bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relation between birefringence and draw ratio of man‐made fibers
Authors: de Vries H. 
Published: April 2003

AbstractIn the course of our investigations into the relation between draw ratio (i.e., the permanent extension ratio imparted during manufacture) and birefringence of man‐made fibers, we found that the relation published by Kordes et al. for Perlon (nylon 6) has equivalents for several different fibers that may be considered as special cases of one general empirical relation. This empirical relation, expressed in differential form, reads

where Δn = specific birefringence of the fiber, In λ = the natural logarithm of the permanent extension ratio, reckoned from the isotropic state, and m and p are constants. The constant m can assume positive or negative values, according to the sign of the birefringence of the fiber. The values found for p appear also to be characteristic of the polymer. It also appears that the experimental results can be described within experimental error by taking for p multiples of 1/2. This opens the possibility for a comparatively simple way of plotting the results. Thus, apart from the value p = −1/2 corresponding to Kordes' relation, for p the following values, which are multiples of 1/2, viz., −1, −1/2, +1/2, +1, have been found by us (e.g., respectively for nylon 66, polyethylene, polyethylene terephthalate, viscose rayon). These seem to be preferred values of p. So far no case has been found of the values p = 0 and p > ±1. As yet there is no theory forthcoming to explain the empirical relation in its general form nor the apparent rule of preference for the above‐mentioned values of p.
γ‐Irradiation of rubber and styrene. Graft polymer formation
Authors: Turner D. T. 
Published: April 2003

AbstractStyrene, styrene mixed with rubber, and rubber alone have been exposed to γ‐radiation from Co‐60. The G value for polymerization‐initiating radicals formed from rubber in the mixture, G(i.r) = 0.26, has been calculated from corresponding values obtained by estimation of the number of polystyrene molecules formed in styrene and in the mixture. A G (radical) value for rubber when irradiated alone, G(r), has been assessed from a G (crosslinking) value, G(X), which was determined under closely similar experimental conditions, as G(r) = 2G(X) ∼ 6. The large discrepancy between G(r) and G(i.r.) cannot be explained satisfactorily on the supposition that radicals formed from rubber have a low efficiency in initiating the polymerization of styrene. Therefore, it is argued that the G(r) value itself is lower in the mixture. Evidence for this argument is provided by the lower rate of gelling in the mixture. this protection of rubber by energy transfer to styrene is an important example since in only one previous case has experimental evidence been provided to exclude an alternative radical mechanism. By polymerization in the presence of crosslinked rubber, uncombined polystyrene could be readily partioned into the sol fraction by equilibration of the gross polymer in benzene. About 15% of the polystyrene was free. Hexachloroethane was chosen as an example of an additive with a high G (radical) value. As would be expected, it increases the rate of polymerization but does not lead to a correspondingly large amount of free polystyrene (about 23%). Graft polymer formation from styrene and methyl methacrylate is compared and attention is drawn to the importance of the formation and subsequent reactions of initially nonpolymeric radicals in determining the proportion of free plastomer.
Solution studies of some polyethylene samples
Authors: Raman N. K. , Hermans J. J. 
Published: April 2003

AbstractFrom studies on light‐scattering, viscometry, and osmometry in solutions of nonfractionated polyethylenes, it is concluded that none of the samples investigated shows an excessively broad molecular weight distribution. This conclusion is supported by the results obtained fro fractionated samples. The results of osmometry for two fractions confirm the [η]–Mn relation suggested by Trementozzi.
Molecular motion in polyamides
Authors: Slichter W. P. 
Published: April 2003

AbstractIt is well known that aliphatic polyamides with even numbers of methylene groups between amide groups melt at higher temperatures than those with odd numbers of methylene groups. Crystallographic studies in the past have sought to relate the packing of the amide groups to the variations in melting point, but these studies have been made almost exclusively at room temperature. In the present study, series of polyamide fibers were examined by x‐ray diffraction over a wide range of temperatures. In the even‐numbered polyamides, the triclinic structure occurring at room temperature shifts to a more symmetrical structure in which the chains assume hexagonal packing. This latter packing occurs in the odd‐numbered polymers at room temperature. The polar groups in the latter occur in layers which are normal to the chain axes. The layers of polar groups in the even‐numbered polyamides are tilted with respect to the chain axes at room temperature, and remain tilted at high temperatures even though the lateral chain packing becomes the same as the lower‐melting (odd‐numbered) members of the series. The spacing between polar groups along the chain decreases with increasing temperature, but the decrease is relatively less in the even‐numbered than in the odd‐numbered polymers, and is less in the more polar than in the more paraffinic compounds. These changes are ascribed to torsional and rotational motions of chain segments in the crystallites. Proton magnetic resonance studies demonstrate the onset of motion of the hydrocarbon segments and compare qualitatively the constraints to chain motion among isomeric members of the series. Some implications regarding the melting process are discussed.
Mechanism of hydrogen ion catalysis in esterification. II. Studies on the kinetics of polyesterification reactions between dibasic acids and glycols
Authors: Au‐Chin Tang , Kuo‐Sui Yao 
Published: April 2003

AbstractOn the basis of our experimental data and a detailed kinetic analysis, the following mechanism of hydrogen ion catalysis is proposed for polyesterification as well as for the simple esterification reactions:
magnified image
The kinetic equation in terms of [COOH] (= C) is

where C0 = [COOH] and r = [COOH]/[OH] at the time t = 0. All of our data on the polyesterification of succinic acid or adipic acid with ethylene glycol at various molar ratios and at different temperatures, in the presence or absence of a foreign acid, support the above equation. For the special case of r = 1 and in the absenc of a foreign acid, ([H+] = K[COOH]1/2), and polyesterification is hence shown to be a reaction of an order of 2.5. The data of Dostal and Raff, Flory, Davies, and Rafikov and Korshak, have been re‐examined and found to conform to the 2.5‐order relationship over the range of 0 to 92% polyesterification.
The second virial coefficient of polymer solutions
Authors: Koyama Ryuzo 
Published: April 2003

AbstractA theoretical calculation of the temperature dependence of the second virial coefficient of polymer solution is carried out, assuming the Lennard‐Jones potential, φ(S) = φ0[(S0/S)12 − 2(S0/S)6], between two molecular segments of chain polymer molecules in the solution. The result gives a good explanation for the experimental relation between the second virial coefficient, A2 and the temperature, T: A2 = a + (b/T), where b > 0 for good solvents and b < 0 for poor solvents. According to this calculation, the theta point, θ, at which the second virial coefficient vanishes is given by the relation, φ0/kθ = 0.292., and the temperature gradient of A2 at this point is determined by another molecular parameter, SM, where M0 represents the molecular weight of the segment. The theoretical value of the second virial coefficient agrees well with the experimental data of Krigbaum and Flory for polyisobutylene in benzene near the theta point, and it gives a value of about S0 = 10 A. for the dimension of a segment consisting of seven monomer units in the solution. Another method for calculation of the molecular parameters, which employs the experimental data of the second virial coefficient is described. Application of this method to the light scattering data of Outer, Carr, and Zimm, permits calculation of the molecular paramenters of polystyrene in several solvents.
Extraction fractionation of polyvinyl acetate and of polyvinyl alcohol
Authors: Beresniewicz A. 
Published: April 2003

AbstractMethods for rapid fractionation of polyvinyl acetate and of polyvinyl alcohol are described. By a slightly modified Fuchs' extraction technique, polyvinyl acetate can be fractionated into relatively homogeneous fractions. The ratio of osmotically determined M̄n of the nonfractionated sample to that calculated from fractionation data is 1.19. Extraction fractionation of polyvinyl alcohol is complicated by the crystallinity of this polymer. The molecular weight distribution of polyvinyl alcohol can be determined, however, in relatively short time, by first reacetylating the polymer and then fractionating the obtained polyvinyl acetate.
Thermal decomposition of poly(vinyl chloride)
Authors: Stromberg Robert R. , Straus Sidney , Achhammer Bernard G. 
Published: April 2003

AbstractPoly(vinyl chloride), polymerized with the use of γ‐radiation, benzoyl peroxide, and 2,2′‐azobis(isobutyroitrile) as initiators, was thermally decomposed in vacuo. The gaseous decomposition products as analyzed by mass spectrometry consist primarily of hydrogen chloride for decomposition temperatures below approximately 300°C. At temperatures approximating 400°C., various hYdrocarbons are evolved along with the hydrogen chloride. Energetic considerations are discussed and the activition energy is determined. A free radical mechanism for the dehydrochlorination reaction that appears consistent with the reaction rate data for a three‐halves‐order reaction is postulated.
Fractionation of polymers by precipitation chromatography—microtechnique and theory
Authors: Caplan S. R. 
Published: April 2003

AbstractA microcolumn for fractionation by precipitation chromatography is described. It operates in conjunction with a continuous paper‐strip fraction collector, and has been used successfully to fractionate milligram quantities of polysarcosine dimethylamide. Polymer which can either be labelled or dyed may be determined directly on the strip by scanning methods. A semi‐empirical theoretical consideration of the column has resulted in the followimg molecular weight vs. volume relationship (for the case of a single constant volume solvent‐precipitant mixing chamber):

where T2 is the temperature at the, bottom of the column, G is the volume of the mixing chamber, and τ and (σ+τ) may be identified with the Flory temperatures of solvent and precipitant, respectively. This has been found to be a close fit to published data for the fractionation of polystyrene. A comparison of exponential and constant solvent gradients shows that the former are advantageous for very broad distributions, the latter for narrow.
Emulsionspolymerisation des styrols mit radikalbildung in der Ölphase
Authors: Edelhauser H. , Breitenbach J. W. 
Published: April 2003

AbstractBei der Emulsionspolymerisation des Styrols wurde durch Anwendung von öllöslichen Startern bzw. durch rein thermische Polymerisation die Bildung der Radikale aus der Wasserphase in das Monomere verlegt. Hierbei ergab sich eine beträchtliche Erhöhung der Polymerisationsgeschwindigkeit gegenüber der Polymerisation in homogener Phase, die nur durch die Isolierung einzelner wachsender Ketten in Latexpartikeln bedingt sein kann. Dass trotz paarweiser Erzeugung der Radikale in der Öphase Latexpartikel entstehen, die nur eine wachsende Kette enthalten, wird auf eine verhältnismässig rasch verlaufende Diffusion der primär gebildeten niedrigmolekularen Radikale aus der Öphase in die Wasserphase zurüchgeführt, von wo sie dann einzeln in Mizellen bzw. Latexpartikel eintreten könuen. Der Einfluss einer solchen intermicellaren Diffusion niedrigmolekularer Radikale—womit die Isolierung in Mizellen bzw. Latexpartikeln nur mehr für makromolekulare Radikale vollständig wäre—auf die Abbruchsgeschwindigkeit in der Emulsionspolymerisation bei Kettenübertragung wird diskutiert. Für die thermische Styrolpolymerisation ist ein Diradikalmechanismus auf Grund der Unter suchungsergebnisse unwahrscheinlich.
The effect of inorganic electrolytes on the denaturation of arachin with urea and guanidinium salts
Authors: Naismith W. E. F. , Williams R. K. 
Published: April 2003

AbstractThe effect of a number of electrolytes on the denaturation of arachin with urea and guanidinium chloride has been examined by ultracentrifuge and viscosity techniques. With urea, all the sodium salts studied retarded the denaturation. With guanidinium chloride, however, it appeared that a salt accelerated or retarded the denaturation depending upon whether the guanidinium salt with the anion of the salt in question denatured arachin more rapidly or more slowly than guanidinium. chloride. The effect of some other guanidinium salts on the sedimentation of arachin is also briefly reported.
Phase equilibria in ternary systems containing a solvent a linear polymer, and a crosslinked polymer
Authors: Sakurada Ichiro , Nakajima Akio , Aoki Hirosi 
Published: April 2003

AbstractThe equilibrium compositions of gels obtained by swelling crosslinked poly(vinyl acetate) of each of the following solutions, at various concentrations, were determined: linear low‐polymeric poly(vinyl acetate) in ethyl acetate, linear low‐polymeric poly‐(methyl acrylate) in ethyl acetate, linear low‐polymeric polystyrene in benzene. From these data, the interaction parameters χij for pairs of the components were deduced and compared with each other and with comparable constants from the literature.
Polymer and group interactions. VII. Lactonization of polyethyl α‐chloroacrylate
Authors: Smets G. , Flore P. 
Published: April 2003

AbstractPolyethyl α‐chloroacrylate (PCA) has been condensed in the presence of aluminum chloride and aromatic hydrocarbons; the molar ratio AICl3/PCA was usually higher than unity. Although the halogen content decreases with a higher degree of conversion, no aromatic hydrocarbons are incorporated into the polymer. The reaction proceeds through a nucleophilic substitution mechanism with intramolecular lactonization; the polymer composition has been calculated from the halogen content and the conductometric titration of free acid and lactone rings after opening. The degrees of polymerization of the reaction products were determined by the osmotic method in order to evaluate the importance of the chain degradation during the condensation. In spite of the high condensation temperature and the high degree of conversion, the degrees of polymerization are about 40–50% of that of the initial PCA. While the limited viscosity numbers vary only slightly, the Huggins‐Schulz k′ constant values decrease regularly with an increasing degree of lactonization.
Fractionation of polyethylene
Authors: Henry Patrick M. 
Published: April 2003

AbstractA procedure and apparatus are described for the large scale (50‐gram) fractionation of high‐density polyethylene by Desreaux's fractional extraction technique. Two samples of Ziegler polyethylene were fractionated by this technique and the intrinsic viscosity in decalin at 135°C. and molecular weight by light scattering were measured on the fractions. The relationship [η] = 4.6 × 10−4 M̄w0.73 was found to hold for molecular weights between 25,000 and 640,000. The samples differed in polydispersity, one having a broad distribution and the other a rather narrow distribution. Evidence for the sharpness of the fractions obtained by the new technique was provided by refractionating of one fraction and the resolation of two fractions which were combined and refractionated.
Radiochemical studies of free‐radical vinyl polymerizations. Part I. The nature of the initiation and termination processes in methyl methacrylate and styrene polymerizations using C14‐labeled initiators
Authors: Ayrey G. , Moore C. G. 
Published: April 2003

AbstractC14‐Labeled initiators, viz., di‐(ar‐C14)‐benzoyl peroxide, di‐(carboxyl‐C14)‐benzoyl peroxide, and C14‐azobisisobutyronitrile (AZBN), have been used to initiate the polymerization of methyl methaerylate at 60°C. in benzene. Determination of the rates of polymerization, and the molecular weights (M̄n) and C14‐contents of the resultant polymers permits the following conclusions to be made. (1) Rates of initiation by benzoyl peroxide and AZBN are given by the equations, Ri = 5.15 × 10−6 [Bz2O2] mole l.−1 sec.−1 and Ri = 1.17 × 10−5[AZBN] mole l.−1 sec.−1, respectively. (2) The initiator efficiency, f, for AZBN is 0.50; f for benzoyl peroxide cannot be evaluated in the absence of a reliable kd value for this compound in the present system. (3) Initiation is solely by addition of initiator radicals, R·, to the monomer; in the case of benzoyl peroxide, 43% of the radicals R· are phenyl and 57% are benzoyloxy under the reaction conditions used. (4) The average number of C14‐initiator fragments per polymer molecule, n, is 1.27, indicating that bimolecular termination of polymethyl methacrylate radicals is 57.5% by disproportionation and 42.5% by combination.
Comments on intrinsic viscosity–weight‐average molecular weight relationships for polyethylene
Authors: Chiang R. 
Published: April 2003

AbstractRelationships, as reported in the literature, between intrinsic viscosity and weight‐average molecular weight for high‐density polyethylene are in poor agreement. Experimental work in this laboratory, aimed at resolving similarly conflicting data, suggests that likely causes for these discrepancies are: polydispersity, incorrect dissymmetry correction, and inadequate solution clarification. These factors are discussed in some detail, and results on both fractionated and unfractionated samples support these conclusions. It is apparent that fairly narrow fractions must be studied to obtain a valid intrinsic viscosity‐weight‐average molecular weight relationship.
Swelling and elasticity of irradiated polydimethylsiloxanes
Authors: St. Pierre L. E. , Dewhurst H. A. , Bueche A. M. 
Published: April 2003

AbstractThe G value for crosslinking of polydimethylsiloxanes by high energy electrons has been redetermined using cryoscopc methods and checked by quantitative determinations of the amounts of gases evolved. The value found, G = 2.5 ± 0.4, is significantly different from that reported previously. The swelling of high polymers crosslinked by high energy electron has been measured using benzene and toluene. The x1 value calculated using equilibrium tension and swelling measurements are in good agreement with those obtained from the vapor pressure measurements of Newing. The equilibrium tension measurements indicate that 1 mole of crosslinks produces 1.3 ± 0.3 moles of effective chain between crosslinks in the Wall, Flory, Rehner scheme. This is in agreement with the predictions of Guth and James.
Molecular weights of sugar beet araban fractions
Authors: Tomimatsu Yoshio , Palmer K. J. , Goodban A. E. , Ward W. H. 
Published: April 2003

AbstractThe molecular weight of sugar beet araban fractions prepared by fractionation of the araban acetates on a charcoal column have been determined. Light‐scattering measurements using 2 M NaCl and aqueous 1% N,N‐dimethylformamide (DMF) as solvents gave, weight average molecular weights which did not agree, the values in the latter solvent being about half of those in the former. Other experimental observations, such as, number average and sedimentation‐viscosity molecular weights favor the results in salt solution; the low results in 1% DMF are presumably due to the interaction between araban and DMF. Arabans exhibited appreciable fluorescence when incident light of wavelength 436 mμ was used, but none at λ = 546 mμ. Sample limitations prevented measurements at the higher wavelength, and an alternate procedure for correcting for fluorescence is presented. The weight average molecular weights in 2 M NaCI which ranged from 18,400 to 37,000 for this study are appreciably higher than the previously reported value of 10,000. Number‐average molecular weights determined by the chlorous acid end‐group method ranged from 8700 to 24,200 for the various fractions. No simple relationship between molecular weight and fraction number was observed, and most of the fractions showed appreciable molecular weight heterogeneity.
Study of particles present in some high‐pressure polyethylenes
Authors: Moore Louis D. , Peck Virgil G. 
Published: April 2003

AbstractScattering of light by solutions of high‐pressure polyethylenes reveals that very large particles are present. These particles are not quantitatively removed by filters having a rated pore size of a fraction of a micron. If these particles are foreign material, aggregates of molecules, they probably should be removed before the solutions are studied in order to avoid an erroneous interpretation of the light‐scattering data. If, however, they are actually molecules of polyethylene, in most cases they should not be excluded from study because, in so doing, the results would not truly represent the sample. Experimental evidence is adduced to show that the particles are not foreign material, aggregates of molecules, or microgel. By appropriate techniques, very thin films of polyethylene can be cast from solution. By etching and shadowing these films, electron photomicrographs revealing the physical appearance of the particles may be obtained. Their shape, solubility, and behavior on pyrolysis strongly indicate that the particles are actually polyethylene molecules of very high molecular weight—perhaps 40,000,000. Such molecules might form an important part of the over‐all molecular‐weight distribution and, therefore, should not be excluded from studies of solutions by light scattering. Electron microscopy proved useful in offering visual confirmation that the particles present in the solutions used for light scattering are actually molecules. Also, it is quite probable that these photomicrographs show the largest polyethylene molecules which have ever been observed individually and reported.
Thermal degradation of polyethylene oxide and polypropylene oxide
Authors: Madorsicy S. L. , Straus S. 
Published: April 2003

AbstractPolyethylene oxide and atactic and isotactic polypropylene oxides were pyrolyzed in a vacuum in the temperature range 265 to 363°C. One phase of the investigation consisted in fractionating the products of degradation and analyzing the fractions qualitatively and quantitatively. Another phase consisted in measuring rates of degradation and calculating from these rates the activation energies. As compared with the corresponding non‐oxide polymers, polyethylene and polypropylene, the oxide polymers are less stable thermally, yield larger amounts of monomeric fragments, and have lower activation energies.
An x‐ray study of new cellulose complexes with diamines containing three, five, six, seven, and eight carbon atoms
Authors: Creely Joseph J. , Segal Leon , Loeb Leopold 
Published: April 2003

AbstractFive new diamine‐cellulose complexes have been prepared from cotton by means of tri‐, penta‐, hexa‐, hepta‐, and octamethylenediamines. The diamine contents of the dry fibrous materials have been determined, and the characteristic x‐ray diffractometer tracings have been obtained. Satisfactory x‐ray fiber patterns could not be obtained for the hydrazine, hepta‐, and octamethylenediamine complexes. The distention of the 101 interplanar spacing was found to be related linearly to the number of carbon atoms in the diamine molecule. Intensity of the diffraction also increased markedly with diamme chain length. Unit cell dimensions of the new complexes have been calculated. The x‐ray data indicating that the 101 interplanar spacing is occupied by only one diamine molecule is supported by the analytical data showing a diamine content close to that required by an anhydroglucose‐diamine ratio of 2:1.