摘要:

AbstractThe grafting of polyacrylamide on to guar gum in aqueous medium initiated by the potassium persulfate/ascorbic acid redox system has been studied gravimetrically at the temperature 35 ± 0.2°C in the presence of atmospheric oxygen and Ag+ions. The rate of grafting was found to increase with temperature, concentration of redox components, acrylamide, and guar gum. But at higher concentration of guar gum, the rate of grafting was found to decrease. A mechanism for grafting and suitable rate expression have been suggeste

ISSN:0021-8995    

DOI:10.1002/app.1990.070391101

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

年代:1990

数据来源: WILEY

摘要:

AbstractContinuous vinyl acetate emulsion polymerization was carried out by using a mixed surfactant system of “Aerosol” OT (AOT) and sodium dodecyl sulfate (SDS). It is well known that the AOT reduces surface tension considerably and has stronger monomer solubilization power than SDS. In this work, particular attention is given to observe the effects of the mixed surfactant on the molecular weights and polydispersities. In comparison with experiments using only SDS, the particle size appears similar, in the range of 190–280 nm. The conversion increased substantially to the 70% range from the 50% level observed with only SDS. All experiments were conducted at 60°C with a mean residence time of 30 min. The total surfactant concentration was maintained at 0.03 mol/L water for all experiments. It was found that once some AOT was included in the surfactant, the behavior was very similar to that observed with only AOT. The number average molecular weights were found to decrease substantially while the polydispersity increases dramatically to about 12. It is believed that AOT may act as a significant chain transfer agent in the polymeri

ISSN:0021-8995    

DOI:10.1002/app.1990.070391102

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe thermal degradation of samples of cotton, cotton oxidized by ceric ion, cotton grafted with vinyl acetate and methyl acrylate having different percent grafting yield, poly(vinyl acetate), and poly(methyl acrylate) 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 ceric ion redox system shows little effect upon thermic properties of cotton cellulose. Graft copolymerization of vinyl acetate makes cotton thermally less stable, while, in the case of methyl acrylate grafted cotton samples having 33, 83, and 174% grafting yield, the initial decomposition starts at lower temperatures; but decomposition beyond 360°C takes place at higher temperatures than those for ungrafted cotton, and in the case of the sample with 430% grafting yield the thermal stability is higher than that of original cotton. The thermal stability of cotton grafted with methyl acrylate is higher than that of cotton grafted with vinyl acetate. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters

ISSN:0021-8995    

DOI:10.1002/app.1990.070391103

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe polymerization of methyl methacrylate in aqueous montmorillonite suspension with thiourea was studied. The polymerization initiated on the montmorillonite surface following the adsorption of thiourea and the monomer. A 20% increase in the basal spacings of the clay mineral was observed. A large fraction of the polymer was nonextractable and was found to be thermally more stable than the extractables. The rate of the polymerization increased with increasing amounts of clay, thiourea, and followed one‐half order on the latter. The apparent energy of activation (Ea) of the system was characteristic of redox free radical polymerizatio

ISSN:0021-8995    

DOI:10.1002/app.1990.070391104

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe results of the experimental and molecular‐dynamics study of the process of mechanical degradation of polymer chain, testifying to the essential role of nonthermal channels of dissipation of elastic energy accumulated during deformation, have been discussed. High‐energy molecular products of mechanical degradation, which are able to induce a chain branching process leading to “explosive” formation of submicrocrackes, have been discovered. It has been noted that a considerable part of polymer chain energy is concentrated in localized excitations of a soliton type, which play the determining role at all the stages of mechanical degradation under consid

ISSN:0021-8995    

DOI:10.1002/app.1990.070391105

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

年代:1990

数据来源: WILEY

摘要:

AbstractSuperabsorbent polymers were prepared using acrylonitrile grafted to corn starch employing low levels of gamma ray radiation as initiator. Various grafting parameters have been studied at these low dosages. Absorbency values for the final products are reported. Use of the above superabsorbent as a desiccant has been evaluated. The product will find application where dispersions of low viscosity and high water absorbencies are desired.

ISSN:0021-8995    

DOI:10.1002/app.1990.070391106

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe dissolution characteristics of model positive resists were investigated through the use of various copolymers of methyl methacrylate and maleic anhydride. Dissolution in methyl ethyl ketone was found to be dependent on the radiation dose and on the composition of the copolymers. The Lee–Peppas dissolution model was used to calculate important parameters of this dissolution process. It was shown that the overall dissolution rate was initially controlled by the swelling process whereas the true disentanglement/dissolution process predominated during the latter portion of the overall phenomenon. In addition, the thickness of the formed gel layer was a function of the square root of tim

ISSN:0021-8995    

DOI:10.1002/app.1990.070391107

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

年代:1990

数据来源: WILEY

摘要:

AbstractA study was made of the removal of methyl orange (MO) solutes in water by the reaction products of chloromethylated divinylbenzene crosslinked polystyrene (CMPS) with polyeth‐ylenepolyamines (PEPA), polyethyleneimines (PEI), and 2‐methyl‐2‐oxazoline (MeOZO). This behavior of such polymers in regard to the Klotz equation and Freundlich adsorption formula was also examined and noted to conform better to the former than to the latter. The constants of the Klotz equation were calculated. The amounts of MO removed with unit masses of the polymers and the effects of salts on removal were studied. A possible mechanism for removal is di

ISSN:0021-8995    

DOI:10.1002/app.1990.070391108

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of maturation time of casting solution and annealing conditions on reverse osmosis (RO) properties of nylon 4 membranes are studied. The effects of plasma treatment conditions, such as supply power, treatment time, and gases used in reactor, on the water contact angle, surface energy, water flux, and salt rejection of nylon 4 membranes are considered. The best results of 4.86 × 10−5g/cm2s of water flux with 74.2% of salt rejection for 1 wt % NaCl aqueous feed solution can be obtained in the conditions of plasma treatment for 80 W–3 min in a reactor with O2on 25 wt % formic acid–4 h annealing nylon 4 membranes. The hydrophilic monomers, such as 1‐vinyl‐2‐pyrrolidone (VP), 2‐hydroxyethyl methacrylate (HEMA), and acrylic acid (AA), are plasma deposited onto the chemical and/or plasma etched nylon 4 membranes to improve the salt rejection without decrease in water flux. The salt rejection of 90.9% and water flux of 3.64 × 10−5g/cm2s of the deposited membrane are obtained in the conditions of depositing AA monomer onto the substrate membrane which was previously treated with annealing followed wi

ISSN:0021-8995    

DOI:10.1002/app.1990.070391109

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

年代:1990

数据来源: WILEY

摘要:

AbstractDeformation of acrylic acid–acrylamide copolymer gels in an aqueous solution under the influence of a dc electric field was studied. In the electric field, the gel swells, shrinks, or bends. It depends on the concentration of polyion coo−in the gel. When the concentration is low, the gel shrinks, and, when high, it swells. The gel which does not contain polyion is not influenced by the electric field. The long and thin gel is bent in an arc. The bent gel can be recovered to the original shape by removing the applied electric field or by changing the polarity of the applied electric field. The deformation is closely related to two substantial changes. One is the change of the osmotic pressure caused by the ion concentration difference between the inside and the outside of a gel. The other is the conformational change of the polymer network with decreasing of the polyion concentrat

ISSN:0021-8995    

DOI:10.1002/app.1990.070391110

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

年代:1990

数据来源: WILEY