bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intrinsic viscosity–molecular weight relationship for low molecular weight nylon 6
Authors: Hague P. , Huglin M. B. , Johnson B. L. , Smith J. 
Published: April 2003

AbstractSamples of nylon 6 have been prepared by the hexamethylene diamine‐initiated polymerization of ϵ‐caprolactam at 220°C. Fractionation of these with m‐cresol–diethyl ether at 26°C yielded 15 amino‐terminated fractions of M̄n of 337–10,940 determined conductometrically. Below M̄n = 4,306 the Mark‐Houwink parameters in m‐cresol at 30°C are K = 3.0 × 10−3 dl/g and v = 0.53 ± 0.02. Thereafter v exhibits a pronounced increase. The value of K is similar to the values of Kθ derived from Stockmayer‐Fixman plots of published data in good solvents. The findings thus corroborate a current hypothesis that fractionated, low molecular weight polymers in good solvents tend to behave viscometrically, as if they were under θ conditions (i.e., K = Kθ and v = 0.50).
The effect of temperature on the infrared absorption frequencies of polyethylene and ethylene–propylene copolymer films
Authors: Brockmeier Norman F. 
Published: April 2003

AbstractThe frequency shifts of the six prominent infrared absorption bands were measured for films of polyethylene and ethylene–propylene copolymer as a function of temperature. Three bands (at 720, 731, and 1473 cm−1) shifted to higher frequency, and three bands (at 1463, 2849, and 2918 cm−1) shifted unexpectedly to lower frequency as the sample temperature was decreased. The greatest shift occurred with the CH2 rocking band, which increased from 730.2 to 734.2 cm−1 as the temperature was decreased from 313 to 22°K. The shift usually ceased in the temperature range from 40 to 110°K, probably because some kind of molecular motion ceased. Four mechanisms are discussed in an attempt to account for the different frequency shifts: bulk contraction with decreasing temperature, an increase in dispersion forces between chains, variation in the length and coupling of the vibrating chain molecule, and a change in the planar zigzag conformation of the chain molecule. Thermal contraction is sufficient to explain most of the observed frequency shifts. The CH2 stretching modes (2849 and 2918 cm−1) may be shifted to lower frequency by an increase in the dispersion forces between chains, caused by contraction. The displacement of the 1463 cm−1 band‐shift curve is an indication of the sample density. The displacements of the 1473 and 731 cm−1 band‐shift curves are indications of the proportion of propylene in the ethylene copolymer.
Acid decomposition of highly substituted cellulose xanthate
Authors: Törnell B. 
Published: April 2003

AbstractThe acid decomposition of cellulose xanthate was studied spectrophotometrically with a stopped‐flow technique. The reactivity of the xanthate groups was found to decrease with an increase in the viscose γ number. This was explained by the occurrence of stabilizing interactions exerted between closely spaced xanthate groups. With uniformly substituted xanthates this effect began to be noticeable at γ numbers above 50. At higher γ numbers partial decomposition by acid resulted in an uneven distribution of xanthate groups along the chain molecules. Another feature of cellulose xanthate is that the degree of dissociation at constant acid concentration decreases with an increase in the γ number. This can be ascribed to variations in the dielectric constant inside the macromolecules.
Concentration and pressure dependence of rate of membrane permeation
Authors: Rosenbaum Shlomo , Skiens W. E. 
Published: April 2003

AbstractThe permeation of water and sodium chloride in cellulose acetate membranes has been examined over a wide range of concentration and pressure. The results obtained from reverse osmosis experiments have been used to evaluate relations derived on the assumption that permeation of both solution components takes place by diffusion down a concentration gradient in the membrane. With the aid of equilibrium and raidoactive tracer measurements, most of the deviations could be attributed to nonconstancy of the diffusion, and, especially, the distribution coefficients of water. A comparison of the net flux in reverse osmosis with the rate of tracer permeation in the same membrane provided positive evidence to show that hydrodynamic flow under pressure cannot account for the water flux through the membrane. Differences in the shape of the distribution isotherms for salt and water between solution and membrane provide an explanation for the high selectivity of cellulose acetate membranes in favor of water.
Radiation‐induced graft copolymerization of butadiene on polyethylene by trapped radicals
Authors: Furuhashi Akira , Mukozaka Hiroshi , Matsuo Hiroshi 
Published: April 2003

AbstractThe low‐temperature grafting of butadiene on polyethylene (PE) preirradiated in air is compared with that on PE preirradiated in vacuo for the effect of several factors on the grafting. Little fundamental difference between the two cases was observed. In both cases the graft conversion curve is trapped radical type and the overall activation energies are 9.7 and 8.4 kcal/mol for 0.947‐density PE and 0.916‐density PE, respectively. Percent grafting is proportional to the square root of the dose rate (= total dose). The retarding effect of oxygen at irradiation or storage after irradiation on the grafting scarcely appears when the irradiation temperature or storage temperature is below 15°C. For thinner film and lower density of PE this effect appears clearly at the higher temperature. Therefore, it may be concluded that the low‐temperature grafting of butadiene onto PE preirradiated in air is initiated predominantly by nonoxidized radical (allyl radical) trapped in PE and that the grafting reaction occurs in the semicrystalline part of PE.
Surface tensions of liquid polyisobutylenes
Authors: Edwards H. 
Published: April 2003

AbstractMeasurements of surface tensions were carried out in the temperature range 25–120°C on seven different liquid polyisobutylenes with molecular weights ranging from 100 to 80,000. Relationships between the surface tenstion of polyisobutylene and other properties, such as the parachor, cohesive‐energy density, and molecular weight are discussed.
Polymer reactors and molecular weight distribution. VII. Further development of gel permeation chromatography
Authors: Duerksen John H. , Hamielec Archie E. 
Published: April 2003

AbstractThe results of an investigation into molecular weight and resolution calibration of a gel permeation chromatograph are reported. Effects of sample amounts and solvent flow rate were observed. Severe skewing and tailing of the standard chromatograms were observed at 2.0 ml/min flow rate, relative to 1.0 and 3.0 ml/min. Resolution calibration by flow reversal was inadequate when skewing and tailing or sample impurity effects were significant. Differential molecular weight distributions (MWD) of broad‐distribution polystyrenes were compared for four methods of resolution correction. Inconsistent oscillations were observed in the MWD's at low resolutions and higher molecular weights. None of the methods was completely adequate in accounting for skewing and tailing.
A study of spinnability in the wet‐spinning of acrylic fibers
Authors: Paul D. R. 
Published: April 2003

AbstractAn extensive study of spinnability is presented for the formation of acrylic fibers by wet‐spinning. The system consisted of an acrylonitrile–vinyl acetate copolymer with dimethylacetamide as the solvent and water in most instances as the nonsolvent. The term spinnability is used here to denote the type of filament breakage that occurs in the spin bath near the spinnerette face as the withdrawal speed V1 is increased to some critical value. This maximum speed V1, m depends on essentially every spinning variable. Data are presented for a wide range of spinnerette hole diameters, flow rates per hole, coagulation rates, temperatures, and polymer concentration in the spinning solution. The freely extruded velocity of the filaments, Vf, is also given over the same range of variables. The free velocity is much less than the average velocity because of the Barus effect. Some similarities are noted in the response of V1, m and Vf to certain variables. In fact, V1, m seems to be determined by Vf. Through this observation the influence of the Barus effect on spinnability is easily seen. Spinnability is discussed also in terms of coagulation rates. It is concluded that both rheological and coagulation phenomena are important in the breakage mechanism. These observations are probably applicable in part to other wet‐spinning systems.
Molecular weight distribution and swell properties of some low‐pressure polyethylenes
Authors: Ford R. W. , Ilavsky J. D. 
Published: April 2003

AbstractThe molecular weight distribution of some low‐pressure homopolymers of ethylene intended for use in blown bottles have been determined by using a modified sand column technique. A correlation is indicated between the Z‐average molecular weight M̄z and the postextrusion swelling of the resin as measured by the weight of a bottle blown from that polymer.
Thermal analysis by a constant heat flow
Authors: Steffens Ed. 
Published: April 2003

AbstractA new method of and apparatus for thermal analysis is described, whereby the heat flow fed by the oven to the sample is kept constant as a function of time. The measurement gives the change of enthalpy in heating or cooling the sample. From this enthalpy–temperature relationship quantitative thermodynamic results are easily obtained. Transitions of first and second order in polymers can be measured in one run.
Molar absorptivity of poly(methyl methacrylate) in the near‐ultraviolet region
Authors: Warnock Maureen , Gardner Donald G. 
Published: April 2003

AbstractThe molar absorptivities of methyl methacrylate monomer and of thermally polymerized, monomer‐free poly(methyl methacrylate) have been measured in the range 2200–3000 Å, and smoothed values are presented at wavelength intervals of 20 Å over much of this range. Typical amounts of monomer present in a thermally polymerized bulk polymer and in films cast from CH2Cl2 solutions of the bulk polymer have been ascertained. The use of such absorptivity values to determine the amount of monomer present in polymer samples is evaluated.
Solubility parameters of polymers from turbidimetric titrations
Authors: Suh K. W. , Corbett J. M. 
Published: April 2003

AbstractThe solubility parameters of sixteen polymers have been determined by the turbidimetric titration method. The results agree well with the reported values obtained from swelling and viscosity measurements. The method is sensitive to the choice of nonsolvents and to small changes in the copolymer composition.
A recording, air‐bearing torsion pendulum
Authors: Rodriguez F. , Van Brederode R. A. , Cocks G. G. 
Published: April 2003

AbstractA recording torsion pendulum has been designed which allows the measurement of storage modulus and loss modulus for weak gels. The gel is held in a cone–plate geometry. The 5° cone, along with the inertial elements of the pendulum, is supported by an air‐lubricated bearing. The decay of oscillations is sensed by a Proximeter which does not touch the moving apparatus and which converts the amplitude of oscillation into a de signal of several volts. Storage moduli as low as 40 dyn/cm2 and log decrements as low as 0.0054 have been measured.
Ionic graft copolymerization. IV. Polymerization of β‐propiolactone by acetic acid, p‐toluenesulfonic acid, and their sodium salts
Authors: Shiota Tetsuya , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractAcetic acid, toluenesulfonic acid, and their salts are used as four representative ionic catalysts for polymerization of β‐propiolactone (βPL). They are classified as follows: sodium acetate is an anionic catalyst, acetic acid is a neutral one having more covalent character, sodium toluene sulfonate is a neutral one having more ionic character, toluenesulfonic acid is a cationic one. The neutral catalyst having more covalent nature is hardly dissociated, and therefore the rate of polymerization is quite small; however, dissociated ions consist of a higher neucleophilic anion and a higher electrophilic cation. On the contrary, the neutral catalyst having an ionic bond dissociates more easily, but the formed ions consist of the less reactive anion and cation. Therefore, it is of interest whether β‐propiolactone is polymerized by a cationic mechanism or an anionic mechanism by these catalysts. The mechanisms of polymerizations of βPL by these neutral catalysts were studied on the basis of the different behaviors of polymerizations by the four catalysts described above. In the cationic polymerization by toluenesulfonic acid, the rate of polymerization was high, but the conversion reaches a low, limited value. In the anionic polymerization by sodium acetate, the rate of polymerization was high and the degree of polymerization of polymer was the highest. Acetic acid has the lowest catalyst activity and the degree of polymerization is also very small. It was found that the polymerization by sodium p‐toluenesulfonate was accelerated in the presence of acrylic acid produced from βPL by hydrogen‐transfer reaction.
Ionic graft copolymerization. V. Graft copolymerization of β‐propiolactone onto the trunk polymers containing carboxylic acid, sulfonic acid, and other salts
Authors: Shiota Tetsuya , Goto Yutaka , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

Abstractβ‐Propiolactone (βPL) was graft‐copolymerized onto styrene–divinylbenzene copolymers containing various carboxylates or sulfonates, composed of anions and cations having different electronegativities. In parallel, the mechanism of polymerizations of βPL by relatively neutral catalysts was studied in comparison with the behaviors of graft copolymerizations. In the graft copolymerization onto the trunk polymer containing various carboxylates, a lower electronegativity of countercation favors a higher anionic polymerization activity and the order of rate of polymerization coincides with that of anionic activities of catalysts. On the other hand, in the case of trunk polymer containing sulfonates, a higher electronegativity of countercation favors a cationic polymerization activity, and the order of rate of polymerization coincides with that of cationic activity of catalyst. The order of grafting efficiency at fixed total conversion coincides almost with that of anionic activity. The comparatively higher grafting efficiency in the grafting onto trunk polymer containing carboxylic acid might support an anionic graft copolymerization mechanism by carboxyl anion. The two following mechanisms were proposed for the initiation of the polymerization by the trunk polymer containing sodium sulfonate, in which acrylic acid is transformed from βPL.
Studies in chemically modified celluloses. II. Some aspects of physical properties of chemically modified celluloses
Authors: Kangle P. J. , Nabar G. M. 
Published: April 2003

AbstractThe changes in physical properties such as moisture regain, tensile strength, elongation at break, bursting strength, and resistance to abrasion of cellulose modified with different oxidizing agents such as dichromate–sulfuric acid, sodium hypochlorite in presence of leuco vat dyes, and potassium metaperiodate and of the corresponding products obtained as a result of reduction with sodium borohydride and those by oxidation with chlorous acid have been studied. Results are critically discussed in the light of existing knowledge on the changes that occur in the fine structure as well as in the chemical structure of cellulose during the mentioned modifications. It is pointed out that complex changes in physical properties of cotton cellulose brought about by chemical modification could hardly be evaluated and interpreted in terms of one or two physical or chemical parameters.
Studies of the initiation mechanism of ferric ion–hydrogen peroxide systems in graft copolymerization on cellulose
Authors: Ogiwara Yoshitaka , Ogiwara Yukie , Kubota Hitoshi 
Published: April 2003

AbstractThe decomposition of hydrogen peroxide by ferric ion adsorbed on cellulose, the lowering of the degree of polymerization of cellulose, and the graft copolymerization in the systems containing methyl methacrylate were studied. As the amount of ferric ion adsorbed on cellulose and the concentration of hydrogen peroxide became higher, the amount of decomposition of hydrogen peroxide and the number of scissions of cellulose chains with higher rates at the initial stage of reaction were both observed to increase. It was recognized that the graft copolymerization was hardly initiated, while such initial reactions were proceeding. Assuming that the hydrogen peroxide decomposed with a higher rate was indifferent to the initiation reaction, a certain relationship was found between the amount of ferric ion adsorbed on cellulose ànd the initiation efficiency of hydrogen peroxide in graft copolymerization.
Infrared spectroscopy of graft polymers separated from graft copolymers of wool and silk with methyl methacrylate
Authors: Arai Kozo , Negishi Michiharu , Okabe Takayasu 
Published: April 2003

AbstractThe HCl‐ or papain‐decomposition residues obtained from reduced wool fibers grafted with 1.5–3.0% methyl methacrylate were extractively fractionated successively with cold acetone, hot acetone, and benzene. Each fraction was examined by infrared spectroscopy. Generally, the 715 cm−1 spectral band considered to be due to vc‐s‐c was found in the hot acetone‐soluble fraction. It was concluded that the thiol groups on wool keratin provide the main sites of grafting, as might be expected. A similar result was obtained for grafted silk fibroin fibers, the methionine residue being presumed to be related to some of the grafting sites at least. Furthermore, a sort of stereoregularity was observed in some of the graft polymer fractions, isotactic‐rich material being obtained in the case of silk fibers. In the range of very low grafting, a stereoregulating effect on the structure of the polymer formed within fibers appears to be present in relation to the grafting or adsorption sites of monomers and the fine structure of fibers.
Structure and properties of polyethylene produced by γ‐radiation polymerization in flow system
Authors: Machi S. , Kawakami W. , Yamaguchi K. , Hosaki Y. , Hagiwara M. , Sugo T. 
Published: April 2003

AbstractThe radiation‐induced polymerization of ethylene was carried out by use of a benchscale plant with a flow‐type reactor of 1 liter capacity under the following conditions: pressure, 200–400 kg/cm2; temperature, 30–90°C; irradiation intensity, 3.8 × 105 rad/hr; and ethylene flow rate, 300–3000 nl/hr. The molecular weight of polymer formed was shown to decrease with increasing reaction temperature and to increase with increasing pressure. When the ethylene flow rate increases, the molecular weight decreases in the polymerization at 30–60°C, but it does not change in the polymerization at 75–90°C. Methyl group content, which is a measure of short‐chain branching of the polymer, increases with increasing reaction temperature, i.e., ca. 1 CH3/1000 CH2 at 30°C and ca. 9 CH3/1000 CH2 at 90°C. Methyl content is independent of the ethylene flow rate. The changes in the melt index of polymer with reaction conditions corresponds to the change of the molecular weight. The density, crystallinity, and melting point of polymer decrease with the reaction temperature as the short‐chain branching increases, and they are almost independent of ethylene flow rate and pressure.
Some remarks on the cationic polymerization of caprolactam
Authors: Stea G. , Gechele G. B. , Mariani L. , Manescalchi F. 
Published: April 2003

AbstractThe cationic polymerization of caprolactam under anhydrous conditions above the polymer melting point with caprolactam hydrochloride as initiator is examined. Analytical and polymerization results under different conditions and with the addition of several substances are compared with the existing theories and discussed.
MIR spectroscopy: A new method for studying the hydrolysis of hexamethylcyclotrisilazane in air
Authors: Hermann T. S. , Leng L. J. 
Published: April 2003

AbstractA new method for studying the rate of hydrolysis of hexamethylcyclotrisilazane has been developed. This method, MIR spectroscopy in the infrared region of 4000–625 cm−1, was employed to characterize the reactions. The change in relative intensity of characteristic bands of the reactant is plotted as a function of time to give the required rate curves. The effects of temperature, pressure, exterior magnetic fields, and ultraviolet–visible radiation on the rate curves are also discussed.
Photo‐oxidation of phenoxy resin
Authors: Kelleher P. G. , Gesner B. D. 
Published: April 2003

AbstractA study has been made of the photolysis and photo‐oxidation of phenoxy resin. Photolysis results in the evolution of hydrogen, methane, ethane, propene, propane, toluene, and the oxides of carbon. Also observed are increased yellowing, a rapid rise in gel content, and a decrease in intrinsic viscosity and elongation. Photo‐oxidation causes similar changes, but produces oxidized chain fragments, more gel, and less yellowing as well as broad absorptions in the hydroxyl and carbonyl regions of the infrared spectrum. A free‐radical mechanism is proposed in which both chain scission and crosslinking occur.
Changes in molecular weight during autoxidation of atactic polypropylene in solution
Authors: Reich Leo , Stivala S. S. 
Published: April 2003

AbstractThe authors had previously reported a general scheme with corresponding kinetic expressions for the uncatalyzed thermal autoxidation of polyolefins, such as atactic polybutene‐1 (APB), in the bulk phase. Recently, Bawn and Chaudhri reported that similar kinetic expressions and scheme were also applicable to autoxidation of atactic polypropylene (APP) in solution. These workers did not attempt to correlate their results for the effect of oxidation on the molecular weight of APP as evidenced by intrinsic viscosity. In this paper, we have applied expressions, previously reported for changes in intrinsic viscosity as a function of time during the autoxidation of APB in the bulk phase, to the data provided by Bawn and Chaudhri for the autoxidation of APP in solution. The quantitative evidence obtained indicates that the intrinsic viscosity relationships which were found to be valid for the autoxidation of APB in the bulk phase are also valid for the autoxidation of APP in solution (at polymer concentrations of ca. 1.5M and above).
The continuum interpretation for fracture and adhesion
Authors: Williams M. L. 
Published: April 2003

AbstractFrom the viewpoint of continuum mechanics, and particularly the energy concept of fracture, adhesive and cohesive failures are similar. The essential difference involves the interpretation of the energy required to create new (adhesive or cohesive) surface area. A simple pressurized disk test is described for measuring the adhesive value for a bonded elastomer, and an application to a debonding problem in engineering design is given.