bluuebunny/crossref_metadata_2025 huggingface dataset:
Method of calculating molecular weight distribution function from gel permeation chromatograms. II. Evaluation of the method by experiments
Authors: Tung L. H. , Moore J. C. , Knight G. W.
Published: April 2003

The calculation scheme for correcting the broadening effect due to imperfect resolution on gel permeation chromatograms was compared with actual performances of a gel permeation chromatography (GPC) column. The experiment consisted of fractioanting a high‐density polyethylene on a GPC unit and then determining the chromatograms of the cuts collected. The chromatograms of the cuts were also computed from the starting chromatogram using experimentally determined resolution factors. The degree of agreement between the calculated and experimental chromatograms of the cuts shows convincingly that the previously proposed calculation scheme is satisfactory for the treatment of GPC data.
Method of calculating molecular weight distribution function from gel permeation chromatograms. III. Application of the method
Authors: Tung L. H.
Published: April 2003

Six examples were used to illustrate the application of a previously reported method of calculating molecular weight distribution from gel permeation chromatograms. These examples show that the correction for the imperfect resolution of the GPC column is important when the distribution is narrow but minor when the distribution is broad. They show also that the variation of the resolution factor h, defined previously, with eluent volume can be neglected in the calculation. When the chromatograms are very narrow in distribution or when they are complex some difficulties are encountered. The two computer programs written to implement the previously described numerical calculations are shown to be adequate for these difficult cases but there are also limitations.
Fractional turbidimetric analysis of the molar substitution of hydroxyethyl cellulose
Authors: Muller Thomas E. , Alexander W. J.
Published: April 2003

High quality packaging films from hydroxyethyl cellulose of low degree of substitution (DS) are being produced commercially in this country and abroad. Increasing demand for this and a variety of other applications requires a rapid and simple production control method for determining hydroxyethyl substitution of cellulose. None of the known analytical methods fulfills these requirements. The present paper describes a method which is based on the relationship between the solubility and the molar hydroxyethyl substitution of hydroxyethyl cellulose. A washed and dried sample of hydroxyethyl cellulose is dissolved in 7% aqueous sodium hydroxide. Methyl alcohol, a nonsolvent, is used to precipitate a fraction of the sample. The turbidity of the equilibrium system is determined and optical density readings are related to molar substitution. The method is most useful in low DS ranges of 2–8% EtO but is susceptile to broader application through adjustment of the composition of the solvent–nonsolvent mixture. Relatively large variations in DP can be tolerated. The molar substitution level of an hydroxyethyl cellulose sample can be obtained in 40 min. by this method, making it a practical production control technique.
Spontaneous polymerization of acetaldehyde to polyacetaldehyde at close to dry‐ice temperature
Authors: Georgieff K. K.
Published: April 2003

Polyacetaldehyde has been prepared in the liquid and vapor phases without the addition of a catalyst by storing undiluted acetaldehyde in the dark at a temperature of −68°C. for 3–6 months. When acetaldehyde was stored in an untreated Pyrex flask, 20% high polymer, 55% paraldehyde, and less than 1% metaldehyde were obtained. The polymer was an elastomeric solid with a low to moderate degree of crystallinity and an intrinsic viscosity of 0.63 dl./g. When the sample was stored in a Pyrex flask which had been pretreated with alcoholic potassium hydroxide followed by a water wash, 16–17% high polymer and 6% paraldehyde were obtained. Some polymer formed on the unwetted glass above the liquid. It was slightly elastic, at least moderately crystalline, and had an intrinsic viscosity of 1.6 dl./g. It is suggested that the formation of this polymer was initiated by basic active sites on the Pyrex surface which acted by an anionic mechanism. Also some polymer was formed in the liquid phase. This material was an amorphous, highly viscous oil with an intrinsic viscosity of 0.28 dl./g. It was probably formed by a cationic mechanism. It is also suggested that a relatively small amount of paraldehyde was formed in the alkali‐treated flask in the liquid phase due to neutralization of the Brønsted acid sites and possibly some of the Lewis acid sites on the surface of the flask.
Infrared spectroscopical investigation of cotton subjected to swelling and deswelling treatments
Authors: Åsnes Harald , Wickman Bengt O.
Published: April 2003

The setting of textiles made from cellulosic materials can be done with swelling and deswelling processes. Standard cotton fibers, purified by extraction, have been set in sodium hydroxide solutions with and without additions of thiocyanate salts. Treatments have also been done in zinc chloride and calcium thiocyanate and in a solution of potassium hydroxide in a mixture of butanol and kerosene. After rinsing and drying of the cotton samples, KBr pellets for infrared investigations were produced. Deuteration of the fiber sample for investigation was made in a special apparatus. Single and differential infrared diagrams have been run with and without previous deuteration of the set cotton samples. The infrared maximum of absorption of the OH band changes as a result of the setting treatment. The infrared diagrams show that the setting treatment in alkaline solution gives a broadening of the OH band towards higher and lower wavelengths, which indicates a transfer of the hydrogen bonding energy both to higher and lower energies. The diagrams from the deuterated samples indicate that the strong hydrogen bonds resulting from the setting treatment are partly resistant to deuteration. The results are discussed on the basis of setting and setting reactions.
Fracture toughness of an epoxy system
Authors: Mostovoy S. , Ripling E. J.
Published: April 2003

The fracture toughness of epoxy used in the bulk and adhesive form was measured by a previously developed technique. The uniform double cantilever‐beam specimen, which was described earlier, was modified to a tapered beam, which simplified the experimental procedure and calculations for obtaining toughness measurements. by varying the ratio of hardener to resin and post‐cure temperature on a single epoxy system (DER 332‐TEPA), it was found that the toughness of the epoxy used in either bulk or bond form varied by a factor of approximately five. A particular combination of composition and post‐curing temperature generally yielded higher toughness in the bulk than in the bond form. This was not always the case, however. At high post‐cure temperatures, where the bonds were very tough, their toughness exceeded that of the bulk material. Hence, it does not appear possible to predict joint toughness from bulk toughness measurements. The toughness of joints was found to be a single‐valued function of tensile modulus. For the bulk material, on the other hand, the toughness obtained on the epoxy having a specific modulus depended on the combination of composition and post‐cure temperature. Joint toughness for any combination of composition and post‐cure temperature depended only on the cracking rate. If the epoxy was the type that caused cracks to jump rapidly, the epoxy was tough and vice versa. For a particular epoxy system, toughness was increased by driving the crack at an increasing rate.
Crystallization from the glassy state
Authors: Collier John R. , Baer Eric
Published: April 2003

Isothermal crystallization of poly[3,3‐bis(chloromethyl)oxacyclobutane] and poly‐(ethylene terephthalate) from the quenched glassy state gave small lamellae approximately 1000–2000 A. in lateral dimension with a constant thickness of about 100 A. The maximum primary nuclei density for crystallization slightly above the glass transition temperature, Tg, was 1010 greater than frequently observed during spherulitic growth from the melt. Since the lamellae grow at a linear rate, the crystallization process could be described by the Avrami theory for two‐dimensional growth with a constant nuclei density. By assuming that crystallization near Tg is diffusion‐controlled, bulk crystallization rate data were analyzed to obtain self‐diffusion coefficients whose activation energies were similar to reported values for other polymers.
Pressure–volume–temperature behavior of nylon 610
Authors: Haug William A. , Griskey Richard G.
Published: April 2003

Equilibrium pressure–volume–temperature behavior in both the solid and molten regions was determine for nylon 610. Data were measured with a compressibility device capable of obtaining precise and accurate data. Residual curve treatment showed that the data were true equilibrium data. A volume extrapolated to 2419 atm. at room temperature from the present data compared favorably to the sole literature value reported by Bridgman. The data of this work showed the existence of what appears to be a second‐order transition point for nylon 610. This point ranged from 140°C. at 232 atm. to about 170°C. at 1855 atm. The Spencer‐Gilmore equation was fitted to the data of this study.
Comparison of tensile stress relaxation behavior of graft copolymer of poly(vinyl acetate) with styrene and mechanical mixture of poly(vinyl acetate) with polystyrene
Authors: Soen Toshiichi , Horino Tzuneo , Ogawa Yasuo , Kyuma Koichi , Kawai Hiromichi
Published: April 2003

As one in a series of studies relating the rheological behavior of mechanical mixtures of two polymer components to the degree of mixing, the tensile stress relaxation behavior of a graft copolymer of poly(vinyl acetate) with styrene, obtained by 60Co γ‐irradiation of poly(vinyl acetate) in styrene solution and extraction of homopolymers, was investigated as a function of the fraction of styrene component and compared with that of a mechanical mixture of poly(vinyl acetate) with polystyrene, one of the typical combinations of incompatible components. The results obtained may classify the graft copolymer as a sort of mechanical mixture giving stable mixing even for incompatible components.
Proton magnetic resonance investigation of the orientation of hydrogen bonds in nylon 66, poly(vinyl alcohol), and cotton yarn
Authors: Gupta Ramdas P.
Published: April 2003

Directional dependence of the PMR‐narrow‐band in oriented fibers of nylon 66, poly(vinyl alcohol), and cotton has been investigated to study the orientation of hydrogen bonds in the unit cell. Filaments of oriented fibers were conditioned to 75% relative humidity, then aligned together axially and packed in a teflon tube. The teflon tube was suspended in the NMR probe in such a manner that the fiber axis was horizontal and could be rotated to a desired angle with respect to the magnetic field. Variation of the narrow‐band line width as a function of the angle between the fiber axis and the magnetic field‐direction shows a minimum at 0° orientation for nylon 66 and PVA, but in the case of cotton it shows a minimum at about 80° orientation. This indicates that in the case of nylon 66 and PVA, hydrogen bonds are oriented nearly prependicular to the chain axis. This would suggest that nylon 66 and PVA have interchain hydrogen bonding, but the hydrogen bonds contributing to directional dependence, in the case of cotton fiber, are intrachain. The interchain hydrogen bonds between the lateral chains, if they exist, must be random and, therefore, do not contribute to directional dependence. The interchain H bonds between central and corner chains are probably oriented in such a way that the horizontal component of p–p vectors have nearly the same orientation in the unit cell as the p–p vectors of the intrachain hydrogen bonds.
Abrasion characteristics of polypropylene yarns
Authors: Ross Stanley E. , Wolf Harold W.
Published: April 2003

The abrasion characteristics of low‐twist polypropylene multi‐filament yarns free of surface lubricants were determined by rubbing the yarns against each other by using a reciprocating action device at a frequency of 60 cycles/min. It was found that the abrasion behavior of the yarns varies over a wide range and is related to such fundamental properties as the polymer and fiber molecular weight, undrawn fiber orientation and crystalline structure, drawn fiber properties, and elevated temperature post‐treatment. It was also found that presence of surface lubricants could increase the number of abrasion cycles to failure by as much as a factor of 20, depending upon the particular lubricant employed. The mechanism of the process of fiber failure resulting from abrasion damage was examined and appears to be one in which the fiber rupture is preceded by a tearing and peeling back of fiber surface fragements probably initiated at flaws in the fiber surface.
Poly(vinyl chloride) thermal stability. I. Evaluation by melt rheology
Authors: Collins Edward A. , Krier Charles A.
Published: April 2003

Capillary rheometry is used to characterize the thermal stability of poly(vinyl chloride). By isothermally extruding the polymer melt at constant shear rate, apparent viscosity–time relationships are obtained having three distinct regions: (1) obtainment of equilibrium viscosity, (2) constant viscosity, and (3) rapidly changing viscosity. During regions 2 and 3 the polymer extrudate gradually changes in color from water clear to black. These characteristic regions are related to the temperature of extrusion by Arrhenius plots. An activation energy of 40 kcal./g.‐mole was calculated for the decomposition of PVC. Infrared spectroscopy, thermal gravimetric analysis, and intrinsic viscosity experiments are used to corroborate the results of the melt flow data.
ESR study of reactions of cellulose initiated by the ceric ion method
Authors: Arthur Jett C. , Baugh Peter J. , Hinojosa Oscar
Published: April 2003

The ESR spectra of microcrystalline cellulose and purified cotton cellulose reacted with ceric ammonium nitrate in nitric acid were determined. The effects of the concentration of ceric ion, atmosphere, temperature, and graft copolymerization with acrylonitrile on the rates of formation and decay of radicals in the cellulose molecule were determined under both static and dynamic conditions. Under static conditions, after the desired conditions of reaction, the samples were frozen at –100 or –160°C., and then the concentration of free radicals was determined. Under dynamic conditions ceric ion solution was continuously flowed through the celluloses while these determinations were being made at 25°C. In the presence of oxygen the rate of decay of free radicals was decreased. On initiation of copolymerization reactions with acrylonitrile, there was an increase in radical concentration, then a decrease. Apparently, during graft copolymerization the radical site initially on the cellulose molecule was retained on the end of the growing polymer chain. Then additional ceric ion coordinated with the hydroxyl groups of the cellulose, leading to the formation of additional radical sites. An Arrhenius interpretation of the effect of temperature on the formation of these additional radical sites gave apparent activation energies for radical formation on cotton cellulose as 34 kcal./mole and on microcrystalline cellulose as 29 kcal./mole.
Interfacial polymerization of n‐alkyl α‐cyanoacrylate homologs
Authors: Leonard Fred , Collins John A. , Porter Harold J.
Published: April 2003

The n‐alkyl α‐cyanoacrylates from methyl through n‐octyl exhibit a reverse order of polymerization rate on biological substrates compared to that on water. On water, the lower homologs spread and polymerize rapidly, whereas the higher homologs spread but polymerize slowly. On biological substrates, the lower homologs do not spread or spread slightly and the higher homologs exhibit large spreadabilities and very rapid polymerization rates. Determination of the spreading coefficients for these systems by using the monomers or model compounds confirm the observed spreadabilities. It is proposed that the increased rate of polymerization of the higher homologs on biological substrates may be due to increased catalyst concentrations on these surfaces or to the solubilization of the higher homologs at the interface, making the catalyst sites more available to the monomer. The suggestion is made that if the liquid monomers spread and orient on the substrate and subsequently polymerize, the polymers will maintain the orientation. If such is the case, a technique is available for preparing stereospecific vinyl polymers which may have different spatial configurations depending on the polarity of the liquid substrate upon which they have been allowed to spread and polymerize.
Estimating elution fractionation conditions for linear polyethylene and isotactic polypropylene
Authors: See Benito , Smith Theodore G.
Published: April 2003

A technique has been developed which provides a means for estimating polypropylene fractionation conditions in an elution column from a knowledge of the fractionation conditions used to fractionate linear polyethylene in the column and the solution behavior of both polymers in the same solvent‐nonsolvent system of varying compositions. The fusion behavior of linear polyethylene and isotactic polypropylene in mixtures of o‐di‐chlorobenzene and dimethyl phthalate of varying compositions has been studied by a differential thermal analysis (DTA) technique using concentrations similar to those in an elution fractionation column. The column temperature for fractionating each of these polymers by using o‐dichlorobenzene and dimethyl phthalate as the solvent and nonsolvent, respectively, was determined from their melting temperatures in dimethyl phthalate. On the basis of the equivalence of the fractional depression in solution temperature of each polymer in the binary liquid mixture, the composition range of solvent‐nonsolvent mixtures to be used in fractionating polypropylene was estimated from a knowledge of the polyethylene fractionation conditions together with the DTA data. Although separation depends primarily on molecular weight, the equivalence in fractional solution temperature depression provides a convenient means of correlating fractionation conditions for the polyolefins investigated.
Free volume treatment of concentrated polymer solutions
Authors: Pezzin G. , Gligo N.
Published: April 2003

Very different concentration dependences of the viscosity of polymer solutions are predicted by the free volume treatments of Fujita and Kishimoto and of Kelly and Bueche. This latter is conveniently extended, and it is shown that it can describe a given set of experimental data over a concentration range much larger than the Fujita‐Kishimoto equations.
Effect of molecular weight on the breaking time of a glassy polymer
Authors: Kwei T. K.
Published: April 2003

An analysis of the dependence of the breaking time tb of a glassy polymer under constant stress on the molecular weight of the polymer is made with the use of the theories by Bueche and by Cohen and Turnbull. It is concluded that log tb is proportional to the degree of polymerization x when x is small but becomes independent of x at large values of x.
Block copolymerization of formaldehyde
Authors: Smith W. E. , Galiano F. R. , Rankin D. , Mantell G. J.
Published: April 2003

Solubility and spectroscopic evidence are presented to support the formation of A‐B block copolymers between monomers undergoing anionic polymerization (A units) and monomeric formaldehyde (B units). Comonomers included in the study were styrene, methyl and n‐butyl methacrylate, acrylonitrile, isoprene, and N, N‐di‐n‐butylacrylamide. Similar evidence is presented on the formation of B‐A‐B copolymers between styrene and α‐methylstyrene and formaldehyde; an A‐(B‐C) random copolymer of styrene, formaldehyde, and phenyl isocyanate (C) was also prepared. Experimental details for the preparation of high‐purity, monomeric formaldehyde suitable for such work is described in some detail. It should be emphasized that this study was directed primarily toward showing the feasibility of preparing formaldehyde block copolymers; therefore, further work is needed to establish the quantitative nature of these reactions.
Mechanisms of oxidative degradation. I. Oxidation of synthetic rubbers catalyzed by metallic ions
Authors: Lee Lieng‐huang , Stacy C. L. , Engel R. G.
Published: April 2003

The oxidative stability of rubbers depends on the structure of the rubber and the impurities contaminating the rubber. It is known that the oxidation of natural rubber is accelerated by the presence of metallic impurities. Besides GR‐S rubber and nitrile rubber, the effects of metallic impurities on the oxidation of new rubbers, especially those introduced after the discovery of Ziegler‐Natta catalyst, have not been reported. In the first part of this paper, the theoretical background on the mechanisms of metalcatalyzed oxidation is given. Most of the early work was carried out for the oxidation of hydrocarbons in the liquid phase. The difficulties in applying the liquid‐phase results to the oxidation of high polymers in the solid phase are mentioned. The new rubbers used for this study are polyisoprene, polybutadiene, cis‐poly‐1,3‐butadiene, styrenebutadiene copolymer, butyl rubber, ethylene‐propylene terpolymer (EPT), propylene oxide rubber, polyacrylic rubber, and butadiene‐acrylonitrile rubber. The effects of stearic acid and various stearates on the oxidation of these rubbers are presented. The number of electrons transferred by the metal ion during redox reactions was found to be related to the effectiveness of the ion as a catalyst. Both the high and low oxidation states of the metal ion were shown to be active catalysts, supporting the accepted theory of metal catalysis through a hydroperoxide decomposition mechanism.
Elastomeric and mechanical properties of poly‐m‐carboranylenesiloxanes
Authors: Sperling L. H. , Cooper S. L. , Tobolsky A. V.
Published: April 2003

A new high‐temperature elastomer, SiB‐2, has been investigated by stress relaxation, modulus‐temperature, and volume‐‐temperature techniques. SiB‐2 was found to be more stable than a related elastomer, radiation‐cured silicone rubber, having about twice as long as a chemical relaxation time at 250°C. Possible mechanisms to account for this increased stability are discussed. At low temperatures, Tg for SiB‐2 was estimated at –34°C., which compares well with Ti = −30°C. for this polymer. By comparison, SiB‐3 has Ti = −60°C., while phenyl‐modified SiB‐4 was found to have Ti = −25°C. Tm for SiB‐2 was estimated to be + 56°C.
A measure of effective crosslinks in formaldehyde‐modified cotton celluloses
Authors: Rowland Stanley P. , Post Arnold W.
Published: April 2003

Sol‐gel fractions have been measured for cotton celluloses crosslinked with formaldehyde under widely different conditions of reaction and have been employed for estimation of the efficiency of crosslinking in the various processes. Most efficient utilization of formaldehyde for insolubilization of molecular chains is indicated for an aqueous process (form W′) and least efficient utilization is indicated for a nonaqueous process (form D′), the difference in efficiency being approximately a factor of 40. Interpretation of sol‐gel data has been made relative to a model assuming random reaction of crosslinking agent throughout the cotton cellulose and by relationships developed by Charlesby and Pinner and by Shultz. This leads to estimates of relative numbers (moles) of effective chain elements per gram, ve (i.e., twice the number of effective crosslinks), which decrease in the following sequence for cottons at the 0.20% level of formaldehyde (i.e., 6.7 × 10−5 mole/g.): aqueous process, higher formaldehyde concentration (W′, ve = 4.8 × 10−5), vapor process (V, ve = 1.75 × 10−5), bake‐cure process (C, ve = 1.37 × 10−5), aqueous process, lower formaldehyde concentration (W, ve = 0.95 × 10−5), nonaqueous process (D, ve = 0.03 × 10−5).
Inhibited oxidation of vulcanized natural rubber
Authors: Bevilacqua E. M.
Published: April 2003

Rates of oxidation in oxygen at 140°C. of natural rubber gum vulcanizates containing PBNA as inhibitor have been compared. They are a function of sulfur combined with the rubber, and only slightly affected by curing system for sulfur alone, TMTD sulfurless, and very high‐efficiency sulfenamide plus dithiocarbamate‐accelerated compositions. Addition of diphenylguanidine to simple sulfur vulcanizates causes much faster oxidation. No conclusions about oxidation mechanism can be drawn from rates of oxidation alone.
Thermal stability of elastomeric networks at high temperatures
Authors: Lee T. C. P. , Sperling L. H. , Tobolsky A. V.
Published: April 2003

Stress relaxation experiments were carried out in a dry nitrogen atmosphere on polydimethylsiloxane and an ethylene‐propylene terpolymer. Relaxation times much longer than expected were observed, and plots of In f(t)/f(0) versus time were linear in all cases.
Gelation and fusion of vinyl plastisols
Authors: Hoy K. L.
Published: April 2003

The gelation of vinyl plastisols at constant temperature has been found to follow the equation ln [(C − Ce)/(U − Ce)] = (− π2/a2)Dτ + ln (8/π2), where C is the resin phase concentration, Ce the equilibrium resin phase concentration, U the critical resin phase concentration, a the average particle size, D the diffusion constant, and τ the time required for the onsent of gelation. A light reflectance apparatus capable of measuring the gelation process is described. The effect that various resin–plasticizer parameters have on the gelation and fusion process is discussed. The light‐reflectance apparatus is also useful for estimating various resin and formulating parameters.
Molecular weight distribution in alkyd resins. Part III. Presence of microgel in alkyd resins
Authors: Solomon D. H. , Hopwood J. J.
Published: April 2003

Alkyd resins which have the same overall chemical composition and the same degree of polymerization have been prepared from synthetic mixtures of mono‐, di‐, and triglycerides of linoleic acid, glycerol, and phthalic anhydride. The properties of these resins differend significantly. Microgel particles are present in all resins, but the quantity and size of the gel particules is a function of the glyceride composition. The concept of microgel is used to explain the solution and film forming properties of these resins. Examination of a range of commercially available alkyd resins has shown that microgel particles are present where the functionality is greater than two.
Polymers for stabilization of colloidal cobalt particles
Authors: Hess Patrick H. , Parker P. Harold
Published: April 2003

A process for preparing metiallic cobalt particles of uniform size in the 10–1000 A. range is described. Dicobalt octacarbonyl is thermally decomposed in solutions of dispersant polymers to form stable colloids of discrete particles which are separated by polymer coatings. Variatin of polymer composition, molecular weight, and solvent used results in a variation of particle size and colloid stability. Preparation of single‐domain ferromagnetic cobalt particles with good magnetic properties depends on a very delicate balance between dispersant polymer, solvent, and the growing metal particle. A number of addition and condensation polymers can act as dispersants. The most successful are linear addition polymers of high molecular weight having relatively nonpolar backbones. Ideally, groups with a polarity greater than the backbone are attached at intervals of at least 100 but not more than 200 backbone atoms. The need for more polar groups and their spacing becomes les critical with increasing polymer molecular weight. The polymers appear to stabilize the metal particles by adsorption to form a thick fiml which separates the particles sufficiently to keep van der Walls energy of attraction below thermal energy levels. The solvent must solubilize the polymer coating sufficiently to allow the particle to grow. It should be less polar than the most polar group in the polymer and be chemically inert.
Emulsion polymerization of ethylene. V. Kinetics and mechanism
Authors: Stryker H. K. , Mantell G. J. , Helin A. F.
Published: April 2003

The solubility of ethylene was measured in water, water–tert‐butyl alcohol, water‐emulsifier, water‐tert‐butyl alcohol‐emulsifier, and water–tert‐butyl alcohol–emulsifier–polyethylene. The polymerization of ethylene in an emulsion system differs from that of other vinyl monomers in several ways: the rate of polymer formation is inversely proportional to the emulsifier concentration and to the number of particles, the molecular weight of the polymer increases as the particle size increases, the polymer contains bound emulsifier whose concentration depends inversely on the particle diameter. These peculiarities are attributed to a transfer reaction between polymer radicals and emulsifier adsorbed on the surface of the polymer particle. In the presence of a fatty‐acid soap, the transfer probably occurs primarily at the carbon α to the carboxyl group.
Melt flow and strength of branched styrene copolymers
Authors: Toggenburger R. , Newman S. , Trementozzi Q. A.
Published: April 2003

In order to assess the dependence of strength properties of glassy polymers upon the extent of branching, copolymers of poly(styrene–acrylonitrile) were prepared. By using principally three methods: (a) hydroperoxide intermediates, (b) hydroxyl radical initiation, and (c) incorporation of transfer monomers, branched polymers with high levels of branching with comb and dendritic type structures were generated. The tensile strength was found to be strongly correlatable with melt flow, and, in general, the branched copolymers were found to have the same tensile strength as linear polymers of the same melt index.
Polyurethane elastomers from post‐grafted polymer–polyol systems
Authors: Kuryla William C. , Whitman Robert D.
Published: April 2003

Certain homopolymer–polyol mixtures, after treatment with a free‐radical generating agent or ionizing radiation, will produce polyurethane elastomers of nearly twice the stiffness and tensile properties compared to control elastomers made with untreated mixtures. Specific examples of these mixtures include the homopolymers of acrylonitrile and vinyl chloride with a poly(oxypropyl) triol of about 3000 molecular weight as the polyol in each case. The marked improvement in the stiffness and tensile properties of elastomers made with the treated mixtures over those of the untreated controls indicates a grafting process occurring between the polyol and homopolymer upon the generation of free radicals. In the present work, grafting could occur by a chain‐transfer hydrogen‐abstraction mechanism, whereby a free‐radical site is generated on both the homopolymer and polyol chains. Coupling of these two free‐radical sites would thus result in the establishment of a polymer–polyol graft bond.
Thermal oxidation and photo‐oxidation of poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Kelleher P. G. , Jassie L. B. , Gesner B. D.
Published: April 2003

The thermal oxidation and photo‐oxidation of poly(2,6‐dimethyl‐1,4‐phenylene oxide) have been examined. Oxidation of the plastic results in the evolution of carbon dioxide, nitrogen and traces of hydrogen, the introduction of considerable crosslinking, and increased absorption in the hydroxyl and carbonyl regions of the infrared spectrum. A free‐radical oxidation mechanism is postulated.
Some mechanical properties of an epoxy resin system cured with multiple crosslinking agents
Authors: Jenkins Robert K.
Published: April 2003

Arbitrary cure times and glass transition temperatures are reported for an epoxy resin cocrosslinked by various weight fractions of hexamethylenediamine (HMDA) and m‐phenylenediamine (m‐PLDA). The glass transition temperatures of the epoxy resin systems studied yielded an excellent fit to an empirical equation developed by Dyvik for copolymers. The cure time parameters were found to be a linear function of the weight fractions of each crosslinking agent present. The mechanical properties of the epoxy resins were measured by an in situ dynamic modulus technique which employed the use of a resin‐coated metallic substrate.
Plasticizer diffusion as the rate‐determining step in dry blending of poly(vinyl chloride)
Authors: McKinney P. V.
Published: April 2003

Differential thermal analysis has been used to examine the process of dry blending of plasticizer and PVC. The rate of transformation of the glass transition from that of the polymer initially in the cold mix to the glass transition of the blend (blend Tg) has been examined at various temperatures from room temperature to above the polymer Tg. The dependence on temperature of this rate of transformation of the observed Tg is similar to the temperature dependence of the diffusion of plasticizer into PVC. It is concluded that diffusion of plasticizer into polymer particles is the rate‐determining step in the dry blending of PVC. It also appears that a single mechanism of diffusion is involved both below and above the glass transition of the polymer.
Characterization of photolyzed elastomers
Authors: Miller C. D.
Published: April 2003

The extent of photolysis of the surface of an elastomer may be characterized semiquantitatively by utilizing the physical model of a two‐ply stressed beam. A brief mathematical exposition is given. This permits a numerical estimate of the degree of chain scission and crosslinking occurring in the surface during photolysis.
Contact angle characteristics and breaking strength of paint plastic film
Authors: Tamai Y. , Tanaka S.
Published: April 2003

The advancing contact angle of water on plastic film coatings on metal was measured against both the air and the metal side surfaces after their being peeled off from the metal substrate. The plastic used was a methacrylate copolymer, and it was baked on cadmium, aluminum, nickel, iron, and gold. Contact angle for the air side was about 74° at 25°C. for all metals, but the values on the metal side differed considerably, ranging from 76° for gold to 50° for cadmium. At the same time the static breaking strengths of the same films were investigated by applying a knife‐edge vertically to the film with increasing load and measuring the weight at which the electric resistance through the film became zero. Increasing film thickness gave increasing strength, but further thickening made the film weaker with a tendency for crack formation. The film–metal combinations of larger contact angle difference generally also showed the higher breaking strength.
Polymer degradation. V. Changes in molecular weight distributions during sonic irradiation of polyisobutene
Authors: Porter Roger S. , Cantow Manfred J. R. , Johnson Julian F.
Published: April 2003

Gel permeation chromatography was used to follow changes in the molecular weight distribution of a polyisobutene, initial Mv = 466,000, during degradation induced by sonic irradiation. Seven samples taken at times of 200–163,500 sec. were studied. In general, a steady decrease in molecular weight was observed, although a bimodal distribution was present after 20,000 sec. irradiation. Various measures of inhomogeneity, Mw/Mn, U, etc., were examined. The function, σn/Mw, where σn is the standard deviation of the number distribution, is considered as a measure of the relative distribution. It is shown to be almost constant throughout the degradation.
Dynamic properties of PBNA–natural rubber vulcanizates
Authors: Payne A. R.
Published: April 2003

Some crystalline organic compounds containing a β‐naphthyl group stiffen rubbers considerably. This paper discusses the dynamic behavior of these systems when subjected to oscillatory strain of increasing amplitude. Modulus–strain amplitude plots similar to that in carbon black–natural rubber systems are obtained. The implication of these results to reinforcement theory is discussed.
Effect of molecular weight distribution on viscosity of polymeric fluids
Authors: Middleman Stanley
Published: April 2003

Bueche's theory is modified to account for the effect of polydispersity on viscosity of polymeric fluids. Results indicate that the ratio of weight‐average to number‐average molecular weight, 〈Mw/Mn〉, though a common measure of polydispersity, is insufficient to account completely for the effect of polydispersity on viscosity.
Synthèse et caractérisation de copolymères cellulose–poly(méthacrylate de méthyle): Greffage par le système acide de Caro–ion Fe3+
Authors: Miléo Jean‐Claude , Nicolas Louis
Published: April 2003

Le méthacrylate de méthyle a été greffé a la cellulose en utilisant l'acide de Caro en présence de sel ferrique comme initiateur. L'effet de la durée du greffage, de la concentration en ions ferriques et du rapport cellulose‐monomere sur le pourcentage du greffage a été étudié. Au départ d'études du mécanisme de réaction, a des composés modèles, on a admis que les greffages ne se passent pas via les unités glycols 1,2 ou à l'unité hémiacétalique ' la fin de la molécule cellulosique. Des dégradations concommittantes de la cellulose en cours de la copolymérisation greffée a été examinée. Une relation linéaire entre le pourcentage de greffage et le nombre de chaînes cellulosiques briées par hydrolyse a été trouvée, d'où il semble que la structure du copolymère greffé était plutôt du type séquencé. La structure du copolymere greffé a aussi été étudiée par détermination des poids moléculaires des branches de polyméthacrylate de méthyle greffées apres hydrolyse de la chaîne cellulosique. Dans tous les cas, indépendamment des conditions de réaction, les poids moléculaires des ramifications greffées étaient tres élevés et leur nombre faible. Le nombre de branches greffées par chaîne cellulosique a été calculé au départ du pourcentage de greffage, des poids moléculaires des branches de polyméthacrylate et des poids moléculaires de la chaîne cellulosique. Ce nombre a été comparé au nombre de liens cellulosiques brisés en cours de greffage.
Graft copolymers of starch. III. Copolymerization of gelatinized wheat starch with acrylonitrile. Influence of chain modifiers on copolymer composition
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E.
Published: April 2003

A study was made of the influence of selected chain modifiers on both the molecular weight of grafted polyacrylonitrile and the grafting frequency of the starch–polyacrylo‐nitrile graft copolymer. Gelatinized wheat starch was used with ceric ammonium nitrate as the initiator. The organic chain modifiers investigated were ethyl mercaptan, 1‐dodecanethiol, methyl ethyl ketone, acetaldehyde, and chloroform. Sodium chromate, cupric bromide, cupric nitrate, cupric acetate, and cupric chloride were also tested as chain modifiers. In the presence of cupric chloride, there was a tenfold reduction in the molecular weight of grafted polyacrylonitrile; however, fewer chains were grafted to the starch backbone than were observed without cupric chloride.
Evaluation of polyglycidyl esters as cryogenic adhesives
Authors: Sandler Stanley R.
Published: April 2003

Polyglycidyl esters of aromatic polycarboxylic acids were evaluated as adhesives for aluminum over the temperature range −453 to +400°F. The esters were cured either with amines or anhydrides. Cyclopentanetetracarboxylic acid dianhydride was found to be a superior curing agent and gave adhesives with tensile shear strengths in excess of 1000 psi at 400°F.
Investigation of conditions of spherulite formation in mixtures of crystalline and amorphous polymers
Authors: Bartoň J. , Rak J.
Published: April 2003

The supermolecular structure of mixtures of crystalline polymers (low pressure and high pressure polyethylene, isotactic polypropylene) with an amorphous polymer (atactic polypropylene) from the point of view of the influence of the amorphous component on the morphology of the crystalline component has been investigated. The criterion of changes in the morphological state of larger supermolecular formations was the microscopic image of the samples obtained with an optical microscope, both between crossed nicols and in phase contrast. It has been established that the formation of typical spherulites depends on the amount of admixture of the amorphous polymer and also on the treatment of the samples. Upon crystallization in presence of a small amount of solvent (p‐xylene), formation of typical spherulites of the crystalline component of the mixture can be observed while the same mixture in case of evaporation of the solvent presents a granulated refractive structure without typical spherulites, regardless of the rate of cooling. The probable role of the solvent is to facilitate mutual segregation of the microphases of both polymers in consequence of decrease in viscosity of the mixture. It has been further shown that even after briefly heating the mixture to a temperature of 220°C., before crystallization, spherulites do not form; on the contrary, spherulites originally present disappear and a structure consisting of smaller refractive formations of crystalline polymer is obtained. The formation of this structure, emerging after destruction of spherulites, might be attributed to an increase of interpenetration of both polymers and to an increase of the contact surfaces between components of the mixture.
Effect of environmental hydrogen pressure on the hydrogen yield from x‐irradiated polyethylenes
Authors: Hill Otto H. , Lightfoot R. Pat
Published: April 2003

An experimental assembly incorporating a capacitance‐type, differential pressure transducer, which provides resolutions of 3 × 10−4 torr at pressures extending to 30 torr, has been employed to monitor the effect of hydrogen environmental pressure on the hydrogen yield from x‐irradiated polyethylenes. Contrary to the observations of previous investigators, the hydrogen yield is found to be independent of hydrogen environmental pressures extending over the critical range up to at least 30 torr. It is demonstrated that neglecting the temperature and density gradients inherent in closed‐volume irradiation assemblies employing cryogenic traps to separate liberated gases into condensable and noncondensable fractions may lead to erroneous conclusions with respect to gas yields arising from the irradiation of materials. A homogeneous, variable‐plate separation ion chamber consisting of a polyethylene body and utilizing flowing ethylene as the cavity gas was employed to obtain total volatile G values of 3.6 ± 0.4, 3.8 ± 0.4, and 4.0 ± 0.4 molecules/100 e.v., for Marlex 6002, Dow Ziegler (Q 917.5), and DuPont A‐1410 polyethylenes, respectively. A hydrogen contribution of approximately 98 mole‐% was obtained with this experimental method.
Silane polysulfide polymers as solid composite propellant binders
Authors: Schwarz William W. , Lowrey R. Dean
Published: April 2003

Two mercaptosilane monomers were prepared and polymerized by oxidation to yield mercaptan functional silane polysulfide polymers. The mercaptosilane monomers were of the general formula, [HS(CH2)x]2SiY2, where x = 3 and Y = Et or Me. These monomers were prepared by the addition of thiolacetic to diallyldialkylsilanes. The dithioldiacetate that resulted from the addition reaction was hydrolyzed in alcoholic NaOH yielding the dimercaptan. Polymerization of the dimercaptan was accomplished with peroxides, iodine, or sulfur, yielding polymers of a molecular weight of approximately 1200. These polymers were cured to solid elastomers with mild oxidizing agents. The mercaptan monomers were also redistributed with diethylformal polysulfide polymers, which were then cured to solid elastomers with mild oxidizing agents. The redistributed silane–diethylformal polymers were used to make composite solid propellants. A 50% increase in propellant burning rate and a 16°C. lowering of the glass transition temperature were found when the redistributed polymer was used in place of diethylformal polymers as a propellant binder. Experimental procedures are given.
Molecular weight distribution in disulfide polymers
Authors: Shlyakhter R. A. , Ehrenburg E. G. , Nassonowa T. P. , Piskarewa E. P.
Published: April 2003

The published data on molecular weight distribution in polysulfide are rather contradictory and cannot be correlated with the concept of the existence of thiol–disulfide interchange in these polymers. In the present work the viscosity and molecular weights of liquid thiokols have been investigated (the number‐average molecular weight by iodometric titration and by ebulliometry and the weight‐average molecular weight by the light‐scattering method). When measuring the light scattering in Thiokol Solutions a considerable depolarization of the scattered light was observed. This fact must be taken into account in the molecular weight determination. It has been established that in polydisulfides with thiol endgroups thiol–disulfide interchange reactions take place not only during the synthesis, but also in the polymer itself (in bulk). These reactions lead to the formation of polymers with an equilibrium molecular weight distribution. A relation of log η = f(Mw)½ has been found that can be used in determining the weight‐average molecular weight of liquid Thiokols.
Viscoelastic investigation on the cure of unsaturated polyester coatings
Authors: Imai T.
Published: April 2003

The change of the viscoelastic behavior of an unsaturated polyester resin during curing was followed by a vibrometric technique, while the portion converted to gel in applied films was also determined by means of extraction with a solvent. Some relationship between the viscoelastic properties and the amount gelling has been found to exist. The dependency of the curing rate of polyesters on the concentration of initiator as well as accelerator seemed not to be unity. A marked delay in cure has been observed in the region of low concentrations of initiator and accelerator.
Elastomers from castor oil
Authors: Ghatge N. D. , Phadke V. B.
Published: April 2003

Castor oil has been used to prepare millable elastomers by using 2,4‐toluene diisocyanate, 4,4′‐diphenylmethane diisocyanate, and 1,5‐naphthalene diisocyanate, respectively. These elastomers are vulcanized with sulfur and 4,4′‐diphenylmethane diisocyanate separately by using the standard methods of rubber technology, and the properties of these vulcanizates are reported.
Mathematical analysis of gel permeation chromatography data
Authors: Smith W. N.
Published: April 2003

The purpose of this paper is to show how a theoretical molecular weight distribution can be found which would result in a given gel permeation chromatogram. Also, to show how the method can be applied to blending problems where one desires a given molecular weight distribution.
Crosslinking of silk fibroin by aqueous peroxydisulfate
Authors: Needles H. L.
Published: April 2003

Silk fibroin is crosslinked by 0.1–1.0M ammonium peroxydisulfate at 70°C. or at 40°C. in the presence of silver ion. Induced decomposition of peroxydisulfate in the presence of fibroin is observed. Methylation of tyrosine in fibroin does not slow attack by peroxydisulfate, but crosslinking of the fibroin is prevented. Modification of tryptophan with α‐bromo‐5‐nitro‐2‐cresol does not prevent crosslinking by peroxydisulfate, however. The nature and sites of crosslinking in fibroin are suggested in light of physical and chemical data, amino acid analyses of crosslinked and control fibroins, and the known mode of decomposition of peroxydisulfate.
Study of the nitration of methyl cellulose
Authors: Bobinski Jack , Carignan Yvon P.
Published: April 2003

A two‐step procedure for the preparation of methyl cellulose nitrate is described. The heterogeneity of the methylation step is reflected in the nonuniformity of the products obtained by nitration with either 98% nitric acid or a solution of 98% nitric acid in methylene chloride. On the basis of the experimental data it is calculated that methyl cellulose having a minimum degree of substitution of 1.8 is required for the preparation of a uniformly substituted methyl cellulose nitrate.