摘要:

AbstractEthylene–propylene (EP) copolymers were fractionated according to chemical composition, molecular weight, or monomer sequence length, which are fundamental distribution factors. Cloud points of polyethylene (PE), polypropylene (PP), and EP copolymer were determined prior to the fractionation. From the results, it was estimated that xylene–butyl cellosolve and tetralin–ethyl carbitol systems were suitable for the fractionations according to chemical composition and molecular weight, respectively. EP random‐type copolymers were fractionated using a xylene–butyl cellosolve system. Separations according to chemical composition were obtained as expected. Then, the above polymer fractions were further fractionated in a tetralin–ethyl carbitol system. and the dependence on molecular weight was observed fairly well. Furthermore, fractionation according to monomer sequence length was satisfactorily achieved by solvent extraction using ethyl ether,n‐hexane, cyclohexane, andn‐heptane. Therefore, it is concluded that the more detailed characterizations of EP copolymers are made possible by a combination of t

ISSN:0021-8995    

DOI:10.1002/app.1973.070170201

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

年代:1973

数据来源: WILEY

摘要:

AbstractDegradation of friction‐reducing effectiveness of dilute poly(ethylene oxide) solutions subjected to continuous agitation is examined in disk flow. A residual or steady‐state effectiveness is observed which disappears only at a sufficiently high Reynolds number. The onset of friction reduction appears to occur within the transition region and seems to be independent of solution concentration. The onset of degradation also appears to be independent of concentration. Prior shear working is shown to have a significant effect on residual friction‐reducing effectiveness only when the shear working is performed in a more intense shear field than that in which the friction‐reducing effectiveness is evaluated. Degradation of friction‐reducing effectiveness is compared to corresponding changes in viscosity‐average molecular weight. The experimental results are interpreted in terms of a model of the interaction between polymer molecules and the turbulent

ISSN:0021-8995    

DOI:10.1002/app.1973.070170202

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe diffusion coefficientsDfor solvating liquids and vapors in membranes can be measured in a number of ways. The effectiveness of permeation methods for systems involving semicrystalline polymers at near‐ambient temperatures has been assessed, and new experiments have been performed usingp‐xylene and high‐density polyethylene. The conclusions are likely to apply to any semicrystalline polymer where the diffusant concentration is not zero. Stresses induced in the downstream side of the membrane by solvent sorption at the upstream surface during the nonsteady period are shown to lead to underestimation ofD. The rate of attainment of a steady state is controlled primarily by the rate at which these stresses relax. The extremely slow rate of stress relaxation in polyethylene implies that, under many experimental conditions, a true steady state of permeation is not attained within an experimentally accessible time, a conclusion supported by experimental evidence. Diffusion coefficients calculated in the usual way from apparently steady‐state permeation rates may be grossly underestimated. In liquid permeation experiments, some of the polymer may dissolve in the upstream permeant, and this may lead to overestimation both of the time to reach an apparently steady state and of the steady‐state permeation ra

ISSN:0021-8995    

DOI:10.1002/app.1973.070170203

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

年代:1973

数据来源: WILEY

摘要:

AbstractA difunctional hydroxyl‐terminated polybutadiene (sample A) was characterized by light scattering (LS), vapor pressure osmometry (VPO), and gel permeation chromatography (GPC). Sample A was then esterified, and the product (sample B) was also characterized. Light‐scattering measurements were carried out in different solvents (some were theta solvents for polybutadiene), and the results were corrected for anisotropy. Values ofMn(3100) andMw(8000) determined respectively by VPO and LS for samples A and B were similar to those computed by GPC using two sets of columns of different resolution. The value of 2.3 found for the polydispersity indexMw/Mnis higher than the value which is usually reported by other workers (ca. 1.3 to 1.7) for functionally terminated polybutadie

ISSN:0021-8995    

DOI:10.1002/app.1973.070170204

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

年代:1973

数据来源: WILEY

摘要:

AbstractSorption by wool of mercuric nitrate, mercuric chloride, and methylmercuric chloride was measured by atomic absorption spectroscopy. Both inorganic mercury compounds are efficiently taken up at low concentrations from acid solution. The rate of binding from the nitrate is appreciably slower than from the chloride. Methylmercuric chloride is bound slowly at low pH, rapidly at pH 6. The extent of its binding is roughly 10% to 20% of that of the inorganic salts. The wool‐bound mercury can be recovered by serial extraction with aqueous citrate or ethylenediaminetetraacetate at pH 6. The residual, firmly bound mercury is roughly equivalent to the sulfhydryl sulfur. Sorption of inorganic mercury compounds at low pH roughly follows a Freundlich isotherm in the concentration range 5×10‐6to 10−1M. Sorption of methylmercurie chloride at pH 6 follows a roughly parallel isotherm in the range 5×10−6to 10−3M. These data suggest the potential value of wool and other animal keratins to remove and recover mercury from contaminated water. Wool may also serve as an instructive model for mercury binding and release

ISSN:0021-8995    

DOI:10.1002/app.1973.070170205

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

年代:1973

数据来源: WILEY

摘要:

AbstractAn important product, C5H6O2, from the pyrolytic decomposition of phosphoric acid, treated cellulose was isolated and identified ascis‐4,5‐epoxy‐2‐pentenal. NMR, IR UV, and mass‐spectral data of this product were analyzed and discussed. A method for the preparation ofcis‐4,5‐epoxy‐2‐pentenal is presented, and a mechanism for its form

ISSN:0021-8995    

DOI:10.1002/app.1973.070170206

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

年代:1973

数据来源: WILEY

摘要:

AbstractPoly(p‐methylstyrene) films have been irradiated with 253.7‐nm radiation under high vacuum at 25°C. The main reaction product is hydrogen, but methane and traces of ethane and monomer were also detected. The quantum yield for H2production (6 × 10‐2) is considerably greater than that for polystyrene photolysis indicating that both α‐CH bonds undergo fission. Solubility measurements also indicated the participation by thep‐methyl group. Main‐chain conjugation and coloration occur and are attributable to hydrogen abstraction from the β‐carbon atom. Cyclohexadienyl compounds are also formed and are presumably associated with crosslinking involving addition to the benzene ring. The mechanisms of photochemical and photophysical proc

ISSN:0021-8995    

DOI:10.1002/app.1973.070170207

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe drag reduction (DR) of dispersions of Chrysotile asbestos fibers in aqueous solutions of Aerosol OT and in ethylene glycol, and of glass microfibers in water at a pH of 3 were studied as a function of concentration and temperature with a rotating disc apparatus. Only the dispersions of asbestos in aqueous Aerosol OT showed DR comparable to poly(ethylene oxide) WSR 35 (∼500,000 MW), and these dispersions were more fully studied. As was the case with Polyox WSR 35, the asbestos dispersions achieved maximum DR at a concentration of about 200 ppm. They showed no DR temperature dependence at constant Reynolds number at high concentrations but displayed a decreasing DR with increasing temperatures at low concentrations. However, the temperature effect was much smaller for the asbestos dispersions than for Polyox. The asbestos dispersions also showed a much smaller decrease of DR with time at a given disc rotation than was previously measured for poly(ethylene oxide). Electron microscope evidence indicated that less than 10% of the fibers were fully separated, and it is probable that these were the fibers which were primarily active in DR. Hence, if complete separation and dispersion could be accomplished without breaking the fibers, Chrysotile asbestos would be a most potent, not very shear‐degradable DR spec

ISSN:0021-8995    

DOI:10.1002/app.1973.070170208

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe transport properties of polymer membranes in various forms which have a wide variety of practical applications, such as ultrafiltration, dialysis and blood oxygenation, depend upon the structure (homogeneous or heterogeneous) and the transport characteristics of the membrane material. Among many possible driving forces of transport, the pressure gradient and the concentration gradient are considered to be the most general forces encountered in practical use of polymer membranes. The transport of various permeants (gas, dissolved gas, liquid solvent, and solute) through porous and homogeneous (nonporous) polymer membranes under these driving forces is discussed. In the absence of a pressure gradient, the transport of permeants can be described as diffusion, regardless of the permeant phase and the membrane structure. In the presence of a pressure gradient, the transport of permeants may occur by diffusion and/or bulk flow of the permeants, depending upon the membrane structure and the nature of the permeant. In homogeneous membranes, many noninteracting permeants such as gases and nonsolvent vapors permeate by diffusion under applied pressure gradient: however, solvent in homogeneously swollen membranes moves by bulk flow and the diffusion depending on the degree of swelling of the membrane. In heterogeneous membranes under applied pressure, most permeants move by bulk flow.

ISSN:0021-8995    

DOI:10.1002/app.1973.070170209

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe effect of addition of lignin model compounds on the polymerization rate and molecular weight of polymer in the radiation‐induced polymerization of styrene was studied. Guaiacol, a model for softwood lignin, reacted slowly with styrene radicals, while 2,6‐dimethoxyphenol, a hardwood lignin model, was a much more efficient chain transfer agent. Studies with isoeugenol indicate that allylic or phenoxy radical stability in a conjugated system may terminate polymerization quite effectively. The results are discussed in the light of new and previous data with isolated lignins; they are consistent with the previously presented grafting sch

ISSN:0021-8995    

DOI:10.1002/app.1973.070170210

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

年代:1973

数据来源: WILEY