bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photodegradative wavelength dependence of thermally resistant organic polymers
Authors: Johnson L. D. , Tincher W. C. , Bach H. C. 
Published: April 2003

AbstractThe wavelength dependence of photodegradation of three “high temperature” aromatic polyamide polymers has been very accurately determined by means of a fast grating spectrograph used in conjunction with a high pressure xenon arc. One of these polymers, the poly‐(isophthalamide) of 4,4′‐bis(p‐aminophenyl)‐2,2′bithiazole, was found to be degraded significantly by visible light, especially that of 4140 Å, wavelength. Both the poly‐terephthalamide of 1,3‐bis(3‐aminobenzamide) benzene and Du Pont Nomex, also an aromatic polyamide, were damaged primarily by radiation in the near ultraviolet region. Degradation band maxima for these polymers were observed at 3700 Å, and 3600 Å, respectively. All three thermally resistant polymers were thus found to be degraded by light of much longer wavelength than that which is harmful to other common polymers.
Prediction of mechanical properties of polymers. Tensile strength of glass‐reinforced plastics
Authors: McAbee Elise , Levi David W. 
Published: April 2003

AbstractTensile strength data at high and low rates of loading were obtained for a glass‐reinforced polyester and a glass‐reinforced epoxy. Analysis of the data by a rate method indicated that such a method may be used to predict behavior of polymers from limited test data.
The measurement of charge response of powders exposed to ion bombardment
Authors: Zabel Lowell W. , Estcourt Allan R. 
Published: April 2003

AbstractA system has been designed and developed to subject a sample of powder on a grounded metal plate to charging by ion bombardment and to measure the charge accepted by the sample. Observation of the charge decay from the sample was also possible. A method of sample preparation was evolved which made it possible to obtain samples of known particle size and number of particles. The sensitivity of measurement and the noise levels were investigated and found to be acceptable. Calibration tests were made to determine the validity of the proposed equation relating the measured voltage, circuit capacitances, and the ratio of probe height to net charge location. It was found that for a wide range of values of the ratio of probe height to particle diameter, the linear equation was a good description of the process and could be used to accurately determine the charge on a sample. Some measurements were made on typical powders to illustrate the feasibility of the method and equipment to characterize variable charging properties.
A study of the surface‐catalyzed polymerization of ethylene on chromic oxide–silica–alumina catalysts
Authors: Whitaker H. L. , Wills G. B. 
Published: April 2003

AbstractThis investigation was an exploratory study of the phenomena associated with the polymerization of ethylene on a chromic oxide–silica–alumina catalyst. The polymerization was carried out in a batch reactor fed on demand at 500 psi gage and at 135°C. The catalyst was 3% chromic oxide on an 87% silica–13% alumina support, activated at 450°C for 5.25 hr in dry air. The catalyst particles were found to reduce in size during the polymerization. The particles decreased in size from 18/20 mesh to an average diameter of 9.6 μ. This reduction in particle size was found to cease at a yield of 40.0 g per gram of catalyst. By determining the monomer reaction rate versus time, the catalyst activity was found to change greatly during the polymerization. The activity increased to a maximum, then decreased. The period of increasing catalyst activity corresponded to the period of catalyst particle size reduction. The period of decreasing activity was considered to be due to the build‐up of a polymer film diffusion layer and true catalyst deactivation. The molecular weight distributions for a series of samples from each polymerization test were determined on gel permeation chromatograph. These distributions for each test were characterized by an increase in the high molecular weight tail as the yield increased, while the peak position and low molecular weight end remained essentially constant.
Urethanes. I. Organometallic catalysis of the reaction of alcohols with isocyanates
Authors: Abbate F. William , Ulrich Henri 
Published: April 2003

AbstractThe catalysis of the reaction of n‐butyl alcohol with isocyanates, using organometallic derivatives of lead, tin, and mercury, has been investigated. The rate of the reaction was measured by following the disappearance of the isocyanate absorption in the infrared. Phenyl, n‐butyl, and cyclohexyl isocyanate were chosen to represent typical aromatic primary and secondary aliphatic isocyanates. Within the same series of catalysts, RnMOAc, the catalytic effect decreases in the order RHg > R3Sn > R3Pb; and in all cases R = aryl > R = alkyl. The electronic effects of substituents on the aryl moiety are not pronounced. Changes in X of RnMX greatly affect the catalytic activity. The mechanism of organometallic catalysis of the alcohol‐isocyanate reaction occurs via a template‐type mechanism whereby the catalyst acts to complex both reactants in a catalyst phase allowing the reaction to occur with greater facility.
Thermal decomposition of Cu(II)‐bis(8‐hydroxy‐5‐quinolyl)methane coordination polymer
Authors: Brown James E. , Tryon Max , Horowitz Emanuel 
Published: April 2003

AbstractThe volatile products formed when the coordination polymer of copper(II) and bis‐(8‐hydroxy‐5‐quinolyl)methane was heated in vacuum at elevated preselected temperatures were examined. The amount of weight loss at each temperature was determined with a recording thermal balance at each fixed temperature. Infrared spectrophotometry was used to aid in the identification of the major volatile component. A sample was pyrolyzed directly into the mass spectrometer. The results show that the volatile product is for the most part the organic ligand bis(8‐hydroxy‐5‐quinolyl)methane and not derivatives of the copper complex or fragments of the ligand. The mechanism for the decomposition previously proposed is supported.
Influence of structure of cyclic urea derivatives on their reactivities with cotton
Authors: Jung H. Z. , Benerito R. R. , Gonzales E. J. , Berni R. J. 
Published: April 2003

AbstractThe structure of the cyclic urea influenced the rate of reaction with cotton cellulose and the mechanism by which reaction occurred. Reaction of N, N′‐dimethylolethylene‐urea (DMEU) and N, N′‐dimethylolpropyleneurea (DMPU) with cellulose in presence of inorganic salt catalysts proceeded through methylol hydroxyls and at the same rate; but reaction mechanism differed. With DMEU, N → metal ion coordination occurred and SN2 mechanism prevailed. With DMPU, O → metal ion coordination resulted.Reaction of dihydroxyethylene urea (DHEU), N, N′‐dimethyldihydroxyethyleneurea (DMeDHEU), and N, N′‐dimethyloldihydroxyethyleneurea (DMDHEU) with cotton cellulose proceeded through ring hydroxyls with the formation of a carbonium ion, indicating an SN1 mechanism. The much faster rate of reaction with DMeDHEU than with DHEU was attributed to the more electronegative environment of its ring hydroxyl, while the much slower rate of reaction of DMDHEU was attributed to hydrogen bonding between its methylol and ring hydroxyls.
Shear properties of polystyrenes in the transition region
Authors: Burge David E. 
Published: April 2003

AbstractShear properties of commercially available polystyrenes with narrow molecular weight distribution have been measured in the transition region from 100°C to 150°C and over a frequency range from 50 Hz to 1000 Hz. The effect of molecular weight or shear properties is established with four polymers ranging in molecular weight from 20,000 to 860,000. A broad, bimodal distribution is also studied. The properties of these polymers, with two different diluents added, illustrate the rather marked qualitative difference in effects caused by diluents.
Thermal degradation of polymers. Part III. Vacuum pyrolysis of poly(m‐aminostyrene); the products volatile at pyrolysis temperature which are liquid or gaseous at room temperature
Authors: Still R. H. , Jones P. B. 
Published: April 2003

AbstractThe products obtained on degradation of poly(m‐aminostyrene) in vacuo are described. The effect of molecular weight and pyrolysis temperature are discussed and the behavior of poly(m‐aminostyrene) compared with that of polystyrene. Quantitative analytical methods using ultra‐violet spectroscopy and gas liquid chromatography are described for m‐aminostyrene and m‐toluidine. The possible mechanisms of degradation to yield the products are discussed.
Crazing, yielding, and fracture of polymers. I. Ductile brittle transition in polycarbonate
Authors: Legrand D. G. 
Published: April 2003

AbstractMost thermoplastics far below their glass transition give a brittle fracture when de‐formed in uniaxial tension. Bisphenol‐A polycarbonates are an exception and deform in a ductile manner. However, it has been observed in Izod impact studies of notched samples that the mode of failure changes from a ductile to a brittle fracture on annealing samples below Tg. It has been found that, when notched samples are stressed, a Griffith type flaw is formed under the notch. The criterion for the ductile brittle transition is evaluated in terms of σG (the stress required to propagate the Griffith flaw), and σy, the yield stress for the polymer. It has been found that the density and yield stress for the samples annealed at various temperatures are dependent upon previous thermal history and in particular on the molecular weíAght. On the basis of these measurements, it is concluded that many of the so‐called anomalous effects observed with polycarbonate can be explained.
Polyacrylic desalination membranes. I. Synthesis and characterization
Authors: Hoffman Allan S. , Modell Michael , Pan Peter 
Published: April 2003

AbstractA new class of desalination membranes has been developed. The membranes were prepared by polymerizing mixtures of two hydrophilic monomers (N‐methyloacrylamide and acrylic acid), a hydrophobic monomer (ethyl acrylate) and a hydrophobic crosslinking monomer (trimethylol propane trimethacrylate) followed by heat treatment. The membranes were homogeneous, averaging about 6 mils in thickness. They were characterized by measuring water contents and salt distribution coefficients using an immersion technique. The fractional water contents in the membranes varied between 0.16 and 0.44 as the molal salt distribution coefficients increased from ca. 0.22 to 0.43. Increasing contents of the hydrophobic monomer and/or crosslinking monomer led to decreased water and salt contents, as expected. A model is postulated in which the water is assumed to be distributed within the polymer in two forms: (1) as primary water, hydrogen‐bonded with hydrophilic polymer groups, and (2) secondary water, imbibed with salt from the external solution into hydrophilic regions or defects within the polymer matrix. It was found that primary water content was approximately constant for all compositions and varied between ca. 2–3 moles of primary water/mole of hydrophilic monomer in the membrane.
Quantitative study of the annealing of poly(vinyl chloride) near the glass transition
Authors: Foltz Carl R. , McKinney Paul V. 
Published: April 2003

AbstractPoly(vinyl chloride) displays a normal DSC of DTA curve for the glass transition when quenched from above its Tg. However if cooled slowly or annealed near the glass transition temperature, a peak appears on the DSC or DTA curve at the Tg. In this paper quantitative studies of the time and temperature effects on the production of this endothermal peak during the annealing of PVC homopolymer and an acetate copolymer are presented. The phenomenon conforms to the Williams, Landell, and Ferry equation for the relaxation of polymer chains, the rate of the peak formation becoming negligible at more than 50°C below Tg. The energy difference between the quenched and annealed forms is small. For a PVC homopolymer annealed 2 hr at 68°C, which is Tg −10°C, the difference is 0.25 cal/g. For a 13% acetate copolymer of PVC similarly annealed, the difference is 0.36 cal/g. The measured rates of the process give a calculated activation energy of 13–14 kcal/mole for PVC homopolymer and copolymer. This appearance of a peak on the Tg curve for a polymer when annealed near the glass temperature appears to be a general phenomenon.
Chemically crosslinked polyethylene: Modulus‐temperature relations and heat stability
Authors: Narkis M. , Tobolsky A. V. 
Published: April 2003

AbstractThe influence of MT black concentration on the shear modulus of low‐density crosslinked polyethylene can be approximated by the Guth–Gold equation, at temperatures below the crystalline melting zone. Above the melting zone shear modulus does not depend practically on the carbon black level. At high temperatures both degradation and crosslinking reactions are taking place. The variation of the shear modulus with temperature due to these reactions is shown for various carbon black loadings. A preliminary chemical stress‐relaxation study at 250°C is presented.
Radiation chemical studies of protein reactions: Radiation dose and optical rotation
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractWhen protein was irradiated by gamma rays from a cobalt 60 sources, an activated state on the position of the groups in the vicinity of the asymmetric carbon atoms in the protein molecule was caused. An empirical equation for the change in optical rotation was obtained, and the phenomena were explained on the basis of the molecular mechanism. The general equation for the change in optical rotation is given by [α] = (b + a log R) (1 − e−kt), where [α] is the specific rotation of the solution, R is the gamma radiation dose, t is time, and a, b, and k are adjustable constants.
Cooking schedule of alkyd resin preparation. I. Effect of cooking schedule on viscosity‐molecular weight relationship
Authors: Nagata Takumi 
Published: April 2003

AbstractThe two constants in the equation log η = A + C′ M̄n1/2 (η is the viscosity of molten alkyd and M̄n the number average molecular weight) were determined at 110°C for two kinds of alkyd resin prepared with the same formulation but with different cooking schedules. It was found that the magnitude of the slope C′ was larger for the alkyd which was prepared by raising the reaction temperature directly up to 230°C, in comparison with that of the alkyd which was prepared by maintaining the temperature at 170°C for an hour and then raising it up to 230°C.Measurements of η and M̄n were carried out until the gelation occurred. Both upward and downward breaks were observed in log η vs. M̄n1/2 plot. Based on these viscometric data, the gel point mechanism was discussed. Disagreements between the molecular weight observed and that calculated from the Flory's theoretical equation became more remarkable as the esterification proceeded. This suggested that a large extent of intraesterification reaction is taking place in alkyd synthesis.
Load–compression behavior of flexible foams
Authors: Rusch K. C. 
Published: April 2003

AbstractThe load–compression behavior of a foam reflects its geometric structure and the physical properties of the matrix polymer. Quantitative relations between these parameters have been established in the present study. Based on both theoretical analyses and experimental data obtained on a flexible polyurethane foam, it is shown that the compressive stress can be factored into the product of two terms: (1) a dimensionless function of the compressive strain, ψ(ε), calculated from experimental load–compression data and reflecting the buckling of the foam matrix; and (2) a factor, εEf, where Ef is the apparent Young's modulus of the foam (which is a function primarily of the modulus of the base polymer E0 and of the volume fraction of polymer, φ). Thus the compressive stress behavior of a foamed polymer is determined by E0, φ, and the matrix geometry, the latter described by the function ψ(ε). Using these established relations, it now is possible to delineate precisely the structural features a foam must possess—density, cell shape and size distribution, and modulus of the base polymer—to meet a given load–compression specification.
The manganic hydroxide–hydrazine hydrate system as an initiator of vinyl polymerization
Authors: Bond Joan , Longbottom H. M. 
Published: April 2003

AbstractThe reaction of hydrazine hydrate with manganic hydroxide and its application to the solution polymerization of methyl methacrylate has been studied. The kinetic evidence suggests that the hydrazine and the monomer are both adsorbed on the surface of the manganic hydroxide sol and that the decomposition of the hydrazine and the polymerization of the methyl methacrylate follow zero‐order kinetics. The rate of polymerization increases slowly with increasing temperature, the activation energy for the polymerization being 4.9 ± 0.2 kcal/mole.
An investigation of factors relating to the exudation of polyester plasticizers from poly(vinyl chloride)
Authors: Rushton Brian M. , Salomons Norman S. 
Published: April 2003

AbstractPoly(vinyl chloride) (PVC) was plasticized with a given polyester. The resulting exudate under humid conditions was qualitatively analyzed by GPC and GLC. The exudate was found to have a greater concentration of low molecular weight species than the origional polyester. Further, a much higher hydroxyl group concentration was present. The described polyester was also fractionated and characterization studies were performed. The relative migratory aptitude in PVC of these moieties was studied under humied conditions. The fraction with the greatest concentration of low molecular weight species and the highest hydroxyl concentration was exuded first.
Estimation of Mw from dilute solution viscosity
Authors: Rudin A. , Bennett G. W. , McLaren J. R. 
Published: April 2003

AbstractThe viscosity‐average molecular weight, Mv, of a polymer is given operationally through its limiting viscosity number [η] and the Mark‐Houwink equation [η] = KMvα, where K and α are empirical constants. If [η] is measured under different conditions, α and Mv will vary for the same sample. Mvα is the α‐order moment about the origin of the differential weight distribution of the polymer. Practically, the results of a series of Mv measurements on the same polymer are equivalent to a cluster of fractional moments of the weight distribution, with orders between 0.55 and 0.80. It is shown that the first moment of this distribution, Mw, may be estimated reliably by a straightline plot of Mv against α‐extrapolated to α equals 1. This simple expedient is effective although there are probably no molecular weight distributions in which the relation is strictly linear and there are no mathematical distributions for which the αth root of the αth moment is a linear function of α for all α. The deviation from linearity is small enough, however, that the real curve can be represented by a straight line over a short range of α. Thus, Mw can be measured accurately, but Mn, Mz, or the breadth of the distribution is not accessible by this method. Experimental and literature examples show that the precision of Mw estimated by this method compares well with that of primary methods for measuring this molecular weight average. If a linear relationship is observed with reliable α values, this appears to be a sufficient condition for estimation of a valid Mw.
Properties of blends containing petroleum jelly and 4‐methyl‐pentene‐1 (TPX‐RT‐D30)
Authors: McCann J. P. , Geacintov C. 
Published: April 2003

AbstractThe properties of 4‐methyl‐pentene‐1 polymer (TPX‐RT‐D30) were altered by blending petroleum jelly (P.J.) with the polymer. The polymer was blended with up to 40% by weight P. J. The plasticization of the polymer by the P. J. apparently allows high molecular weight fractions of the polymer to crystallize and influences the crystalline size and perfection. Tensile properties of the blends showed both a break and yield value in all ratios as compared to only a break value for the pure polymer. Breaking strength ranged from 4000 psi for the polymer to 1000 psi at 40% P. J. The samples had a “necking down” effect at 10% P. J. Modulus decreased from 1.8 × 104 (literature value 2.1 × 105) to 2.3 × 104 at 40% P. J. Brittle point values varied from above room temperature to 5°C at 40% P. J. The Vicat softening point ranged from 181°C for the polymer to 87°C at 40% P. J. Differential thermal analysis (Stone) showed a melting point depression from 235°C to 218°C at 40% P. J.
Thermal conductivity, specific heat, and dynamic mechanical behavior of diglycidyl ether of bisphenol a cured with m‐phenylenediamine
Authors: Kreahling R. P. , Kline D. E. 
Published: April 2003

AbstractThe thermal conductivity, specific heat, and dynamic mechanical behavior of an epoxide system have been investigated over a relatively wide temperature range. Effects of nonstoichiometric amine concentrations and postcure heat treatments were included in the study. The thermal conductivity behavior was found to be related to the extent of cure of the poxy system, but in general the results were typical of an amorphous polymer. Calorimetric determinations were used to study the curing reaction and the glasslike transition temperature for the various systems. Dynamic mechanical results were employed to delinearte the various internal relaxations of the cured materials and in some instances to permit correlation of relaxations with the thermal conductivity and the specific heat results. From comparison of present results to those of a previous paper, the activation energy for the relaxation process occurring near 270°K has been estimated to be 16 kcal/mole.
Determination of the extent of reaction for the system carboxyl‐terminated polybutadiene‐epoxide beyond the gel point by infrared spectroscopy
Authors: Strecker R. A. H. 
Published: April 2003

AbstractCuring reactions were investigated after the gel point, using infrared transmittance and reflection spectrophotometric techniques. In the system carboxyl‐terminated polybutadiene (CTPB)/Epon X801 or Epotuf STF‐6, catalyzed with Fe(III)‐acetyl‐acetonate (FeAA), at an equivalent ratio of carboxyl to epoxide groups, the final extent of reaction of COOH groups was found to be between 64% and 77% for eight CTPB samples. Increasing the ratio of epoxide to carboxyl groups (up to 1.6) resulted in an increase in the conversion, but the complete reaction of COOH groups could not be accomplished. The final extent of reaction also depends upon the functionality of the crosslinking agent. The lower the functionality of the epoxide, the higher the conversion of COOH groups. The use of chromium naphthenate as a catalyst for epoxide–COOH reactions gave higher conversions than FeAA. This result is related to side reactions catalyzed by the chromium naphthenate. The change in mechanical properties and the change in extent of reaction were followed simultaneously; it was found that no further development of mechanical properties occurred when the curing reaction between COOH and epoxide groups had ceased.