摘要:

AbstractThe aqueous polymerization of tetrafluoroethylene initiated with ammonium persulfate in neutral or relatively weak acid solutions leads to polymer containing carboxyl end groups. The conversion of this endgroup to the sodium salt and its pyrolysis to the terminal olefin was followed, using infrared absorption technique.

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813401

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractA study has been made of the wettability of thin films of polyethylene by observing the equilibrium advancing contact angle formed by a drop of liquid on the surface. Treatment of polyethylene film by exposure to methane/oxygen flames of varying intensity produces a controllable increase in the polarity of the surface as measured by the contact angles with a series of solutions of ethyl alcohol in water. The surface tension lowering of water by ethyl alcohol required to give complete spreading was determined for each flaming condition and related to the adhesion of a polar printing ink. It is shown that an essential criterion for good ink adhesion is the complete wetting of the film surface by the ink. It is suggested that a simple measure of the efficacy of the preprinting treatment would be the contact angle of water with the film.

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813402

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractPolyethylene pinate‐4,4′‐biphenyldicarboxylate, polyethylene homopinate‐4,4′‐biphenyldicarboxylate, and polyethylene pinate‐terephthalate interpolymers were all prepared on a laboratory scale by ester‐interchange reactions. The polymer, fiber and film‐forming properties were examined. In the biphenyl systems, little difference was noted between pinate and homopinate; both formed filaments and films in the 40‐70 mole‐% pinic ranges. In the pinate‐terephthalate system this occurred in the 0‐40 mole‐% pinic range only. Both pinic and homopinic esters are thermally stable at polymerization temperatures of 250‐290 °C. for the time necessary to form high molecular weight interpolyesters. Their internal plasticization of highly crystalline, aromatic systems is useful in controlling the properties of interpolyesters from these systems. The crystalline melting points of polyethylene pinate‐terephthalate was a continuous, almost straight line relationship over the composition range studied. In the biphenyl systems, a discontinuity appeared in the melting point‐composition curves at 30‐40 mole‐% pinate or homopinate concentration. Possible reasons for this are suggested. An analytical method for determining 4

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813403

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractCetyl pyridinium hyaluronate was prepared, and some of its main physicochemical characteristics were studied in nonaqueous media. The following parameters were obtained: sedimentation constant,D20= 3.8S; diffusion constant,D20= 1.0 × 10−7cm.2/sec.; partial specific volume,V= 0.86 cc./g. From these data were calculated molecular weight,M= 289,000; frictional ratio,f/fo= 2.4, corresponding to a molecular asymmetry ofL/d30; and finally, a molecular length of 900 A. Using a velocity gradient range of 2,500 to 15,000 see.−1, a molecular length of 2400 to 3100 A. was obtained with the double refraction of flow apparatus. The difference between the molecular length obtained by ultracentrifugal analysis and that obtained by the flow birefringence technique was attributed to an unfolding of the molecule under shearing stress. This view is supported by the calculation of the internal viscosity of cetyl pyridinium hyaluronate according to the method of Cerf. This was found to be ηi= 9.4 × 10−2. The stoichiometric reaction between hyaluronic acid and cetyl pyridinium chloride yields a derivative which, though differing significantly in some respects, still retains certain similarities to the naturally occurring polysaccharide. The electrical properties of hyaluronic acid are altered when sodium ions are replaced by the cetyl pyridinium group, and the material is no longer soluble in aqueous medium. Even with this structural modification, the molecule behaves in the manner characteristic of highly asymmetric particles. The sedimentation and diffusion patterns, like those of sodium hyaluronate, are positively skewed, indicating a polydisperse distribution which favors the higher molecular weight co

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813404

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractA nonstatistical theory has been developed to account for the heat, entropy, and free energy changes accompanying the formation of binary non‐electrolyte solutions, and for associated thermodynamic properties such as activities, activity coefficients, osmotic pressures, and light‐scattering behavior. The theory considers the volume changes occurring during solution, the effective volume occupied by the molecules, their relative size, and their interactions as a function of temperature and concentration. Since the approach was general in character, the theory should be applicable to polymer solutions as well as to solutions of low molecular weight substan

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813405

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractIn this communication, equations are developed which allow the calculation of well defined average molecular weights and molecular weight distributions for unfractionated polydisperse polymer systems by appropriate combinations of the results of sedimentation, viscosity, and diffusion measurements. This theoretical approach is based upon the existence, for the polymer‐solvent system being studied, of a simple equation relating molecular weight to sedimentation coefficient. The particular equation chosen in this communication is the relationM=ASγwhereMandSare the molecular weight and the sedimentation coefficient, respectively, andAand γ are constants for polymer‐solvent system being studied. The equations developed show how the constantsAand γ may be determined from measurement of other hydrodynamic properties such as the diffusion coefficient and the intrinsic viscosity of the unfractionated system. Systems which are homogeneous with respect to molecular weight but polydisperse in shape are also considered, and equations are developed for determining the molecular weight of such preparations. Finally, systems polydisperse both with respect to shape and molecular weight are examined, and a possible method for the molecular weight characterization of such systems is pre

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813406

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe photolysis of films of polyethylene terephthalate has been studied over a wide variation of exposure conditions. The rate of polymer bond rupture was measured by the change in molecular weight. The rate of energy absorption upon exposure to near ultraviolet light was determined from an analysis of the emission characteristics of the light sources used and the absorption characteristics of the polymer. The overall quantum yield for the photolysis was found to be 5 × 10−4bonds ruptured per photon. This quantum yield is shown to be independent of the wave length of the light absorbed in the spectral region studied. Further, analysis of the effect of film thickness on the rate of bond rupture indicates that the reactions are initiated only by the light absorbed in the strong ultraviolet absorption band characteristic of the pure polymer. The quantum yields for the photolysis of this polymer and others reported in the literature are compared and related to the effect of changes in physical state on the reactions of simple monomeric systems. It is concluded that the low values typical of many polymers are a result of rapid recombination of free radicals due to a low mobility in the solid sta

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813407

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractDilatometers of simple design were used to determine the relationship between specific volume and temperature for several different kinds of polyethylene: samples with densities of approximately 0.91 and 0.96 made at high and low pressures, respectively, and samples of low‐density material which had been irradiated with 106−108roentgens supplied by 800‐kv. electrons. It was found that polyethylene made at low pressures is not only more crystalline than that made at high pressures, but also that it melts much more sharply. Despite the fact that irradiation raises the softening temperature of polyethylene, we have shown that the melting point of the crystalline regions of polyethylene is not thereby increased. It was found that in highly irradiated polyethylenes, the volume change with temperature deviates from linearity at 150°C. and rises rapidly at

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813408

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe melt index apparatus has been adapted for use as a simple rheometer. Changes in orifice diameter from 0.0425 to 0.2000 in. and in weight applied to the piston from 250 to 3250 g. permit an effective range of shear stress from 104to 106dynes/cm.2With this apparatus, the fluidity of polyethylene as a function of shear stress was shown to be a linear function of the shear stress in the range studied. Consistent data using different orifices were obtained by correcting for the friction between piston and barrel. It was found that two parameters, the fluidity at zero shear rate and the shear‐stress dependence of fluidity, are sufficient for the characterization of the flow behavior of polyethylenes. In order to account for the effect of temperature on the shear dependence of viscous flow, as determined from measurements at several temperatures, two activation energies are needed, one corresponding to each of the two parameters mentione

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813409

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe polymerization of acrylamide initiated by ceric nitrate and 3‐chloro‐1‐propanol was studied in aqueous solution at 25°C. At constant hydrogen ion and nitrate ion concentration, the rate of polymerization was found to be independent of the ceric ion concentration. The molecular weight of the polymer was very low. To explain the data, a kinetic scheme is proposed whereby ceric ions are responsible for both initiation and termination. The rate constant for oxidative termination was found to be of the order of 105l. mole−1sec.−1and varied with the hydrogen ion and the nitrate ion conc

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203813410

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY