bluuebunny/crossref_metadata_2025 huggingface dataset:
The quantitative detection of free radicals on mechanically formed polymer surfaces
Authors: Salloum Robert J. , Eckert Roger E.
Published: April 2003

Mechanochemical reactions are becoming increasingly important; yet, quantitative data on mechanoradicals are sparse. A study was undertaken to determine the surface concentration of free radicals which are available for reaction when chemical bonds are broken by mechanically forming fresh polymer surface. Polyethylene and polypropylene were cut under a benzene solution of the free‐radical scavenger diphenylpicryl‐hydrazyl, using countersinks as the cutting tools. Accurate surface area measurements of the polymer shavings were made. Surface free‐radical densities up to 2 × 1013/cm2 for polyethylene and 9 × 1013/cm2 for polypropylene were determined. The physical conditions of the test and of the cutting tool were found to have an effect on the results, but not as profound as that of base polymer.
Polymerization of benzene in a capacitively coupled RF plasma
Authors: Duval M. , Théorêt A.
Published: April 2003

The influence of various parameters on the polymerization reaction of benzene in a capacitively coupled rf plasma has been investigated, with particular emphasis on coatings structure and quality. Molecular weight distribution studies by gel permeation chromatography indicate that the degree of polymerization is mainly influenced by pressure and power. A two‐stage mechanism of polymer formation is proposed on the basis of experimental data: oligomers or polymers are first formed in the gas phase and then diffuse to the electrodes and reactor walls, where they may undergo an emulsiontype polymerization. Sputtering and pyrolysis effects are suggested to explain the additional observations on the lowest‐and highest‐pressure films.
Further studies on the action of alkali metal hydroxides on cotton
Authors: Zeronian S. H. , Cabradilla K. E.
Published: April 2003

X‐Ray diagrams revealed that the conversion of the lattice structure from cellulose I to cellulose II is substantially complete in cotton treated at 0°C with LiOH, NaOH, or KOH of approximately 5N concentration. With concentrations less than 5N, there were marked differences in the ability of these reagents to cause lattice conversions in cotton. Below a minimum concentration which is dependent on both the alkali and the treatment temperature, conversion from cellulose I to cellulose II cannot take place in cotton irrespective of the swelling caused by the reagent. We suggest that extensive swelling by one of these alkalis is not sufficient by itself to cause conversion from cellulose 1 to cellulose II and that the concentration of the alkali is of prime importance. There was no direct relation between the swelling induced in cotton by treatment with LiCH, NaOH, or KOH at 0°C and the sorption ratio of the resulting product. Also, although treatment with 5N KOH caused less swelling than that obtained with either 5N NaOH or LiOH, KOH reduced the level‐off degree of polymerization (LODP) of cotton most, indicating the importance of the size of alkali cation in reducing crystallite length. In additional experiments, cotton was treated at 21°C with a solution of 4.7N NaOH to which boric acid had been added. Although the swelling of the cotton was little affected, the addition of the boric acid caused the sorption ratio of the product to decrease, whereas the LODP increased. Also conversion of the lattice structure from cellulose I to cellulose II was inhibited.
The preparation of crystalline polypropylene sodium sulfonates and their interaction with an included sodium hydroxide phase
Authors: Huff T. , Johnson B. H.
Published: April 2003

Sodium sulfonated polypropylenes have been prepared by the slurry chlorosulfonation of polypropylene or propylene—ethylene copolymer followed by hot aqueous sodium hydroxide treatment. Low levels of excess sodium hydroxide were added to the materials to stabilize them against thermal decomposition. It was found that there was a strong interaction between the sodium hydroxide phase and the polymer sodium sulfonate groups which persisted above the nominal melting point of crystalline polypropylene. Evidence for the interaction includes an increased melt viscosity and a greatly increased nucleation rate for the composites as compared to the polypropylene sodium sulfonates not containing the sodium hydroxide phase. The composites have an improved balance of mechanical properties as compared to the materials from which they are prepared.
Thermoelastic properties of block copolymers of the polystyrene–polybutadiene–polystyrene type
Authors: Pollàk V. , Romanov A. , Marcinčin K. , Vyroubal Č.
Published: April 2003

The thermoelastic properties of block copolymers of the type polystyrene—polybutadiene—polystyrene were studied. It was found that the fu values depend on the content of styrene and the strain history as well. These relationships are discussed from the point of view of polymer structure.
Flame‐retardant cotton fabrics by reaction of cellulose with phosphorus trichloride–DMF adduct
Authors: Vigo Tyrone L. , Collins Anna M. , Welch Clark M.
Published: April 2003

Cotton sateen fabric was found to react with the 1 : 2 adduct of phosphorus trichloride and N,N‐dimethylformamide (DMF) in DMF or DMF—chloroform solutions at room temperature. During this reaction, the fabric acquired flame resistance. The introduction of as little as 1.2% phospohorus and 0.4% nitrogen, achieved at adduct concentrations as low as 2–5% in reaction times of 5–30 min, was sufficient to impart a useful level of flame retardancy. The effect of the adduct concentration, reaction time, and wash procedures on the flame resistance and other properties of the resultant cotton fabrics was studied. Moderate increases in the wet and dry wrinkle recovery were imparted by the treatment, but the use of high concentrations of adduct were somewhat detrimental to the tensile strength of the fabric. However, adduct concentrations of 20–25% produced a rather durable finish which passed the standard vertical flame test after 20 home launderings. Gradual loss of flame resistance during repeated laundering is attributable to ion exchange properties gradually acquired by the fabric. Based on analytical and in frared spectral data, the initial reaction of cellulose with the PCl3—DMF adduct is thought to involve elimination of one mole of DMF to form celluloseOP linkages, as well as some cellulose crosslinking via a second formimidate group of the adduct. Gradual hydrolysis during multiple launderings apparently yields cellulose acid phosphates responsible for the calcium ion uptake and decrease in flame resistance.
The effect of sodium hydroxide on crystallite orientation measurements in cotton fibers
Authors: Hebert Jacques J. , Muller Linda L. , Schmidt Richard J. , Rollins Mary L.
Published: April 2003

The crystallite reorientation brought about by the swelling of cotton with sodium hydroxide solution (NaOH) has been investigated. The degree of reorientation as indicated by the decreased value of x‐ray angle may arise from deconvoluting and not necessarily from a change in orientation of the crystallites within the fibrillar structure.
Viscoelastic properties of aqueous solution of methylcellulose
Authors: Amari Takeshi , Nakamura Matao
Published: April 2003

The viscoelastic properties of aqueous solution of methylcellulose were investigated using three types of rheometers, which enabled us to cover more than 8 decades of frequency range. At first, the entanglement densityX/qat various temperatures was estimated by comparingG′, andG″ curves and relaxation spectra experimentally obtained with those calculated from Hayashi's theory. At lower temperatures, the concentration dependence ofX/qwas small as observed for polyelectrolytes, but increased at higher temperatures. The same tendency was observed in the concentration dependence of the entanglement functionGeN.It is supposed that water molecules adsorbed on methylcellulose and depressing the entanglement formation dissociate with increasing temperature. The relaxation mechanism was then examined from the concentration dependences ofG′, η′, and ηo at various temperatures and frequencies. It is concluded that the structural networks in a solution become closer with increasing temperature, and the corresponding viscoelastic mechanism varies from the intermolecular interaction such as entanglements to the intramolecular motion with increasing frequency.
Gas‐Filled polymers. II. Mechanical behavior of polyethylene
Authors: Kolbeck A. G. , Uhlmann D. R. , Calvert P. D.
Published: April 2003

The mechanical properties of gas‐filled polyethylene have been studied for material with density greater than about 0.85 g/cm3. The effect of gasification on the tensile properties of both high and low density polyethylene beyond a certain critical density reduction is to cause a general weakening of the material. The yield stress falls by about 25% over the range of density investigated, while the elongation to fracture decreases by an order of magnitude. A mechanism is proposed to this weakening and for the yielding and fracture phenomena observed for gasified polyethylene.
Interpolymer from starch xanthate and polyamide–polyamine–epichlorohydrin resin: Structure and papermaking application
Authors: Carr M. E. , Doane W. M. , Hamerstrand G. E. , Hofreiter B. T.
Published: April 2003

The efficacy of oxidatively crosslinked starch xanthate for improving wet‐ and dry‐strength properties of paper prompted the present study of an alternative, interpolymeric crosslinking procedure. Sodium starch xanthate of degrees of substitution 0.05–0.25 was reacted with a commercial paper additive (a polyamide–polyamine–epichlorohydrin wet‐strength resin) which was found to contain 3‐hydroxyazetidinium chloride, epoxy‐propyl, and chlorohydrin groups (3:1:1) to give an interpolymer crosslinked by both ionic and covalent bonds. Model systems, in conjunction with nuclear magnetic resonance, infrared, and ultraviolet spectral data, served to elucidate reaction mechanisms and structures of the interpolymer and the commercial resin. Reaction conditions that favored formation of either ionic (polysalt) or covalent (xanthate ester) crosslinks were investigated. In preliminary evaluations, incorporation of the interpolymer into paper handsheets resulted in excellent wet‐ and dry‐strength improvements.
Redox sensitization in the photochromic polymers of the thionine series
Authors: Kamogawa Hiroyoshi , Hasegawa Haruo
Published: April 2003

The incorporation of electron‐donating components such as mono‐, di‐, and triethanolamines into the thionine photoredox system was tried (1) by copolymer preparations containing the acrylamidomethylthionines and triethanolamine monoacrylic ester as components, (2) by the reaction of triethanolamine and thionines with the N‐hydroxy‐methyl group in polymer in an acid medium, and (3) by the reaction of mono‐ or diethanolamine and thionines with the N‐hydroxymethyl group. The photochromic behavior incorporated into the polymer chain are as effective as their monomeric equivalents, to the extent that the sensitivity is among the highest so far investigated.
Anisotropic shrinkage of injection‐molded rubber
Authors: Nakashima Kunihiko , Fukuta Hiroshi , Mineki Minoru
Published: April 2003

The anisotropic characteristics of injection‐molded flat rubber sheets were investigated. The shrinkage and mechanical properties were measured in two directions: parallel and perpendicular to the flow direction. The results showed that (1) the shrinkage in the parallel direction is larger than that in the perpendicular direction, (2) such anisotropic shrinkage increases with the increase of vulcanization temperature and flow distance, (3) similar anisotropy was also noticed in 300% modulus, tensile strength, and elongation. Two kinds of orientation, “shear orientation” and “expanded orientation,” were observed. The former occurs by plug flow, and the latter by the expansion of the materials. The shrinkage was independent of the expanded orientation but was strongly associated with the shear orientation, while the mechanical properties were affected by the expanded orientation.
Polymer deposition onto the support in column fractionation
Authors: Ogawa Toshio , Tanaka Shoichi , Inaba Tadami
Published: April 2003

The effects of the depositing condition in column fractionation of isotactic polypropylene were studied in detail. A good fractionation was accomplished not only in selective but also in nonselective deposition. Furthermore, it was found, in opposition to Kenyon's opinion, that the polymer was not spread uniformly over the support, but deposited onto the support in the state of particles and that fractionation was not successful in the case of large particles. From these facts, the particle size is regarded as an important factor to attain good fractionation of isotactic polypropylene.
Formalized poly(vinyl alcohol) membranes for reverse osmosis
Authors: Chen C. T. , Chang Y. J. , Chen M. C. , Tobolsky A. V.
Published: April 2003

The permeation properties of formalized poly(vinyl alcohol) membranes are described. The interest of this work is centered on the properties relevant to desalination by reverse osmosis. These membranes, when properly prepared, showed reasonably high water permeability, high salt rejection, and stability in the presence of acids and alkalies.
Effect of molecular structure on polyethylene melt rheology. III. Effects of long‐chain branching and of temperature on melt elasticity in shear
Authors: Mendelson R. A. , Finger F. L.
Published: April 2003

The effects of long‐chain branching and of temperature on the melt elasticity in shear of polyethylene were investigated using die swell measurements and relating them to recoverable shear strain, normal stress, and shear modulus. Die swell measurements, as a function of shear rate, were obtained for high‐ and low‐density polyethylenes at temperatures ranging from 130° to 225°C. The samples were characterized by GPC and intrinsic viscosity for molecular weight distributions and degrees of long‐chain branching. The importance of annealing the extrudates at temperatures above the polymer melting temperature to achieve equilibrium, or strain‐free, values of die swell was demonstrated. The effect of long‐chain branch was to decrease elastic deformation. At constant shear stress, the melt elasticity of both high‐ and low‐density polyethylene was found to be essentially independent of temperature. Thus, at constant shear rate, elastic deformation decreased with increasing temperature, and it was demonstrated that this decrease could be quantitatively defined in terms of previously determined shear rate–temperature viscosity superposition shift factors.
Cured polyesters based upon bisacid A2: Water absorption, toluene resistance, and resistance to 5% aqueous HNO3 and NaOH
Authors: Lenk R. S.
Published: April 2003

Earlier papers have described the preparation and purification of bisacid A2,1,2 the preparation and cure of crosslinkable polyesters,3 the thermal properties of cast sheet,4 and the mechanical properties of glass fiber laminates5 which were made from reactants that included bisacid A2 in two series of cocondensates. The present paper details the water absorption and the long‐term effects (up to 12 months) of toluene, 5% aq. HNO3, and 5% aq. NaOH. The effects of the last two were found to be negligible, but the water absorption and the toluene resistance appeared to be capable of correlation with the known composition and the inferred structure of the copolyesters.
Reinforcement factors in fibers from block copolyamides and polyamide blends
Authors: Zimmerman J. , Pearce E. M. , Miller I. K. , Muzzio J. A. , Epstein I. G. , Hosegood E. A.
Published: April 2003

The modulus of a fiber can be increased by plying with it a higher‐modulus fiber. In this case, the modulus of the combination is characterized by a springs‐in‐parallel model, and the modulus of the composite is a linear function of the per cent of the second fiber in the composite. Another method of obtaining reinforcement is to melt‐blend a higher‐modulus polymer with the substrate polymer. With polyamides, this leads to a certain degree of amide interchange and block copolymer formation which depends on the compatibility of the polymers as well as on the usual kinetic factors. If the dispersion of the higher‐modulus polymer is such that aggregate size is relatively large (e.g., ≥500 Å) and if the adhesion between the two polymers is good, a springs‐in‐parallel‐type reinforcement is the best which can be obtained. In melt‐blend polyamides, a “nonclassical” phenomenon in reinforcement has been noted when the diameters of the dispersed aggregates are ≤500 Å and when there are a relatively high number of hydrogen bonding sites on both polymer components. In this case, it appears that moduli appreciably higher than predicted from a springs‐in‐parallel model are obtained as well as higher than expected Tg values. A mechanism is proposed to account for this “nonclassical” behavior along with data to support it. Another type of anomaly is observed when the components of the blend are isomorphous. In this case, the reinforcement is considerably less than expected.
Relations between viscoelastic parameters of hydrophobic fiber and dyeing with disperse dyes
Authors: Supanekar S. D. , Daruwalla E. H.
Published: April 2003

Experimental evidence is presented to show that the kinetics of dyeing of hydrophobic fibers with disperse dyes can be represented by an equation of the same form as the well‐known equation giving creep in fibers. A mechanism is proposed whereby one can regard the dye uptake in the fiber at a constant temperature as a viscoelastic phenomenon in the dye‐polymer system. A comparison of these two equations enables the dyeing constants to be interpreted in terms of the viscoelastic parameters of the system. It is also possible to find the upper bounds for the dyeing rate and a condition for rapid dyeing on the same basis.
Formation of an amorphous powder during the polymerization of ethylene in a radio‐frequency discharge
Authors: Kobayashi Hiroaki , Bell Alexis T. , Shen Mitchel
Published: April 2003

An investigation has been carried out to determine the influence of operating conditions on the character of the final product resulting from the polymerization of ethylene in a radio‐frequency discharge. It has been found that low pressures and high ratios of discharge power to gas flow rate lead to the deposition of a powder as well as a film. From visual observations of powder deposition, it has been possible to divide the plane formed by the axis of pressure and flow rate into a region in which powder is deposited together with a film and a region in which only a film is deposited. Numerous physical measurements have been carried out in order to characterize the powder. From these measurements, it has been concluded that the powder is a relatively dense, amorphous, and highly crosslinked polymer composed of short‐chain segments containing no more than two adjacent methylene groups. Many forms of unsaturation have been observed which, together with the high crosslink density, explain the measured hydrogen‐to‐carbon ratio of 2.7 to 2. Evidence of oxidation has been observed through the appearance of hydroxyl and carbonyl bands in the infrared spectrum of the polymer. A mechanism for the formation of the powder has been proposed which suggests that the polymerization of the powder takes place totally in the gas phase.
The influence of the stretch ratio on the rate of diffusion in a wet‐spinning process
Authors: Doppert H. L. , Harmsen G. J.
Published: April 2003

This article describes diffusion experiments on a single filament spinning set. The aim was to find phenomena which may occur in any wet‐spinning process. An alkaline poly(vinyl alcohol) solution containing an indicator was spun out into a coagulation bath containing Na2SO4, after which the filament was guided into an acidic second bath. The first bath served to deswell the filament in order to avoid contamination in the diffusion study. In the second bath the diffusion of H+ and OH− ions was studied by measuring the distance which had to be covered by the filament in order to produce a color change of the indicator at the center of the filament. The equation for cylindrical diffusion was tested at various mechanical adjustments of the spinning set. It was found that the rate of diffusion decreases with increasing stretch ratio. Moreover, the relevant diffusion equation is qualitatively very well applicable to the phenomena considered, provided the applied stretch ratio is taken into account.
Bulk polymerization of methyl methacrylate
Authors: Balke S. T. , Hamielec A. E.
Published: April 2003

This manuscript reports on an experimental investigation of the chemical‐initiated (AIBN) bulk polymerization of methyl methacrylate to limiting conversion at temperatures of 50°C, 70°, and 90°C. The change in the cumulative differential molecular weight distribution (CDMWD) with respect to conversion was measured by gel permeation chromatography (GPC). These CDMWD's were differentiated to determine the instantaneous differential molecular weight distribution (instantaneous DMWD) over the range of conversions investigated. These experimental instantaneous DMWD's were found to agree with theoretical distributions predicted by classical free‐radical kinetics over the entire conversion range and where diffusion control of the termination reactions is dramatic. A correlation of the dimensionless group α (where α = ktdRp/kp2M2) with free volume is proposed. This correlation appears to adequately account for diffusion control of the termination reaction. A kinetic model for the bulk polymerization of methyl methacrylate has been developed. This model should find use in the design, simulation, and optimization of PMMA reactors.
Block copolymers of polycarbonates with several hydroxy‐terminated elastomers to yield thermoplastic elastomers for higher service temperature
Authors: Memon Nazir A. , Williams H. Leverne
Published: April 2003

The synthesis of block copolymers and the study of their morphology were undertaken to find improved thermoplastic rubbers for service at elevated temperatures. The basis was the extraordinary properties possessed by ABA‐type block copolymers in which the terminal blocks are polystyrene and the central block is either polyisoprene or polybutadiene. In these systems it has been well established that the unusual properties are a result of domain formation in which the hard and the soft blocks aggregate separately into distinct phases. The hard segment is thought to act both as a crosslink and as a filler. Block copolymers were synthesized with different soft and hard segments. The effects of these segments and of their properties on the morphology and the stress‐strain properties of the block copolymers were measured and evaluated. Electron microscopy and birefringence were used to determine the morphology. It was found that the glass transition temperatures of the segments, the bulk of the monomer unit in the glassy segment, and the morphology determined the strength of the material. Some of the materials prepared have tensile strengths of 0.1 kg/cm2 or more at temperatures in excess of 180°C and therefore appear promising as elastomers for service at elevated temperatures.
Dynamic mechanical properties of epoxy–rubber polyblends
Authors: Kalfoglou Nikos K. , Williams H. Leverne
Published: April 2003

The dynamic mechanical properties of the epoxy resin of the diglycidyl ether of bisphenol A cured with varying amounts of a carboxyl‐terminated butadiene–acrylonitrile copolymer were determined. Isochronal measurements were made between −90° to 170°C for eight compositions. Mechanical relaxations indicate the degree of interaction and the state of mixing of the two‐phase system. Phase reversal occurs at a volume fraction of 0.5, where an intermediate compound is formed. In the low concentration range of the elastomeric phase, the impact strength improvement correlates well with an increase in the energy absorption of the relaxation. The known morphology of the system at this composition range allowed testing of various phenomenological mechanics models proposed to calculate the tensile properties of composite systems.
The structure and physical properties of anionically polymerized nylon 6 crosslinked by bislactams
Authors: Šimůnková E. , Zelinger J. , Kubánek V. , Králíček J.
Published: April 2003

Crosslinked polyamides prepared by copolymerization of ϵ‐caprolactam with bislactams under conditions of activated anionic polymerization proceeding adiabatically below their melting point show differences in physico‐mechanical properties. Owing to varying copolymerization rates of bislactams, depending on the position of the connecting bridge of the bislactam in relation to the amido group, copolymers with different morphological structure are formed. The differences in the mechanical properties of the copolymers are explained on the basis of the differences in the morphological structure. This explanation is supported by results obtained by measuring the thermal and dynamic properties.
Influence of the die entry angle on the entrance pressure drop, recoverable elastic energy, and onset of flow instability in polymer melt flow
Authors: Han Chang Dae
Published: April 2003

An experimental study has been carried out to investigate the effects of die entry angle on the entrance pressure drop, recoverable elastic energy, and onset of melt fracture in the flow of viscoelastic polymeric melts through a capillary die. For the study, capillaries with an L/D ratio of 4 and with varying die entry angles, 15°, 30°, 60°, 90°, 120°, and 180°, were used for extruding low‐density polyethylene and high‐density polyethylene. Measurements were taken of wall normal stresses along the upstream reservoir section, tapered conical section, and straight capillary section.
Molecular weight determination of high polymers by means of vapor pressure osmometry and the solute dependence of the constant of calibration
Authors: Bersted Bruce H.
Published: April 2003

Data are presented to show that the calibration constant of the vapor pressure osmometer is in fact not a constant, but rather depends on the nature of the solute. It is shown that the assumption of the constancy of the calibration constant is particularly severe when comparing low molecular weight standards and polymeric materials. A model is presented which visualizes either condensation or evaporation taking place at the solution drop surface, depending on the relative magnitudes of the concentration and Thermistor self‐heating. In terms of this model, the solute dependence of the calibration constant is attributed to the formation of a diffusion‐controlled surface concentration of the solution drop that differs from the concentration of the drop as a whole. Experimental evidence consistent with a diffusion‐controlled surface layer is given. A method based on this model is given for operating the instrument so that the solute dependence of the calibration constant disappears. When the instrument is run in this manner, Mn determinations from vapor pressure and membrane osmometry are in significantly better agreement than when the instrument is operated as recommended by the manufacturer.
Gel permeation chromatography. VIII. A study of the effect of column arrangement of resolution at normal and overloading concentrations
Authors: James P. M. , Ouano A. C.
Published: April 2003

In the determination of molecular weight distributions by GPC, the traditional column arrangement is such that the fractionation process proceeds from a high‐permeability limit to a low‐permeability limit column. We report computer comparisons of data obtained from columns in their normal ordering (high‐ to low‐permeability limit), reverse ordering, and random ordering. The columns had a permeability limit range from 1 × 106 Å down to 1 × 103 Å, and the polymers had a molecular weight range of 1.8 × 106 down to 2.1 × 103. The concentrations used varied from 0.05% up to 0.5%. The data show significantly different results, with the random arrangement the preferred ordering. A qualitative model for the separation mechanism is presented to account for the improvement in resolution. Additional data are presented which show that serious errors (as high as 45%, depending on concentration) will be encountered in GPC studies, unless the calibration curve is obtained at the same relative concentration as the samples, with definite overloading effects occurring at the higher concentrations. A new method of curve fitting was used in the higher molecular weight region to give meaningful calibration curves.
Solution polymerization of acrylamide to high conversion
Authors: Ishige T. , Hamielec A. E.
Published: April 2003

The solution polymerization of acrylamide initiated by 4,4′‐azobis‐4‐cyanovaleric acid (ACV) at high monomer concentrations in the temperature range 25–50°C has been studied. Molecular weight distributions were measured by gel permeation chromatography and by electron microscopy. Molecular weight measurements show that transfer to monomer plays a dominant role in controlling the molecular weight averages.
On some rheological phenomena of amorphous polymers
Authors: Aharoni Shaul M.
Published: April 2003

The molecular domain model for flexible macromolecules is presented in brief, and various observations are enumerated, indicating that the model holds true for the solid, melt, and solutions of different concentrations. The four forms in which the domains can exist under shear stress are then presented, and, by referring to them, such rheological phenomena as “die swell,” sudden jumps in flow rate, critical concentrations, and changes in viscosity are qualitatively explained.
Polymerization in an electrodeless glow discharge. II. Olefinic monomers
Authors: Yasuda H. , Lamaze C. E.
Published: April 2003

The rates of polymer deposition from various olefinic monomers in an electrodeless glow discharge were studied. The previously found empirical relationship (with styrene in part I) between the rate of polymer deposition R, the monomer pressure pM, and gas pressure px in a steady‐state flow system (i.e., R = a(pM)2 [1 + b(px)], R being nearly independent of the discharge power) was also found with all monomers investigated. (The effect of gas was examined with nitrogen in this study.) However, it was found that the polymer deposition is controlled by the monomer flow rate and Ro (in pure monomer flow) is proportional to the flow rate of monomer Fw (based on the weight); i.e., Ro = kFw, where k is a characteristic rate constant of the polymerization. Olefinic monomers can be generally classified into two major groups, i.e., type A monomers which predominantly polymerize, and type B monomers which decompose in a glow discharge. Type B monomers have smaller values of a and k compared to type A monomers. The values of a and k for type A monomers both increase with increasing molecular weight of the monomer. The values of k for all monomers investigated are within roughly an order of magnitude, indicating that the reactivity levels of monomers are very similar in a glow discharge polymerization.
Terpolymers. III. Isochronal viscoelastic parameters for terpolymers of vinyl stearate, vinyl acetate, and vinyl chloride
Authors: Jordan Edmund F. , Riser George R. , Artymyshyn Bohdan , Wrigley A. N.
Published: April 2003

Isochronal viscoelastic parameters were collected for many of the copolymers, terpolymers, and diluent mixtures whose mechanical properties at ambient temperatures were reported in the preceding paper. In the polymeric systems, vinyl stearate, acting as the primary internal plasticizer, was introduced into terpolymers by displacing vinyl acetate from base copolymers of vinyl acetate and vinyl chloride, across the range of composition. In the diluent mixtures, poly(vinyl chloride) was plasticized by di‐2‐ethylhexyl phthalate across the range of compositions. For direct comparison with the mixtures, vinyl chloride was plasticized by copolymerization with vinyl stearate across the same range of compositions. Moduli for the co‐ and terpolymers reached the low values characteristic of soft materials at room temperature only through a short range of vinyl stearate composition. At higher internal plasticizer compositions, side‐chain crystallization stiffened the samples and raised their moduli. In contrast, moduli for the mixtures decreased steadily with increase in diluent at ambient temperature. The effective use temperature ranges were narrow for the co‐ and terpolymers but broad for the mixtures. Curve broadening was similar for both types of systems, but reached a maximum at about 40 weight‐% plasticizer for the diluent mixtures. The slopes of the glassy modulus with decreasing temperature at 50°C below Tg for the vinyl stearate copolymers were relatively large. However, moduli close to that of poly(vinyl chloride) were reached only near the temperature range associated with the γ‐transition. Consequently, this behavior was attributed to motions of the side chains in the glassy matrix. Room temperature moduli, which could be obtained before the onset of melting, were correlated with the fractional side‐chain crystallinity for polymers having a high vinyl stearate content. From this relation, the modulus for the hexagonal crystal form of the side‐chain crystallites of poly(vinyl stearate) was estimated to be 1.2×1010 dynes/cm2. Moduli for the glassy amorphous phase of this same polymer appeared to have one sixth of this value at 40°C below the glass transition. The glass transition temperature occurred about 10° below the inflection temperature at 109 dynes/cm2, as an average for all of the systems studied.
Molecular weight distributions of standard polystyrene samples by GPC and by sedimentation velocity analysis
Authors: Tung L. H. , Runyon J. R.
Published: April 2003

In precision gel permeation chromatographic (GPC) work, the spreading (zone spreading) characteristics of the instrument must be calibrated. Standard samples of anionic polystyrene have been used for this purpose. The molecular weight distributions of these standard samples, nevertheless, have not been determined carefully. In this work, several standard polystyrene samples obtained from Pressure Chemical Company were examined by GPC and by sedimentation velocity analysis. The results show that (1) the high molecular weight polystyrene samples have skewed molecular weight distributions as has been suspected and that (2) the present data treatment technique for GPC is effective for these very narrow‐distribution samples.
Thermal conductivity of polymer melts
Authors: Ramsey J. C. , Fricke A. L. , Caskey J. A.
Published: April 2003

Thermal conductivities were measured for melts of a series of polypropylene and a series of polyethylene samples that had been characterized by GPC. Results indicate that thermal conductivity depends upon the molecular weight distribution and degree of branching of the polymers. The results of this work can probably be used to predict the thermal conductivity of a commercially available polypropylene or polyethylene to within 25%.
Thiolation of starch and other polysaccharides
Authors: Trimnell D. , Shasha B. S. , Doane W. M. , Russell C. R.
Published: April 2003

Thiolated starches with a degree of substitution of 0.01–0.6 were obtained by pyrolysis of starch dithiobis(thioformates) followed by saponification. The pyrolytic decomposition of dithiobis(thioformates) followed two pathways: (1) to thionocarbonate , carbon disulfide, and sulfur, and (2) to dithiocarbonate , carbonyl sulfide, and sulfur. Only the second pathway affords thiolation. Thiol groups were determined by Ellman's reagent, by sulfur analyses, and, following acetylation, by the ratio of O‐acetyl versus S‐acetyl absorption in nuclear magnetic resonance spectra. The poly‐saccharides cellulose, dextran, and xylan were thiolated by the same procedure.
Predicting solubilities of vinyl polymers
Authors: Manning A. J. , Rodriguez F.
Published: April 2003

Accurate solubility limits of polymers are best expressed by molecular weight fractionation curves. Individual curves may be obtained for each polymer–solvent (–nonsolvent) system. A method for predicting solubility behavior, based on solubility parameter δ and hydrogen bonding index γ, is proposed here. The correlation is of the form

where [η] = intrinsic viscosity of precipitated polymer; T = absolute temperature; (v.f.) = volume fraction of solvent; R = (δs − δn) − 0.3(γs − γn); Q = (γp − γe)2.2/(δp − δe); p refers to polymer; s refers to solvent; n refers to nonsolvent; e refers to solvent system at theta temperature; and a,b,c, and k are fitted constants. The correlation was derived from data for poly(vinylpyrrolidone) and polyacrylamide. It probably is limited to systems in which the precipitate occurs as a liquid.
Diffusion of water and caprolactam in nylon 6 melts
Authors: Nagasubramanian K. , Reimschuessel H. K.
Published: April 2003

The diffusions of both caprolactam and water from nylon 6 melts have been measured using a semiinfinite geometry. The process involving diffusion and chemical reaction was analyzed utilizing Higbie's penetration model and known kinetic data. The caprolactam and water diffusion coefficients are, respectively, 8 × 10−8 and 2.5 × 10−4 cm2/sec. Using the data, molecular weight profiles were obtained for both semiinfinite and cylindrical geometries as a function of melt depth and time.
Effect of blending on the rheological properties of polystyrene
Authors: Harris Everette K.
Published: April 2003

Experimental non‐Newtonian viscosity, primary normal stress difference, complex viscosity, and shear stress relaxation were taken for highly fractionated polystyrene in Aroclor 1248 (a chlorinated biphenyl) as well as for blends differing in molecular weight and concentration. The data are described by three parameters: a zero‐shear rate value, the slope of the log–log plots in the high shear rate region, and a time constant defined as the inverse of the shear rate at the intersection of the low and high shear rate asymptotes. For the functions measured, the low shear rate region is characterized by a dependence on Mw and the high shear rate region by a dependence on Mn. Implications to polymer processing are discussed.
Bending stress relaxation and recovery of wool, nylon 66, and terylene fibers
Authors: Chapman B. M.
Published: April 2003

The bending stress relaxation and subsequent recovery behavior were determined for merino wool, nylon, and Terylene fibers. The effect of four experimental parameters were investigated, viz., the level of bending strain (0.5–4%), the time of stress relaxation before release (1–1000 min), the relative humidity (0–85%), and the temperature (20°–60°C). For small strains the merino and nylon fibers displayed behavior characteristic of linear viscoelastic materials, while Terylene exhibited a degree of nonrecoverable set. It was possible to construct master recovery curves for fibers held bent for different times before release. These curves can be used as a more convenient means of presenting the results. A relationship was found, for each fiber type, between the percentage stress relaxation and the time taken to recover to a given level of set. This relationship appeared to be independent of the experimental conditions employed. Although the fibers were not linear viscoelastic under all conditions, recovery could be roughly predicted from their stress relaxation behavior at the particular test conditions using the Boltzmann superposition principle.
Determination of the diffusivity of n‐pentane in polystyrene bead foam
Authors: Fossey D. J. , Smith C. H.
Published: April 2003

The amount of residual n‐pentane in expandable polystyrene bead foam (PSBF) has an effect on the strength and dimensional stability of the foam. Data were needed to determine how fast the residual n‐pentane could be removed to enhance the properties of PSBF. An experiment was designed to determine the diffusivity of n‐pentane through PSBF at various temperatures. Mathematical models based on the appropriate diffusion differential equations were then used to predict n‐pentane concentrations in in cylinders of PSBF. The diffusivity of n‐pentane through PSBF was found to have a magnitude of 1×10‐8 to 1×10−6 cm2/sec and to vary with temperature, foam density, n‐pentane concentration, and foam structure.
Concerning the microstructure of dry‐RO membranes
Authors: Kesting R. E.
Published: April 2003

The microstructure of cellulose acetate reverse osmosis membranes which have been prepared by the Kesting dry process has been elucidated with the aid of scanning and transmission electron microscopy. The dry‐RO membranes consist of three layers: skin, transition layer, and substructure. The gel morphology of each of these layers originates in its sol precursors within the nascent membrane which manage to survive the sol → gel transition intact. The dense skin layer is composed of aggregates of tiny, slightly ellipsoidal nodules which are believed to be paracrystalline in nature. Immediately beneath the skin lies the transition layer, a narrow band of intermediate density consisting of widely separated closed cells. Below the latter lies the porous substructure which is composed of micrometer‐sized, open‐celled voids. Because of the size of their substructural voids, dry‐RO membranes are able to reversibly undergo wet–dry cycling without densification and loss of permeability.
The ferric hydroxide/hydrazine system as an initiator of vinyl polymerization
Authors: Brown C. W. , Longbottom H. M.
Published: April 2003

The reaction between ferric hydroxide and hydrazine was used to initiate the solution polymerization of methyl methacrylate. Polymerization occurs readily at pH > 6, over a wide range of iron concentration and of temperature. The initiation reaction appears to be of heterogeneous nature, like those in similar metal hydroxide/hydrazine systems.
The physical limits of grafting in two‐phase polymerization reactions
Authors: Rosen S. L.
Published: April 2003

When rubber‐reinforced thermoplastics are produced, conversion of monomer to glassy polymer takes place in two thermodynamically incompatible phases. Regardless of the chemical nature of the grafting process, monomer which is converted in the glassy phase can never be grafted to rubber simply because it is never in contact with rubber. A simple model has been developed which describes quantitatively the upper limit of grafting arising from the physical nature of the process as a function of conversion and monomer‐to‐rubber ratio in the charge.
The chemistry of fast‐curing phenolic adhesives. II
Authors: Tiedeman G. T. , Sanclemente M. R. , Smith H. A.
Published: April 2003

Novolak‐like materials have been prepared by reaction of phenol–formaldehyde resoles with aromatic amines. The hydroxymethyl groups present in resoles react with the ring carbons and the amino groups of the aromatic amine. Proportions of the two types of product vary with the amine used.
A new technique for thermal analysis of vapor‐producing reactions
Authors: McCarter R. J.
Published: April 2003

An apparatus was developed for measuring the rate at which vapors are evolved during the thermal degradation of materials and thereby deriving the kinetics of such reactions. Requisite to the operating scheme of the apparatus is the provision of a high‐temperature zone to convert condensable or tarry vapors into noncondensable form. The apparatus yields a direct measure of reaction velocity, rather than the integrated indication obtained with thermogravimetric analysis. This simplifies the identification and calculation of kinetic parameters. Increases in sensitivity and operating range are also achieved. Flexibility in operation is obtained that permits the separate recording of reactions that tend to overlap. Although the apparatus principally has been operated using a combustible gas indicator to meter the evolved vapors, a number of options are available for the latter function, including flowmeters and various continuous gas analyzers. The applicability of the method appears promising.
The stability of solutions in reactive monomers of crosslinkable polyesters containing bisacid A2
Authors: Lenk R. S.
Published: April 2003

Earlier papers1–6 have dealt with the synthesis and purification of bisacid A2; the preparation of unsaturated polyesters by cocondensing bisacid A2 with maleic anhydride in varying proportions in the presence or absence of phthalic anhydride as a further modifying acid, using propylene glycol as the polyesterification diol; the hardness and the thermal and mechanical properties of cast, cured resins and glass fiber‐reinforced laminates; and the water and chemical resistance of the cured resins. This paper deals with the solution stability of the liquid resins prior to cure and, in particular, with the observed fact that solutions containing esters of bisacid A2 in sufficient quantity do not require the addition of stabilizers commonly needed for commercial polyesters in order to impart an acceptable shelf life to the liquid resins.
The determination of the amount of bound water within cellulosic gels by NMR spectroscopy
Authors: Carles J. E. , Scallan A. M.
Published: April 2003

It has been shown that the NMR spectrum of moist cellulose is consistent with the idea that part of the water within the gel is destructured and bound to the accessible surfaces. A method for calculating the amount of bound water is presented, but because of experimental difficulties in obtaining an exact value for the spin‐spin relaxation time of the protons in the bound water, only upper limits can at present be obtained for the amount of bound water. Accordingly, it is estimated that the amount of bound water does not exceed the following values: wood, 0.23 g/g; cotton, 0.15 g/g; two wood pulps, 0.30 and 0.33 g/g. The amount of bound water appears to approximate to a monomolecular layer upon all accessible surfaces, which suggests that the NMR technique might be used to determine the surface areas of the gels in the wet state.
The thermal degradation of model compounds of amine‐cured epoxide resins. I. The thermal degradation of 1‐(N‐ethylanilino)‐3‐phenoxypropan‐2‐ol
Authors: Paterson‐Jones J. C. , Percy V. A. , Giles R. G. F. , Stephen A. M.
Published: April 2003

The thermal degradations of 1‐(N‐ethylanilino)‐3‐phenoxypropan‐2‐ol in an inert atmosphere, in air, and over alumina were studied with the aim of investigating the thermal stability of the cure linkage in aromatic amine‐cured bisphenol A‐based epoxide resins. Degradation products were characterized. Possible degradation mechanisms are outlined and are related to the results of previous studies of the thermal degradation of these resins.
The thermal degradation of model compounds of amine‐cured epoxide resins. II. The thermal degradation of 1,3‐diphenoxypropan‐2‐ol and 1,3‐diphenoxypropene
Authors: Paterson‐Jones J. C. , Percy V. A. , Giles R. G. F. , Stephen A. M.
Published: April 2003

The thermal degradations in an inert atmosphere, in air, and over alumina of 1,3‐diphenoxypropan‐2‐ol and 1,3‐diphenoxypropene were studied with the aim of investigating the thermal stability of the glyceryl portion of bisphenol A‐based epoxide resins. Degradation products were characterized. The thermal stability of the glyceryl group relative to that of the cure linkage in aromatic amine‐cured epoxide resins is discussed.