bluuebunny/crossref_metadata_2025 huggingface dataset:
Unsymmetrical diisocyanates. II
Authors: Case L. C.
Published: April 2003

It has long been known that certain aromatic diisocyanates exhibit unequal reactivities of the two isocyanate groups. However, the degree of unsymmetry of reactivity in the previously known diisocyanates is limited. In this research, a number of structurally unsymmetrical diisocyanates were screened for unsymmetry of reactivity by reacting the diisocyanate with excess isoamyl alcohol in chlorobenzene solvent. The reaction was followed by observing the decrease of infrared absorption of the solution at 4.5 μ. A number of diisocyanates were found to have desirably high degrees of unsymmetry in reactivity. These diisocyanates, and the ratio of apparent half‐lives of reaction for the two isocyanate groups are: 2,6‐diethyl‐p‐phenylenediisocyanate, 100; 2,6‐dimethyl‐p‐phenylenediisocyanate, 80; 2‐bromo, 6‐methyl‐p‐phenylenediisocyanate, 50; 2,6‐dichloro‐p‐phenylenediisocyanate, 30; and 3,5‐diethyl‐4‐4′‐diisocyanato‐diphenylmethane (DEMDI), 49.
Thermal expansion of photomechanical materials
Authors: Colao Angelo , Becker Herbert
Published: April 2003

A quartz thermal expansion apparatus was developed to measure the thermal expansion of photomechanical plastics. Three different methods of motion measurement correlated with a maximum error of ±1% for three different models of Hysol 4290 epoxy. The thermal expansion of a 30% plasticized epoxy was determined and was found to exhibit essentially the same characteristics as the 4290 epoxy except for a shift in the temperature scale.
Unsymmetrical diisocyanates. III. The kinetics of reactions of DEMDI
Authors: Case L. C. , Li K. W.
Published: April 2003

In the previous investigation it was found that 3,5‐diethyl‐4,4'‐diisocyanatodiphenylmethane (DEMDI) exhibits a marked asymmetry in the reaction with isoamyl alcohol. Since DEMDI is potentially rather cheap, and since the unsymmetrical nature of the diisocyanate is quite advantageous in certain urethane formulations, the reactions of this diisocyanate with a series of model compounds were investigated. The model compounds were chosen so as to represent the important classes of functional groups commonly reacted with diisocyanates in the preparation of polyurethanes. The compounds used were isoamyl alcohol, 2‐octanol, water, 2,6‐diethylaniline, 1‐n‐butyl‐3‐phenylurea, and 1‐(4‐n‐butylphenyl)‐3‐(methylphenyl)‐urea. The reactions were conducted in dry diglyme solvent. The extent of reaction of the isocyanate groups was followed by reaction with excess di‐n‐butylamine and back‐titration with hydrochloric acid. Tetramethyl‐1,3‐butanediamine and dibutyltin dilaurate were used as catalysts in some runs. The results show that DEMDI has a desirably high asymmetry of reaction with alcohols or water at low temperatures. Catalysis with dibutyl dilaurate markedly increases this asymmetry. An increase in temperature generally decreases the asymmetry of DEMDI reactions, so that elevated temperatures should be avoided in prepolymer formation. The dibutyltin dilaurate is a more effective catalyst than the diamine for all of the reactions studied. The diamines are very poor catalysts for urea reactions, whereas the tin compound is quite effective.
Effects of mechanical action on the electron paramagnetic resonance of wool and silk
Authors: Windle J. J. , Wiersema A. K.
Published: April 2003

Wool fibers and cloth damaged by mechanical action such as abrading and grinding show strong EPR signals. Silk fibers after grinding also show strong EPR signals. Both wool and silk ground in a dry nitrogen atmosphere exhibit a doublet spectrum attributed to a ·CH radical on the polypeptide chain. In wool, a complex curve centered at g = 2.025 is observed. It is attributed to a CH2S· radical resulting from the rupture of the disulfide bond in the cystine residue. These radicals are stable for many months in a nitrogen atmosphere or vacuum. In dry oxygen the spectrum of the ·CH radical is transformed within a few hours from a double into a single, narrow curve, whereas the spectrum characteristic of the cystine radical disappers more slowly. In the presence of water vapor both radical species are rapidly destroyed and their spectra disappear. The mechanisms for the production of free radicals by mechanical action are believed to be direct chain rupture or localized pyrolysis, coupled with migration to specific radical traps in the protein.
Hydration and density of collagen and gelatin
Authors: Fels I. Gordon
Published: April 2003

The water sorption by adult and embryonic native and insoluble collagen was investigated, along with that of calfskin gelatin. Greater sorption was obtainable with the collagen fractions than with gelatin, but the technique could not distinguish the fractions themselves. The suggestion is made that the greater sorption by collagen over gelatin and differences in apparent wettability between the adult and embryonic insoluble collagen might be explained by the formation of helical grooves with aging. Density measurements of the collagen fractions indicate that collagen becomes more crystalline with aging. This also applied to the insoluble collagen. These results are consistent with the view that differences in collagen solubility are due to differences in molecular ordering. The density of the insoluble collagens and gelatin passes through a maximum at 3–4% sorbed water. The phenomenon is explained on the basis of water bridges comprised of a single water molecule double hydrogen bonded to closely aligned chains. A discussion is presented in this connection. A calculation based on the density yields a molecular volume of 4.32 × 10−19 cm.3 For tropocollagen. This is in agreement with the molecular dimensions and consistent with the idea that collagen is formed from an aggregation of the monomer.
Polymers as fibers
Authors: Tippetts E. A. , Zimmerman J.
Published: April 2003

The relation between polymer and fiber structure and fiber properties is discussed. The specific effects of intermolecular forces, chain stiffness, monomer unit regularity, crystallinity, crosslinking, orientation, molecular weight, and chemical composition on the important fiber properties of melting point, modulus, elasticity, or recovery from strain, tensile strength, moisture adsorption, and dyeability are discussed in some detail. An example is given to illustrate the role of today's sophisticated engineering in further controlling and modifying fiber properties.
Gas permeability apparatus for films and sheets
Authors: Huldy H. J.
Published: April 2003

An apparatus for measuring the gas permeability of films and sheet material has been developed at the Central Laboratory TNO, Delft (The Netherlands). The apparatus consists of a high vacuum unit, connected to six film holders of a new design and construction. The pressure of the gas which permeates through the film in a constant volume, is measured with the aid of McLeod manometers. The apparatus was developed for rapid, accurate measurements of materials of very low permeability, but it is also suitable for films of high permeability, but it is also suitable for films of high permeability. The range of permeabilities to be measured is between 10−7 and 10−13 cm.3 (S.T.P.)‐film thickness/cm.2‐sec.‐cm. Hg. The measuring time for the 10−13 range is about 6 hr. (for plastic laminated with aluminum) and for the 10−7 range is about 15 min. (for polyethylene). Measurements can be executed simultaneously on six heads and easily at various temperatures and relative humidities. The apparatus is suitable both for research purposes and for routine measurements in industry.
Effect of agitation and molecular weight on polymer adsorption and deflocculation
Authors: Jankovics L.
Published: April 2003

The rates of adsorption of PAM's were measured on calcium phosphate at various intensities of agitation. Vigorous mechanical stirring promotes the adsorption by degrading the floccules, thus providing new surfaces available for further adsorption of polymers. The rising parts of the rate curves correspond to the breaking up of flocs or “deflocculation” by the applied mechanical stirring. The flat portions of the curves in the high stirring time range indicate complete redispersion; no further surfaces are available for the adsorption of polymer flocculants. The effect of the intensity of agitation upon adsorption was investigated. Increasing the number of revolutions of the stirrer causes the adsorption curves to rise more sharply. This suggests that the deflocculation also becomes more rapid. At equimolar initial concentrations the rates of adsorption and deflocculation decrease with increasing molecular weight.
Dipolar solvents in polyurethane foams
Authors: Kuryla William C.
Published: April 2003

A number of catalytic solvents have been discovered for the polyurethane foaming process. These solvents include N,N‐dimethylformamide (DMF), dimethyl sulfoxide (DMSO), formamide, and a number of others. The catalytic effectiveness of a given solvent appears to be dependent on its dipole moment, water solubility, and the size or bulkiness of the groups which are attached to the carbonyl carbon or sulfur atom of the amides and sulfoxides, respectively. Steric effects play a very important role in controlling the catalytic efficiency of these solvents. A mechanism is proposed for the catalytic action of these solvents in the polyurethane reaction.
A note on the conductivity and modulus of carbon black‐loaded rubbers
Authors: Payne A. R.
Published: April 2003

Electrical conductivity and dynamic shear modulus measurements were made simultaneously on carbon black‐filled natural rubbers. G′ the in‐phase shear modulus, and the electrical conductivity, C, were shown to vary in an approximately similar way as the amplitude of dynamic oscillation was increased. Both G′ and C altered sigmoidally from a high value at low amplitudes of oscillation to very much reduced values at high amplitudes of oscillation. Recovery curves for conductivity were shown to be parallel with respect to the logarithm of the time (in minutes), even though the initial deforming amplitudes varied widely.
Degradation and stabilization of polyacetal copolymers
Authors: Berardinelli F. M. , Dolce T. J. , Walling Cheves
Published: April 2003

Acetal copolymers prepared from trioxane and ethylene oxide consist of polyoxymethylene segments with oxyethylene units distributed in the chain. These oxyethylene units profoundly affect the thermal and chemical behavior of the polymer. The presence of the oxyethylene units renders the copolymer amenable to thermal or base hydrolytic treatment which results in a final product with stable endgroups. The copolymers so obtained are significantly more stable, thermally and chemically, than acetylated polyoxymethylene homopolymer.
Continuous measurement of polymerization rates over the entire conversion range with a recording dilatometer
Authors: Rubens L. C. , Skochdopole R. E.
Published: April 2003

A new type dilatometer has been described which will automatically record the volume changes which occur during the entire course of polymerization reactions. Experiments have shown that the weight per cent polymer in a monomer solution is more accurately described as a function of additive densities of monomer and polymer than of additive volumes of monomer and polymer. The operation of the dilatometer, the relation of the observed volume changes to monomer conversion to polymer, and the possible errors involved in these type measurements have been discussed. The apparatus has been used to obtain rate curves for the polymerization of both linear and crosslinked vinyl monomer compositions over the entire course of polymerization, despite the early formation of a firm crosslinked gel structure in the latter case.
Mechanical properties of highly filled elastomers. II. Relationship between filler characteristics, thermal expansion, and bulk moduli
Authors: Van Der Wal C. W. , Bree H. W. , Schwarzl F. R.
Published: April 2003

Model substances were prepared of a polyurethane rubber filled with different amounts of various fractions of sodium chloride. Eight filler fractions were used of sizes in the range of 1–480 μm. The amount of filler was varied between 0 and 50 vol.‐%. An experimental method is described by which thermal expansion and bulk modulus of an isotropic material may be simultaneously determined as functions of temperature. The materials were investigated for thermal expansion and bulk modulus. All filled and unfilled samples show a glass–rubber transition, at which temperature the thermal expansion coefficient increases considerably and the bulk modulus decreases sharply. These temperatures do not depend on amount or size of filler. The values of the bulk moduli and the thermal expansion coefficients are independent of filler size, but depend considerably on the volume fraction of filler. These values may be predicted by means of a simple macroscopic theory (Fröhlich‐Sack‐Van der Poel,) describing the bulk modulus, the thermal expansion, and the density of the composite material in terms of the corresponding properties of the components and of their relative amounts.
Effect of dispersion on the dynamic properties of filler‐loaded rubbers
Authors: Payne A. R.
Published: April 2003

A study has been made of the effect of increased time of mixing carbon black in rubber on the dynamic properties of the carbon black‐rubber vulcanizates. Increased time of mixing reduces the dynamic modulus and dynamic viscosity as well as the phase angle at moderate amplitudes of oscillation. The changes in dynamic properties with mixing time are shown to be associated with the dispersion of the carbon black.
Interfacial polycondensation of nylon 610 in continuous cascade systems
Authors: Kispert Robert C. , Griskey Richard G.
Published: April 2003

The interfacial polycondensation of nylon 610 in unstirred, continuous, cascade systems has been studied. It was found that yields increased with increased reactant flow rates. The increase was shown to result from improved mass transport due to the change from molecular diffusion at low flow rates to eddy diffusion at high flow rates. The effect of improved mass transfer was also shown in the behavior of plots of polymer intrinsic viscosity versus sebacoyl chloride concentration.
Stress softening in natural rubber vulcanizates. Part II. Stress softening effects in pure gum and filler loaded rubbers
Authors: Harwood J. A. C. , Mullins L. , Payne A. R.
Published: April 2003

Considerable stress softening (Mullins effect) occurs in both gum and filler loaded vulcanizates of natural rubber and SBR. When compared at the same stress, the extent of softening is similar in both gum and filled vulcanizates. The stress softening is shown to be mainly due to changes in the rubber phase in the filled vulcanizate, and related to that of the gum vulcanizate by the use of the strain‐amplification factor discussed in Part I of this series.
Oxidative stress relaxation of natural rubber vulcanizates at high strains
Authors: Bell C. L. M.
Published: April 2003

The effect of high strain on the oxidative stress relaxation of several natural rubber vulcanizates has been investigated. In the case of peroxide and CBS accelerated vulcanizates, the rate of stress relaxation increases with increasing strain, and this increase appears to be due to an increase in the rate of oxidation of the network. TMTD and MBT vulcanizates showed marked premature failure at high strains and no oxidative stress relaxation measurement could be made. It was found that the tensile strength of a TMTD vulcanizate was at least 20% higher in vacuum than in oxygen, due, it is believed, to stress‐induced oxidative degradation at the tip of surface flaws in the rubber.
The influence of structure and processing conditions on engineering mechanical properties in bulk crystallized isotactic polypropylene
Authors: Reinshagen J. H. , Dunlap R. W.
Published: April 2003

A study of the influence of processing conditions and structure on engineering mechanical properties was conducted in bulk isotactic polypropylene. The influence of one processing parameter, undercooling, defined so as to account for both pressure and temperature effects, was particularly studied.

Improved mechanical properties were found with increased undercooling. At low undercoolings, brittle failure without yield occurred, presumably the result of a sparsity of intercrystalline links under these conditions. As undercooling was increased, failure occurred after yielding as failure stress elevated dramatically, apparently because of greater link density. A modest improvement in yield stress with increased undercooling was attributed to the increasingly crosshatched lamellar structure produced at higher undercoolings, a structural trend confirmed by electron microscopy.

Spherulite size, varied by altering melt history (melt temperature and time at melt temperature) at constant undercooling, was found to have no effect on engineering yield stress. This result indicates that apparent yield stress–spherulite size effects found by several earlier investigators were probably caused by structural variations other than spherulite size.
Hyperfiltration membranes prepared by radiochemical grafting of styrene onto poly(tetrafluoroethylene). Influence of the size and shape of emulsion particles used to obtain the PTFE film
Authors: Munari S. , Vigo F. , Nicchia M. , Canepa P.
Published: April 2003

The hyperfiltration performances of membranes obtained from PTFE films sintered with different granulometric distribution emulsions were studied. It has been possible to show that: (1) large spherical particles lead to high flux, poor rejection membranes, and vice versa for small spherical particles; (2) the particle shape affects the membrane properties. “Stick” shaped particles lead to better rejection properties than the spherical and “fibrillar” ones. An attempt was also made to utilize a PTFE/PMMA porous support to make asymmetric membranes.
Effect of orientation of two‐dimensional filler on dynamic mechanical properties of cured epoxy resin
Authors: Iisaka Katsuyoshi , Shibayama Kyoichi
Published: April 2003

Dynamic mechanical properties of cured epoxy resin filled with mica flake, as two‐dimensional filler, were investigated over the temperature range from room temperature to 200°C. Two series of composite specimens were examined. One is series RM, containing ill‐oriented mica flakes, and another is RMB, containing mica flakes oriented in the direction parallel to the specimen surface. Both tensile and shear moduli for RMB series were determined by dynamic mechanical experiments. The tensile modulus for RMB series was always higher than that for RM series over the whole temperature range. The shear modulus for RMB series was low, compared with that of the tensile modulus in the rubbery state. The behavior of the modulus reinforcement, observed both in the glassy and rubbery states, was compared with recently proposed theories of Wu and Padawer and Beecher. In the glassy state, the tensile modulus of RM series follows Wu's theory, while that of the RMB series agrees with Padawer and Beecher's theory. In the rubbery state, the tensile modulus of each series cannot be well explained by either theory. It was proposed that the tensile stress applied to the specimen was converted to shear stress in a thin resinous layer sandwiched by two mica flakes. The modulus behavior of the RMB series can be fully explained by this model.
Improvement of the impact strength of a blend of poly(vinyl chloride) with copolyester thermoplastic elastomer by heat treatment
Authors: Nishi T. , Kwei T. K.
Published: April 2003

Dynamic mechanical properties and impact strength of a blend of poly(vinyl chloride) with a copolyester thermoplastic elastomer were studied. The microscopic structure of the blend was dependent on the thermal history of the specimen. By an appropriate heat treatment, the blend underwent phase separation with an attendant severalfold increase in room‐temperature impact strength. The mechanism of energy dissipation involves both crazing and shear flow processes.
Photodegradable polymers. II. Preparation of styrene copolymers with alkyl and phenyl β‐styryl ketones and their photodegradability
Authors: Shiraishi Shinsaku , Senō Manabu , Ishii Masao , Asahara Teruzo
Published: April 2003

Photodegradable polymers having pendent carbonyl groups attached directly to the polymer chain were prepared by copolymerization of styrene (St) with alkyl and phenyl β‐styryl ketones (RCOCHCHC6H5), where R = CH3, C2H5, n‐C5H11, n‐C11H23, t‐C4H9, cyclo‐C6H11, and C6H5. The photodegradability of these copolymers was traced by viscometric and IR spectroscopic measurements. The degradability of St–benzalacetophenone (BAPh) copolymer is greater than that of St–alkyl styryl ketone copolymers under the irradiation of a high‐pressure Hg lamp. The photodecomposition behavior St–BAPh copolymer was investigated in detail by a spectoirradiation technique. The changes in molecular weight and its distribution by photodegradation were measured by gel permeation chromatography, and the quantum yield for bond scission along the main chains of the copolymer was estimated to be about 5 × 10−3 by 328 nm irradiation in a benzene solution. Examination of the effect of wavelength of the radiation on the bond scission showed that 328‐nm light is most effective. The photochemical degradation process was shown to occur chiefly via triplet state of carbonyl groups by the quenching technique using 1,3‐cyclohexadiene as a triplet quencher. The quantum yield of decarbonylation process was also estimated to be about 4.2 × 10 −2 in benzene.
Structure and properties of abs polymers. X. Influence of particle size and graft structure on loss modulus temperature dependence and deformation behavior
Authors: Morbitzer L. , Kranz D. , Humme G. , Ott K. H.
Published: April 2003

ABS systems which differ distinctly in particle size and degree of grafting were prepared and investigated by dynamic mechanical measurements as function of temperature in the glass transition region of the rubber phase. Variation of rubber content within different sample series results in effects which were mainly referred to thermal stresses as consequence of phase interactions. Basic aspects of the deformation behavior of some of these ABS systems are studied by mechanical and morphological methods, and the operation modes of the component of a bimodal/bigraft‐system concerning toughness are discussed.
Effect of perchloric acid on the molecular weight and yield of poly‐THF
Authors: Matsuda Kazuo , Tanaka Yoshiaki , Sakai Takeyo
Published: April 2003

Polytetramethylene glycol (molecular weight range 1000–8000) was prepared by the polymerization of tetrahydrofuran (THF) using a binary catalyst system of fuming sulfuric acid and perchloric acid. When 28% fuming sulfuric acid alone was used as the catalyst, the average molecular weight of polymer was low, the maximum value being 1000–1100. By the combination of fuming sulfuric acid with a small amount of perchloric acid, the average molecular weight of the polymer was increased to about 8000. Furthermore, the molecular weight was readily controlled in the range of 1000 to 8000 by varying the amount of the binary catalyst.
Studies of polymeric systems for absorbing airborne sound
Authors: Chen Alex C. F. , Williams H. Leverne
Published: April 2003

Sound absorption properties of polymer systems were investigated as functions of temperature, frequency, and chemical composition. Viscoelastic polymers were mixed with rigid polymers to obtain improved acoustical performance. In the case of foamed polymers, it was found that the chemical nature of the polymer is the most important factor controlling sound attenuation if the thin membranes of the closed‐cell foams are “acoustically transparent.” Polyurethane‐based polymer foams have been developed which possess excellent sound absorption characteristics. The foams are closed‐cell, leathery, and “dead,” and can absorb as much as 96% of the normal incident sound energy at 1250 Hz (foam thickness 25 mm). The temperature‐dependent acoustical properties of various polymer systems are discussed in terms of viscoelastic theory of polymers.
A semiempirical equation of state for polymer melts
Authors: Olabisi Olagoke , Simha Robert
Published: April 2003

An explicit reduced equation of state is developed by combining results of the hole'theory with a semitheoretical expression for the temperature dependence of the reduced Tait parameter B̃ which is found to be in good agreement with experiment. This approach circumvents the implicit character of the theoretical equations.

Two procedures are explored to derive for a given system the PVT surface and the compressional energy and entropy changes from the corresponding reduced functions. One rests on the usual superposition of experimental and analytical isotherms and isobars. The other, and more approximate method, utilizes a correlation between the scaling temperatures, pressures, and volumes obtained previously, and requires only experimental data at atmospheric pressure and a single temperature above the glass transition (Tg) or the melting temperature (Tm). The good agreement between experiment and theory noted previously is shown to extend to the semiempirical relationships. Finally, internal pressure data for oligomers and polymers at atmospheric pressure and encompasing a wide range of reduced temperatures are examined. The ensemble of data can be described by simple power relationships between the internal energy and the density. The exponents, however, depart significantly from the van der Waal's value of unity.
Photochemical degradation of glassy polyesters of low softening point
Authors: Husband S. , Russell K. E. , Stone J. A. , Wan J. K. S.
Published: April 2003

The photodegradation of polyesters prepared by the reaction of o‐phthalic, adipic, and “dimer” acids with ethylene glycol has been studied. The polyesters softened at temperatures in the range of 25–50°C. Polymer films were irradiated in air by means of a medium pressure mercury lamp and the extent of formation of COOH groups determined by infrared spectroscopy. The films were also irradiated in vacuo and in air by means of a high‐pressure mercury lamp, and the volatile products, consisting mainly of carbon monoxide and carbon dioxide, were determined by gas chromatography.

The results are interpreted in terms of simultaneous Norrish type I and type II decompositions of the polyesters. The type I process accounts for the formation of carbon monoxide and carbon dioxide in the absence of air. The enhanced yield of carbon dioxide in irradiations performed in air is ascribed to the formation of hydroperoxide which undergoes further photolysis. The type II process accounts for the formation of COOH groups. The photodegradation of these glassy polyesters parallels that of crystalline poly(ethylene terephthalate) and is relatively unaffected by changes in composition of the aromatic polyester.
A semiempirical derivation of phase domain size in interpenetrating polymer networks
Authors: Donatelli A. A. , Sperling L. H. , Thomas D. A.
Published: April 2003

In previous papers, interpenetrating polymer networks were shown to display a cellular structure. The phase domain size of polymer II was shown to depend inversely on the crosslink density of polymer I. The present paper presents a semiempirical derivation of equations which show quantitatively the dependence of the phase domain size of polymer II on the crosslinking density of polymer I, and also on the interfacial energy and the overall composition. If polymer II is linear, the dependence on the molecular weight of polymer II is also included. The values of the phase domain sizes so estimated are compared with experimental results. While theory and experiment yield good agreement, the semiempirical nature of the equations must be borne in mind.
Wet spinning of aliphatic and aromatic polyamides
Authors: Hancock Tony A. , Spruiell Joseph E. , White James L.
Published: April 2003

Bench‐scale equipment for wet spinning was designed and built. An experimental study of the wet spinning of several polyamides has been carried out. The polymers studied include nylon 6, nylon 66, redissolved Nomex, and redissolved Kevlar. The superstructure of the wet‐spun fibers were studied by optical and scanning electron microscopy as well as small‐ and wide‐angle x‐ray diffraction. Mechanical properties were measured and related to the spinning variables. For nylon 6 and nylon 66, the coagulation bath composition was found to be of major importance in determining fiber superstructure. For the case of the redissolved Kevlar, anisotropic spinning dopes were obtained from redissolved fiber, and the wet‐spun filaments produced from such solutions were investigated. These fibers proved to have relatively high modulus and strength as spun. They had even greater strengths after hot drawing.
Viscoelastic properties of epoxy resins. III. Effect of molecular weight of antiplasticizers in highly crosslinked antiplasticization system
Authors: Hata Naoaki , Kumanotani Ju
Published: April 2003

Antiplasticization, defined as an increase in glassy modulus of polymers upon dilution with low molecular weight compounds, was studied for highly crosslinked epoxy resins. A series of oligomers with average molecular weight 500–4000 was incorporated with epoxy resins for elucidating the effect of their molecular weight on antiplasticization. The antiplasticization was found to be dependent on the molecular weight of the oligomers used. It was most evident when the lowest molecular weight oligomer was incorporated, and seems to be suppressed by increasing molecular weight of the oligomers. These results were discussed in correlation with the behavior of dynamic mechanical properties and the changes in specific volume as a function of the epoxy resin and diluents.
Melt viscosity characteristics of methacrylate–styrene copolymers
Authors: Terrell D. R. , Katiofsky H.
Published: April 2003

The activation energies of flow EA of methacrylate–styrene copolymers containing n‐butyl, n‐hexyl, n‐heptyl, n‐octyl, n‐decyl, n‐dodecyl, n‐tridecyl, n‐octadecyl, and cyclohexyl methacrylate have been investigated as a function of molecular weight, composition, and methacrylate monomer. Below a critical pendent group molar volume per chain unit (120 ± 10 ml Le Bas units), EA was found to increase with molar volume; and above this value, a decrease in EA was observed, reflecting a decrease in copolymer density. Copolymers with pendent group molar volumes per average chain unit of between 96 and 140 ml (Le Bas units) were found to exhibit sufficiently high EA values to render them suitable for use in thermoplastic and photothermoplastic devices with superior development and erasure rates, at temperatures which enabled the attainment of the development and erasure viscosities with a low expenditure of heat energy. Methacrylate–styrene copolymers with long‐chain ester methacrylates (viz., n‐decyl and n‐dodecyl methacrylate) were found to exhibit critical molecular weights Mc below 3000; and Mc was found to decrease with increasing methacrylate tail length and methacrylate concentration. These Mc values correspond to critical chain lengths Zc below 45. Similar Zc values have been previously reported for acrylonitrile–methyl methacrylate copolymers30 and ethylene–propylene copolymers.28
Modified bead‐spring theory of polymer solutions. IV. Extension to polymer melts
Authors: Everage A. E. , Gordon R. J.
Published: April 2003

A constitutive equation which has proven quite successful in describing the nonlinear viscoelastic behavior of dilute polymer solutions is extended to the case of molten polymers. The techniques utilized and similar to those discussed by Ferry in a similar adaptation of the Rouse–Zimm Theory. The resulting model is found to quantitatively portray the shear rate dependence of the non‐Newtonian viscosity and primary normal stress functions and the frequency dependence of the storage and loss moduli. Extensional flow data reported by Spearot and Metzner for two polyethylenes are well described, using parameters calculated from steady shearing measurements. Of major significance is the ability of the model to account for influences of molecular weight, molecular weight distribution, and temperature.
N‐(morpholinothio)imides as curing agents in semiefficient vulcanization systems
Authors: Son P. N. , Krueger R. A.
Published: April 2003

Semiefficient vulcanization systems (semi‐EV) are often used when a stock requires good aging properties as well as good fatigue resistance. A partial replacement of sulfur in a conventional cure system with 4,4′‐dithiobismorpholine or 2‐mercaptabenzothiazyl 4‐morpholino disulfide (BMD) is an example of semi‐EV system. However, with BMD the scorch time is not always long enough for multisteps involved in the manufacturing of tires. Such new cure retarders as N‐(cyclohexylthio)phalimide or N, N′‐bis(cyclohexylthio)oxanilide showed very little efficiency in BMD cure systems. This paper describes the usage of new curing agents, (N‐morpholinothio)imides, which can overcome the disadvantage of scorchness in BMD cure system and provide excellent aging properties. This is rationalized by the formation of BMD during vulcanization. The facile formation of BMD from N‐(4‐morpholinothio)phthalimide (MTP) and 2‐mercaptobenzothiazole (MBT) serves to illustrate the feasibility of in situ formation of BMD during cure and to explain long scorch time observed with N‐(4‐morpholinothio)imides.
Free‐radical polymerization with long‐chain branching: Batch polymerizations of vinyl acetate in t‐butanol
Authors: Chatterjee A. , Kabra K. , Graessley W. W.
Published: April 2003

Vinyl acetate was batch polymerized at 60°C in t‐butanol solution. Conversion and molecular weights were measured as functions of time for several initiator and solvent concentrations. Although the overall rate constant depends somewhat on solvent concentration, the reaction is first order in monomer concentration up to at least 60% conversion and one‐half order in the concentration of initiator. Molecular weights were independent of initiator concentration, confirming that the polymerization is transfer dominated. Measurements of M̄w and M̄w versus conversion were used to establish the individual transfer constants. All are independent of solvent concentration, except Cp, the polymer transfer constant, which decreases systematically with increasing solvent concentration.
Products of polyaddition of toluene 2,4‐dicarbonimide with triethylene glycol glycolate, thioglycolate, lactate, and p‐hydroxybenzoate
Authors: Zochniak A.
Published: April 2003

Investigations on the suitability of triethylene glycol glycolate, thioglycolate, lactate, and p‐hydroxybenzoate for the synthesis of new polyurethanes from toluene 2,4‐dicarbonimide were carried out. The products obtained were subjected to physicomechanical, thermal, dielectric, and analytical tests. IR, DTA, and TG analyses were also done.
Parameters for prediction of reverse osmosis performance of cellulose acetate propionate membranes
Authors: Kutowy O. , Matsuura Takeshi , Sourirajan S.
Published: April 2003

Data on reverse osmosis separations have been obtained for 12 alkali metal halide solutes and 24 organic solutes (including eight alcohols, four aldehydes, seven ketones, and five ethers) with cellulose acetate propionate (CAP) membranes using single‐solute dilute aqueous feed solutions at 250 psig. From the analysis of these data, the parameters and correlations needed to calculate the values of solute transport parameter DAM/Kδ for the above classes of inorganic and organic solutes for a CAP membrane of any surface porosity from data on DAM/Kδ for NaCl only have been generated. These parameters and correlations enable one to predict reverse osmosis separations of different solutes included in the classes of compounds studied in this work, from a single set of experimental data on membrane specifications given in terms of pure water permeability constant and DAM/Kδ for NaCl. The reverse osmosis characteristics of CAP material lie intermediate between those of cellulose acetate and aromatic polyamide materials reported in the literature.
Flammability and degradation characteristics of styrene–butadiene rubbers
Authors: Kratzer R. H. , Paciorek K. L. , Kaufman J. , Nakahara J. H. , Hartstein A. M.
Published: April 2003

Uncured styrene–butadiene gum, a known cured composition, and four SBR beltings used in underground coal mining were subjected to thermal oxidative degradation in static and dynamic systems. The room temperature volatiles produced under the static conditions at 370°C were identified and quantitated. Monomers and their interaction products were liberated by the raw gum; the cured composition formed together with the above products materials traceable to the curing ingredients. The four beltings gave a large spectrum of products; an attempt was made to correlate these with possible components used in belts manufacture. In the dynamic system, the occurrence of glow, the rate of smoke generation, and char yields were determined at 400°C and 500°C. None of the materials glowed at 400°C. At 500°C, the raw gum volatilized completely, and the cured rubber and two beltings glowed. One of the beltings, which failed to glow, liberated the smallest quantity of toxic products.
Kinetics of epoxy resin polymerization using differential scanning calorimetry
Authors: Peyser P. , Bascom W. D.
Published: April 2003

The kinetic parameters of the polymerization of diglycidyl ether of bisphenol A with hexahydrophthalic anhydride and benzyldimethylamine as catalyst were determined using differential scanning calorimetry. The reaction was found to be first order with some variation with temperature, and the activation energy and natural log of the frequency factor were 25 kcal/mole and ∼25 sec−1, respectively. These results are discussed with respect to a steady‐state mechanism of the polymerization and compared with results reported for other epoxide–anhydride reactions.
Depolymerization of poly‐ϵ‐caprolactam catalyzed by sodium hydroxide
Authors: Mukherjee A. K. , Goel D. K.
Published: April 2003

Depolymerization of poly‐ϵ‐caprolactam chips was carried out at low pressures (3–15 mm Hg) and elevated temperature (225°–270°C) in the presence of sodium hydroxide as catalyst. The effects of variation of amount of sodium hydroxide, time, temperature, and pressure on ϵ‐caprolactam yield were studied. With increase in alkali content the yield increases linearly, reaching a maximum at 1% (w/w) NaOH and then falls. The yield increases with time of depolymerization up to 4 1/2 hr and then becomes practically constant. Between 240° and 250°C there is a sudden increase in depolymerization rate. Further increase in temperature has very little effect. Decrease in pressure from 15 to 3 mm Hg shows a nine‐fold increase in yield. The optimum conditions for the depolymerization were a temperature of 250°C, a pressure of 3 mm Hg, and a time 4 1/2 hr in the presence of 1% NaOH (w/w), which gave a 90.5% yield of ϵ‐caprolactam. Physical properties, IR spectra, and behavior toward polymerization of the recovered monomer indicated the presence of some impurities.
Binding of heavy metal ions by formaldehyde‐polymerized peanut skins
Authors: Randall John M. , Hautala Earl , McDonald Gary
Published: April 2003

Peanut skin, when treated with formaldehyde to polymerize tannins, is a highly efficient substrate for removal of many heavy metal ions from aqueous waste solutions. The ions Ag1+, Cd2+, Cr6+, Cu2+, Hg2+, Ni2+, Pb2+, Zn2+, as well as Ca2+ and Mg2+, were contacted with formaldehyde‐treated peanut skin. Quantitative removal could be achieved with Ag1+, Cd2+, Cu2+, Hg2+, Pb2+, and Zn2+. Capacity of the substrate for ions was promising for Pb2+ (2.1 meq/g substrate), Cu2+ (3.0 meq/g), and Cd2+ (1.3 meq/g). Sorption from a solution containing Cd2+, Cu2+, Hg2+, Ni2+, Pb2+, Zn2+, on a packed column of formaldehyde‐treated peanut skin indicated that Hg2+, Pb2+, and Cu2+ were rapidly and completely bound to the packing, while Cd2+, Ni2+, and Zn2+ were poorly bound until the preferred ions had been removed from solution.
Mechanical properties of urea–formaldehyde foam
Authors: Sarig Y. , Little R. W. , Segerlind L. J.
Published: April 2003

The mechanical behavior of urea‐formaldehyde foam was studied to evaluate its potential for energy absorption applications. The apparent elastic modulus (Ef) as a function of foam density was obtained from force‐deformation tests. The values of energy absorption capacity were derived from a numerical integration technique. Poisson's ratio (v) was determined by a method of uniaxial compression of cylindrical samples. An increase in foam density results in an increase in the apparent elastic modulus of the material and therefore in its energy absorption capacity. Poisson's ratio is independent of the foam density. The mechanical properties' values obtained can be incorporated in various analyses for predicting desired characteristics for energy absorption applications.
Solvation and phase separation in ABA block copolymers
Authors: Picc Efrain R. , Williams Michael C.
Published: April 2003

A conceptual scheme is presented for classifying the phase behavior of ABA block copolymers and solvents. The effect of solvent fraction ϕS on microphase separation is described for macroscopically homogeneous systems, but more attention is focused on the limits of solubility. A “miscibility map” is developed in terms of solubility parameters δA, δB, and δS and used to define regions of macrophase separation, complete miscibility, and partial miscibility. Combined with known triblock molecular structure, the miscibility map can be used to predict the character of solvated systems and guide the selection of solvents for special purposes. A survey of reports in the literature shows qualitative consistency with this treatment. New observations are reported on solvation of a polystyrene–polybutadiene–polystyrene polymer in numerous solvents; these are used to infer microstructural information and define the miscibility map more realistically.
A new biodegradable plastic made from starch graft poly(methyl acrylate) copolymer
Authors: Dennenberg Ronald J. , Bothast Rodney J. , Abbott Thomas P.
Published: April 2003

A starch graft poly(methyl acrylate) copolymer was developed having grafted side chains with molecular weight of less than 500,000. This material can be easily extruded into a film which shows excellent initial tensile strength and elongation. Tensile strength, however, falls off rapidly after 70 hr of water immersion at 25°C. Starch graft poly(methyl acrylate) films show excellent susceptibility to fungal growth, some samples losing more than 40% of their weight after 22 days of incubation with Aspergillus niger. Tensile tests and scanning electron micrographs of the incubated samples, after being freed of mycelium, indicate substantial biodegradation of the starch portion of the copolymer. This material may have application as a biodegradable plastic mulch.
Kinetics of sorption of aliphatic acids by oleophilic anion exchange resins in toluene
Authors: Walden John , Miller Irving F. , Gregor Harry P.
Published: April 2003

The rate of sorption of toluene by dry oleophilic anion exchange resins in the hydroxide state was measured both by direct weight measurements and also by the visual observation of the rate of movement of a refractive index gradient between unreacted and reacted zones. The rate of sorption of carboxylic acids from solution in toluene was also measured by beads swollen in toluene, both by direct chemical analysis of the solution and by the visual method. Diffusion coefficients of acids in the resins were calculated using three different theories for diffusion in gels coupled with chemical reactions, and reasonable agreement between theory and experiment was found.
Thermal oxidation of fractionated polypropylene in solution
Authors: Osawa Zenjiro , Saito Takashi , Kimura Yuji
Published: April 2003

Thermal oxidation of fractionated polypropylene was carried out in trichlorobenzene under atmospheric oxygen at 125°C with conventional oxygen uptake. The oxidizability of the polymers is discussed on the basis of the oxygen uptake curves and the properties of the polymers. Fractions of atactic polypropylene oxidized easily at the initial stage of the oxidation and showed neither autoxidation phenomena nor the induction period observed in the isotactic polymer. Hydrogenation of the ether‐soluble fraction by a Wilkinson catalyst gave a polymer which was, according to infrared spectrometry, free from impurity groups such as hydroperoxide, carbonyl, and unsaturation groups. The hydrogenated fraction was more stable to thermal oxidation than the unhydrogenated fraction and showed an induction period. The results indicate that the initiation process of the oxidation of polypropylene is apparently dependent on the impurities such as hydroperoxide, carbonyl, and unsaturation and that stereoregularity of the polymer affects the kinetic dependence of the oxidation.
Liquid exclusion chromatography. A technique for monitoring the growth of polymer particles in emulsion polymerization
Authors: Singh S. , Hamielec A. E.
Published: April 2003

An experimental investigation of the growth of polymer particles in the emulsion polymerization of styrene and of vinyl acetate is reported. The growth of polymer particles in the size range of 200–6500 Å was monitored by liquid exclusion chromatography (LEC). This relatively new analytical technique permits very rapid analysis for particles as small as 200 Å and should prove extremely useful as an online monitor of polymer particle size for the control of latex reactors.
Reverse osmosis with dynamically formed membranes from water‐soluble polymers
Authors: Igawa M. , Senō M. , Takahashi H. , Yamabe T.
Published: April 2003

Membranes were dynamically formed from poly(acrylic acid), poly(1‐methyl‐2‐vinylpyridinium iodide), and methylcellulose on a Millipore filter. The effects of the conditions of membrane formation on reverse osmosis performances and the membrane structure were investigated. The primary factors that affect membrane performance were ascertained to be the kind and concentration of salts and the pH of the preparing solutions, the concentration and the polymerization degree of the membrane materials, the pore size of filters, and the pressure and circulation velocity during membrane formation. Two types of dynamically formed membranes, the membranes inside the filter and the membranes on the filter, were distinguished.
Effects of molecular weight distribution and long‐chain branching on the viscoelastic properties of high‐ and low‐density polyethylene melts
Authors: Han Chang Dae , Villamizar Carlos A.
Published: April 2003

Using the Han slit/capillary rheometer, rheological measurements were taken of several commercially available low‐ and high‐density polyethylene melts, namely, three low‐density polyethylene samples of Chemplex Corp. (CX 1005, CX 1016, and CX 3020), three low‐density polyethylene samples of U.S. Industrial Chemicals Co. (NA 205, NA 244, and NA 279), two high‐density polyethylene samples of Union Carbide Corp. (DMDJ 5140 and DMDJ 4306), and two high‐density polyethylene samples of Mitsui Petrochemical Industries, LTD. Molecular characterization of these samples was carried out by the resin suppliers. The rheological measurements included (1) entrance pressure drop, (2) exit pressure, (3) pressure gradient, (4) die swell ratio. These then permitted us to determine the shear viscosity and normal stress differences. The rheological measurements were interpreted to identify the effects of long‐chain branching and molecular weight distribution on the rheological properties of polyethylenes in the light of the existing molecular viscoelasticity theories. It was found that fluid elasticity is greater for polymers having a broader molecular weight distribution and that, for polymers having more long‐chain branching, viscosities are lower while elasticities are higher.