range of different chemical moieties. For example, a cationic or an anionic membrane can be made from the same initial composite membrane. In this paper the selection of an appropriate photolabile group is investigate

ISSN:0021-8995    

DOI:10.1002/app.1987.070340808

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

年代:1987

数据来源: WILEY

摘要:

AbstractNew flame‐retarding epoxy is synthesized by reacting 3′, 5′, 3Prime;, 5″‐tetrabromophenolphthalein (TBPP) with epichlorohydrin and characterized in comparison with commercially available tetrabromobisphenol‐A(TBBA) epoxy on their flame retardancy and thermostability. TBPP epoxy show better results in promoting flame resistance than TBBA epoxy. However, TBPP epoxy exhibits a greater effect on thermal decomposition temperature. The order of char yield at 800°C under nitrogen for the cured products is TBPP epoxy>phenolphthalein (PP) epoxy>TBBA epoxy. Meanwhile, there is a linear relationship between oxygen index and char yield for cured products of TBPP‐PP epoxy and TBBA‐

ISSN:0021-8995    

DOI:10.1002/app.1987.070340809

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

年代:1987

数据来源: WILEY

摘要:

AbstractA series ofp‐dimethylaminobenzylidene derivatives was able to sensitize the photodecomposition of diphenyliodonium salt to afford highly photosensitive negative‐type resins. When a polymer‐bearing methacryloylated group in the side chain was sensitized with a combination of thep‐dimethylaminobenzylidene compounds and the iodonium salt, the polymer demonstrated high sensitivity even to 488 nm light emitted from an Argon laser. The same photoinitiator systems were applicable to insolubilize poly(glycidyl methacrylate) through cationic photopolymerization. The storage stability of these types of photoinitiators depends on the structure of the benzylidene compounds; decreasing the basicity of the amino group enhanced the thermal st

ISSN:0021-8995    

DOI:10.1002/app.1987.070340810

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

年代:1987

数据来源: WILEY