bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxyluminescence of polymers. II. Effect of temperature and antioxidants
Authors: Schard M. P. , Russell C. A.
Published: April 2003

The oxyluminescence of polypropylene and polyethylene stabilized with various amounts of 4,4′‐thiobis(3‐methyl‐6‐tert‐butylphenol) were studied and compared with oxygen uptake data. It was found that there was a correlation, although not linear, between the two methods. In the case of the stabilized polypropylenes, a pronounced aging effect was noticed. The oxyluminescent behavior of stabilized polyethylene was somewhat different from that of stabilized polypropylene. The temperature coefficients of the oxyluminescence of polypropylene, polyethylene, nylon 6, polystyrene, polyurethane and polymethyl methacrylate were obtained. From these data the apparent activation energies for the light‐emitting reaction were calculated. For the olefin polymers, these values are close to the activation energies of the oxidative degradation reaction obtained by other means. Both polyethylene and polymethyl methacrylate have different activation energies below their transition points as compared to higher temperature, indicating a different mode of reaction in the solid state from that occurring in the melt. An interesting transition luminescence, which was more pronounced in the absence of oxygen, was observed in the case of polyethylene.
Some thermal studies on poly(ethylene terephthalate)
Authors: Hughes M. A. , Sheldon R. P.
Published: April 2003

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) of poly(ethylene terephthalate) has been carried out on samples of amorphous, cold‐drawn, heat‐crystallized, and acetone‐crystallized polymer. From DTA it appears that for amorphous material a prolonged “secondary” crystallization process follows a primary process in the region of 140°C. For cold‐drawn polymer, heat treatment does not reflect differences observed in previous x‐ray diffraction studies. The TGA gives evidence that a high temperature endothermic peak observed in DTA may not be directly associated with depolymerization. With acetone‐crystallized material a high degree of acetone retention is detected.
Thermal decomposition of polysulfones
Authors: Wellisch Eric , Gipstein Edward , Sweeting Orville J.
Published: April 2003

The thermal decomposition of the C4, C6, and C8 polymethylene sulfones has been investigated at 275°C. under reduced pressure. The gaseous decomposition products, collected and identified by infrared and mass‐spectrometer analysis, were found to consist primarily of sulfur dioxide, olefins, alkanes, water, and hydrogen. A mechanism is proposed in which the rate‐determining step consists of a concerted attack of the sulfone group on the β‐hydrogen atom with elimination resulting in α‐olefins and a sulfinic acid. The sulfinic acid rapidly decomposes to give sulfur dioxide, hydrogen, and alkyl free radicals. The final products are formed by transfer and termination reactions of the free radicals and isomerization of the olefins in the presence of sulfur dioxide. Experimental evidence confirming this mechanism consists of rate studies of polymer decomposition whose initiation was found to be independent of polymer purity and of added free‐radical initiators. A further proof of the rate‐determining step was obtained by comparison of the decomposition products of bis‐1,4‐(butanesulfonyl)butane with those of structurally comparable sulfinic acids: 1,4‐butanedisulfinic acid and 1‐butanesulfinic acid.
Effect of surface tension in the measurement of the average normal stress at the exit of a capillary tube through an analysis of the capillary jet
Authors: Slattery John C. , Schowalter W. R.
Published: April 2003

The analysis of a stationary, rotationally symmetric liquid jet which leads to an expression for the average normal stress at the exit of a capillary tube is reexamined with particular attention to the effect of surface tension. The limiting case of a nearly cylindrical jet is compared with the analysis presented by Gavis and Middleman.
Factors affecting the promoted aggregation and coalescence of synthetic rubber particles
Authors: White W. W. , Reynolds J. A. , Gilbert R. D.
Published: April 2003

Small particles (ca. 700 A.) in an SB‐R latex can be agglomerated (aggregation and coalescence) to the large size and heterogeneous distribution required for fluid high solids latex. This agglomeration is promoted by high molecular weight materials such as polyvinyl methyl ether (PVM). The mechanism of this agglomeration has been investigated. The effects of controlled variations in the amounts of PVM, electrolyte, soap and latex solids content were determined using statistically designed experiments. The agglomeration was found to differ from Smoluchowski kinetics in that it could best be described by the relationship: (1/n) = (1/n0) + at − bt2 where n = particle number, t = time and a and b are constants. The agglomeration rates were about 1011 to 1012 times slower than the theoretical Smoluchowski rapid coagulation rate. Increases in PVM, soap, and latex solids increased the agglomeration rate. The agglomerations were self‐limiting and reached equilibria the level of which increased with increases in PVM and decreased with increases in soap. Regression equations relating the effects of the controlled variables on the agglomeration rate and the equilibria states are derived and presented graphically. The particle size distribution of the final latex was significantly correlated, with that expected from theoretical collision theory.
Effect of the concentration of phenyldichlorophosphine and reaction time on the intrinsic viscosity of copolymers of methyl methacrylate with phenyldichlorophosphine
Authors: Łaszkiewicz Bogumił
Published: April 2003

The relation between the intrinsic viscosity of methyl methacrylate–phenyldichlorophosphine copolymers and the copolymerization time were investigated. The copolymers of methyl methacrylate and phenyldichlorophosphine were prepared at mole ratios of 1:10.012, 1:0.026, and 1:0.062, respectively. The experiments indicate that the intrinsic viscosity of copolymers increases at the first stage of copolymerization and then decreases after reaching a maximum. These changes of the intrinsic viscosity can be explained by degradation and by small relative activity of organophosphorus comonomers.
Physicochemical studies of cellulose acetate decomposition reactions
Authors: Parks L. R. , Sperling L. H.
Published: April 2003

This work is a continuation in these laboratories of the study of the source of undesirable optical properties of molded cellulose acetate. The origin, mechanism of formation, and structure of the colored compounds formed upon heating cellulose acetate in the presence of plasticizer were studied. Extraction of heated mixtures gave evidence indicating the colored compounds are intermediates containing a conjugated carbonyl group. Efforts to fractionate and isolate color‐causing fractions were defeated by the well‐known solvent inclusion difficulties and upset of the little‐understood salt balance in the sample. The effects of additives known to degrade cellulose acetate were determined by heating mixtures of these materials with cellulose acetate dissolved in excess plasticizer. Acidic compounds caused the expected severe degradation and color formation. Air oxidation and free radical initiators had very little effect compared to the acidic materials. Inhibitors of the action of acidic compounds (neutralizers) and of oxidative degradation were studied.
Dielectric properties of an epoxy resin
Authors: Dasgupta S. , Mital P. K.
Published: April 2003

The dielectric properties of an unmodified epoxy resin with a wide range of hardener content were investigated over the frequency range 5 cycles/sec. to 50 Mcycles/sec and over the temperature range 12–95°C. In the frequency region below 1 Kcycle/sec., the loss is predominently high both in the pure resin and the pure hardener and, interestingly, is very much reduced when the two are mixed to obtain a plasticized product; the loss is at a minimum when the percentage of epoxy is about 10 and increases appreciable on both sides of the figure. At frequencies above 1 Kcycle/sec., a relaxation type loss is obtained in the hardener and the plasticized samples; pure resin again shows a predominently high loss, the maximum for it at room temperature being above 100 Mcycles/sec.
Caractérisation de structures de fibres de cellulose régénérée par l'étude détaillée de leurs diagrammes de diffraction de rayons X et par divers traitements de gonflement. I. Étude détaillée des diagrammes de diffraction de rayons X de fibres et de feuilles d'hydrate de cellulose
Authors: Lefébvre S. G. , Ludé A. C. , Larticle M.
Published: April 2003

The authors have designed different experimental devices for the realization of strictly monochromatic diagrams of orientated samples, the fully automatic recording of numerous radial tracings thereof, and the careful analysis of their components. Because of the difficulty of interpretation of high tenacity rayons diagrams (due to poor resolution of peaks and the occurrence of cellulose IV) preliminary experiments have been carried out, with (a) particular examination of rayons containing no cellulose IV, (b) application of moderate swelling treatments causing a sharpening of diffraction peaks, (c) x‐ray examination of planar‐oriented cellulose samples giving “simplified” diagrams when irradiated under particular conditions. The information obtained from these experiments establishes the occurrence of a noncrystalline anisotropic part in regenerated cellulose fibers. There is a twofold orientation of the “amorphous” background in regenerated cellulose sheets. This is in favor of the occurrence of doubly anisotropic “pseudo‐amorphous” parts whose structure is of a paracrystalline type with superimposed dislocations. On the basis of different observations made on photometric tracings, a nonsubjective method is suggested for the individual evaluation of A0, A3 + A4 of cellulose II, (002) and (101 + 101) of cellulose IV, pseudo‐amorphous and amorphous components in regenerated cellulose diagrams. Individual orientation factors may be defined and measured for the components.
Some observations on the melting behavior of textile fibers. Part I. Core melting during hot‐stretching of nylon
Authors: Farrow B. , Simmens S. C.
Published: April 2003

It has been found that under certain conditions of heating, filaments of nylong melt from the center outwards. It has been established that this is associated with the presence of moisture in the filaments and that moisture lowers the melting point of the material. Well‐defined core effects and internal cavitation resulting in delustering of the filament may occur under conditions of shock heating. The melting point of nylon is raised by the presence of stress.
Ultrasonic degradation of sol rubber in solution
Authors: Chandra Sarswati , Roy‐Chowdhury Phanibhusan , Biswas A. B.
Published: April 2003

Sol rubber dissolved in three solvents—cyclohexane, petroleum ether (40‐60°C. fraction), and toluene—was degraded by ultrasonic waves, the degradation kinetics being followed by measuring spectrophotometrically the consumption of the free radical scavenger α,α′‐diphenyl‐β‐picryl hydrazyl. The kinetic data have been examined by the rate equations developed from two different approaches: one by Jellinek and the other by Ovenall. It has been observed that the number of bonds broken as a function of time can be fitted equally well by both equations in the initial stage, but as the time of degradation increases, especially when the number‐average degree of polymerization attains a value less than 3Pe/2, the rate can be described better by Jellinek's equation than that of Ovenall. The rate constants K and the final degree of polymerization for rubber are found to depend on the nature of the solvent.
Block copolymerization of unsaturated monomers and octamethylcyclotetrasiloxane
Authors: Morton Maurice , Rembaum A. A. , Bostick E. E.
Published: April 2003

A study has been carried out on the preparation of block copolymers of styrene–dimethylsiloxane and isoprene–dimethylsiloxane. This has been accomplished by means of anionic polymerization, using potassium metal or potassium naphthalene as initiator, in tetrahydrofuran. Block copolymers of the ABA type were synthesized by first preparing the polystyrene or polyisoprene dianion, followed by polymerization of the octamethylcyclotetrasiloxane. Proof of the presence of these block copolymers was obtained from their solubility behavior and from the ability of the isoprene–siloxane polymers to undergo vulcanization by sulfur. The chain length of the polymeric blocks could be controlled in a predictable fashion, leading to a central segment (B) of polystyrene or polyisoprene, having a narrow molecular weight distribution, and two end segments (A) of polydimethylsiloxane, having a most probable distribution. The reverse type of block copolymer was not possible due to the inability of the siloxane to initiate styrene or isoprene polymerization.
Oxidation of cellulose microfibril segments by alkaline silver nitrate and its relation to the fine structure of cellulose
Authors: Colvin J. Ross
Published: April 2003

The oxidation by alkaline silver nitrate of segments (ca 0.1 μ long) of cellulose microfibrils from Avena coleoptiles, ramie, bacteria, and Valonia has been followed by electron microscopy. For comparison, chitin microfibrils have been oxidized by the same reagent and observed by the same method. Oxidation proceeds equally at both ends of the segments, as judged by the rate of deposition of colloidal silver. As a consequence of oxidation, dissolution of the ordered array of 1→4β‐polyglucosan chains (or poly‐N‐acetylglucosamine chains) takes place rapidly from both ends, due to Coulomb repulsion between ionized carboxyl groups and/or electrostriction of water molecules about the same groups. The observations are consistent with the assumption that the neighboring chains run in opposite directions in the cellulose microfibril (i.e., with the Meyer‐Misch antiparallel postulate). They are not in agreement with expectations based upon the parallel arrangement.
Determination of diffusion rates in swelling systems
Authors: Watt I. C.
Published: April 2003

A new method of measuring diffusion coefficients of ethyl alcohol in keratin is described. Ethyl alcohol, which is retained in keratin on desorption by evacuation, is released by swelling the keratin with water vapor. The essential measurement is the loss of weight of the keratin as the ethyl alcohol diffuses out after the absorption of water. Values of the diffusion coefficients at 35°C. are given for a range of volume swelling of keratin where it is not possible to obtain the data by absorption or permeation measurements. The change of diffusion coefficient with swelling is in agreement with values obtained by absorption at lower and higher levels of swelling. The method should have general applicability to many polymer sorption systems where swelling occurs.
Dielectric behavior of curing phenolic‐formal resins
Authors: Van Beek L. K. H.
Published: April 2003

Dielectric properties of phenolic‐formal resins are studied between 0.06 and 300 kHz. The resins are prepared from novolac and 1,3‐dioxalane with a strong acid as catalyst. The high dielectric losses are attributed to proton jumps felicitated by water molecules which are produced in the curing reaction. The activation energy of the dielectric relaxation is 0.77 e.v. Curing often continues for weeks after preparation, which is reflected by a gradual increase of the frequency of maximum loss. Drying the samples causes the loss maximum to return to lower frequencies.
Study of the structure of polymers by infrared spectra
Authors: Vol'kenshtein M. V. , Volchek B. Z. , Gotlib Yu. Ya. , Nikitin V. N.
Published: April 2003

In this review a short outline of the results of the application of IR‐spectroscopy to the study of polymer physics is summarized. Questions of rotational isomerism, mechanical deformation of polymers, crystallization, intramolecular order, and microtacticity determination are discussed. Details are given on the authors' data concerning polypropylene, 1,4‐trans‐polybutadiene, poly(methyl methacrylate), and cellulose triacetate, and also data on calculations of spectra for different conformations of poly(vinyl chloride), poly(vinyl bromide), and poly(ethylene terephthalate).
Monolayers of linear poly(vinyl benzoate) and its mixtures with stearic acid
Authors: Beredjick Nicky
Published: April 2003

Monomolecular films of linear poly(vinyl benzoate) (PVBz) and of mixtures of linear PVBz and stearic acid, show properties similar to branched PVBz and its mixtures with stearic acid. Nuclear magnetic resonance of linear and branched PVBz show no phenyl‐hydrogen splitting, chemical shift, or other differences in relative peak positions. These results are consistent with the structure of PVBz as derived from general mechanistic considerations. The unusual monolayer properties of this polymer may be attributed to superior contiguous alignment of aromatic rings and tighter packing, but not to branching.
Tack in urethane elastomers
Authors: Boenig H. V. , Miller C. B. , Shottafer J. E.
Published: April 2003

The phenomenon of tack has been studied in urethane‐urea elastomers prepared from polyether or polyester prepolymers and 4,4′‐methylenebis(2‐chloroaniline). It is shown that tack at zero elongation is attained only in polymers in which the flexible chains, i.e., polyesters or polyethers, contain 50 chain links or more. This coincides with the requirements for the Gaussian vector function in elastomers. The results suggest that, in the absence of flexible chain ends in these polymers, tack is solely contributed by the flexible segments along the polymer chains, while the rigid blocks in the chains do not participate in the formation of tack.
Polymers suitable for increasing the viscosity of formic acid: Application to the printing of wool with reactive dyes
Authors: Harrap B. S. , Rosman R. E. , Solomon D. H.
Published: April 2003

A study has been made of the properties of formic acid solutions of several polymers in relation to their usefulness as thickening agents for printing pastes composed of reactive dyes dissolved in formic acid. Polybases effectively increase the viscosity of formic acid to a satisfactory level but because of their ionization in formic acid, they inhibit the uptake of dye on wool due to the “salt effect” previously described. Incorporation of styrene with the base into a copolymer dilutes the salt effect but not sufficiently to be of practical importance. It was found that high molecular weight poly(ethylene glycol) and several natural carbohydrate gums effectively increased the viscosity without affecting the dye uptake. Moreover, contrary to their behavior in aqueous solutions, these natural gums did not react with the reactive dyes in formic acid solution. It is suggested that these dyes do not react with wool itself in formic acid solution, but reaction takes place only after the formic acid has been removed by washing.
Nonlinear dynamic behavior of plastics
Authors: Sharma M. G. , Sen J. K.
Published: April 2003

The dynamic behavior at low frequencies of Penton (chlorinated polyether) which displays nonlinear response is described in terms of a free energy function and a dissipated energy function. The variation of the energy functions with frequency and magnitude of stress is determined experimentally from hysteresis tests. The dynamic properties of the material are expressed in terms of storage and loss modulus functions. In addition the dynamic behavior of the material at low frequencies is predicted from uniaxial static creep properties, using a modified superposition principle.
Fracture surface work measurements on glassy polymers by a cleavage technique. I. Effects of temperature
Authors: Broutman L. J. , McGarry F. J.
Published: April 2003

It has recently been postulated that viscous flow or plastic deformation occurs near the tip of an advancing crack in glassy amorphous polymers such as Plexiglas, and this results in molecular orientation of the fracture surface. The evidence for this has been the appearance of colors on fresh fracture surfaces of Plexiglas and the extremely high measured surface work which is 1000 times greater than the theoretical surface energy. The surface energy of a solid is defined as the amount of energy required to create unit area of surface in the material by separating two planes each of half a unit area in extent, and the measured surface work of a polymer may also include any irreversible work which occurred during the fracture process. In the present investigation a cleavage test has been empolyed to measure the surface work of glassy polymers and to measure the effects of temperature on the surface work. A reproducible procedure has been developed to measure the surface work of cracks which propagate continuously and for cracks which propagate in a stick‐slip fashion. The measured surface work of Plexiglas II is 1.2 × 102 erg/cm.2, and the value for a typical polystyrene is 4 × 105 erg/cm.2, compared to a theoretical estimate of 450 erg/cm.2. The surface work varies with temperature over the range of −40 to 80°C. The surface work of Plexiglas II and polystyrene decrease with increasing temperature. Colors have been seen on the Plexiglas fracture surfaces over the entire temperature range, and the fracture surface changes from rough to mirror‐smooth at elevated temperatures. The inherent flaw size of the polymers, from Griffith's equation, also varies with temperature and is thought to be related to the crazing behavior of the polymer. At 23°C. the flaw size for polystyrene is 0.05 in. and for Plexiglas II, 0.002 in.
Application of differential thermal analysis to polyethylene blends
Authors: Stafford Bill B.
Published: April 2003

The analytical application of differential thermal analysis (DTA) for the identification and evaluation of a number of polyethylene blends is described. New DTA data are presented for hompolymer blends of low and intermediate density polyethylenes and low and high density polyethylenes whose degrees of branching are sufficiently different. The concentration by weight of each of the crystalline components in the blend is determined from DTA thermograms by the peak area method and the melting point‐density method. The density of polyethylenes and polyethylene blends is determined with the use of density gradient columns.
Specific heat of wool in the temperature range −50 to 100°C
Authors: Haly A. R. , Abu‐Isa I. , Dole Malcolm
Published: April 2003

The specific heat of wool containing 2.6, 2.9, and 8.9 g. of water per 100 g. 01 dry wool has been measured over the temperature range −50 to 100°C. All of the wool samples showed an approximately linear increase of cp, with temperature, but small increments appeared at −30, 20, 50, and 70°C. With increasing water content at any one temperature the specific heat increased. The specific heat of the sorbed water seemed to be more nearly like that of ice than of liquid water; if the sorbed water is assumed to have the specific heat of ice a t all compositions and temperatures, an apparent specific heat of the wool can be calculated. With increasing water content the apparent specific heat of the wool approaches that of the synthetic polymer, nylon 6.
Transient permeation of organic vapors through polymer membranes
Authors: Meares Patrick
Published: April 2003

A method of analyzing permeation data has been developed which permits the diffusion coefficient D, its variation with concentration, and the solubility coefficient to be determined from a single experiment on the permeation of a vapor through a membrane when diffusion is known to be Fickian. There is evidence that in the range from the glass temperature Tg to (Tg + 20°C.) the diffusion of an organic vapor into a polymer is not always Fickian. In such a case a single permeation experiment gives the limiting value of D at zero vapor concentration. If the sorption isotherm is determined, two or three permeation experiments give sufficient information to characterize the concentration dependence of D and to predict a “Fickian time lag.” The difference between the observed and the predicted time lag is the mean relaxation time of the time‐dependent factors in the non‐Fickian permeation. When there is a transient period of rapid permeation at the beginning of an experiment a plot of permeation rate against logarithmic time permits another relaxation time to be defined. By comparing these relaxation times with the mechanical characteristics of the polymer the time‐dependent mechanisms of permeation may be identified.
Factors affecting the solution properties of cellulose acetate
Authors: Neal J. L.
Published: April 2003

Absorbance measurements on concentrated solutions of cellulose 2 1/2‐acetates in acetone show that the apparent absorbance is almost entirely due to turbidity. The size of the scattering particles is comparable with the wavelength of light. Sedimentable fractions are responsible for the anomalous viscosity of concentrated solutions of cellulose acetates as well as for their turbidity. These sedimentable fractions are enriched in xylan and mannan acetate. Solubility differences found for sediments rich in either xylan or mannan acetate, and extraction experiments with polar and nonpolar solvents revealed that more polar impurities, such as xylan acetates, are responsible for turbidity, while less polar impurities, such as mannan acetates, are responsible for false viscosity. A hypothesis based on solvent interaction and polymer incompatibility has been advanced to coordinate these and earlier findings.
The photooxidation of polymers. IV. A note on the coloration of polystyrene
Authors: Grassie N. , Weir N. A.
Published: April 2003

Yellow coloration develops in polystyrene under 2537 A. radiation a t comparable rates whether or not oxygen is present. Thus the commonly accepted view that coloration is a manifestation of oxidation is wrong. The coloration increases in intensity with time but does not move toward the red end of the spectrum, behavior which is typical of poly(vinyl chloride), polyacrylonitrile, etc., and which is due to the development of long conjugation sequences. It is suggested that the color in polystyrene is due to conjugated carbon–carbon unsaturation in the polystyrene backbone but that the lack of mobility of the molecules within the rigid polymer films prevents long sequences of double bonds becoming coplanar and color consequently moving through the spectrum. The rapid darkening of irradiated polymer which occurs on melting is probably due to relaxation of this rigidity allowing coplanarity of longer sequences.
Cold water‐soluble films from cyanoethylated polyvinyl alcohol
Authors: Roth Roy W. , Patella Lawrence J. , Williams Bernard L.
Published: April 2003

The cyanoethylation of polyvinyl alcohol and the merits of using NaCN as the catallyst are discussed. The application of cyanoethylated PVA to cold water‐soluble films is specifically discussed. The use of NaOH catalysis was found to lead to nitrile hydrolysis which resulted in humidity‐susceptible films. By using NaCN catalysis, it was found that the reaction temperature and per cent solids could be increased resulting in a decrease in undersirable by‐product formation. It was found that films could be cast from cyanoethylated PVA with a degree of cyanoethylation between 5 and 10 mole‐% which were readily soluble in cold water and which had physical properties very similar to several commercial water‐soluble films.
Statistical analysis applied to film development: Grafted PVA‐based water‐soluble film
Authors: Bentz Alan P. , Roth Roy W.
Published: April 2003

A statistically designed experiment was used to optimize the physical properties of a cold water‐soluble film by establishing reliable estimates of the effects of the independent variables of the system. The system consisted of polyvinyl alcohol (low molecular weight, 88% hydrolyzed) to which is grafted ethyl acrylate by a ceric ion technique. To the grafted PVA is added a higher molecular weight PVA to strengthen film.
Effect of ethylamine treatment on dielectric properties and crystallinity of cellulose. II
Authors: Venkateswaran A. , Akker J. A. Van Den
Published: April 2003

Investigations have been made on the influence of (1) beating on the dielectric properties of cellulose, (2) beating before and after ethylamine treatment of cellulose, (3) compressive stress and moisture on the crystallinity of cellulose, (4) pelletizing cellulose for measurement of crystallinity, and (5) employing different methods of drying the cellulose on the crystallinity of cellulose. It was found that existing formulas involving the 002 peak intensity for estimating the crystallinity index seem to be inadequate. It is suspected that ethylamine treatment does not “decrystallize” cellulose but causes swelling of cellulose, resulting in an alteration in the lateral order structure of the so‐called “amorphous content” of cellulose. It is suggested that the moisture regain method is more suitable for comparing the dielectric constant and accessibility of cellulose.
Oxidation of styrene popcorn polymer
Authors: Chock David P. , Chock Ernest P. , Miller Glenn H.
Published: April 2003

Studies have been made of the oxidation of styrene popcorn polymer that was grown on butadiene popcorn seed. It was found that the solubility of the polymer increased after oxidation. This solubility was studied as a function of both temperature and butadiene content of the polymer. Oxidation of the styrene‐on‐butadiene popcorn occurs at the carbon atoms alpha to a double bond in the butadiene portion of the polymer. This is followed by scission of the structure and the separation of linear atactic soluble polystyrene chains.
Butadiene/styrene/2‐methyl‐5‐vinylpyridine terpolymer. Composition–conversion data in comparison with calculated values
Authors: Crescentini L. , Gechele G. B. , Zanella A.
Published: April 2003

Terpolymers from 1,3‐butadiene, styrene, and vinylpyridine are important as rubbers, and, in latex form, as components of rubber‐to‐fabric adhesives. Three monomer mixtures having the approximate weight composition butadiene/styrene/2‐methyl‐5‐vinylpyridine 70/15/15, 25/48/27, and 38.5/49/12.5 have been emulsion‐polymerized at 30°C., and the terpolymer composition as a function of the conversion has been studied. The six monomer reactivity ratios have been determined by binary copolymerizations at 30°C. and checked by low conversion bulk terpolymerizations. Average and instantaneous composition–conversion curves have been calculated, on the assumption of a constant reaction volume, by numerical integration of the terpolymerization equations on electronic computer. Details, of general applicability, for calculations are given. The experimental results of the emulsion terpolymerizations fit satisfactorily the calculated curves over a wide range of conversions.
Sulfur group analysis in unaccelerated vulcanization of natural rubber
Authors: Chakravarty Shomnath , Chatterjee Pronoy K. , Sircar Anil K.
Published: April 2003

The reaction of lithium aluminum hydride forming mercaptan with disfulfides and mercaptan as well as hydrogen sulfide with polysulfides has been applied in order to characterize the structure of the crosslinks in the case of unaccelerated vulcanization of natural rubber with sulfur. The mercaptans formed were determined amperometrically, and the hydrogen sulfide was determined as cadmium sulfide. These measurements, coupled with the estimation of total crosslinks as measured by swelling, provide valuable information as to the distribution f different crosslinks (monosulfide, polysulfide, cyclic structures, etc.) in the vulcanizate. When extended to compounds of different sulfur concentrations (2.92‐33.9%) these studies show how the distribution of different linkages changes with sulfur concentration from compositions corresponding to soft rubber to those corresponding to hard rubber. The present study provides conclusive evidence that the long polysulfidic crosslinks first formed during vulcanization decrease in chain length as vulcanization progresses. Polysulfides also increase with the increasing sulfur content in the stock except in the range 6‐10%. Monosulfidic crosslinks increase with increasing sulfur in the stock. In contrast to accelerated vulcanization, a high proportion of combined sulfur was found to be present in cyclic structures, and this increases with temperature of curing. These findings tally with the results of the earlier workers and have been explained with the present day ideas of the vulcanization reaction. Inaccuracies in the measurements and inherent limitations of the method were discussed.
Stress relaxation of polytetrafluoroethylene in the vicinity of its glass transition temperature at about 130°C.
Authors: Araki Yoshio
Published: April 2003

Measurements of compressive stress relaxation for molded polytetrafluoroethylene were carried out at different temperatures over the range 60–150°C., at 5°C. increments under a small strain (less than 0.3%). By the application of the so‐called Ferry's reduction method, three master curves were obtained with good overlapping from a series of stress relaxation curves obtained at different temperatures for the same specimen. This polymer has two temperatures at which the three master curves cross and the reduction method becomes entirely in applicable. Those two temperatures are about 80 and 100°C. It may be concluded that this polymer has two first‐order transitions at about 80 and 100°C., and the states above and below these temperatures are quite different, as in the case of the transition observed for this polymer at about 20°C., which has been confirmed to be a first‐order transition in crystal structure. The reduction factors aT at different temperatures were plotted in logarithmic scale against the reciprocals of the absolute temperatures. From the slope of those three log aT vs. 1/T curves, the diagrams of the apparent activation energy vs. temperature were obtained. There were two sharp maxima at about 120 and 130°C. in the diagram, where this polymer also has two irregular changes in other viscoelastic properties. It is conceivable that these changes at 120 and 130°C. are second‐order transitions occurring in the amorphous region of the polymer.
Filler particle size and mechanical properties of polymers
Authors: Alter Harvey
Published: April 2003

Literature data for the effect of mineral fillers on the mechanical properties of polyethylene at two temperatures, styrene–butadiene rubber, and natural rubber were examined. The data for modulus, tensile strength, elongation at yield, and ultimate elongation could be well represented by linear plots of the relative mechanical property (ratio of the values for the filled to the unfilled) as functions of the reciprocal of the filler particle size. A plot of one of these properties versus reciprocal filler size shows a family of lines, one line for each concentration of filler, and independent from the chemical nature of the filler. The dependence of the mechanical properties on reciprocal particle size may express a dependence on the surface‐to‐volume ratio of the filler, a balance between the effective cross‐linking due to the large surface area of the filler, and the dilution of the polymer by the volume of filler present.
Some relationships between molecular structure and flow in linear polyethylene
Authors: Schreiber H. P.
Published: April 2003

The flow curves of linear polyethylenes are characterized by a set of empirically defined parameters, including the apparent melt viscosity at zero shear stress, the shear stress for onset of non‐Newtonian flow, and the slopes of linear sections fitted to data in three shear stress ranges of the flow curve. Not all of these parameters have theoretical significance but all are easily measured and therefore should be useful for broad, practical application. The dependence of the parameters on molecular weight, shape, and breadth of the molecular weight distribution has been demonstrated by using fractions and blends of fractions of linear polyethylenes. The zero shear viscosity and degree of non‐Newtonian flow at low shear stress depend primarily on polymer molecular weight. The degree of non‐Newtonian flow at higher shear stress can be related quantitatively to molecular weight distribution factors, while the stress for onset of non‐Newtonian flow also correlates with molecular weight distribution. Formally, the derived correlations are specific to the apparatus used, but may in fact have much broader validity because of the minor importance in these polymer samples, of elastic effects such as capillary die entry effects.
Photodegradation of cis‐1,4‐polyisoprene sensitized by the addition of chloronitroso compounds
Authors: Rabek J. F.
Published: April 2003

It was found that chloronitroso compounds with a free non‐conjugated nitroso group show a considerable sensitizing activity in respect to the process of photochemical degradation of dissolved cis‐1,4‐polyisoprene, which is induced by visible radiation (4000–7000 A.). The effect of 10 chloronitroso sensitizing compounds were investigated. The highest sensitizing activity was found with compounds 2,2‐chloronitrosopropane and 1,1‐chloronitrosocyclohexane. The maximum wavelength, of which the decrease of relative viscosity of solutions was the highest, was determined for 2,2‐chloronitrosopropane. The highest sensitizing activity of chloronitroso compounds was found for wavelengths corresponding to the absorption maximum of the sensitizer added. The theory of the sensitizing activity of chloronitroso compounds is proposed.
Anionic heterogeneous polymerization of acrylonitrile by butyllithium. II. Effect of lewis bases on the molecular weight
Authors: Feit Ben‐Ami , Mirelman David , Katz Y. , Zilkha Albert
Published: April 2003

The heterogeneous polymerization of acrylonitrile in petroleum ether by butyllithium in the presence of Lewis bases was investigated. Molecular weights increased sharply on addition of small amounts of Lewis bases. High, maximal molecular weights were obtained at optimal values of [Lewis base]/[BuLi] = 1–2. Beyond this optimum a sharp decrease of molecular weights was observed. The optimal [Lewis base]/[BuLi] ratio was dependent on the Lewis base used and was specifically related to the structure of the complex Li+ Lewis base. The effectiveness of the Lewis bases in obtaining high molecular weights was as follows: DMF ≫ THF ∼ dioxane > dimethylacetamide. A nonterminated “living” polymerization for which DP was given by DP = Rp/Ri was observed with low rates of monomer addition, whereas chain transfer to monomer occurred with high rates. This behavior was qualitatively the same as that found in the absence of any Lewis base. However, under comparable conditions, higher molecular weights were always obtained in the presence of a Lewis base, except for relatively high ratios of [Lewis base]/[BuLi]. It was suggested that at the optimal ratio of [Lewis base]/[BuLi] and beyond it, all the positive Li+ ions in the polymerization mixture were solvated by the Lewis base. This solvation increased the nucleophilic reactivity of the carbanions. On increasing the Lewis base concentrations up to the optimal value of [Lewis base]/[BuLi], Rp increased much more than Ri, which resulted in a sharp increase of molecular weights. Beyond the optimal value of [Lewis base]/[BuLi] where all the positive counterions of the propagating ends were completely solvated, added Lewisbase might cause further dissociation of the associated [BuLi]n, leading to a larger increase of Ri as compared to Rp, and consequently to a decrease of DP.
Determination of primary and secondary xanthate groups in cellulose xanthate
Authors: Dunbrant Stig , Samuelson Olof
Published: April 2003

Various kinetic methods for the determination of primary and secondary xanthate groups have been compared. With certain types of viscoses all methods give an excellent agreement and are superior to the purely chemical methods which are unreliable. The field of application of a kinetic method based upon decomposition in a slightly acid buffer is limited due to the appearance of a turbidity upon prolonged dexanthation. A modified technique in which the decomposition is carried out at elevated temperature in sodium hydroxide solution is both rapid and versatile.
Regulation of molecular weight distribution in the polymerization of butadiene–styrene and butadiene–nitrile rubbers
Authors: Poddubnyĭ I. Ya. , Rabinerzon M. A.
Published: April 2003

Conditions for the preparation of butadiene–styrene and butadiene–nitrile rubbers with desirable molecular weight distributions were developed; regulators of different activities were used in the polymerizations. The character of the dependencies of properties of the butadiene–styrene rubbers on the molecular weight distribution of the polymers was established. Butadiene–styrene and butadiene–nitrile rubbers with the desired distributions and good elastic‐plastic and physical‐mechanical properties were obtained. These rubbers are now commercially produced on the basis of these findings.
Physical properties and structure of the polyethylene produced by γ‐radiation polymerization
Authors: Machi Sueo , Tamura Takeshi , Fujioka Shuji , Hagiwara Miyuki , Gotoda Masao , Kagiya Tsutomu
Published: April 2003

Polyethylene produced by γ‐radiation had short‐chain branching to some extent and a small amount of vinylidene unsaturation. An OH group was found in polyethylene produced in the presence of methanol. The properties and structure of the polymer were found to vary widely with changes in the reaction condition, such as ethylene pressure, reaction temperature, time, and dose rate. Polymer density, an important property, varied from 0.88 to 0.96 g./cc. and crystallinity from 40 to 80%, depending on the reaction conditions. Polyethylene polymerized at room temperature at a pressure of 300–400 kg./cm.2 was shown to have an extremely high molecular weight (up to 300,000) and low methyl content (below 0.5CH3/100C). Density depends solely on the crystallinity of the polymer, which was found to be determined by the degree of short‐chain branching and molecular weight. Quantitative relationships between them were obtained. The use of methanol as a solvent was found to have no effect on short‐chain branching but have a marked effect on molecular weight; hence, high‐density polyethylene could be obtained with the use of methanol solvent. Polyethylenes with a high molecular weight (above 100,000) had a higher melting point than high‐pressure polyethylene. The quantitative correlation between molecular weight and melt index was also determined and found to be similar to that of Sperati. Some mechanical properties were also measured.
Sedimentation analysis of 1,4‐cis‐polybutadiene in a theta solvent, diethyl ketone at 10.3°C
Authors: Abe Mitsuo , Murakami Yuriko , Fujita Hiroshi
Published: April 2003

A sedimentation and viscosity study of 1,4‐cis‐polybutadiene (having 95% 1,4‐cis units) in a θ‐solvent diethyl ketone (DEK) at 10.3°C. is reported. The limiting sedimentation coefficient so and the limiting viscosity number [η]θ of the monodisperse sample of this polymer in the given θ‐solvent as functions of its molecular weight M are derived from data on polydisperse fractions by application of the method described by Homma et al. The results are: so = 0.530 × 10−15M1/2 (in sec.) and [η]θ = 1.60 × 10−3M1/2 (in dl./g.). Substitution of the experimental data into the well‐known Mandelkern‐Flory equation yields 1.74 × 106 for the familiar parameter Φ1/3 P−1, which is about 30% lower than the usually accepted value (2.5 × 106).
Suspension polymerization of caprolactam
Authors: Gechele G. B. , Martinis G. F.
Published: April 2003

The anionic polymerization of caprolactam (with sodium hydride and acetyl caprolactam as catalysts) carried out in glass ampules is reported. The effect of the catalyst concentration, polymerization temperature, and other variables was studied. Polymerization of caprolactam at temperatures around 120°C. in a paraffin suspension, in which the paraffin was introduced into a syrupy prepolymer is also reported. The influence of a few variables on conversion, molecular weight, particle size distribution, is discussed. Both viscosity and conversion are always lower in suspension than in bulk polymerization. Polymer granules of a wide range of dimensions which generally contain some residual monomer (unlike the bulk polymerization) are obtained in suspension polymerization. The above results are discussed and some interpretations are suggested.
Apparatus for determining thermal conductivity of insulation materials
Authors: Goldfein S. , Calderon J.
Published: April 2003

The initial object of this investigation was to design and build an apparatus capable of screening insulation materials for use in arctic shelters. A further object was to determine its suitability for determining thermal conductivity. The apparatus comprised a steel heat sink embedded in a 6‐in. core of polyurethane foam coated with glassreinforced plastic. The specimen rested upon the heat sink, and a constant temperature bath rested, in turn, on the specimen. A potentiometer was used to measure the temperature of the sink by means of a connecting thermocouple. After calibration, the apparatus was found to be highly accurate in determining thermal conductivity.
Oxidative stress relaxation of blends of cis‐1,4‐polybutadiene and natural rubber
Authors: Bell C. L. , Tiller R.
Published: April 2003

Blends of cis‐1,4‐polybutadiene and natural rubber were vulcanized with dicumyl peroxide and a CBS (N‐cyclohexylbenzothiazole‐2‐sulfenamide) accelerated sulfur system. For the peroxide‐cured systems, soft vulcanizates had the natural rubber component only very lightly crosslinked and showed pronounced flow at room temperature. The oxidative stress relaxation of the hard vulcanizates at 80°C. in air was intermediate between that of the pure polymers. Intermittent stress relaxation measurements on these vulcanizates showed pronounced crosslinking during the aging of the pure polybutadiene and the 50/50 blend. Soft blends prepared by the accelerated sulfur system also showed flow due to the lightly crosslinked polybutadiene component. The unextracted hard blends resembled the pure polybutadiene vulcanizate in oxidative stress relaxation behavior at 80°C. in air, whereas after extraction to remove residual antioxidant and vulcanization products, etc., the blends were similar to natural rubber at all levels.
Rheopexy in some polar fluids and in their concentrated solutions in slightly polar solvents
Authors: Steg I. , Katz D.
Published: April 2003

Several medium and high molecular weight polar fluids, when subjected to shearing forces above a certain rate of shear, showed a rheopectic behavior. The observation was made on some polyesters, an epoxy compound, and on concentrated solutions of these materials in nonpolar solvents. The experiments were carried out in a rotating type viscometer with cone‐and‐plate arrangements. The following explanation for the observed rheopexy is proposed: above a critical rate of shear, the polar macromolecules after alignment in the field of shear are forming quasicrystallites and a rheological network structure due to intermolecular forces. Because of the simultaneously occurring process of the breaking of structures in the field of shear, a state of pseudoequilibrium is reached. It was found that when the experiments were interrupted at the stage of such a pseudo‐equilibrium for a short time, a thixotropic strengthening of the existing structure occurred; under renewed shear the stress decreased to its value before the interruption. After interruption of shear for longer periods (hours, days), a breakdown of the rheopectic structure was observed.