摘要:

AbstractChanges of flow curves of the carboxylated acrylate latex dispersions during alkalinization were described in terms of parameters of the Cross theory of aggregation of disperse particles. It was found that the dependence of viscosity on pH has a maximum at pH ≃ 9.3 where a yield stress appear

ISSN:0021-8995    

DOI:10.1002/app.1988.070350101

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

年代:1988

数据来源: WILEY

摘要:

AbstractCopolymers of vinyl chloride with propene, 1‐butene, and 1‐pentene having the same content of 1‐olefin (4.0 ± 0.5 mol%) and various molar mass and copolymers with a comparable molar mass and the same composition were prepared. By measuring rheological and mechanical properties of this assembly of samples, which also included the reference vinyl chloride homopolymer, it was possible to estimate the effect of molar mass and of the individual comonomers. The copolymers under investigation possessed improved processing properties and did not suffer any deterioration of important mechanical prop

ISSN:0021-8995    

DOI:10.1002/app.1988.070350102

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

年代:1988

数据来源: WILEY

摘要:

AbstractSorption of methylene chloride in polyethylene terephthalate has been performed at three different temperatures: 21, 34, and 48°C. The solubility data are explained through dual sorption. The diffusivities are more difficult to explain since some anomalous effects were present

ISSN:0021-8995    

DOI:10.1002/app.1988.070350103

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe structure of skin layer in injection‐molded polypropylen which displayed a clear two‐phase structure of skin and core has been studied by means of wide‐angle x‐ray diffraction, small‐angle x‐ray scattering, melting behavior, density, dynamic viscoelasticity, and tensile test. In skin layer, the c‐axis and a*‐axis were highly oriented to the machine direction (MD), and the plane of the lamellar structure of about 160 Å in thickness was in normal to MD. The density was about 0.907 g/cm3, which was nearly the same as that of core layer. Although the majority of crystallites melted in the same temperature range as in that of the core layer, there was about 5.3% higher temperature melting structure (Tm= 182°C). The dynamic tensile modulusE′ in MD decreased more slowly with increasing temperature than that of the core layer and held high modulus in the range of ca. 30°C, just above the temperature at whichE′ of the core layer suddenly dropped.E′ in MD was higher than that in TD in the temperature range below 33°C, which was slightly higher than the primary absorption temperature, and the order reversed above 33°C. The tensile yield stress in MD was 1.5 times higher than that of the core layer. The skin layer in MD ruptured just after yielding and did not show necking. The tensile yield stress in TD was about half of that in MD about 0.7 times that of the core layer. The necking stress in TD was about 0.6 times that of the core layer. In general, a polypropylene melt crystallizes under a high shear stress in injection molding. From these facts, it was concluded that the skin layer is composed of so‐called “shishkebab”‐like main skeleton structures, whose axis is parallel to MD, piled epitaxially with a*‐axis‐or

ISSN:0021-8995    

DOI:10.1002/app.1988.070350104

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe diffusion of solutions of ethyl centralite (EC), dibutylphthalate (DBP), and dinitrotoluene (DNT) into a nitrocellulose (NC) propellant is investigated. DBP and EC penetrate the propellant in a way consistent with Case II diffusion. The diffusion of DNT solutions is Fickian. The apparent activation energy for Case II diffusion is 62 kJ/mol for DBP and 66 kJ/mol for EC. Changes to coating solvent polarity have little effect on DNT and DBP penetration and merely alter the rate, not the mechanism, of EC diffusion into the propellant.

ISSN:0021-8995    

DOI:10.1002/app.1988.070350105

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe formation of primary particles in agitated bulk polymerizations of vinyl chloride was found to proceed in two stages. The first stage occurred at the very beginning of the polymerization; the second stage started as the initially nucleated particles began to agglomerate, and continued up to at least 7% conversion. Upon formation, the primary particles were stable and did not agglomerate until reaching a limiting size, which was found to be lower at higher stirring speeds. The number of particles formed in the first stage was independent of agitation and other polymerization parameters. The rate of particle formation during the second stage was equal to the rate of particle agglomeration. Thus the total number of primary particles formed was determined almost exclusively by the rate of particle agglomeration. Addition of the surfactant Span 20 caused an increase in the total number of primary particles. Also, this addition increased the tendency of the particles to fuse together after agglomeration. These effects can be understood to be a consequence of particle destabilization by the surfactant. When a small amount of a high molecular weight PMMA was dissolved in the monomer, the polymerization behaved quite differently. In this case, the primary particles were prevented from agglomeration, reaching a limiting size independent of stirring speed.

ISSN:0021-8995    

DOI:10.1002/app.1988.070350106

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

年代:1988

数据来源: WILEY

摘要:

AbstractPolyester resins were prepared by the reaction ofp‐carboxysuccinanilic acid ethyl ester with ethylene glycol and 1,4‐butenediol. Also, unsaturated polyester resins were prepared by the copolymerization ofp‐carboxysuccinanilic acid ethyl ester and maleic anhydride with ethylene glycol, 1,6‐hexanediol, 1,4‐butenediol, and 2‐butyne‐1,4‐diol. All the polyester resins and the copolyesters have been characterized and were found to cure with styrene, except those prepared in the absence of maleic anhydride. The properties of the cured products in the form of films were determined. Infrared and nuclear magnetic resonance (NMR) spectroscopy were used for both qualitative and quantitative analyses of the polyester resins and their hydrolyzate products after curi

ISSN:0021-8995    

DOI:10.1002/app.1988.070350107

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe synthesis of a new aliphatic–aromatic polythioesters obtained by polycondensation of 4,5‐di(mercaptomethyl)–1,2‐dimethylbenzene,4,6‐di(mercaptomethyl)–1,3‐dimethylbenzene and 2,5‐di(mercaptomethyl)–1,4‐dimethylbenzene with adipoyl and sebacoyl chloride is described. To define the optimal condition of the process, the polythioester from 2,5‐di(mercaptomethyl)–1,4‐dimethylbenzene and sebacoyl chloride was chosen as a model system and obtained by interfacial polycondensation as well as by low‐ and high‐temperature solution polycondensation. To determine the optimal conditions for polycondensation the following parameters have been studied: kind of organic solvent, concentration of reagents, temperature and time of reaction and, in the case of interfacial polycondensation additional, ratio of aqueous to organic phase, kind and concentration of hydrochloride acceptor, and kind and concentration of catalyst were taken into consideration. The quality of the obtained polycondensates was estimated on the basis of values of the reduced viscosity and yield. The structure of the aliphatic–aromatic polythioesters was determined from elementary analysis, infrared spectra, and X‐ray analysis. Some thermal, mechanical, electrical, and chemical properties as well as molecular weights of obtained pol

ISSN:0021-8995    

DOI:10.1002/app.1988.070350108

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe crosslinking reaction of an epoxy‐based resin has been monitored by observing the time evolution of the thermal diffusivity of the mixture, using photoacoustic spectroscopy. The results are interpreted in terms of the expected thermal properties of liquids, polymers and solids, and a comparison with the reported viscosity behavior in similar systems is also made. The potential of the technique for following the curing process is discusse

ISSN:0021-8995    

DOI:10.1002/app.1988.070350109

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

年代:1988

数据来源: WILEY

摘要:

AbstractMethoxypoly(ethylene glycohol) methacrylate was grafted onto polyacrylonitrile in dimethylsulfoxide solution via thioamide formation, where ammonium peroxydisulfate was used as an initiator. Optimum conditions for the graft copolymerization, such as degree of thioamidation of the trunk polymer, feeding concentration of the acrylate and the trunk polymer, and temperature were examined. Also the rate of graft polymerization was found to be proportional to concentrations of the acrylate and the trunk polymer. An increase of the degree of the grafting increased water content of the graft copolymer and decreased interfacial free energy between the copolymer and water.In vivotests showed that the graft copolymer obtained was highly nonthrombogenic.

ISSN:0021-8995    

DOI:10.1002/app.1988.070350110

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

年代:1988

数据来源: WILEY