bluuebunny/crossref_metadata_2025_split huggingface dataset:
Degradation and crosslinking in irradiated polyamides and the effect of oxygen diffusion
Authors: Zimmerman Joseph 
Published: April 2003

AbstractThe changes in relative viscosity which occur when nylon 66 is irradiated with 2 m.e.v. electrons under an oxygen‐free atmosphere under various conditions have been observed. A mechanism is proposed which reconciles all of these observations, and on the basis of this postulated mechanism yields of chain breaks and crosslinks are calculated. The effect of the presence of a small concentration of a vinyl monomer (acrylic acid) in the polymer during irradiation on degradation and crosslinking is also considered. The rate of penetration of oxygen into irradiated polyamides has been measured. There is a marked reduction in penetration rate which results from the presence of free radicals in the fiber and the irreversible reaction which results. The data are treated by an approximate diffusion equation and estimates of true diffusion coefficients are given. The effect of filament diameter on the extent of degradation which occurs when fibers of nylon 66 are irradiated and then exposed to air has been investigated. The marked dependence of degradation on fiber thickness is related qualitatively to the data on rate of oxygen penetration.
Local regularity of chain substances. III
Authors: Miyake Akira , Adachi Hatsuko 
Published: April 2003

AbstractThe statistics of polymer chain configuration is examined from the viewpoint of local regularity. The partition function of the chain composed of N linked bonds, internally rotating through the hindering potential, under the stretching force f is given, provided the bond length b and the bond angle γ are kept constant. The averages of the chain end separations R and the internal energy are calculated. When only three configurations, T (ϕ = π), G (ϕ = cos−1 c), and G′ (ϕ = −cos−1c), are possible for the internal rotation angle ϕ, we can have for the average numbers of T and G (including G′) bonds

and

where ε is the energy difference between G (or G′) and T; that of T or G parts is n = NTNG/N and those of bonds per T and per G part 〈t〉 = N/NG and 〈g〉 = N/NT, respectively. These results can be also deduced by the method of virtual boundary energy.
Temperature dependence of NMR absorption spectra of polyethylene
Authors: Peterlin Anton , Pirkmajer Edo 
Published: April 2003

AbstractA single‐crystal preparation from solution, polycrystalline Marlex crystallized from the melt, and five branched Du Pont polyethylenes were investigated by NMR from −170°C. to the melting point in order to study chain mobility and relaxation phenomena. Line width, line shape, and second moment measurement can be easily interpreted by chain mobility in lattice defects of the paracrystal which rapidly increase in number and extent with rising temperature and branching. Irreversible mobility changes were found in the single‐crystal preparation which, with increasing temperature, approaches that in Marlex crystallized from the melt.
The use of permselective membranes to determine the activity of the counterion in some polyelectrolyte solutions
Authors: Hardisty D. R. , Neale S. M. 
Published: April 2003

AbstractVarious cation‐selective membranes have been examined for sodium ion response in dilute solutions. The oxidized nitrocellulose membranes of Sollner have been used to determine cationic activities in solutions of Sky Blue FF, of cellulosic polyelectrolytes and of sodium polymethacrylate. The dyestuff behaves as a normal electrolyte of between 1:2 and 1:4 valence type, whereas the polyelectrolytes show the usual pronounced sequestering of the cation.
Polymerization with redox initiators. III. Complex formation between benzoyl peroxide and dimethylaniline
Authors: O'Driscoll K. F. , Richezza E. N. 
Published: April 2003

AbstractWhen a dilute solution of benzoyl peroxide is mixed with one of dimethylaniline, the resultant solution has an absorbance in the ultraviolet which is different from that which can be calculated assuming no interaction. The difference is temperature dependent and reversible. It is believed that the absorbance difference may be attributed to the rapid equilibrium formation of a complex between the amine and peroxide.
Polymerization of isobutene in homogeneous systems
Authors: Kennedy J. P. , Thomas R. M. 
Published: April 2003

AbstractThe homophase polymerization of isobutene in pentane solution with AlCl3 catalyst solutions has been studied at −78°C. The DP of isobutene increases with increasing amounts of pentane present. Below about 10% monomer content the polymerization is completely homogeneous. The reaction is extremely fast, and conversions and molecular weights do not change after the introduction of catalyst. Only when more catalyst is added can the reaction proceed to higher conversions. A linear relation exists between conversion and catalyst concentration. The dependence of DP or the conversion has been established. The differential DP's increase until a well defined maximum is reached at low conversions. At higher conversions the DP starts to decay sharply. A hypothetical termination mechanism has been proposed.
Sorption of water vapor by starch. Thermodynamics and structural changes for dextrin, amylose, and amylopectin
Authors: Volman D. H. , Simons J. W. , Seed J. R. , Sterling C. 
Published: April 2003

AbstractWater vapor sorption isotherms of a commercial dextrin prepared by dry acid treatment, amylose recrystallized from n‐butanol, and amylopectin precipitated from methanol were determined at various temperatures in the range of 10–40°C. The differential thermodynamic functions for water vapor sorption on the various materials were calculated, and B.E.T. constants were determined. A striking characteristic of the thermodynamic functions is the strong similarity for amylopectin and amylose. A model for the sorption is proposed. X‐ray patterns for the starch samples equilibrated with water vapor at various relative pressures of water vapor were determined. The major changes are explicable on the basis of intramicellar swelling. As the relative pressures increase, the crystalline patterns gradually fade and disappear. However, some new spacings appear with increased sorption in amylose and amylopectin. These spacings are explained on the basis of the formation of transitory lattices during the swelling of the starch crystallites.
The electrochemistry of vinyl polymer membranes
Authors: Kumins Charles A. , London Arnold 
Published: April 2003

AbstractThe electrochemical properties of polyvinyl acetate, polyvinyl chloride, and a copolymer of vinyl acetate and polyvinyl chloride have been studied. By means of membrane and bi‐ionic potential measurements, it has been shown that films made from these polymers are cation‐selective with a very low ion‐exchange capacity. The variation of membrane potential with external salt solution concentration occurs in a manner which may be predicted by the Meyer, Teorell, Sievers equations for permselective membranes. These have been used to calculate the fixed ion concentration within the polymers. The results suggest a possible mechanism for the passage of ions through mechanically perfect films.
Tracer techniques for the determination of monomer reactivity ratios. III. Ionization chamber assay and the reactivity ratios for the styrene/p‐methylstyrene copolymerization
Authors: Wiley Richard H. , Davis Burns 
Published: April 2003

AbstractMonomer reactivity ratios for the copolymerization of styrene (M1)with p‐methylstyrene (M2)using labeled styrene and an ionization chamber assay technique gave values of r1 = 0.83 and r2 = 0.96. These values are believed to be more reliable than those obtained by direct counting techniques (r1 = 0.99 and 0.94). There is a possibly significant difference between these values and those for this monomer pair in the aluminumtrialkyl–titanium chloride‐initiated copolymerization (r1 ∼ r2 ∼ 1.0), which requires further evaluation.
Heterophase polymerization of isobutene with aluminum chloride catalyst solutions
Authors: Kennedy J. P. , Thomas R. M. 
Published: April 2003

AbstractThe low temperature polymerization of isobutene with AlCl3 in methyl chloride solutions has been investigated. In a series of experiments the degree of polymerization of poly(isobutene)as a function of monomer concentration has been determined. It was found that increasing amounts of methyl chloride causes a marked increase in molecular weight until a sharp maximum is reached at about 0.10 mole fraction isobutene. Further dilution causes a precipitous drop in the molecular weights. It has been shown that increase in dielectric constant does not account for the rise in degree of polymerization. The log of degree of polymerization was found to be inversely proportional to the log of catalyst concentration between about 10−3–10−2 wt.‐% (7.53 × 10−5–10−4 mole liter−1)AlCl3 on monomer. At higher catalyst concentrations the degree of polymerization becomes concentration independent. This was true for methyl isobutene–chloride systems containing 1.0, 0.65, and 0.25 mole fraction of monomer. The product degree of polymerization times monomer concentration falls on the same curve.
On the mechanism of polymerization retardation by hydroquinone
Authors: Caldwell Robert G. , Ihrig Judson L. 
Published: April 2003

AbstractThe retardation of methyl methacrylate polymerization by hydroquinone, 1,4‐napthalenediol, and benzoquinone was studied by an accurate dilatometric method. The degree of retardation was found to be very small for the phenols in the absence of air and very sensitive to the presence of impurities. Kinetic analysis of the experimental results indicates that the intermediate radicals formed in the reaction between the chain radicals and the phenols disappear from solution principally by reinitiating polymerization. Comparison with results obtained for retardation by benzoquinone indicates that semiquinone radicals are probably not formed in the initial reaction of the phenols with the chain radicals. It is suggested that the intermediate radicals produced in phenolic retardation are addition complexes between the phenols and the chain radicals which may involve hydrogen bridging. The breakdown of these complexes then causes reinitiation of polymerization.
Reactivity ratios of vinyl 2‐chloroethyl ether in cationic copolymerization with vinyl alkyl ethers and para‐substituted α‐methylstyrenes
Authors: Dunphy J. F. , Marvel C. S. 
Published: April 2003

AbstractReactivity ratios have been determined for vinyl 2‐chloroethyl ether (M2) and vinyl isobutyl ether, vinyl octadecyl ether, α‐methylstyrene, p‐methyl‐α‐methylstyrene and p‐methoxy‐α‐methylstyrene in a stannic chloride‐initiated polymerization system.
Evidence for retention of the crystalline‐amorphous ratio of cellulose during heterogeneous acid hydrolysis
Authors: McKeown J. J. , Lyness W. I. 
Published: April 2003

AbstractThe literature reports that hydrolysis of cellulose under heterogeneous conditions proceeds by an initially rapid attack on the amorphous regions and then a much slower hydrolysis of the ordered regions or “crystallites.” During such hydrolysis, the degree of polymerization (D.P.) of cellulose initially decreases quite sharply and then levels off and declines at a much slower rate. This leveling off of the D.P. has been interpreted as being due to the slow hydrolysis of the “crystallites.” Some results obtained in our laboratories suggested that heterogeneous hydrolysis does not generate “crystallites” as has been assumed. Hence, a study of the crystallinity of the hydrolysis products was undertaken. The x‐ray crystallinity of cellulose was evaluated by comparing the integrated intensities of the main diffraction peaks before and after hydrolysis. The effects of variations in sample preparation and orientation of cellulose samples as well as fluctuations in the operation of the diffractometer were assessed and were found to introduce no artifacts. The x‐ray crystallinity of slash pine sulfate pulp did not increase upon hydrolysis as would be expected if hydrolysis had liberated “crystallites.” Cotton linters and slash pine sulfite pump exhibited only small increases in crystallinity upon hydrolysis. A decrease in x‐ray crystallinity was observed for gum sulfate pulp which cannot be explained at this time. Thus it appears that hydrolysis does not convert cellulose to a wholly crystalline or ordered state. It might be well to review past work in which complete crystallinity of cellulose “crystallites” has been assumed.
Aqueous solutions of salts of poly(vinylsulfonic acid)
Authors: Eisenberg Henryk , Casassa Edward F. 
Published: April 2003

AbstractSpecific ion effects in solutions of salts of poly(vinyl sulfonic acid) in aqueous univalent supporting electrolyte are described in regard to observations of phase separation, dialysis equilibrium, light scattering, viscosity, and sedimentation. The most complete data have been obtained on two systems, ammonium poly(vinyl sulfonate) in 0.5M NH4Cl and potassium poly(vinyl sulfonate) in 0.5M KCl. Although the distribution of small ions across a semipermeable membrane is not markedly different in the two cases, other thermodynamic properties, the occurrence of phase separation in the KCl solution and its absence with NH4Cl, together with a larger second virial coefficient in the latter case, indicate that NH4Cl is a much better solvent for the corresponding polymer than is KCl. The hydrodynamic measurements concur in showing that the polymer chain configuration is more expanded in the NH4Cl solution. The interrelations among thermodynamic and hydrodynamic properties developed and generally substantiated for solutions of unionized polymers are found to be valid, at least qualitatively, for both these systems. This study also illustrates how the thermodynamic formalism for a two‐component system is applicable to three components, two diffusible and one non‐diffusible, provided solutions are equilibrated by dialysis against the solvent mixture.
Reaction of ferric chloride with benzene
Authors: Kovacic Peter , Wu Chisung 
Published: April 2003

AbstractBlack, insoluble organic material was obtained, together with chlorobenzene in low yield, from the reaction of benzene with ferric chloride. Small amounts of Brönsted acids, such as water, hydrogen sulfide, acetic acid, and nitroethane, markedly promoted the formation of black solid. The principal product, whose properties were investigated, is believed to be formed by a cationic polymerization of benzene, leading to chlorinated polynuclear hydrocarbons. In contrast, under similar conditions aluminum chloride yielded a high‐boiling oil, but no black solid.
Osmotic pressure and dimensions in moderately concentrated polymer solutions
Authors: Fixman Marshall 
Published: April 2003

AbstractConcluding calculations are reported for a recent theory of the concentration dependence of polymer dimensions. In a prior theory of the osmotic pressure, the polymer size appeared as a parameter. It is here shown that a better agreement of the osmotic pressure theory with experiment is obtained if the polymer size is allowed to depend on concentration in such a way as to minimize the free energy of solution, than if the polymer size is taken independent of concentration. A brief résumé and critique of the model is given.
On the characterization of stereoregular polymers. II. Polypropylene
Authors: Newman S. 
Published: April 2003

AbstractIn this study, a survey has been made of the applicability to the crystallization of partially tactic polypropylene of Flory's theoretical relations concerning crystallization in copolymers. To this end, the crystallinity and modulus of several fractions of polypropylene of varying tacticity were measured and compared with theoretical calculations.
A theory of the thermodynamic behavior of nonelectrolyte solutions. V. The scattering of light by polymer solutions
Authors: Maron Samuel H. , Nakajima Nobuyuki 
Published: April 2003

AbstractMaron's theory of the thermodynamics of non‐electrolyte solutions has been used to examine the light scattering behavior of both dilute and concentrated solutions of polystyrene in several solvents. It is shown that for each polymer‐solvent system at a given temperature the behavior can be characterized, as in the case of osmotic pressure, by a single interaction parameter μ which varies linearly with volume fraction v2, i.e. μ=μ°+σ°v2, where μ° and σ° are constants. Introduction of this equation into Maron's theory leads to functional plots in dilute solutions which are linear even when the conventional plots of HC/τ versus C plots are not. These plots yield the molecular weight from the intercepts and (μ° − σ°) from the slopes. However, to obtain the individual values of μ° and σ° data are required for concentrations higher than those normally used for molecular weight determinations. It is further shown that once μ° and σ° are evaluated, they may be used to calculate satisfactorily the turbidities up to a concentration of v2 = 0.62. Under the same circumstances the Flory‐Huggins interaction parameter χ does not reproduce the observed data as well even when χ is taken to be a linear function of v2.
“Steric” stabilization of colloidal solutions by adsorption of flexible macromolecules
Authors: Heller Wilfried , Pugh Thomas L. 
Published: April 2003

AbstractIt had previously been found in this laboratory that flexible polymer molecules adsorbed at colloidal particles most likely extend with many segments into the interior of the surrounding medium. This led one to expect a possible “steric protection” of colloidal particles by adsorption of flexible polymers of sufficiently high molecular weight since the merely slight interpenetration of polymer chains protruding from two colliding particles should keep them at distances too large to give a van der Waals interaction energy sufficient for coherence. This new type of stabilization was now proved using gold hydrosols as test systems and polyethylene glycols as adsorptives. The stabilization was found to increase with polymer concentration and, particularly, with the molecular weight of the polymer. In analogy with the previous finding, that the adsorption equilibrium is being approached very slowly if the molecular weight of the polymer exceeds several thousand, it was found that the degree of stabilization achieved by addition of polymer to the gold sols increases with the time elapsed before the subsequent addition of coagulating electrolyte. This increase is particularly strong during the first hour following addition of the polymer. The potential significance of the results for stabilization of organosols is discussed.
Coagulation and stabilization of colloidal solutions with polyelectrolytes
Authors: Pugh Thomas L. , Heller Wilfried 
Published: April 2003

AbstractPolyelectrolytes are found to be powerful coagulating agents for colloidal solutions at concentrations as low as 10—8 moles/l., and excellent stabilizing agents at somewhat higher concentrations (in excess of 10—6 moles/l.). This applies if the polyions have a charge opposite to that of the colloidal particles. If polyions and colloidal particles have like charges, the stability of the colloidal solutions is only slightly altered, primarily in the direction of sensitization. The investigations were carried out with FeOOH sols (positively charged particles), gold sols (negatively charged particles), sodium polystyrene sulfonate and polyvinylbenzyltrimethylammonium chloride. The stability was tested by means of a modified gold number (Au sols) or by considering the rate of coagulum formation (FeOOH sols). The stabilizing effect is interpreted as being both electrostatic and steric.
Ultrasonic degradation of polystyrene. Part III. The molecular weight distributions of degraded fractions
Authors: Gooberman G. 
Published: April 2003

AbstractA method is given for calculating the molecular weight distributions of ultrasonically degraded polystyrene. This method is based on the assumption that the bond which is most likely to break is situated in a plane passing through the center of the polymer molecule and which is normal to the propagation direction of the shock wave from a collapsed cavity. The theoretical distribution has been calculated for a polystyrene fraction of average molecular weight of 4.8 × 105 dissolved in benzene after 2 hr. irradiation. The undegraded fraction is assumed to possess a rectangular differential number distribution. The theoretical distribution is peakier than that found experimentally by turbidimetric titration. The difference may be due to the lack of resolving power shown by turbidimetric titration.
Dynamic mechanical properties of polymerized epoxy resins
Authors: Kline Donald E. 
Published: April 2003

AbstractThe dynamic mechanical properties of polymerized epoxy resins have been studied over the 80—600°K. temperature region using an appratus which drives rodlike specimens in a transverse mode. Experimental results for the mechanical loss indicate several dispersion peaks throughout the temperature range. The dynamic modulus is found to be monotonically decreasing everywhere except near the 480—550°K. range. Effects of cure time, filler, and low dose irradiations are included in the investigation.
Chromatographic fractionation of polyethylene
Authors: Guillet J. E. , Combs R. L. , Slonaker D. F. , Coover H. W. 
Published: April 2003

AbstractA new method has been developed for the fractionation of polyethylene, providing more reliable data on molecular weight distribution in a fraction of the time required by previous methods. The fractionation is carried out on a column of glass beads, using a combination of solvent and temperature gradients by a method similar to that used by Baker and Williams for polystyrene. The lowest temperature in the column is above the melting point of the polyethylene, so that fractionation takes place by partition of the polymer molecules between two liquid phases in transient equilibrium. Because of the combined solvent and temperature gradients, the polymer is transferred from the stationary to the moving phase many times in its passage down the column; consequently, the fractions are considerably narrower than those obtained from a single‐step fractionation. A simple apparatus which will fractionate up to 5 g. of polyethylene in a 24‐hr. period is described. The effect of such experimental variables as column load, solvent flow rate, and the type of solvent gradient was determined. Experimental data obtained on several commercial polyethylenes are given.
A vorticity effect in anisotropic fluids
Authors: Ericksen J. L. 
Published: April 2003

AbstractWe analyze equations describing the motion of a preferred direction in an anisotropic fluid undergoing plane, steady homogeneous flow. These equations are essentially the same as those deduced by Jeffery for the motion of a rigid ellipsoid of revolution suspended in a Newtonian fluid. When the ratio of vorticity to rate of strain is sufficiently small, we find that the flow produces a high degree of orientation. This can be destroyed or at least diminished by making the ratio sufficiently large. We suggest conditions under which this hydrodynamic orientation effect might give rise to elasticity phenomena in polymer solutions.
The synthesis of polythiolcarbamates
Authors: Dyer Elizabeth , Osborne D. Wendell 
Published: April 2003

AbstractA series of polythiolcarbamates, [—CONH—X—NHCOS—Y—S]m, have been prepared in which X was either aliphatic or aromatic and Y was a wide variety of aliphatic groups. Synthesis of the polymers by two different methods, the tertiary aminecatalyzed solution polymerization of diisocyanates with dimercaptans and the interfacial polycondensation of bischlorothiolformates and diamines, proved that the polymers had the desired thiolcarbamate structure. Greater yields of lower molecular weight polymers were obtained by the diisocyanate method. Polythiolcarbamates were found to be highly insoluble white powders which tend to decompose in light, in hot solvents, and in aqueous base. They melt somewhat higher than their oxygen analogues, but are less thermally stable.