bluuebunny/crossref_metadata_2025_split huggingface dataset:
ESR study of irradiated acrylic acid and reaction of the produced radical
Authors: Shioji Yūji , Ohnishi Shun‐Ichi , Nitta Isamu 
Published: April 2003

AbstractA single crystal of acrylic acid CH2CHCOOH was irradiated at −196°C. and its ESR spectrum was measured at that temperature with various crystal orientations with respect to the external magnetic field. At −196°C. the spectrum appears as a double quartet, the doublet showing anisotropy. By analyzing the spectrum, the hyperfine coupling tensor was derived. The result showed that the radical was CH3ĊHCOOH produced by hydrogen addition to the double bond. Referring to the molecular orientation of acrylic acid in the crystal, it was found that the radical was oriented in the crystalline lattice in the same way as the undamaged molecule. When the temperature was raised from −196°C. the double quartet spectrum began to decay at −100°C., and there remained a triplet spectrum showing no anisotropy. The triplet may be attributed to a propagating type radical In order to compare the ESR result with polymerization process, monomer preirradiated at −196°C. was postpolymerized at various elevated temperatures. It was found that although the radical decayed at −78°C. no discernible polymer was obtained at that temperature. These results suggest that, although the radical can move and be reactive at −78°C. which is far below the melting point, it does not seem sufficiently mobile to permit growth of the propagating chain to any observable extent.
Study of the base‐catalyzed cellulose–d,l‐butadiene diepoxide reaction
Authors: Benerito Ruth R. , Berni Ralph J. , McKelvey John B. , Burgis Beverly G. 
Published: April 2003

AbstractThe reaction of cotton cellulose with d,l isomers of butadiene diepoxide (BDO) in the presence of base catalysis has been investigated as a continuation of work previously reported on the reaction between cotton cellulose and the meso isomer (BDE). The BDO has been found to react similarly out of CCl4 solutions with fabrics pretreated with dilute solutions of base. However, unlike the meso isomer, which is less soluble in concentrated base, the BDO has been found to increase dry as well as wet crease resistance of cotton pretreated with aqueous solutions as concentrated at 23% NaOH. Increased wet crease resistance was imparted to cotton at low add‐ons of BDO to fabric pretreated with all concentrations of base. Increased dry crease resistance was imparted at low add‐ons of BDO to only those fabrics pretreated with dilute solutions of NaOH. For those fabrics pretreated with 10% or 15% NaOH, higher add‐ons of BDO were required to impart high dry as well as high wet crease resistance. Speed of the reaction was increased with increase of base concentration or by removal of water from fabrics pretreated with dilute base. With the latter, rate of increase of dry crease resistance also increased. Optical microscopical examinations of fibers and electron micrographs of ultrathin cross sections of these fibers after immersion in cuene gave evidence of degree of crosslinking of the cellulose. Evidence from these microscopical observations has been correlated with textile properties of fabrics. Intersting changes in fabric properties of BDO treated cotton with heat have been investigated. Optimum fabric properties have been obtained by reducing the amount of water in cotton after pretreatments with aqueous base and thus reducing the degree of polymerization of BDO. Data are also given to show influence of hydration of cation of strong base on degree of polymerization of BDO.
Properties of melt‐blends of crystalline high polymers. Fusion and crystallization behaviors
Authors: Inoue Masakazu 
Published: April 2003

AbstractThe fusion and crystallization behavior of melt blends of crystalline high polymers was studied by differential thermal analysis. The crystalline high polymers used for the experiments are nylon 6, nylon 66, nylon 11, high density polyethylene, and isotactic polypropylene. The thermograms of fusion of the melt blends indicate that each component produces an endothermic peak which retains its characteristic shape. In the blends of two crystalline polymers, only the melting point of high melting component is lowered, while that of low melting component hardly shifts. As for the degree of crystallization of each component in the blends, the major component crystallizes to a higher degree than the minor component. In the blends, the crystallization peak temperature of the high melting polymer decreases, while that of the low melting polymer increases. The morphological structures of each component, especially those of the low melting component, in the blends are affected by blending.
Synergistic antioxidant combinations. Mechanism of stabilization with organo‐sulfur compounds
Authors: Hawkins W. L. , Sautter H. 
Published: April 2003

AbstractThe ability of diaryl disulfides to inhibit polyethylene oxidation is a result of the formation of an active antioxidant from these additives. This is evident from their ineffectiveness to inhibit until substantial oxidation has occurred. Elemental sulfur also appears to form a more effective stabilizer as oxidation proceeds. Thiolsulfinates have been suggested as the active products which are formed from disulfides. However, phenyl benzenethiolsulfinate decomposes rapidly even at its melting point (70°C.), and yet the protection obtained when it is added to cumene at 120°C. far exceeds the time in which total decomposition would occur. At low concentrations, phenyl benzenethiolsulfinate also fails to inhibit until oxidation has proceeded for an appreciable time. Thermal decomposition of phenyl benzenethiolsulfinate yields sulfur dioxide in addition to other products. Elemental sulfur and the several organo‐sulfur compounds studied function as stabilizers through their ability to decompose peroxides. Sulfur dioxide is by far the most effective peroxide decomposer. It apparently functions catalytically through an ionic mechanism forming products which do not propagate oxidation. The additional role of sulfur compounds to decompose peroxides, coupled with the ability to regenerate chain terminators in antioxidant combinations may account for the high order of synergism obtained with these compounds.
Preparation and biological application of highly substituted cationic derivatives of polysaccharides
Authors: Wood John W. , Mora Peter T. 
Published: April 2003

AbstractA general procedure is presented for the preparation of diethylaminohydroxylpropyl ethers of polysaccharides. This involves reaction between various ratios of 1‐diethylamino‐2,3‐epoxypropane and the polysaccharide (amylose, amylopectin, dextran, and a chemically synthesized polygalactose) and concentrated aqueous solution of sodium carbonate. These ratios control the degree of substitution, and give as high as 1.4 cationic groups per monosaccharide unit in the case of certain polysaccharides. The cationic polysaccharides possess high hemagglutinating activity which is proportional to the degree of substitution. Other biological applications are reviewed.
Thermodynamic interpretations of the elastic properties of rubbers obtained from ethylene—propylene copolymers
Authors: Natta G. , Crespi G. , Flisi U. 
Published: April 2003

AbstractStress—temperature coefficients have been measured for a high‐molecular‐weight ethylene—propylene copolymer, containing 45 mole‐% of ethylene, chlorinated and vulcanized with a cure system based on sulphur and accelerators. From the relationships:

the thermodynamic functions [∂E/∂L]T and — T [∂S/∂L]T have been determined in a range of the extension ratio up to α=6.9. A good agreement has been found between the experimental data and the stress—strain theoretical curve obtained for a non‐Gaussian type network.
Nitrosation of linear phenol‐formaldehyde polymers
Authors: Burke William J. , Higginbottom Harold P. 
Published: April 2003

AbstractThe nitrosation of o,o‐linked linear phenol‐formaldehyde polymers was readily affected in aqueous N,N‐dimethylformamide to give products containing p‐benzoquinone monoxime repeating units. Elemental analyses and infrared spectra indicated the presence of nitrophenol moieties also. Factors influencing the nature of the nitrosation reaction were studied.
Anionic polymerization of acrylonitrile by various catalysts
Authors: Ottolenghi Ariel , Barzakay Samuel , Zilkha Albert 
Published: April 2003

AbstractThe polymerization of acrylonitrile was studied using cyclopentadienyllithium, cyclopentadienyl sodium, fluorenylithium, and phenyllithium, and was compared to polymerization with butyllithium. With phenyllithium and fluorenyllithium in tetrahydrofuran, termination was found to be by chain transfer to monomer. The homogeneous polymerization in dimethylformamide carried out at both high and low catalyst concentrations showed that at high catalyst concentrations the molecular weights of polymer increased sharply with monomer concentration using cyclopentadienyllithium and cyclopentadienyl sodium, unlike the case of polymer obtained with butyllithium and fluorenyllithium. The increase in molecular weight is due to what has been previously found that the cyclopentadienyl anion acts as a polyfunctional catalyst leading to initiation of polymerization at various places on the ring. The basic strength of the catalyst investigated, as determined from the ability to polymerize monomers of decreasing acidity, was as follows: butyl ⋍ phenyl > fluorenyl > cyclopentadienyl.
Crosslinking and degradation in γ‐irradiated poly‐n‐alkyl acrylates
Authors: Burlant W. , Hinsch J. , Taylor C. 
Published: April 2003

AbstractPolymers of methyl, ethyl, n‐butyl, n‐octyl, and n‐cetyl acrylate were γ‐irradiated in vacuo, and the effects of irradiation temperature (−196 to 56°C.) on energy yields for crosslinking and degradation estimated from gel fractions and swelling behavior of the gel. The extent of degradation is independent of polymer structure and reaction temperature, suggesting a molecular chain breaking process. Crosslinking, found to occur predominantly on the alkyl side chain, is independent of temperature above and below the polymer softening point, but is severalfold higher for irradiations above the softening point; these data seem to reflect the importance of segmental mobility of radiation produced polymer radicals in the crosslinking step.
Studies on structure and properties of aromatic polyamides. II. Structural elucidation of poly(m‐xylylene adipamide)
Authors: Yoda Naoya , Matsubara Ikuo 
Published: April 2003

AbstractX‐ray diffraction and infrared spectra of poly(m‐xylylene adipamide) were investigated. On the basis of x‐ray diffraction studies, the twisted form of molecular model for the polymer structure of poly(m‐xylylene adipamide) was proposed which shows the calculated value of 15.2 A. to be an identity period consistent with the observed value from x‐ray diffraction. The assignment of infrared absorption bands were made with the aid of polarization measurements combined with the techniques of deuteration and iodine treatment of the polymer. It was established on the experimental evidences that the band at 725 cm.−1 is assigned to the amide V vibration. The intense bands at 1639, 1545, and 1266 cm.−1 are ascribed to the amide I, II, and III vibrations, respectively. A tentative assignment of the amide VI and VII was also made. The infrared spectra show that the observed dichroism of the amide characteristic bands of the highly oriented specimen is much lower than that of aliphatic polyamides. This is also consistent with the proposed twisted model for the polymer structure of poly(m‐xylylene adipamide).
Chain entanglements and elastic behavior of polybutadiene networks
Authors: Kraus Gerard , Moczvgemba G. A. 
Published: April 2003

AbstractThe role of chain entanglements in determining the stress‐strain properties of polybutadiene networks has been investigated. The number of entanglements was varied by changing the primary molecular weight and chemical crosslink concentration. Networks essentially free of entanglements were prepared by endgroup coupling of carboxy terminated polybutadiene of 5500 molecular weight. Conventional sulfur or peroxide vulcanizates obeyed the Mooney‐Rivlin stress‐strain relation, the constant C2 which represents the deviation from simple kinetic theory diminishing with the time allowed for approaching elastic equilibrium. The constant C2 was found to increase with both the total physical crosslinking and the entanglement contribution to this quantity. The endgroup vulcanizates obeyed the simple kinetic theory of rubber elasticity and approached elastic equilibrium much more rapidly than sulfur or peroxide vulcanizates. The evidence presented suggests that the apparent deviation of elastomeric vulcanizates from the kinetic theory of rubber elasticity resulting in the appearance of the Mooney‐Rivlin C2 term in the stress‐strain relation arises from a slow relaxation process involving the entanglement crosslinks.
The molecular structure of perfluorocarbon polymers. II. Pyrolysis of polytetrafluoroethylene
Authors: Siegle J. C. , Muus L. T. , Lin Tung‐Po , Larsen H. A. 
Published: April 2003

AbstractVacuum pyrolysis of thin samples of polytetrafluoroethylene follows first‐order kinetics with monomer as the only important decomposition product in the temperature range 360–510°C. The rate constant for vacuum pyrolysis is independent of both the melt viscosity and the type of polymer and is characterized by an activation enthalpy of 83.0 kcal./mole and a frequency factor of 3 × 1019 sec.−1. The molecular weight is found to decrease during pyrolysis. A plausible reaction mechanism consistent with these facts involves random chain cleavage, depropagation with short kinetic chain length, and termination by disproportionation. For thick samples the rate of vacuum pyrolysis is controlled by diffusion of monomer. The course of pyrolysis is changed by the presence of monomer or gaseous pyrolysis products. Accumulation of monomer reduces the rate of pyrolysis as measured by the weight loss and results in formation of a waxy product consisting of low molecular weight fluorocarbons.
Cyclopolymerization of diepoxides
Authors: Stille J. K. , Culbertson B. M. 
Published: April 2003

AbstractThe monomer 1,2,5,6‐diepoxyhexane can be polymerized by a variety of catalysts to afford a polymer which has tetrahydropyran recurring units as a result of a cyclopolymerization mechanism. A phosphorus pentafluoride‐water catalyst system gives soluble polymer with inherent viscosities as high as 0.37. The polymerization rates, conversions, and polymer molecular weights are affected both by catalyst to monomer ratio and the amount of water present. A diethylzine‐water catalyst system gives a higher molecular weight polymer with very limited solubility, the soluble portion of which has an inherent viscosity of 0.45. In contrast, 1,2,4,5‐diepoxypentane polymerizes to a completely insoluble polymer in all catalyst systems employed. Samples of poly‐1,2,5,6‐diepoxyhexane prepared with the diethylzine‐water catalyst show a higher degree of crystallinity than those samples prepared with the phosphorus pentafluoride‐water catalyst, as demonstrated by x‐ray patterns and differential thermal analyses.
X‐ray diffraction and infrared spectra studies on the fine structure of rayon improved by high temperature steaming
Authors: Okajima Saburo , Inoue Kimio 
Published: April 2003

AbstractFive samples of rayon containing two high tenacity rayons and three textile rayons of viscose and Bemberg types were heat‐treated with high temperature water or steam (110–210°C.) for a few minutes or seconds, and the change in the fine structure was investigated by means of x‐ray diffraction and small‐angle scattering. An additional study by infared spectra was carried out on cellulose films similarly heat‐treated. The crystallinity increased with increasing temperature and extension of the treating time within the range of less than 10%. Crystallites thicken laterally and grow into those of a higher order. Newly formed crystallites are of cellulose IV. The change is more striking in the high tenacity rayon than in the textile rayons. The remarkable reduction in the degree of swelling is considered to be due partially to such development of crystallinity. No clear conclusion could be drawn as to the contribution of junction points in the amorphous region.
Anionic polymerization of octamethylcyclotetrasiloxane in tetrahydrofuran solution
Authors: Morton Maurice , Bostick E. E. 
Published: April 2003

AbstractA study has been carried out on the base‐catalyzed polymerization of octamethylcyclotetrasiloxane (D4) in tetrahydrofuran solution by means of various anionic initiators. These included potassium hydroxide, sodium and potassium metal and sodium and potassium naphthalene. Tetrahydrofuran was found to have a very marked accelerating effect on the polymerization rate, presumably by increasing the concentration of the silanolate anions. The rates obtained with the potassium metal and potassium naphthalene were even faster than for the KOH, permitting room temperature polymerization in a few hours. The polymerization temperature was not found to affect the equilibrium conversion of monomer to polymer, indicating very similar activation energies for propagation and depropagation. For polymerizations catalyzed by potassium naphthalene, two molecules of catalyst were found to be consumed per chain formed, with one dihydronaphthalene structure included in the chain.
Inhibition of the copper‐catalyzed oxidation of polypropylene
Authors: Hansen R. H. , Russell C. A. , De Benedictis T. , Martin W. M. , Pascale J. V. 
Published: April 2003

AbstractThermal oxidation and copper‐catalyzed thermal oxidation of polypropylene were studied over a range of elevated temperatures. The apparent activation energy for both of these processes, based on t10 induction periods, was 27 kcal./mole. Measurement of the time (t10) required for interaction of 1 g. of polymer with 10 cc. of oxygen was found to be a convenient and expedient technique for estimating the induction period, since this amount of oxygen is sufficient to cause deterioration of physical and dielectric properties of the polymer. In the absence of copper, stabilization of polypropylene comparable to that achieved with polyethylene was observed when antioxidant concentration was increased proportionately to compensate for the larger number of oxidation‐susceptible tertiary carbon atoms in polypropylene. However, it was found that thermal antioxidants, even in high concentration, were ineffective protectants for polypropylene when copper was present. Conventional copper chelators and metal deactivators were, at best, only slightly effective in suppressing oxidation catalyzed by copper and usually were unsatisfactory for a variety of other reasons. Oxamide, however, and particularly its less volatile, high melting, disubstituted derivatives, functioned cooperatively with a wide variety of antioxidant systems and were found to comprise a highly effective and useful family of inhibitors of the copper‐catalyzed oxidation of polypropylene.
An evaluation of column thermal diffusion as a means of polymer characterization
Authors: Taylor David L. 
Published: April 2003

AbstractThe mechanism of polymer fractionation in a Clusius‐Dickel thermal diffusion column was elucidated by a systematic study of the effects of important experimental factors on the separations attainable combined with an analytical description of column operation and recent theories of polymer thermal diffusion. Several polystyrene samples of known molecular weight distribution were studied in toluene and methyl ethyl ketone solvents at varying conditions of temperature gradient (up to 1050°C./cm.), mean temperature (20–45°C.), and concentration (up to 2.4 wt.‐%). The thermal diffusion column was of the concentric cylinder type, equipped with thirty sample ports. The degree of separation of polymer from solvent increased with temperature gradients below 40°C./cm., increased slightly with decreased mean temperature, increased markedly with starting concentration, and was greater in toluene at a given concentration. The degree of fractionation was found to increase rapidly with temperature gradient, and was largely independent of concentration in methyl ethyl ketone but increased strongly with concentration in toluene solutions. These effects were interpreted by means of a theoretical calculation of the influence of both ordinary and thermal diffusion on column behavior in conjunction with an evaluation of the radical concentration gradients. The experimental results are in accord with a recent theory of polymer thermal diffusion which predicts that the thermal diffusion coefficient should not be a strong function of molecular weight. The fractionation effect is apparently governed by differences in ordinary diffusion coefficients. The fractionation was greater for higher molecular weights.
Crystallographic study of xylan from wood
Authors: Horio Masao , Imamura Rikizo 
Published: April 2003

AbstractSome preparations of xylan in the form of transparent membrance or amorphous powder prepared from deciduous woods such as beech and birch show a number of Debye‐Scherrer rings at the irradiation with x‐ray. Of special interest from the crystallographic standpoint is the diffraction pattern of the membrane, which shows an indication of a fiber diagram with the beam parallel to the surface, and this is more obvious when the membrane is stretched to an appropriate extent by rolling. The diagram can be neatly interpreted on the basis of an end surface‐centered rhombic cell whose two axes of the base plane have exactly the ratio of \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt 3 :1\ $\end{document}, within the limit of experimental error. It is assumed that the cell has a trigonal or hexagonal symmetry. The observed reflections are indexed on the base of orthohexagonal unit cell, whose postulated three axes are a = 9.16 A., b = \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt 3 a\ $\end{document}., and c = 15.5 A. (fiber axis). The crystalline lattice of xylan is susceptible to mechanical treatment, heat, and moisture. The crystallinity depends greatly upon the uronic acid content. The diffraction pattern becomes less distinct and the interplanar spacings are enlarged with increasing uronic acid content, until at last the pattern diffuses into a single halo.