摘要:

AbstractThe rate of isomerization during the polyesterification of maleic acid or maleic anhydride depends on the structure of the glycol used: the longer the chain of the glycol, the lower the isomerization rate. The rate constants differ greatly from one case to another. Thus, the difference in the reaction rate constants depends mainly on the steric effects caused by the different types of glycols used in the polycondensation. The isomerization approaches a constant value, which after a certain time depends on the structure of the glycol and the temperature of the condensation. The activation energies calculated from the rate constants would fall at about 20 ± 4 kcal./mole. This value for the activation energy corresponds to that reported in the literature for the transformation of maleic acid into fumaric acid. The reaction apparently follows second‐order kinetics due to the catalytic effect of the maleic acid on the isomerizati

ISSN:0021-8995    

DOI:10.1002/app.1966.070100401

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe common assumption in the literature is that amine complexes of Lewis acids (particularly boron trifluoride) cure epoxy resins by virtue of their dissociation to liberate the Lewis acid which then functions as the “true” catalyst. Evidence is presented to indicate that this picture of amine–Lewis acid complex curing may be incorrect. Another mechanism is proposed which is consistent with (a) lack of correlation between adduct stability and reactivity, (b) a similarity in reactivity of BF3adducts and the corresponding fluoroborate salts, (c) the relationship between reactivity of BF3and PF5adducts, (d) a correlation between reactivity and structure of the amine in the complex, and (e) the effect of the anion on reactivity of amine salts. The relative reactivity of the catalysts has been equated with the temperature at which gelation occurs on heating at a fairly constant

ISSN:0021-8995    

DOI:10.1002/app.1966.070100402

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

年代:1966

数据来源: WILEY

摘要:

AbstractDimethyl‐, trifluoropropyl‐, and high phenyl content polysiloxanes were irradiated in a60Co source to doses of 100 Mrad. The hardness of the specimens increased with dose. Crosslink density changes did not directly reflect the hardness changes. The crosslink density of the dimethyl polymer increased significantly and that of the trifluoropropyl polymer increased only slightly. There was a slight decrease in the crosslink density of the aromatic material. The storage moduli reflected the changes in crosslink density. Loss moduli of the dimethyl‐ and trifluoropropylpolysiloxanes initially decreased and then increased on continuing irradiation. Dynamic moduli of the high aromatic content polymer were essentially unchanged by the radiation. All the dynamic data were correlated by the WLF time–temperature relat

ISSN:0021-8995    

DOI:10.1002/app.1966.070100403

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe polymerization of vinylcarbazole in aqueous dispersion by azobisisobutyronitrile can yield–depending on the protective colloid used–polyvinylcarbazole beads or granules. These require impregnation by a polymer solvent and preferably also by azobisisobutyronitrile before they can be molded to panels or simple sha

ISSN:0021-8995    

DOI:10.1002/app.1966.070100404

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe uniformity, heat and solvent resistance, and thermal conductivity of foamed polyvinylcarbazole have been examined. Compressive and tensile properties, dielectric constant, and loss factor have been determined between ambient temperature and the softening range. Some features of the properties are attributed to the degree of orientation of the polymer molecules, which is thought to be the greater, the lower the density of the foam. The good high temperature stability is attributed to sterically impeded reversibility of the polymerization of vinylcarbazole.

ISSN:0021-8995    

DOI:10.1002/app.1966.070100405

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

年代:1966

数据来源: WILEY

摘要:

AbstractTires containing nylon tire cord exhibit a temporary deformation upon standing under load. The delayed recovery from this deformation, due to the fact that the yield point of nylon is exceeded under normal inflation pressures, results in the phenomenon of “flatspotting.” Previous attempts to improve the viscoelastic characteristics of nylon by crosslinking have been discouraging on account of the general degradation of properties caused by the treatment. It has now been found that short, vapor‐phase treatments with diisocyanates, particularly tolylene diisocyanate, produce nylon 6 of greatly improved flatspotting resistance, without undersirable side effects. The development of this procedure, the evaluation methods employed, and the proposed mechanism are disc

ISSN:0021-8995    

DOI:10.1002/app.1966.070100406

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe degradation of phenol–formaldehyde polycondensates has been investigated by mass spectrometric thermal analysis to 800°C. The thermal oxidative mechanism proposed by Conley and co‐workers has been confirmed. Direct analysis of products at frequent intervals of a temperature‐programmed heating cycle demonstrates the existence of postcuring, general degradation, and char‐forming stages. Activation energies for formation of each product and for degradation of the polymer have been determined. Phenolic homologs, products of thermal scission of methylene–phenyl bonds, show high activation energies; oxidation products have activation energies comparable to or slightly higher than that for oxidation of methylene bridges to carbonyl groups. The tarry high molecular weight products found on pyrolysis at atmospheric pressure are not formed in high vacuum because recombination reactions of phenols and formaldehyde are minimized. Otherwise, no major change in product composition, as compared to the high heating rate pyrolysis–gas chromatographic investigation of Jackson and Conley,

ISSN:0021-8995    

DOI:10.1002/app.1966.070100407

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe changes in nylon 66 fiber structure and properties which take place during drawing and aqueous phenol treatments were studied by means of measurements of length, birefringence, density, moisture regain, x‐ray diffraction, stress–strain behavior, and sound velocity. Drawing was found to establish molecular orientation along the fiber axis predominantly in the early stages, whereas the development of lateral order occured primarily after a certain level of orientation had been achieved. Treatments in aqueous phenol solutions caused longitudinal contractions which depended on phenol concentration (1‐5%), draw ratio (1‐6), and the tension on the fiber during the treatment. The treatments resulted in an increase in the lateral order, decrease in orientation and corresponding changes in mechanical properties. Moisture regain was inversely related with density for the untreated fibers of various draw ratios, but the relationship became complex after treatments in phenol. The data are interpreted in terms of changes in the lateral order distributions, which permits an increase in the fibers' sorptive capacity despite an increase in the mean latera

ISSN:0021-8995    

DOI:10.1002/app.1966.070100408

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

年代:1966

数据来源: WILEY

摘要:

AbstractData are presented relating the time change of the coefficient of friction of cast polypropylene films to changes in film density and concentration of surface lubricant. It is shown that during aging the density of polypropylene increases, thus causing a decrease in the friction coefficient. It is also shown that although the lubricant added to the polymer will diffuse to the surface of copolymer films, no diffusion occurred in polypropylene films.

ISSN:0021-8995    

DOI:10.1002/app.1966.070100409

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

年代:1966

数据来源: WILEY

摘要:

AbstractIn the addition of stabilizing agents to plastic materials, problems such as incompatibility, migration, volatility, and/or solvent extraction of the additive frequently arise. With a view toward overcoming such problems in the use of ultraviolet absorbing stabilizers, acrylate and methacrylate derivatives containing the 2‐hydroxy‐4‐alkoxybenzophenone moiety have been synthesized. The ultraviolet absorbing monomers were synthesized by reaction of 2, 4‐dihydroxybenzophenone with glycidyl acrylate and glycidyl methacrylate. They were homopolymerized and blended with poly(vinyl chloride), poly(vinylidene chloride), polystyrene, and poly(methyl methacrylate). They were also copolymerized with the corresponding monomers. The polymer blends and copolymers were investigated for ultraviolet stability versus corresponding controls. Effective ultraviolet stabilization was observed. Differences in the stability of some blends as compared to corresponding copolymers is thought to be due to incompat

ISSN:0021-8995    

DOI:10.1002/app.1966.070100410

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

年代:1966

数据来源: WILEY