bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential thermal analysis of high polymers. V. Ethylene copolymers
Authors: Ke Bacon 
Published: April 2003

AbstractMelting and crystalline properties of methyl‐and ethyl‐branched polymethylenes—models for ethylene‐propylene and ethylene–α‐butene copolymers—containing up to 20 branches per 1000 carbon atoms have been investigated by differential thermal analysis (DTA). The melting‐point depression is practically linear with branch concentration. However, ethyl groups are more effective than methyl groups. Cooling at different rates during annealing produces a wider melting‐point spread in copolymers containing more branches. Again, copolymers containing ethyl groups are affected more than those having an equal number of methyl groups. Copolymer crystallinity estimated by DTA also decreases linearly with the number of branches; ethyl groups disrupt crystallinity more markedly than methyl groups do. The effect of colling rates on crystallinity increases with branch concentration. Melting and crystalline behavior of two commercial ethylene copolymers agree with patterns derived from the models. The thermogram of a crystalline ethylene‐propylene block copolymer consists of two separate melting peaks corresponding to crystalline regions formed by ethylene and propylene sequences. Total crystallinity of this copolymer was estimated and used in calculating the copolymer composition. Restrictions for crystallization in the block copolymer are apparent from the thermogram.
An expression for orientation in cellulose fibers
Authors: Gupta V. D. 
Published: April 2003

AbstractHermans' orientation factor can be evaluated only when the diatropic and paratropic interferences arise from planes which form an orthogonal set. This is only approximately satisfied in case of both cellulose I and cellulose II. In the present communication an exact expression has been derived which can be evaluated from x‐ray measurements, angle between face normals of paratropic interferences, and the optical constants.
The contribution of internal energy to the elastic force of natural rubber
Authors: Roe R.‐J. , Krigbaum W. R. 
Published: April 2003

AbstractData are reported for the temperature coefficient of the retractive force for a natural rubber sample which had been crosslinked by irradiation. These measurements differ from those previously reported in allowing a longer interval for the attainment of equilibrium, in covering a wider range of elongations, and in a somewhat greater precision of the tension measurement. The Mooney equation constants for the tension at 45°C. are 2C1 = 2.617 kg./cm.2 and 2C2 = 0.876 kg./cm.2. The latter, although smaller than the values reported by other workers for similar samples, is far from vanishing. A comparison is given of (∂f/∂T)V,L as evaluated from the measured (∂f/∂T)V,L according to various proposals. Approximately 20% of the total force arises from the internal energy contribution, fe, when the relative elongation, α, is near unity. The fe/f ratios calculated from our measurements stand in good agreement with those obtained from Ciferri's data, despite the fact that the latter correspond to a much larger C2 value. Furthermore, both sets of data indicate that fe/f decreases with increasing α. The entropy component of the force, when fitted to the Mooney equation, yields C1s ≅ C1 but C2s < C2. This suggests that the C1 term is primarily due to entropy effects, whereas the internal energy makes a larger contribution to C2. The nonvanishing C2 and the variation of the fe/f ratio with α, represent deviations from the gaussian model treatment of Flory, Hoeve, and Ciferri. Criferri and Flory have expressed the opinion that finite C2 values arise solely from the failure to attain mechanical equilibrium. However, the cubic lattice model treatment of Krigbaum and Kaneko indicated that although the two discrepancies cited above may be accentuated by nonequilibrium effects, they can only be expected to vanish under equilibrium conditions in the limit of infinite chain length between crosslinks.
Solution‐grown polyethylene dendrites
Authors: Wunderlich Bernhard , Sullivan Peter 
Published: April 2003

AbstractPolyethylene has been crystallized from toluene solution under varying conditions of quenching. The concentration, temperature gradient, pressure, and viscosity has been varied. Depending upon the conditions, different dendrites were found. The dendrites were named in accordance with their appearance: epitaxial dendrites, rightangle dendrites, six‐ended dendrites, and hedgehog dendrites. The resulting structures were analyzed with an interference microscope and with a polarizing microscope. On flattening dendrites on the microscope slide, regular structures with a weak birefringence of 0.0026 and an average refractive index of 1.527 ± 0.009 were found. The dendrites have a bundlelike appearance in three dimensions with a strong birefringence (∼0.07). Correlation to single crystal growth from solution and spherulitic growth from the melt has been attempted.
Reactions of carboxylated butadiene–styrene rubbers and their mixtures with ε‐caprolactam induced by γ‐radiation
Authors: Mladenov I. , Tutorskiǐ I. A. , Dogadkin B. A. 
Published: April 2003

AbstractCarboxylated butadiene–styrene rubber containing various amounts of styrene and methacrylic acid were exposed to 0.1–50 Mr doses of γ‐radiation from a Co60 source. This irradiation resulted in a decrease in the carboxyl group content, particularly at low doses. The radiochemical yield of crosslinked polymers at low doses is a linear function of the carboxyl group content of the initial polymer. The number of crosslinks formed by the carboxyl groups at doses up to 20 Mr calculated from the maximum swelling data was found to agree satisfactorily with the number of crosslinks as calculated from the carboxyl group consumption. Irradiation of the carboxylated rubber in mixtures with ε‐caprolactam gives rise to addition of the latter to the rubber with formation of insoluble compounds. The amount of caprolactam combining with the rubber increases linearly with an increase in ε‐caprolactam content of the original mixtures in the range of 5–50%. There is also an increase in the degree of crosslinking. An increase in the bound ε‐caprolactam content leads to an increase in the tensile strength of the polymer.
Polymerization of methyl methacrylate by triethylboron–oxygen mixtures
Authors: Welch F. J. 
Published: April 2003

AbstractThe effect of oxygen on the rate of polymerization of methyl methacrylate catalyzed by triethylboron has been investigated at temperatures in the range 0–52°C. In the absence of oxygen polymerization does not occur, but formation of polymer begins immediately on admission of oxygen. Polymerization is characterized by a decrease in rate with increasing conversion which is most pronounced when the concentrations of oxygen and triethylboron are greatly different. The initial rate of polymerization is proportional to the square root of the oxygen concentration and inversely proportional to the degree of polymerization of poly(methyl methacrylate) formed, confirming the radical nature of the polymerization. The apparent activation energy for the polymerization was unusually low, only 4 kcal./mole. A mechanism in which initiating radicals are produced by a sequence of reactions involving autoxidation of the boron alkyl to peroxide followed by induced decomposition of the peroxide by excess boron alkyl is suggested.
γ‐initiated crosslinking of unsaturated polyesters
Authors: Burlant W. , Hinsch J. 
Published: April 2003

AbstractUnsaturated polyesters containing 1.5, 3.2, and 4.8 double bonds per molecule (derived from maleic anhydride, phthalic anhydride, and propylene glycol) were crosslinked by γ‐rays from Co60. From sol fraction data and from measurements of the molecular weight between crosslinks of the corresponding gel, it is concluded that for polymers containing more than about 4 double bonds per molecule, γ‐initiated bond formation is in accord with the reported chain reaction scheme for such systems. At lower degrees of unsaturation, a significant fraction of the initially available unsaturated sites has been consumed at the gel point so that subsequent radiation (and radical formation), which effects chain growth at the expense of intramolecular crosslinking, appears to be in part, a random process. It is suggested that radiation‐induced changes in unsaturated polyesters are best described in terms of the simultaneously occurring chain growth and intramolecular crosslink formation.
Crystallization kinetics of poly‐3,3‐bis(chloromethyl) oxacyclobutane
Authors: Inoue Masakazu 
Published: April 2003

AbstractThe crystallization kinetics of poly‐3,3‐bis(chloromethyl) oxacyclobutane has been investigated by the method of dilatometry, and at the same time the growth rate of spherulites was measured under the polarizing microscopy. Isothermal crystallizations of this polymer were carried out at constant crystallization temperature over the range of 150–160°C., and the rate constants were calculated by the Avrami equation. Crystallization proceeds through a mechanism of homogeneous nucleation and fibril growth. The growth rates of spherulites were measured at various constant crystallization temperatures of 75–140°C. Under a polarizing microscopy, the spherulites formed are seen to be of two morphological types; one is four‐cornered and another is petal‐shaped.
Preparation of regularly alternating polyesteramides
Authors: Williams J. L. R. , Laakso T. M. , Contois L. E. 
Published: April 2003

AbstractRegularly alternating polyesteramides with glycol components ranging from C2 to C14 and interamide linkages ranging from 2 to 6 have been prepared by high‐temperature polycondensation of performed bisesteramides with sodium hydrogen tetrabutyltitanate as catalyst.
Magnetic anisotropy effects in broadline NMR spectra of polytetrafluoroethylene
Authors: Wilson Charles W. 
Published: April 2003

AbstractThe effects of molecular magnetic anisotropy upon the broadline NMR spectrum of a bulk polymer have been recognized and measured for the first time. The F19 NMR absorption spectra in polytetrafluoroethylen (PTFE) show a line‐shape asymmetry over a broad range of temperatures which can be explained by the magnetic anisotropy of C‐F bonds. Nuclear magnetic resonance studies of PTFE samples whose crystalline regions are aligned by cold drawing have made possible an estimate of the anisotropy of C‐F bonds in this material: Δσ, the magnetic anisotropy of the screening constant, is found to be 171 ± 15 ppm; the screening of each F19 nucleus is paramagnetic, being maximum when the direction of its C‐F bond is perpendicular to the large static magnetic field and minimum (probably zero) when parallel. Static magnetic susceptibility measurements of PTFE show the predicted diamagnetism, and only a small (<5%) static magnetic anisotropy of the molecular crystals is found.
Infrared studies of popcorn polymerization. I. Oxidation of butadiene popcorn polymer
Authors: Miller Glenn H. , Larson Virginia R. , Pritchard Glyn O. 
Published: April 2003

AbstractAn infrared analysis of butadiene popcorn polymer showed the structure to be highly unsaturated with all of the groupings around the double bonds in the trans‐position. The oxidation of the polymer produces aldehydes and ketones, but due to the nature of the infrared‐pelleting technique which had to be used, it was not possible to resolve the broad spectral peaks for the positive identification of other structures. There was no apparent loss of unsaturation during the oxidation process. The loss in popcorn polymer growth activity shown when it is reseeded above fresh butadiene monomer is attributed to the loss of the hydrogen atoms that could participate in a transfer reaction. The latter is undoubtedly responsible for much of the rapid growth phenomena exhibited by this type of polymer.
Viscoelastic properties of amorphous selenium
Authors: Eisenberg A. , Tobolsky A. V. 
Published: April 2003

AbstractViscoelastic properties of amorphous selenium were studied by stress relaxation, creep, and a new technique described in this paper. A master curve was obtained as well as maximum relaxation times at several temperatures. The glass transition temperature was obtained from volume‐temperature relations. A technique is described for the study of hard viscoelastic materials.
Stereospecific polymerization of acetaldehyde. Part I
Authors: Ishida Shin‐Ichi 
Published: April 2003

AbstractStereospecific polymerization of acetaldehyde by triethylaluminum was studied. It was found that some catalyst was made at room temperature or at a low temperature and that the effective catalyst of the polymerization was the reaction product of organometallic compound and water contained in aldehyde. When addition is made at room temperature, Polymerization proceeds more rapidly than when at low temperature. and there is a miximal conversion at a certain concentration of catalyst. Because the maximal catalytic activity occurred at a molar ratio of H2O/ALEt3 of about 0.5, the effective catalyst is considered to be tetraethyl dialumoxane not but triethylaluminum itself. It is considered that the dialumoxane produced the stereogularity in the present case. Crystalline polyacetaldhyde was formed even in a homogeneous solution. The polarity of solvent did not completely destroy the stereospecificity but reduced the yield of polymer in spite of the ionic nature of the polymerization. Clear relationships were obtained between the dipole moment, or the logarithm of dielectric constant of the solvent used, and the conversion. It was found that there is a critical temperature near −40°C., above which polymer could not be obtained, and that as the temperature was lowered below −40°C. the rate of reaction was increased, showing negative temperature coefficient. The critical temperature −40°C., may be regarded as a ceiling temperature for the polymerization of acetaldehyde.
Polymerization of 2,4,6‐triallyloxypyrimidine
Authors: Clampitt Bert H. , Mueller Arthur P. 
Published: April 2003

AbstractThe preparation of trallyloxypyrimidine is described, together with the polymerization characteristics of this compound under differential thermal analysis conditions. The DTA curves show a doublet first exotherm near 100°C, and a singlet exotherm at 225°C. Combining the heat values obtained from the DTA curves with infrared spectral data indicates that the complex first exotherm represents a total polymerization of two allyl groups, while the second exotherm involves rearrangment to the barbiturate structure. The fact that the last allyl group does not polymerize during the second exotherm is due to the presence of a hydroxyl group in the rearranged structure. The results are compared to a previous study of the reaction mechanism of triallyl cyanurate polymerization.
The polymerization reaction in liquid sulfur dioxide. Part VIII. The effect of aromatic compounds on the cationic polymerization of styrene in liquid sulfur dioxide
Authors: Tokura Niichiro , Matsuda Minoru , Watanabe Yasuaki 
Published: April 2003

AbstractThe cationic polymerization of styrene in liquid sulfur dioxide was conducted at −10°C. in the presence of hydrocarbons such as benzene, toluene, p‐xylene, p‐cymene anisole, cyclohexane, and chlorobenzene diluted with carbon tetrachloride and with boron trifluoride etherate as catalyst. When aromatic hydrocarbons were added to the polymerizing system in liquid sulfur dioxide, both overall rate and degree of polymerization decreased with increasing of hydrocarbon concentration. On the other hand, the rate and degree of polymerization increased as the concentrations cyclohexane or chlorobenzene added increased. When anisole was used, polymerization was completely inhibited. The order of solvent participation n on the polymerization in liquid sulfur dioxide was obtained. The magnitude and the sign of n is discussed and explained by interaction of the added solvent with the active carbonium ion of the growing chain and with liquid sulfur dioxide.
Trifluoronitrosomethane/tetrafluoroethylene copolymer: Degradation by heat and by radiation
Authors: Shultz A. R. , Knoll N. , Morneau G. A. 
Published: April 2003

AbstractThermal degradation of trifluoronitrosomethane/tetrafluoroethylene copolymer yields COF2 and CF3NCF2 as gaseous decomposition products. The copolymer weight loss appears first order in copolymer. The activation energy is 58 kcal./mole, and the first‐order rate constant is approximately k1 (min.−1) = 3.1 ′ 1021 exp {‐29,047/T} determined in the 250–265°C. range. A rather large weight fraction of low molecular weight species exists in some nonfractionated copolymer samples leading to rapid initial weight losses upon heating. Thermogravimetric and differential thermal analyses were used to observe a thermal runaway decomposition at temperatures above 270°C. Gamma radiations from spent atomic fuel elements produce random scissions in the copolymer chains followed by COF2 and CF3NCF2 evolution. At 23°C. the total energy absorption per primary chain scission is Ed = 44 e.v./scission. For each chain scission an average of approximately 5.3CF2N(CF3)OCF2 units decompose to COF2 and CF3NCF2. In systems containing these product gases at appreciable pressure an adduct, (CF3)2NCOF, is produced. Ultraviolet light of 2537 A. wavelength photolyzes the copolymer producing random chain scissions and the gases COF2 and CF3NCF2. The quantum yield for primary random chain scission at 23°C. is ϕd = 0.91 × 10−3 scissions/absorbed photon; the equivalent total energy absorption per event is Ed = 5400 e.v./scission. An average of approximately 3.6 CF2N(CF3)OCF2 units decompose to COF2 and CF3NCF2 for each chain scission.
Elution fractionation of atactic and isotactic polypropylene
Authors: Shyluk Shirley 
Published: April 2003

AbstractProcedures and an apparatus for the elution fractionation of polypropylenes are described. The isotactic polymer is precipitated onto a sand column from p‐xylene solution by cooling slowly from 126°C. to room temperature. After removal of the solvent and the atactic fraction soluble at room temperature, the column is heated to 156°C. Fractions are eluted with mixtures of a high boiling hydrocarbon fraction as solvent and 10% ethylene glycol in 2‐butoxyethanol as nonsolvent. The dissolving power of the eluents is periodically increased to fractionate the polymer. Upward solvent flow is used. Recovery is usually quantitative, and good reproducibility is demonstrated. Polymer degradation during fractionation has been reduced to generally less than 5% by suitable techniques. Molecular weight distribution curves for three samples are shown. Good selectivity is established by the fact that the ratio of the molecular weight of the highest to that of the lowest fraction is usually in the range of 50 to 200. A description of the fractionation of atactic polypropylene is given also. The atactic material was used to show the effect of depositing the polymer selectively or randomly on the surface of the support as well as the effect of diffusion on fractionation efficiency.
Structural dependence of the electrical conductivity of polyethylene terephthalate
Authors: Amborski Leonard E. 
Published: April 2003

AbstractThe direct current conductivity of three different forms of polyethylene terephthalate was studied over a wide temperature and voltage range to determine the structural dependence of the conduction process. From the films in the amorphous, crystallized, and oriented and crystallized forms it was determined that crystallization reduces the conductivity by more than one order of magnitude. Orientation results in a sixfold decrease in conductivity. The conductivity does not change over a wide range of molecular weight or carboxyl end group concentration. As shown from model polymers and copolymers, disruption of chain symmetry and molecular packing, introduction of side chains, or any other modification which reduces the crystallinity and order, results in greater conductivity. The structural dependence of conductivity, the temperature dependence, and the current–voltage relationships of polyethylene terephthalate are consistent with a proposed ionic mechanism for the conduction process.
Infrared specturm of cellulose I in relation to its structure
Authors: Saksena B. D. , Agarwal K. C. , Jauhri G. S. 
Published: April 2003

AbstractThe infrared data for cellulose I have been critically analyzed and are found to show two parallel and four perpendicular bands in the region of OH stretching. In the region of CH stretching there are two parallel bands and four perpendicular bands. If we imagine that the chains have random phase and a twofold screw axis passes down each chain we should expect six OH frequencies. From the coordinates of O2, O3, and O6 it is shown that two modes should show parallel and four modes perpendicular dichroism. It is also shown that the mode which represents the oscillation of hydrogen atoms against oxygen atoms parallel to the line joining hydroxyl oxygen atoms O2 and O3 can produce intramolecular hydrogen bonding and should be a parallel mode. This is identified with the strong parallel band at 3350 cm.−1 Since each band should become double by virtue of symmetry and antisymmetry with respect to the screw axis we should have two parallel modes, and these are identified with parallel bands at 3350 and 3275 cm.−1. The position of the oxygen atom O6 and of hydrogen atoms H61, H62 of groups CH2 have been calculated. It is shown that the oscillating dipole moment in symmetric CH stretching mode makes an angle of 39°17′ and in the CH antisymmetric stretch an angle of 50°43′ with the fiber axis and therefore both should show parallel dichroism. These are respectively identified with bands at 2853 and 2967 cm.−1. The remaining CH vibrations belonging to the hydrogen atoms of the glucopyranose ring should show perpendicular dichroism. Four vibrations at 2945, 2910, 2897, and 2870 cm.−1 are identified with these CH vibrations. Thus all the infrared predictions are explained on the basis of the Meyer and Misch structure of cellulose I provided we assume that the chains have a random phase relationship. That a two‐fold screw axis runs along each chain direction is also in agreement with the infrared data.
Some polymers and copolymers of vinyl ketostearates
Authors: Marvel C. S. , Dykstra T. K. , Magne F. C. 
Published: April 2003

AbstractVinyl esters of 4‐ketostearic acid, 9(10)‐ketostearic acid, and 12‐ketostearic acid have been homopolymerized and copolymerized with vinyl chloride. Reactivity ratios have been determined for the three vinyl ketostearates with vinyl acetate and vinylidine chloride. Also reactivity ratios for the 4‐ and 10‐ketostearates with vinyl chloride and those of the 9(10)‐ketostearates and 12‐ketostearate with acrylonitrile were determined. The mechanical properties of typical vinyl chloride‐vinyl ketostearate copolymers have been examined and compared with a similar vinyl chloride‐vinyl stearate copolymer and with a plasticized vinyl chloride‐vinyl acetate copolymer. The copolymers of vinyl chloride with vinyl 9(10)‐ketostearate and with vinyl 12‐ketostearate compare favorably with the compolymer of vinyl chloride and vinyl stearate in general properties.
Dynamic mechanical properties of high molecular weight nylon 66 fiber
Authors: Murayama Takayuki , Silverman Bernard 
Published: April 2003

AbstractDynamic mechanical properties of the ultrahigh molecular weight nylon 66 film and fiber produced by thermally induced solid‐state polycondensation are presented. The α peak temperature of tan δ of these treated films and fibers is shifted 8–32°C higher than that of the appropriate control nylon 66 (film and fiber) while the maximum height of the tan δ peaks is decreased. The treated fibers have higher moduli at all temperatures (20–145°C) and humidities (30% RH) than do their control counterparts. The moduli of the treated fibers at 30% RH compare favorably with control yarn at 0% RH. These yarns also have a greater per cent of the 25°C modulus retention as temperature increases.