bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applied force and second order transitions of rubber
Authors: Wall F. T. , Miller Donald G. 
Published: April 2003

AbstractThe second order transition temperatures of three different cures of natural rubber have been studied as functions of elongation by observing length dependence on temperature. This transition temperature (Tm) decreases with increasing applied force, and at any given force increases with increased crosslinking; moreover the slopes of the Tm vs. force curves become less steep with increased crosslinking. The results are in agreement with the following propositions: (1) that transitions are caused by the onset of rotations; (2) that extension of the polymer makes the onset of such rotations easier, thus lowering Tm; (3) that increased crosslinking hinders rotation so as to increase Tm; and (4) that increased crosslinking diminishes the effect of a given force on Tm. The hypothesis of rotation is also discussed in connection with the effect of swelling agents on the second order transition.
An X‐ray study of the decomposition product of the ethylamine‐cellulose complex
Authors: Segal Leon , Loeb Leopold , Creely Joseph J. 
Published: April 2003

AbstractThe present paper reports the results of a study of the decomposition product of the ethylamine‐cellulose complex obtained from cotton cellulose. It is shown that the cotton remaining after removal of ethylamine by distillation possesses a crystalline component identical with the ammonia‐cellulose decomposition product designated by other workers as cellulose III. Certain important differences between ramie cellulose III and cotton cellulose III are discussed especially as regards the relative ease of recoversion to cellulose I. Experimental data are given showing the effect on degree of conversion of temperature, and of two different times of immersion in boiling water. Data are also given showing the effect on the structure of the decomposition product of time of immersion in ethylamine. An attempt is made to explain the appearance of a strong diatropic 020 interference in the x‐ray patterns of the decomposition product and of the regenerated cotton cellulose I.
The microstructure of diene polymers. I. Polyisoprenes and polybutadienes prepared at high temperatures
Authors: Richardson W. S. 
Published: April 2003

AbstractPolybutadienes and polyisoprenes prepared by bulk thermal polymerization at temperatures between 100 and 250°C. have been analyzed for the percentages of the various types of addition present. It is found that polybutadiene tends toward a mixture of about 40% each of cis‐1,4‐ and trans‐1,4‐ and 20% 1,2‐addition as the polymerization temperature is increased. Polyisoprenes show a decrease of 1,2‐addition and cis‐1,4‐addition and a corresponding increase in trans‐1,4‐ and 3,4‐addition at preparation temperatures above about 100°C. Differences in energy and entropy of activation for the formation of the various structures in polybutadiene are given.
The structure of neoprene. VI. Crystallization
Authors: Maynard J. T. , Mochel W. E. 
Published: April 2003

AbstractA volume dialometric study of the crystallization behavior of polychloroprenes made at −40°, 10°, and 40°C. has shown that the melting point of the crystalline phase in these polymers is an inverse linear function of polymerization temperature. Polychloroprene made at −40°C. melts at ca. 65°C., while conventional 40°C. neoprenes melt at ca. 40°C. Comparison of this data with the melting point depression observed in a chloroprene/methacrylonitrile copolymer and in polychloroprene/diluent mixtures has made possible calculations which confirm earlier hypotheses that neoprenes have a highly regular structure. Commercial neoprenes made at 40°C. are calculated to consist of 80–85% of the trans‐2‐chloro‐2‐butylene units which result from trans‐1,4 polymerization of chloroprene. Densities determined for crystalline and amorphous neoprenes have been used to calculate the degree of crystallinity of these polymers, and this information has made possible calibration of the infrared crystallization‐sensitive bands, for use in measurement of degree of crystallinity. The heat of fusion of the crystalline phase of neoprenes has been found from diluent data to be 22.7 ± 2 calories per gram.
The structure of neoprene. VII. Infrared analysis of configuration
Authors: Maynard J. T. , Mochel W. E. 
Published: April 2003

AbstractA study of the infrared absorption spectra of polychloroprenes made at temperatures ranging from −40 to 100°C. has made possible identification and estimation of the major structural features of these polymers. It is confirmed that 1,4 polymerization of chloroprene accounts for the greatest part of the structure of all neoprenes, ranging from 99% in −40°C. polymers to ca. 84% in 100°C. polychloroprenes. Of this 1,4 polymer only a small fraction has the cis configuration. This proportion increases from less than 5% in −40°C. polymer to ca. 13% in 100°C. polymer. Small amounts of branched structures that result from 1,2 and 3,4 polymerization are observed. These also increase in concentration with higher polymerization temperatures but do not account for more than 2.5% each even in 100°C. polychloroprenes. The portion of these polymers unaccounted for by these observations amounts at the most to 10% in 100°C. polymers. It is suggested that this part of the structure is that formed by hydrolysis and/or rearrangement of a part of the tertiary allylic chloride units which result from 1,2 polymerization of chloroprene. It is shown that only 50% of an acid‐catalyzed ionic polychloroprene can be accounted for by structures recognized in free‐radical polychloroprenes.
Kinetics of acrylonitrile polymerization in bulk
Authors: Thomas W. M. , Pellon J. J. 
Published: April 2003

AbstractAs a step toward the better understanding of acrylonitrile polymerization a kinetic study was made in bulk with azo and peroxy catalysts over the range 30 to 60°C. Rates were followed gravimetrically in most cases, and molecular weights were estimated from viscosity measurements. Electron micrographs and nitrogen sorption data were obtained. Following a short induction period (which could not be eliminated) polymer separated as a fine suspension, coagulated to form curds at a few tenths percent polymerization and formed a hard, porous mass at about 60% reaction. Product at 5 to 50% polymerization was in the form of dense particles about 0.5 micron across; these appeared to be aggregates of 400 A. particles. The rate of polymerization accelerated up to 1–3% conversion and was then nearly constant to about 50%, beyond which it could not be measured. Rate increased with the 0.8 power of catalyst concentration and showed an over‐all activation energy of 35 to 37 kcal./mole. Molecular weight varied inversely with the 0.2 power of the catalyst concentration, was nearly constant from 5 to 50% conversion and went through a slight maximum with temperature. To account for these observations a kinetic scheme is proposed that involves the possibility of unimolecular chain termination by a process of “burial.” This process is conceived of as a mechanism by which a growing chain may become shielded from further growth by coiling or embedding itself in the solid phase. Equations derived for rate and degree of polymerization fit the data adequately. Consideration is given to the simultaneous effects at high conversion of a small loss in initiator by thermal decomposition, of enrichment of the solution by shrinking liquid volume and of depletion of monomer.
The hydrolysis of cellulose Part I. The fine structure of egyptian cotton
Authors: Sharples A. 
Published: April 2003

AbstractThe kinetics of chain degradation have been studied for the heterogeneous hydrolysis of Egyptian cotton under mild acid conditions. The results have been interpreted to give estimates of accessibilities free from the defects associated with former measurements. The amount of accessible material in the undegraded cotton was found to be 10.8%, but during hydrolysis this is reduced to less than 5%. The recrystallization takes place at an early stage in the degradation, starting at a point when approximately one‐eighth of the intercrystalline chain segments have been broken.
Degradation of long chain molecules by ultrasonic waves. Part V. Cavitation and the effect of dissolved gases
Authors: Brett H. W. W. , Jellinek H. H. G. 
Published: April 2003

AbstractThe rate of ultrasonic degradation of polystyrene in benzene solution saturated with a number of gases was studied. The rate of degradation decreases with increasing solubility of the gas. Ultrasonic degradation is discussed generally on the basis of a theory for ultrasonic cavitation. A rate equation for this type of degradation is proposed. It is concluded that ultrasonic degradation is mechanical in its origin due to the adiabatic collapse of cavities.
Infrared spectrophotometric studies on polyethylene. II. Oxidation
Authors: Rugg Frank M. , Smith Joseph J. , Bacon R. Charles 
Published: April 2003

AbstractPolyethylene can be heat‐oxidized in air when temperatures in excess of 125°C. are employed or photo‐oxidized when exposed to ultraviolet radiation during weathering. Infrared spectrophotometric studies show that during these types of oxidation carbonyl groups are formed and the concentrations of the three types of carbon to carbon double bond groups present are altered. Grating spectra in the 5.6–6.0 micron region reveal that the carbonyl groups formed by heat‐oxidation are mainly ketonic (5.81 microns) although some aldehyde (5.77 microns) and acid (5.84 microns) groups are also present. In photo‐oxidized samples, the carbonyl groups are rather well distributed among the aldehyde, acid and ketone forms. For oxidized samples showing intense carbonyl absorptions, there is a small increase in the concentration of RHCCHR groups (10.35 microns) for both types of oxidation. At this same degree of oxidation both the heat‐and photo‐oxidized samples show decreases in the concentration of RRCCH2 groups (11.25 microns). However, this decrease is considerably more pronounced in the photo‐oxidized samples. Finally, there is a small decrease in the concentration of RHCCH2 groups (10.07 and 11.00 microns) in the heat‐oxidized samples which stands in contrast to a large increase in concentration of RHCCH2 groups produced by photo‐oxidation. The presence of an absorption maximum at 2.81 microns as the heat‐oxidation of polyethylene is occuring is indicative of unstable hydroperoxide groups.
Relation between the structure of polymers and their dynamic mechanical and electrical properties. Part I. Some alpha‐substituted acrylic ester polymers
Authors: Deutsch K. , Hoff E. A. W. , Reddish W. 
Published: April 2003

AbstractA comprehensive study of the dynamic mechanical and dielectric properties of acrylic polymers (polymethyl methacrylate, polymethyl‐α‐chloroacrylate) has been made; these two properties were found to be intrinsically correlated; results are given in graphic form. The hypothesis is proposed that each of several mechanical and dielectric dispersion regions found in a given polymer is associated with a definable structural feature, i.e., a group of atoms, in the polymer, such that each group gives rise to a mechanical dispersion and, if polar, also to a dielectric dispersion in the same temperature and frequency region; it should also be possible to trace the same dispersion from one polymer to another, provided they all contain the same group.
A new method for the determination of branching in polymers
Authors: Hayes Robert A. 
Published: April 2003

AbstractThe transfer constant for the butadiene‐polybutadiene system at 50°C. has been calculated from data obtained from a graft polymerization study of that system. This constant (K = 1.1 × 10−3) has been used to calculate that polybutadiene prepared in an emulsion system at 50°C. contains an average of one branch for every 800 monomer units.
Calculation of extrusion behavior of viscoelastic materials from the relaxation distribution function
Authors: Smith Thor L. 
Published: April 2003

AbstractA viscoelastic material when extruded rapidly through a short capillary or spinneret may exhibit an effective viscosity which is smaller than the usual or zero shear rate viscosity by a factor of several hundred. An equation is derived which expresses the effective viscosity as a function of the time the material spends in the spinneret (transit time) and the distribution function of Maxwellian relaxation times. It is assumed that the mechanical properties of the material may be represented by a generalized Maxwell model. Effective viscosities observed when a 25% cellulose acetate solution in a 96:4 (by weight) acetone:water solvent is extruded through a spinneret with radius 0.006 cm. and effective length 0.0186 cm. are given. The relaxation distribution function for the cellulose acetate solution is calculated from the dynamic viscosity data of Philippoff. From the distribution function and values of the transit time, effective viscosities are calculated and found to differ from the experimental values by −26 to 60%. In view of the fact that the effective viscosities are smaller than the zero shear rate viscosity by factors ranging from 145 to 10.8, the agreement between calculated and experimental values is quite satisfactory.
Rheology of polyisobutylene. II. Low molecular weight polymers
Authors: Leaderman Herbert , Smith Robert G. , Jones Robert W. 
Published: April 2003

AbstractThe flow and retarded‐elastic behavior of four polyisobutylene specimens (M̄w 1.09 × 104 to 8.54 × 104), measured in a concentric cylinder rotational viscometer, are reported. Under the conditions investigated the non‐Newtonian flow behavior can be represented by Ferry's equation. The logarithm of the viscosity η varied linearly with the reciprocal of the square of the absolute temperature. The time‐scale for retarded elasticity was found to vary with temperature in the same way as the viscosity. The normalized retarded elasticity functions at temperatures corresponding to unit viscosity are substantially identical. The time corresponding to a normalized retarded elastic compliance of 0.5 is about 10−5 η second when η is in poises. The reciprocal steady state shear compliances 1/J and internal shear moduli Gi in Ferry's equation are of the same order of magnitude for each polymer. The retardation time function L(ln τ) is calculated for one of the polymers, and then the dynamic response; these results are in good agreement with dynamic measurements on this material. From a consideration of the stress relaxation behavior of high molecular polymers, it is pointed out that there must exist another retarded elasticity mechanism, the time‐scale of which depends only on temperature and not on molecular weight. This second mechanism is masked in the reported experiments on low molecular polymers.
The concentration dependence of the sedimentation constants of flexible macromolecules
Authors: Wales M. , Van Holde K. E. 
Published: April 2003

AbstractData for a number of vinyl polymer‐solvent systems show that the constant Ks in the relation 1/S = (1/S0) (1 + KsC) (where S and S0 are sedimentation constants at the concentration C and zero respectively) is proportional to the intrinsic viscosity. The average constant of proportionality is 1.6. Assuming the Mandelkern‐Flory theory of the relation of frictional coefficient and intrinsic viscosity to root‐mean‐square end‐to‐end distance and Burgers' relation for the sedimentation constant of a dilute suspension of spheres, the ratio Ks/[η] is calculated to be 1.66. Molecular weights may be calculated from Ks and the limiting sedimentation constant, S0 without the use of the constants Φ and P, and agree well with molecular weights determined independently. These considerations apparently do not apply to cellulose derivatives, for which Ks is not proportional to [η].
Reactivity of polar monomers in copolymerization
Authors: Ham George E. 
Published: April 2003

AbstractAs a consequence of earlier establishment of electrostatic repulsion between nonterminal polar 1,2‐disubstituted olefins in polymers and like adding monomer, polar methylenic monomers were examined for such an effect. Acrylonitrile was found to exhibit such behavior in at least three systems: styrene–acrylonitrile, α‐methylstyrene–acrylonitrile, and α‐acetoxystyrene–acrylonitrile. Absence of such an effect was shown for methacrylonitrile, methyl acrylate, acrylic acid, methacrylic acid, and crotonic acid. A modified copolymerization equation involving r1, r, and r2 was presented. A convenient means of estimating r1 and r2 in this equation as well as in the ordinary copolymerization equation was shown.
Some properties of polyacetaldehyde rubber
Authors: Bovey F. A. , Wands R. C. 
Published: April 2003

AbstractCertain physical and chemical properties of samples of polyacetaldehyde prepared by M. Letort have been examined. Study of the rheological behavior of high molecular weight specimens of this polymer indicates that its internal strength is high, and that it shows typical rubbery elasticity. Under rapidly applied stresses, it shows a high modulus, indicating a high degree of internal friction. Correlated with this is a relatively high brittle point. Upon pyrolysis the polymer depolymerizes to yield the monomer, and likewise undergoes chain cleavage. About 200–400 monomer units are lost for each cleavage of the chain.
Viscosity of 25% solutions of cellulose acetate versus intrinsic viscosity distribution
Authors: Rosenthal A. J. , White B. B. 
Published: April 2003

AbstractThe 25% w/w solutions of blends of cellulose acetate fractions have higher viscosities than solutions of single fractions of the same average intrinsic viscosity. It was found that the viscosity of a blend can be related to its composition by the relationship:

where \documentclass{article}\pagestyle{empty}\begin{document}$[\bar \eta ]_{25\%}$\end{document} is the apparent intrinsic viscosity of the cellulose acetate blend in solution at 25% concentration, and [η]i are the intrinsic viscosities of the components. By application of this equation it was determined that only a portion of the high anomalous viscosity of solutions of cellulose acetate prepared from viscose grade wood pulp could be attributed to intrinsic viscosity distribution.
Relaxation distribution functions of polyisobutylenes in concentrated solutions
Authors: Ferry John D. , Jordan Ivo , Evans Warren W. , Johnson Myrle F. 
Published: April 2003

AbstractRelaxation distribution functions for concentrated solutions of six polyisobutylene samples, using three different solvents, have been derived from measurements by the methods of the single transducer, wave propagation, and stress relaxation following cessation of steady‐state flow. The ranges of molecular weight, concentration, and temperature were about 0.3 to 2.5 × 106, 5 to 40%, and −5 to 40°C., respectively. When plotted with reduced variables with a reference state of unit density and viscosity at a standard temperature, data at different temperatures superpose; data at different concentrations superpose except for the two samples of highest molecular weight, where there are perceptible deviations. The reduced distribution functions for all the samples lie close together at long times where there is a drop associated with the finite lengths of the molecules. The theory of Rouse for viscoelastic properties of dilute solutions, when modified for concentrated solutions by assuming that all segmental mobilities are equally affected by interlacing of neighboring molecules, agrees with the reduced mechanical properties at long times fairly well. However, it does not predict the plateau region characteristic of distribution functions of polymers of high molecular weight. The existence of this plateau in concentrated solutions and undiluted polymers represents an abnormal prolongation of the longest relaxation times in these systems, which is attributed to molecular coupling by entanglement as discussed by Bueche with respect to steady flow viscosity.
The dielectric increment of a carboxymethylcellulose as a function of the degree of ionization
Authors: Allgén Lars‐Göran 
Published: April 2003

AbstractThe dielectric increment of a specimen of carboxymethylcellulose in aqueous solution has been studied as a function of pH. For the free acid a low increment was obtained which increased with increasing ionization (sodium salt). With excess sodium or hydrogen ions the increment decreased. Similarly there was a marked increase of the increment per gram per liter for the sodium salt with increasing dilution. The dielectic increments obtained for various salts of carboxymethylcellulose followed the order: Li+ > Na+ > NH4+ > K+ in agreement with the ion exchange affinities found previously for these ions (reversed order). The data have been interpreted along the lines of current theories for polyelectrolytes, by taking into consideration the net charge of the polyion, and the polyion‐counterion association under varying conditions.
Water induced acceleration of the diffusion of organic vapors in polymers
Authors: Long F. A. , Thompson L. J. 
Published: April 2003

AbstractThe influence of water vapor on the rate of diffusion of organic molecules has been studied at 40°C. by the sorption method for the systems water‐acetone‐polyvinyl acetate, water‐carbon tetrachloride‐polyvinyl acetate, water‐acetone‐cellulose acetate (37.9% acetyl) and water‐benzene‐polystyrene. For the first three systems the rate of diffusion of the organic vapor is markedly faster for the mixture of water and organic vapor than for the pure organic vapor. With polyvinyl acetate, the rate of diffusion of 80 mm. of acetone is increased about 25‐fold if 36 mm. of water vapor is mixed with the acetone. Diffusion of the larger carbon tetrachloride molecule is accelerated by water even more than is acetone. Water vapor at a pressure of 36 mm. causes about a 30‐fold increase in the rate of diffusion of 80 mm. of acetone into cellulose acetate even though the diffusion of acetone itself into cellulose acetate is anomalous. With polystyrene the presence of water vapor causes no acceleration of the diffusion of benzene which is the expected result since, in contrast to the other two polymers, polystyrene sorbs only very small amounts of water. It is concluded that the marked effect of water vapor on the diffusion of organic vapors into polyvinyl acetate and cellulose acetate involves (a) a rapid diffusion of water into the polymer and (b) more rapid diffusion of the organic vapor into the “water plasticized” polymer than into the dry polymer.
Polyelectrolytes. XI. Electrophoresis in solutions of poly‐4‐vinyl‐N‐n‐butylpyridinium bromide
Authors: FitzGerald Emerson B. , Fuoss Raymond M. 
Published: April 2003

AbstractThe following systems were observed in the Tiselius moving boundary apparatus: (1) poly‐4‐vinyl‐N‐n‐butylpyridinium bromide (PBr) with added potassium bromide/potassium bromide in osmotic equilibrium with the PBr‐KBr solution; (2) KBr/PBr, both solutions adjusted initially to the same conductance; (3) LiBr/PBr and (4) PBr‐(c1)/PBr(c2). Series 1 showed that the mobility of the polycation decreased with increasing KBr concentration. The schlieren patterns were strikingly asymmetric. Series 2 showed that the mobility of the polycation does not depend very much on molecular weight. Series 3 showed strong interaction between polyelectrolyte and simple electrolyte. Series 4 indicates that the mobility of the polycation depends on concentration much more than in the case of simple electrolytes. Both in Series 3 and 4, more moving boundaries appeared than are theoretically called for by the number of ionic species present.