bluuebunny/crossref_metadata_2025 huggingface dataset:
The design and application of an automatic endless‐belt polymer fractionator
Authors: Blair David E.
Published: April 2003

The automatic endless belt polymer fractionator utilizes a continuous application and multistage extraction technique. A thin coating of polymer deposited on a slowly moving endless belt which passes through a series of solvent–nonsolvent mixtures of increasing solvent strength is fractionally dissolved. Discussion includes the description of the construction of the apparatus, details and results of fractionations of Neoprene W and polytetramethylene ether glycol, fractionation techniques and subsequent work‐up of the fractions, “large scale” preparative fractionations, and general performance characteristics.
Remarks on copolymer sequence distributions
Authors: Strate Gary Ver
Published: April 2003

Distribution functions for the unit X in copolymers of the type
equation image
are given. These functions have been used to calculate the expected degree of crystallinity using the Flory theory of copolymer crystallinity. The calculations indicate that differences can be expected between polymers prepared from XA and XX on the one hand and A and X on the other when the kinetics constants of the polymer‐forming reactions are identical. In addition, it has been shown that the Flory results carry over to the terpolymer case with the propagation probability given in its terpolymerization form. The addition of more than one comonomer can lead to increased or decreased crystallinity with a given constant melting point, depending on whether the noncrystallizable monomers tend to alternate or “block” with one another.
Kinetics of autoxidation of atactic polypropylene by infrared spectroscopy
Authors: Jadrnicek B. R. , Stivala S. S. , Reich Leo
Published: April 2003

The autoxidation of a film of atactic polypropylene was studied by means of infrared spectroscopy. Reaction temperatures varied from 110°C to 135°C and oxygen concentrations, from 5% to 100% by volume. A general reaction scheme previously reported for the autoxidation of polyolefins was utilized for atactic polypropylene. Various results obtained for this polymer were compared with those previously reported for isotactic polypropylene.
Oligomer of o‐xylene as a heat stabilizer for isotactic polypropylene
Authors: Boor John
Published: April 2003

Oligomers of o‐xylene (molecular weight ∼400) have been shown to be novel heat stabilizers for isotatic polypropylene film. In contrast to unstabilized films which failed after exposure of 5 hr in a 150°C air oven, a film containing 0.5 and 1.0 wt‐% of the o‐xylene oligomer survived 100 and 226 hr, respectively. Furthermore if 0.25% dilauryl thiodipropionate (DLTP) was also present, only 0.1 wt‐% of the o‐xylene oligomer was necessary to maintain a film intact up to 124 hr. In absence of DLTP, this low level of o‐xylene oligomer was not effective. Oligomers of toluene, m‐xylene, p‐xylene, and 1,2,4‐trimethyl benzene were found less effective.
Effects of aluminum ionomer surface layers on polymer properties
Authors: Otocka E. P. , Sharpe L. H.
Published: April 2003

Bulk samples of carboxylic acid containing copolymers may be treated with solutions of aluminum isopropoxide, Al(OC3H7)3, to produce ionically gelled surface layers. The behavior of treated specimens is different from that of untreated specimens in tests which measure friction coefficient, stress crack resistance, and tensile strength. In several instances the results are compared to those produced by CASING, another technique for producing crosslinked surface regions.
A method for determining boron in cotton fabric
Authors: Liepins R.
Published: April 2003

A technique involving radiofrequency‐discharged oxygen has been demonstrated in the analysis for boron in cotton fabric as well as preparation of residual ash replicas of identical three‐dimensional configuration of the original sample for microscopic studies. The main advantages of this technique lie in its simplicity and fastness.
Graft copolymers of starch and poly(2‐hydroxy‐3‐methacryloyloxypropyltrimethyl‐ammonium chloride). Preparation and testing as flocculating agents
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E.
Published: April 2003

The title monomer (I) has been graft polymerized onto whole wheat starch with both ceric ammonium nitrate and ferrous ammonium sulfate–hydrogen peroxide initiation. Three graft copolymers, which contained 4.5, 12.1, and 15.2% grafted poly(I), were characterized as to molecular weight of grafted branches and grafting frequency. Graft polymerization was proved by fractional precipitation. Graft copolymers were tested as flocculating agents for diatomaceous silica and nonmagnetic iron ore. The graft copolymers with 12.1 and 15.2% grafted poly(I) compared favorably in flocculating ability with a commercial high molecular weight cationic polyacrylamide.
Decay of free radicals in irradiated PMMA at high pressures studied by ESR
Authors: Szőcs F.
Published: April 2003

The decay of free radicals in irradiated PMMA subjected to high pressures has been studied by the method of ESR. The rate constants and activation energies has been determined for the decay of free radicals at the pressures of 5000 and 10,000 atm over the temperature range of 100–170°C. It has been found that the rate of decay was reduced essentially by the effect of high pressure. The mechanism of the decay of free radicals in solid polymers is being discussed. The important influence of the motion of macromolecule segments on the course of radical reactions in solid phase is printed out.
Cryogenic relaxations of polystyrene and poly(fluorinated styrenes)
Authors: Armeniades C. D. , Baer Eric , Rieke J. K.
Published: April 2003

The effect of structural and morphologic modifications of styrene and fluorinated styrene polymers on their internal friction was studied by means of a free‐oscillating torsional pendulum at temperatures from 300° to 4.2°K and frequencies of 1 to 2 Hz. Atactic and isotactic polystyrene gave the previously observed δ and β′ loss peaks at 38° and 100°K, respectively. These losses decrease in intensity with crystallinity in isotactic polystyrene but remain relatively unchanged in uniaxially drawn atactic polymer. Atactic polypentafluorostyrene showed an intense δ loss peak at 52°K and a broad shoulder around 100°K, which extends toward the β′ relaxation. In poly‐α,β,β‐trifluorostyrene, the δ loss peak is largely suppressed, the logarithmic decrement showing only broad maxima at 22° and 100°K. Plasticization of atactic polystyrene with 2% mineral oil gives rise to a sharp loss maximum at 100°K, which does not occur in the pure atactic polymer.
Examination of a master curve method of characterizing steady‐state flow of polymers
Authors: Nakajima Nobuyuki
Published: April 2003

Master curve methods or superposition techniques are rather widely used for characterizing the steady‐state flow behavior of polymers. One method, developed by Sabia,1 is examined with respect to its applicability and limitations. In the original development of the method, it was assumed that a universal curve (master curve) exists. Based on this, a theoretical explanation was presented for the sample parameters. Such explanation became dubious because experimental evidence was found later to nullify the master curve assumption.2,3 In this paper, Sabia's method is treated as a curve‐fitting procedure to represent observed data. In order to do so, the shear rates of observation must be limited to two or two and a half decades. Also, the range of shear rates are defined from 1 to 1000 sec.−1 The results of curve fitting and molecular interpretation of the parameters are presented.
Development of chlorendic anhydride‐cured epoxy systems with wide variations in the resin: Anhydride ratio
Authors: Levy M. F. , Canestaro M. J.
Published: April 2003

Using the epoxy resins Epon 828 (diglycidyl ether of bisphenol A) and DEN 438 (an epoxylated novalak) with chlorendie anhydride as the curing agent, a series of formulations were developed having a very wide range in the anhydride: resin ratio (40–160 phr). This range was made possible by the use of metal chelate catalysis. While these systems were not evaluated for fire retardancy, it is anticipated that they would exhibit this property dependent on their chlorine contents.
Non‐Newtonian flow and the steady‐state shear compliance
Authors: Prest W. M. , Porter Roger S. , O'Reilly J. M.
Published: April 2003

A survey of viscoelastic data on amorphous polymer melts indicates that the steady‐state shear compliance, Je, of many systems can be approximated from a knowledge of their flow response. For systems with monomodel molecular weight distributions, the absolute value of the reduced complex viscosity, η*/η0, is found to equal 0.67 ± 0.03 at the frequency ω, where ωη0Je = 1. This result applies to a variety of polymer systems and to a wide range of molecular weights and distributions as long as the highest molecular weight dispersion of the distribution constitutes more than 20 weight per cent of the sample. This relationship determines Je from non‐Newtonian flow data and thus provides a consistent way to relate differently shaped reduced variable curves and to calculate compliances from characteristic times reported in the literature. The connection between some commonly used times and Je is given. The method of calculating Je is successfully applied to capillary measurements of melt viscosities and to characteristic times determined from steady‐state shear measurements of concentrated polymer solutions.
Amine‐catalyzed polymer encapsulation of cotton fibers by vapor phase application of formaldehyde
Authors: Goswami J. C. , Brenner W. , Rugg B. , Liu W.
Published: April 2003

A process for encapsulating cotton fibers in the form of woven clothes at ambient temperatures with polyoxymethylene is described. It involves pretreatment of the cotton with a carbon tetrachloride solution of tributylamine and diphenylamine to deposit the basic catalyst on the surface of the fibers. Subsequent exposure to dry, purified vapors of monomeric formaldehyde at 25°C results in the encapsulation of individual fibers with high molecular weight polyoxymethylene. The process is relatively fast (30% fiber weight gain in approx. 20 min) with the polymer located only at the fiber surfaces. Fiber cementation does not become pronounced for weight increases below approximately 60%–65% based upon the weight of the fibers. Thickness of the polymer sheath increases with the time of the polymerization reaction. Because of the uniformity of the polymer layer deposition, the encapsulated cotton cellulose fibers can be expected to exhibit substantially different physical and chemical surface properties even at low polymer add‐on. The tensile and tear strengths of the polyoxymethylene‐encapsulated cotton fibers are generally improved, with some gains in abrasion resistance also noted. Differential staining techniques and polarized light microscopy have shown the location and uniformity of the polymer sheaths.
Graft polymerization of 1,1‐dihydroperfluorobutyl acrylate onto cellulose fabric
Authors: Watanabe Haruhiko , Chiba Akira , Tuchida Toshio , Kobayashi Yoshio
Published: April 2003

1,1‐Dihydroperfluorobutyl acrylate was prepared and grafted onto cellulose fabric by means of γ‐ray preirradiation to produce oil and water repellency. A 2% grafting was sufficient to impart oil and water repellency to cellulose fabric. In the case of 19.1% or 29.4% grafted fabrics, the grafting decreased rapidly with laundering, and the laundered fabric which possessed no oil and water repellency still had about 10% grafting of the perfluoro compound. Thus, the apparent graft polymerization takes place both on the surface and in the inner structure of the cellulose fiber; the polymer grafted onto the surface imparts oil and water repellency and is easily removed by laundering, whereas the polymer grafted onto the inner structure is hardly eliminated but does not impart oil and water repellency to the fabric.
A theoretical study of liquid‐film spread heights in the calendering of newtonian and power law fluids
Authors: Brazinsky I. , Cosway H. F. , Valle C. F. , Jones R. Clark , Story V.
Published: April 2003

The relationship between spread height and upstream reservoir thickness, with power low coefficient as parameter, was obtained analytically. At all values of n studied, the value of r (ratio of spread height to nip width) increases with increasing values of H/ho where H is upstream reservoir thickness and ho is nip width. At higher values of H/ho, the curves of r, versus H/ho tend to “flatten” out, and r approaches an asymptotic value. For example, the asymptotic value of r for Newtonian fluids (power law constant of 1) is 1.226. Asymptotic values of r increase with decreasing values of the power law constant.
Morphology and structure of silica agglomerates in silica‐reinforced silicone rubber
Authors: Galanti A. V. , Sperling L. H.
Published: April 2003

Light‐scattering and optical microscope observations of silica‐reinforced silicone rubber have shown that the filler is dispersed in a complex manner. Much of the original material appears agglomerated into particles several microns in size. These particles apparently further cluster to form agglomerates of about 20 μ in diameter. In an earlier paper in this series it was shown that the thermodynamic function fe/f (the fraction of the retractive force due to internal energy changes) was a measure of the reinforcement level. It is now proposed that the corresponding physical mechanism of reinforcement may have its origin in the large amounts of energy required to deform the filler particle agglomerates.
The effect of internal temperature rise on the tensile behavior of polymeric materials at subambient temperatures
Authors: Skelton J. , Freeston W. D. , Schoppee M. M.
Published: April 2003

The tensile properties of nylon, Dacron, and Nomex yarn are given at liquid helium temperatures, −450°F, and at two strain rates, 1.67 and 3000%/sec. The data are compared to similar results obtained at −320°, −109°, and 70°F. A theoretical analysis of the thermodynamics of straining under both isothermal and adiabatic conditions is presented, and theoretical maximum temperature rises occurring within both adiabatically and isothermally strained yarns are given for a range of subambient test temperatures. The initial modulus of the yarns increases, the tenacity increases, and the breaking elongation decreases with decreasing temperature at the lower rate of straining. However, at the higher rate of straining, although the initial modulus of the yarns at −450°F is considerably greater than the modulus at −320°F, the nylon yarn shows a lower breaking load and greater breaking elongation at −450°F than at −320°F. The Dacron follows the expected trend with the breaking load higher and the breaking elongation smaller at −450°F than at −320°F. The Nomex has a lower breaking load, but its breaking elongation is also lower at −450°F than at −320°F. The calculated yarn internal temperature rises are sufficient to explain these differences in the stress–strain behavior of the yarns.
Viscoelastic behavior of interpenetrating polymer networks: Poly(ethyl acrylate)–poly(methyl methacrylate)
Authors: Sperling L. H. , George H. F. , Huelck Volker , Thomas D. A.
Published: April 2003

The creep behavior of a series of poly(ethyl acrylate)–poly(methyl methacrylate) interpenetrating polymer networks was investigated. For comparison purposes, some stress relaxation data were included. Master curves containing a single broad transition covering approximately 20 decades of time were found for midrange compositions. Although the time–temperature superposition principle and the WLF equation should not strictly apply, reasonable agreement was found over a large portion of shift factor versus temperature plots. Application of a modified Tobolsky‐Aklonis‐Dupre glass–rubber theory suggested that the breadth of the transition could be attributed to a near continuum of phase compositions in the material, each phase composition making its specific contribution to the relaxation spectrum. Whether or not these phase regions are so small as to arise from random concentration fluctuations in an otherwise compatible polymer pair remains unknown.
Thermal runaway of nylon 6–10 during drawing under constant load
Authors: Kramer Edward J.
Published: April 2003

Anhydrous nylon 6–10 filaments were cold drawn (by propagation of a preexisting neck) under constant load. The extension rate i, which is proportional to the neck velocity, was observed to be a continuous function of the load up to a certain critical extension rate ic above which i increased discontinuously (“runaway”) by approximately two orders of magnitude. If the filaments is in N2 gas, ic ≃ 0.4 cm/min, whereas if it is in He gas, ic ≃ 1 cm/min. The structure of the drawn filament produced by runaway is an opaque, microvoid structure which, after a suitable change in load, forms first in the center of a filament and spreads toward the surface. This instability is attributed to the heating of the shoulder of the neck during neck motion. An analysis based on the measured activation enthalpy for neck motion and the thermal properties of nylon and the gas is used to predict ic values that are in rough agreement with experiment.
Graft copolymerization to cellulose in the presence of hydrogen peroxide with ultraviolet irradiation
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

The decomposition of hydrogen peroxide in the presence of cellulose with ultraviolet irradiation and graft copolymerization occurring upon addition of methyl methacrylate to this system was investigated. Graft copolymerization barely began in the hydrogen peroxide system without ultraviolet irradiation, but was markedly accelerated by ultraviolet irradiation. Ultraviolet light is capable of initiating the graft copolymerization even without addition of hydrogen peroxide, and this capability is enhanced further with the use of hydrogen peroxide. However, an increase in the hydrogen peroxide concentration was observed to exercise a zero or negative effect on the number of grafts. Such a phenomenon is absent in the ceric ion initiator system and, in the present study, is believed to be brought about by a characteristic enhancement of the stabilization of grafting sites effected by hydroxyl radicals. The number of grafts of copolymers obtained in the present initiator system is only approximately 0.085 mmole/100 g of cellulose at its maximum and is within the range of results obtained for the hydrogen peroxide initiator system in general.
The manganic hydroxide–hydrazine system as an initiator of vinyl polymerization. II. The emulsion polymerization of methyl methacrylate
Authors: Brown C. W. , Longbottom H. M.
Published: April 2003

The reaction between hydrazine hydrate and manganic hydroxide has been studied as an initiator for the emulsion polymerization of methyl methacrylate. The system has proved to be effective, and polymerization occurs at favorable rates over a wide temperature range extending from below 10°C to over 50°C. The pH range, however, is rather limited, the most effective value being 9. The main features of the initiator's behavior are similar to those found previously in the corresponding solution polymerization and are explained on the basis of a surface reaction between the hydrazine and the insoluble hydroxide. A complicating feature is the reaction between hydrazine and monomer, which exerts an inhibiting influence.
The adiabatic compressibility of poly(acrylic acid) and polyacrylamide in aqueous solution
Authors: Roy‐Chowdhury Phanibhusan , Kale Kalidas M.
Published: April 2003

The results of adiabatic compressibility measurements of poly(acrylic acid) and polyacrylamide along with their corresponding monomers and two poly(sodium acrylates) obtained by neutralizing the polyacid 25% and 100% with sodium hydroxide have been described. The total adiabatic compressibility of poly(acrylic acid) solution is higher than that of the corresponding salt solutions or of polyacrylamide solutions. The unneutralized acid does not dissociate much, even in dilute solution, and the magnitude of electrostriction in polyamide is greater than in acid. The ΦV2 and ΦK2 values for monomers and polymers are seen to be almost concentration independent, and so are the sodium salts of the polyacid. Poly(acrylic acid) and poly(acrylamide) are structurally closely related polymers, and water must be bound to them through polar groups either by hydrogen bonding or by dipole attraction. The hydrophobic part of the solute, because of compact orientation of water and solute in the boundary region, causes a decrease in solvent volume and therefore in the values of ΦV2 and ΦK2. On the other hand, intermolecular hydrogen bonding between the polar groups increases the volume and counterbalances the hydrophobic effect. Because of these two counteracting effects, the observed ΦV2 and ΦK2 values are seen to be concentration independent. Contrary to the observation with poly(methacrylic acid)1 and its sodium salts, the solvated counter‐ions in case of poly(sodium acrylates) make no special contribution in the dilute region. In 100% neutralized polyacid, the dissociation of counterions is complete, and the magnitude of electrostriction is highest in this case. Accordingly, lowest ΦV2 and ΦK2 values (37.0 cc/mole and −50.50 × 10−3 cc bar−1 mole−1) are observed. However, the dissociation and therefore the magnitude of electrostriction are somewhat reduced in the presence of 1.0M NaCl solution; and, accordingly, the values increase to 42.80 cc/mole and −33.0 × 10−4 cc bar−1, mole−1, respectively. The limiting values for the apparent molal volume and the apparent molal compressibility for the polymers show a considerable decrease over those of the monomers. The values of ΦV20 and ΦK20 per methyl group are less in the polymers than in the monomers, and this has been attributed to water clusters that become stronger and better formed as the molecules grow larger and larger. The molar volumes of acrylic acid and methacrylic acid are decreased, while those of acrylamide and methacrylamide are increased when dissolved in water to form an infinitely dilute solution.
Thermal analysis of poly (vinyl chloride) fractions
Authors: Varma I. K. , Grover S. S.
Published: April 2003

The thermal stability of commercial poly(vinyl Chloride) and its four fractions having different intrinsic viscosities (1.152–0.397 dl/g) has been investigated thermogravimetrically in the presence of atmospheric oxygen, up to a temperature of 400°C, by using the nonisothermal technique. The results indicate that the thermal stability of the polymer is inversely proportional to its intrinsic viscosity. The kinetic parameters have been evaluated for the early stages of decomposition (2% to 20%). The results have been explained on the basis of different structures of the polymer chain in fractions of high and low intrinsic viscosity.
A study of fiber extrusion in wet spinning. I. Experimental determination of elongational viscosity
Authors: Han Chang Dae , Segal Leon
Published: April 2003

Elongational viscosities were measured in a wet‐spinning apparatus. The advantage of this procedure lies in the fact that excellent temperature control can be maintained and that gravity effects can be neglected for a horizontally spun fiber. As a spin dope, an aqueous solution of polyacrylonitrile (PAN) consisting of approximately 10% polymer and 40% sodium thiocyanate (NaSCN) was spun into a coagulating bath of varying NaSCN content, up to a concentration at which spinning was no longer feasible. Fiber diameters were measured photographically as a function of distance from the spinnerette. Spinning tension readings were made on a multifilament bundle using a calibrated tensiometer. To eschew the influence of the hardening effect arising from mass and heat transfer, the temperatures of the spin dope and coagulating bath were kept constant, while the solvent concentration of the coagulating bath was varied up to a maximum limiting value. In this manner, the theoretical condition of no hardening is approached, and the experimentally determined elongational viscosity approaches a limiting, concentration‐independent value. The rheological properties of the spin dope were determined independently in a jet thrust measurement device. Some of the experimentally determined results on elongational viscosity versus rate of elongation were presented and discussed in the light of the theoretical prediction based on various constitutive equations.
A study of fiber extrusion in wet spinning. II. Effects of spinning conditions on fiber formation
Authors: Han Chang Dae , Segal Leon
Published: April 2003

A study is carried out to investigate the effects of spinning conditions on fiber formation in the wet‐spinning process. The spinning conditions studied are free velocity (and hence free diameter), throughput rate, maximum take‐up velocity, jet stretch (the ratio of take‐up velocity to free velocity), and filament tension. The coagulating bath temperature and concentration are varied, and three spinnerette diameters are used. The spinning dope is an aqueous solution of polyacrylonitrile in sodium thiocyanate. The present study shows that the coagulating bath concentration influences the spinning tension and maximum take‐up velocity. Two thread breakage mechanisms are postulated which take into account the rate of coagulation, spinning tension, and thread velocity. An attempt is made to predict the concentration profile of solvent in the moving filament by simultaneously solving the mass and force balance equations, in which the increase in elongational viscosity along the spinning way is assumed to be mainly due to the hardening process.
A micro‐macro correlation of ozone‐induced fracture in rubber
Authors: DeVries K. L. , Simonson E. R. , Williams M. L.
Published: April 2003

Rate of molecular bond rupture is successfully correlated by a Griffith‐type energy balance to the strain energy release rate during ozone cracking of rubber. Rate of bond rupture is determined from electron paramagnetic resonance (EPR) measurements. The rate of strain energy release is determined from stress–elongation measurements during stress relaxation, creep, and cyclic loading tests. To compare with macroscopic crack studies, it was assumed that each ruptured bond created a given amount of fracture surface. Numerical agreement could be obtained by assuming each broken bond results in the production of an area of approximately 10−13 cm2. Using the surface energy density determined from stress relaxation tests in an energy balance gives surprisingly accurate predictions of expected behavior in creep and cyclic loading tests. There is a one‐to‐one correspondence between the rate of crack growth (bond rupture) and rate of energy release from strain and external work in all cases. It is proposed that such correlations give credence to a Griffith‐type approach to environmental cracking which it did not have previously.
Kinetic analysis of radiation‐initiated copolymerization reactions of water‐soluble vinyl monomers with cellulose
Authors: Byrne Geoffrey A. , Arthur Jett C.
Published: April 2003

A kinetic analysis of the radiation‐initiated copolymerization reactions of 2‐hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), and methacrylic acid (MAA) from water, methanol (MeOH), N,N‐dimethylformamide (DMF), dimethysulfoxide (DMSO), and combinations of these solvents with irradiated fibrous cellulose I and II was made. The maximum extent of copolymerization of HEMA and HPMA with irradiated cellulose occurred from water solutions. When organic solvents were added to the water solution, while the concentration of monomer was kept constant, the extent of copolymerization decreased. The maximum extent of copolymerization of MAA with irradiated cellulose occurred from mixtures of MeOH (15–30 vol‐%) and water (85–70 vol‐%) solutions rather than from water. After initiation of the copolymerization reactions, they were apparently diffusion controlled and exhibited second‐order kinetics. The relative concentrations of grafted polymer and homopolymer formed with irradiated cellulose from aqueous solutions depended primarily on the concentration of water in the solutions. From MeOH (60 vol‐% or less)–water (40 vol‐% or more) solutions, about 60% of poly(MAA) formed was apparently grafted polymer; from solutions containing less water, the fraction of grafted polymer decreased to about 40%.
Predicting nonlinear viscosity and elasticity from zero‐shear parameters in the Pao‐Rouse model
Authors: Fruh S. M. , Rodriguez F. , Manning A. J.
Published: April 2003

When the Rouse distribution of relaxation times is inserted into Pao's constitutive equation as expressed by Huseby and Blyler, a simple two‐parameter model results. The parameters can be fitted using the limiting values of viscosity and modulus at low shear rates. The modulus in this case is defined as the ratio of shear stress during steady flow to the recovered shear during creep recovery with the stress removed. The mathematical model, is then used to predict the behavior at high shear rates where flow is pseudoplastic and elasticity is non‐Hookean. A sample of polyisobutylene and several high molecular weight poly(dimethylsiloxanes) can be fitted reasonably well. Silicones of lower molecular weight (3.7 and 5.5 × 105) are not correlated successfully, perhaps because not all the “recoverable shear” stored during flow can actually be recovered experimentally. The Rouse distribution can be generalized for added flexibility.
The conformation of the anhydrocellobiose units in cellulose I and II
Authors: Chü N. J.
Published: April 2003

It is postulated from energetic considerations that the anhydrocellobiose unit in cellulose I has a conformation differing from that in cellulose II. Conformation I has two intramolecular hydrogen bonds, while conformation II has only one. This difference arises from a different orientation of the C(6)‐hydroxyl group in the two conformations. Their interconversion is shown to be dependent upon the polarity of the medium. The assignment of conformation I to cellulose I and conformation II to cellulose II and the equilibrium between them appear to be consistent with a number of experimental observations reported in the literature.
Reactions of wood components with hydrogen sulfide. VIII. Influence of cation and base catalysts on the reductive thiolation reaction at cellulose‐reducing endgroups
Authors: Procter A. R.
Published: April 2003

In the presence of calcium, magnesium, and ammonium ions, the reductive thiolation reaction at cellulose‐reducing endgroups by a hydrogen sulfide–hydrosulfide ion buffer system is more efficient when compared to the sodium base system. The calcium and magnesium base systems show a maximum reaction rate when the buffer pH is 5.9, thus behaving similarly to the previously described sodium base system. In the ammonium base system, however, there is a specific ammonia‐catalyzed reaction with no maximum in the reaction rate over the available pH range. The increased efficiency of the bivalent ion systems is thought to be due to the formation of a salt‐like complex between the cation and an intermediate gem‐dithiol structure in the reductive thiolation reaction scheme. Ammonia enters into the kinetics of the reaction, but the exact mechanism of its action is unclear. Some other nitrogenous bases also catalyze the reductive thiolation. The use of ammonium hydrosulfide to carry out the reductive thiolation reaction is also briefly described.
An investigation of mechanisms of synergistic interactions in PVC stabilization
Authors: Briggs G. , Wood N. F.
Published: April 2003

Synergism in poly(vinyl chloride) stabilization has been studied by measuring rates of hydrogen chloride evolution from samples of polymer in the presence of stabilizers in di‐(2‐ethylhexyl) phthalate solution in an inert atmosphere. Barium, cadmium, calcium, and zinc laurates, when used alone, allow escape of hydrogen chloride well before stoichiometric uptake is achieved, whereas synergistic mixtures of calcium–zinc and barium–cadmium laurates absorb almost the theoretical quantity of hydrogen chloride. Cadmium and zinc laurates replace labile chlorine atoms in the polymer backbone by ester groups, reducing formation of long polyene sequences: barium and calcium laurates delay the formation of cadmium and zinc chlorides, apparently by reconverting them into their respective laurates. Polyols function by forming complexes with the prodegradant cadmium and zinc chlorides, but contrary to popular belief phosphites possess little activity in this respect. Instead, they slow down the rate of polymer degradation by removal of labile chlorine atoms, by reaction with hydrogen chloride, and by peroxide decomposition.
The permeation of gases through modified polymer films. IV. Gas permeability and separation characteristics of graft copolymers of polyethylene and teflon FEP films
Authors: Kanitz Peter J. F. , Huang Robert Y. M.
Published: April 2003

The effects of grafting styrene and acrylonitrile onto polyethylene and Teflon FEP films on their gas permeation and separation properties were investigated. The time‐lag method was used to determine the permeability, diffusion, and solubility coefficients of nitrogen and methane gases in the grafted films. The separation factors of nitrogen—methane gas mixtures were measured by gas chromatography. Structural and morphologic changes in the modified films were examined by density, differential scanning calorimetry, and infrared measurements. Attempts were made to relate these changes to the gas permeation and separation characteristics of the films. Modification by graft copolymerization resulted in slightly improved separation factors; however, the permeability and diffusion coefficients decreased. The experimental permeability and diffusion coefficients for gas mixtures were in good agreement with those of the pure components and could be predicted by single gas permeability and diffusion coefficients.
A graphic procedure for obtaining average molecular weights from a chromatogram
Authors: Schrager M.
Published: April 2003

A simple graphic method is described for obtaining average molecular weights of a continuously distributed polymer from its GPC chromatogram. The method is based on the assumption that the weight distribution of the polymer may be approximated by a Schulz distribution. As an example, a polystyrene sample is analyzed graphically, and the results are compared with the traditional method of calculation.
Decomposition kinetics of a phenolic–carbon composite. II. Rate relationships
Authors: Auerbach Irving
Published: April 2003

The isothermal decomposition of a phenolic resin in a phenolic–carbon cloth composite was measured in air at 0.1 to 0.2 torr over the temperature range 104–718°C. Two decomposition rate relationships are presented that can be used to predict decomposition. One assumes two second‐order consecutive rate‐controlling reactions, and the other assumes a diffusion‐limited second‐order reaction. Two rate constants govern each relationship, one being operative during the initial decomposition stages, and the other during the final stages. Evidence is presented to support the applicability of both relationships to predict decomposition over the entire temperature range studied. Arrhenius plots of the rate constants consist of several segments linearly connected. Activation energies and frequency factors computed from these segments cover a broad range of values. The activation energies are used to correlate the temperature ranges with the predominant products formed in these ranges.
Thickening of poly(vinyl alcohol) by borate
Authors: Nickerson R. F.
Published: April 2003

Viscosity and pH of aqueous borate–poly(vinyl alcohol) mixtures were determined under different conditions toward a clarification of the thickening mechanism. Boric acid has little effect on dilute poly(vinyl alcohol) (PVOH), but sodium borate causes sharp viscosity increases which are temperature sensitive and apparently stem from labile exothermic crosslinking of PVOH by borate ions. The pH data indicate that the complexing of borate with simple polyols such as mannitol and glycerol is a different process from borate crosslinking of PVOH. The PVOH thickening and gelling effect probably arises from the replacement of labile waters of hydration on borate ion by OH groups of PVOH rather than from borospirane formation.
Modification of butadiene rubber with 1,3‐dipolar cycloaddition reaction. I. Preparation and properties of the modified polybutadiene
Authors: Tada Koichi , Numata Yoshihiko , Katsumura Toshiaki
Published: April 2003

Polybutadiene of lowcis‐content was modified with the precursors of nitrones and nitrile oxide. The carbon‐black‐filled vulcanizates of the modified rubbers containing isoxazolidine and isoxazoline groups showed good tensile properties. The effect of modification was ascribed to the interaction between active sites of carbon black particles and the heterorings.
Effects of corona treatment on composite formation. Adhesion between incompatible polymers
Authors: Blais P. , Carlsson D. J. , Wiles D. M.
Published: April 2003

Polypropylene–nylon 6 10 composites were prepared by the in situ polymerization of the nylon monomers on polypropylene films. The adhesion between the nylon and the polypropylene was markedly improved by a brief corona discharge treatment of the films in nitrogen prior to coating. This improvement was demonstrated by an increase in the peel strength of the nylon coating and a decrease in brittleness of photo‐oxidized compesites when corona treatment was used. Adhesive bonding between the nylon and substrate was sufficiently strong to cause cohesive failure in the corona‐treated polypropylene. Only interfacial failure was observed at untreated surfaces. These effects were demonstrated by electron microscopy of the surfaces produced in peel tests. The effects of corona treatment on adhesive bonding characteristics of surfaces are discussed in terms of the chemical and physical changes observed in treated surfaces.
Cellulosates of group ia metals—their preparation and reactivity with β‐chloroethyldiethylamine
Authors: Soignet D. M. , Berni R. J. , Benerito R. R.
Published: April 2003

Mercerized cotton printcloth converted to a cellulosate of lithium, sodium, potassium, rubidium, or cesium by reaction with metal methoxide is a good substrate for the preparation of diethylaminoethyl (DEAE) cotton at low temperatures in nonaqueous media. The pretreatment to form the cellulosate of the alkali metal does not adversely affect mechanical properties of the cotton fabric. There is no advantage to using a cellulosate other than sodium cellulosate in reactions with β‐chloroethyldiethylamine to form DEAE cotton. The reaction occurs in organic solvents of low and high dielectric constants. The hydrochloride of the amine rather than the free amine can be used to prepare DEAE cotton, provided the ratio of reactants is within specific limits. Consideration has been given to the mechanism of the reaction.
Crack initiation in PVC for subsequent linear elastic fracture mechanics analysis
Authors: Faulkner P. G. , Atkinson J. R.
Published: April 2003

Reproducible starter‐cracks for subsequent linear elastic fracture mechanics analysis have been grown in PVC by fatigue cycling at 80 Hz. The crack growth rate has been related to the fracture surface markings and to the opening mode stress intensity factor (KI) of the fatigue cycle. Termination of the fatigue crack growth when crack growth rate is constant ensures a smooth mirror fracture surface and a sharp crack tip.
Compatibility of plasticizers with poly(vinyl chloride)
Authors: Wales M.
Published: April 2003

The tendency of a plasticizer to resist exudation from poly(vinyl chloride) (PVC) under compressive stress, known technologically as “compatibility,” is treated in terms of a network model, the plasticized composition being thought of as a rubber crosslinked by crystallites. Compatibility is increased by increased solvency (Flory‐Huggins χ) and decreased by increasing plasticizer molar volume. A large crosslink density and/or insufficient melting of crosslinks during processing (thermal history) also decreases compatibility. All commercial primary plasticizers are believed to be infinitely miscible with amorphous PVC. Phase separation which occurs is syneresis and not related to any phase diagram. Swelling tests for compatibility and swelling measurements on dilute PVC gels are described. Some general principles relating to gel formation and association in polymer solutions are also discussed.
The preparation and purification of diphenylolpropane 4,4′‐dioxyacetic acid (bisacid A2)
Authors: Lenk R. S.
Published: April 2003

Earlier work on the synthesis of bisacid A2 is reviewed. The problems associated with the achievement of a pure product in good yield are pointed out. The procedure for obtaining same is described. It is believed that the melting point (or rather melting range) of bisacid A2 prepared from specially pure bisphenol‐A and purified as described is higher than that of any bisacid A2 previously reported in the literature.
The thermal degradation of perfluoropolypyridine
Authors: Cotter J. L. , Dickinson Hilary , Knight G. J. , Wright W. W.
Published: April 2003

The thermal degradation of perfluoropolypyridine was studied in inert and oxidizing atmospheres by thermogravimetric techniques. Volatile products were analyzed mass‐spectrometrically, and the yield of products giving rise to fluoride ion was also determined. The stability of the polymer on a weight loss basis is rather better than that of polytetrafluoroethylene in inert atmospheres, but rather worse in oxidizing atmospheres. The major breakdown route seems to involve removal of the fluorine from the heterocyclic nucleus by a mechanism as yet unknown.
Permeability of polyethylene film to organic vapors
Authors: Laine Roney , Osburn James O.
Published: April 2003

The permeabilities of polyethylene film to vapors of 19 organic compounds at temperatures of 21°C, 38°C, and 49°C were measured by a sorption method. The film was formed into a pouch, which was filled with silica gel, sealed, and suspended in a saturated atmosphere. The permeability was calculated from the steady‐state rate of the gain in weight. The permeability data were correlated with the Hildebrand solubility parameters of the organic substances.
The relationship between polymer elastic properties and the ability to impart improved wrinkle recovery to cotton fabric
Authors: Rawls H. R. , Klein E. , Vail Sidney L.
Published: April 2003

The wrinkle recovery of polymer‐coated cotton printcloth was generally found to correlate qualitatively with the elastic behavior of the polymer film. Of the several tensile parameters that can describe elasticity, immediate strain and work recoveries and stress decay were found to be the most sensitive indicators of the polymers' performance on the fabric. Delayed recovery, ultimate elongation, and permanent set were found to be important but were less sensitive parameters; while tensile strength and initial modulus appeared to be unrelated. A model is described whereby the polymer provides additional recovery forces when properly coupled to the fabric. High values of stress decay and permanent set diminish the effectiveness of these forces, while high values of immediate, work, and delayed recovery indicate that large portions of the distorting forces are available for recovery.
The significance of the rubber damping peak in rubber‐modified polymers
Authors: Keskkula Henno , Turley S. G. , Boyer R. F.
Published: April 2003

Dynamic mechanical properties have been used as the basis for some important conclusions with regards to the physical properties of rubber‐modified high‐impact polymers. This paper attempts to show that conclusions of this type should be limited to fairly narrow groupings of polymers. Since the size, shape, and position on the temperature scale of a damping peak are influenced by composition, morphology, and method of polymer preparation, the significance of the damping peak associated with the rubber phase of the polymer has probably been generalized to too great an extent. Two examples of polymer groupings are given to illustrate the need for caution in attaching significance to the dynamic mechanical properties of polymers. Also given are two fairly narrow polymer groupings to show to what extent dynamic mechanical properties can be used for a correlation with impact strength and rubber concentration.
Flow of viscous fluid through a circular aperture
Authors: Chong J. S. , Christiansen E. B. , Baer A. D.
Published: April 2003

The creeping flow of a highly viscous incompressible fluid through a circular aperture located in an infinitely wide horizontal plate is analyzed by solving Navier‐Stokes equations without inertia terms. Solutions for vertical and radial velocities as well as pressure have been obtained in terms of integral equations with an undetermined Kernal function. This function has been evaluated by assuming several different velocity distributions at the aperture, and the corresponding pressure drop for each case has been calculated. The results show that the pressure loss for a given flow rate goes through a minimum as the assumed velocity profile changes from flat to parabolic. Based on the minimum energy dissipation theorem of Helmholtz, the most appropriate velocity distribution is discussed. Experimental data obtained using sharp‐edged orifices are compared with theoretical predictions.
The synergistic effect of benzhydrylation and iodination of the flammability of alpha‐cellulose
Authors: Lipska A. E. , McCasland G. E.
Published: April 2003

Cellulose samples modified by iodination, benzhydrylation, and benzhydrylation followed by iodination were pyrolyzed to investigate the potential flame retardance of such treatments. Their effect on crystallinity, rate of thermal degradation, char production, and pyrolysis products was determined. Results indicate that in general the crystallinity index varies inversely with the percentage of substitution, rate of weight loss, and amount of residual char. Although the rates of weight loss of the substituted samples increased from 0.3%/min to 108%/min, depending on the type and percentage of substitution, the overall weight loss pattern of the treated cellulose was similar to that of the untreated samples. Of the three treatments, iodination appears to offer the best flame retardance in that the residual char is increased by a much larger factor for a given weight loss rate. On the other hand, addition of the benzhydryl to the iodinated sample decreases the char. All three treatments drastically reduce the number of degradation products of molecular weights lower than 150; untreated cellulose gave 59 components, whereas the substituted cellulose produced five major compounds: water, acetic acid, furfural, 5‐methyl‐2‐furaldehyde, and 1,5‐anhydro‐2,3‐deoxy‐β‐D‐pent‐2‐eno‐furanose. Of these, water and the furanose derivatives were the major components.
Thermal behavior of poly(vinyl alcohol) modified with phosphorous acid
Authors: Łaszkiewicz Bogumił
Published: April 2003

The thermal behavior of poly(vinyl alcohol) (PVA) modified with H3PO3 has been studied. The effect of phosphorus content in the polymer on the dehydration rate is discussed as well as the temperature‐dependent changes in sample weight. It has been shown that the presence of phosphorous acid radicals in PVA causes a lowering in the temperatures of dehydration and pyrolysis and accelerates these processes.