bluuebunny/crossref_metadata_2025 huggingface dataset:
Friction and deformation of nylon. I. Experimental
Authors: Adams N.
Published: April 2003

An apparatus which permits the simultaneous measurement of kinetic friction and contact area between polymer hemispheres and a smooth glass surface has been used to study the dependence of friction and contact area on load, specimen radius, sliding speed, and loading time. Hemispherical nylon 610 specimens of radii 0.12–0.58 cm. have been used with loads of 0.7–200 g. and sliding speeds from 10−7 to 3 × 10−2 cm./sec. All measurements were performed in air at 20°C. and 66% r.h. The contact area was estimated from optical interference fringes (Newton's rings) between the surface of the specimen and that of the glass plate, by means of a theoretical expression, experimentally verified, for the shape into which an elastic hemisphere is deformed when pressed against a rigid plane. The contact area was negligibly affected in size or shape by the presence of the tangential force of friction, in accord with the theory for the contact of elastic spheres. The deformations of the specimens were, within experimental error, completely recoverable but depended on the time of loading. The effects of changes in the four variables, load, radius, speed, and time were found to be essentially independent. Subsidiary experiments showed that both friction and contact area increased by about 10% for each factor‐of‐10 increase in loading time in the range 5–1000 sec. and that friction increased by a factor of 3 as sliding speed increased from 10−7 to 3 × 10−2 cm./sec. The main series of measurements (at constant sliding speed and loading time) showed that the dependence on load W of both the contact area A and the friction F could well be represented by the expressions: A = βWm and F = αWn (where α and β were constants for a given specimen). The values of m and n were almost independent of specimen radius and their mean values, for 15 specimens, were 0.708 ± 0.006 and 0.781 ± 0.012, respectively. The difference between these values, 0.073 ± 0.013, is statistically highly significant and in the following paper is interpreted as implying that the friction per unit area of true contact between nylon and glass increases with pressure. The dependence of A on the specimen radius R (which is included in β) was found to be as R0.576. The value of this index of R and the value of m are both consistent with a power‐law dependence of mean contact pressure on deformation (measured by the ratio of contact to specimen radius) with index 0.82. The values of α for specimens of the same radius showed too much variation for a useful estimate of the dependence of F on R to be obtained.
Polymer structure and gas permeation II. Permeation studies
Authors: Roberts R. W. , Kammermeyer K.
Published: April 2003

A series of gas permeability studies of plastic membranes demonstrated the strong dependence of gas transport on structural aspects of the membrane. Films of cellulose acetate butyrate, silicone rubber, polyethylene, polypropylene, and vinyl chloride, were used in these studies. The effect of elastic and nonelastic stretching, orientation, plasticization, and phase changes were shown to be detectable by gas permeations. Interpretation of the permeation response, as a function of temperature, is compatible with a thermodynamic appraisal of the permeation process.
Determination of carboxyl groups in the presence of carbonyl groups in oxidized polyolefins by using sulfur tetrafluoride
Authors: Heacock J. F.
Published: April 2003

A simple analytical technique has been developed to determine the amount of carboxyl groups present in degraded polyethylene film. This procedure is based upon the relative reactivities of the various carbonyl groups present, in oxidized polyethylene film, to sulfur tetrafluoride gas. The quantity of the carboxyl groups in the film is then measured as a function of the absorption at 5.45 μ.
Cut growth and fatigue of rubbers. I. The relationship between cut growth and fatigue
Authors: Gent A. N. , Lindley P. B. , Thomas A. G.
Published: April 2003

The relationship between the cut growth and fatigue failure of natural rubber vulcanizates under repeated loading is examined. The cut growth behavior has been investigated using several types of test piece, and the results are shown to be consistent when interpreted in terms of the tearing energy concept developed previously. The most comprehensive data have been obtained by measuring the growth of a small cut in the edge of a strip cycled in simple extension. It is found that the cut growth per cycle is approximately proportional to the square of the maximum tearing energy attained during the cycle. Using this relation, the fatigue life of a specimen containing a small cut is deduced from elasticity theory as a function of initial cut size and maximum strain. Experimental results give good agreement with theory. A similar strain dependence is found for the fatigue life of die‐stamped dumbbell test pieces with no intentionally produced flaws; this is consistent with the mechanism of failure being cut growth from small flaws present in the specimens. Their effective size is estimated to be about 2 × 10−3 cm, which is compatible with the observed superficial imperfections of the cut edges.
Crystallite orientation in regenerated cellulose filaments. II. Effect of degree of polymerization and stretch
Authors: Ellis K. C. , Warwicker J. O.
Published: April 2003

Measurements of the degree of orientation in cellulose filaments prepared from fractions of secondary cellulose acetate having a very limited range of degree of polymerization have shown that the degree of orientation produced by a given effective stretch increases as the degree of polymerization increases. The orientation distributions of the (101) and (020) planes have been compared with those predicted by Kratky's theory for the deformation of a material containing rod‐shaped crystallites, and it has been shown that the shapes of the observed and theoretical distributions are the same if the appropriate value of the degree of stretch is used. This value is always less than that calculated from the changes in the dimensions of the filaments produced by stretching. Kratky's theorv cannot however account for the variation with degree of polymerization and does not account for the observed shape of the curves for orientation as a function of stretch. Consideration of the process by which the filaments were produced shows that the filaments were subjected to stretches additional to those intentionally applied to them. The results of the orientation measurements are compared with published figures for the birefringence and tenacity of similar filaments, and linear relations are found between birefringence and orientation and between tenacity and orientation.
Evaluation of poly(2,6‐dimethyl)‐1,4‐phenylene oxides and related copolymers for high temperature adhesive application
Authors: Hoyt H. E. , Halpern B. D. , Tsou K. C. , Bodnar M. , Tannar W.
Published: April 2003

Poly‐(2,6‐dimethyl)‐1,4‐phenylene oxides and related copolymers have been evaluated for high temperature adhesive applications. Because of the high‐melting character of these polymers, proper wetting was found to be difficult to achieve. Where such conditions can be obtained, good tensile strength values have been reached up to 600°F. The introduction of allyl group and epoxy group into such polymers provides sites for thermosetting. The fast setting rate of these groups, however, introduces difficulty in bonding procedure. Problems and ways to improve the initial bonding of specimens are discussed.
Partial specific compressibility of polystyrene
Authors: Nomura Hiroyasu , Miyahara Yutaka
Published: April 2003

The partial specific compressibilities of polystyrene at infinite dilution in such solvents as methyl ethyl ketone, toluene, dioxane, and a mixture of methanol and toluene were determined by ultrasonic velocity measurements and were compared with the intrinsic viscosities. The limiting partial specific compressibility decreased with decreasing solvent power. The variation of this quantity was ascribed to the increase in the segment‐segment contacts on the basis of a macroscopic model. The limiting partial specific compressibility is a measure of the compactness of the polymer molecule.
Light‐sensitized crosslinking of polyvinyl alcohol by chromium compounds
Authors: Duncalf B. , Dunn A. S.
Published: April 2003

The insolubilization of polyvinyl alcohol by potassium dichromate on exposure to light has been investigated. Ultraviolet spectrometry shows that secondary hydroxyl groups are oxidized to ketone groups but insolubilization is attributed to crosslinking of polymer chains by co‐ordination of alcohol groups to “nascent” chromic ions formed by reduction of the dichromate. Exposure to air saturated with water vapor eliminates the carbonyl absorption maxima from the ultraviolet spectrum of polyvinyl alcohol film but the spectrum can be restored by heating: this phenomenon is independent of the crosslinking reaction.
Phenolic‐formal resins
Authors: Heslinga A. , Schors A.
Published: April 2003

A new method of curing phenolic novolac resins by means of cyclic formals under the catalytic influence of strong acids is given. It was proved that the formals react with the novolac molecules to form a highly crosslinked resite structure. As a practical consequence of this novel curing process it is possible to use the new resins at low or contact pressures in molding operations. The physical properties of the end products in general resemble those of the standard phenolic casting resins.
Acid–base properties of fibers. Part I. Nylon
Authors: Mathieson A. R. , Whewell C. S. , Williams P. E.
Published: April 2003

The acid‐base titration curves of solid nylon 6 resins and nylon 66 fibers have been measured, and isoionic points and endgroups determined. Five nylon 6 polymers of different molecular weights and two commercial nylon 66 yarns have been studied. Titration curves of these materials with hydrochloric acid and sodium hydroxide in the absence of added salt, and of nylon 66 in the presence of added salt, at three different temperatures, and with benzenesulfonic, trichloroacetic, and naphthalene‐2‐sulfonic acid, allowed the effect of polymer molecular weight, salt, temperature, and anion affinity on the titration curves to be determined. All the results are consistent with the view that nylon possesses a zwitterion structure at neutral pH, carboxyl groups being protonated on acid titration. A proportion of the endgroups is not available to titration in the solid polymers. Existing theories of the acid–base combination of solid polymers fail to explain all the results. The titration curves and elastic properties of the following modified nylon 66 yarns have also been determined and interpreted: nylon deaminated by nitrous acid, dinitrophenylated, acetylated, carboxymethylated, hydrolyzed, and dihydrophenylated nylons, and nylon treated with alkaline hypochlorite, boiling water, and boiling benzene. In all cases the increase in the work to stretch the filament is independent of pH.
Capillary viscometry of molten polycaprolactam
Authors: Pezzin G. , Gechele G. B.
Published: April 2003

A study was made of the rheological behavior of 35 samples of nylon 6 polymers of molecular weights varying from 4,000 to 40,000. A capillary extrusion rheometer was employed, and flow curves extending over a large range of shear rates were obtained. The effect of temperature, shear rate, and molecular weight on viscosity is reported, and some peculiarities of the flow behavior of nylon 6 polymers are discussed.
Partial specific compressibility of dextran
Authors: Nomura Hiroyasu , Yamaguchi Sadao , Miyahara Yutaka
Published: April 2003

The limiting partial specific compressibility (LC) of low molecular weight dextran in aqueous solution was determined by the measurements of ultrasonic velocity and density. The negative value of LC was ascribed to hydration. The amount of bound water calculated from LC and its temperature dependence were in accord with those of sugars in order of magnitude.
Column fractionation of polymers. IV. Large‐scale polyester column fractionation
Authors: Cantow Manfred J. R. , Porter Roger S. , Johnson Julian F.
Published: April 2003

A small‐scale fractionation of 9 g. and a large‐scale fractionation of 90 g. of a polyester were carried out. The polymer was prepared by condensation of isophthalic acid, maleic anhydride, and propylene glycol in the mole ratio 1:2:3. Results from the two fractionations were in good agreement despite different fractionation conditions. By proton magnetic resonance measurements the fractions were found to have nearly constant chemical compositions. The Huggins' constant and the Staudinger relation for this polyester were determined from data on fractions in chloroform at 30°C. Integral and differential molecular weight distributions as well as various molecular weight averages for the polyester were obtained by a computer program. The fractionation data were applied to several popular distribution correlations. The experimental distribution was found to be in good agreement with that expected from the theory of polycondensation kinetics.
Semipermeable membranes of cellulose acetate for desalination in the process of reverse osmosis. I. Lyotropic swelling of secondary cellulose acetate
Authors: Kesting Robert E.
Published: April 2003

The role of certain inorganic salts in increasing the flux of water through semipermeable membranes of cellulose acetate is related to the capacity of the component ions to swell the cellulosic substrate. The mechanism whereby ions which are high on the Hofmeister lyotropic series swell and dissolve secondary cellulose acetate has been investigated. Swelling is effected by the formation of metastable complexes involving the highly hydrated cationic fraction of the salt and both the hydroxyl and acetate groups of the cellulose acetate. Whereas effective anions possess large ionic radii and cause a breakdown in the structure of water which results in increased hydration of the cation, ineffective anions possess higher charge densities and tend to pair with the cation and decrease the latter's electrophilicity and hence hydratability. Ionic charge density is the factor of prime importance both with respect to the hydratability of the cation and the tendencies toward water disaggregation and ion association of the anion. The mechanism involved in the swelling of secondary cellulose acetate is related to swelling phenomena in many other polymers containing polar groups.
Electrochemical properties of thin parlodion membranes
Authors: Lakshminarayanaiah N. , Shanes Abraham M.
Published: April 2003

Thin membranes (50‐800 A. thick) formed by spreading a solution of Parlodion in isoamyl acetate on the air‐water interface have been characterized. The electrical resistance and capacitance of these membranes prepared from each of the three Parlodion concentrations viz., 5, 10, and 20 mg./ml. solution, have been measured as functions of both membrane thickness and external electrolyte (KCI) concentration. Capacitance values corroborate the thickness inferred from the weight of material transferred to cover a fixed area. Membrane resistance drops with increase in thickness. Resistivity of a membrane 100 A. thick rises with decrease in external electrolyte concentration. Acid and alkaline solutions of KCI lower membrane resistance due to increased porosity of the membrane brought about possibly by the hydrolysis of the membrane material. Membrane potentials arising across these membranes also have been measured as functions of both membrane thickness and external electrolyte concentration. The bi‐ionic potentials confirmed the usual order of penetrability of alkali metal ions observed in artificial membranes. A study of the effect of pH on membrane potentials indicates that the electrochemical activity of the membrane may be attributed to the presence of odd and terminal carboxyl groups in the nitrocellulose matrix of the membrane.
Effects of molecular weight distribution and branching on rheological parameters of polyethylene melts. Part II. Fractions and blends
Authors: Guillet J. E. , Combs R. L. , Slonaker D. F. , Weemes D. A. , Coover H. W.
Published: April 2003

Studies of the rheological properties of fractions of linear and branched polyethylenes have shown that the melt recovery of linear polyethylene fractions is very small and independent of molecular weight over a wide range. Fractions containing high degrees of long‐chain branching, on the other hand, have high melt recoveries. The melt recovery of a fraction can therefore be used as an index of long‐chain branching. Alternatively, if no long‐chain branching is present, the melt recovery is a unique function of the molecular weight distribution. This effect is illustrated by blends of fractions. The log of the critical shear rate is a linear function of the log melt viscosity of the fraction for both linear and branched polyethylenes. This would indicate that the critical shear rate of polydisperse samples would depend primarily on the weight‐average of Z‐average molecular weight of the polymer. This is confirmed by previous studies on polydisperse samples. It also appears that critical shear rate is highly dependent on the homogeneity of the sample. Blends of the same fractions had quite different critical shear rates, depending on the procedure used to prepare them, even though their molecular weight distributions were identical. The change in viscosity with shear rate is not a unique function of molecular weight or melt viscosity. Fractions of linear polyethylene show a greater change in viscosity with shear rate than branched fractions of similar low shear melt viscosity. This suggests that the effect is related to chain entanglement or coordinated segmental motion.
Formulas for the dielectric constant and dissipation factor of mixtures and their application to the cellulose system
Authors: Venkateswaran A.
Published: April 2003

Formulas for the dielectric constant and dissipation factor of a dielectric mixture of many components have been derived assuming (1) that the dipoles can point only in two definite directions, along and opposite to the directions of the applied field, and (2) that the dipole is a highly anisotropic body having a needle shape. The formula for the dielectric constant is applied to calculate the dielectric constant of cellulose at any sheet density. The application of the Clausius‐Mosotti relation for the dielectric constant‐density relation is discussed.
Spin casting of polymer films
Authors: Kaelble D. H.
Published: April 2003

A versatile technique for spin casting of small polymer films within a cylindrical open faced mold is described. The high centripetal acceleration, about 500g, provides outstanding thickness uniformity and freedom from interior defects. The casting apparatus may be provided with pressure, temperature, and atmosphere control. A compact unit for simultaneous casting of four films is illustrated.
Reactions catalyzed by minerals. Part I. Polymerization of styrene
Authors: Solomon D. H. , Rosser M. J.
Published: April 2003

The polymerization of styrene on neutral mineral surfaces has been studied. It has been shown that the polymerization has characteristics expected for both a radical and cationic reaction, and a mechanism involving a radical‐carbonium ion is proposed to explain this evidence. A range of mineral catalysts have been investigated and a tentative theory proposed to relate the variation in activity with catalyst structure. Experiments have also been carried out to define the specific portion of the mineral surface responsible for the catalyst activity.
Preparation and characterization of thin parlodion membranes
Authors: Lakshminarayanaiah N.
Published: April 2003

Parlodion membranes 95 to 500 A. thick have been prepared on a glass surface by dipping a clean glass plate into the Parlodion solution and subsequently evaporating the solvent under controlled conditions by keeping the glass plate vertical in a metallic frame and covered with an inverted beaker. The membrane may be floated off on to an aqueous surface. Capacitance measurement established the thickness of the membrane. Electrical resistance and isothermal diffusion potentials arising across them when they separate different salt solutions have also been measured at room temperature.
Kinetics of emulsion polymerization
Authors: O'toole J. T.
Published: April 2003

The quantitative theory of free radical mechanisms in emulsion polymerizations is reexamined. It is suggested that existing descriptions are not entirely consistent with physically realizable situations. The proposed modifications result in a closer resemblance to homogeneous systems. Explicit expressions for the distribution of radicals are also given. The importance of interphase transfer is emphasized.
Transport properties of cellulose acetate osmotic membranes
Authors: Lonsdale H. K. , Merten U. , Riley R. L.
Published: April 2003

Diffusion and distribution coefficients of water and sodium chloride have been measured in cellulose acetate osmotic membranes. These coefficients have been found to vary with the degree of acetylation of the cellulose ester. The diffusion coefficient of water varies from 5.7 × 10−6 to 1.3 × 10−6 cm.2/sec., and the diffusion coefficient of salt varies from 2.9 × 10−8 to 3.9 × 10−11 as the acetyl content is increased from 33.6 to 43.2 wt.‐%. A homogeneous diffusion model is proposed which describes the observations in terms of Fick's law.
Relative inhibitory effect of various compounds on the rate of polymerization of methyl methacrylate
Authors: Georgieff K. K.
Published: April 2003

The relative inhibitory effect of the following compounds on the bulk polymerization of methyl methacrylate were measured: hydroquinone, p‐tert‐butylcatechol, p‐methoxyphenol, 2,4‐dichloro‐6‐nitrophenol, n‐propyl gallate, di‐tert‐butyl‐p‐cresol, 2,2'‐methylenebis(4‐methyl‐6‐tert‐butylphenol), 1‐amino‐7‐naphthol, p‐benzoquinone, 2,6‐dichloro‐p‐benzoquinone, 2‐amino‐1,4‐naphthoquinone, three aminoanthraquinones, diphenylamine, p‐nitrosodimethylaniline, α‐ and β‐naphthylamine, phenothiazine, N‐nitrosodimethylamine, hexamethylphosphoramide, n‐dodecyl mercaptan, benzenethiol, 2,2‐diphenyl‐1‐picrylhydrazyl, phenyl hydrazine, divinylacetylene, and various antimony and copper salts. Polymerization was carried out in a test tube in a bath at 101.2°C., benzoyl peroxide being used as initiator. Generally, phenols and naphthols were the strongest inhibitors, followed by quinones, aromatic amines, 2,2‐diphenyl‐1‐picrylhydrazyl, antimony pentachloride, phenyl hydrazine, divinylacetylene, and the thiols.
Estimation of kinetic parameters from thermogravimetric traces
Authors: Reich Leo
Published: April 2003

A novel and comparatively simple procedure is described for the estimation of values of kinetic parameters from thermogravimetric traces. The expressions derived are assessed for their facility and reliability by utilizing data from theoretical and experimental thermograms. Calculated values of parameters agree well with assumed or reported values.
Polymerization of methyl methacrylate under ultrasonic irradiation
Authors: Osawa Zenjiro , Igarashi Nobuo
Published: April 2003

Polymerization of methyl methacrylate with Grignard reagents and benzoyl peroxide under ultrasonic irradiation was carried out and the effect of the ultrasonic irradiation on the stereoregularity and the properties of the polymers obtained was studied. No effect of ultrasonic irradiation on the stereoregularity of the polymers was observed, but the yield and the intrinsic viscosity of the polymers were lower than those of polymers produced without ultrasonic irradiation. It is, therefore, assumed that the bonds at a propagating site between an active polymer end and a counterion are fairly strong and are not broken by the externally applied energy corresponding to an ultrasonic wave of 500 keycles/sec., even though carbon–carbon covalent bonds in the main chain are broken.
Some aspects of the degradation of epoxide resins
Authors: Stuart J. M. , Smith D. A.
Published: April 2003

This paper contains a description of the use of gas chromatography to examine the pyrolytic degradation of epoxide resins. The method depends on the pyrolysis of the material by use of an electrically heated filament, the difficulties of the method are examined and attempts to overcome them are described. The pyrolytic degradation of a resin based on the glycidyl ether of bisphenol‐A hardened with 1,2‐diaminoethane and also triethylenetetraamine, is described. An attempt has been made to explain, in terms of possible degradation reactions, the actual compounds detected in the pyrolytic breakdown.
Glass transition temperatures of poly(methyl methacrylate) plasticized with low concentrations of monomer and diethyl phthalate
Authors: Dudek Thomas J. , Lohr Jerome J.
Published: April 2003

The effect of low plasticizer concentrations on the glass transition temperature of poly(methyl methacrylate) (PMMA) has been studied experimentally for diethyl phthalate (DEP) and methyl methacrylate (MMA) as plasticizers. Volume dilatometry, differential thermal analysis, and a torsional pendulum were used to determine glass transition temperatures. The monomer‐plasticized PMMA samples were prepared by polymerizing MMA to a limiting conversion which was found to depend primarily on temperature. At temperatures slightly above the glass transition temperature of a MMA–PMMA system, a polymerization reaction occurred at a rate rapid enough to complicate the interpretation of the dilatometric and differential thermal analysis methods for determining the glass transition temperature. However, the torsional pendulum method could be used since it did not require measurements to be made at temperatures where polymerization could occur. The differential thermal analysis results showed that the temperature at which the polymerization reaction was first detectable was related to the glass transition temperature of the MMA–PMMA solution. The measured glass transition temperatures were compared with the predictions of the theories of Fox, Kelley, and Bueche, and Dimarioz and Gibbs on the effect of plasticizer concentration on the depression of the glass transition temperature.
Thermal characteristics of some rigid urethane foams
Authors: Smith Clifford H.
Published: April 2003

The thermal stability characteristics of three rigid urethane foams prepared from various formulations, to give a wide range of molecular structure, were investigated by means of TGA, DTA, and long‐term heat aging. Compressive strength values over a temperature range of −73°C to +232°C were also determined for these foams. Based on all tests performed, a toluene diisocyanate foam displayed the poorest thermal stability characteristics of the three foams studied. A combination toluene diisocyanate–polymethylene polyphenylisocyanate foam showed intermediate elevated temperature properties, whereas, a foam employing only polymethylene polyphenylisocyanate demonstrated the best over‐all high temperature stability.
Pressure chamber for use during differential thermal analyses
Authors: Wisnewski Antoinette M. , Calhoun Robert J. , Witnauer Lee P.
Published: April 2003

This article describes a simple cell suitable for use with the Du Pont 900 differential thermal analyzer to maintain pressures up to 150 psi. Also discussed are two applications of such a device.
Specific refractive index increments of polymer solutions. Part I. Literature values
Authors: Huglin M. B.
Published: April 2003

The specific refractive index increments of 158 natural and synthetic polymers and copolymers in pure and mixed solvents have been collated. Wherever possible the temperature and wavelength (generally 436 and/or 546mμ) are quoted.
Polarization colors of nitrocellulose
Authors: Kohlbeck J. A. , Bolleter W. T.
Published: April 2003

The polarization colors of nitrocellulose (NC) fibers show an orderly progression from gray‐white at 11.0% nitrogen (N) through first‐order whites, yellows, and reds to second‐order blue at 12.6% N. At higher levels of nitration, the polarization colors revert back to first orders with fibers containing 13.1% N showing gray changing to intense white at 13.5% N. The length‐positive and length‐negative character of NC fibers also changes with the degree of nitration. Fibers nitrated to about 12.4% N are optically neutral and become increasingly positive with a decrease in the level of nitration and increasingly negative as the level of nitration increases. This optical property and the polarization colors of NC provide much information about the level and range of nitration of NC fibers.
An infrared technique for the quick analysis of cotton–polyester blends
Authors: Iyer P. Bhama , Iyer K. R. Krishna , Patil N. B.
Published: April 2003

The details of an infrared technique standardized to analyze cotton–polyester blends of different compositions are reported. It is observed that particle size plays a very important role in the peak intensity of the 1725 cm−1 band (CO stretching) in polyester, the absorption band recommended for analysis of cotton–polyester blends. However, the product of the band width and peak intensity is found to be dependent on particle size to a lesser extent and hence is a more reliable parameter in the measurement of percentage composition. It has further been shown that the method of sample preparation can affect the band width and hence the results. A suitable sample preparation procedure is, therefore, described whereby an accuracy of ±3% in the estimation of polyester content in a given blend can be achieved.
Modification of poly(vinyl alcohol) fibers by hexamethylene diisocyanate
Authors: Varma D. S. , Nedungadi Chandran
Published: April 2003

Poly(vinyl alcohol) multifilament yarn was modified by reaction with hexamethylene diisocyanate. The effects of reaction variables such as time, temperature, concentration of reagents, solvent, and atomosphere were studied. The role of solvent appears to be very important in the reaction. Dimethylformamide, on account of its swelling power, proved better than the solvents benzene, toluene, and dioxane. Physical properties of modified fibers were compared with those of the parent. Moisture regain of the modified samples decreased with increasing add‐on percent. The elastic recovery was not improved, and there was little effect of the HMDI treatment on mechanical properties. The thermal stability of poly(vinyl alcohol) modified with diisocyanate with small add‐on was slightly improved.
The effect of red phosphorus on the flammability of poly(ethylene terephthalate)
Authors: Granzow A. , Cannelongo J. F.
Published: April 2003

Addition of red phosphorus in concentrations of about 4% to poly(ethylene terephthalate) (PET) reduces the flammability of that polymer. The rates of flame propagation and the ignitability are reduced, while the oxygen index (O.I.) is increased. The surface temperature of burning PET amounts to TS ≈ 380°C; addition of 4% red phosphorus raises this value to TS ≈ 450°C. An increase of the environmental temperature TE enhances the flammability of PET and PET + phosphorus samples; the O.I. decreases and the rate of flame propagation increases with temperature. The flame‐retardant effectiveness of red phosphorus is reduced if the sample is burned in a N2O atmosphere. This indicates that part of the flame retardancy imparted by phosphorus involves gas‐phase inhibition. The major flame‐retardant action does, however, occur in the condensed phase, since the rate of pyrolysis of PET is affected by the presence of red phosphorus.
Azeotropic graft polymerizations of dienes and acrylonitrile onto poly(propylene oxide)
Authors: Fall H. H.
Published: April 2003

Graft copolymerizations of isoprene or butadiene with acrylonitrile in an approximately 2:1 weight ratio onto poly(propylene oxide) are azeotropic. These products, when vulcanized with sulfur, yield elastomers with excellent tensile properties.
Structure–property relationships in crosslinked networks from cis‐1,4‐polybutadiene and methacrylic acid. Swelling behavior
Authors: De Candia F. , Taglialatela A. , Vittoria V.
Published: April 2003

In the present paper, we report results obtained analyzing the swelling behavior of a composite system prepared from vulcanizing mixtures of cis‐polybutadiene and methacrylic acid with different amounts of acid. Two solvents were used as swelling agents, decalin and the N,N‐dimethylformamide. The structural data, given by low‐angle x‐ray diffusion spectra, were used to interpret the mechanical behavior described in terms of the Mooney‐Rivlin equation and hysteresis loops. Structural and mechanical data give information about the swelling mechanism of the solvents and about the problem of the experimental deviations from the Gaussian theory of rubber elasticity.
Analysis of cotton fiber maturity. II. Glycerol retention value of cotton
Authors: Kulshreshtha A. K. , Chudasama V. P. , Dweltz N. E.
Published: April 2003

The imbibition of glycerol by cotton has been used as a measure of fiber porosity which includes a major contribution from the fiber lumen. Cotton is swollen in glycerol to saturation and subjected to centrifugation until constant weight is attained. The glycerol retention value (GRV) is calculated from the increase in weight of cotton after swelling and centrifugation. This method is applied to determine GRVs and pore space of 12 American cottons which have different wall thicknesses but more or less the same fiber perimeter. A high negative correlation is obtained between GRV and the percentage of mature fibers for various raw and extracted cottons. Effect of fiber wax content of GRV was studied. It has been shown how the average lumen area in swollen state can be calculated from GRV and gravimetric fineness. The significance of pore space is discussed.
Thermal degradation of polystyrene
Authors: Kishore K. , Verneker V. R. Pai , Nair M. N. R.
Published: April 2003

The importance of the study of thermal degradation of polymeric fuels arises from their role in the combustion of solid propellants. Estimation of the condensed‐phase heat release during combustion can be facilitated by the knowledge of the enthalpy change associated with the polymer degradation process. Differential scanning calorimetry has been used to obtain enthalpy data. Kinetic studies on the polymeric degradation process have been carried out with the following objectives. The literature values of activation energies are quite diverse and differ from author to author. The present study has tried to locate possible reasons for the divergence in the reported activation energy values. A value of 30 kcal has been obtained and found to be independent of the technique employed. The present data on the kinetics support to chain‐end initiation and unzipping process. The activation energies are further found to be independent of the atmosphere in which the degradation of polymer fuel is carried out. The degradation in air, N2, and O2 all yield a value of 30 kcal/mole for the activation energies.
Highly accessible or decrystallized cotton by chemical methods
Authors: Tsuji Waichiro , Hirai Asako , Hosono Masao
Published: April 2003

To obtain highly accessible cotton by cyanoethylation with acrylonitrile after pretreatment with swelling agents, the effect of various swelling agents was examined. Swelling agents such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ethylamine, triethylamine, ethylenediamine, piperazine, benzyltrimethylammonium hydroside (BTMOH), urea, dimethyl sulfoxide, dimethylformamide, zinc chloride, and liquid ammonia were examined. It was found that the sodium hydroxide pretreatment or the dual pretreatment with either potassium hydroxide, ethylenediamine, or BTMOH, and sodium hydroxide prior to acrylonitrile treatment gave modified cottons having moisture regain as high as 14%. In such cases, maximum values of moisture regain were observed at the degrees of cyanoethylation of 5–8%.
Molecular stiffness and thermal properties of polymers
Authors: Aharoni Shaul M.
Published: April 2003

Because it merely reflects rotational hindrance, the parameter σ alone does not convey a measure of chain stiffness. Stiffness can arise from short links joined by rigid joints, or from long, stiff links with flexible joints. Flexibility results from the absence of rigid joints and stiff, long links. The slope of the product σΔT versus TR indicates stiffness; the higher the slope, the stiffer the chain. The polymers whose thermal data are presented in this paper are divisible into two major groups. Those whose d(σΔT)/dTR = 1.37 are flexible, and those whose d(σΔT)/dTR = 3.44 are stiff. The indication is that there exists a direct relationship between the polymer expansivity above Tg and the stiffness parameter of the chain.
Grafting of ethyl α‐cyanacrylate on poly(vinyl alcohol)
Authors: Huczkowski Pawel , Kapko Jerzy , Polaczek Jerzy
Published: April 2003

Because hydrophilic copolymers containing cyanacrylate elements should be useful as components of adhesives in surgery, the conditions of grafting of ethyl α‐cyanacrylate on poly(vinyl alcohol) were studied. Two anthraquinone derivatives were applied as sensitizers in UV‐initiated grafting; 2,6‐disulfoanthraquinone sodium salt proved to be especially efficient. IR spectra and derivatograms of poly(vinyl alcohol‐g‐ethyl α‐cyanacrylate) are described.
Formation of particles in the preparation of carboxylated polystyrene latexes
Authors: Sakota Kazuyuki , Okaya Takuji
Published: April 2003

Carboxylated polystyrene latexes have been prepared by copolymerizing acrylic acid at the appropriate degree of neutralization in the absence or presence of sodium dodecyl sulfate (SDS), and the particle formation process was investigated from the number and uniformity of particles. In the absence of SDS or in a concentration range of SDS lower than 6.41 mmole/l., the formation of particles can predominantly be attributed to the precipitation of growing radicals formed in the aqueous phase; whereas in a concentration range of SDS higher than 6.41 mmole/l., the formation of particles can predominantly be attributed to the initiation of polymerization in the interior of SDS micelles containing solubilized styrene by the collision of growing radicals formed in the aqueous phase. In the former range, the number of particles increases linearly with increasing concentration of SDS below the critical concentration of 1.60 mmole/l., which is sufficient to stabilize particles formed by the precipitation of growing radicals, and remains constant above the critical concentration. The effect of initiator concentration as well as amount of styrene on the formation of particles also supports the particle formation process described above.
Method for correcting molecular weight from gel permeation chromatography. II. Long‐chain branching correction of low‐density polyethylenes
Authors: Nakano Seikou , Goto Yukitaka
Published: April 2003

Direct measurement of intrinsic viscosity on gel permeation chromatography effluent was performed with use of an automatic viscometer in order to determine molecular characteristics of branched polymers. In analyzing the viscosity data, the instrumental spreading was considered. Results obtained from three low‐density and one high‐density polyethylene were compared with those obtained by such other methods as osmometer, light scattering, and column elution fractionation.
The structure and physical properties of copolymers of lactams
Authors: Šimůnková E. , Zelinger J. , Kubánek V. , Králíček J.
Published: April 2003

Copolymers of caprolactam with caprylolactam and laurolactam were prepared by activated anionic copolymerization under adiabatic conditions, at an initial polymerization temperature of T0 = 130°C. The drop of the crystalline phase content and changes of the copolymer morphological structure depending on the content of comonomers result in increasing toughness and deformability due to enhanced yielding ability. The dependences of the copolymer structure and properties on the concentration of comonomers are different for the two series of copolymers. This results from different courses of the polymerization and crystallization history as a consequence of a large difference between polymerization rates of caprylolactam and laurolactam.
Bimodal character of polyester–solvent interactions. I. Evaluation of the solubility parameters of the aromatic and the aliphatic ester residues of poly(ethylene terephthalate)
Authors: Knox B. H.
Published: April 2003

The Hildebrand and the Hansen solubility parameters of the aromatic and the aliphatic ester residues of poly(ethylene terephthalate), PET, are evaluated and compared to those determined experimentally. The interactions of nonaqueous solvents with the aromatic and aliphatic ester residues of PET are also described in terms of their relative basicity and acidity in the Lewis sense, where the aromatic residue may be taken as a Lewis acid and the aliphatic ester residue may be taken as a Lewis base.
Ion movements in cellulose acetate membranes
Authors: Horigome Shinkichi , Taniguchi Yoshio
Published: April 2003

The behavior of ions in a cellulose acetate membrane was discussed from the standpoint of mobilities obtained from the membrane potentials. The mobilities of univalent ions larger in radius or divalent ions relative to Na+ ion mobility in the membrane are much different from those in aqueous solutions. The order of the mobilities of ions in the membrane is shown quantitatively. The mobilities of the ions with radii larger than a certain value in the membrane decrease with increase in their size. This could be explained by the physical friction between the ion and the membrane wall. This friction is of importance as the ionic radius comes close to the intermolecular gaps between polymer chains. The mobilities of Na+ anyd 1− ions in the membrane are (2–3) × 10−7 cm2/sec‐V and are about three to four orders of magnitude less than those in aqueous solutions.
Effects of atmospheric pollutants at high temperature on the adhesion of RFL‐coated tire cords to rubber
Authors: Hartz R. E. , Adams H. T.
Published: April 2003

The examination of treating oven pollutant effects on the adhesion of RFL‐coated polyester and nylon tire cord to rubber was conducted using a hot strip adhesion test. Ozone, ultraviolet light, and ozone–ultraviolet light were examined at 140°F. Nitrogen oxides, sulfur dioxide, and air were tested at 320°F. Ozone and ozone–UV (singlet molecular oxygen) systems were many orders of magnitude greater degradants than the other pollutants known to exist in the ovens. The remaining pollutants tested were ranked in order of degradation effect with NO2 > NO ≫ SO2 ≡ air ≡ heat alone. The mechanism for adhesion loss involves addition to the olefinic double bonds to reduce unsaturation sites for cure.
DSC evaluation of epoxy and polyimide‐impregnated laminates (prepregs)
Authors: Pappalardo L. T.
Published: April 2003

Differential scanning calorimetry has been applied to the study of epoxy–glass and Kerimid 601 (polyimide–glass) prepregs used in making multilayer printed wiring boards. The data generated through thermal analysis are thermodynamic and kinetic. Thermodynamic properties of B‐stage prepregs obtained are endothermal and exothermal peak temperatures, glass transition temperatures, and heats of residual cure. They were obtained from thermograms made at fixed scanning rates. Kinetic information obtained from isothermal cure scans gave rates of residual cure, cure times, and energies of activations. This information gives the process engineer useful information for controlling the processing of multilayer printed wiring boards.
Crystallinity in jute fiber as revealed by multipeak resolution
Authors: Ray P. K. , Montague P. E.
Published: April 2003

A method of multipeak resolution and computation of background scatter in x‐ray diffraction from fiber has been applied to jute fibers. While crystallinity as determined by this method in raw and delignified jute fibers remains unchanged, perfection of the crystalline regions improves on delignification.
Torsional braid analyzer measurements of polymer damping factors
Authors: Hartmann Bruce , Lee G. F.
Published: April 2003

Measurements were made in a torsional braid analyzer (TBA) and a torsional pendulum (TP) on a diglycidyl ether of bisphenol A cured with methaphenylenediamine over a broad temperature range that included the γ transition of this polymer. Based on a comparison of the results from the two instruments, we conclude that (1) the relative shear modulus measured in the TBA differs from the absolute modulus measured in the TP by a multiplicative constant that is independent of temperature in the glassy state; (2) the damping factor measured in the TBA is, at least approximately, equal to the damping factor measured in the TP, contrary to the usual assumption that only relative values are obtained from the TBA; and (3) as a result of (1) and (2), the TBA can be used to determine not only the temperature of a transition but also its activation energy.
Crosslinked poly(vinyl alcohol) hydrogels as swollen elastic networks
Authors: Peppas Nikolaos A. , Merrill Edward W.
Published: April 2003

Transparent crosslinked PVA hydrogels were prepared by electron beam irradiation of aqueous solutions under nitrogen. These weak hydrogels, upon swelling at 30°C in water, showed low elastic moduli (up to 50 psi), low ultimate tensile strength (up to 4 psi), and low extensibility to break (not higher than 85%). Values of the molecular weight between crosslinks Mc were calculated from swelling and from tensile experiments. In fact, two values of Mc were calculated for each swelling experiment, (a) allowing for observed variation in the polymer–solvent interaction parameter χ1 with concentration, and (b) fixing χ1 = 0.494 according to literature data. The correlation of the Mc obtained from tensile data with the Mc obtained from swelling data, by (a) or (b), was approximately linear and gave the same per cent agreement.
The effect of chelation on the selective transport of alkaline‐earth metal ions in asymmetric cellulose acetate hyperfiltration membranes
Authors: Lee K. L. , Hopfenberg H. B. , Stannett V. T.
Published: April 2003

The rejection of calcium and/or magnesium ion by asymmetric cellulose acetate hyperfiltration membranes is increased significantly by formation of the corresponding alkaline‐earth metal chelate. Typically solute fluxes are reduced by a factor of 5 consequent to chelation with ethylenediaminetetraacetic acid (EDTA) at pH 6.0. Selective chelation and, in turn, selective transport of magnesium is observed when equimolar solute mixtures corresponding to 1:1:1 magnesium:calcium:EDTA are hyperfiltered. Under these conditions, calcium successfully competes for the stoichiometrically limiting EDTA, and the rejection of magnesium is lower than the rejection observed for the hyperfiltration of the MgEDTA2− complex in the absence of competitive calcium. Alternatively, the rejection of the CaEDTA2− complex is increased under these identical conditions, presumably as a consequence of specific interactions between the available free magnesium and the cellulose acetate membrane. The effects reported here all seem to be related to reductions in solute diffusivity associated with the increased size of the alkaline‐earth metal ion complex.