摘要:

AbstractThe accuracy of the parallel‐plate approximation to represent various viscous flows of non‐Newtonian fluids between coaxial cylinders is investigated. Four types of flow are considered: tangential drag flow, tangential pressure flow, and axial pressure flow. The solutions for flow between parallel plates are compared with the exact solutions, and the errors are plotted against radius ratio for a number of values of the power‐law index to provide an indication of the range of usefulness of the parallel‐plate

ISSN:0021-8995    

DOI:10.1002/app.1979.070240201

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe construction and function of an apparatus for the determination of gas permeability through metallized polymer films is described. The test gases N2, O2, and CO2penetrate under pressure differences from 100 torr to 20 bar through galvanized ABS films (acrylonitrile–butadiene–styrene copolymer). The metallic layers consists of chemically deposited Ni and a galvanic deposited Cu having a thickness of 2–30 μm. The quantity of permeated gases is determined by gas chromatography. The lowest permeability coefficient obtained is 10−17(cm3cm/cm2sec torr). Leak effects can be measured quantitatively. The permeability of gas mixtures (i.e., air) can also be investigated. The apparatus allows the determination of extremely low permeability rates as well as those for conventional polymer

ISSN:0021-8995    

DOI:10.1002/app.1979.070240202

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe rates of the individual reactions of 2‐methylol‐4‐t‐butylphenol with 4‐t‐butylphenol were measured under varying mole ratios of reactants in the presence of different acid catalysts (5.0 × 10−3Nto 2.0 × 10−4N) at five different temperatures (60, 65, 70, 75, and 80°C). In all the experiments, the reactions were found to obey second‐order rate law. The values of the Arrhenius parameters and the entropy of activation for the overall reaction were calculated. The relative catalytic efficiencies of the acid catalysts followed the

ISSN:0021-8995    

DOI:10.1002/app.1979.070240203

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

年代:1979

数据来源: WILEY

摘要:

AbstractA new method of preparing rubber powders, especially masterbatch powders, is described. It consists of the dispersion of polymer latices in highly hydrophobic fine particle‐size powders such as special silicas and carbon black, followed by drying. During the whole procedure the powders never lose their pourable state. Several powder properties, e.g., particle size distribution, pourability, bulk density, and angle of repose, are dealt with for NR and SBR powders. These powders require a high shear processing stage to disperse the black and rubber chemicals into the rubber matrix. For direct extruder feeding, a highly efficient extruder mixing screw is necessary. It is shown that the powders can be sufficiently protected against aging by use of special antioxidants. The procedure is characterized by an outstanding simplicity in respect to engineering and equipment. The future outcome of the method will depend on the balance between that simplicity and the energy demand which can be tolerate

ISSN:0021-8995    

DOI:10.1002/app.1979.070240204

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe rate at which an additive is lost from the surface of its solution in a polymer is considered to depend upon three factors—the solubility of the additive, the rate at which it volatilizes from the polymer surface, and its diffusion coefficient within the bulk of the polymer. By adapting the mathematics of heat flow in a solid, the loss of additive from a polymer is mathematically modeled in terms of these three variables for bulk polymer and for film and fiber samples. Two cases are considered—loss of additive by volatilization or dissolution from the polymer surface and loss by precipitation on the surface from a supersaturated solution of the additive. The results are applied to a discussion of the relative importance of the three parameters under various conditions occurring or expected in practical application of additives as oxidation stabilizers for polyethylene and polypropyl

ISSN:0021-8995    

DOI:10.1002/app.1979.070240205

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe maximum crosslink density for the dioxime‐butyl vulcanizate was obtained at equimolar quantity of the dioxime and red lead. The formation of each quinoid crosslink required about 1.25 molecule ofp‐quinone dioxime dibenzoate. The vulcanizates consisted mainly of the anil‐type crosslink. It was estimated that about 20% of the combined dinitro compounds was wasted in the form of the pendent groups. The vulcanization mechanisms are also disc

ISSN:0021-8995    

DOI:10.1002/app.1979.070240206

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

年代:1979

数据来源: WILEY

摘要:

AbstractOxidation of cotton cellulose with potassium periodate, potassium dichromate‐sulfuric acid, and potassium dichromate‐oxalic acid results in creation of variable amounts of acidic and reducing groups along the cellulose molecule, being dependent upon the type of oxidizing agent used. Such groups were found to have a profound effect on the acceptability of cellulose for reactive and direct dyes. The rate and extent of dye uptake for the oxidized celluloses were significantly lower than those of the unoxidized cellulose. While presence of the acidic groups in cellulose molecules induces a negative environment thereby making approach of the dye anions to the cellulose difficult, presence of the reducing groups lowers the magnitude of cellulose reactivity as well as decreasing its adsorptive power. Further modification of the oxidized celluloses via either borohydride or chlorous acid treatment brought about modified celluloses the dyeability of which confirms the inhibiting effect of the acidic and reducing groups of those oxidized celluloses on the rate and extent of dyeing with reactive and direct d

ISSN:0021-8995    

DOI:10.1002/app.1979.070240207

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe Benoit universal calibration method has been tested for evaluation of GPC data of polydimethylsiloxane (PDMS) in toluene at 60°C. For the conversion of the calibration curve for polystyrene to the PDMS calibration curve, the Mark–Houwink equation for PDMS in toluene at 60°C was derived: [η] = 9.77 × 10−5M0.725. The applicability of this universal calibration was proved by the experimental results on five PDMS model samples. For the correct evaluation of the PDMS elution curve, the use of the true calibration is inevitable, because the hydrodynamic volume of PDMS molecular weight unit is somewhat different from the polystyr

ISSN:0021-8995    

DOI:10.1002/app.1979.070240208

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe possibilities of comparing the GPC curves of two or more polymers were studied, and the method of “distinguished points” (DPs) is suggested for this purpose. The features of these DP values as random variables were investigated. According to the experimental results they meet the requirements of the statistical tests applied in this text. In order to indicate the significant deviation or the agreement of the DP values of GPC curves of two polymers, the sequentialUandttests are suggested, because with these methods the number of the necessary parallel measurements is considerably decreased, and one can also decide on the magnitude of the variation on must be able to detect, while in the case of more than two polymers the methods of the analysis of variance can be utilized. The molecular weight ranges in which significant differences occur can also be determined. The described methods were tested by materials of known molecular weight distributi

ISSN:0021-8995    

DOI:10.1002/app.1979.070240209

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

年代:1979

数据来源: WILEY

摘要:

AbstractPoly(methyl methacrylate)–lead silicate composites were prepared with different amounts of crystalline or amorphous PbO–SiO2binary composition (70 mole % PbO). The polymerization reaction was carried out in aqueous medium and in methanol–water mixture at 40°C using sodium bisulfite as initiator. The presence of lead silicate was found to increase the molecular weight of the poly(methyl methacrylate). The prepared composites were characterized by studying their shielding properties to γ radiation, mechanical hardness, dielectric constant, and thermal stability. It was found that lead silicate increases the absorbing power of the composites to γ radiation. This behavior was found to be dependent on the amount and the type of lead silicate (amorphous or crystalline). Gamma irradiation of the composites was found to cause chemical degradation of the poly(methyl methacrylate) leading to a decrease in mechanical hardness. Molecular weights of the poly(methyl methacrylate) for some of the composites were determined before and after irradiation viscosimetrically. Dielectric constants for some of the composites were determined at two different temperatures. The thermal stability of the composites was studied by means of an automatic thermogravimetric

ISSN:0021-8995    

DOI:10.1002/app.1979.070240210

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

年代:1979

数据来源: WILEY