bluuebunny/crossref_metadata_2025 huggingface dataset:
A high hydroxyl group content found in high molecular weight fractions of poly(oxyethylene glycol)
Authors: Delmas G.
Published: April 2003

The results of a fractionation of high molecular weight poly(oxyethylene glycol) with the mixture benzene—isooctane are presented. The fractions are characterized by gel permeation chromatography (GPC), infrared spectroscopy, viscometry, and dialysis. A high hydroxyl content was found for the higher fractions, which is not compatible with a linear polyoxyethylene glycol molecule with hydroxyl endgroups. The presence of hydroxyl groups on the chain is improbable. The dialysis of the higher fractions in CCl4 and toluene shows that a surprising amount passes through the dialysis bag. The possibility of degradation of the polymer is considered. However, GPC analysis of the products of the dialysis suggest that the high molecular weight is made up of aggregates of middle‐sized molecules and low molecular weight ones, held together by hydrogen bonding between hydroxyl and ether groups. Some results of a fractionation in water with the lower critical solubility temperature at 99°C. are given.
Calorimetric behavior of methacrylic polymers
Authors: Griskey Richard G. , Hubbell Douglas O.
Published: April 2003

Specific heats for poly(methyl methacrylate), poly(diethylaminoethyl methacrylate), poly(cyclohexyl methacrylate), poly(allyl methacrylate), and poly(ethyl acrylate) were measured from 120 to 300°C. with a drop calorimeter. It was found that existing solid‐state theories and equations were unable to correlate the data. The reason advanced was that such theories were developed for crystalline materials, which differed greatly from the amorphous polymers of the present work. A more successful approach was to use a correlation technique originally developed for organic liquids.
Thermal degradation of poly(phenylene sulfide) and perfluoropoly(phenylene sulfide)
Authors: Christopher N. S. J. , Cotter J. L. , Knight G. J. , Wright W. W.
Published: April 2003

The thermal and oxidative degradation of poly(phenylene sulfide) and perfluoropoly(phenylene sulfide) have been studied by a weight‐loss method. The products of breakdown in vacuum have also been analyzed. The poly(phenylene sulfide) is more thermally stable in inert and oxidizing atmospheres than the fully fluorinated analog. The breakdown products can be accounted for by chain scission and transfer reactions. The formation of a large proportion of residue implies that crosslinking reactions play an important part in the degradation.
A dynamic mechanical study of the effect of chemical variations on the internal mobility of linear epoxy resins (polyhydroxyethers)
Authors: Van Hoorn H.
Published: April 2003

A series of polyhydroxyethers prepared from various bisphenols and their diglycidyl ethers has been investigated for dynamic mechanical behavior in a temperature range from −180°C. up to their glass‐rubber transition region, employing a torsion pendulum method for frequencies of about 0.1 hz and a vibrating‐reed method for frequencies of about 100 hz. Glass‐rubber transition temperatures ranged from 85 to 170°C. and are interpreted in terms of polarity, segment bulkiness, and packing capability of the polymer molecules. In most cases the activation energy of this transition was found to be extremely high, of the order of 500 kcal./mole. Fair consistency is found regarding the role played by methyl or chlorine substitution of the bisphenol rings, increasing bulkiness and steric hindrance, but reducing polar interaction. At least one and, in some cases, two secondary transitions were found well below the glass‐rubber transition region. One is ascribed to a change in mobility of the glyceryl ether segments common to all nonesterified polymers of the series. While this is in general agreement with the findings of other authors, we found a spread in transition temperature values (−70 to −102°C. at ≈ 1 hz) and activation energies which can be related to the detailed chemical structure of these polymers. With methyl substitution of the bisphenol rings of the highly polar polymers symmetry seems to be an important factor. In addition, another secondary transition appeared, which we ascribe to an onset of ring rotation.
Determination of polyolefin film properties from refractive index measurements. II. Birefringence
Authors: Schael George W.
Published: April 2003

The use of refractive index data for studying changes in oriented polyolefin films has been demonstrated. Application of this technique to oriented polypropylene and polyethylene films showed that the birefringence is a linear function of the refractive index in the direction of maximum orientation. By utilizing refractive index, density, and crystallinity data the crystalline refractive indices nc and (na + nb)/2 and polarizabilities α∥ and α⊥ could be estimated for polypropylene and polyethylene.
The effect of a low‐viscosity swelling liquid on the tensile strength of rubber
Authors: Grosch K. A.
Published: April 2003

The paper examines the effect of swelling on a number of different gum rubbers and rubbers filled with different types and concentrations of black. The observed decrease in strength with decreasing rubber fraction Vr (increasing swelling ratio) is, in the case of gum rubbers, associated with a decrease in internal friction. The incorporation of a black filler is shown to increase strength by hydrodynamic stiffening and by an increase in internal friction of the rubber network, and a simple reduction scheme of the data shows a close analogy between the strength as a function of Vr and the dynamic modulus of a rubber solution as a function of concentration. The results lead to a failure criterion, which describes the energy density at break as a simple function of the hysteresis near break.
Brabender Plasticorder studies of the process of crosslinking polyethylene
Authors: Narkis Moshe , Miltz Joseph
Published: April 2003

The process of crosslinking unfilled thermoplastic polyethylene has been followed with the aid of the Brabender Plasticorder. It is shown that extrusion conditions without any significant scorching can be obtained with this instrument. The maximum torque in the plastograms is discussed and shown not to be a correct criterion of crosslinking efficiency, since its value is influenced by a process of shear grinding of the crosslinked polymer. The crosslinking is further continued after the maximum torque is reached. The dependence of gel content on peroxide concentration is given.
Dynamic mechanical properties of some polymeric acid zinc salts
Authors: Fields J. E. , Nielsen L. E.
Published: April 2003

Mechanical properties, shear modulus, and damping of a series of polyacid divalent metal salts have been correlated with the degree of salt formation. The salts were prepared in situ by molding mixed powders of 94/6 acrylic acid–2‐ethylhexyl acrylate and zinc oxide at temperatures of 200–300°C. and pressures of 5,000–10,000 psi. Zinc oxide consumption was followed by x‐ray techniques. Compositions contained 25–200% of theory metal oxide as charged. Excesses, over theory, of metal oxide were shown to lead to the formation of substantial amounts of pendent half‐salts which are high damping and have temperature‐sensitive shear moduli. Only complete reaction as the di‐salt, at 300°C. and 10,000 psi, leads to low damping products with temperature‐insensitive high modulus. The modulus increase due to ionic bonding as the di‐salt, over that expected from classical filler action alone, ranged from 40 to 80%, depending upon the theory chosen to calculate filler action. The pendent half‐salt gives much smaller moduli increases and unreacted metal oxide appears to act as classical filler in an intertangled complex polyelectrolyte salt matrix. The modulus of the di‐salt was found to be 6–7 times higher than moduli for normal organic rigid polymers.
Flammability and thermal stability of isocyanate‐based polymers
Authors: Backus J. K. , Bernard D. L. , Darr W. C. , Saunders J. H.
Published: April 2003

A series of model polyurethanes and polyureas, a polyamide, and a polyimide were prepared by reacting 4,4′‐diphenylmethane diisocyanate or polyisocyanates having similar polybenzyl structures with aliphatic or aromatic coreactants. Thermogravimetric analyses indicated that the flammability of the polymers was related to the formation of volatile flammable products during early stages of decomposition. Determinations of the heat evolved during differential thermal analyses and of the thermodynamic heats of combustion suggested that the extent and rate of reaction were among the important factors governing flame propagation. Flame‐resistant polymers were prepared by use of structural elements which were thermally stable and nonvolatile or which formed nonflammable decomposition products.
Reactions of carbon black. Part I. Nonthixotropic carbon black compositions
Authors: Takashina Naomitsu , Aida Tetsuo
Published: April 2003

The solution polymerization of butyl acrylate in the presence of a furnace black was found to produce a stable dispersion of carbon black which showed Newtonian flow, while the mixture prepared by mixing the same carbon black into a solution of poly(butyl acrylate) homopolymer had a large degree of thixotropy. A marked change in the viscosity of the reaction mixture was also observed at an early stage of polymerization when the initial mixture which was a moist mass with no fluidity, turned to a fluid easily stirred. The change in viscosity and the transition in flow behavior were carefully followed with a rotary cylinder type viscometer. The non‐Newtonian initial mixture was found to turn to a Newtonian fluid at low conversion of the monomer. Beside the adsorption of the homopolymer onto the surface of carbon black particles, which would occur also in mechanical mixing, the change in the flow behavior was estimated to be caused by the change in the shape and the size of the dispersed carbon black particles due to the change in the condition of the surface of the particles by which growing polymer radicals, as well as initiator radicals, were captured.
Growth, morphology, and reinforcement potential of low molecular weight crystals in amorphous polymeric matrices
Authors: Joseph Jacques R. , Kardos John L. , Nielsen Lawrence E.
Published: April 2003

The technique of in situ crystallization of low molecular weight organic compounds from amorphous polymers was evaluated as a method of fabricating composite materials. Two workable systems, styrene–acrylonitrile copolymer (SAN)–acetanilide and SAN–anthracene, were found and their phase diagrams determined. In both systems kinetic studies revealed that the maximum crystallization rate takes place at large degrees of supercooling and that below these temperatures the mechanism is diffusion‐controlled. The temperature‐dependent crystal morphologies were characterized with electron microscopy, which showed three distinctly different morphologies for both systems. From dynamic mechanical measurements, it appears that the elastic moduli of organic crystals are about the same as those of organic polymers in the glassy state, and that relatively little reinforcement took place under the particular crystallization conditions employed.
The chemistry of sulfur curing. Part II. Kinetics of vulcanization of an EPDM elastomer accelerated by tetramethylthiuram monosulfide and disulfide
Authors: Wolfe James R.
Published: April 2003

The induction periods and maximum cure rates of an EPDM gum rubber were determined by using the Monsanto oscillating disk rheometer and correlated against the initial concentrations of curing ingredients. Sulfur curing systems accelerated by TMTM and TMTD were used. The maximum cure rates of the TMTM‐accelerated and the TMTD‐accelerated EPDM terpolymer compounds differed significantly only at low sulfur concentrations where the TMTM‐accelerated compounds had slower maximum cure rates. Above approximately the 1% concentration level, TMTM and TMTD were found increasingly to retard the maximum cure rates of the EPDM terpolymer compounds as the initial concentrations of the thiuram accelerators were increased. The maximum cure rates of the TMTM‐and TMTD‐accelerated terpolymer compounds were found to be variable order in initial accelerator concentration, second‐order in initial cure site concentration, approximately half‐order in initial sulfur concentration above 0.3% sulfur, and of a positive variable order in initial zinc oxide concentration.
Fracture behavior of rubber‐modified thermoplastics after aging
Authors: Bucknall C. B. , Street D. G.
Published: April 2003

Experiments show that the effects of outdoor aging on rubber‐modified thermoplastics can be reproduced by laminating a layer of a glassy polymer onto the surface of unaged specimens. This technique is used to study the effects of fracture temperature, specimen geometry, and polymer composition on the impact strength of aged HIPS and ABS. Aging reduces the energy of crack initiation, so that the impact strength is determined by the crack‐propagation energy, which is in turn governed by the nature and concentration of the rubber and by the fracture temperature.
Gel in polyethylene
Authors: Mortimer George A. , Wade Dennis E. , Arnold Lloyd C.
Published: April 2003

A quantitative test for the presence of gel (insoluble polymer) in polyethylene is described. A number of experiments were performed by using the test and on the polymers separated by the test. It is concluded that gel is crosslinked polyethylene in the form of discrete particles of significant size, the large ones, probably weighing up to at least 10 mg. Some crosslinks are broken by treatment with solvents above 200°C., and much of the gel is thus rendered permanently soluble. Gel is also insoluble in the reaction medium in which it is produced. Thus, even if the ethylene–polyethylene phase relationships would predict a homogeneous reaction, the reaction must be hetero‐geneous if gel is present. Therefore, kinetic treatments of ethylene polymerization which do not consider phase separation when gel is found in the reaction product are oversimplified.
Variation of refractive index of polystyrene with molecular weight: Effect on the determination of molecular weight distributions
Authors: Barrall E. M. , Cantow M. J. R. , Johnson J. F.
Published: April 2003

Sensitive refractive index measurements on solutions have indicated that the narrow molecular weight polystyrene samples prepared by the Mellon Institute method exhibit a small systematic molecular weight–refractive index dependence up to 300,000 and higher. This upper limit is higher than had previously been suggested. Sensible consistency is generally assumed above a few thousand molecular weight. The effect on this molecular weight–refractive index dependence on gel permeation chromatography and light‐scattering molecular weight measurements on polystyrene standards is illustrated.
Influence of cohesive forces on the glass transition temperatures of polymers
Authors: Lee W. A. , Sewell J. H.
Published: April 2003

The relationship between cohesive energy (c.e.) or cohesive energy density (c.e.d.) and the glass transition tenperature (Tg) of polymers has been re‐examined on the basis of literature data. For polymers with Tg above 25°C., there is no correlation between published or calculated values of c.e. or c.e.d. and Tg. However, for the rest of the polymers there is a linear relationship between c.e.d. and Tg, and a broad relationship between c.e. and Tg. These results imply that c.e.d. is the regulating, though not the only, factor in determining Tg's up to values of approximately 25°C.
ESR study of reactions of cellulose with ·OH generated by Fe+2/H2O2
Authors: Arthur Jett C. , Hinojosa Oscar , Bains M. S.
Published: April 2003

It was demonstrated by ESR spectroscopy that the Fe+2/H2O2 system gave a reactive species which generated an ESR triplet spectrum or sorbitol similar to that generated by hydroxyl radicals from the Ti+3/H3O2 system. An ESR spectrum was obtained for the hydroxyl radicals generated by the latter system. However, the lifetime of hydroxyl radicals, generated by the Fe+2/H2O2 system, was apparently very short, and an ESR spectrum for the hydroxyl radicals, generated by this system, was not observed. The Fe+2/H2O2 system also generated triplet spectra with cotton cellulose I, cotton cellulose II, and microcrystalline cellulose, suggesting that a hydrogen atom had been abstracted from the hydroxyl group on carbon C6, or possibly the hydrogen atom on carbon C5. The ESR spectrum generated on microcrystalline cellulose was less intense than those generated on cellulose I and II. On initiation of graft polymerization of the activated cellulose with acrylonitrile, the triplet spectrum disappeared and was replaced by two strong singlet spectra. One of the singlet spectra was likely generated on carbon C1 or C4 on depolymerization of the cellulose molecule, and the other was probably generated on the end of the growing polyacrylonitrile molecular chain. The absence of a triplet spectrum gave direct evidence for the order in which the acrylonitrile monomer was being grafted onto the cellulose molecule. The mechanisms proposed by Haber and Weiss for the reactions generated in the Fe+2/H2O2 system were generally supported.
Compressibility and other thermodynamic properties of polymers
Authors: Surland C. C.
Published: April 2003

Experimental methods for estimating the thermodynamic derivative, (∂T/∂P)s, of both liquids and solids are described and discussed. The adiabatic heating parameter is shown to be useful, in conjunction with other more commonly measured properties, for estimating the heat capacity, Cp = T(∂S/∂T)p, and the internal pressure, Pi = (∂U/∂V)T. The principles for applying adiabatic heating measurements to the characterization of polymers are given with data for several common liquids and for filled and unfilled polyurethane rubbers.
Mechanochemical degradation of an EPDM polymer
Authors: Baranwal Krishna
Published: April 2003

A mill‐mastication study of an EPDM polymer (DuPont, Nordel 1070) was conducted in the mill‐roll temperature range of 68–480°F. The extent of degradation was determined by dilute‐solution viscosity measurements. The role of oxygen in the polymer mastication was followed by infrared spectroscopy. The breakdown of the EPDM polymer on the mill is minimum in the temperature range of 185–315°F. Up to 315°F. the increase in temperature leads to a decreased amount of degradation. During cold mastication mechanical breakdown occurs. The use of a free‐radical acceptor shows that this type of breakdown is caused by the mechanical rupture of CC bonds in the polymer chain. At and above 350°F. thermooxidative degradation becomes dominant, the polymer degrading drastically, and the higher the temperature, the greater the extent of degradation for the same period of mastication. Infrared spectroscopy shows that hot mastication results in decreased double‐bond concentration and increased amounts of carbonyl and, possibly, anhydride and lactone groups. Of the carbonyl groups formed 30% are due to the oxidation of double bonds in terpolymer and 70% to the oxidation of the main chain. A mechanism is proposed to account for these observations.
Photopolymerization of hydroxypropyl acrylate and tetraethylene glycol dimethacrylate initiated by uranyl ion
Authors: Higgins Cecil E. , Baldwin Willis H.
Published: April 2003

Uranyl nitrate, acetate, sulfate, and dibutyl phosphate were used in solution for the photoinitiation of homopolymerization and copolymerization of hydroxypropyl acrylate and tetraethylene glycol dimethacrylate. Solvents used included water, water‐ethylene glycol mixtures, and dimethylformamide. Polymer yields in excess of 90% can readily be obtained by exposing solutions containing 0.014M UO22+ to light from a tungsten bulb for 1 hr. The rigidity of the polymers varied directly, the affinity for water in‐versely, with the concentration of tetraethylene glycol dimethacrylate in the monomer mixture. Poly(hydroxypropy1 acrylate) contained 52% water and poly(tetraethy1ene glycol dimethacrylate) 34% water, a t equilibrium.
Cleavage behavior of bonds made with adherends capable of plastic yield
Authors: Duke A. J. , Stanbridge R. P.
Published: April 2003

The failure behavior of adhesive joints under cleavage stresses depends upon the thickness of the adherend. With thick, rigid adherends failure occurs by rapidly propagated adhesive rupture. Thinner adherends can exhibit plastic flexural yield, the subsequent adhesive failure then being progressive and strain‐limited, and occurring only in the region of bond directly adjacent to the yielding adherend. A fairly sharp discontinuity between these two types of behavior occurs over a small range of adherend thicknessT. Work to rupture can differ by more than an order of magnitude, for otherwise identical joints havingTabove or below the transitional range (aroundTc). ForT>Tcthe applied loadPcausing rupture is proportional toT1.5while the moment arm remains constant, as predicted by Yurenka. ForT < Tcthe turning moment during failure is proportional toT2and is substantially independent of the nature of the adhesive. Empirically, the radius of the yielded adherend after failure is proportional toT. The manner of interaction of various adhesive mechanical properties in definingPin the two ranges and, thereby,Tc, are related to this and other empirical correlations. The initial free moment arm in the joint,L, determines the stability of peel at initiation of adhesive rupture. ReducingLleads ultimately to instability. The change of controlling factors asL→ 0 is discussed.
Epoxy polymers. IV. Impact‐induced voltage generation
Authors: Cuthrell R. E.
Published: April 2003

Mechanical‐stress‐induced voltage or current in epoxy polymers appears to be a function of the state of order of dipoles in the surface layer. The sign and magnitude of the voltage is correlated with the surface layer characteristics. The time required for the impact voltage to decay to its original value appears to correlate with dipole orientation relaxation times obtained by dielectric constant and loss measurements.
Characterization of branched polyethylene fractions from the elution column
Authors: Schneider N. S. , Traskos R. T. , Hoffman A. S.
Published: April 2003

Fractions from several elution column runs on samples of up to 6 g. of a well‐characterized high‐pressure polyethylene were analyzed by absolute molecular weight methods and several other techniques. The Mn and Mw integral distribution curves are free from any reversal, as was the viscosity distribution curve. Fractions with Mw as high as 8 × 106 were recovered, more than 20 times higher than the original sample's Mw. The polydispersity of the fractions increases from Mw/Mn = 1.5 or less in the low molecular weight fractions to a nearly constant value of 4.5–5.0 in fractions above 60% cumulative sample weight. Nonetheless, refractionation on the elution column shows that the fractions are narrowly distributed in terms of solubility, while GPC analysis reveals that the fractions have an extremely narrow size distribution. It is concluded from the combined results that long‐chain branching plays an important role in determining the equilibrium solubility and, further, that long‐chain branching increases the polymer solubility. Sample calculations are provided, which illustrate the effect of fraction polydispersity on calculated original sample molecular weights and the fit of the fractionation results to several model distribution functions.
The solubility parameter of polypropylene
Authors: Michaels Alan S. , Vieth Wolf R. , Alcalay Haim H.
Published: April 2003

Solubility parameter values for polypropylene as reported in the literature cover a rather broad span, ranging from 7.9 to 9.4 (cal./cm.3)1/2. This communication suggests the approximate value 8.2. This value is based on the swelling and dissolution characteristics of polypropylene films in various organic liquids. A calculated value of 8.1, obtained by Small's method, compares well with the experimentally determined value.
Studies of the fractionation of polyoxymethylene
Authors: Kobyashi Eiichi , Okamura Seizo , Signer Rudolf
Published: April 2003

The precipitation of polyoxymethylene in p‐chlorophenol solution and the molecular weight fractionation of the polymer by mechanical agitation were investigated. The agitation of the solution was carried out in a glass vessel with a stirrer, usually at 60°C. After agitation for several minutes a fibrous polymer precipitated. High molecular weight polymer precipitated around the stirrer in an early stage, and therefore the method might be applied to the fractionation of polyoxymethylene. The method was applied to the fractionation of polyoxymethylene prepared in a solid‐state and in a solution polymerization of trioxane, catalyzed by BF3.OEt2. It was found that the polymer from the solid state contained a small amount of extremely high molecular weight fraction, and that obtained from the solution had a relatively narrow distribution of molecular weight.
The polymerization and copolymerization of nitroalkyl acrylates and nitroalkyl methacrylates
Authors: Takahashi Kunihiro , Abe Satsuki , Namba Keiho
Published: April 2003

Nitroalkyl acrylates and methacrylates involving some new compounds were prepared. The homopolymerization of these monomers in toluene and their copolymerization with styrene in acetone were carried out with azobisisobutyronitrile as initiator. The rate of polymerization of the nitroalkyl acrylates showed a correlation with the number of nitro groups situated on the ester side chain. The apparent activation energies of the polymerization were found to be 22.0–27.5 kcal./mole for the nitroalkyl acrylates and about 11.5–13.0 kcal./mole for the nitroalkyl methacrylates. From the reactivity ratios and Q‐e values of the copolymerization the following information was obtained. The copolymerization behavior of nitroalkyl acrylates and methacrylates showed an alternating tendency, and these monomers belong to the conjugative monomer groups. On the reactivities of these monomers, the polarity of vinyl group was affected a little by nitro group of ester bond side, and the resonance affected little. These monomers were crosslinked with 2‐methyl‐2‐nitro‐1,3‐propylene diacrylate. Some of the polymers showed marked improvement in the physical properties of elastomers.
Chlorination of polyesters
Authors: Jackson W. J. , Caldwell J. R. , Perry K. P.
Published: April 2003

By photochemical chlorination chlorine was substituted on the gem‐dimethyl groups of the polyterephthalate and polycarbonate of 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol, the polyterephthalate of 2,2‐dimethyl‐1,3‐propanediol, and the polycarbonate of 4,4′‐isopropylidenediphenol (bisphenol A). The factors affecting polyester degradation, the efficiency of chlorination, and the degree of chlorination were investigated, and the effects of chlorine content on the solubility, flammability, density, hydrolytic stability, thermal stability, tensile properties, electrical properties, and heat‐distortion temperatures of cast films were determined. The chlorinated polyesters of particular interest, because of their properties, are the polycarbonates of 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol and bisphenol A.
Thermal stability of modified poly(vinyl chloride) by TGA
Authors: Matlack J. D. , Metzger A. P.
Published: April 2003

The stability of poly(vinyl chloride), as measured by thermogravimetric analysis, is significantly different from that of other thermoplastics. It is shown that the onset of weight loss can be correlated with the development of color in a processed resin. It is further shown that the ingredients within a rigid polyvinyl chloride compound drastically alter its thermal behavior. The effect of lubricant and stabilizer on the degradation of poly(vinyl chloride) is stressed.
Poly(norbornene): Tensile and dynamic‐mechanical properties
Authors: Galperin I. , Carter J. H. , Hein P. R.
Published: April 2003

The tensile and dynamic mechanical properties of poly(norbornene), prepared through ring‐opening polymerization, were studied. Tensile strength and extensibility increased, while Young's modulus decreased with increasing molecular weight and with increasing content of trans relative to cis unsaturation. The damping factor Delta; was dependent on molecular weight only for the lower molecular weight samples. The out‐of‐phase modulus E″ and the damping factor decreased as the trans/cis ratio increased.
Some effects of ionizing radiation on a polyhydroxyether
Authors: Golden J. H. , Hammant B. L. , Hazell E. A.
Published: April 2003

The behavior of the polyhydroxyether derived from bisphenol A and epichlorohydrin on exposure to electron irradiation (0–500 Mrads) in vacuum has been investigated. The polymer underwent chain scission, G = 0.20 (scission per 100 e. v.), with no evidence of crosslinking. Degradation was accompanied by the loss of H2 together with smaller quantities of CO, CO2, and CH4. Spectroscopic studies are reported, and a mechanism of degradation is proposed. The tensile yield stress and fracture energy of molded specimens were also examined, and changes in these properties as functions of radiation dose and molecular weight are discussed.
Properties of solutions of poly‐N‐vinylcaprolactam
Authors: Solomon O. F. , Corciovei M. , Ciută I. , Boghină C.
Published: April 2003

The properties of poly‐N‐vinylcaprolactam organic and aqueous solutions were studied. Toluene solutions present an increasing [η] from 10 to 40°C. Aqueous solutions present a very accentuated diminishing of [η] from 10 to 30°C. Above 30°C. The polymer precipitates from its aqueous solutions. The precipitation temperature does not depend on the concentration but on the molecular weight of the polymer. Some acid and basic agents have a marked influence on [η] and the precipitation temperature of the aqueous solutions.
A modified copolymerization equation for three‐component systems
Authors: Kumar A.
Published: April 2003

A modified copolymerization equation substantiated by experimental evidence has been proposed for tricomponent systems.
Chain reaction mechanism of cellulose pyrolysis
Authors: Chatterjee Pronoy K.
Published: April 2003

Chatterjee and Conrad1 studied the kinetics of pyrolysis of cotton cellulose in the temperature range 270–310°C and proposed a chain reaction mechanism. Lipska and Parker8 studied the pyrolysis of the α‐cellulose in the temperature range 250–300°C and interpreted the kinetic data differently. Both articles were published almost simultaneously. In this paper Lipska and Parker's complete data have been again analyzed and reinterpreted in light of the chain reaction mechanism. The energies of activation for initiation and propagation steps of the cellulose decomposition reaction are discussed.
Determination of degree of nitration of nitrocellulose by refractometry
Authors: Kohlbeck J. A. , Bolleter W. T.
Published: April 2003

Nitrocellulose (NC) films, when dried on a rigid substrate, tend to be biaxial and thus exhibit two refractive indices. The absolute difference between these indices has been found to provide an accurate measure of the degree of nitration of NC. A film of NC is cast from a 1% solution in butyl acetate to provide a film about 0.5 mil thick. The dry film, when placed in an Abbé‐3L refractometer, gives two white lines which go to extinction alternately upon rotation of a cap analyzer through the east–west (EW) and north–south (NS) directions. Refractive index measurements are made using the line visible in each direction of the analyzer. The absolute difference between the two indices is related to the degree of nitration through standard curves for various grades of NC. The standard deviation for the proposed method was found to be ±0.01% N.
Some properties of low molecular weight polybutadiene and polytetrahydrofuran
Authors: Huglin M. B. , Whitehurst D. H.
Published: April 2003

The proposition, that low molecular weight polymer fractions in good solvents behave as if they were under ⊖ conditions, has been examined experimentally. Series of monodisperse hydroxy‐terminated polytetrahydrofuran (PTHF), 82% 1,4‐polybutadiene (PBD), and 30% 1,4‐PBD were prepared, and values of M̄n obtained by vapor‐pressure osmometry and endgroup analysis. The Mark–Houwink viscosity parameters K and ν were determined in a number of solvents. The general conclusion is that the proposition is invalid for these systems notwithstanding the fact that ν = 0.50 for one of them [82% 1,4‐PBD in methyl ethyl ketone (MEK) at 25°C]. For this particular case, the following evidence suggests that these are actually ⊖ conditions so that the apparent fulfilment of the proposition is fortuitous. (1) Cloud‐point precipitation yields ⊖ = 26 ± 3°C in MEK. (2) The value of K is close to that of K⊖ found elsewhere for PBD in a different solvent at a similar temperature. (3) Application of the Kurata‐Stockmayer iterative procedure for estimating K⊖ from data in good and bad solvents yields a reasonably small discrepancy (10%) between the K⊖ values from data in toluene and MEK at 25°C for this polymer and only a 3% difference in the unperturbed dimensions (〈r02〉/M)1/2 derived from them. Measured melting points Tm of PTHF (M̄n = 1000–13000), plotted as a function of chain length Z, viz., 1/Tm = 1/Tm0 + 2R/ZΔHf, yield 43 ± 3°C and 1.6 kcal/submole, respectively, for the limiting melting point Tm0 and the heat of fusion ΔHf. The former is in good agreement with the value obtained dilatometrically for high molecular weight polymer, while the latter indicates a degree of crystallinity of ca. 54%.
Molding of polyacrylonitrile
Authors: Griffith R. K.
Published: April 2003

A method has been devised whereby clear, chemically resistant, compression‐molded articles of polyacrylonitrile are prepared within minutes. The molding powder consists of preformed polyacrylonitrile, acrylonitrile, and initiator. The effects of process variables on the physical properties are discussed.
Polymer–solvent interaction parameters and efficiency of crosslinking of ethylene–propylene copolymers
Authors: Flisi U. , Crespi G.
Published: April 2003

A study has been carried out of the vulcanization of ethylene–propylene copolymers having different propylene contents, by use of an organic peroxide. The polymersolvent interaction parameter μ, calculated by the Flory‐Rehner equation from values of νe and vr, was found to be a linear function of vr with benzene as the swelling agent. Values of μ and their dependence upon vr were independent of copolymer composition, at least within the limits of experimental error, for samples having a propylene content of 30–60 mole‐%. The crosslinking efficiency of the peroxide used was found to depend considerably on copolymer composition, in agreement with the results found for dicumyl peroxide. Finally, sulfur as a crosslinking coagent was found to exert a large effect on the value of νe, calculated from the equilibrium retractive force of benzene‐swollen specimens.
Torsional braid as a kinetic tool for the study of the polymerization of viscous materials. II. Catalytic effects in the polymerization of carboxylic acid‐terminated polybutadiene prepolymers with tris[1‐(2‐methyl)aziridinyl]phosphine oxide
Authors: Adicoff Arnold , Yukelson Arnold A.
Published: April 2003

The torsional braid technique for studying the polymerization of viscous substances has been extended to a study of the homogenous catalytic behavior of a number of acidic and basic catalysts int he polymerization of carboxy‐terminated polybutadiene with tris(methyl aziridinyl)phosphine oxide. No general catalytic behavior was observed. Specific catalysis was observed in the case of lithium oleate, where the gel time was decreased, and in the case of bis(tri‐n‐butyltin) oxide, where the gel time was increased. The average energy of activation for all of these polymerizations was 13.9 ± 0.5 kcal./mole. This energy of activation and the reaction environment, when compared with the data in the literature, strongly suggest that the explanation that a change in the rate‐determining step occurs as a function of the polarity of the reaction medium fails to account for all of the results.
Steric effects in the basic hydrolysis of poly(ethylene terephthalate)
Authors: Namboori C. G. G. , Haith Malcolm S.
Published: April 2003

A comparative study of the reactivity of hydroxide and various alkoxide anions was made by determining percentage weight loss of poly(ethylene terephthalate) fiber. Regardless of the basicity of the anions, the order of reactivity was found to be hydroxide < tert‐butoxide < sec‐propoxide < methoxide < ethoxide. This observed order follows the nucleophilicity of the bases, and the relatively lower reactivity of sec‐propoxide and tert‐butoxide is assumed to be due to steric retardation during the equilibrium reactions.
Study of radiation‐induced graft polymerization of vinyl monomers to cellulose by infrared spectroscopy. II. Cellulose–polystyrene copolymers
Authors: Imrišováa D. , Maryška S.
Published: April 2003

Infrared spectral analysis has been applied for the study of cotton‐polystyrene copolymers prepared by using the preirradiation method. The degree of grafting was determined from the absorption at 700 cm−1, which is characteristic of the polystyrene spectrum, with an accuracy of ± 1.5%.
Viscoelastic changes of epoxy resin–acid anhydride system during curing
Authors: Shimazaki Akio
Published: April 2003

The changed viscoelastic properties of the epoxy resin‐acid anhydride system, Epikote 834‐HHPA, are followed to the gel point at 130, 140, and 150°C with a dynamic viscoelastometer. The viscosity increases with curing time through two inflections designated A and B. The point A is interpreted (from the reference to the chemical changes reported in the previous paper) as the termination of the initial stage of this curring reaction, and point B coincides with the gel point determined by the torsion method. The resonance frequency remains constant value up to the point B, followed by a rapid increase. The extents of reaction for epoxide, anhydride, and initial OH are 15, 45.8, and 100% at the point A; 27.8, 63.7, and 100% at the point B, respectively. The apparent activation energies for viscosity are 7.5 kcal/mole for the resin mixture before curing, 10.5 kcal/mole for point A, 48.8 kcal/mole for point B (gel point). The overall apparent activation energies of this curing reaction are obtained from the Arrhenius plots for the curing time required for the resin mixture to reach the state of the points A and B; these values were 8.9 kcal/mole for point A and 16.2 kcal/mole for point B.
Gel–water relationships in hydrophilic polymers: Thermodynamics of sorption of water vapor
Authors: Masuzawa Mitsunobu , Sterling Clarence
Published: April 2003

A thermodynamic study was conducted of water vapor adsorption on four hydrophilic polymers (agar, carboxymethyl cellulose, gelatin, and maize starch) at 12 and 25°C. Monolayer coverage amounted, after correction for crystallinity, respectively, to 0.93, 1.46, 0.51, and 0.77 mol water/mol monomer. Evidence is adduced from the Bradley equation and thermodynamic data to indicate that at least during coverage with the second layer of water, the energy of adsorption is greater than that due to condensation alone. Differences in the amount of sorption and in the trend of values of ΔS̄° and ΔH̄° with the amount of sorbed water are related with differences in the strength of intermolecular association as affected by steric hindrances.
Chlorination of polystyrene
Authors: Jenkins Robert K. , Byrd Norman R. , Lister James L.
Published: April 2003

Chlorination of a low molecular weight polystyrene in the α position was studied by following changes in the infrared spectrum, glass transition temperature, and molecular weights of the polymer. The logarithm of the absorbance ratio at 2920 and 1500 cm−1 as a function of mole per cent chlorination was linear. The glass transition temperatures, determined by use of a differential scanning calorimeter (DSC), were found to obey an equation developed by Dyvik for copolymers. The molecular weight of the chlorinated polystyrene decreased as a function of chlorination.
Characterization of nylon 66 structure from x‐ray diffraction
Authors: Dumbleton J. H. , Buchanan D. R. , Bowles B. B.
Published: April 2003

A description of methods available for the determination of structural parameters in nylon 66 is given for both wide‐ and small‐angle x‐ray diffraction. The methods are applied to a series of drawn nylon 66 fibers, and the results indicate that the drawing process is one of crystal slip. It is concluded that the methods of characterization give a great deal of information about the structure along the fiber axis but that methods for examining the structure perpendicular to the fiber axis give less quantitative information and new methods are desirable.
Physical properties of some vinyl tetrahydroabietate and vinyl maleopimarate acid anhydride copolymers
Authors: Magne F. C.
Published: April 2003

The stress–strain and torsional characteristics of some experimental copolymers of vinyl tetrahydroabietate and vinyl maleopimarate acid anhydride with vinyl chloride and vinyl acetate have been determined. Similar studies were also undertaken on peroxide‐cured compositions of a vinyl chloride‐vinyl tetrahydroabietate copolymer. Elastie moduli for the uncured copolymers range from 80,200 to 338,000 psi. Cured compositions of vinyl chloride–vinyl tetrahydroabietate copolymer exhibited both lower and higher moduli than that of the uncured copolymer. Some of the cured compositions appear to have an improved impact resistance over that of the uncured polymers.
Crosslinking poly(ethylene oxide) in dilute solutions by gamma rays
Authors: Van Brederode R. A. , Rodriguez F. , Cocks G. G.
Published: April 2003

A high molecular weight poly(ethylene oxide) is gelled by radiation from a 60Co source. At concentrations of 0.25 to 1 wt‐%, doses of 4.5 to 7.5 × 104 rad cause gelation. The storage modulus of the gel formed increases linearly with additional dose to a plateau value and then remains constant during further irradiation. The does needed to reach the plateau, Dp in rads, and the plateau modulus Gp in dynes per square centimeter, are related to the concentration c, in weight per cent: Dp = 1.05 × 106c and Gp = 1.75 × 104c2.5. The energy absorbed by the polymer per crosslink formed is about 80 ± 10 kcal/mol. The crosslink density produced by radiation is calculated from the measured modulus by using the theory of rubber elasticity. Both modulus and loss are measured in a special air‐bearing, recording torsion pendulum with a coneplate geometry.
Intrinsic viscosity–molecular weight relationship for low molecular weight nylon 6
Authors: Hague P. , Huglin M. B. , Johnson B. L. , Smith J.
Published: April 2003

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

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

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

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

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