摘要:

AbstractThe temperature dependence of the reaction between some metal oxides and an aqueous solution of polyacrylic acid was investigated using the infrared measurements. The obtained data indicated that the divalent metal oxides MgO, ZnO, and PbO react rapidly with the polyacrylic acid forming carboxylate salts. The bonding between the acid groups and these metals is purely ionic in character. The reactivity between these metals and the carboxylic acid is inversely proportional to the radius of metal ions. The reaction of Bi2O3, Cr2O3, and TL2O3is far from complete. However, SiO2reacts slowly with polyacrylic acid at 0°C only. The results provided strong evidences that the rate of reaction between some metal oxides and polyacrylic acid depends on the temperature of reaction, This rate of reaction is enhanced as the temperature is lowered

ISSN:0021-8995    

DOI:10.1002/app.1990.070410301

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

年代:1990

数据来源: WILEY

摘要:

Abstractit‐Polypropylene films were coextruded by using dies of varying extrusion draw ratio (EDR) from 2–10. Among the resulting films, the film coextruded at EDR 9 possesses the most attractive superstructure and the highest modulus. The dynamic modulus at room temperature was 7 GPa and an αcdispersion peak occurred at 100°C in E″‐temperature curves, which is higher by about 20°C than that of the multistep zone‐drawn and zone‐annealed fibers previously reported. Further, to prepare films with higher draw ratio and higher modulus, repetition of the coextrusion was attempted. Consequently, the draw ratio and the E′ at room temperature reached 12 and 13 GPa, respectively. The present paper discusses changes in molecular orientation, crystallinity, uniformity of the superstructure, and dynamic viscoelasticity, with increasing of the used EDR and repeating the coextrusion with some com

ISSN:0021-8995    

DOI:10.1002/app.1990.070410302

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

年代:1990

数据来源: WILEY

摘要:

AbstractA bisphenol‐A diglycidylether (DGEBA) based epoxy was cured with a cycloaliphatic diamine (4,4′‐diamino‐3,3′‐dimethyldicyclohexylmethane, 3DCM), in the presence of an epoxy terminated butadiene‐acrylonitrile random copolymer (ETBN). Results showed that vitrification is slightly delayed with the rubber addition. With ETBN the auto‐catalytic mechanism by [OH]0is predominant at the beginning of the reaction, and on the contrary dilution is the dominant factor afterx= 0.15. Phase separation takes place completely, well before gelation and vitrification; the conversion at the onset of phase separation decreases with the rubber amount but does not depend significantly on the temperature. The maximumTgof the rubber‐modified matrix does not depend on the cure temperature but decreases with the initial rubber concentration. This implies that a significant amount of rubber remains in solution in the continuous phase. This explains the delay

ISSN:0021-8995    

DOI:10.1002/app.1990.070410303

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

年代:1990

数据来源: WILEY

摘要:

AbstractPoly(ethylene ether carbonate)diols (2025 mol wt) have been made by the molecular weight advancement of lower molecular weight oligomers and have been fabricated into polyurethane elastomers by reaction with 4,4′‐MDI and 1,4‐butanediol using the prepolymer method. Polymer structure has been delineated by carbon‐13 NMR. Comparisons have been made to a series of elastomers based on other polyester and polyether polyols (2000 mol wt) under conditions where the only variable was the soft segment structure. The poly(ethylene ether carbonate) diol gives a polymer with a partially phase mixed morphology, a higher ambient temperature modulus, and a lower ΔHmthan the other polyester polyols. This lower ΔHmleads to a significantly lower rubbery plateau modulus than the other polyester polyols. Phase mixing is increased by post‐curing at 150°C. Organic solvent resistance is the most outstanding property. The poly(ethylene ether carbonate) diol produces a polymer with predominantly polyester pol

ISSN:0021-8995    

DOI:10.1002/app.1990.070410304

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

年代:1990

数据来源: WILEY

摘要:

AbstractA series of polyurethane elastomers were studied in which the soft segment composition was a molecular weight advanced poly(ethylene ether carbonate)diol (2025 mol wt) and the hard segment composition was based on MDI/1,4‐butanediol. These polyurethane elastomers had a constant soft segment composition and block length, a constant hard segment composition, but a variable hard segment block length and concentration (31.9–65.2 wt % hard segment). Properties such as rubbery plateau modulus, solvent resistance, melting point, hardness, tensile strength, and hard segment run length all improve with increasing hard segment concentration. DMA and DSC data indicate a partially phase mixed morphology. However, phase mixing must occur at domain boundaries since the soft segmentTgis nearly invariant with hard segment concentration. Annealing studies indicate that the optimum post‐cure temperature, for 1 h, is about

ISSN:0021-8995    

DOI:10.1002/app.1990.070410305

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

年代:1990

数据来源: WILEY

摘要:

AbstractContact angle measurements with water indicate that the hydrophilicity of poly(ethylene terephthalate) (PET) film decreased in the order PET treated with aqueous sodium hydroxide>untreated PET>PET treated with methanolic sodium methoxide. When the sodium‐methoxidetreated polyester was hydrolyzed with caustic soda, its contact angle fell, indicating that the methyl ester groups formed during the sodium methoxide reaction by a base‐catalyzed ester interchange had been the cause of the high contact angles. Thus it appears that carboxyl groups at the surface of hydrolyzed PET play an important role in determining its hydrophilicity. It appears from adsorption experiments that there is a marked increase in the surface area of PET fibers on treatment with aqueous sodium hydroxide. The increase is attributed to the presence of the pits produced by the hydrolysis. It is suggested the higher surface area leads to increased numbers of hydrophilic groups on the fiber surface causing the greater wettability observed in the caustic hydrolyzed samp

ISSN:0021-8995    

DOI:10.1002/app.1990.070410306

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

年代:1990

数据来源: WILEY

摘要:

AbstractA model calculating the diffusion coefficients of liquids in polymeric membranes from the diffusion coefficients at zero concentration was developed. This model is based on Fujita's volume theory and considers crystallinity in the polymer and is tested by using available data in the literature, i.e.,n‐hexane–polyethylene and benzene–polyethylene systems. The calculated diffusion coefficients were simulated by calculating the pure liquid permeabilities in a pervaporation system. When comparing the predicted pure liquid permeabilities with the experimental values, these calculated values were found to be in fairly good agre

ISSN:0021-8995    

DOI:10.1002/app.1990.070410307

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe coalescence process of polymer latex particles has been investigated by following simultaneously weight losses and dielectric constants variations during water evaporation in a latex deposited as a film in a resonant cavity at microwave frequency (5 GHz) and under controlled humidity and temperature. Different styrene (S)n‐butyl acrylate (BuA) emulsion copolymer latexes were examined so as to differentiate the behaviors of film forming or non‐film‐forming latexes. In the latter ones, both flocculation and maximum packing points were clearly evidenced, whereas only the first point was shown in the former ones. The effect of other colloidal variables (particle size distribution, surface charge density, particle diameter, ionic strength) have also been studied. It is found that the influence of the last three parameters is reflective of the latex stability and can be well detected by dielectric measurement. Such a method appears to be quite reliable for studying the film‐forming process of latexes having different colloidal characte

ISSN:0021-8995    

DOI:10.1002/app.1990.070410308

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

年代:1990

数据来源: WILEY

摘要:

AbstractExamples of simulation in the first reactor for the direct continuous esterification were shown to predict the effects of water added into the reactor (δ H 2O) on the reactions by a computer. From the simulation results, the followings were confirmed: Although the higher δ H 2Ogives the worse results, i.e., the main reaction rates become lower, it brings about the better results, i.e., the side reactions of diethylene glycol (DEG) formation is suppressed; the clearing point where solid (undissolved) terephthalic acid begins not to exist in the reaction mixtures, β = 1, is the point ofAV= 0.6 eq/kg, which coincides with the point obtained from the experimental observation, independently of reaction

ISSN:0021-8995    

DOI:10.1002/app.1990.070410309

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

年代:1990

数据来源: WILEY

摘要:

AbstractFilms were cast from liquid crystalline solutions of cellulose in an ammonia (NH3)/ammonium thiocyanate (NH4SCN) solvent. Microscopic examination of the cellulose liquid crystalline solutions used for the film formation exhibited the so‐called conjugated phase. It displayed a fingerprint and a uniformly dispersed highly birefringent pattern. Without additives, the films made from these liquid crystalline solutions are clear, flexible, and have high strength comparable to commercial Cellophone® films. The infrared crystallinity index of the film was somewhat higher than that of other cellulose II materia

ISSN:0021-8995    

DOI:10.1002/app.1990.070410310

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

年代:1990

数据来源: WILEY