bluuebunny/crossref_metadata_2025 huggingface dataset:
Aqueous degradation of polyimides
Authors: DeIasi R. , Russell J.
Published: April 2003

The effect of an aqueous environment on the tensile properties of Kapton polyimide film has been investigated. Immersion of specimens in distilled water at 25° to 100°C for time periods ranging from one hour to several hundred hours resulted in a decrease in the ultimate tensile strength of the polymer from 23 ksi to approximately 14 ksi, and a corresponding decrease in elongation to failure from 38% to approximately 5%. The kinetics of this decrease in mechanical properties are second order and yield an activation energy of approximately 15.6 kcal/mole. The reaction is slightly dependent on pH in the range 2.0 to 12.0, but is highly dependent on the pH in the range 0.4 to 2.0. The decrease in mechanical properties at pH 2.0 to 6.0 appears to be due to hydrolysis of either uncyclized amic acid linkages or diamide functional groups present in the polyimide, whereas that at pH below 2.0 is probably the result of hydrolysis of both imide and amide bonds. Prolonged reflux of the polyimide in water resulted in the extraction of a water‐soluble, amide‐containing material.
Radiation grafting of vinyl monomers onto wood pulp cellulose. Part I
Authors: Oraby W. , Hopfenberg H. B. , Stannett V.
Published: April 2003

The effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably.
On creep test loading for soft polymers
Authors: Kobayashi Akira , Ohtani Nobuo , Ino Shuji
Published: April 2003

The dead‐weight loading speed in the creep test for soft polymers was investigated. The optimum dead‐weight loading speed can be determined so as to assure instantaneous elastic deformation and, at the same time, also avoid dynamic effects. It is found that small dynamic effects are inevitable for soft polymers such as polypropylene even at optimum speed. The experimentally determined optimum dead‐weight loading speed for polypropylene was 300 mm/min for 30 kg dead‐weight at 16°C.
The pyrolysis of wool and the action of flame retardants
Authors: Ingham Peter E.
Published: April 2003

The thermal degradation of untreated wool and wool treated with a number of flame retardants has been studied in a variety of atmospheres using thermogravimetric analysis and pyrolysis–gas chromatography. The major products of pyrolysis have been identified and their amounts determined. Gas evolution curves have been determined for the main light gases evolved.
Reaktionsverlaut während der härtung eines epoxidharzes mit dizyandiamid
Authors: Eyerer Peter
Published: April 2003

Nach einem kurzen Überblick über bisherige Untersuchungen an Epoxidharz–Dizyandiamid‐Systemen, wurde der Reaktionsverlauf eines handelsüblichen dizyandiamidhärtenden Epoxidharzes mittels Ultrarotspektroskopie verfolgt und mit den Ergebnissen früherer anderer Methoden am gleichen System verglichen. Dabei ergaben sich gute Übereinstimmungen hinsichtlich charakteristischer Reaktionszeiten (Polymerisationsbeginn, Polyadditionsbeginn, Vernetzungsende). Die Aktivierungsenergie für das Vernetzungsende wurde zu 20 kcal/mol bestimmt. Infolge einer Sedimentation der Dizyandiamidkristalle kommt es vor dem Polyadditionsbeginn zu einem völligen Entmischen von Harz und Härter. Mit Hilfe der Mikrohärtemessung ist es gelungen, den Reaktionsverlauf auch über der Schichtdicke zu erfassen. Zumischen von Quarzmehl verhinderte ein Absinken des Härters. Dadurch konnte die als Schwachstelle für Zugfestigkeitsmessungen wirkende Grenzschicht zwischen abgesunkenem Dizyandiamid und härterfreiem Epoxidharz vermieden werden. Außerdem erfolgte die Aushärtung über der Schichtdicke gleichmäßig. Als Folge ergaben sich für die gef¨︁llten Proben wesentlich höhere Zugestigkeiten.
Fractionation of linear polyethylene with gel permeation chromatography. IV
Authors: Nakajima Nobuyuki
Published: April 2003

Reproducibility was examined on the GPC fractionation of linear polyethylenes. The experiences over the period of two and a half years were used. Calibration was done with the same batches of narrow distribution polystyrene standards. A control sample of broad‐distribution polyethylene was run at each calibration. The reproducibility over ten calibrations with this control was in terms of standard deviation of ca. ±10% for the number‐average and ca. ±15% for the weight‐average chain length. The fractionation data of 36 commercial resins were corrected by using the control samples as an additional standard. The correction was very effective in decreasing the scattering of the data in the intrinsic viscosity–molecular weight plot, especially when the viscosity average was used for the molecular weight expression.
Fatigue of teflon bladder materials
Authors: Cuddihy Edward F.
Published: April 2003

The fatigue properties of Teflon laminates employed in the fabrication of liquid propellant expulsion bladders were studied by cyclically stretching specimens to constant load in order to achieve a correlation of cycles to failure versus the maximum stress amplitude. This approach provides a useful technique for evaluating the resistance of bladder materials to fatigue failure which could be caused by vibration‐induced cyclic loadings during ground testing and launch. Further, the data provides for a direct comparison of the relative fatigue properties of Teflon laminates and, in particular for those which were studied, the relative fatigue properties correlated with their ultimate breaking stresses. This observation, which suggests a simple and rapid method for evaluating relative fatigue behavior of candidate Teflon laminates, is discussed along with the effect of delamination on the fatigue properties observed for one laminate.
Polymer structure formed in radiation‐induced graft polymerization
Authors: Matsuzaki Kei , Kanai Taiichi , Morita Nobuyuki
Published: April 2003

Methacrylic acid (MAA) and methyl methacrylate (MMA) were grafted onto nylon 6, cellulose triacetate, cotton, viscose rayon, and polyester fibers, and the stereoregularities of the grafted polymers were determined. The graft polymerization was carried out with preirradiation techniques using γ‐rays from a Co 60 source. The grafted copolymers were then separated from the homopolymers by Soxhlet extraction. The grafted (branch) polymers were isolated from the trunk polymers by acid hydrolysis and their stereoregularity was determined with a 100 MHz NMR spectrometer. The stereo‐regularity of PMAA or PMMA grafted onto viscose rayon or cotton fiber was different from that of the polymers formed in ordinary radical polymerization.
Pyrolysis and combustion of cellulose. II. Thermal analysis of mixtures of methyl α‐D‐glucopyranoside and levoglucosan with model phosphate flame retardants
Authors: Hendrix James E. , Drake George L. , Barker Robert H.
Published: April 2003

The thermal degradation of methyl α‐D‐glucopyranoside, a cellulose model of intermediate complexity, was investigated in an attempt to gain insight into the pyrolytic reactions of analogous cellulose systems. The pure glucoside pyrolysis proceeds through formation of an intermediate of higher thermal stability. Nitrogenous bases bring about decomposition of the glucoside at lower temperatures and without formation of a detectable intermediate. Phenyl phosphates and phosphoramides induce thermal degradation of methyl α‐D‐glucopyranoside at lower temperatures than observed for the pure glucoside. The postulated degradation mechanism involves esterification of the glucoside followed by dehydration and skeletal rearrangements. Nitrogenous bases assist the dehydration process but reduce the yield of residue and bound phosphorus. Levoglucosan, the cellulose degradation product responsible for flaming combustion, was pyrolyzed in the presence of model flame retardants. Nitrogenous bases were found to inhibit thermal polymerization of levoglucosan and to induce its decomposition at lower temperatures. Zinc chloride exerted its effects in two stages: acid‐catalyzed polymerization at lower temperatures and dehydration at higher temperatures. Phenyl phosphates and phosphoramides alter levoglucosan pyrolysis by action as Lewis acids in a manner similar to zinc chloride.
Color stabilization of poly(vinyl chloride) against high‐energy electron irradiation
Authors: Albarino R. V. , Otocka E. P.
Published: April 2003

Color stability in irradiated PVC may be achieved by (1) structural modification to block dehydrochlorination, (2) addition of radiation protectors, or (3) addition of radical scavengers. This study explores the latter approaches. Twenty‐six compounds representing a variety of structural types were screened for their effectiveness as measured by subsequent color development. Fifteen of the compounds imparted partial or complete postirradiation stability. Possible stabilizer mechanisms are discussed.
Spinning of poly(ethylene terephthalate) fibers from a melt pool without a spinneret
Authors: Wampler F. C. , Gregory D. R. , Kennedy W. D.
Published: April 2003

Monofilament fibers were spun continuously from the free surface of a pool of molten poly(ethylene terephthalate) without the aid of a spinneret. For take‐up velocities in the range of 12 to 400 ft/min, the denier of the filaments produced was an inverse power function of take‐up velocity, and the birefringence was an inverse power function of the filament diameter. Production rate and product uniformity were strongly dependent on take‐up velocity and surface temperature of the melt pool.
Preparation and properties of ABA block polymers of styrene and butadiene or isoprene made with sec‐C4H9Li·2(C2H5)2O
Authors: Cunningham Robert E. , Wise Mary L.
Published: April 2003

ABA‐type “tapered” block polymers were prepared from styrene (monomer A) and butadiene or isoprene, using an initiator of sec‐butyllithium complexed with two molecules of ethyl ether. The stress–strain curves of polymers containing about 20–50% styrene show the usual resemblance to curves of crosslinked elastomers. The SBS polymers had higher tensile strengths than the SIS polymers. They also had slightly higher tensile strengths than comparable SBS polymers made with sec‐butyllithium. The SIS polymers, however, had generally lower tensile strengths than those made with sec‐butyllithium. This is probably caused by higher styrene content of the isoprene block, brought about by increased randomization of the styrene–isoprene copolymerization due to the presence of the ether. The A and B blocks become more compatible, producing loss of strength in the polymer. Infrared analyses of polydienes made with the sec‐C4H9Li·2(C2H5)2O initiator showed a 6% to 8% increase in 1,2‐content (for polybutadiene) or 3,4‐content (for polyisoprene), compared to polymers made with sec‐butyllithium. The polymer microstructures still have high (>80%) total 1,4‐content, however. Thus, this amount of ether can be tolerated in the polymerization system without great loss of rubbery properties or block structure in the resultant polymers.
Thermal properties of unfilled cast cured sheets of polyesters based on bisacid A2
Authors: Lenk R. S.
Published: April 2003

The synthesis of bisacid A2 in a high state of purity, the preparation of unsaturated copolyesters therefrom, the preparation of solutions of the latter in suitable monomers, followed by casting of those solutions after addition of catalysts and curing of the material to obtain crosslinked polyester sheet, has been described in earlier communications.1–3 This paper deals with the heat distortion temperatures4 and the (modified) Vicat softening points5 of the cast sheets of various copolyesters at various monomer contents.
A new structural parameter of polymers–the relative number of network bonds per unit volume
Authors: Holliday L. , Holmes‐Walker W. A.
Published: April 2003

In this paper we define a new structural parameter of polymers, and show how this may be employed. This parameter, for which only the structure and the density are needed, is the relative number of network bonds per unit volume; it is written Ner (basis 1 cm3), and it is used in conjunction with the average connectivity or connection number CN of the network atoms, where the word connection also refers only to network bonds. The relationship of these two numbers makes it possible to present a unified picture of all polymers, organic and inorganic, including such highly condensed networks as diamond. By plotting Ner against CN, the region in which inorganic and organic polymers occur can be seen. This is called the polymer zone, and it is evident that carbon polymers occupy only a small part of it. From this graph, an arbitrary measure of bond packing efficiency can be deduced for carbon polymers. In addition, the process of graphitization and carbonization can be followed graphically within the polymer zone. Ner is also related to certain physical properties such as bulk modulus, hardness, and cubical coefficient of expansion, which depend (among other things) on the tightness of bond arrangement. The resultant correlations can be used to predict the value of Ner required to achieve given values of these properties for the more rigid structures.
Preparation and stress–strain properties of SBS and SIS block polymers made with dilithium initiators
Authors: Cunningham Robert E. , Auerbach Melvin , Floyd Walter J.
Published: April 2003

ABA‐type block polymers of styrene (monomer A) and isoprene or butadiene were prepared using two commercially available dilithium adducts of isoprene as initiators. One (DiLi‐1) was predominantly dilithio diisoprene and contained a small amount of dimethyl ether (ether/Li > 1.0). The second (DiLi‐1 C.E.) was a higher molecular weight version of DiLi‐1, containing about seven isoprene units per molecule. It contained only a trace of dimethyl ether (ether/Li < 0.1). Polymers were made by charging all of the monomers at the start of the reaction. The diene polymerized first, incorporating some styrene. When the diene was consumed, the difunctional polymer chains then added a block of nearly pure polystyrene at each end. Thus an ABA‐type polymer was synthesized in one step. These polymers show the usual behavior of pseudo‐vulcanized elastomers. Their stress–strain curves are given. The SBS polymers had the higher tensile strengths. None had tensile strengths as high as SBS or SIS polymers made with n‐ or sec‐butyllithium. It was shown that the diene blocks contain appreciable amounts of styrene. This leads to more compatibility between the A and B blocks; it also shortens the styrene blocks compared to the theoretical lengths of “pure” blocks. Both effects can lead to loss of tensile strength. Microstructures of the diene homopolymers made with these initiators are also given.
Photochemical degradation of poly(ethylene terephthalate). I. Irradiation experiments with the xenon and carbon arc
Authors: Day M. , Wiles D. M.
Published: April 2003

Poly(ethylene terephthalate) films were irradiated in a carbon‐arc Fade‐Ometer and in a xenon‐arc Weather‐Ometer. The changes in tensile properties, intrinsic viscosities, infrared absorption, and fluorescence emission spectra resulting from these irradiations were measured. Quantitative comparisons between changes in surface (ATR) and transmission infrared spectra, in conjunction with the other results obtained, have established the importance of surface reactions in the photodeterioration of poly(ethylene terephthalate).
A new instrument for preparative gel permeation chromatography
Authors: Peyrouset A. , Panaris R.
Published: April 2003

A preparative liquid‐phase chromatograph was built for the purpose of obtaining sufficiently large quantities of very narrow fractions of different polymeric species, such as polystyrene, PVC, polybutadiene, and polyethylene. This apparatus allows the fractionation of approximately 20 g of polymer per day; the fractions so obtained have polydispersities of about 1.1 over a very wide range of molecular weights. Polydispersities of less than 1.01 were obtained after recycling of the sample.
Effect of metallic ions in photo‐induced graft copolymerization onto cellulose
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

In photo‐induced graft copolymerization of methyl methacrylate onto cellulose, the effect of metallic ions as sensitizer was investigated. Some metallic ions were effective in their adsorbed states and accelerated the formation of grafts in the order Fe2+ > Ag+ > Fe3+. However, Cu2+ acted negatively, and little effect was observed for Co2+, Ni2+, Mn2+, Zn2+, and Cr3+. In the systems in which aqueous metallic salt solutions were added, the formation of grafts was generally depressed, but Fe3+ was an exception. The effect of metallic ions on the scission reaction of cellulose main chains did not necessarily agree with the effect on the formation of grafts. This is attributed to the varied interaction between cellulose and the different active species produced by irradiation, depending on the type of metallic ions used.
Crystalline character of native and chemically treated egyptian cottons. II. Computation of variance of x‐ray line profile and paracrystalline lattice distortions
Authors: Shenouda S. G. , Viswanathan A.
Published: April 2003

A variance range analysis of the x‐ray line profiles for seven cottons (native, ureatreated, and mercerized) has been carried out to get two estimates of the crystallite size from (1) the slope and (2) the variance intercept. Assuming the crystallite length of cellulose to be the same in ramie and native cottons under ideal conditions of growth, the relative fluctuation of the repeat length along the b‐axis has been calculated for all the samples. This degree of paracrystalline lattice distortions is negatively correlated with the fiber bundle strength at zero gauge and appears to be the same as the imperfections referred to in the weak link theories of fiber strength. While the orientation parameters are also well correlated with strength, the degree of crystallinity does not seem to have any influence. Wilson's rigorous mathematical treatment of the number‐average particle size, in relation to the two estimates from the variance slope and intercept as well as the particle size distribution, has been successfully applied for the first time to cotton fibers leading to a clearer understanding of crystallite size–strength relationship.
Studies on the biaxial stretching of polypropylene film. VII. Refractive index of film measured with abbé refractometer
Authors: Tanaka Hiroshi , Masuko Toru , Okajima Saburo
Published: April 2003

The refractive index of a film measured with an Abbé refractometer differs often depending on which surface of the film faces the refracting prism of the refractometer. This phenomenon was elucidated by using well‐characterized films especially prepared for the purpose. The experimental results led to the conclusion that the measurement with an Abbé refractometer gives the refractive index of the film surface facing the refracting prism independently of the refractive index distribution within the film. The importance of this conclusion is stressed in relation to the structural studies of polymer films, especially of biaxially stretched films.
Characterization of nylon 66 by gel permeation chromatography
Authors: Dudley M. A.
Published: April 2003

The quantitative characterization of nylon 66 of various polydispersities has been carried out by gel permeation chromatography (GPC), using m‐cresol solvent at 130°C. A Q‐factor value of 13.9 for nylon 66 has been validated, by limiting viscosity‐number determinations for the particular solvent/temperature combination described above. Using this value together with a simple correction technique for viscous fingering and unsymmetrical dispersion, the practical quantitative characterization of linear nylon 66 has been achieved. Construction of a universal calibration curve, based on hydrodynamic volume, gave a straight‐line relationship for polystyrene fractions and nylon 66 samples covering a broad range of polydispersity values.
Diffusion of poly(vinylpyrrolidone) through cellulose ester membranes
Authors: Jellinek H. H. G. , Blom B.
Published: April 2003

Diffusion coefficients of poly(vinylpyrrolidone) in aqueous solutions were ascertained by the diaphragm method as a function of molecular weight and temperature using mixed cellulose ester (Millipore) membranes. The results agree satisfactorily with diffusion coefficients obtained by other methods. Separation of polymer according to molecular size takes place on diffusion as a function of membrane pore diameter. Also, interaction between the polymer and membrane has been observed resulting in a distribution coefficient between solution and membrane larger than 1. The energy and entropy of activation, repectively, increase with polymer chain length, and their magnitudes are in agreement with the view that segment mobility is operative for the diffusion process.
Studies in chemically modified celluloses. IV. Lactones in chemically modified celluloses
Authors: Shenai V. A. , Sudan R. K.
Published: April 2003

Cellulose has been modified by hydrolysis followed by oxidation with chlorous acid to produce gluconic carboxyl groups, which can form only δ‐lactones. A method has been described for reducing these gluconic acid groups by sodium borohydride into alcoholic groups. Iodometric and alkalimetric methods were used for estimating the carboxyl value of various chemically modified samples.
Determination of the molecular weight distribution of polyisoprene by random scission
Authors: Booth C. , Harlan J. T.
Published: April 2003

cis‐Polyisoprene in dilute solution in toluene (plus antioxidant) undergoes random scission when exposed to γ‐radiation. The possibility of using this scission in a method to assess the width of the molecular weight distribution of the polymer has been explored and found potentially useful in situations where conventional methods provide little information.
Transfer of gas to dissolved oxygen in water via porous and nonporous polymer membranes
Authors: Yasuda H. , Lamaze C. E.
Published: April 2003

The transfer rates of oxygen via polymer membranes in gas–membrane–gas and gas–membrane–water (dissolved oxygen) were investigated with various porous membranes and compared with results of silicone rubber sheet (nonporous, homogeneous polymer membrane). With a nonporous membrane, the permeability constant obtained by gas–membrane–gas represents the true membrane permeability in gas–membrane–water system, and consequently the transport resistance due to boundary layer can be quantitatively estimated. With a porous membrane, the data in gas–membrane–gas system (under applied pressure) merely represent the gas effusion rate of the membrane and are not directly related to the dissolved oxygen transfer rate in gas–membrane–water system. The penetration of liquid water into the pores of porous membrane is the most important controlling factor for the dissolved oxygen transfer rate of a porous membrane. With a porous membrane in which liquid water does not penetrate into the pore, the overall transfer rate of dissolved oxygen reaches the level which corresponds to that of the boundary layer found with silicone rubber membrane.
Molecular weight distribution in a poly(vinyl chloride–vinyl acetate) copolymer
Authors: Chen H. R. , Blanchard L. P.
Published: April 2003

The molecular weight distribution of a vinyl chloride–vinyl acetate copolymer has been studied by three methods: (a) solution fractionation; (b) osmometry and light scattering; (c) gel permeation chromatography. In (a), the fractions were precipitated from a tetrahydrofuran solution by water, then characterized. The data yielded models for the intrinsic viscosity and the molecular weight distribution, in terms of the copolymer molecular weight. In (b), the unfractionated copolymer was characterized by osmometry and light scattering, using in the latter case the two currently accepted theories for the determination of the true weight‐average molecular weight. Conflicting data suggest caution in the use of these theories. In (c), the original fractions served to establish a calibration curve which yielded exceptionally low results when applied to the analysis of the unfractionated VC–VAc copolymer. Further investigations using proposed universal calibration theories bring to light serious discrepancies.
Studies in radiation‐induced polymerization of vinyl monomers at high dose rates. I. Styrene
Authors: Squire D. R. , Cleaveland J. A. , Hossain T. M. A. , Oraby W. , Stahel E. P. , Stannett V. T.
Published: April 2003

The kinetics and degree of polymerization of the radiation‐induced polymerization of styrene were investigated at dose rates up to 3 Mrads per sec. It was found that both the polymerization rates and the molecular weights at high dose rates lie well above the values predicted by extrapolation from low dose rate studies where the mechanism is primarily free radical in nature. The evidence obtained indicates that with increasing dose rate there is an increase in the ionic contribution to the polymerization mechanism. At the highest dose rates investigated, 3 Mrads per sec, the ionic mechanism dominates while the free‐radical mechanism contributes insignificantly. There was no inhibition of the polymerization of styrene by dissolved air at the higher dose rates. Investigation of the polymerization of styrene saturated with water tends to support the ionic mechanism via free cations. Investigation of equimolar solutions of styrene and methyl methacrylate further support the ionic mechanism, yielding predominately polystyrene and a small amount of 50–50 copolymer. In the intermediate dose rate range, 1000 rads per sec, there is evidence that the high dose rate free‐radical kinetic mechanism is the principal mechanism.
Hydrodynamic resistance and flux decline in asymmetric cellulose acetate reverse osmosis membranes
Authors: Baayens L. , Rosen S. L.
Published: April 2003

Long‐term flux‐versus‐time measurements were made on a series of homogeneous, dense cellulose acetate (39.8% acetyl) membranes. All tests were carried out at 1500 psi applied pressure on a 3.5% NaCl feed. These tests show that essentially all the resistance to solvent (water) flow in the typical asymmetric reverse osmosis membrane is concentrated in the thin dense layer. Further, the evidence strongly suggests that the longterm flux decline noted in asymmetric membranes is a result of viscoelastic deformation of the dense layer.
The quasi‐stationary state approximation in polymerization kinetics
Authors: Biesenberger J. A. , Capinpin R.
Published: April 2003

The errors incurred in free‐radical chain addition polymerizations through the use of the popular quasi‐stationary state approximation (QSSA) under severe, but fairly common, reaction conditions are examined in detail, and simple, useful criteria for applicability of the QSSA are proposed. The conditions examined are “dead end” polymerization, polymerization with hindered termination and nonisothermal polymerization. It is concluded that the proposed criteria are reasonably accurate and that in most known free‐radical polymerizations only hindered termination might possibly lead to appreciable errors through application of the QSSA.
The polycondensation of dimethyl terephthalate and ethylene glycol in the presence of dye derivatives of 1,3,5‐sym‐triazine
Authors: Konstantinov Chr. , Konstantinova T. , Draganov A. , Kabaivanov V.
Published: April 2003

Two new triazine‐based dyes have been prepared with the following general formula:
magnified image
in which R = HNCH2CH2OH or NHCH2COOH. As a result of the presence of suitable functional groups, these compounds can be incorporated in the polycondensation process which gives colored polyethylene glycol terephthalates (PEGT). By means of a spectrophotometric investigation, it has been demonstrated that the dye does not change its structure under high temperature or its incorporation in the polymer chain. A colorimetric study has been made of the dye content of the polymer as related to the quantity initially taken for the reaction. It has been shown that the inclusion of the dye in the polycondensation process does not affect notably the molecular weight, melting point, and the polydispersion of the polymers. Intensive coloration can be obtained with very low concentrations of the dye, 0.1–0.5%. By comparing the infrared spectra of the polymer and the pure dyes, the dyes have been demonstrated to be bound to the polymer molecule. Since the dye is part of the basic chain of PEGT, the polymers retain their color after repeated reprecipitation. The proposed method can be used for the preparation of saturated polyesters of divers properties and persistent colors.
Bulk polymerization of vinyl chloride
Authors: Abdel‐Alim Ahmed H. , Hamielec A. E.
Published: April 2003

The bulk polymerization of vinyl chloride initiated by AIBN at temperature levels of 30°, 50°, and 70°C has been studied. Molecular weight averages and distribution (MWD) were measured by gel permeation chromatography. A model has been proposed which accurately predicts conversion to high levels and MWD. Molecular weight measurements show that transfer to monomer plays the important role in controlling molecular weight averages. Disproportionation is probably the dominant mode of termination.
Rate of emulsion polymerization of styrene
Authors: Harada Makoto , Nomura Mamoru , Kojima Hideki , Eguchi Wataru , Nagata Shinji
Published: April 2003

In emulsion polymerization, the Smith and Ewart theory gives about two or three times the number of polymer particles obtained by experiment. In this paper, a reaction model is proposed which, from the standpoint of reactor design, can give an adequate explanation of the whole course of an emulsion polymerization of monomer highly insoluble in water. Among other things, the generating process of polymer particles is examined in detail. It is demonstrated experimentally that a new parameter proposed here, which represents the degree of difficulty of monomer initiation in micelles, is indispensable in explaining that process. Also confirmed is that monomer initiation takes place more easily in polymer particles than in micelles. According to the new model, the progress of polymerization, i.e., monomer conversion, the number of the polymer particles, and properties of polymer thus produced can be estimated with satisfactory accuracy. Furthermore, approximate equations are derived for easier estimation.
Volatile combustion products of polycarbonate and polysulfone
Authors: Ball Gwendolyn L. , Boettner E. A.
Published: April 2003

Thermal analysis of polycarbonate and polysulfone has shown each plastic to undergo a two‐step decomposition, the first step involving production of high‐boiling chain scission and volatile products, the second resulting, in addition, in production of large amounts of carbon dioxide and carbon monoxide. Ten to fifteen volatile products of each plastic have been quantitatively analyzed under several combustion conditions and also in several temperature ranges chosen on the basis of TGA curves. Polycarbonate products include a moderate amount of methane, small amounts of other aliphatic hydrocarbons through C5, methanol, acetaldehyde, and several aromatics. Volatile products account for 40–60% of polycarbonate, with phenol and substituted phenols predominating in the large amount of liquid residue formed during chain scission. Polysulfone produces very similar hydrocarbon products as well as sulfur dioxide, which accounts for 85–96% of the sulfur of the plastic, and carbonyl sulfide, which was only detectable during the temperature range 490°–550°C. Volatile products account for 50–60% of polysulfone.
Protection against intense light. III. The use of commercial dyes in thermal protection
Authors: Prosser R. A.
Published: April 2003

Experimental evidence is offered showing that commercial dyes can be used to provide protection against intense light energy. An estimate of the amount of material required/cm2 to protect the skin, clothing, or houses is given.
Blocking and copolymer heterogeneity in anionic copolymerization in industrial reactors
Authors: Mehta Rajesh U. , White James L.
Published: April 2003

An analysis is given of the effect of reactor design on the variation of composition and extent of blocking in anionic copolymerization. Batch, pipeline, continuous stirred tank (CSTR), and recycle reactors are contrasted. Specifically, alkyl lithium‐polymerized butadiene–styrene and alkyl sodium‐polymerized p‐methylstyrene–styrene are contrasted to the products of copolymerization of the same monomers by free‐radical mechanism. It is shown for both systems that considerably more extensive blocking occurs in a batch reactor when the anionic polymerization mechanism is used. The free‐radical copolymers, unlike the anionic copolymers, exhibit compositional heterogeneity in a batch reactor. Carrying out the polymerization reaction in a pipeline reactor gives results equivalent to the batch reactor if there is plug flow. However, if a parabolic profile exists in the reactor, there will be significantly increased compositional drift in the copolymer product and a broadened molecular weight distribution, with little effect on blocking. Recycle reactors, including the recirculating loop variety, seem effective in decreasing blocking. The extent of blocking may be considerably decreased in a wellmixed continuous stirred tank reactor. However, poor mixing will greatly increase both the extent of blocking and the compositional heterogeneity of the product.
Thermally stable polyimides from solutions of monomeric reactants
Authors: Serafini T. T. , Delvigs P. , Lightsey G. R.
Published: April 2003

A method to prepare thermally stable resin fiber‐reinforced composites using solutions of appropriate monomers is described. Solutions containing a dimethyl ester of an aryl tetracarboxylic acid, the monomethyl ester of 5‐norbornene‐2,3‐dicarboxylic acid and an aryl diamine were used to impregnate graphite fibers. Composites fabricated from these prepregs exhibited excellent thermo‐oxidative stability and retention of mechanical properties at 600°F. These results compare favorably with those obtained from composites made from amide‐acid prepolymers capped with reactive alicyclic rings. Monomeric solutions provide excellent shelf life and improved solubility compared to amide‐acid prepolymer solutions.
Optimization of the thermomechanical behavior of a poly(chromium(III) trisphosphinate)
Authors: Gillham J. K.
Published: April 2003

A two‐component reactive system consisting of a poly(chromium(III) bisphosphinate) and dioctylphosphinic acid reacts to form a poly(chromium(III) trisphosphinate). Extensive thermomechanical hysteresis is displayed throughout the temperature range −180°C to >300°C by specimens containing filaments of glass. Thermal pretreatment to about 400°C (the limit of thermal stability) eliminated these instabilities. These results correlate with the reported brittle and tough character of films of the poly(chromium (III) bisphosphinate) and poly(chromium (III) trisphosphinate), respectively. Regardless of thermal history (between 200°C and 400°C), the polymer system displayed three major transition regions: the glass transition centered at about 0°C, another centered at about 230°C, and a third at about −200°C.
Gas transport in glassy polymers
Authors: Vieth W. R. , Eilenberg J. A.
Published: April 2003

Sorption kinetics and equilibria for CO2 in polycarbonate were studied over a range of temperatures from 35° to 65°C and pressures from 3 to 22 atm. The dual mode sorption model of Vieth et al. was used to test the data, and a comparison was made with previous work on glassy polystyrene. Further evidence of the validity of generality of the model in providing a consistent picture of small‐molecule diffusion in glassy polymers was thereby provided. The technical feasibility of membrane separation of H2 from a H2/CO2 mixture by selective permeation through polycarbonate was examined at 50°C.
On the rheology of molten binary blends of polyolefins. X. Homogeneity and high shear (Poiseuille's) melt flow of polypropylene–polyethylene blends
Authors: Płochocki A.
Published: April 2003

Statistical analysis of inherent viscosities (LVN), shear modulus (G*), and melting temperature (Tm) interval data for isotactic polypropylene–linear polyethylene (HDPE) blends was performed in order to verify their microheterogeneity. High shear measurements in viscometric (Poiseuille's) flow were carried out on four replicated compositions of the blends. Least‐squares treatment of the results yielded power law parameters for the blends differing in composition. The significance of differences between the blends of various HDPE content was tested using the multiple‐range (Duncan's) test, and tentative conclusions are drawn on the composition dependence of the melt flow viscosities of the blends.
Radiation‐induced graft copolymerization of styrene to cellulose
Authors: Guthrie J. T. , Huglin M. B. , Phillips G. O.
Published: April 2003

The radiation‐induced graft copolymerization of styrene to cellulose has been studied in vacuo at 30°C and at dose rates from (0.37 to 8.73) × 10−2 W/kg. Dioxan was used as solvent for monomer and polystyrene homopolymer, and water (2% total volume) was incorporated as swelling agent for cellulose. The concentration of styrene in the bulk medium was varied from 0.432 to 3.46 moles/l., and the rates of both grafting and homopolymerization were shown to be proportional to [monomer] · [intensity]1/2. The value of 3.3 × 10−4 l. mole−1 sec−1 derived for kp2/kt in homopolymerization is similar to that for normal free‐radical polymerization of styrene. However, reduced termination during grafting yielded a much higher value (58 l. moles−1 sec−1). Degradation of cellulose in the absence of monomer was followed viscometrically, and values of 13.5 and 24.6 were derived for G (scission) in vacuo and in air, respectively.
A thermoanalytical determination of the activation energy of the decomposition of azodiisobutyronitrile
Authors: Higgs D. A. , Manley T. R.
Published: April 2003

The decomposition of azodiisobutyronitrile (AZDN) has been studied in a simple, robust apparatus specially constructed for simultaneous study of differential thermal analysis and evolved gas detection (DTA/EGD). The results obtained are comparable with those of other thermoanalytic techniques. It is difficult to obtain kinetic results by the DTA technique alone, as the decomposition is confounded with a melting endotherm. This problem does not arise when EGD is used. The apparatus provides a convenient method for research on blowing agents and is being extended to studies of polymer degradation.
Ultraviolet surface‐photopolymerization from phenol, cyclohexanol, and ethylbenzene
Authors: Christopher A. , Wright A. N.
Published: April 2003

The formation of surface‐photopolymerized films from the vapors of phenol, cyclohexanol, and ethylbenzene is described. The structures of the films are discussed in terms of their multiple‐reflection infrared spectra.
Molecular aggregation in poly(vinyl chloride). A novel analytical technique
Authors: Abdel‐Alim Ahmed H. , Hamielec A. E.
Published: April 2003

A novel experimental technique based on gel permeation chromatography (GPC) has been developed for the measurement of molecular aggregation in poly(vinyl chloride) (PVC). PVC having a range of syndiotacticity was synthesized using polymerization temperatures of 30–70°C. Tacticity and molecular aggregation of these PVC samples were measured by NMR and GPC, respectively. The temperature dependence of molecular aggregation was found to be much greater than that of tacticity. This GPC technique is inherently more sensitive than NMR in the temperature range normally employed for commercial production of PVC. It should find extensive use in the control of PVC reactors and in PVC processing.
Studies on heterogeneous polymeric systems. II. Polyblends containing saturated rubbers
Authors: Baer Massimo
Published: April 2003

Saturated rubbers composed of ethylene–propylene or ethylene–vinyl acetate copolymers and terpolymers were used in the mass polymerization of high‐impact styrene or styrene–acrylonitrile polyblends. Conventional polymerization procedures lead to blends of inferior mechanical properties. The cause for the poor performance was traced to the inability of the rubber‐phase particles to preserve the desired size and particularity during processing.

Polymeric blends of saturated rubbers having mechanical properties comparable to those obtainable with polybutadiene rubbers are prepared by (1) controlling the rubber‐particle size during prepolymerization and (2) preserving such size by crosslinking and grafting of the rubber following phase inversion. Extensive crosslinking of the rubber in the final blend must take place prior to processing to resist rubber particle deformation and disintegration during mechanical working. Rubber vulcanization is realized by the presence of peroxides in the final stages of polymerization; pendant unsaturation in the rubber is also needed or helpful. The reactivity and number of unsaturated groups in the rubber must be controlled to avoid excessive grafting prior to phase inversion and to permit efficient crosslinking following phase inversion.
On the solubility parameter of polar polymers
Authors: Utracki Lechoslaw A.
Published: April 2003

The binary cluster integral, β, was computed from intrinsic viscosity data. Subtracting from β the polar contribution, βe, calculated from YRCR theory,9 the nonpolar interaction parameter, βn, was found. The calculations were performed for poly(vinylacetate) and poly(methyl methacrylate), each in 16 solvents. The correlation between βn and the solvent solubility parameter, δ1, was found to be similar to that reported8,17 for solutions of natural rubber, cis‐polybutadiene and for poly(vinyl chloride). This correlation can be crudely approximated by the formula

where E and F are functions of the ill‐defined symmetry of the solvent molecule and δm is the δ1 value for the local maximum of the function. At δ1 = constant, the more spherical is the molecule, the higher is the βn value. It was shown that for most cases separation of the solvent into two classes (linear and nonlinear) is sufficient. This βn behavior finds support in the Funk and Prausnitz6 report on aromatic–saturated hydrocarbon mixtures and in the theoretical calculations of Huggins.21,22
A scanning electron microscope study of plasma‐polymerized organosilicon films suitable for use as lightguides. A determination of the cause of signal attenuation
Authors: Thompson L. F. , Smolinsky G.
Published: April 2003

The scanning electron microscope was used to evaluate the optical quality of a plasma‐deposited organic film. A major source of signal attenuation in lightguide films results from scattering by microscopic embedded spheres. The spheres are produced in the gas phase, and their size and population density are a function of the substrate surface and the rate of film formation. For all systems studied, the number of spheres increase with increasing rate. High‐quality films were deposited more easily on silicon, silicon dioxide, tungsten, and glass than on Nichrome or β‐tantalum. Gold, copper, and titanium surfaces proved more difficult, while aluminum was the most intractable material encountered. The rate of film growth usually increased with an increase in power input for any ratio of total pressure‐partial pressure of monomer. Spheres were essentially eliminated or their number reduced to a tolerable level by a proper choice of reaction conditions.
A radiotracer study of durability of acrylic soil release polymers to laundering
Authors: Warburton C. E. , Flynn L. T.
Published: April 2003

Cotton/polyester fabrics were treated with 14C‐labeled acrylic soil release polymers, either alone or with a durable press reagent, dimethyloldihydroxyethyleneurea (DMDHEU). Both two‐bath and one‐bath applications were used. Rate of removal of polymer in laundering was determined experimentally by radiotracer methods. Removal was faster in the order polymer alone (no DMDHEU) > two‐bath process > one‐bath process. The difference was much more significant when high molecular weight emulsion polymer was used than partially neutralized low molecular weight solution polymer. It is concluded that condensed DMDHEU serves as a coupling agent to bind polymer to fabric, thereby retarding removal of polymer in laundering. The significance of the results with respect to soil release of treated fabrics is discussed.
The morphological consequences of annealing high‐density polyethylene in solvents
Authors: Blackadder David A. , Keniry John S.
Published: April 2003

When a semicrystalline polymer imbibes solvent molecules at near‐ambient temperatures it is very probable that the crystalline regions are not affected. The noncrystalline regions swell to accommodate the solvent and may also undergo structural changes which are not reversed on removing the solvent. If this happens, the sorptive capacity of the polymer is permanently changed. Pretreating a polymer membrane with liquid solvent has the same effect on sorption measurements as pretreatment with the corresponding saturated vapor only when special precautions are observed. High‐density polyethylene films were used throughout the investigation, and p‐xylene was the organic permeant. Numerous measurements of sorption and permeation rates were made, and the results are discussed in terms of a new model for the behavior of noncrystalline chains in a semicrystalline polymer. The shorter tie molecules running between the crystalline lamellae appear to be of crucial importance, and slight modification of these may have a large effect on the sorptive capacity of the sample as a whole. The possibility of solvent molecules clustering in the swollen polymer is considered in an Appendix.
Estimation of viscosities of mixed polymer solutions
Authors: Rudin Alfred , Hoegy Howard L. W. , Johnston H. Kirk
Published: April 2003

A semiempirical model for estimation of viscosities of concentrated polymer solutions1 can be applied to mixtures of polymers in a common solvent. The data required for estimation of mixture viscosity are: solvent viscosity, polymer molecular weight, density, concentration, and intrinsic viscosity in the particular solvent. Calculated and experimental viscosities agree to within a few per cent for the relatively nonpolar systems for which comparative data are available. The model does not appear to be adequate for mixtures in which there are extensive hydrogen‐bonding interactions.

Results of the new model are equivalent to those of an empirical equation2 reported to be effective for fairly concentrated binary polymer mixtures.

Specific interactions between polymeric solutes can be conveniently assessed by comparing measured mixture viscosity to that calculated from the model presented. It is not clear, however, that such assessments have any fundamental significance, since the interactions which are calculated depend on the assumptions inherent in the estimation of the “ideal” mixture viscosity. The same reservations apply to other models which have been proposed for this purpose.