bluuebunny/crossref_metadata_2025_split huggingface dataset:
Osmotic pressure measurements with solute‐permeable membranes
Authors: Gardon J. L. , Mason S. G. 
Published: April 2003

AbstractA method of determining the osmotic pressure of a solute which can diffuse through the membrane is described. It is shown theoretically that after a certain time interval a plot of the logarithm of the indicated osmotic pressure against time yields a straight line which can be extrapolated to zero time. The true value of the initial osmotic pressure is calculated by correcting the extrapolated value for the rate of transfer of solute and solvent through the membrane and for the partition coefficient of the solute between the membrane and the solvent. The various correction factors are calculated from experimentally determined quantities. By the use of cellophane membranes, osmotic pressures of lignin sulfonates with molecular weights as low as 4,300 have been evaluated.
Crystallinity and orientation in silicone rubber. I. X‐ray studies
Authors: Ohlberg Stanley M. , Alexander Leroy E. , Warrick E. L. 
Published: April 2003

AbstractA technique is described for quantitatively examining the diffraction pattern of polydimethylsiloxane at and below room temperature with the x‐ray diffractometer. The crystalline fraction of the unstretched material is determined by the classical method developed for natural rubber. In the case of the stretched elastomer, a modified procedure is required which takes into account the extent of preferred orientation of the molecular chains. As the extension ratio is increased, the crystallization temperature rises and preferential orientation of the crystallites with respect to the extension axis increases. The crystallinity increases with decreasing temperature and appears to be independent of the extension ratio below −60°C. An over‐all crystalline fraction of 0.42 was measured for a silicone rubber specimen at −60°C. and an extension ratio of 6.3.
Crystallinity and orientation in silicone rubber. II. Physical measurements
Authors: Warrick E. L. 
Published: April 2003

AbstractDensity data for a silica‐filled dimethylpolysiloxane rubber define incipient crystallization conditions and indicate the forms of crystalline growth for the unstressed rubber and for a sample at 200% elongation. Temperature—tension data for the same silicafilled rubber show incipient crystallinity temperatures as a function of extension. While stress relaxed filled silicone rubber samples show a tension decrease with falling temperatures, they are far from ideal rubbers. The change in polymer filler interaction links with temperature may account for this nonideality. Both the filled and unfilled rubbers show a thermoelastic inversion. The comparison with x‐ray data yields good evidence that crystallization is responsible for the tension rise at low temperatures. This rise may stem from the tendency of silicone rubber to crystallize without altering the orientation of chain segments. The ability to crystallize chain elements in all states of orientation may be founded upon a much greater chain segment mobility for silicone rubber than found with natural rubber. Normal stress—strain curves taken at low temperatures qualitatively show the effects of crystallization.
Reactivity ratios of vinyl esters of aliphatic acids and some common vinyl monomers
Authors: Marvel C. S. , DePierri W. G. 
Published: April 2003

AbstractThe copolymerization reaction of five vinyl esters of aliphatic acids with vinyl chloride, vinylidene chloride, acrylonitrile, butadiene, styrene, and methyl acrylate have been studied. The reactivity ratios have been determined and the Q and e values for the esters have been calculated. The results clearly show that the nature of the acyl residue in a vinyl ester has little influence on its reactivity ratio in a copolymerization reaction or on the Q or e value.
Nuclear spin resonance line width measurements of polyethylene
Authors: Collins R. L. 
Published: April 2003

AbstractThe proton spin resonance spectrum of polyethylene consists of two superimposed lines. The narrow line is attributed to the amorphous phase, and the broad line to the crystalline phase. The width of the narrow line was measured at various temperatures from 25−130°C. for Alathon 10, Alathon 14, DYNH, and Marlex 50 polyethylene and it was found to vary with temperature. The results have been interpreted using the theory of motional narrowing, which indicates that the product of temperature and line width is proportional to the viscosity. A plot of log of line width times temperature versus reciprocal temperature is linear for Marlex 50 polyethylene, and is curved for the other three. The linearity is believed due to the simple structure of the material, and the slope yields an activation energy of 8200 cal./mole. The curvature of the other data is believed due to extensive branching which causes a change of composition of the amorphous phase upon cooling, and the apparent activation energy varies from 11,800 cal./mole at 130°C. to 4900 cal./mole at 25°C.
Crystalline recovery of quenched polyethylene
Authors: Collins R. L. 
Published: April 2003

AbstractThe effect of time and temperature on the crystalline recovery of quenched Marlex 50 polyethylene has been investigated. Quenching thin films in ice water reduced the room temperature crystallinity from a normal value of 93 to 82%. These specimens were maintained at 25, 66.2, and 106.4°C., and the time variation of crystallinity was followed by nuclear spin resonance. The crystalline recovery appears to follow the empirical formula, X = A + B log t, where X is the percentage crystallinity and t, is the time in hours. The rate, X, increases with temperature. The temperature‐dependence of B was computed by assuming the rate to be controlled by diffusion in the amorphous phase. The temperature‐dependence of diffusion is determined by nuclear spin resonance line width measurements to be exp {−8700/RT}. The rate is then X = C/t exp {−8700/RT}, and C, evaluated at 25, 66.2, and 106.4°C., is 2.2 ± 1.9, 1.7 ± 0.5, and 2.1 ±0.2 × 105. This agreement is within the probable error, and justifies the assumption of diffusion as the rate‐controlling factor. The result is X = 2.04 × 105(1/t) exp { −8700/RT} and X = A + 4.70 × 105 log t exp {−8700/RT}.
The scattering of light from thin polymer films. IV. Scattering from oriented polymers
Authors: Norris Forrest H. , Stein Richard S. 
Published: April 2003

AbstractThe scattering of both unpolarized and polarized light by a series of stretched polyethylene films has been studied. The radiation envelope of the scattered light loses its cylindrical symmetry upon stretching. The dissymmetry depends upon the orientation of the stretching direction of the film as does the intensity of scattered light. The results imply a scattering unit which is anisotropic both in shape and in polarizability. The largest dimension and highest polarizability lie in the stretching direction. The Debye‐Bueche theory has been generalized to describe oriented anisotropic systems. The single parameter, a, describing the size of the heterogeneity is replaced by two parameters, a and c. The mean‐square dielectric constant fluctuation η2 depends upon the principal polarizabilities of the scattering unit and upon its orientation. The parameters are evaluated for the series of polyethylene samples. A model is proposed which accounts for the variation of the parameters as well as the changes occuring during melting and crystallizing the polymer.
Molecular weight of ethyl cellulose by dielectric dispersion of solutions in dioxane
Authors: Scherer Philip C. , Hawkins M. C. , Levi D. W. 
Published: April 2003

AbstractThe dielectric dispersion of dilute solutions of ethyl cellulose in dioxane was studied using a “differential” bridge method for the range from 200 cycles to 300 kilocycles. The frequency where the dispersion was 0.50 was recorded as the “critical” frequency. The critical frequency is related to the intrinsic viscosity of the samples as log 100[η] = 2.97 − 0.59 (vc). Since the determination of critical frequency is very rapid this method apparently is satisfactory for molecular weight determinations in the systems studied.
Irradiation effects in plexiglas
Authors: Gross Bernhard 
Published: April 2003

AbstractSamples of methyl methacrylate were irradiated with 2‐m.e.v. electrons. Stopping and trapping of the incident electrons in the dielectric leads to the formation of a negative space charge. Under proper conditions the electric field of this charge can produce breakdown accompanied by the appearance of a characteristic discharge pattern. The nature of this effect is discussed. It is shown that the bulk of the space charge is concentrated in a narrow layer at a depth corresponding to the effective range of the electron beam. The quantity of charge released during breakdown is measured for various doses and compared with the value of the intercepted charge.
Etude par diffusion de la lumiere et viscosimetrie du bromure de polyvinyle en solution
Authors: Ciferri A. , Kryszewski M. , Weill G. 
Published: April 2003

AbstractPolyvinylbromide prepared by photopolymerization was fractionated. The molecular weights of the fractions were determined by a method which takes into account the fluorescent light for any polarization of fluorescence and anisotropy of the scattering molecule. The second virial coefficient‐molecular weight relation, the intrinsic viscosity‐molecular weight relation, and the values of the end‐to‐end distance indicate that P.V.B. follows the classical laws for a molecular coil. The molecular distribution curve was determined. The ratio Mw/Mn = 1.8.
Change in electrical resistivity of some high polymers during isothermal polymerization
Authors: Aukward J. A. , Warfield R. W. , Petree M. C. 
Published: April 2003

AbstractEpoxy, polyester, and styrene isothermal polymerizations have been monitored electrically. Sample resistivity—time records at different temperatures are reported for each class of polymer. These plots suggest that relative rates of reaction could be conveniently obtained if a correlation between extent of polymerization and electrical resistivity were known for the particular resins studied. Qualitative agreement between changes in infrared absorption and changes in volume resistivity as a measure of the extent of polymerization has been obtained.
Thermal degradation of polymethacrylonitrile. Part II. The coloration reaction
Authors: Grassie N. , McNeill I. C. 
Published: April 2003

AbstractThe thermal coloration which occurs in copolymers of methacrylonitrile with small amounts of methacrylic acid has been studied at 140°C. The infrared spectra of colored polymers show a decrease in nitrile absorption (which has been followed quantitatively) and new absorption appears, mainly at 1693–1490 cm.−1 No volatile material is lost during coloration and molecular weight measurements show that neither chain scission nor crosslinking is involved. Copolymers of different compositions have been used to control the length of sequences of adjacent methacrylonitrile units, and it has been found that coloration is inhibited by larger concentrations of methacrylic acid. Colored polymer slowly reverts to the original material in solution, and rapid decoloration is effected by addition of aqueous solutions of acids, alkalis, and salts. A structure has been deduced for colored polymethacrylonitrile analogous to those proposed previously for paracyanogen and colored polyacrylonitrile. Essentially this is the results of the linking up of adjacent nitrile groups to form conjugated carbon‐nitrogen sequences of considerable length. It is suggested that this structure is formed in a nonradical chain process initiated at methacrylic acid units and propagated through adjacent nitrile units. The changes in solubility properties are not the result of crosslinking but of the rigidity of the modified polymer structure.
Intrinsic viscosities of cellulose derivatives
Authors: Flory P. J. , Spurr O. K. , Carpenter D. K. 
Published: April 2003

AbstractIntrinsic viscosities of cellulose acetates of degrees of substitution 2.86 and 3.00 and of cellulose trinitrate have been investigated as functions of temperature, solvent, and molecular weight. Large negative temperature coefficients (ca. −0.6% per degree) of [η] appear to be characteristic of cellulosic chains. These observed decreases in [η] with temperature are due to increases in chain flexibility, which are reflected in decreases in the characteristic ratio r/M. The rather large variations in [η] with the solvent are shown also to be manifestations of altered chain flexibilities brought about in some manner, as yet unexplained, by specific solvent interaction. This behavior stands in marked contrast to that of other polymers for which r/M is independent of the solvent and varies only slightly with temperature, and for which solvent effects on [η] are wholly attributable to changes in the molecular expansion (α3) brought about by solvent action,
Viscoelasticity of some crosslinked polymers
Authors: Tokita Noboru , Kanamaru Kisou 
Published: April 2003

AbstractTaking, as the samples for investigation, filaments of viscose rayon (60% crystallinity) and acetate rayon (54% acetyl) both crosslinked to various extents by tetramethylenebisethylene urea and tetramethylenediisocyanate urea as the crosslinking agents, the dynamic and transient moduli, E′, G1, G2, the internal friction, Q−1, and the apparent activation energy for relaxation of segment, ΔU, were measured and the results were considered in their relation to the degree of crosslinking. From the results, the following conclusions were made: (1) When crosslinking is caused by long molecular chains of the crosslinking agents between the nearest neighboring molecules, the intermolecular spaces are widened to some extent and the restraint of segmental motion due to the dipole interaction of the strong polar hydroxyl groups is partly relieved so that the decreases in ΔU, E′, G1, and G2 are rather caused by a small amount of the crosslinking agents; for example, while the values of ΔU and E′, for the original viscose rayon not crosslinked are 230 kcal./mole and 2.0 × 1011 dynes/cm.2, respectively, they both decrease with an increase in degree of crosslinking and each shows a minimum (ΔU = 95 kcal./mole, E′ = 0.9 × 1011 dynes/cm.2) at the amount of bound nitrogen N = 0.73%. When the crosslinking proceeds further, the primary crosslinking effect makes its appearance so that ΔU, E′, G1, and G2 begin to rise with an increase in degree of crosslinking. (2) Due to the strong solvating or plasticizing effects, the water molecules absorbed bring about a strong decrease in the apparent activation energy; ΔU = 90 kcal./mole at 80% RH, 200 kcal./mole at 66% RH, and 210 kcal./mole at 55% RH for viscose rayon.
Polymerization of vinyl stearate by high energy electrons
Authors: Burlant W. , Adicoff A. 
Published: April 2003

AbstractVinyl stearate has been polymerized by 1000 kv. electrons with field intensities ranging from 1.0 × 103 to 20 × 103 rep per second; the polymers are considered to be branched. A discontinuity of reaction rate and molecular weight with respect to temperature was noted in the vicinity of monomer melting point, and it is suggested that in this temperature region, the diffusion constant for propagation is easily affected. A linear relationship between field intensity and polymerization rate, and a constancy in molecular weight with varying field intensities, at constant total dose, indicated that polymerization occurs in “volume elements.”
Copolymerization of vinylene carbonate
Authors: Hayashi K. , Smets G. 
Published: April 2003

AbstractThe copolymerization of vinylene carbonate VC (M2) with several vinyl monomers (M1) has been examined. The reactivity ratios r2 and r1 have been determined in the system VC‐vinyl acetate (0.27 and 3.0), VC‐vinyl chloride (0.09 and 5.2), VC‐vinylpyrrolidone (0.4 and 0.7), VC‐methyl methacrylate (<0.01 and ∼70). These values indicate for vinylene carbonate in the Alfrey‐Price scheme a reactivity Q equal to 0.012 and a polarity e of −0.6. From the r1 and r2 parameters of the system vinyl acetatevinylpyrrolidone (0.38 and 0.44, respectively) the Q and e values of vinylpyrrolidone have also been determined: Q = 0.11 and e = −1.6. The copolymers of vinylene carbonate and vinyl acetate yield on hydrolysis polyalcohols (CH2CHOH)x(CHOH)y of which the solubility decreases with increasing content of hydroxyl groups.
Studies on the sorption of moisture by polymers. I. Effect of crystallinity
Authors: Valentine L. 
Published: April 2003

AbstractThe relation between the sorption of moisture by polymers and their crystalline structure is reviewed, and it is concluded that, if a dry polymer can form well‐defined crystallites, then these crystallites will usually be inaccessible to water vapor. The ratio of the moisture sorption of a polymer to that of its completely amorphous form will thus be a measure of the noncrystalline fraction. Methods of estimating the sorption of the amorphous form of a polymer that is normally partially crystalline are then discussed. In one method, the polymer is prepared in various degrees of crystallinity, and the relation between sorption and crystallinity is extrapolated to zero crystallinity. A variant of this method involves the measurement of the accessibility to some simple reagent that reacts only in the noncrystalline regions, e.g., D2O; the relation between sorption and accessibility is extrapolated to 100% accessibility. The second main technique is based on the fact that conversion of a partially crystalline homopolymer into a random copolymer frequently destroys the crystallinity over a wide range of compositions, within which there is a linear relation between sorption and composition. Extrapolation of this linear relation enables the sorption of the completely amorphous homopolymer to be found. These methods have been applied to several polymers, e.g., cellulose, polyvinyl alcohol, wool. For cellulose, in particular, very good agreement is found between many different methods, and the sorption isotherm of amorphous cellulose has been calculated.
On the stress relaxation of nylon 6
Authors: Yoshitomi Tatsuya , Nagamatsu Kazuo , Kosiyama Kiiti 
Published: April 2003

AbstractThe stress relaxation of low‐crystallinity nylon 6 is measured by torsional method at various temperatures in three (0, 40, and 75%) relative humidities. As the whole procedures are very accurate, the results contain little experimental error. The relaxation data at 0 and 75% relative humidity can be reduced to respective master curves by Ferry's reduction method. Considering the changes of structure by difference in humidity, it is found that these two master curves are reduced further to one single general master curve by the aid of some molecular theory of the crystalline polymers. By the use of first‐order approximation, the relaxation time spectrum of this crystalline polymer is obtained for a very wide time scale range, more than 1021 sec. The resultant spectrum is fairly high and flat, reflecting the characteristic features of crystalline polymers. It has, however, two weak but distinct maxima, corresponding to the so‐called “wedge” and “box” distributions in the relaxation time spectrum of the amorphous polymers. Based on the existence of this box distribution in the spectrum, it is suggested that there should exist some sort of clusters effective in the mechanical behavior of the crystalline polymers.
Copolymerization of vinylene carbonate with vinyl thiolacetate and N,N,N‐triethyl‐N‐[2‐(methacryloxy) ethyl]ammonium iodide with 4‐vinylpyridine
Authors: Overberger C. G. , Biletch H. , Nickerson R. G. 
Published: April 2003

AbstractCopolymerization reactivity ratios for the system vinyl thiolacetate (M1)‐vinylene carbonate (M2) have been determined to be r1 = 12.9 ± 1.1 and r2 = 0.04 ± 0.01 by the method of Fineman and Ross. For the system 4‐vinylpyridine (M1) and N,N,N‐triethyl‐N‐[2‐(methacryloxy)ethyl]ammonium iodide (M2)r1 = 0.30 ± 0.02 and r2 = 0.61 ± 0.09 as determined by use of the “integrated equation” of Mayo and Lewis. A base‐soluble, easily oxidizable sulfhydryl copolymer has been prepared by hydrolysis of the copolymer of vinyl thiolacetate and vinylene carbonate. The sulfhydryl copolymer is of interest as a successful short lived prophylactic for ionizing radiation.
Diffusion of allyl chloride in polyvinyl acetate. Part I. The steady state of permeation
Authors: Meares P. 
Published: April 2003

AbstractOnly for neopentane in polyisobutene and for methylene chloride in polystyrene has the diffusion coefficient of a vapor in a polymer been determined both by steady‐state and by transient‐state methods. In the former case, well above the glass temperature of the polymer, there was a good agreement. In the latter case, below the glass temperature, the two methods seriously disagreed. This paper describes steady‐state measurements for allyl chloride in polyvinyl acetate at 40°, a few degrees above the glass temperature. Experiments were made with thin membranes of polymer mounted in a stainless steel cell. Vapor permeating was collected in a known volume and its pressure determined as a function of time, using a Pirani gage, for short periods until a steady state was established. The permeation data have been used to determine the integral D, differential D, and intrinsic 𝒟 diffusion coefficients as a function of concentration cg up to 0.085 g. allyl chloride per g. polymer. Log D is found to be a curved function of cg. Kokes and Long, from observations of sorption kinetics, have also determined D for this system and find log D to be linearly related to cg. The data given here can also be represented by a straight line, but of steeper slope, over the concentration range studied by Kokes and Long. This line and the data of Kokes and Long extrapolate to the same value of log D at cg = 0. It is concluded that transient and steady‐state determinations agree when there is no polymer swelling but that, at finite concentrations of penetrant, the polymer chains do not have time to assume their equilibrium configuration during the transient‐state experiments. Complete relaxation occurs before a steady state is established and this leads to a higher value of D being recorded. Bueche's theory of segmental mobility can be applied to the change in jumping frequency of the polymer segments with diluent concentration at constant temperature. Assuming a direct proportionality between jumping frequency and 𝒟, the theoretical equation successfully predicts the observed dependence of 𝒟 on the volume fraction of diluent using physically justified values for all parameters.