bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the formation of dibenzyl ether linkage during curing of resole‐type phenol–formaldehyde resin by DTA and infrared spectroscopy
Authors: Katović Zvonimir 
Published: April 2003

AbstractThe kinetics of formation of dibenzyl ether linkages during cure of resole‐type phenol‐formaldehyde resins was studied by the use of differential thermal analysis and infrared spectroscopy. The activation energy was 21.6 kcal./mole by the Borchard and Daniels method gives and 18.6 kcal./mole by the Kissinger method. For the same process, infrared, which shows a rather good agreement between the two different methods. The heat of reaction, determined from the area under the DTA curve for the corresponding reaction, was found to be 20.2 cal./g.
Graft copolymerization of vinyl monomers in wool fibers
Authors: Negishi Michiharu , Arai Kozo , Okada Sadayuki 
Published: April 2003

AbstractGraft copolymerization of vinyl monomers, mainly methyl methacrylate, in reduced, successively alkylated, or KCN‐Treated wool fibers was performed in the redox LiBr–persulfate system without homopolymer. The reduction gives a striking effect in promoting the graft copolymerization. Methylation or ethylene recrosslinking of the reduced wool, especially the former, decreases the graft‐on remarkably. By the KCN treatment in which the conversion of disulfide to lanthionine bonds occurs, the grafting is decreased in the bromide–persulfate system but promoted in the system with persulfate alone. Methylation or KCN treatment of wool as well as reduction brings about a great increase in the absorption of persulfate. The grafting of the lanthionine‐containing wool in the redox system accompanied by the liberation of bromine might be retarded by the pronounced bromination of monomers over the inhibiting of homopolymerization, because the lanthionine bonds are more stable to bromine than the disulfide bonds. In general, disulfide bonds and the other easily oxidized components of wool may perhaps play an important role in regulating the bromination of monomers and in the graft copolymerization without homopolymer. The molecular weight of graft polymer is decreased distinctly with increasing extent of reduction of wool. From these results, the thiol groups on wool are considered to give predominantly graft centers by the radicalotropy from SO4, OH·, and/or Br·.
Analysis of the Maxwell orthogonal rheometer
Authors: Blyler L. L. , Kurtz S. J. 
Published: April 2003

AbstractAn analysis of the Maxwell orthogonal rheometer for polymer melts is made by using the constitutive equation of White and Metzner. The results indicate that the shear deformation involved is oscillatory and that the storage and loss moduli of the melt may be derived from the measured stress response.
Estimation of kinetic parameters during pyrolysis from linearized DTA traces
Authors: Reich Leo 
Published: April 2003

AbstractA method which empolys the linearization of DTA traces is presented for the estimation of kinetic parameters during polymer pyrolysis. By this method, two DTA traces are used, changes in mechanism with conversion may be detected, and it is not necessary to measure areas prior to evaluating activation energy and reaction order. The method is applied to polyethylene, polypropylene, and polystyrene. The agreement between observed and reported values of kinetic parameters is good. Advantages and disadvantages of the method are discussed.
Interaction of CO2 with a series of detached organic films
Authors: Slabaugh W. H. , Kennedy G. H. 
Published: April 2003

AbstractData obtained from gaseous sorption isotherms of CO2 on eight organic films at three temperatures and three pressures were evaluated for evidences of chemisorption and physical adsorption. The rates of sorption, affected by both temperature and pressure, were analyzed by calculating the perameters of the Elovich equation and those of Barrer's solution of Fick's law for diffusion. Through a consideration of the Elovich parameters, the sorption coefficients, the limiting diffusion coefficients, and the activation energies for diffusion it appears that the rate of interaction of CO2 with these organic films is primarily a diffusion‐controlled process.
Antiplasticization. II. Characteristics of antiplasticizers
Authors: Jackson W. J. , Caldwell J. R. 
Published: April 2003

AbstractBy the incorporation of certain types of additives in bisphenol A polycarbonate, the modulus and tensile strength of the films are increased and the elongation is decreased. This effect is called antiplasticization, because the opposite results are obtained on plasticization—decreased modulus and tensile strength and increased elongation. A study of these additives indicated that antiplasticizers are compounds which are comptiable with the polymer and which (1) contain polar atoms such as halogen, nitrogen, oxygen, or sulfur, (2) contain at least two nonbridged rings, (3) have a glass transition temperature greater than −50°C., and (4) have one dimension less than about 5.5 A. in at least 65% of the length of the molecules.
Antiplasticization. III. Characteristics and properties of antiplasticizable polymers
Authors: Jackson W. J. , Caldwell J. R. 
Published: April 2003

AbstractAntiplasticization is applicable to polymers which contain rigid, polar groups and stiff chains, such as many bisphenol polycarbonates and polyesters, 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol polycarbonates and polyesters, cellulose triacetate, and a commercial poly(sulfone ether). The stiffness, hardness, and tensile strength of these polymers are increased by antiplasticizers, and the elongation, impact strength, and heat‐distortion temperature are decreased. The stiffness of antiplasticized polymers can be further increased by crystallization. A clear, hard, stiff, tough, self‐extinguishing molding plastic with good electrical properties and improved resistance to stress cracking is obtained by antiplasticizing bisphenol A polycarbonate with 20% Aroclor 5460.
Studies on melt spinning. II. Steady‐state and transient solutions of fundamental equations compared with experimental results
Authors: Kase Susumu , Matsuo Tatsuki 
Published: April 2003

AbstractIn the part installment of the present paper, the authors formulated the dynamics of melt spinning by introducing a set of fundamental equations that consist of the equations of heat, force, and material balances. Some steady‐state solutions were also given. Additional steady‐state solutions corresponding to many different spinning conditions for polyester and polypropylene filament yarns consistently show good agreement with experimental results. These steady‐state solutions that give filament cross‐section A (x) and filament temperature t(x) as functions of position x are correlated with yarn qualities: yarn density and birefringence, crystallinity and molecular orientation, are correlated respectively with the speed of Polymer cooling at 100°C. and the maximum tensile stress (F/A)w acting on the filament. A transient solution of the fundamental equations computed on an IBM 1401 machine shows that the filament cross‐section A at the take‐up roll forms a large transient peak after a stepwise increase in the speed vy of cooling air. This agrees with experiments fairly well. The fundamental equations, therefore, clarify the dynamic relations between cooling air speed and yarn weight variations.
Resistance of Valonia cellulose to mercerization
Authors: Okajima Saburo , Kai Akira 
Published: April 2003

AbstractThe mercerization behavior at 20°C. of Valonia macrophysa cellulose of Japanese origin was investigated by x‐ray, moisture regain, and infrared spectrographic methods. The NaOH concentration range necessary for mercerization was 16–20%, which is higher than those required for wood pulp (8–11%), ramie or cotton (11–14%), and even the animal cellulose, Tunicin (14–16%). Treatment with the alkaline solution of the ordinary concentration (17.5%) for 4 days could not mercerize it, and even mercerization with a 19% solution brought about the presence of the reflection from (101)II along with those from (101)I and (101)I after regeneration. Such a high resistance to mercerization of the Valonia cellulose may be due to its larger crystallite size rather than the crystalline content.
Thermal stability of model compounds related to thermostable polymers by pyrolysis‐gas chromatography
Authors: Hirsch Stephen S. , Lilyquist M. R. 
Published: April 2003

AbstractThermal stabilities of eighteen model compounds related structurally to thermostable polymer systems were determined accurately by pyrolysis‐gas chromatography. This approach offers distinct advantages over previously used indirect methods which measure parameters other than actual starting material remaining undecomposed. Both the oxadiazole ring and the aromatic amide link were found to have poor thermal stabilities in comparison with other compounds studied. Since polymers based on these two features have been shown to be valuable for use in air at 200–400°C., the data suggest that oxidation resistance rather than the ultimate in pure thermal resistance should be sought in all‐purpose thermostable materials.
Density–dose behavior of irradiated polytetrafluoroethylene
Authors: Scherer A. E. , Kline D. E. 
Published: April 2003

AbstractThe nature of the room temperature density–dose relationships in polytetrafluoro‐ethylene (PTFE) have been studied over the dose range of 104 to 109 rads. Under various conditions, samples of PTFE were irradiated in combinations of neutron and gamma (reactor and 60Co) radiation fields resulting in density increases up to approximately 5%. For the dose range 105 to 108 rads, the increase in density measured at 0°C. is approximately proportional to the logarithm of the radiation dose. For doses less than about 105 rads, the increase in density appears to be directly proportional to the dose, while above 108 rads the density reaches a maximum and then begins to decrease. By examining the changes in slope and displacement of the curves which occur under various conditions, several effects are discernible. Compared to the effects of γ‐rays alone, the density increase per dose in the 105 to 108 rad region is lower for cases where both neutrons and γ‐rays are present in the radiation field. This may suggest that competing processes are involved in producing density changes. The discernible difference between effects of γ‐radiation and reactor radiation appears to be unique in polymers. The ambient temperature during irradiation and the post‐irradiation heat treatment of the specimens affect the changes in density. For dose rates over the range 0.1 × 106 to 13 × 106 rads/hr., no dose rate effects have thus far been observed. The feasibility of using PTFE for some types of radiation dosimetry has been demonstrated, and its possible usefulness is being investigated.
Effects of interfaces on the thermal degradation of polymer–metal composites
Authors: Schmidt G. A. , Gaulin C. A. 
Published: April 2003

AbstractPrevious studies by Black and Blomquist on the degradative failure of polymer–metal adhesive bonds have shown that composite failure depends largely on the type of metal substrate employed. In the work reported herein, metal powders of high surface area have been employed to maximize the metal–polymer interface. The composite systems studied consisted for aluminum and iron with polycondensates of bisphenol A–diglycidyl ether, phenol–formaldehyde and poly‐2,2′‐(m‐phenylene)‐5,5′‐bibenimidazole. The composites were prepared in the absence of air and thermally degraded in a time‐of‐flight mass spectrometer while the degradation products were continuously monitored from mass 1 to 200. In the polymer and polymer–metal systems investigated, iron accelerated the decomposition of all polymers studied. This was determined by plotting m/e against degradation temperature for the more common mass peaks such as hydrogen and carbon monoxide for the carbon–hydrogen–oxygen‐containing polymer and hydrogen cyanide and ammonia for the carbon–hydrogen–nitrogen‐containing polymer. This technique offers promise in determining the nature of the interface as well as the effect of the interface on polymer degradation.
Physikalische messungen an einem kunststoff als optischem medium
Authors: Lasch Margarete , Rudolph Friedrich , Schreiner Ludwig , Schulze Horst 
Published: April 2003

AbstractVorliegende Arbeit befasst sich mit der Möglichkeit, Diäthylenglycol‐bisallylcarbonat Polymerisate als optisch wirksame Bauelemente zu verwenden. Es wird die Problemtik der Herstellung des Materials und der Formgebung dargestellt. Bei der Diskssion der Eigenschaften des Polymerisates werden Messmethoden und ‐probleme erörtert, z.B. hinsichtlich der Steuerung des Polymerisationsvorganges, der Widerstandsfähigkeit des Polymerisates gegenöber mechanischen Oberflächenbeschädigungen und Klimaein‐ flüssen. Die Arbeit zeigt, dass Diäthylenglycol‐bisallylcarbonat die Reihe der bisher in der Optik verwendeten Kunststoffe in wertvoller Weise ergänst. Bezüglich der Beständigkeit gegen mechanische Oberflächenbeschädigungen wird gezeigt, dass eine Steigerung und Weiterentwicklung möglich ist; das ist gleichzeitig ein Beitrag zum Formulierung und Standardisierung des Begriffes Wischfestigkeit.
Mixing of carbon black and polymer: Interaction and reinforcement
Authors: Boonstra B. B. 
Published: April 2003

AbstractInteraction between carbon black and polymer starts during the mixing process; a primary agglomerate is formed, the composition of which is dependent upon the structure. The important carbon black properties are surface area, specific activity, structure (void, volume, anisometry), and porosity of the particles. On heat treatment of black at 3000°C., it loses its sites of high specific activity. Structure and specific activity determine incorporation time and further dispersion. During mixing, bound rubber is formed which is used as a measure of specific surface activity. In the final vulcanizate, the filler–polymer interaction is evident in reduced swelling in solvents (benzene, chloroform, cyclohexane,) etc. Below a certain critical degree of swelling, the percentage swelling is no longer dependent upon the amount of filler in the vulcanizate. Graphitized black vulcanizates exhibit in all solvents the same degree of swelling as the unfilled vulcanizate. This phenomenon is explained by the assumption of mobile adsorption of rubber chains on the carbon black surface. In untreated blacks the mobility on the surface is limited by sites of high energy of adsorption. In graphitized blacks such sites are no longer found, and swelling is unhindered by the presence of black. Reinforcement is explained by the more homegeneous distribution of tension between molecular chains due to slippage on the carbon surface.
Effect of temperature on the permeation of water through propylene glycol monoacrylate hydrogel
Authors: Refojo Miguel F. 
Published: April 2003

AbstractTransparent propylene glycol monoacrylate (PGMA) hydrogels become reversibly opaque when the temperature is rapidly increased to above 30°C. Water permeation, driven by a hydrostatic pressure difference through three PGMA membranes differing in water content and thickness was determined at several temperatures. At room temperature, the permeability to water is relatively low (less than 10 × 10−16 cm.2) and is dominated by a diffusion mechanism. When the temperature is suddenly increased, the water permeation rises quickly (up to fifteen times or more depending on the temperature), and viscous flow predominates over diffusive flow. The rapid flow slows down after some time at the same temperature, or on lowering the temperature, and may be interpreted as caused mainly by the reversible transformation of the membrane from the heterogeneous to the homogeneous form. When the temperature is increased gradually, the permeability of the membrane is in the same order of magnitude as that found at room temperature, because no phase separation occurs. The permeation of water decreased in successive measurements made under the same pressure gradient. An increase of the pressure difference also resulted in decreased permeation, indicating that water was pressed out of the gel. Dehydration of the gel caused by increases in temperature (exothermic swelling) and in pressure and changes in the viscosity of water with temperature are some of the factors which are considered in the interpretation of the results.
Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions
Authors: Paul D. R. 
Published: April 2003

AbstractThe reversible gelation of acrylonitrile–vinyl acetate copolymers in concentrated solutions has been studied with the use of various solvents. These concentrated solutions gel or become rigid with time, but they become fluid again when heated above a certain temperature called the gel melting point. A technique involving the use of mercury drops was developed to measure this transition. This temperature was evaluated as a function of solids level, water content in the solvent, and the amount of vinyl acetate in the copolymer, dimethylacetamide being used as the solvent. Four other solvents were used to obtain limited data. Gel melting was studied further by differential thermal analysis and shear modulus measurements. The results are discussed in terms of network formation and solubility. The x‐ray diffraction results imply that the tie points of the gel are crystalline.
Colloidal macromolecular phenomena. Part II. Novel microcrystals of polymers
Authors: Battista O. A. , Erdi N. Z. , Ferraro C. F. , Karasinski F. J. 
Published: April 2003

AbstractColloidal microcrystalline cellulose, introduced in 1961, now is a successful commercial product with growing world‐wide markets. This paper describes some major findings of our continuing research to convert fibrous or fiber‐forming polymer systems into new colloidal microcrystalline physical states without going through a homogeneous molecular solution phase. Several novel microcrystalline colloidal products from the following natural and/or synthetic polymeric raw materials are described and compared for the first time: cellulose, amylose, collagen, nylon, and chrysotile mineral silicates. Many previously unpublished electron micrographs are presented. These products demonstrate a new and growing field of colloidal microcrystalline polymer science. They open up increasing opportunities for new polymer products based on the original concept, namely, the unhinging of polymer microcrystals from their natural or synthetic network and then by appropriate mechanical energy, releasing them as discrete, submicron colloidal polymer microcrystals dispersed in various liquid media to form unique gel systems, or reaggregated in the dry state to form porous colloidal particles.
Dielectric behavior of some polar high polymers at ultra‐high frequencies (microwaves)
Authors: Frosini Vittorio , Butta Enzo , Calamia Mario 
Published: April 2003

AbstractThe dielectric behavior of different polar high polymers at ultra‐high frequencies has been investigated by means of a dielectrometer, suitably modified to permit measurements at different temperatures. Experimental measurements were made at about 9 × 109 cps over the temperature range of −150 to 200°C. for polyoxymethylene, polythiomethylene, poly(3,3′‐chloromethyl)oxetane (Penton), polycarbonate of 4,4′‐dioxydiphenyl‐2,2′‐propane (Makrolon), poly(vinyl alcohol), poly(vinyl acetate), poly(vinyl chloride), vinyl chloride–vinyl acetate copolymer, and two ABS plastics, type B (blend) and type G (graft). On comparing the dielectric behavior of the examined materials at ultra‐high frequencies with the corresponding ones determined at low or at radiofrequencies, it is observed that, in the microwave region, all relaxation peaks, either connected with cooperative motions in main chain (primary processes) or with local motions in the backbone or in side chains (secondary processes), usually observed at lower frequencies, tend to disappear; the corresponding relaxation effects, however, manifest themselves through a progressive increase of losses with increasing temperature, which is particularly marked above the glass transition temperature Tg. The latter transition, in spite of the very high frequency, is easily distinguished, in most cases, by the sudden change of slope in the tan δ versus temperature curve which accompanies its onset. This is explained on the basis of the very wide distribution times of molecular relaxation processes in polymers and the increase in strength of the secondary relaxation effects, which is verified at Tg, as a consequence of the increased kinetic energy of macromolecules and of the larger free volume for orientation of side chains. Each case is discussed separately and the experimental results interpreted on the basis of the molecular structure and chain mobility of the examined polymers.
Kinetic study on the alkaline degradation of cotton hydrocellulose
Authors: Haas Donald W. , Hrutfiord Bjorn F. , Sarkanen K. V. 
Published: April 2003

AbstractThe kinetics of alkaline degradation of cotton hydrocellulose were determined in 5% NaOH at various temperatures. An activation energy of 24 kcal./mole was found for the endwise degradation reaction, while that of termination to a stable m‐saccharinic acid endunit is 32 kcal./mole. Consequently, the DPn of the degradable chain length is highly dependent on the reaction temperature, being 1000 at 65°C. and 140 at 132°C. At lower temperatures, the majority of degrading chains terminate to a normal reducing endgroup at the crystalline–amorphous transition region. From the data, the DPn of cellulose chain segments participating in the amorphous regions of the original cotton fibril was calculated to be 143. This result strongly supports the classical micellar fibril structure over the folded model proposed by Manley.
Preparation and fabrication of aromatic polyimides
Authors: Dine‐Hart R. A. , Wright W. W. 
Published: April 2003

AbstractAromatic polyimides were prepared from pyromellitic dianhydride and a number of aromatic diamines. The effect of certain variables on the polymerization to, and the degradation of, the intermediate polypyromellitamic acids was studied, and a previously unrecorded reaction intermediate was isolated and identified. From these studies the conditions necessary to obtain high molecular weights were defined. Techniques were developed for the fabrication of satisfactory films and moldings.
Function of sheets of cellulose chains in swelling reactions on cellulose
Authors: Warwicker J. O. , Wright Ann C. 
Published: April 2003

AbstractAn x‐ray investigation of the products formed by the action of caustic soda on different samples of cellulose and those formed on the decomposition of these products by aqueous reagents and alchols shows that the fundamental reacting unit is a sheet of cellulose chains, and not individual cellulose chains. Although the caustic soda can affect the relative dispositions of the chains within these sheets to some extent, it cannot separate the chains, and the products then depend on the aggregation of the cellulose sheets with or without other molecules between them. Such aggregation leads to variables products whose x‐ray diagrams can, however, show distinct reflections and be mistaken for those from more precise crystal structures. It is, therefore, important in swelling reactions to take into account the ability of the swelling agent to modify the cellulose sheets and the mode of decomposition of the complexes formed on swelling. Thus swelling with caustic soda cannot be taken as typical of all aqueous swelling reagents in its reaction towards cellulose, and the possibility with other reagents of finding cellulose I, instead of cellulose II, after a series of swelling reactions must be taken into consideration.