bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid method for the determination of molecular weight distribution in high polymers: A thermal gradient‐turbidity technique
Authors: Gamble Leon W. , Wipke W. Todd , Lane Trent
Published: April 2003

A rapid method for determining the molecular weight distribution of polymers has been the aim of polymer chemists for a long time. The method presented here requires less than two hours, including dissolution of the polymer. It is an extension of a photoelectric turbidimetric technique presented by Taylor and Tung in 1961. The equipment has been completely redesigned and presently consists of a copper block containing a turbidity cell, optical system and attendant electronic circuitry for measuring relative changes in turbidity of polymer solutions as a function of temperature. An X–Y recorder is used to plot turbidity versus temperature. A parameter determined from the plot is correlated with a measure of molecular weight distribution determined on known samples for each type polymer by another means. Based on this correlation unknown samples may be analyzed. The instrument is easy to operate and has shown excellent stability over a two year period. Polymers studied by this technique include ethylene‐propylene copolymer (EPR), polypropylene, polyethylene, and butyl, however, the only results to be reported here are those on ethylene‐propylene copolymer.
Single‐point determination of intrinsic viscosity
Authors: Shroff Ramesh N.
Published: April 2003

Limitations on the use of the equations [η] = {2(ηsp − ln ηre1)}1/2/c and [η] = (ηsp + 3ln ηre1)/4c in determining intrinsic viscosity, [η], by a single point method have been pointed out. Inclusion of higher order terms in the series expansion for ln ηre1 introduces an additional term in the above equations which is negligible when the value of Huggins' constant, k′, is in the vicinity of 0.3–0.4. More accurate values for intrinsic viscosity calculated by a single point method can be obtained using these modified equations provided k′ can be estimated.
Thermogravimetric study of some new transition metal–schiff base coordination polymers
Authors: Horowitz Emanuel , Tryon Max , Christensen Richard G. , Perros Theodore P.
Published: April 2003

A condensation reaction between 5‐amino‐8‐hydroxyquinoline and terephthalaldehyde yielded a bis‐bifunctional Schiff base ligand, 5,′5‐[p‐phenylene‐bis(methylidynenitrilo)] di‐8‐quinolinol, which was used to produce coordination polymers containing Mn(II), Co(II), Ni(II), Cu(II), or Zn(II) in the form of insoluble powders. The thermal stabilities of these polymers were evaluated in vacuum over the temperature range of 25–700°C. by using a newly constructed thermobalance having improved sensitivity. The results relate the decomposition of the polymers to the metal in the backbone as well as to the organic ligand to which the metal is coordinated. Some discussion is devoted to the possible modes of decomposition of these polymers.
Semipermeable membranes of cellulose acetate for desalination in the process of reverse osmosis. III. Bound water relationships
Authors: Vincent Arthur L. , Barsh Max K. , Kesting Robert E.
Published: April 2003

The mechanism by which water and dissolved salts permeate selectively through membranes has been investigated. It has been demonstrated that the predominant mechanism of permeation involves the interaction of the various species with specific sites and their associated bound water molecules. The extent of the bound water held by the cellulosic membranes of interest has been determined. Correlation has been found between the permeation characteristics demonstrated by membranes at various steps in their preparation and its bound water content. The mechanism of rejection of salts has been shown to be related to the relative inability of their ions to become solvated by bound water. A model has been hypothesized which correctly describes the behavior of the desalination membrane with reference to water and soluble inorganic salts.
Kinetics of vinyl polymerization initiated by ceric ion in aqueous solution
Authors: Ananthanarayanan V. S. , Santappa M.
Published: April 2003

A systematic kinetic study of the thermal polymerization of methyl methacrylate, methyl acrylate, and acrylonitrile initiated by ceric ion in aqueous perchloric, nitric, and sulfuric acid solutions, has been made. The polymerization experiments were conducted in the dark at 35°C. under conditions of negligible oxidation of water by ceric ion. The polymerization was found to proceed without an induction period, and the steady‐state rate was attained in a short time. The rate of monomer disappearance (followed by gravimetry) was found to bear a square dependence on monomer concentration and is independent of both the ceric and hydrogen ion concentrations. The rate of ceric disappearance (followed by titrimetry or spectrophotometry) was found to be directly proportional to the ceric, monomer, and hydrogen ion concentrations. The chain lengths of the polymers (determined viscometrically) were directly proportional to the monomer concentration and inversely to the ceric and hydrogen ion concentrations. Initially added cerous ion had negligible effect on the rates. Increase in ionic strength caused a slight increase in the rates. From experiments conducted at different temperatures, the activation energies for the various processes in the reaction were calculated. Most of the experimental results were suitably explained by a kinetic scheme involving initiation and termination by ceric ion in the unhydrolyzed Ce4+ form.
Characterization studies for polyethylene formed by Co60 γ‐radiation under constant conditions in a nonflow system
Authors: Colombo P. , Fontana J. , Kukacka L. E. , Steinberg M.
Published: April 2003

Several properties of polyethylene, synthesized by Co60 gamma radiation have been investigated. The polymerization reactions were carried out in static experiments over a wide range of conditions. Measurements include molecular weight, molecular weight distribution, density, methyl group content, crystalline melting point, and melt index. The density of polyethylene formed at 20°C. was found to be 0.94 g./cc. This value appears to be independent of pressure from 170 to 1700 atm. and radiation intensity from 0.58 × 105 to 4.7 × 105 rads./hr. Increasing temperature results in increasing methyl group content and a decrease in density to 0.91 g./cc. at 200°C. The polymers formed, over the entire range of experimental conditions, were completely soluble in o‐dichlorobenzene at 135°C. Intrinsic viscosities were determined and their dependence on temperature, pressure, intensity, and radiation dose are shown. An attempt was made to correlate melt index to molecular weight and molecular weight distribution.
Effect of volatilization of stabilizers and oxidation products on polypropylene lifetimes
Authors: Blumberg M. , Boss C. R. , Chien J. C. W.
Published: April 2003

Three methods of measuring thermal oxidative stability of polypropylene have been compared. The oxygen absorption and the sealed tube tests give comparable results. The polymer lifetimes in circulating oven‐aging tests differ significantly from those obtained by the first two methods. The oven‐aging lifetime is aparently influenced to a large extent by the volatilization of the added stabilizer and of the oxidation products, the former decreases whereas the latter increases the polymer lifetime. The optimum composition of a synergistic stabilizer system was found to vary with the test method.
Estimation of molecular weights of epichlorohydrin–bisphenol a polymers by gel permeation chromatography
Authors: Edwards G. D.
Published: April 2003

During a program to evaluate the gel permeation chromatography (GPC) technique for measuring the molecular size distribution of polymers, three experimental epichlorohydrin–bisphenol A polymers were sent to Waters Associates for analysis with the commercially available instrument. The resulting distribution curves were used to calculate weight‐average and number‐average chain lengths of the samples. These values were found to give good straight‐line correlations with weight‐average and number‐average molecular weights measured by absolute methods. Thus the GPC method gives meaningful information about the molecular size distribution of polymers which can be used to obtain rapid estimates of molecular weight.
Specific refractive index increments of polymer solutions. Part II. Scope and applications
Authors: Huglin M. B.
Published: April 2003

The data of Part I are examined in the light of accepted theories. The specific refractive index increment ñ of most polymer solutions lies between −0.2 and +0.2 ml./g., although larger values can obtain in circumstances wherein the scattering unit is unusually large, e.g., solutions of partially neutralized polyacids the units of which contain the gegenions. ñ depends on the indices of solvent n1 and polymer n2. Among common solvents, water and 1‐bromonaphthalene are capable of affording high positive and negative values, respectively, for n. The Gladstone‐Dale rule applies rigorously to pure and mixed solvents, but the Lorenz‐Lorentz expression is preferable for evaluating n2. Results of current theories applied to mixed solvents and copolymers are summarized. In the former, the true molecular weight M is determined by using ñ and the variation of solvent index with composition. For a copolymer of monomers A and B, M as well as Ma and Mb are obtainable by using ñ, ña, and ñb. Dispersion is expressed as (ñ)λ = (ñ)436[D′ + D″/λ2] at a wavelength λ, and dispersive constants D′ and D″ are evaluated for some solutions. ∂ñ/∂T is generally 3.2 (±2.3) × 10–4 ml./g./°C. and changes very little with λ. When ñ increases with M, the limiting characteristic value is derived (at 1/M = 0) from a plot of ñ versus 1/M. ñ can be determined to a maximum accuracy of 1% by using n2 calculated from the Lorenz‐Lorentz equation and the experimental partial specific volume.
The effect of plasticizing compounds on acrylic fibers
Authors: Gur‐Arieh Z. , Ingamells W. , Peters R. H.
Published: April 2003

Comparison of the various solubility parameters of different plasticizing agents has shown that their plasticizing action on Acrilan filaments is governed by polar interactions. The diameter swelling of the filaments appears to decrease with increasing efficiency of the plasticizing agent. The diffusion of a disperse day through the plasticized fiber is not related to the fiber swelling and is controlled by the plasticizing action of the dyebath.
Refractometric and calorimetric studies of the van der Waals interactions between the molecules of polycarbonate and of the additives acting as plasticizers or antiplasticizers
Authors: Makaruk Leszek , Polańska Hanna , Staros Elżbieta
Published: April 2003

Considerable deviations of molar refraction from the additivity in the solutions containing polycarbonate and its antiplasticizers symmetrical trinitrotoluene and 1,1‐bis(4‐hydroxy‐3, 5‐dichlorophenyl)2,2,2‐trichloroethane diacetate are reported. In contrast to this, the solutions of polycarbonate with plasticizer di‐n‐butyl phthalate and the solutions of antiplasticizers in pure solvent show only insignificant deviation from the additivity. The calorimetric studies showed the differences in the heats of solution of the used antiplasticizers in pure solvent and in the solvent containing a constant amount of polymer, whereas there was no noticeable difference in the polycarbonate–plasticizer (di‐n‐butyl phthalate) system. Both deviations of the molar refraction from the additivity and differences of the heats of solution prove the existence of strong interactions between the molecules of polycarbonate and the antiplasticizer.
Thermal degradation of polymers. XI. Synthesis, polymerization, and thermal characterization of polymers of p‐N,N‐diethylaminostyrene in nitrogen
Authors: Oprea S. , Still R. H.
Published: April 2003

The monomer p‐N,N‐dimethylaminostyrene has been synthesized from p‐N,N‐diethylaniline and homopolymerized and copolymerized with styrene using 2,2′‐azobisisobutyronitrile as free‐radical initiator. The polymers have been characterized by thermal analysis (DTA, DSC, and TG). Glass transition temperatures have been measured and activation energies for degradation in nitrogen have been established by a variety of methods for comparative purposes.
Thermal degradation of polymers. XIII. Thermal analysis studies on p‐N,N‐dimethylaminostyrene homopolymers and copolymers with styrene in air
Authors: Still R. H. , Whitehead A.
Published: April 2003

Homopolymers of p‐N,N‐dimethylaminostyrene and copolymers with styrene have been subjected to thermal analysis studies in air. Molecular weight and copolymer composition have been shown to influence the stability of the polymers and the shape of the TG and DSC curves obtained under dynamic conditions. Mechanisms to account for this behavior based on the anti‐oxidant effect of the chain‐bound p‐N,N‐dimethylamino substituent are discussed.
Reactivity of poly(vinyl chloride) containing N‐methyl dithiocarbamate toward metal ions in heterogeneous system and effect of γ‐irradiation on the reactivity
Authors: Nakagawa Tsutomu , Oishi Noriko , Fujiwara Yukihiko
Published: April 2003

The reaction of poly(vinyl chloride) containing N‐methyl dithiocarbamate (PMD) with metal ions in a heterogeneous system and the effect of γ‐irradiation on the reactivity were studied. PMD powder suspended in aqueous solutions did not show any reactivity toward metal ions. However, the PMD powder suspended in a methyl alcohol solution formed a chelate with various metal ions. The effects of the reaction time, pH, and the initial concentration of the metal ion were examined. PMD irradiated in methyl alcohol with γ‐irradiation doses up to 28 Mrad was compared with the original PMD. The reactivity of the irradiated PMD toward the metal ions did not show any apparent decrease.
A comparison of equations for the effect of pressure on the viscosity of amorphous polymers
Authors: Goldblatt Philip H. , Porter Roger S.
Published: April 2003

Several equations which are used to predict the pressure coefficient of viscosity for amorphous polymers have been examined on the basis of type of information required and equation reliability. These equations can be useful in accounting for pressure effects observed in tubular flow and in other shear geometries. The correlations of Penwell and Porter and of Miller are evaluated and in the perspective of expressions by Matheson and by Eyring. Data on linear amorphous polystyrene (PS), polyisobutylene, poly(vinyl acetate), poly(methyl methacrylate) (PMMA), natural rubber, and polycarbonate are examined and presented. Predictions from the Penwell‐Porter and Miller equations are compared with experimental coefficients at one atmosphere for all data available. For PS and PMMA, it was found that Miller's equation tends to predict values somewhat higher than experiments but is closer to the data on PS and on a high molecular weight PMMA. The Penwell‐Porter equation, on the other hand, tends to predict values somewhat lower than experiments and does a slightly better job for lower molecular weight PMMA. Both equations require WLF or Vogel coefficients and Tg‐pressure‐molecular weight data. Miller's equation also requires compressibilities at Tg and at the temperature of interest, although an alternate method can be used which only requires average “K” values without Tg‐pressure or compressibilities at Tg.
Effect of dispersity on the Tll (>Tg) transition in polystyrene
Authors: Glandt C. A. , Toh H. K. , Gillham J. K. , Boyer R. F.
Published: April 2003

The presence of a high temperature (>Tg) relaxation in amorphous polystyrene has been investigated further. In the previous work,1 the techniques of differential thermal analysis (DTA) and torsional braid analysis (TBA) were employed to study polystyrene as a function of “monodisperse” molecular weight. The occurrence of the Tll transition appeared to be associated with the attainment of a critical viscosity level with also corresponded with a free volume level. An entanglement network developed at a critical value of molecular weight, Mc, giving a break in the Tll‐versus‐M plots. The present work deals with the influence of dispersity on the Tll transition, below and above Mc. A series of binary blends of “monodisperse” anionically polymerized polystyrenes with systematic changes in M̄n and heterogeneity index (M̄w/M̄n) was tested by TBA. The results show that when both components have molecular weights below Mc, single and average values of Tg and Tll are observed which are linearly related to M̄n−1, as predicted by free volume arguments. Although a single Tg is observed when one component has a molecular weight above and the other has a molecular weight below Mc, the components appear to undergo the Tll relaxation independently. The results indicate that both the glass transition and the Tll transition are basically governed by the same type of molecular motion but at different length ranges.
The spinnability of polymer fluid filaments
Authors: Ide Yoshiaki , White James L.
Published: April 2003

A theoretical study of the stability of extending liquid filaments has been carried out. The interaction of surface tension and different fluid rheological properties is investigated. It is also hypothesized that cohesive failure or fracture will occur if a critical stress level is reached. It is predicted that viscosity and viscoelasticity tend to stabilize the filaments. However, even extremely high viscosity filaments will neck and exhibit ductile failure. In highly viscoelastic fluids, defects tend to heal during stretch. Highly viscoelastic fluid filaments fail by fracture. The theory is used to predict the failure of molten polymer filaments as a function of molecular weight. The extensibility or spinnability of filaments is predicted to exhibit a maximum at intermediate molecular weights with capillarity‐ductile failure occurring at low molecular weights and cohesive fracture, at high molecular weights. The results are compared to experiments on polyethylenes. There is general qualitative agreement especially with the behavior of low and high molecular weights where capillarity and fracture occur. The tendency to necking and ductile failure differs considerably among melts and is more pronounced in high‐density than in low‐density polyethylenes. The application to continuous spinline behavior is discussed, and draw resonance is suggested to be the continuous process analogue of ductile failure.
The crystallinity of poly(phenylene sulfide) and its effect on polymer properties
Authors: Brady D. G.
Published: April 2003

The crystallinity and crystallizability of poly(phenylene sulfide) have been examined by a number of common techniques. Several provided qualitative information, but only one, x‐ray diffraction, was considered sufficiently reliable and reproducible to allow quantitative comparisons. Based on x‐ray measurements, an approximate degree of crystallinity, termed crystallinity index (Ci), could be readily assigned. According to this method, virgin polymer possesses significant crystallinity (Ci ≈ 65%). Curing (crosslinking) the resin below its melting point did not change the crystallinity but did affect the crystallizability. Lightly cured resin suitable for molding and film extrusion was easily quenched from the melt to give amorphous polymer. The amorphous samples crystallized rapidly when heated to temperatures > 121°C (250°F). At mold temperatures below 93°C (200°F), moldings with very low surface crystallinity were produced. Annealing (204°C, 400°F) caused rapid crystallization of such moldings, and changes in crystallinity were correlated with observed changes in physical properties. The resin crystallizes so rapidly that these quenched moldings possessed a crystallinity gradient, the internal crystallinity being substantially greater. At high mold temperatures (121–204°C, 250–400°F), moldings very similar to fully annealed specimens were obtained.
Structure–property relationships in copolymers to composites: Molecular interpretation of the glass transition phenomenon
Authors: Kaplan Donald S.
Published: April 2003

Structure is taken as the main theme in outlining the mechanical properties of polymer composites. Examples of two‐component polymer systems are selected from the literature showing their morphology, as evidenced from electron micrographs, and their corresponding mechanical properties, as evidenced by dynamic mechanical spectra. A compatibility number, Nc, is defined in a continuous scheme from a compatible system (one glass transition, Nc → ∞) to an incompatible system (two glass transitions, Nc → 0). The point at which semicompatibility occurs, Nc ≅ 1, is taken as the approximate universal segmental length associated with a glass transition. This length of 150 Å allows for 100 to 5000 CC bonds for an associated glass transition. The ramifications of this molecular interpretation of a glass transition are discussed, resulting in a denouncement of the time–temperature correspondence principle and a new interpretation of short‐segmental block copolymers.
New catalyst system for easy‐care cotton finishing
Authors: Hebeish A.
Published: April 2003

A new catalyst system, based on a mixture of boron trifluoride–acetic acid complex (BF3·2CH3COOH) and magnesium chloride hexahydrate (MgCl2·6H2O), has been examined in cotton finishing treatment for producing easy‐care properties. It provides strong catalysis in crosslinking cotton with a series of N‐methylol finishing agents when the pad‐dry‐cure process is applied. Curing can be carried out at a temperature of 130–150°C for a period of 1–3 min, dependent on the temperature used. The resilience and abrasion resistance properties as well as the degree of polymerization (D.P.) of the crosslinked cotton so obtained were equivalent or slightly better than those of crosslinked cottons catalyzed by conventional catalysts. The influence of the new catalyst as well as a number of conventional catalysts, viz., ammonium chloride, ammonium dihydrogen phosphate, magnesium chloride hexahydrate, and zinc nitrate hexahydrate, on some properties of cotton fabrics was also investigated. The behavior of these catalysts in the presence of the N‐methylol finishing agent was quite different from their behavior in its absence. With the exception of ammonium salts, the D.P. of crosslinked cotton was much higher than that of cotton treated with the catalyst only. The opposite holds true for the abrasion resistance.
Elementary steps in Ziegler‐Natta catalysis
Authors: Fink Gerhard , Rottler R. , Schnell D. , Zoller W.
Published: April 2003

This paper is a short review of our recent advances in Ziegler‐Natta catalyst system of the type (C5H5)2TiRCl/AlEtn Clm. These are, for instance, the electronic changes after complex formation, the parallel reactions of the alkyl and chain transfer between both the Ti centers of two complexes and the Ti center and an Al center of two complexes; furthermore, the alkyl, chain, and chlorine transfers between these complexes and dimer Al–alkyl, the time which the insertion step of one ethylene requires, and the mathematical calculation of the kinetics of the polyreaction.
Phosphorylation of cellulose with phosphorous acid and thermal degradation of the product
Authors: Inagaki Norihiro , Nakamura Satoshi , Asai Hitoshi , Katsuura Kakuji
Published: April 2003

The reaction of cellulose with phosphorous acid in molten urea afforded a white, water‐soluble product. The product was a monoester of phosphorous acid, and all the phosphorus residues were in phosphonic form, i.e., cellulose phosphonate. Quantitative addition of acrylonitrile to the PH bonds in cellulose phosphonate occurred in the presence of sodium ethoxide. By alkali hydrolysis of the adduct, a polyelectrolyte having two different ionization groups, POH and COOH, could be prepared. Thermal degradation of three cellulose phosphonates, ammonium cellulose phosphonate (I), ammonium cellulose 2‐cyanoethlyphosphonate (II), and ammonium cellulose 2‐carboxyethylphosphonate (III), was examined. All three samples decomposed at a temperature around 270°C, but their thermal behaviors were different. Replacement of hydrogen in the phosphonic residue by 2‐cyanoethyl and 2‐carboxyethyl groups retarded dehydration of cellulose. Sample I had a satisfactory flame retardance; samples II and III were not flame resistant. Reduction of flame retardance may be due to the electron‐withdrawing effect of the cyano and carboxyl groups.
Effect of hydrogen bond formation on dynamic mechanical properties of amorphous cellulose
Authors: Yano Shoichiro , Hatakeyama Hyoe , Hatakeyama Tatsuko
Published: April 2003

The temperature dependence of the dynamic modulus (E′) and the mechanical loss tangent (tanδ) of amorphous cellulose prepared from cellulose triacetate by saponification was measured and compared with that of cellophane, recrystallized cellulose obtained by immersing amorphous cellulose in water, and cellulose triacetate. The E′ of amorphous cellulose decreased initially with increasing temperature and then began to increase at about 70°C with a maximum at 80°C, decreasing again at about 100°C. Another decrease in E′ was observed at 220°C accompanied by a discontinuity at 155°C. In the tan δ‐versus‐temperature curve, a medium peak at 60°C a shoulder peak at 146°C, and a broad peak at 200°C were observed. It was found that the transition at about 60°C was related to hydrogen bond formation by free OH groups. The transition at about 150°C was attributed to a recrystallization process by heating, and the relaxation at 200°C, to the glass transition of the polymer. The decrement in E′ observed at about 100°C was attributed to the cooperative motion of an individual pyranose ring in amorphous cellulose, juding from the E′ and tan δ assignment of other cellulose materials. The change in E′ was also measured isothermally as a function of time in the temperature range between 40°C and 80°C, where a maximum in tan δ and an increment in E′ were observed as the temperature dependence of the dynamic viscoelasticity. The change in E′ with elapsed time was analyzed kinetically, and an activation energy of 2.6 kcal/mole was calculated. This value is the expected activation energy of hydrogen bond formation.
Reaction of hexamethylene diisocyanate with poly(vinyl alcohol) films for biomedical applications
Authors: Caro S. V. , Sung C. S. Paik , Merrill E. W.
Published: April 2003

The objective of this work was to obtain primary amine groups on the surface of poly(vinyl alcohol) films by means of a reaction with hexamethylene diisocyanate. The reaction was run in such a way as to minimize the internal crosslinking by employing a large excess of hexamethylene diisocyanate in toluene and then hydrolyzing the unreacted isocyanate endgroup to primary amine. After dialyzing out the adsorbed hexamethylenediamine from the aqueous solution of reacted poly(vinyl alcohol), the extent of covalent bonding of hexamethylene diisocyanate onto the polymer was determined by measuring aminohexyl content through a fluorescence assay. This assay is based on the reaction of fluorescamine, 4‐phenylspiro[furan‐2(3H)‐1′‐phthalan]‐3,3′‐dione, with a primary amine to yield a fluorophor which will emit a strong fluorescence at 475–490 nm when excited at 390 nm. Analyses show a range of 1.1 × 10−10−3.6 × 10−10 mole of amines per cm2 of reacted poly(vinyl alcohol) film. When assuming 47% as degree of crystallinity approximated by IR spectroscopy for these polymer films, the availability of hydroxyl groups in amorphous region was estimated to be 3.7 × 10−10 mole/cm2. The extent of reaction based on available hydroxyl groups was then in the range of 31–97%. The primary amine groups attached by this method can now be exploited for binding biomolecules such as heparin (anticoagulant) or fibrinolytic enzymes in an attempt to achieve biocompatible materials.
The effect of solution variables on the solution of cellulose in dimethyl sulfoxide
Authors: Seymour Raymond B. , Johnson Earl L.
Published: April 2003

Through the study of the effects of concentration, temperature, and molar ration (of paraformaldehyde to cellulose) on solution viscosity and per cent transmittance (at 530 nm), it has been demonstrated that cellulose solutions in dimethyl sulfoxide (DMSO) are readily produced. By heating 1, 2, and 50 to 100 parts by weight of cellulose, paraformaldehyde, and DMSO, respectively, extremely viscose cellulose solutions and gels were prepared. Solutions with concentrations as high as 10% were prepared. However, the optimum conditions to effect complete cellulose solution in DMSO at 75°C were found to be 0.5% cellulose and 0.8 and 1.0% paraformaldehyde. This corresponds to a paraformaldehyde‐to‐cellulose molar ratio of about 10:1.
The effect of glass transition on gas permeabilities
Authors: Yasuda H. , Hirotsu Toshihiro
Published: April 2003

Gas permeabilities of a copolymer of acrylonitrile and methyl acrylate were examined at the temperature range of 25° to 80°C. The change of activation energy of gas permeability constant at the glass transition temperature (65°C) was observed with N2, Ar, O2, and CO2, but no change was observed with He. The observation of the change of slope of the Arrhenius plot of gas permeability is discussed as a function of the diffusion constant (D) of a permeant gas at the glass transition temperature (Tg). The change occurs only if the value of D at Tg is smaller than a certain value (i.e., 5 × 10−8), according to the analysis of data appearing in the literature.
Flame retardancy effects of halogenated phosphates on poly(ethylene terephthalate) fabric
Authors: Inagaki Norihiro , Onishi Hiroyoshi , Kunisada Hideshi , Katsuura Kakuji
Published: April 2003

A Chemical research on the flame retardancy effect of halogenated phosphates on poly(ethylene terephathalate) fabric was carried out by thermogravimetry, infrared spectral analysis, and mass spectrometry. The following conclusions were drawn: (1) The flame retardancy effect of halogenated phosphates such as tris(2,3‐dibromopropyl) phosphate is due to altering the pyrolysis reaction of polyester by aldol condensation. (2) The probability that liberated halogen compounds from the phosphates act as radical acceptors in a flame zone may be low. (3) Incorporation of halogen elements into phosphates appear to depress evaporation of phosphates, which act as acidic catalysts in aldol condensation from the condensed phase.
Bimodal character of polyester–solvent interactions. II. Evaluation of the chemical structures of the aromatic and aliphatic ester residues of poly(ethylene terephthalate)
Authors: Knox B. H.
Published: April 2003

The chemical structures of the aromatic (A) and the aliphatic ester (B) residues of poly(ethylene terephthalate), PET, are evaluated from a comparison of their Hansen solubility parameters, as determined experimentally, and with those calculated for the various residues of PET. From such a comparison it is proposed that the structures of residues A and B are best represented by “hybrid” structures which may be taken as linear combinations of two or more structures rather than by single chemical structures. That is, the 1,4‐carbonyl group which separates the benzene ring of the aromatic residue and the ethylene group of the aliphatic ester residue effectively acts as a common plane between the two residues and is “shared” by the benzene ring and the ethylene glycol group. It is proposed that the extent to which the 1,4‐carbonyl group is “shared” by residues A and B is 0.33 and 0.67, respectively, which is consistent with the most probable molecular conformation of the 1,4‐benzenoid residue of PET as calculated from the data of Tonelli23 and Daunbeny et al.21 and which gives support to the view that the bond connecting the benzene ring and the carbonyl group is not rigid, but free to rotate as proposed earlier by Flory27 and by Tonelli23
Electrokinetic properties of polyformaldehyde fibers
Authors: Lokhande H. T. , Salvi A. S.
Published: April 2003

Electrokinetic properties, namely, zeta potential (ζ), surface charge density (σ), and surface conductivity (Ks) of polyformaldehyde fibers [poly(oxymethylene) fibers] have been studied in the presence of direct dyes, with or without surfactants and an electrolyte. The anionic dyes increased the negative zeta potential of fibers. The increase in ζ was found to be a function of concentration and basicity of the dye in the streaming solution. Thus, the tetrabasic dye gave higher value of negative ζ than the equivalent concentration of the dibasic dye. The cationic surfactant brought about a decrease in negative ζ, giving a point of inflection, while the anionic surfactant increased it. The nonionic surfactant brought about a certain reduction in negative ζ, but failed to give a point of inflection. In the presence of a direct dye, the cationic surfactant brought about considerable reduction in negative ζ, to give a point of inflection. The presence of an electrolyte in the streaming dye solution progressively lowered the negative ζ. In general, σ increased with the increase in the concentration of either a dye or an electrolyte in the presence of a given concentration of the dye in the streaming solution. Results on Ks indicated that the surface conductivity of the fibers is a function of concentration of dye, surfactant, and electrolyte. It was, however, observed to be independent of the nature of the surfactant. Although both the dibasic and tetrabasic direct dyes brought about an increase in Ks, the extent of increase was dependent upon the basicity of the molecules.
Morphology and mechanical properties of injection‐molded specimens of two‐phase polymer blends
Authors: Han C. D. , Villamizar C. A. , Kim Y. W. , Chen S. J.
Published: April 2003

An experimental study was carried out to investigate the moldability of polymer blends which form two phases in the molten state and the effect of mixing on the morphology and mechanical porperties of molded specimens. Blends of polystyrene with polypropylene and blends of polystyrene with high‐density polyethylene were used for this study. A plunger‐type injection molding machine (Van Dorn) was employed for molding specimens. To improve the mixing performance of the plunger machine, a Static Mixer (Kenics Corp., Super Nozzle) was installed between the heating cylinder and the sprue. A number of different molding conditions (injection pressure, temperature, injection time, cooling time) were varied, and molded specimens were collected under each molding condition. The specimens were used for studying the degree of dispersion in the blends and for determining the mechanical properties. A differential thermal analysis (DTA) experiment was also carried out to determine the degree of dispersion of the blends in molded specimens. It was found that a linear correlation exists between the blend composition and thermal spectra area of the blends tested.
Pyrolysis–molecular weight chromatography–vapor‐phase infrared spectrophotometry: An on‐line system for analysis of polymers. III. Thermal decomposition of polysulfones and polystyrene
Authors: Kiran Erdoǧan , Gillham John K. , Gipstein Edward
Published: April 2003

The thermal decomposition of poly(butene‐1 sulfone), poly(pentene‐1 sulfone), poly(hexene‐1 sulfone), poly(styrene sulfone), and polystyrene was investigated in helium at a heating rate of 20°C/min using an experimental system which consists of a programmable pyrolyzer, a thermal conductivity detector, a mass chromatograph, and a vapor‐phase infrared spectrophotometer. Poly(butene‐1 sulfone), poly(penetene‐1 sulfone), and poly(hexene‐1 sulfone) displayed two‐step decomposition; the primary products of decomposition at both steps were the comonomers (olefin and SO2). For poly(styrene sulfone), in addition to styrene and SO2, products with molecular weights corresponding to dimers of styrene were observed. Decomposition of this polymer was compared with that of polystyrene, which formed mostly monomer.
A comparison of melt fracture initiation conditions in capillaries and slits
Authors: Vlachopoulos J. , Chan T. W.
Published: April 2003

An experimental study was carried out with the objective of comparing the critical conditions for the onset of gross extrudate distortion, usually called melt fracture, in capillaries and slits. Narrow and broad molecular weight distribution polystyrenes as well as low‐ and high‐density polyethylenes were used. The onset of melt fracture was observed to take place at higher shear stresses in slits than in capillaries. It is argued that the flow‐average value of the recoverable shear strain should be used as the criterion for the initiation of melt fracture.
Thermal degradation of polymers. XV. Vacuum pyrolysis studies on poly(p‐methoxystyrene) and poly(p‐hydroxystyrene)
Authors: Still R. H. , Whitehead A.
Published: April 2003

The monomers p‐hydroxystyrene (p‐HS) and p‐methoxystyrene (p‐MS) have been synthesized and polymerized using azobisisobutyronitrile as free‐radical initiator. The polymerization behavior of p‐HS is anomalous, and a mechanism is suggested to account for this phenomenon. Poly(p‐hydroxystyrene) (PHS) and poly(p‐methoxystyrene) (PMS) homopolymers have been subjected to vacuum pyrolysis at temperatures in the range of 300–500°C. The products of degradation have been identified and qualitatively and quantitatively analyzed and the degradation behavior of the two systems compared with polystyrene. PHS shows anomalous behavior resulting from the high reactivity of the p‐HS monomer and the facility for transfer afforded by the proton of the hydroxyl substituent. Mechanisms to account for the degradation behavior of each system are discussed.
Thermal degradation of polymers. XVI. Thermal analysis studies on poly(p‐methoxystyrene) and poly(p‐hydroxystyrene) in air and nitrogen
Authors: Still R. H. , Whitehead A.
Published: April 2003

Comparative thermal degradation studies have been made in air and nitrogen on polystyrene (PS), poly(p‐methoxystyrene) (PMS), poly(p‐hydroxystyrene) (PHS) and p‐hydroxystyrene/styrene copolymers (p‐HS/S) by thermal analytical methods (TG and DSC). The degradation behavior shown by these polymers in an oxidizing or inert atmosphere is different. PMS and PS, however, degrade in a similar manner in the same test atmosphere, suggesting that similar degradation mechanisms are operative for these systems. Polymers containing p‐HS behave differently to PMS and PS in both atmospheres. Their behavior in air is discussed it terms of the antioxidant effect of the phenolic hydroxyl grouping and the related crosslinking reactions. In nitrogen, the anomalous behavior is discussed in terms of the observed carbonization reaction.
Postdecrystallization rates of grafted fibers and their effect on fiber elasticity. I. Effect of zinc chloride concentration
Authors: Williams J. L. , Piatrik Milan , Choi Sam‐Kwon , Stannett V.
Published: April 2003

Rayon yarns grafted with poly(ethyl acrylate) become highly elastic following decrystallization in aqueous zinc chloride solutions. An increase in temperature speeds up the decrystallization rate but does not have a substantial effect on the ultimate elongation properties of the grafted fiber. Increasing the concentration of zinc chloride does not have a marked change in the extension properties of the grafted fiber until 70% zinc chloride. At this saturated concentration, there is a sudden and dramatic change in the elastic properties of the grafted fiber. In fact, the grafted fibers after decrystallization in 70% zinc chloride have elongations in excess of 800%.
Graft copolymerization of vinyl monomers onto modified cottons. VIII. Dimethylaniline–benzyl chloride‐induced grafting of methyl methacrylate onto partially carboxymethylated cotton
Authors: Hebeish A. , El‐Rafie M. H. , Khalil M. I. , Bendak A.
Published: April 2003

The feasibility of dimethylaniline (DMA)–benzyl chloride (BC) mixture to initiate graft polymerization of methyl methacrylate (MMA) onto partially carboxymethylated cotton was examined. The graft yield depends on the nature of the solvent used along with water; ethanol proved to be the best at a water;ethanol ratio of 90:10. Considerable grafting occurred in the presence of acetic acid at a concentration of 200 mmol/l. Higher concentrations of this acid decrease grafting significantly. The graft yield obtained in the presence of formic acid was much lower than that obtained in the presence of acetic acid. Inclusion of hydrochloric or sulfuric acid in the graft polymerization system prevent grafting. A DMA–BC mixture at a concentration of 0.08:0.087 mole/l. constitutes the optimal concentration for grafting. This contrasts with 0.32:0.35 mole/l. for total conversion. The rate of grafting increases by raising the polymerization temperature; it follows the order 50°>60°>65°>70°>75°C. Furthermore, increasing the monomer concentration caused a significant enhancement in the graft yield and total conversion.
Multiple steady‐state solutions in an isothermal perfectly mixed flow reactor
Authors: Ahmad Abu , Treybig Mike N. , Anthony Rayford G.
Published: April 2003

The effect of multiple steady solutions in isothermal perfectly mixed flow reactors is illustrated for polymerizations which have autocatalytic rates of initiation and no termination reactions. For feed conditions where more than one steady condition can exist, longer holding times may not necessarily yield higher molecular weight polymer or higher monomer conversions.
Graft copolymers of starch–polyacrylonitrile prepared by ferrous ion–hydrogen peroxide initiation
Authors: Stout Edward I. , Trimnell Donald , Doane William M. , Russell Charles R.
Published: April 2003

The effect of concentration, reactant ratios, temperature, and starch pretreatment on grafting of acrylonitrile onto starch were studied. Grafting was efficient at high concentrations (8–12% starch) when granular starch was used. The molecular weights for grafted polyacrylonitrile (PAN) were higher when gelatinized starch was used, but grafting efficiencies (grafted PAN/total PAN) were much lower. The molecular weight of the grafted side chain increased with increased concentration of reactants. The grafting frequency was highest when the reaction mixture was kept at 5°C and decreased with increased swelling of the starch. The starch–polyacrylonitrile graft copolymers were saponified and dried to give products which absorbed 75–440 ml H2O per gram and 20–70 ml synthetic urine per gram.
Poly(aryloxyphosphazenes) and a flame retardant foam
Authors: Thompson James E. , Reynard Kennard A.
Published: April 2003

Plastics and elastomers were prepared, physical state determined by the side chains attached to the phosphorus–nitrogen backbone. The poly(aryloxyphosphazenes) displayed a high degree of flame retardancy in the uncured, unfilled state. Limiting oxygen index (LOI) values varied from 27 to 33 for nonhalogenated materials and from 38 to 65 for halogenated materials. These values qualify all poly(aryloxyphosphazenes) studied as flame retardants according to the generally accepted definition (LOI ≥ 27). Materials subjected to the National Bureau of Standards Smoke Test gave encouraging results. The [(C6H5O)2PN‐(4‐C2H5C6H4O)2PN]n elastomer was investigated for application as a fire retardant insulating foam. Closed‐cell foams produced from this copolymer showed much improved fire retardancy and smoke generation compared to commercially available fire retardant foam insulations.
Changes in NMR characteristics of cotton and wool during water adsorption
Authors: Svanson S. E.
Published: April 2003

NMR signals have been followed for cotton and wool materials during humidification of the fibers. It is shown that the adsorbed water is present in two main states of different mobilities and that the relative velocities for the penetration of the water to these different states can easily be followed. It has been observed that the amount of adsorbed water with low mobility, in the primary sites, grows more rapidly in cotton than in wool during the sorption. Overlap between the signal contributions from water with reduced mobility and from the polymer chains makes observations of the segmental mobility of the polymer chains difficult.
Viscosity index. II. Correlation with rheological theories of data for blends containing n‐octadecyl acrylate
Authors: Jordan Edmund F. , Smith Stephen , Zabarsky Ruth D. , Austin Robert , Wrigley A. N.
Published: April 2003

The viscosities obtained for the copolymer blends of the previous paper were correlated with several relations derived to describe more fundamental behavior of polymer–diluent mixtures at both infinite dilution and finite concentrations. Only the most efficient blends showed any appreciable expansion of hydrodynamic volume as temperature increased from 25° to 98.9°C. However, in spite of restricted coil expansion, all of the copolymers were effective viscosity index improvers. The mechanism of viscosity index improvement in multigrade oils was shown to be largely regulated by the translational friction generated by the polymer coils. This greatly increased the apparent negative entropy change of the blends; the enthalpy change characteristic of the base oil was retained. Efficiency resulted from coil contraction at low temperatures, but enthalpy decrease below that of the base oil was small. In contrast, viscosity index improvement using higher molecular weight solvents was accompanied by large enthalpy increases. Thus, undesirably high viscosities resulted at low temperatures. The structure of these blends was uncomplicated by polymer chain entanglements; unit values of the Fox‐Flory exponent were obtained for the relation between viscosity and weight‐average carbon backbone length. The lack of evidence for coil compression in the thermodynamically miscible blends above a critical reduced concentration was anomalous. Intermingling of side chains and their interaction may have overcome normal excluded volume effects.
The effect of carriers on drawn poly(ethylene terephthalate) filaments
Authors: Ingamells W. , Yabani A. M.
Published: April 2003

The effect of various organic compounds on the birefringence equilibrium shrinkage and swelling of poly(ethylene terephthalate) filaments was studied. Evidence is presented that suggests the carrier action of the compounds is dominated by dispersion forces and that interaction between dye and the carrier in the fiber has been detected.
Swelling and glass transition relations for epoxy matrix material in humid environments
Authors: McKague E. Lee , Reynolds Jack D. , Halkias John E.
Published: April 2003

An experimental investigation has established coherent data sets describing effects of moisture absorption upon swelling and glass transition of an epoxy resin. Equilibrium moisture absorption levels and resultant swelling can be represented by power law functions of relative humidity and quantity of absorbed moisture, respectively. Depression of glass transition temperature is shown to be described by a relationship derived from free‐volume theory.
Water transport through reconstituted collagen hollow‐fiber membranes
Authors: Viswanadham R. , Agrawal Dinesh C. , Kramer Edward J.
Published: April 2003

The hydraulic permeability κ of reconstituted collagen hollow‐fiber membranes has been determined from measurements of the volumetric flow rate of aqueous solutions through the membrane for various pressure differences across the membrane. Increasing the ultraviolet crosslinking time during manufacture of the membrane markedly decreases κ, whereas decreasing the pH of the aqueous solution increases κ. Applying a tensile strain of only 10% along the fiber axis decreases κ approximately fivefold. These results are in good agreement with those expected from a recent model of the membrane structure in which collagen fibrils, oriented preferentially along the hollow‐fiber axis, bend between crosslinks to accept water in a pore structure. If the average fibril volume fraction and diameters are known, estimates can be made of κ. These estimates, based on direct small‐angle x‐ray scattering measurements of fibril diameters, are in good agreement with the measured κ values.