bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle size distribution in brominated Hevea latices
Authors: Schoon Th. G. F. , van der Bie G. J. 
Published: April 2003

AbstractFrom electron micrographs of clonal latices and centrifuge fractions, the particle size distributions in Hevea brasiliensis latices have been measured. By means of this investigation–which was meant to be informative only–it has been possible to ascertain that the highly asymmetric size frequency distributions that are apparently present result from the existence of several size fractions, which each itself has a normal Gaussian distribution. The particle sizes are found as being multiples of whole numbers of either of the two particle sizes 58 mμ and 69 mμ. A possible explanation of this phenomenon is that the larger particles form by clustering of the smaller particles in a grape‐like arrangement, without actual coalescence or fusing together. From the experiments it may be supposed that the particle size distribution of latex may have an influence on its centrifuging qualities.
Formation and properties of polymer carbon
Authors: Winslow F. H. , Baker W. O. , Pape N. R. , Matreyek W. 
Published: April 2003

AbstractDivinylbenzene (48%)/ethylvinylbenzene copolymer was converted to a series of pyrolytic derivatives. Enough of the carbon bond network remained intact throughout thermal rearrangement and condensation to retain the original gross shape of the copolymer in the final polymer carbon. Although a carbon residue (6% by weight) was obtained by direct heating of the copolymer, yields were increased eightfold by preoxidation or prechlorination. Such an alteration of thermal degradation is obviously a complex process involving both “inhibition,” in the ordinary sense, and a considerable contribution toward an increased valence network density. As a consequence, the average molecular weight of volatile fragments evolved during carbonization is inversely proportional to the oxygen content of the original hydrocarbon polymer. Pyrolysis of divinylbenzene copolymer, containing 18% oxygen, resulted in a 50% volume shrinkage, 50% weight loss, and a 100% density gain. Unless these data are attributable to extensive microporosity, it is difficult to account for the sorption of up to 3 cc. of helium gas per gram of polymer carbon at 30°C. and 600 mm. pressure; and calculated surface areas as large as 1400 sq.m./g. Abrupt changes in the progress of polymer carbon formation occurred between 600 and 700°C. The residue became rigid; vigorous evolution of volatile products, principally hydrogen, suddenly diminished; and paramagnetic resonance absorption (unpaired electron concentration) dropped about tenfold while d.c. resistivity decreased 106 ohm cm. In this region, also, x‐ray patterns were most diffuse, exhibiting no maxima characteristic of carbon scattering in either hydrocarbons or condensed rings. Finally, the x‐ray patterns of polymer carbon intermediates became less diffuse in samples prepared at 700°C. or above. Yet, scattering indicated the presence of crosslinked graphitic layers of such stability that reordering or true graphitization did not occur at 2400°C.
Reinforcing effect of condensation polymers on rubber in connection with their particle size
Authors: Houwink R. , Van Alphen J. 
Published: April 2003

AbstractEvidence is brought forward that the noticeable reinforcing effect by cyclized rubber, if added as a filler to natural rubber, is bound to a certain minimum particle size of the cyclized rubber. It is further shown that the reinforcing effect of some condensation polymers is enhanced if chemical bonds with the rubber are formed. The reinforcing effect by resins is connected with their hardness.
Determination of the shape of gamma‐globulin by means of the x‐ray low‐angle method
Authors: Kratky O. , Porod G. , Sekora A. , Paletta B. 
Published: April 2003

AbstractA short review is given of the development of the theory and of the new experimental technique of x‐ray low‐angle scattering. The study of human γ‐globulin leads to a cylindrical particle of about elliptical cross section with axes of 19 and 57 A. and with a length of 230–240 A. The volume is found to be 1.98 × 105 A.3, which involves a molecular weight of 1.62 × 105 in satisfactory agreement with the value found by ultracentrifuge measurements.
The viscosity slope constant k′—ternary systems: Polymer–polymer–solvent
Authors: Cragg L. H. , Bigelow C. C. 
Published: April 2003

AbstractThe viscosity slope constant k′, i.e., \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\lim }\limits_{c \to 0} \frac{{d\left( {{{\eta _{sp} } \mathord{\left/ {\vphantom {{\eta _{sp} } c}} \right. \kern-\nulldelimiterspace} c}} \right)}}{{dc}}\frac{1}{{[\eta ]^2 }} $\end{document}, is shown to be of increasing significance in polymer science as a molecular‐weight‐independent criterion of solvent power and as a parameter sensitive to various changes in polymer structure, such as long‐chain branching. Ideally, it is a dimensionless parameter, independent of molecular size, which arises only from the mutual hydrodynamic interaction of polymer molecules and depends, therefore, on the intrinsic flexibility of the polymer chain and on the polymer density in the coiled molecule. In real systems, however, other interactions may contribute, sometimes very significantly, to k′. For such real systems, the general expression:

is suggested. In ternary systems, polymer–polymer–solvent, ideal expressions for ηsp/c and k′ are developed, that for k′ being:

It is proposed that deviations from ideal behavior so defined are due to nonhydrodynamic polymer‐polymer interactions and might be used to detect and measure the strength of such interactions. Some preliminary data for the system polystyrene–poly(methyl methacrylate)–m‐xylene are presented and discussed.
Acid acceleration of epoxide condensations
Authors: Dearborn Elizabeth C. , Fuoss Raymond M. , White Alice F. 
Published: April 2003

AbstractThe addition of carboxylic acid to Epon 834‐phthalic anhydride resins accelerates the rate of cure. The maximum thermal yield point corresponds to reaction of all the epoxide groups in the ratio of two anhydride carbonyls to one epoxide oxygen or of one acid carbonyl to one epoxide oxygen. The initial presence of some secondary alcohol groups appears to be essential for initiation of reaction as suggested by Fisch and Hofmann. Carboxylic acids react directly with epoxide groups to produce secondary alcohols which in turn react with phthalic anhydride, regenerating carboxylic acid groups. Succinic acid gives a rapid cure (although not as fast as amines) to a resin with only slightly lowered thermal yield point, while benzoic acid depresses the yield point by about 15° because it acts as a chain‐stopper.
Mechanochemistry and ion exchange
Authors: Katchalsky A. , Zwick M. 
Published: April 2003

AbstractThe swelling behavior of crosslinked gels of polymethacrylic acid, partially or wholly neutralized by mixtures of sodium and barium hydroxide, is described. At high degrees of neutralization and high barium content there is a contractile region of rapid transition from a swollen to an unswollen state. A new type of contractile polyacid fiber made of Krilium and polyvinyl alcohol was developed. The force–elongation curves are given for these fibers at different degrees of neutralization with sodium and barium hydroxide in solutions containing sodium and barium chloride of various ionic strength. The dimensional changes caused by ion exchange can be utilized in a mechanochemical engine. An irreversible work cycle for such an engine is described in which the energy of mixing of mono‐ and divalent ions on polyelectrolyte fibers is partially converted into mechanical work.
Dye binding to high polymers
Authors: Oster Gerald 
Published: April 2003

AbstractA number of examples are presented to show that cationic dyes bind to polymeric acids by simple electrostatic forces. Competitive binding for the substrate is illustrated by the addition of hydrogen ions, calcium ions, and streptomycin. Anionic binding to uncharged or to negatively charged substrates is attributed to hydrogen bonding with the carbonyl groups of the substrate. Van der Waals' forces also play an important role in the binding. Illustrations are given for the substrates, native serum albumin, denatured ovalbumin, polyvinylpyrrolidone, and water‐soluble urea‐formaldehyde resin. In the last‐named case the binding increases with increasing molecular weight of the substrate. A new fluorometric technique for following the binding of anions is described. The changes in spectral and photochemical properties which dyes undergo when bound are summarized.
Statistical thermodynamics of polyelectrolyte solutions. I. Activity coefficient of counter ion in salt‐free system
Authors: Kagawa Ikumi , Nagasawa Mitsuru 
Published: April 2003

AbstractThe authors investigated theoretically the activity coefficient of counter ion in the salt‐free polyelectrolyte solutions, by stressing the interionic interaction between the macro ion and counter ion. Assuming the Boltzmann distribution for the polyelectrolyte system and proposing a new linear approximation, the Poisson‐Boltzmann equation was solved for a model of spherical rigid macro ion, and then the free energy of the system was calculated by means of the charging‐up procedure. Applying this theory to the experimental data of activity coefficient of silver ion in the silver carboxymethyl cellulose solutions, the size of macro ion was computed, and the results are discussed from a purely theoretical standpoint. Thus, the authors have succeeded in giving a valid insight into the correlation between polyelectrolyte and simple electrolyte solutions as well as into some peculiar features of polyelectrolyte solutions.
Reactions of methyl radicals and their applications to polymer chemistry
Authors: Szwarc M. 
Published: April 2003

AbstractAn experimental method has been developed for determining the relative reactivities of various aromatic and olefinic compounds toward methyl radicals. The reaction in question may be represented by the equation CH3 + A → CH3. A, where A denotes an aromatic or olefinic molecule. By these means the reactivities of various vinyl monomers, inhibitors (such as quinones, nitro compounds, etc.), and aromatic hydrocarbons were determined on the same relative scale. The method can be utilized also for deriving the relative chain transfer data (for methyl radicals). A relationship between reactivity and singlet‐triple excitation energy has been demonstrated and explained in terms of energy diagram. The problem of efficiency of initiators is discussed in some details.
The polymerization of sulfur
Authors: Fairbrother Fred , Gee Geoffrey , Merrall G. T. 
Published: April 2003

AbstractA previous analysis of the polymerization of liquid sulfur has been revised to take account of specific heat data now available and some new experimental evidence presented here. It is confirmed that liquid sulfur is essentially an equilibrium mixture of S8 rings and long free radical chains. The heat of polymerization (S8 → inifinite chain) is estimated as 3180 cal./mole of S8 at 432°K., where polymerization sets in rather abruptly; the corresponding entropy of polymerization is +7.4 cal. mole−1 deg.−1. There is evidence for the presence of rings of more than 8 atoms; the concentration of these reaches a maximum of ca. 1% in the neighborhood of the critical polymerization temperature (432°K.). Magnetic susceptibility measurements place an upper limit of 2 × 10−2 moles l.−1 on the free radical concentration. From this and other lines of evidence it is concluded that the heat of scission of sulfur chains does not exceed 35 kcal., and an explanation is put forward.
Contribution à la cinétique de polymérisation dans les milieux précipitants
Authors: Magat Michel 
Published: April 2003

AbstractUne tentative est faite d'utiliser pour la description de la polymérisation en milieu précipitant le schéma cinétique habituel (amorçage, propagation, terminaison mutuelle), mais en admettant que l'état quasi‐stationnaire n'est pas atteint au début de la réaction. Le système d'équations différentielles pu être résolu pour certains cas: concentration constante de catalyseur, concentration décroissante selon une loi cinétique de premier ordre, etc…. Une méthode d'approximation est proposée pour traiter les cas où il y a accumulation du catalyseur dans la phase monomère par suite de son insolubilité dans le polymère. Les formules obtenues permettent de rendre compte de la polymérisation en masse du chlorure de vinyle, à différentes températures et à différentes concentrations du catalyseur (peroxyde de benzoyle), et ceci aussi bien pour des expériences à faibles degrés de conversion que pour des expériences poussées à des degrés de conversion élevés. Les constantes kp/kt et (kaA0kt)−1/2, déterminées à différenctes températures correspondent à des énergies d'activation E − E = 5,2 kcal., E + E = 29,6 kcal. Cette dernière valeur indique que l'énergie d'activation de terminaison n'est pas très élevée et que le ralentissement de terminaison observé est dû à une diminution du facteur de fréquence. Les mêmes formules ont été utilisées pour le cas de polymérisation du chlorure de vinylidène. Dans ce cas il a été possible de calculer les valeurs absolues des constantes de vitesse de terminaison et de propagation qui sont très sensiblement plus faibles que dans le cas de polymérisation en milieu homogène. Certaines difficultés persistent, qui amènent à penser que la théorie n'est pas complète.
Turbidimetric titration of block polymer solutions
Authors: Melville H. W. , Stead B. D. 
Published: April 2003

AbstractThe turbidimetric titration method, used previously to determine molecular weight distributions in polymers, has been used for the qualitative examination of various polymers: mixtures containing block copolymer (styrene‐methyl methacrylate or vinyl acetate‐methyl methacrylate), polystyrenes prepared in branching studies, and commercially prepared polystyrenes. The method is a sensitive and rapid one and is suitable for the examination of very small quantities of polymer. A semiautomatic titration apparatus is also described.
Copolymers in dilute solution. I. Preliminary results for styrene‐methyl methacrylate
Authors: Stockmayer W. H. , Moore L. D. , Fixman M. , Epstein B. N. 
Published: April 2003

AbstractThe dilute solution properties of copolymers are briefly discussed in relation to those of the parent homopolymers. It is shown that copolymer molecules are usually more expanded in solution than would be expected from the averaged behavior of the pure polymers, because of repulsive interactions between the unlike monomer units. A thermodynamic parameter χAB characterizing these interactions can be derived from measurements of the dilute solution properties of copolymers. In favorable cases this parameter can be independently evaluated from studies of ternary systems composed of the two parent homopolymers and a solvent, thus allowing prediction of the behavior of the copolymer. Light scattering and viscosity measurements on fractions of approximately equimolal copolymers of styrene and methyl methacrylate are presented and analyzed. The values of χAB deduced from the results in two solvents agree satisfactorily with each other, but are somewhat larger than those earlier obtained from measurements on ternary systems.
Die ubertragungskonstante von polymethylmethacrylat bei der polymerisation von methylmethacrylat und styrol
Authors: Schulz G. V. , Henrici G. , Olivé S. 
Published: April 2003

AbstractDie Übertragungskonstante von Polymethylmethacrylat hei der Polymerisation von Methylmethacrylat hzw. Styrol wird dadurch bestimmt, dass man Polymeres von sehr kleiner Kettenlänge dem polymerisierenden Stoff zusetzt. Das zugesetzte α‐Polymere beeinflusst nicht die Bruttogeschwindigkeit, setzt aber den Polymerisationsgrad des entstehenden Polymeren herab. Für diesen Vorgang gelten dieselben Gleichungen wie für niedermolekulare Regler. Die Übertragungskonstante von Polymethacrylat setzt sich aus zwei Anteilen zusammen, welche den Mittelgruppen und einer Endgruppe entsprechen. Die wirksame Endgruppe ist hei der Disproportionierung entstanden. Polystyrol zeigt keinen Endgruppeneffekt, da das Kettenwachstum durch Kombination beendet wird. Aus den gemessenen Übertragungskonstanten kann der Grad der Verzweigung bei Polymethacrylaten und Polystyrolen abgeschätzt werden.
The extension of polystyrene chains: Dependence on molecular weight and solvent
Authors: Notley N. T. , Debye P. J. W. 
Published: April 2003

AbstractThe relation between molecular size and weight for polystyrene in cyclohexane at 34, 43, and 57°C. and toluene at 20°C. has been determined by a light scattering method. For the molecular weight range, half‐million to five million, the data suggest a linear relationship:L2 = κ (M − b)
where κ and b are parameters which have their higher values in better solvents.
The crystal structure of polycaproamide: Nylon 6
Authors: Holmes D. R. , Bunn C. W. , Smith D. J. 
Published: April 2003

AbstractThe crystal structure of nylon 6 (NH (CH2)5CO)p has been determined by interpretation of the x‐ray diffraction patterns given by drawn, rolled fibers. The determination was part of a program to investigate the relation between structure and physical properties, in particular melting point. Nylon 6 melts 50°C. lower than its isomer nylon 66 (NH (CH2)6NH·CO (CH2)4CO)p; it had been suggested that this was due to deficient hydrogen‐bond formation in nylon 6 crystallites. The unit cell contains eight chemical units (NH (CH2)5CO) and is monoclinic with a = 9.56 A., b = 17.24 A., c = 8.01 A., and β = 671/2°. Calculated density = 1.23. Observed density for a drawn monofilament = 1.16. The structure consists of planar chains of CH2 groups and amide groups tilted 7° from the (001) plane. Alternate chains in this plane are oppositely directed, an arrangement which allows all hydrogen bonds to be made perfectly. The hydrogen‐bonded sheets of atoms are packed in an “up‐and‐down” staggered configuration along the c‐axis. Distances between atoms in neighboring molecules are all normal van der Waals contact distances. It appears, from a general survey of polyamide melting points published elsewhere, that the determining factor is the number of CH2 groups between the amide “anchor points”—polymers with odd numbers of CH2 groups melt lower than those with even numbers. The present work shows that the odd number of CH2 groups in this polymer does not lead to deficient hydrogenbond formation, and that the lower melting point of nylon 6 as compared with nylon 66 must be ascribed to some other cause, possibly connected with the propagation of vibrations along odd‐numbered chain segments.
Determination of the tensile strength of gels
Authors: Ben‐Arie Michael M. 
Published: April 2003

AbstractA method has been devised and an apparatus constructed for measuring the tensile strength of viscoelastic gels. The method consists of extruding the gel vertically through a nozzle of diameter of 2–14 mm. and weighing the gel‐column falling by its own weight. The weight of the column divided by the area of the nozzle gives the value of the tensile strength. The latter lies for Napalm gels of 2–6% Napalm in gasoline within the limits of 1.5–8 g./cm.2. The so determined tensile strength depends on the extrusion velocity, but is independent of the area and other dimensions of the nozzle; it is also independent of the driving pressure. The functional dependence of the tensile strength on the extrusion velocity and the form of this function have been established by a numerical approximation. The tensile strength of viscoelastic fluids has been shown to depend on the viscosity coefficient and on Young's modulus. It follows that thixotropy and work‐hardening are interrelated phenomena.
Dielectric constant–strain coefficient of polystyrene and lucite at 3.2 centimeters
Authors: Horton C. W. , Rogers R. G. 
Published: April 2003

AbstractTwo experimental procedures have been used to measure the effect of elastic strains on the dielectric constants of polystyrene and Lucite. In the first experiment the dielectric sample was placed in a section of a standard X‐band wave guide. Stresses were applied parallel and perpendicular to the electric field. In the second experiment the dielectric sample was placed in a resonant cavity. The cavity was excited in the TE011 mode and the applied stress was perpendicular to the electric vector. The data are presented in terms of a so‐called dielectric constant‐strain coefficient, β, which is defined as the ratio of the fractional change in the dielectric constant to the compressional strain of the sample. When these values are converted to the customary stress‐“optical” coefficients, one obtains C = 6 × 10−12 cm.2/dyne for polystyrene and Lucite.
A graphic method for single‐point determination of intrinsic viscosity
Authors: Hart Victor E. 
Published: April 2003

AbstractFor a given polymer‐good‐solvent system at a fixed temperature, the product of intrinsic viscosity and concentration is a unique function of specific viscosity alone up to high values of specific viscosity. This permits a single parametric curve to be drawn from experimental data; thereafter, accurate calculation of intrinsic viscosity from the results of a single specific viscosity measurement becomes possible with the aid of a convenient equation.
Bis‐type modifiers in polymerization. I. Behavior of various disulfides in bulk styrene polymerization
Authors: Pierson R. M. , Costanza A. J. , Weinstein A. H. 
Published: April 2003

AbstractModifiers with bis‐type structures are of interest as a means for conferring reactive groups onto the highest possible fraction of polymer chain ends. Various disulfides and other bis‐type compounds—some with reactive groups attached—were compared as to their effectiveness as modifiers in low conversion bulk styrene polymerizations and studies made of their mechanism of cleavage. Alkyl disulfides of primary thiols had transfer constants too low to be of much interest for this work, even when substituted at carbons near the sulfur‐sulfur bond. Aryl disulfides proved to have much higher transfer constants, and substitution on each ring with appropriate groups offered a means both of increasing the transfer constant and of incorporating desired groups.It has been shown quite conclusively that aryl disulfides cleave so as to confer one‐half the molecules onto each end of the polymer. This was demonstrated by analyzing the end group concentrations of styrene polymers of wide molecular weight range which contained various types of end groups—carboxyl, amino, naphthyl, and benzothiazyl—and comparing, wherever possible, with polymers modified with thiols containing similar groups.Polymerizations carried out at 25, 50, and 75°C. with certain of the bis‐type compounds and with a normal and a tertiary mercaptan showed that activation energies are very slight if the transfer constant is high, and begin to reach significant levels only at low levels of transfer constant.
Structural analysis of novolacs
Authors: Boelhouwer C. , Waterman H. I. , Wijnands P. H. W. 
Published: April 2003

AbstractThe structure of certain novolacs, prepared by polycondensation of formaldehyde with phenol, p‐cresol, and m‐cresol respectively, was investigated. The novolacs were transformed into saturated hydrocarbons, thus expelling the oxygen, by a relatively mild high pressure hydrogenation (300°C., 250 atm.) using 100% by weight of a nickelcopper on kieselguhr catalyst. It can be expected that this treatment does not alter the structural frame of the molecules. From ultimate analysis and physical constants of the hydrocarbons, conclusions were made as to the structure of the novolacs. They are linear thermoplasts; no “extra” rings are present.