bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractIn 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

AbstractABA‐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

AbstractPoly(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

AbstractA 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

AbstractIn 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractDiffusion 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

AbstractCellulose 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

Abstractcis‐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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractLong‐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

AbstractThe 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

AbstractTwo 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

AbstractThe 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

AbstractIn 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

AbstractThermal 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.
Blocking and copolymer heterogeneity in anionic copolymerization in industrial reactors
Authors: Mehta Rajesh U. , White James L. 
Published: April 2003

AbstractAn 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

AbstractA 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

AbstractA 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.