bluuebunny/crossref_metadata_2025_split huggingface dataset:
Column fractionation of polymers. VII. Computer program for determination of molecular weight distributions from gel permeation chromatography
Authors: Pickett Harry E. , Cantow Manfred J. R. , Johnson Julian F. 
Published: April 2003

AbstractGel permeation chromatography produces a type of differential molecular weight distribution directly and rapidly. Conversion of these data to conventional molecular weight distributions and plots of distributions is time‐consuming. A computer program is described to perform these operations readily. Input data from the automated chromatograph, elution volume, and recorder deflection are converted to unit sensitivity and base line corrections applied. The curve is then numerically integrated and a calibration curve used to convert elution volumes into molecular weights. Various calibration curves can readily be introduced into the program. The output, in addition to tabulation of cumulative and differential molecular weight distributions, contains values of M̄n, M̄v, M̄w, M̄z, and M̄z+1. Importantly, a reduced absolute area, i. e., area computed for unit sensitivity on a unit concentration basis, is tabulated. An additional time‐saving eature is the printing out of differential and cumulative molecular weight distribution curves and of a differential histogram.
Effect of temperature on viscosity of amylose
Authors: Khairy M. , Morsi S. , Sterling C. 
Published: April 2003

AbstractViscosity parameters were obtained for maize maylose (molecular weight of 107,000) in 1N KOH at 25, 30, 35, and 40°C. Intrinsic viscosity continuously decreased and Huggins' constant k' continuously increased with increasing temperature. The temperature dependence of intrinsic viscosity, d[η]/dT, was −2.12 × 10−2/°C.
Studies on polymer blends: Blending methods for natural rubber and styrene‐butadiene rubber
Authors: Shundo Minoru , Imoto Minoru , Minoura Yuji 
Published: April 2003

AbstractThe relations between the properties and the blend ratios of natural rubber (NR) and styrene‐butadiene rubber (SBR) blends were studied in comparison with four blending methods. The relations between the properties of unvulcanized and vulcanized blends and the blend ratios of blends prepared by means of solution blending, latex blending, roll blending, and Banbury mixer blending were studied. In practice, such rubber blending methods as roll blending are more effective for obtaining uniform blends than Banbury mixer blending the latter. In roll blending, it is more effective to blend NR and SBR by way of a master‐batch in which the ingredients are compounded beforehand than to blend raw rubber. In solution and latex blending, very uniform blends are easily obtained. It was found, however, that the properties of NR/SBR blends prepared carefully showed a direct relation to their blend ratios, regardless of blending method used.
Sur une méthode d'obtention de polymeres en poudre par précipitation
Authors: Chapiro Adolphe , Palma Giancarlo 
Published: April 2003

AbstractMany polymers can be obtained in powder form by precipitation from dilute solutions under well‐defined conditions. For this purpose the precipitant is first added gradually until a permanent cloudiness is reached. At this point a large excess of precipitant is suddenly poured into the solution. Many examples are given. Very fine powders have also been obtained from gummy or rubberlike polymers by carrying out the precipitation at a temperature below the glass transition point of the polymer.
Semipermeable membranes of cellulose acetate for desalination in the process of reverse osmosis. IV. Transport phenomena involving aqueous solutions of organic compounds
Authors: Kesting R. E. , Eberlin J. 
Published: April 2003

AbstractTransport of a solute through semipermeable membranes of secondary cellulose acetate is dependent both upon its capacity for hydrogen bonding with boung water and upon steric factors. The rate of transport of water is influenced by Gibbs adsorption of solute.
Reactivity of functional groups in surface coating polymers. Part I. Hydroxyl groups in alkyd resins
Authors: Solomon D. H. , Hopwood J. J. 
Published: April 2003

AbstractThe factors which can influence the availability of functional groups in polymers are considered. In particular, the importance of hydroxyl groups in the formation and Film‐forming reactions of alkyd resins is discussed, and evidence is presented to suggest that the number of hydroxyl groups available for chemical reaction is not necessarily equivalent to the theoretical value. Factors which influence the availability of the hydroxyl groups are considered, and some of the properties of the alkyd are related to the available hydroxyl content.
Adsorption of surfactant on polystyrene‐styrene interfaces
Authors: Griskey Richard G. , Woodward Clifford E. 
Published: April 2003

AbstractThe adsorption of sodium dodecyl sulfate on polystyrene‐styrene interfaces has been studied. Polystyrene interfaces of 20 and 60% were considered. Initial surfactant concentrations used in the study were 0.0004, 0.0008, and 0.004 mole/l. Two temperature levels, 25 and 75°C., were studied. Results showed no effect of initial surfactant concentration for a 20% interface at 25°C. However, the data for the 60% interface at 25°C. showed an effect of initial surfactant concentration. The apparent anomaly in the results regarding effect of initial surfactant concentration was explained in terms of the behavior of polystyrene‐styrene as a mixed absorbent and the work of Harkins and co‐workers, which showed that surfactant adsorption was a function of initial surfactant concentration over certain concentration ranges. Rate of surfactant adsorption appeared to be a function of surfactant adsorption raised to a power. The order of the adsorption appeared to be first‐order for the 20% interface and second‐order for the 60% interface.
Estimation of kinetic parameters during polymer degradation from two DTA traces
Authors: Reich Leo 
Published: April 2003

AbstractA method is presented for the estimation of kinetic parameters during polymer degradation from two DTA traces. By this method, changes in mechanism with conversion may be detected. The method is applied to polyethylene, polypropylene, polystyrene, and polytetrafluoroethylene (Teflon). The agreement between observed and reported values of kinetic parameters is good. Advantages and disadvantages of the method are discussed.
DTA and TGA studies of flame‐resistant fabrics
Authors: Perkins R. M. , Drake G. L. , Reeves W. A. 
Published: April 2003

AbstractPreliminary thermal studies were made of cotton fabrics which had been made flame resistant by chemical modification or by blending with a flame‐resistant modified acrylic fiber. DTA and TGA thermograms were made in both nitrogen and oxygen atmospheres. Differences were found in the thermograms of the untreated controls, depending upon amount of purification. Fabrics treated with the flame‐retardant formulations had lower decomposition temperatures and higher percent residue. Decomposition in oxygen was more complete and proceeded at a lower temperature. Infrared spectra of selected samples, which had been partially or completely charred, were examined. These data are related to theories about the degradation of flame‐resistant cotton fabrics.
Use of the dielectrometer for the determination of the complex dielectric constant in the microwave region in organic high polymers at various temperatures
Authors: Calamia Mario , Butta Enzo , Frosini Vittorio 
Published: April 2003

AbstractA commercial type dielectrometer has been utilized for determining the complex dielectric constant of insulating materials as a function of temperature. For low‐temperature measurements, modifications of the apparatus have been made, by which the lower section of the guide, containing the specimen, is insulated from the upper section by means of a Teflon disk, in order to permit measurements under vacuum without difficulties arising from moisture condensation. Taking into account the modifications made, relations between the experimentally measured quantities and the complex dielectric constant have been elaborated, and error analysis made, and best conditions to perform experimental measurements determined. For high‐ and medium‐loss materials, in the low‐temperature range, an accuracy of the order of 1% in ϵ′ and of 10% in ϵ″ have been calculated. Better results can be obtained for measurements at high temperature. The apparatus performance and the accuracy of measurements have been checked through measurements of the complex dielectric constant of different polar polymers at frequencies of the order of 9 × 109 Hz, at temperatures between −150 and 200°C. The experimental results are in good agreement with literature data derived from experimental measurements with other techniques and with the behavior expected on the basis of the results from radiofrequency measurements through considerations of molecular mobility in relation to molecular structure.
Nonlinear least squares: A method for simultaneous thermal property determination in ablating polymeric materials
Authors: Pfahl Robert C. 
Published: April 2003

AbstractA method of data interpretation known as nonlinear least squares has recently been applied by several authors to the study of polymeric materials. Nagler has used a modified method proposed by Blizzard and Jirka and has concluded that the method is impractical because it requires excessive computer time. It is shown that the difficulties Nagler encountered are inherent in Blizzard and Jirka's method, but not in the basic method. Three steps are outlined to minimize computer time, and a summary of successful applications is presented.
Turbidimetric thermal gradient technique for the estimation of compositional distribution of ethylene copolymers
Authors: Imhof L. G. 
Published: April 2003

AbstractA new experimental technique has been developed for determining the compositional distribution of ethylene copolymers and blends of ethylene homopolymers and copolymers. The method is similar to the turbidimetric titration procedure, but with crystalline precipitation of the various structural species effected by lowering of the temperature. Experimentally, a Brice‐Phoenix light‐scattering photometer, equipped with a stirred heated cylindrical cell is used as a turbidimeter for measuring the light transmission through a liquid system. The decreasing light transmission of a 0.01% solution in a fixed ratio of solvent and nonsolvent of α‐chloronaphthalene and dimethyl phthalate, with a temperature drop of 2°C./min., is plotted against temperature on an X‐Y recorder. The more highly branched molecules, that is, those containing higher comonomer content, are the less crystalline, hence are more soluble and precipitate at the lower temperatures. Compositional distribution is estimated from the cooling curves by two procedures: (1) the broader temperature range over which a nonuniform resin precipitates out of solution is compared to that of a more uniform resin, and (2) the higher initial cloud point of a mixture or nonuniform copolymer is compared to the cloud point–comonomer content relationship developed for uniform resins. The effects of molecular weight and molecular weight distribution are shown to be small relative to the effects of structural distribution. The compositional distribution of the ethylenepropylene copolymers studied varies from narrow to broad, depending on the specific coordination catalyst and polymerization method used. Ethylene–vinyl acetate copolymers, on the other hand, are uniform because of the 1:1 reactivity ratios of ethylene and vinyl acetate. Synthetic mixtures of ethylene–vinyl acetate resins of varying vinyl acetate content exhibit the expected nonuniformity. This technique has also been successfully applied to mixtures of high‐ and low‐density polyethylenes, further demonstrating the utility of this new rapid tool for structural characterization. Experimental time is about 2 hr.
Kinetics of the addition stage in the melamine–formaldehyde reaction
Authors: Gordon M. , Halliwell A. , Wilson T. 
Published: April 2003

AbstractThe addition reaction between melamine and formaldehyde has been kinetically separated from the subsequent condensation stage by suitable choice of concentration and temperature conditions. The reaction, which is reversible, has been monitored by estimation of the free formaldehyde content of the system. It has been investigated over the range of mean degree of methylolation 1 < R′ < 3.7 of the melamine nuclei, the temperature range 25–55°C., and the pH range 5.7–10.2. The rate data thus obtained have been treated according to the random reversible addition scheme for which reasonable, first approximation, agreement was obtained. Average kinetic and thermodynamic constants have been calculated and are discussed in terms of the present model. The factors which are likely to cause deviations from randomness are described. The addition of formaldehyde to melamine proceeds by superposition of an OH−‐catalyzed step with a minor solvent‐catalyzed or uncatalyzed one.
Determination of the thermal stability and trace volatiles content of polymers. A hot‐filament thermal analysis technique
Authors: Eggertsen F. T. , Stross F. H. 
Published: April 2003

AbstractThe thermal stability and trace volatiles content of polymers can be determined rapidly and conveniently by using a hot‐filament pyrolyzer for heating the sample. The filament unit, of a type employed for pyrolysis‐GLC analysis, consists of a platinum coil with an attached platinum/platinum–rhodium thermocouple for measuring the sample temperature. As the sample is heated the volatile products are monitored directly with a flame ionization detector, a dual recorder being used to chart both temperature and volatiles yield. At any stage of heating the products are analyzed, if desired, with a suitable GLC column. Thermal stability measurements of several polymers were generally consistent with results by conventional thermogravimetric analysis. Advantages of the method are high sensitivity for detection of low decomposition rates, speed of the temperature adjustment, simplicity of the apparatus, and small sample requirement.
Studies of the chemical modifications of wool and their effects on the wool‐water relationship. Part I. Chemical modification of wool
Authors: Gervasi J. A. , Stannett V. 
Published: April 2003

AbstractWool has been modified to render it more hydrophobic by two methods. The first method involved treating the wool with benzoyl, lauroyl, stearoyl, and dodecenyl chlorides and with trifluoroacetic anhydride. Substantial degrees of reaction with the wool were achieved when the correct solvent media and reaction conditions were used. These varied with the particular reagent employed. Pyridine was particularly effective with the acid chlorides, whereas dimethyl sulfoxide was best with trifluoroacetic anhydride. Pyridine is believed to function both as a swelling agent and as an acid acceptor in these treatments. The second method of treatment was the grafting of vinyl and allyl monomers to wool by the use of high energy radiation. Both 60Co γ‐rays at 0.3 Mrad/hr. and Van de Graaff γ‐radiation at 3 Mrad/min. were found to be highly effective. The presence of a swelling agent in the monomer solution was found to be essential even in the case of acrylonitrile in dimethyl formamide. Water and methanol in small amounts were found to be highly efficient swelling agents. Substantial quantities of monomer could be grafted in most cases without difficulty when the correct conditions were used.
Studies of the chemical modifications of wool and their effects on the wool–water relationship. Part II. Wool‐water relationships of modified and unmodified wool
Authors: Williams J. L. , Stannett V. , Armstrong A. A. 
Published: April 2003

AbstractThe wool–water relationships of the modified wools prepared as described in Part I of this series have been studied. The drained water content of fabric and the solution isotherms and diffusion constants of water vapor into untreated and modified wools have been measured. Most of the treated wool fabrics showed considerable decreases in the drained water contents compared with the untreated wool. However, the degree of improvement depended markedly on the conditions of modification, particularly with the styrene grafted materials. In some cases values close to those of a comparable polypropylene fabric were found. The sorption isotherms also showed that the modifications reduced, substantially in some cases, the regains even when calculated on the wool content only. The diffusion constants were difficult to measure because of the heats of sorption causing temperature changes during the sorption; however, at lower regains this effect could be corrected. It was found that both the direct chemical modification and the grafted wools showed a diffusion behavior which was more characteristic of hydrophobic materials in that the diffusion constants tended to decrease with increasing concentration. At low humidities the diffusion constants were larger than in the untreated wool, but at higher humidities lower diffusivities were found with the modified wools.
Aging of SBR. II
Authors: Bevilacqua E. M. 
Published: April 2003

AbstractComparison of aging of a sulfur vulcanizate with a control having stable crosslinks, shows that oxygen affects reactions of the crosslink as well as of the hydrocarbon. Crosslink scission is inhibited. Results are in agreement with an earlier Suggestion that new crosslinking is enhanced by oxygen, although less than observed for natural rubber. This may be an effect of carbon black and amine antioxidants present in the vulcanizates.
A simple theory of filler reinforcement in elastomers subjected to shear
Authors: Zorll Ulrich 
Published: April 2003

AbstractThe effects of a filler in an elastomer can be described by means of a theory based on a simple model in which the filler particles are assumed to be of uniform size, of cubic shape, and dispersed in such a manner as to occupy the points of a cubic space lattice. For the case of shear deformation, simple relations can be derived for the increase in the storage modulus G' and the loss modulus, G″ of the bulk material with an increase in filler content. Furthermore, the theory predicts the temperature shift of two points which can be easily determined experimentally: the inflection point of G' and the maximum of G″.
Practical evaluation of the [η]–M relationship
Authors: Van Krevelen D. W. , Hoftyzer P. J. 
Published: April 2003

AbstractThe Mark‐Houwink equation for the relationship between the intrinsic viscosity of a polymer Solution and the molecular weight can be expressed in the more general form: [η] = 32Kθ(M/1000)a, where the constant Kθ has a theoretical meaning and the constant a is approximately equal to 0.7.
The sward number and mechanical properties of plastics
Authors: Roberts J. , Steel M. A. 
Published: April 2003

AbstractA Sward rocker tester is used to obtain the Sward number for glass, mild steel, copper, poly(methyl methacrylate), polyethylene of various densities, and natural rubber. A relationship between the number and mechnical properties is investigated. It is shown that with metals and glass the number is essentially a frictional factor. With plastics and rubber it is a true hardness factor, involving dynamic Young's modulus, Poisson's ratio, and damping capacity. The aim of the investigation is to encourage the development of the Sward test as a nondestructive quality test for plastics.
Molecular structure and some related properties of polyethylene stretched in the amorphous and crystalline states
Authors: Chu Hyong‐Dong , Kitamaru Ryozo , Tsuji Waichiro 
Published: April 2003

AbstractThe molecular orientation of stretched polyethylene has been estimated separately for the crystalline and amorphous phases by using x‐ray and birefringence techniques. It is confirmed that if a hightly crosslinked polyethylene is highly stretched rapidly in the perfectly molten state and cooled to room temperature, a fibrous structure comprised of highly oriented crystallites and almost unoriented relaxed amorphous chains is produced. Some properties such as dynamic mechanical properties and thermodynamic property are discussed in relation to the molecular structure.
Tensile recoveries of cotton modified with and without crosslinks
Authors: Weiss Louis C. , Frick J. G. , McSherry Wilbur F. , Cannizzaro Anna M. 
Published: April 2003

AbstractWhen effect of the substrate is nullified, resiliency can be defined as a function of strain, time, and humidity. Determination of improvement in the immediate, or rapid, tensile recovery readily delineates differences due to chemical modifications. Delayed recovery is usually less improved than immediate. Crosslinking cotton with dimethylolethyleneurea (DMEU) increases tensile strain recovery as the number of crosslinks increase, reduces dependency of recovery upon external strain, and produces maximum recovery at about 65% R.H. Noncrosslinking treatments produce limited increases in tensile strain recovery. Measurements on yarns crosslinked with DMEU and then hydrolyzed indicate that incalculably few residual links may contribute to tensile recovery. N‐Methylol‐N'‐methylethyleneurea treated cotton displays physical blocking and water swelling which aid recovery. Oleoyl chloride esterified cellulose has tensile recovery probably due to molecular entanglements. Its delayed or viscoelastic recovery is the most improved with immediate recovery being the least improved. The higher the moisture regain, the greater tensile modulus reduction under wet conditions. Crosslinking with DMEU under dry conditions lessens this reduction in modulus. Improvements in the tensile recovery of strain and energy, for all samples and with varied conditions of humidity and strain, correspond linearly with unit slope.
Crystallinity index of poly(ethylene terephthalate) by x‐ray diffractometry and differential scanning calorimetry
Authors: Wakelyn N. T. , Young P. R. 
Published: April 2003

AbstractThe crystallinity of a variety of poly(ethylene terephthalate) (PET) specimens, produced by thermal annealing, has been measured by three x‐ray diffractometric index methods and by an index method for differential scanning calorimetric data. The measurement procedures are termed indices since they involve various methods of ranking specimens in a relative manner between maximum and minimum crystallinity standards. Statistically different index values are determined by the various physical methods and procedures of calculation for many types of specimens. The integral index method, which utilizes x‐ray diffractometric data, corresponds in a more precise manner to the calorimetric index than to the other two x‐ray methods, for the cases in which oriented film is annealed in a vacuum oven and is subject to a continuous pumping environment. This treatment also produces a threefold increase in number‐average molecular weight of PET film. Annealing in sealed ampules, Mn constant, produces substantially the same results for all three x‐ray methods but different results for the calorimetric procedure. A relatively simple two‐point procedure yields virtually the same trend as the more complicated indicial methods.