bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface tensions of liquid polyisobutylenes
Authors: Edwards H.
Published: April 2003

Measurements 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

The 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

An 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

The 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

A 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

The 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

The 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

A 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

Acetic 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

β‐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

The 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

The 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

The 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

The 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.
Effect of amines in anionic polymerization of caprolactam
Authors: Stea Gianni , Gechele Giovanbattista , Arena Carlo
Published: April 2003

The effect of various amines in anionic polymerization of caprolactam has been investigated. Experiments have been carried out below the polymer melting point. The results are discussed and explained on the basis of imide–amine interaction.
Some remarks on the cationic polymerization of caprolactam
Authors: Stea G. , Gechele G. B. , Mariani L. , Manescalchi F.
Published: April 2003

The 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

A 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

A 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

The 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

From 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.
Reactions of halogenated 1,2‐epoxypropanes and diethylaminoethyl cotton
Authors: Soignet Donald M. , Benerito Ruth R.
Published: April 2003

Diethylaminoethyl (DEAE)‐cotton has been reacted with epichlorohydrin (1,2‐epoxy‐3‐chloropropane) neat, in alcoholic solvents, and in aprotic solvents at temperatures ranging from 25 to 95°C. Fabric properties and electron micrographs of fibers removed from these chemically treated DEAE cottons have been compared with those obtained when DEAE‐cottons were treated under similar conditions with other halogenated 1,2‐epoxypropanes, and with 1,2‐epoxy‐4,4,4‐trichlorobutane. For comparative purposes, epichlorohydrin was reacted with an aminized cotton containing primary amine groups, with cotton containing quarternary ammonium groups, and with DEAE‐cottons in which the tertiary amine groups had been quaternized. For reaction at 95°C with net epichlorohydrin, greatest increase in conditioned wrinkle recovery was observed with DEAE‐cottons. Only with DEAE‐cottons were the add‐ons and recovery angles imparted by epichlorohydrin affected by the anion associated with the amine groups. None of the halogenated 1,2‐epoxypropanes reacted with unmodified cotton in the absence of a basic catalyst. Those that reacted with unmodified cotton in the presence of an external base catalyst did not improve conditioned recovery angles. The mono‐, di‐, and trichloro‐1,2‐epoxypropanes all increased the conditioned and wet wrinkle recovery of DEAE‐cotton when reacted neat at 95°C. The type of oxirane ring opening of epoxypropanes was shown to be influenced by the degree of chlorination of the carbon alpha to the ring. Both primary amine groups and quaternary amine groups catalyzed the epichlorohydrin–cellulose reaction. Dilution of epichlorohydrin with alcohols or decreasing reaction temperature lowered add‐ons and improvements in wrinkle recovery properties. Use of aprotic solvents for the DEAE‐cotton‐epichlorohydrin reaction gave finished cotton fabrics having only high wet wrinkle recovery properties.
Diethylaminoethyl cellulose–anhydride reactions
Authors: Soignet Donald M. , Benerito Ruth R. , Pilkington Mary W.
Published: April 2003

Tertiary amine groups of diethylaminoethyl cotton are internal catalysts for the reaction of cellulose hydroxyls with anhydrides to form esters. These cellulose esters are stable to mild acid steeping but hydrolyze under mild basic conditions. Anhydrides containing halogen atoms yield products with increased resistance to rot. None of the anhydrides employed produced fabrics with increased crease recovery, abrasion resistance, or breaking strength.
Substituted aliphatic polybenzimidazoles as membrane separator materials
Authors: Trischler Floyd D. , Levine Harold H.
Published: April 2003

When initially evaluated as potential membrance separators for a heat‐sterilizable silver‐zinc battery, aliphatic polybenzimidazoles (PBI) proved to be unsatisfactory because of their excessively high resistivity. Later, various polymer modifications such as sulfonation, N‐hydroxyethylation, N‐cyanoethylation, and N‐carboxyethylation were made in an attempt to increase the hydrophilicity of the PBI's. As a result of these efforts, an N‐carboxyethylated, suberic acid‐based PBI shows promise as a sterilizable battery separator material.
Copolymers of starch and polyacrylonitrile: The dilution effect
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E.
Published: April 2003

In the ceric ammonium nitrate‐initiated graft polymerization of acrylonitrile (AN) with starch, grafting frequencies and molecular weights of grafted polyacrylonitrile changed from 600 anhydroglucose units (AGU)/graft and 120000 to 280 AGU/graft and 36000 when concentrations of starch and AN were varied from 0.27 and 1.20 to 0.023 and 0.235 moles/l. of water, respectively. The influence of variety of starch, size of the starch granules, and reaction time was studied, and possible reasons for the influence of reactant concentration on the composition of the copolymer are considered.
Telechelic elastomers
Authors: Uraneck C. A. , Hsieh H. L. , Sonnenfeld R. J.
Published: April 2003

Telechelic elastomers, polymers with reactive terminal groups, can be prepared in emulsion and solution systems. Examples of characterization of the polymers and preparation of a mercapto telechelic copolymer in an emulsion system and of mercapto‐, hydroxy‐, and aziridinyl‐telechelic elastomers in solution systems are given. The elastomers were cured in peroxide or sulfur‐accelerator formulations. The telechelic polymers exhibited enhanced stress‐strain and dynamic properties in comparision to those of the controls. In tread formulations, outstanding properties were obtained for the mercapto‐and azieridinyl‐telechelic butadiene‐styrene copolymers.
Performance of solution‐cast membranes of poly(hydroxythyl methacrylate) in osmosis and reverse osmosis
Authors: Bloch R. , Vieth W. R.
Published: April 2003

Noncrosslinked copolymers of hydroxyethyl methacrylate (HEMA) with ethyl methacrylate (EMA) were prepared and investigated as candidate materials for reverse osmosis membranes. Water and salt flux were calculated from the results of osmosis experiments, compared with cellulose acetate and found to be somewhat smaller. The mobility of water varies by several orders of magnitude between a high flux cellulose acetate membrane and a low flux HEMA‐EMA membrane.
Comparaison des méthodes de fractionnement par chromatographie de perméation et par gradient d'elution pour la détermination des répartitions moléculaires des polypropylénes
Authors: Crouzet P. , Fine F. , Mangin P.
Published: April 2003

Molecular weight distributions for polypropylene samples have been determined by a permeation fractionation method (GPC). Porous silica beads were used as a packing material for the columns. The set of columns allows a good separation of the polypropylene macromolecular chains in a range of molecular weights from 5000 to 1.5 × 106, and the thermal and mechanical stabilities of these beads are very good. The calibration has been carried out with fractions of polypropylene of narrow molecular weight distribution prepared by a large‐scale column fractionation. The molecular weights M̄w and M̄n and the ratios M̄w/M̄n calculated from the GPC curves show, in general, good agreement with the ones calculated from the column fractionation curves. However, the M̄w/M̄n ratios are always highter in the case of GPC fractionation. This could be due to diffusion phenomena.
Storage‐stable epoxy B‐stage resins
Authors: Aelony David
Published: April 2003

N‐Substituted β‐aminopropionhydrazides, RNHC2h4CONHNH2, were prepared by the Michael addition of primary amines to acrylic esters. The adducts were converted to the corresponding hydrazides. The aminohydrazides react readily with terminal epoxides at moderate temperatures yeilding B‐stage resins of excellent storage stability. When powdered B‐stage resins are sprayed on hot metal (150‐230°C.), a smooth cross‐linked coating is formed in less than 3 min. The coatings have unusually high elasticity, they pass the Olson button test. For best performance the amine used should have the primary amino group attached to either a primary carbon atom or directly to an aromatic nucleus. Aminohydrazides with the following R. Groups have been prepared: methyl, n‐butyl, sec‐butyl, tert‐butyl, phenyl, cyclohexyl, benzyl, octyl, dodecyl, and octadecyl.
Reversible melt flow rate increase of branched acetal polymers
Authors: Prichard J. H. , Wissbrun K. F.
Published: April 2003

Continued shearing of molten long‐chain branched acetal polymers raises their melt flow rates manyfold. The increase is not due to molecular degradation, as evidenced by constancy of inherent viscosity, and by the ability to reverse the increase by dissolving and reprecipitating the polymer. Shearing was found to have only a relatively small effect upon the melt viscosity but a very large effect upon the entrance correction for capillary flow. It is suggested that crystallization of branched polymers from solution creates an exceptionally strong entanglement network, and that the observed rheological changes reflect the disruption by shear of this network.
Oxygen consumption during induction period of a photopolymerizing system
Authors: Chong J. S.
Published: April 2003

Based on a simple, general kinetic scheme for the inhibition reaction of a photopoly‐merizing system, a solution is obtained for the differential equation which describes the oxygen concentration profile as a function of exposure time, light intensity, and absorption coefficient. The effect of the absorption coefficient on the oxygen concentration in a polymer slab is evaluated by numerical computation.
Decomposition of burning polytetrafluoroethylene
Authors: Fenimore C. P. , Jones G. W.
Published: April 2003

PTFE rods, 0.6–3.8 cm diameter, were burnt from the top downwards in a gently rising atmosphere of oxygen. The burning was only possible in concentrated oxygen, or at elevated temperature or pressure. At its surface temperature of 920 ± 25°K, the polymer evolved monomeric C2F4 which oxidized in a surrounding gas flame; 15–35% of all the carbon in the gas was found present as monomer just above the larger rods. Depolymerization of the solid was not its only mode of decomposition, however. The heat radiated and conducted from the flame into the condensed phase was too little to depolymerize it completely, and heterogeneous reactions with species from the gas phase must also have contributed to the decomposition. Overall, the polymer burnt in O2, but the gaseous reactant which attacked the surface need not have been O2 or O in all cases, for these rare species just above the larger rods. Elemental fluorine was present in the gas even when elemental oxygen was absent, and calculations indicate that F atoms would be a major flame species at equilibrium. It is possible that heterogeneous attack by flame generated F atoms consumed part of the polymer and also supplied energy to help depolymerize the rest.
Chemistry of epoxide resins. XVII. Influence of structure and curing conditions on the density, degree of cure, and glass transition temperature during the curing of epoxide resins
Authors: Fisch W. , Hofmann W. , Schmid R.
Published: April 2003

During an investigation of various epoxide resin systems, some cases were found in which the room temperature density decreased with increasing curing temperature and increasing degree of cure. In other systems the density was found to be independent of the curing temperature. In these cases it is possible by deliberately stopping the reaction to measure density values which also decrease as the curing progresses. This unexpected behavior can be explained in a purely physical manner from the pattern of the density changes during an entire curing cycle. The density decrease of the noncured mixture, which is due to the increased curing temperature, outweighs all contraction effects consisting of isothermal chemical and cooling shrinkage, whereby the latter is dependent to a great extent on the glass temperature. In those cases where the glass temperature exceeds the curing temperature, the chemical reactions come to a standstill, when the temperature difference reaches a certain value, i.e. it “freezes chemically”. By means of values that can be measured readily at low temperatures, it is possible to construct diagrams from which the variation of the density at higher temperatures of the curing cycle can be estimated.
Studies in chemically modified celluloses. I. Oxidative susceptibility of chemically, modified cellulose
Authors: Kangle P. J. , Nabar G. M.
Published: April 2003

The oxidative susceptibility to different oxidizing agents such as dichromate–sulfuric acid, dichromate–oxalic acid and sodium hypochlorite in presence of leuco Cibanone Orange R of cellulose oxidized with sodium metaperiodate and its corresponding borohydride‐reduced product was studied and compared with that of cellulose. From the changes in the chemical properties of the oxidixed products, an attempt was made to study the mechanism of oxidation of periodate oxycellulose and sodium borohydride‐reduced periodate oxycellulose with the above mentioned oxidizing agents.
Mounting media for the microscopical examination of rubber‐reinforced polymers
Authors: Hannah Ray E. , Bond Robert H.
Published: April 2003

Mounting media for examining rubber reinforced copolymers using the phase microscope are described. The mounting media are based on cinnamaldehyde as the basic solvent with suitable adjustments made depending upon the copolymer under examination.
Practical use of intrinsic viscosity for polyethylenes
Authors: Quackenbos H. M.
Published: April 2003

Although usually derived from measurements at several concentrations, intrinsic viscosity (IV) can be determined with good precision from a single measurement. IV tends to be a regular and distinct function of melt index (MI) for each family of high‐density polyethylenes. The tendency to regularity suggests a use in routine control, uniform production being marked by a small scatter about the IV–MI line. The distinctiveness marks one family of medium high and high‐density resins from another, and becomes a rapid means of identifying the production method of a resin. Further, IV at a given MI correlates roughly with properties, and can be used to characterize a resin. These attributes of the IV–MI relationship arise from the correlation of IV a t a given MI with width of molecular weight distribution. Such width varies considerably among commercial high‐density polyethylenes, causing a commensurate variation in IV. Among low‐density polyethylenes the IV–MI relationships is less useful, being confused by long‐chain branching.
Methods of fractionating polymers by ultrafiltration
Authors: Baker R. W.
Published: April 2003

Polyvinylpyrrolidone and dextran polysaccharides have been fractionated by ultrafiltration by using newly developed membranes with sharp molecular weight cutoffs. Three different experimental techniques were employed: (a) batch ultrafiltration by using progressively more retentive membranes; (b) continuous ultrafiltration by using several similar membranes in series; (c) variable pressure ultrafiltration by using a single membrane and varying the applied pressure. Ultrafiltration is shown to be a technique of preparative fraction having the advantages of simplicity, speed, and economy.
Thermal degradation of phenolic resins. V
Authors: Learmonth G. S. , Searle D. P.
Published: April 2003

The effect of varying the nature of crosslinks in phenolic resins has bee studied with the use of resins made from phenol, p‐cresol, and bisphenol A. Thermal analysis showed that the methylene bridge was stronger under nonoxidative conditions than the isopropylidene linkage. The result is somewhat affected by the degree of crosslinking.
Failure loci for a thermoplastic at various temperatures
Authors: Golden J. H. , Hammant B. L. , Hazell E. A.
Published: April 2003

Corresponding flexural stress and strain data for polycarbonate failure (at yield or break when brittle), at various temperatures are reported. It is shown that a specific failure locus is obtained at each temperature examined and that the results provide a means of construction of an appropriate locus for any temperature within the range 77–373°K investigated.
Analysis of condensation polymerization reactors. II. Batch reactors
Authors: Szabo T. T. , Leathrum J. F.
Published: April 2003

The kinetic model for polycondensation reactions was developed in Part I of this work. This kinetic model is now to be utilized as a framework for the analysis of batch experiments.
Tetrabromophthalic anhydride in self‐extinguishing polyesters
Authors: Narkis M. , Grill M. , Leeser G.
Published: April 2003

Polyesters based on tetrabromophthalic anhydride are self‐extinguishing in the range of 8–12% bromine content and nonburning at higher levels of the latter. An increase in bromine content results in higher flexural and tensile strenght and flexural modulus, while impact resistance is slightly reduced. Mechanical Properties vary with bromine content in the 0–12% range and remain practically unaffected at higher levels up to 23%.
Diffusion of m‐nitroaniline into polyacylonitrile
Authors: Hossain Talukder Mohamed Abul , Iijima Toshiro , Morita Zenzo , Maeda Hirokuni
Published: April 2003

The diffusion of nonionic penetrant, m‐nitroaniline, into polyacrylonitrile was studied in detail on a range of temperature from 50.6°C to 95.0°C. The penetrant distribution in polymer is Fickian, which is different from that of cationic dye, Malachite Green reported earlier. The diffusion coefficient D increases with the rise of temperature. The sharp inflection point (72°C) of the Arrhenius plot, log D versus 1/T, corresponds to Tg of polyacrylonitrile in the presence of water, which is lower than that measured in the dry state by a dynamic mechanical testing method. The activation energy is constant below Tg (ca. 10 kcal/mole), suddenly reaches a maximum at Tg and then gradually decreases with increasing temperature. General trends of Arrhenius plot for different polymer–penetrant systems are discussed. The temperature dependence of penetrant diffusion above Tg can be described by a general form of the WLF equation, log aT = log (DTg/DT) = − C1g(T − Tg)/(C2g + T − Tg), where the values of C1g and C2g were calculated to be 4.03 and 24.54, respectively. A comparison was made between m‐nitroaniline and Malachite Green. The difference in the respective Tg and the constants C1g and C2g of the WLF equation in polyacrylonitrile is attributed to the size of the penetrants and their ionic character. The surface concentration increases below Tg and decreases above Tg with rise in temperature.
Analysis of condensation polymerization reactors. III. Continuous reactors
Authors: Szabo T. T. , Leathrum J. F.
Published: April 2003

The kinetic model for polycondensation reactions has been derived and techniques for validating the model have been described in Parts I and II of this work. This paper is concerned with using the results of Part I and II for the analysis and design of continuous polycondensation reactors.
Structure–property relationships for liquid transport in modified polypropylene membranes
Authors: Michaels Alan S. , Vieth Wolf , Hoffman Allan S. , Alcalay Haim A.
Published: April 2003

In view of the intensifying interest in the application of polymeric membranes in mixture separation processes, the permeation and permselective properties of polypropylene films toward several candidate organic liquids and vapors were investigated. Polymer films were subjected to solvent and thermal treatments, and the effects of these treatments on film morphology and transport properties were studied. Structure–property relationships for membrane permeation were then developed. Polypropylene films were found to be selective toward toluene, relative to isooctane, and p‐xylene relative to o‐xylene. Liquid flux rates were found to depend primarily upon the solubility of the permeants in the films and the absolute difference in the solubility parameters of the polymer–liquid pair provided a good basis for correlation of this effect. Considering liquids of closely similar solubility parameters, fluxes were found to be dependent upon the apparent molecular cross sections of the permeants. Films annealed in various organic solvents at temperatures of 60–100°C exhibited enhanced permeability, with up to fifteenfold increase relative to untreated membranes, but with reduced selectivity towards the permeants. A mechanism to account for these effects through consideration of the influence of treating solvent type on polymer morphology is proposed. It postulates the formation of more open or coarser spherulitic structures as a result of recrystallization in the presence of solvent during annealing. The enhanced flux rates in the treated films are attributed to the changes in the spherulite textures and to diminished intercrystalline tie chain constrainment within the spherulitic substructure.
Effect of molecular weight on changes produced in the surface layer of polystyrene film in a nitrogen atmosphere by ultraviolet irradiation
Authors: Kato Koichiro
Published: April 2003

The effect of molecular weight on the changes in the surface layer of polystyrene films on near‐ultraviolet irradiation has been studied in a nitrogen atmosphere at 25°C. Changes produced by irradiation were followed by determining the amount of solvent‐insoluble portions, the molecular weight changes, and the intrinsic viscosity changes. Most crosslinking took place in the range of the transmissible depth of 2537 Å light. Low molecular weight samples formed a small amount of solvent‐insoluble material. High molecular weight samples formed a large amount of solvent‐insoluble material. In the range above a certain molecular weight, the amount of solvent‐insoluble material approached an asymptotic value with increasing molecular weight, because of the limited penetration of 2537 Å light. Since most crosslinking took place in the range of the transmissible depth of 2537 Å light, the average number of crosslinks in the solvent‐soluble portions was influenced by the amount of solvent‐insoluble material. Low molecular weight samples produced many crosslinks. High molecular weight samples produced a few crosslinks. In the range above a certain molecular weight, the average number of crosslinks in the solvent soluble portions approached an asymptote with increasing molecular weight. Chain scission seems to have occurred in every sample.
Preparation of block copolymers of styrene and methacrylic acid
Authors: Brown C. W. , Taylor G. A.
Published: April 2003

A range of block copolymers of styrene and methacrylic acid has been prepared by the suspension method involving migration of a growing radical across a phase boundary. The way in which copolymer composition varies with change in the amount of the two monomers in the reaction mixture has been studied, and explanations are suggested to account for these variations. Two methods, involving calculation from solubility data and thermogravimetric analysis respectively, have been used to give an estimate of the length and composition of the blocks.
Visible dichroism of the poly(ethylene terephthalate)–disperse dye system at high temperatures
Authors: Nakayama Kazuo , Okajima Saburo , Kobayashi Yasuji
Published: April 2003

The dichroic behavior of PET film dyed at 70°C with Disperse Red 17 or Disperse Yellow 7 was investigated in the temperature range 20–200°C with a view to studying the changes in amorphous region of PET at high temperatures. The dichroic orientation factor D versus temperature plot is expressed by a straight line with negative slope; two breaks appear at 80 (Tg) and 120°C. So long as the amorphous structure does not change irreversibly, the values of D change reversibly with the temperature. Hence, if a change in D after heating is observed at room temperature, it is evidence that an irreversible change occurred in the amorphous structure during the heating. The break at 120°C is a new amorphous transition point of PET existing along with Tg, although the Tg can hardly be observed after the cold crystallization; some phenomena reported in the literature are proposed as evidence.
Permeation of gases through modified polymer films. I. Polyethylene–styrene graft copolymers
Authors: Huang R. Y. M. , Kanitz P. J. F.
Published: April 2003

The permeabilities of nitrogen, oxygen, and carbon dioxide through polyethylene–styrene graft copolymer films were measured by means of a gas permeability apparatus based on a modification of Barrer's high vacuum technique. Polyethylene–styrene grafts were prepared by mutual γ‐ray irradiation of low‐density polyethylene films in styrene–methanol solution. Densities and thicknesses of the graft copolymer films were determined. It was observed that the gas permeability constants decreased with increasing grafting to minimum values at 20–30% styrene grafting and increased again above 30% grafting. These results are explained in terms of a decrease in the free volume of the amorphous regions of the polyethylene by a “filling in” effect of the grafted polystyrene chains. Above 30% grafting, disruption of the crystallites may occur resulting in increased gas permeation. Activation energies for gas permeation through polyethylene–styrene graft copolymer films were calculated and found to decrease with increasing per cent styrene grafting. For nitrogen permeation, the activation energy decreased from 11.7 kcal/mole for unirradiated polyethylene to 9.5 kcal/mole for a 50.5% graft. Corresponding values for oxygen and carbon dioxide were 10.2–8.2 kcal/mole for a 48.7% graft and 8.4–6.5 kcal/mole for a 50.5% graft.
Transport properties and their correlation with the morphology of thermally conditioned polypropylene
Authors: Vieth Wolf , Wuerth Walter F.
Published: April 2003

Time‐lag and static sorption experiments were employed to measure permeability, diffusivity and solubility constants of He, A, and CF4 in polypropylene films cooled at various rates from the melt and subsequently annealed at varying temperatures near the melting point. While solubility constants in films annealed above 90°C showed the normal variation with the amorphous content of the polymer, solubility constants for all unannealed, quenched films were remarkably constant and independent of the rate of cooling. In fact, all quenched films appeared to have the same amorphous content (ca. 41%). The remaining material is believed to be a mixture of monoclinic and hexagonal crystallinity, the volume ratio of the two being a function of the rate of quenching, and changing on annealing, in favor of the more stable, monoclinic form; the transition occurring rather sharply at 90°C. X‐ray diffraction provided supporting evidence for the presence of the hexagonal crystals. The diffusion behavior in crystalline polypropylene is normal and Fickian but instead of the usual decline with increasing crystallinity, diffusivities showed definite enhancement in the case of the annealed films, i.e., the expected monotonic decline of D with increasing crystallinity is not observed. This behavior is attributed to a reduction in diffusional impedance through formation of defects in existing crystallites, as the lamellae thicken, in a manner similar to that observed on annealing of polyethylene single crystals. The apparent activation energies of diffusion were essentially constant and independent of thermal history. This suggests that in a highly crystalline polymer diffusion is not so much impeded by the restricted mobility of chain segments but rather by the extremely small dimensions of the available diffusive pathways. In support of the argument that the transport properties of polypropylene are controlled at a level of microstructure well below the characteristic dimensions of spherulities, it was observed that bulk‐crystallized polypropylene has a spherulitic structure whose size and texture do not change significantly on annealing.
Some rheological properties of water‐soluble hydroxypropylcellulose
Authors: Elliott John H.
Published: April 2003

Water‐soluble hydroxypropylcellulose having a hydroxypropyl molecular substitution (MS) of approximately 4.0 is a thermoplastic which may be fabricated in conventional plastic‐forming equipment. Its high‐temperature rheological properties have been measured over a wide range of temperatures, shear rates, frequencies, and diluent concentrations, by using the Weissenberg rheogoniometer. The rheological behavior of such hydroxypropylcelluloses is quite different from that of a nonpolar thermoplastic. This behavior may be interpreted in terms of two types of supermolecular structure: a crystalline phase which persists up to at least 215°C (as established by x‐ray examination), which is dispersed in an amorphous but highly hydrogen bonded matrix of stiff molecules.
Polymer rheology: Influence of molecular weight and polydispersity
Authors: Cross Malcolm M.
Published: April 2003

Literature data on the non‐Newtonian flow of bulk polymer and of polymer solutions are correlated on the basis of a four‐parameter equation, η = η∞ + (η0 − η∞)/[1 + (τD)m], η being the viscosity at shear rate D, and η0 and η∞ limiting values at D = 0 and D = ∞, respectively. The parameters η0, η∞, and τ all show dependence on molecular weight, and in general there is good correlation between τ and η0. There is evidence that τ is related to a molecular weight higher than the weight‐average. The exponent m shows dependence on molecular weight distribution and approaches an upper limit of unity for a monodisperse linear polymer. For linear unblended polymers it may be expressed empirically by m = (M̄n/M̄w)1/5.
Effect of mastication on molecular weight and molecular weight distribution of EPDM polymer and SBR
Authors: Baranwal Krishna , Jacobs Howard L.
Published: April 2003

EPDM and SBR were masticated on an open mill. The temperature range of mastication for EPDM was 68–480°F. SBR was milled at 170–200°F. The gel‐permeation chromatography analyses were made on the masticated samples. For EPDM at 68°F, molecular weight decreases and molecular weight distribution narrows with mastication time; the degradation process is nonrandom. At constant mastication time between 182 and 315°F, there is little change in molecular weight. Mastication for 18 min at 480°F broadens the molecular weight distribution; the degradation is random. For SBR at 170–200°F, molecular weight decreases and molecular weight distribution narrows with mastication time; the degradation process is also nonrandom. Nonrandom degradation for both EPDM and SBR results in a narrowing of the molecular weight distribution, without build‐up of low molecular weight molecules, and without a shift in the peak molecular weight. This is contrary to nonrandom degradation of natural rubber where a shift in the peak molecular weight occurs with mastication time.
Strain magnification in polymer composites
Authors: Ziegel K. D. , Frensdorff H. K. , Fogiel A. W.
Published: April 2003

We consider two approaches to strain magnification in a composite material, point out that they apply to different situations, and caution against misapplication of the equations derived.
Prediction of polymer densities
Authors: Van Krevelen D. W. , Hoftyzer P. J.
Published: April 2003

A method is proposed for predicting the density of a linear, amorphous polymer. The method is based on the additivity of group increments for the molar volume of a polymer unit. It is analogous to the published methods for predicting the molar volume of organic liquids. The method may be improved as additional experimental values on polymer densities become available.