摘要:

AbstractThe electroinitiated polymerization of commerical divinylbenzene (DVB) containingp‐ andm‐DVB andp‐ andm‐ethylvinylbenzene (EVB) and traces of diethylbenzene has been studied in acetonitrile medium with an added electrolyte, namely, tetrabutylammonium fluoroborate (TBAFB). A white partially crosslinked polymer is formed only after the passage of an electrical current. The dependence of yields on parameters such as current strength, temperature, time of electrolysis, and stirring of the reaction mixture has been determined. A detailed IR analysis of the polymeric product has been made and the linear polymeric product is identified as poly(p‐DVB‐co‐m‐DVB‐co‐p‐EVB‐co‐m‐EVB). The electropolymer is thermally stable up to 645 K as found by its DTA, TG, and DTG studies and possesses partial crystallinity as indicated by the X‐ray diffraction experiments. Experiments conducted with a split cell indicated the formation of the polymer in the anode compartment; hence the polymerization mechanism app

ISSN:0021-8995    

DOI:10.1002/app.1990.070390501

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

年代:1990

数据来源: WILEY

摘要:

AbstractPreparation and some properties of the graft copolymers obtained by radiation‐induced graft polymerization of methacrylic acid (MAA) and (acrylonitrile/MAA) comonomer onto polyethylene and polytetrafluoroethylene films, were investigated. The effect of reaction conditions, solvent, monomer, and inhibitor concentration, comonomer composition, and comonomer concentration, on the graft copolymerization process was studied. The grafting process was enhanced in the presence of comonomer (AN/MAA) as compared with individual grafting of MAA or acrylonitrile (AN). The optimum comonomer composition, at which the highest grafting yield was obtained, was found to be (80/20) wt % of (AN/MAA) comonomer. The graft copolymerization of (AN/MAA) comonomer was enhanced in presence of AN due to its higher polarity strength. The electrical and swelling properties of the graft copolymers were greatly affected by the contents of PAN and PMAA graft chains. Mechanical properties of the graft copolymers were significantly changed with the grafting yiel

ISSN:0021-8995    

DOI:10.1002/app.1990.070390502

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

年代:1990

数据来源: WILEY

摘要:

AbstractA cured epoxy resin is modified with polybutyl acrylate (A) and polyethyl acrylate (B) produced byin situultraviolet radiation polymerizations of their corresponding monomers in the epoxy resin, respectively, to reduce the internal stress. In the A system, a heterogeneous structure with submicron domains was formed. In the B system, however, the B mixed well with the epoxy matrix. In both systems, the internal stress was decreased by the modification. The glass transition temperature of the epoxy matrix decreased in the B system more than in the A system. The A‐modified resin was superior to the B‐modified resin in reducing the internal stress without decreasing the thermal resistance of epoxy re

ISSN:0021-8995    

DOI:10.1002/app.1990.070390503

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe rate of the thermal decomposition of potassium persulfate has been studied in an unbuffered aqueous solution at 50°C in nitrogen atmosphere in the presence of vinyl acetate (VA) monomer (M). It has been found that the initial rate of persulfate decomposition may be written as\documentclass{article}\pagestyle{empty}\begin{document}$$ {{ - d\left( {{\rm S}_2 {\rm O}_8^{2 - } } \right)} \mathord{\left/ {\vphantom {{ - d\left( {{\rm S}_2 {\rm O}_8^{2 - } } \right)} {dt{\rm }\infty \left( {{\rm S}_{\rm 2} {\rm O}_{\rm 8}^{{\rm 2 - }} } \right)}}} \right. \kern-\nulldelimiterspace} {dt{\rm }\infty \left( {{\rm S}_{\rm 2} {\rm O}_{\rm 8}^{{\rm 2 - }} } \right)}}^{1.49 \pm 0.05} \times \left( M \right)^{0.50 \pm 0.06}$$\end{document}in the concentration range of persulfate (1.85 × 10−2–1.85 × 10−3m/dm3) and VA (0.054–0.27 m/dm3). The pH of the aqueous solution of persulfate was found to decrease continuously at 50°C, but there was no measurable change of pH of the aqueous solution containing persulfate and VA at 50°C in the presence of nitrogen at the early stages of the reaction. VA, methyl acetate, and ethyl acetate have been found to undergo very slow hydrolysis in aqueous solution at 50°C. The partition coefficient (β) of the monomer between the polymer phase and the aqueous phase was found to be 21 ± 2 in the presence and absence of electrolytes (K2SO4, 10−4–10−3m/dm3) by the bromometric estimation of the monomer present in the aqueous phase containing known amounts of monomer [1.80–2.20%, w/v] and freshly prepared polymer (0.3–0.5 g/100 mL). Above 10−2(m/dm3) persulfate, the polymer obtained was found to be insoluble in common solvents, viz., acetone, benzene, etc. Highly purified sodium dodecyl sulfate (0.5–5.0 × 10−3m/dm3) had no measurable effect on the

ISSN:0021-8995    

DOI:10.1002/app.1990.070390504

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

年代:1990

数据来源: WILEY

摘要:

AbstractA study of the influence of dimethyl sulfoxide (DMSO) on the graft copolymerization of acrylonitrile (AN) onto jute fiber using ceric ion has been made. The effect of concentrations of monomer, Ce(IV) and DMSO on graft yield have been studied. Besides, the effect of time, temperature, acid, and the amount of jute fiber on graft yield has been investigated. On the basis of experimental findings, a reaction mechanism has been proposed and optimum condition for effective grafting has been suggested.

ISSN:0021-8995    

DOI:10.1002/app.1990.070390505

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

年代:1990

数据来源: WILEY

摘要:

AbstractA microporous membrane is prepared by treating the cation exchange membrane (Fe+++form) with an H2O2aqueous solution. The cation exchange membrane is prepared by the paste method: the base membrane is prepared beforehand and then sulfonated. The preparative conditions of the base membrane were studied in connection with the characteristics of the resultant microporous membrane. Furthermore, the availability of the microporous membrane for ultrafiltration was studied by using an aqueous solution of a bovine hemoglobin.

ISSN:0021-8995    

DOI:10.1002/app.1990.070390506

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

年代:1990

数据来源: WILEY

摘要:

AbstractThermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate‐methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parametersE,n, andAhave been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate‐methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate‐methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic p

ISSN:0021-8995    

DOI:10.1002/app.1990.070390507

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe permeability coefficient for oxygen diffusing through a sample of Teflon‐PFA tubing was determined experimentally. The source of the diffusing oxygen was ambient temperature air surrounding a coiled length of the PFA tubing. High pressure nitrogen was directed through the center of the PFA tubing. Oxygen permeating from the low pressure ambient air source, through the PFA tubing, and into the flowing high pressure nitrogen was observed in the effluent gases as they passed through a trace oxygen analyzer. By this means, oxygen concentrations in the effluent nitrogen were determined as a function of varying nitrogen flow rates, at nitrogen gas pressures of 4.4 and 7.8 atm (absolute), within the tubing bore. All measurements were also carried out at ambient temperatures of 21 ± 1°C. In addition, a theoretically related graphical method of evaluating the experimental data was developed and subsequently employed to actually determine the oxygen permeability coefficient for this sys

ISSN:0021-8995    

DOI:10.1002/app.1990.070390508

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn investigation was carried out on the effect of physical aging on viscoelastic properties of compatible polymer blends. Poly(methyl methacrylate) (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were chosen for this study. Blends of six different ratios of PMMA and SAN were physically aged at different times and temperatures and then subjected to stress–relaxation tests at small strains. It was found that the shape of the stress‐relaxation curve does not change with a change in blend composition, aging temperature, or aging time. A single “master curve” is presented, to which all data may be fit using 0.408 for the exponential parameter of the Williams‐Watts equation. In creating the master curve, all data are shifted horizontally in time only. For a given set of experimental conditions, the relaxation time τ may be expressed in terms of blend composition, aging temperature,

ISSN:0021-8995    

DOI:10.1002/app.1990.070390509

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

年代:1990

数据来源: WILEY

摘要:

AbstractPoly(methyl methacrylate)/(PMMA) microspheres crosslinked with various concentrations of ethylene glycol dimethacrylate (EGDM) were prepared by a suspension polymerization procedure. They were subjected to alkaline hydrolysis in ethylene glycol at high temperature (>175°C), resulting in the rapid conversion of methacrylate ester functions to methacrylic acid, while retaining the spherical shape of the microspheres intact. The method provides a novel approach to obtain smooth, nearly perfect spherical, mechanically strong, high water‐absorbing hydrogel beads from crosslinked PMMA. The reaction has been found to be considerably faster than many of the hydrolysis procedures reported previously. The effect of concentration of alkali, particle size, crosslinking density, and reaction time on the extent of hydrolysis has been investigated to a limited exte

ISSN:0021-8995    

DOI:10.1002/app.1990.070390510

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

年代:1990

数据来源: WILEY