bluuebunny/crossref_metadata_2025_split huggingface dataset:
Peel strength of polyurethanes from oxypropylene polyols II. Effect of additives, isocyanate structure, and other factors
Authors: Reegen S. L. 
Published: April 2003

AbstractThe study of factors influencing the adhesion properties of polyurethane coatings to aluminum has been continued. The data indicate that the addition of additives to polyurethanes can affect their peel strengths. The addition of epoxy resins, chlorinated paraffins, or sulfonamide–formaldehyde resins results in increased peel strengths; the use of a mixture of fatty acids resulted in reduced values. The isocyanate structure can also play an important role; those producing more flexible films (such as m‐xylylene di‐isocyanate) result in higher peel strength values. Other factors found to be of importance included the concentration of aromatic and aliphatic groups, the type of solvent used in casting the films, the crystallinity of the polyether glycols and the presence or absence of certain substituents, such as fluorine, in the polyurethane chain. Tracer studies have indicated that the mechanism of adhesion failure involves the breaking of the polymer‐polymer as well as polymer–substrate bonds.
Method of calculating molecular weight distribution function from gel permeation chromatograms. II. Evaluation of the method by experiments
Authors: Tung L. H. , Moore J. C. , Knight G. W. 
Published: April 2003

AbstractThe calculation scheme for correcting the broadening effect due to imperfect resolution on gel permeation chromatograms was compared with actual performances of a gel permeation chromatography (GPC) column. The experiment consisted of fractioanting a high‐density polyethylene on a GPC unit and then determining the chromatograms of the cuts collected. The chromatograms of the cuts were also computed from the starting chromatogram using experimentally determined resolution factors. The degree of agreement between the calculated and experimental chromatograms of the cuts shows convincingly that the previously proposed calculation scheme is satisfactory for the treatment of GPC data.
Method of calculating molecular weight distribution function from gel permeation chromatograms. III. Application of the method
Authors: Tung L. H. 
Published: April 2003

AbstractSix examples were used to illustrate the application of a previously reported method of calculating molecular weight distribution from gel permeation chromatograms. These examples show that the correction for the imperfect resolution of the GPC column is important when the distribution is narrow but minor when the distribution is broad. They show also that the variation of the resolution factor h, defined previously, with eluent volume can be neglected in the calculation. When the chromatograms are very narrow in distribution or when they are complex some difficulties are encountered. The two computer programs written to implement the previously described numerical calculations are shown to be adequate for these difficult cases but there are also limitations.
Fractional turbidimetric analysis of the molar substitution of hydroxyethyl cellulose
Authors: Muller Thomas E. , Alexander W. J. 
Published: April 2003

AbstractHigh quality packaging films from hydroxyethyl cellulose of low degree of substitution (DS) are being produced commercially in this country and abroad. Increasing demand for this and a variety of other applications requires a rapid and simple production control method for determining hydroxyethyl substitution of cellulose. None of the known analytical methods fulfills these requirements. The present paper describes a method which is based on the relationship between the solubility and the molar hydroxyethyl substitution of hydroxyethyl cellulose. A washed and dried sample of hydroxyethyl cellulose is dissolved in 7% aqueous sodium hydroxide. Methyl alcohol, a nonsolvent, is used to precipitate a fraction of the sample. The turbidity of the equilibrium system is determined and optical density readings are related to molar substitution. The method is most useful in low DS ranges of 2–8% EtO but is susceptile to broader application through adjustment of the composition of the solvent–nonsolvent mixture. Relatively large variations in DP can be tolerated. The molar substitution level of an hydroxyethyl cellulose sample can be obtained in 40 min. by this method, making it a practical production control technique.
Spontaneous polymerization of acetaldehyde to polyacetaldehyde at close to dry‐ice temperature
Authors: Georgieff K. K. 
Published: April 2003

AbstractPolyacetaldehyde has been prepared in the liquid and vapor phases without the addition of a catalyst by storing undiluted acetaldehyde in the dark at a temperature of −68°C. for 3–6 months. When acetaldehyde was stored in an untreated Pyrex flask, 20% high polymer, 55% paraldehyde, and less than 1% metaldehyde were obtained. The polymer was an elastomeric solid with a low to moderate degree of crystallinity and an intrinsic viscosity of 0.63 dl./g. When the sample was stored in a Pyrex flask which had been pretreated with alcoholic potassium hydroxide followed by a water wash, 16–17% high polymer and 6% paraldehyde were obtained. Some polymer formed on the unwetted glass above the liquid. It was slightly elastic, at least moderately crystalline, and had an intrinsic viscosity of 1.6 dl./g. It is suggested that the formation of this polymer was initiated by basic active sites on the Pyrex surface which acted by an anionic mechanism. Also some polymer was formed in the liquid phase. This material was an amorphous, highly viscous oil with an intrinsic viscosity of 0.28 dl./g. It was probably formed by a cationic mechanism. It is also suggested that a relatively small amount of paraldehyde was formed in the alkali‐treated flask in the liquid phase due to neutralization of the Brønsted acid sites and possibly some of the Lewis acid sites on the surface of the flask.
Infrared spectroscopical investigation of cotton subjected to swelling and deswelling treatments
Authors: Åsnes Harald , Wickman Bengt O. 
Published: April 2003

AbstractThe setting of textiles made from cellulosic materials can be done with swelling and deswelling processes. Standard cotton fibers, purified by extraction, have been set in sodium hydroxide solutions with and without additions of thiocyanate salts. Treatments have also been done in zinc chloride and calcium thiocyanate and in a solution of potassium hydroxide in a mixture of butanol and kerosene. After rinsing and drying of the cotton samples, KBr pellets for infrared investigations were produced. Deuteration of the fiber sample for investigation was made in a special apparatus. Single and differential infrared diagrams have been run with and without previous deuteration of the set cotton samples. The infrared maximum of absorption of the OH band changes as a result of the setting treatment. The infrared diagrams show that the setting treatment in alkaline solution gives a broadening of the OH band towards higher and lower wavelengths, which indicates a transfer of the hydrogen bonding energy both to higher and lower energies. The diagrams from the deuterated samples indicate that the strong hydrogen bonds resulting from the setting treatment are partly resistant to deuteration. The results are discussed on the basis of setting and setting reactions.
Fracture toughness of an epoxy system
Authors: Mostovoy S. , Ripling E. J. 
Published: April 2003

AbstractThe fracture toughness of epoxy used in the bulk and adhesive form was measured by a previously developed technique. The uniform double cantilever‐beam specimen, which was described earlier, was modified to a tapered beam, which simplified the experimental procedure and calculations for obtaining toughness measurements. by varying the ratio of hardener to resin and post‐cure temperature on a single epoxy system (DER 332‐TEPA), it was found that the toughness of the epoxy used in either bulk or bond form varied by a factor of approximately five. A particular combination of composition and post‐curing temperature generally yielded higher toughness in the bulk than in the bond form. This was not always the case, however. At high post‐cure temperatures, where the bonds were very tough, their toughness exceeded that of the bulk material. Hence, it does not appear possible to predict joint toughness from bulk toughness measurements. The toughness of joints was found to be a single‐valued function of tensile modulus. For the bulk material, on the other hand, the toughness obtained on the epoxy having a specific modulus depended on the combination of composition and post‐cure temperature. Joint toughness for any combination of composition and post‐cure temperature depended only on the cracking rate. If the epoxy was the type that caused cracks to jump rapidly, the epoxy was tough and vice versa. For a particular epoxy system, toughness was increased by driving the crack at an increasing rate.
Crystallization from the glassy state
Authors: Collier John R. , Baer Eric 
Published: April 2003

AbstractIsothermal crystallization of poly[3,3‐bis(chloromethyl)oxacyclobutane] and poly‐(ethylene terephthalate) from the quenched glassy state gave small lamellae approximately 1000–2000 A. in lateral dimension with a constant thickness of about 100 A. The maximum primary nuclei density for crystallization slightly above the glass transition temperature, Tg, was 1010 greater than frequently observed during spherulitic growth from the melt. Since the lamellae grow at a linear rate, the crystallization process could be described by the Avrami theory for two‐dimensional growth with a constant nuclei density. By assuming that crystallization near Tg is diffusion‐controlled, bulk crystallization rate data were analyzed to obtain self‐diffusion coefficients whose activation energies were similar to reported values for other polymers.
Pressure–volume–temperature behavior of nylon 610
Authors: Haug William A. , Griskey Richard G. 
Published: April 2003

AbstractEquilibrium pressure–volume–temperature behavior in both the solid and molten regions was determine for nylon 610. Data were measured with a compressibility device capable of obtaining precise and accurate data. Residual curve treatment showed that the data were true equilibrium data. A volume extrapolated to 2419 atm. at room temperature from the present data compared favorably to the sole literature value reported by Bridgman. The data of this work showed the existence of what appears to be a second‐order transition point for nylon 610. This point ranged from 140°C. at 232 atm. to about 170°C. at 1855 atm. The Spencer‐Gilmore equation was fitted to the data of this study.
Comparison of tensile stress relaxation behavior of graft copolymer of poly(vinyl acetate) with styrene and mechanical mixture of poly(vinyl acetate) with polystyrene
Authors: Soen Toshiichi , Horino Tzuneo , Ogawa Yasuo , Kyuma Koichi , Kawai Hiromichi 
Published: April 2003

AbstractAs one in a series of studies relating the rheological behavior of mechanical mixtures of two polymer components to the degree of mixing, the tensile stress relaxation behavior of a graft copolymer of poly(vinyl acetate) with styrene, obtained by 60Co γ‐irradiation of poly(vinyl acetate) in styrene solution and extraction of homopolymers, was investigated as a function of the fraction of styrene component and compared with that of a mechanical mixture of poly(vinyl acetate) with polystyrene, one of the typical combinations of incompatible components. The results obtained may classify the graft copolymer as a sort of mechanical mixture giving stable mixing even for incompatible components.
Proton magnetic resonance investigation of the orientation of hydrogen bonds in nylon 66, poly(vinyl alcohol), and cotton yarn
Authors: Gupta Ramdas P. 
Published: April 2003

AbstractDirectional dependence of the PMR‐narrow‐band in oriented fibers of nylon 66, poly(vinyl alcohol), and cotton has been investigated to study the orientation of hydrogen bonds in the unit cell. Filaments of oriented fibers were conditioned to 75% relative humidity, then aligned together axially and packed in a teflon tube. The teflon tube was suspended in the NMR probe in such a manner that the fiber axis was horizontal and could be rotated to a desired angle with respect to the magnetic field. Variation of the narrow‐band line width as a function of the angle between the fiber axis and the magnetic field‐direction shows a minimum at 0° orientation for nylon 66 and PVA, but in the case of cotton it shows a minimum at about 80° orientation. This indicates that in the case of nylon 66 and PVA, hydrogen bonds are oriented nearly prependicular to the chain axis. This would suggest that nylon 66 and PVA have interchain hydrogen bonding, but the hydrogen bonds contributing to directional dependence, in the case of cotton fiber, are intrachain. The interchain hydrogen bonds between the lateral chains, if they exist, must be random and, therefore, do not contribute to directional dependence. The interchain H bonds between central and corner chains are probably oriented in such a way that the horizontal component of p–p vectors have nearly the same orientation in the unit cell as the p–p vectors of the intrachain hydrogen bonds.
Abrasion characteristics of polypropylene yarns
Authors: Ross Stanley E. , Wolf Harold W. 
Published: April 2003

AbstractThe abrasion characteristics of low‐twist polypropylene multi‐filament yarns free of surface lubricants were determined by rubbing the yarns against each other by using a reciprocating action device at a frequency of 60 cycles/min. It was found that the abrasion behavior of the yarns varies over a wide range and is related to such fundamental properties as the polymer and fiber molecular weight, undrawn fiber orientation and crystalline structure, drawn fiber properties, and elevated temperature post‐treatment. It was also found that presence of surface lubricants could increase the number of abrasion cycles to failure by as much as a factor of 20, depending upon the particular lubricant employed. The mechanism of the process of fiber failure resulting from abrasion damage was examined and appears to be one in which the fiber rupture is preceded by a tearing and peeling back of fiber surface fragements probably initiated at flaws in the fiber surface.
Poly(vinyl chloride) thermal stability. I. Evaluation by melt rheology
Authors: Collins Edward A. , Krier Charles A. 
Published: April 2003

AbstractCapillary rheometry is used to characterize the thermal stability of poly(vinyl chloride). By isothermally extruding the polymer melt at constant shear rate, apparent viscosity–time relationships are obtained having three distinct regions: (1) obtainment of equilibrium viscosity, (2) constant viscosity, and (3) rapidly changing viscosity. During regions 2 and 3 the polymer extrudate gradually changes in color from water clear to black. These characteristic regions are related to the temperature of extrusion by Arrhenius plots. An activation energy of 40 kcal./g.‐mole was calculated for the decomposition of PVC. Infrared spectroscopy, thermal gravimetric analysis, and intrinsic viscosity experiments are used to corroborate the results of the melt flow data.
ESR study of reactions of cellulose initiated by the ceric ion method
Authors: Arthur Jett C. , Baugh Peter J. , Hinojosa Oscar 
Published: April 2003

AbstractThe ESR spectra of microcrystalline cellulose and purified cotton cellulose reacted with ceric ammonium nitrate in nitric acid were determined. The effects of the concentration of ceric ion, atmosphere, temperature, and graft copolymerization with acrylonitrile on the rates of formation and decay of radicals in the cellulose molecule were determined under both static and dynamic conditions. Under static conditions, after the desired conditions of reaction, the samples were frozen at –100 or –160°C., and then the concentration of free radicals was determined. Under dynamic conditions ceric ion solution was continuously flowed through the celluloses while these determinations were being made at 25°C. In the presence of oxygen the rate of decay of free radicals was decreased. On initiation of copolymerization reactions with acrylonitrile, there was an increase in radical concentration, then a decrease. Apparently, during graft copolymerization the radical site initially on the cellulose molecule was retained on the end of the growing polymer chain. Then additional ceric ion coordinated with the hydroxyl groups of the cellulose, leading to the formation of additional radical sites. An Arrhenius interpretation of the effect of temperature on the formation of these additional radical sites gave apparent activation energies for radical formation on cotton cellulose as 34 kcal./mole and on microcrystalline cellulose as 29 kcal./mole.
Interfacial polymerization of n‐alkyl α‐cyanoacrylate homologs
Authors: Leonard Fred , Collins John A. , Porter Harold J. 
Published: April 2003

AbstractThe n‐alkyl α‐cyanoacrylates from methyl through n‐octyl exhibit a reverse order of polymerization rate on biological substrates compared to that on water. On water, the lower homologs spread and polymerize rapidly, whereas the higher homologs spread but polymerize slowly. On biological substrates, the lower homologs do not spread or spread slightly and the higher homologs exhibit large spreadabilities and very rapid polymerization rates. Determination of the spreading coefficients for these systems by using the monomers or model compounds confirm the observed spreadabilities. It is proposed that the increased rate of polymerization of the higher homologs on biological substrates may be due to increased catalyst concentrations on these surfaces or to the solubilization of the higher homologs at the interface, making the catalyst sites more available to the monomer. The suggestion is made that if the liquid monomers spread and orient on the substrate and subsequently polymerize, the polymers will maintain the orientation. If such is the case, a technique is available for preparing stereospecific vinyl polymers which may have different spatial configurations depending on the polarity of the liquid substrate upon which they have been allowed to spread and polymerize.
Estimating elution fractionation conditions for linear polyethylene and isotactic polypropylene
Authors: See Benito , Smith Theodore G. 
Published: April 2003

AbstractA technique has been developed which provides a means for estimating polypropylene fractionation conditions in an elution column from a knowledge of the fractionation conditions used to fractionate linear polyethylene in the column and the solution behavior of both polymers in the same solvent‐nonsolvent system of varying compositions. The fusion behavior of linear polyethylene and isotactic polypropylene in mixtures of o‐di‐chlorobenzene and dimethyl phthalate of varying compositions has been studied by a differential thermal analysis (DTA) technique using concentrations similar to those in an elution fractionation column. The column temperature for fractionating each of these polymers by using o‐dichlorobenzene and dimethyl phthalate as the solvent and nonsolvent, respectively, was determined from their melting temperatures in dimethyl phthalate. On the basis of the equivalence of the fractional depression in solution temperature of each polymer in the binary liquid mixture, the composition range of solvent‐nonsolvent mixtures to be used in fractionating polypropylene was estimated from a knowledge of the polyethylene fractionation conditions together with the DTA data. Although separation depends primarily on molecular weight, the equivalence in fractional solution temperature depression provides a convenient means of correlating fractionation conditions for the polyolefins investigated.
Free volume treatment of concentrated polymer solutions
Authors: Pezzin G. , Gligo N. 
Published: April 2003

AbstractVery different concentration dependences of the viscosity of polymer solutions are predicted by the free volume treatments of Fujita and Kishimoto and of Kelly and Bueche. This latter is conveniently extended, and it is shown that it can describe a given set of experimental data over a concentration range much larger than the Fujita‐Kishimoto equations.
Effect of molecular weight on the breaking time of a glassy polymer
Authors: Kwei T. K. 
Published: April 2003

AbstractAn analysis of the dependence of the breaking time tb of a glassy polymer under constant stress on the molecular weight of the polymer is made with the use of the theories by Bueche and by Cohen and Turnbull. It is concluded that log tb is proportional to the degree of polymerization x when x is small but becomes independent of x at large values of x.
Block copolymerization of formaldehyde
Authors: Smith W. E. , Galiano F. R. , Rankin D. , Mantell G. J. 
Published: April 2003

AbstractSolubility and spectroscopic evidence are presented to support the formation of A‐B block copolymers between monomers undergoing anionic polymerization (A units) and monomeric formaldehyde (B units). Comonomers included in the study were styrene, methyl and n‐butyl methacrylate, acrylonitrile, isoprene, and N, N‐di‐n‐butylacrylamide. Similar evidence is presented on the formation of B‐A‐B copolymers between styrene and α‐methylstyrene and formaldehyde; an A‐(B‐C) random copolymer of styrene, formaldehyde, and phenyl isocyanate (C) was also prepared. Experimental details for the preparation of high‐purity, monomeric formaldehyde suitable for such work is described in some detail. It should be emphasized that this study was directed primarily toward showing the feasibility of preparing formaldehyde block copolymers; therefore, further work is needed to establish the quantitative nature of these reactions.
Mechanisms of oxidative degradation. I. Oxidation of synthetic rubbers catalyzed by metallic ions
Authors: Lee Lieng‐huang , Stacy C. L. , Engel R. G. 
Published: April 2003

AbstractThe oxidative stability of rubbers depends on the structure of the rubber and the impurities contaminating the rubber. It is known that the oxidation of natural rubber is accelerated by the presence of metallic impurities. Besides GR‐S rubber and nitrile rubber, the effects of metallic impurities on the oxidation of new rubbers, especially those introduced after the discovery of Ziegler‐Natta catalyst, have not been reported. In the first part of this paper, the theoretical background on the mechanisms of metalcatalyzed oxidation is given. Most of the early work was carried out for the oxidation of hydrocarbons in the liquid phase. The difficulties in applying the liquid‐phase results to the oxidation of high polymers in the solid phase are mentioned. The new rubbers used for this study are polyisoprene, polybutadiene, cis‐poly‐1,3‐butadiene, styrenebutadiene copolymer, butyl rubber, ethylene‐propylene terpolymer (EPT), propylene oxide rubber, polyacrylic rubber, and butadiene‐acrylonitrile rubber. The effects of stearic acid and various stearates on the oxidation of these rubbers are presented. The number of electrons transferred by the metal ion during redox reactions was found to be related to the effectiveness of the ion as a catalyst. Both the high and low oxidation states of the metal ion were shown to be active catalysts, supporting the accepted theory of metal catalysis through a hydroperoxide decomposition mechanism.
Elastomeric and mechanical properties of poly‐m‐carboranylenesiloxanes
Authors: Sperling L. H. , Cooper S. L. , Tobolsky A. V. 
Published: April 2003

AbstractA new high‐temperature elastomer, SiB‐2, has been investigated by stress relaxation, modulus‐temperature, and volume‐‐temperature techniques. SiB‐2 was found to be more stable than a related elastomer, radiation‐cured silicone rubber, having about twice as long as a chemical relaxation time at 250°C. Possible mechanisms to account for this increased stability are discussed. At low temperatures, Tg for SiB‐2 was estimated at –34°C., which compares well with Ti = −30°C. for this polymer. By comparison, SiB‐3 has Ti = −60°C., while phenyl‐modified SiB‐4 was found to have Ti = −25°C. Tm for SiB‐2 was estimated to be + 56°C.