bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polypeptide hormones and lipid monolayers
Authors: Pak Charles Y. C. , Kafka Marian S. 
Published: June 2010

AbstractThe monomolecular film of monooctadecyl phosphate (mOP) spread at an air‐water interface was employed to elucidate the nature of the interaction between peptide hormones and the cell membrane. First, the effect of peptide hormones on the uptake of calcium ion (Ca++) by the monolayer was examined from the emission of45 Ca radioactivity through the monolayer. Insulin inhibited the initial uptake of Ca++ and facilitated the release of adsorbed Ca++. These effects were partially or completely lost with insulin analogs. Vasopressin and oxytocin inhibited the adsorption of Ca++. Vasopressin facilitated Ca++ release, whereas oxytocin did not. Thyrocalcitonin profoundly inhibited Ca++ uptake, but facilitated only slightly the release of Ca++. Parathyroid hormone had negligible effect. The molecular basis and the biological significance of these results are discussed. Secondly, the effect of peptide hormones on the transport of water through the mOP monolayer was examined. Ca++ increased the specific resistance to evaporation of water. In the presence of Ca++, insulin and vasopressin lowered the resistance to evaporation (or increased the trans‐port of water). This effect of the hormones could not be accounted for entirely by the inhibition of Ca++ uptake.
Monolayers of polyorganosiloxanes on water
Authors: Noll W. , Steinbach H. , Sucker Chr. 
Published: June 2010

AbstractLinear organosiloxanes with various substituents differ in their spreading velocities and with respect to the film structure formed on aqueous substrates. The material investigated allows a distinction between siloxanes in which the molecules placed on the subphase in helical form become oriented on the surface of the water to form “spreading chains” and siloxanes in which this is not the case. It is believed that hydrogen bridging is responsible for the orientation effect.Within the first group, a distinction can be made between polymers which on strong compression are lifted off from the water and can be returned to the helical form, and those in which due to great hydrophilicity of the substituents release of “dry” spreading chains from the water can not be achieved. Methyl‐substituted siloxanes, among them especially the dimethyl‐ and methyl‐H‐siloxanes, show quick spreading and good orientability. This may explain why these siloxanes play such an important role since the beginning of silicone technology up to the present day as interfacially active substances. But this behavior is not representative for organosiloxanes in general.The structure of the siloxane skeleton seems to have no decisive influence on the spreading phenomena. Branched or crosslinked methylsiloxanes behave similar to the linear ones and form also, by and large, monomolecular films.Hydrate phases, i.e., mixed phases of the spread substance and the subphase, play an important part in the interpretation of the force/area (F/A) isotherms.
Surface‐polymerization of tetrafluoroethylene on fluorine‐activated metal substrates
Authors: Toy Madeline S. 
Published: June 2010

AbstractMetals form protective metal fluoride films upon exposure to fluorine. The utilization of the metal fluoride films as catalysts for surface polymerization of tetrafluoroethylene is described. The process consists of a two‐step synthesis: (1) gas phase fluorination of a metal sample to produce a fluoride film on the metal surface and, (2) gas phase polymerization to form a polymeric coating. The fluorocarbon films formed on the metal substrates by the Toy process are fairly adherent, continuous and flexible, except that it is somewhat porous depending on the conditions of fluorination, polymerization, metal compositions, and metal surface preparations. The possible mechanisms of surface‐polymerization are discussed.
Chemo‐rheology of curing in structural adhesives I: Epoxy‐phenolic systems
Authors: Kaelble D. H. , Cirlin E. H. 
Published: June 2010

AbstractThermosetting adhesives undergo a chemo‐rheological transition during cure which transforms the material from an initial compliant bonding state to a rigid high strength holding state. The results of combined application of differential scanning calorimetry (DSC) and Instron thermomechanical analysis (TMA) in a study of reaction kinetics and physical state changes in epoxy‐phenolic adhesives are reported. A special reduction of DSC data isolates the apparent heat of polymerization ΔHp and activation energy E* of curing. Analysis of a repetitive extension‐recovery cycle, at low strain amplitude, isolates the temperature‐time effects of curing upon the tensile modulus E, the work of deformation WT = WL + Ws, and the work ratio WP/Ws = work loss/work stored per cycle. Correlated results of DSC and TMA analysis of two epoxy‐phenolic adhesives isolates the effects of metal fillers upon both the curing kinetics and mechanical response of the cured material.
Chars produced from cellulose under various conditions of thermal decomposition
Authors: Miller Bernard , Gorrie Thomas M. 
Published: June 2010

AbstractAn experimental study has been performed to identify the controlling conditions when self‐generating flames move through and transform flame‐retardant treated and untreated cotton fabrics. The approach has been to compare the chars formed by flames with those produced by induced (nonflame) thermal decomposition under known conditions of temperature and environment. Char comparisons were made mainly through internal reflection infrared spectroscopy. Considerable variations were found among chars formed by flames moving in different directions in space, corresponding to differences in the maximum temperatures and degree of contact with oxygen experienced by the materials during burning.
The effect of liquid anhydrous ammonia in the structure and morphology of cotton cellulose
Authors: Lewin Menachem , Roldan Luis G. 
Published: June 2010

AbstractThe effect of liquid ammonia on cotton fabric was studied using x‐ray diffraction (XRD) and electron microscopy. A phase diagram is presented describing the relationship between disordered cellulose, cellulose I, and cellulose III. The transition from cellulose I to III proceeds through the liquid ammonia. Cellulose III is obtained upon drying the ammonia‐cellulose without the presence of water. Treatment of the cellulose III or of the ammonia‐cellulose with water brings about the formation of cellulose I. The degree of crystalline order achieved in water is enhanced by heating, which is consistent with a glass transition temperature between room temperature and 100°C. The cellulose III crystallites obtained are much smaller than those of cellulose I,16‐23Åas against 50‐80ÅThe interaction of ammonia with cotton cellulose is faster than with other swelling agents, such as ethylamine. The penetration of ammonia into the secondary wall of the cotton fiber is not only along the concentrical rings, as is the case with water, but also radially across the rings.Prolonged soaking in water increases the crystallite size with simultaneous rejection of swelling water.
Folding chain model and annealing of cellulose
Authors: Chang Martin 
Published: June 2010

AbstractA folded chain model of cellulose fine structure has been developed, together with a new hypothesis on cellulose “weak links”. Essentially, single cellulose molecules are folded back and forth in the (101) plane to form “platellites” which are the smallest physical and structural unit of crystalline cellulose. The average fold length in the platellites corresponds to the levelling‐off DP. The glucosidic bonds at the folds are weak links due to a loop conformation of the chain.The morphological transition of cellulose during mercerization has been examined with reference to the folding chain model. It is envisaged that the transition is the result of a partially restricted annealing of the cellulose crystals under the action of the swelling agent. Thus, low‐temperature annealing of cellulose shortens the fold length of the molecule and results in the well known mercerization process; high‐temperature annealing, on the other hand, generates at least a partial reversal of the mercerization. This hypothesis is found to agree very well with the known facts in the literature and is further supported by some experimental evidence.
Some properties of water‐soluble hydroxyalkyl celluloses and their derivatives
Authors: Klug E. D. 
Published: June 2010

AbstractThe effect of increasing the substitution of water‐soluble hydroxyethyl cellulose (HEC) and hydroxypropyl cellulose (HPC) is to decrease their affinities for water. This is consistent with data given on the cloud point, salt tolerance, surface tension of aqueous solutions, and solubility in organic solvents, all as functions of MS.Ionizable substances have a great influence on temperature‐solubility behavior of the hydroxyalkyl celluloses. If the ions are present as inorganic salts in solution, they cause hydration of the polymer to decrease with some loss in solubility. In the case of HPC, ions derived from substituent groups, present in small amounts, improve hot water solubility and impart unusual viscosity‐temperature behavior.Mechanical properties of HEC film and thermoplasticity of HPC are functions of the extent of substitution rather than the hydrophilicity.
Kinetics of crystallization of polyamide 6 from the glassy state
Authors: Kozlowski Wojciech 
Published: June 2010

AbstractGlassy polyamide 6 was obtained by quenching the melt in liquid toluene at 210°K. On the DSC thermogram of such a polyamide a small endothermic peak of glass transition at 310°K, and an exothermic peak at 325°K of cold crystallization are observed (both temperatures were calculated by extrapolation to zero heating rate).The kinetics of cold crystallization was investigated in the range 321‐339°K by DSC technique using three different methods of measurement: 1) standard isothermal, 2) isothermal by Miller, and 3) nonisothermal by Ozawa. The data obtained from 1 and 2 were analyzed by the simple Avrami equation, and from 3 by a modified equation. It was confirmed that the exponent n is not constant; in the range up to 328°K it has an average value of 2.2, and then varies with the rise in crystallization temperature. Unfortunately, the mechanism of the variation of n is not known and this prevents the calculation of the crystallization rate from the nonisothermal dynamic data.Thus, an assumption was made that crystallization follows first‐order kinetics: K and t0.5 for different temperatures were calculated; the Arrhenius function was plotted; and from it the activation energy of 69.7 kcal/mole was estimated.
The structure of solutions and films of cellulose acetate
Authors: Buntjakov A. S. , Averyanova V. M. 
Published: June 2010

AbstractThe optical rotatory dispersion of solutions of cellulose acetates with different degrees of acetylation in a series of solvents is studied. Increasing the degree of esterification of the cellulose acetate results in a shift of the optical rotation to more negative values. These changes have been explained on the assumption of various contributions to the optical rotation from hydroxyl and acetate groups. The cellulose acetate solutions studied fall into two groups. Solutions in acetic acid, dimethylformamide, nitromethane, and acetone give anomalous curves, whereas in methylene chloride, chloroform, tetrachlorethane, and dioxane normal curves of rotatory dispersion are produced. Attempts to fit the results by calculations based on a one‐term Drude equation proved all the curves to be more complex. The influence of solute is probably due to specific interaction with hydroxyl and acetate groups and fixing of rotatory isomers of the side groups. A complex pattern of the rotatory dispersion curves is dictated by the contributions from asymmetric carbon atoms associated with hydroxyl and acetate groups having a different rotatory dispersion. Polymer‐solvent interaction affects the film structure. Crystalline films are obtained from cellulose acetate solutions (AcOH = 60.3%) with anomalous dispersion while solutions with a normal dispersion give amorphous firms.
Morphological changes in nylon 6 and effect on mechanical properties. II. Dynamic mechanical properties
Authors: Hoashi Koji , Andrews Rodney D. 
Published: June 2010

AbstractDynamic mechanical measurements were carried out on nylon 6 film treated with heat and swelling agents to produce changes in the crystalline morphology. The original smectic hexagonal crystal form was changed by heat treatment and phenol treatment to an unoriented and oriented α‐crystalline form, respectively, and by I2/KI treatment to a preferentially oriented γ‐crystalline form. The behavior of the αa mechanical loss peak located at about +70°C was investigated in most detail. This peak was independent of frequency on the low‐temperature side of the peak but markedly frequency‐dependent on the high‐temperature side. The low‐temperature side of the peak probably represents a thermodynamically controlled “melting” or bond‐breaking process which frees molecular units to participate in a viscoelastic relaxation process which is the controlling factor in the high‐temperature side of the peak. Frequency‐temperature superposition of data from the high‐temperature side of the peak gave shift factor values which showed two straight‐line regions in the Arrhenius plot for the specimens containing some smectic hexagonal form, and a single straight line in the other cases. Activation energy values obtained were 30–50 kcal. The αa peak split into two components with an increase in absorbed phenol, indicating that two loss mechanisms corresponding to two noncrystalline phases (one amorphous and one more highly ordered or hindered) are involved.
Triplet energy transfer in solid solutions and films of poly(vinyl carbazole)
Authors: Klöpffer Walter , Fischer Dieter 
Published: June 2010

AbstractMonomeric carbazole derivatives show phosphorescence in the wavelength region between 400 and 500 nm. Poly(vinyl carbazole) (PVCA) in dilute frozen solutions also shows phosphorescence in this region and, in addition, delayed fluorescence owing to triplet‐triplet annihilation. The latter depends on the molecular weight of the polymer, high‐molecular weight samples showing very strong delayed fluorescence, whereas in low‐molecular weight products phosphorescence prevails.The phosphorescence of solid PVCA is governed by traps. Comparison with low‐temperature fluorescence and measurement of decay times suggest that two traps are important for both singlet and triplet excitons. The excimer‐forming site is one of them. The maximum of triplet excimer emission is at about 500 nm, the decay time is 7.9 ± 1 sec (compared to 410 nm and 43 nsec in the singlet system). The second trap emits in the same wavelength region, decay time 1.4 sec, and corresponds to a second intrinsic singlet trap emitting at 380 nm (decay time 12 nsec). The range of the triplet exciton at 77°K is drastically reduced by these traps, as in the case of the singlet system.
Study of the reaction of oxyradicals with antioxidants on synthetic zeolites
Authors: Rychlý J. , Lazár M. , Pavlinec J. 
Published: June 2010

AbstractThe ESR method has been used for the study of the inhibition effect of some antioxidants on polymerization of methyl methacrylate proceeding in the surface of synthetic faujasite of the Na Y type. From equilibrium levels of trapped radicals the inhibitor efficiency has been elucidated as follows: hydroquinone > diphenylamine > 2, 6‐di‐tert‐butyl‐4‐methylphenol > pyrogallol > N‐phenyl‐2‐naphthylamine > 1‐naphthol.Mechanism of hydroperoxides decomposition on zeolite surface has been discussed as well.
THE radical reactivity of some bisphenol antioxidants
Authors: Simonyi M. , Kardos J. , Tüdös F. , Pospíšil J. 
Published: June 2010

Abstract4,4′‐isopropylidene‐bisphenol and some of its methyl and tert‐butyl derivatives were studied by inhibiting the radical polymerization of vinyl acetate. Alkyl groups in the bisphenol increase the radical reactivity. The substituent effect is significantly additive, i.e., the individual groups contribute independently to the reactivity. As a contrast, in the case of 2, 6‐tert‐Bu2 substitution a steric effect emerges. The analogy between the reactivities of phenols and bisphenols is remarkable.
Thermooxidative stability of copolymers having polyconjugated fragments in the main chain of macromolecules
Authors: Berlin A. A. , Gherassimov B. G. , Ivanov A. A. 
Published: June 2010

AbstractCopolymers have been synthesized which consist of polyazophenylene (1‐50%) and polyisoprene (or polystyrene) fragments. Synthesized copolymers have some specific properties caused by intermolecular interaction of polyconjugated blocks. The inhibiting activity of polyazophenylene blocks of copolymers was ascertained considerably to surpass the inhibiting effect of polyazophenylene addition to corresponding homopolymers in the processes of thermal destruction and oxidation of polymers. This is reflected in the decreased rate of oxygen absorption at constant temperature, in the decreased rate of weight losses in isothermal conditions, and in the increased temperatures of 50% weight losses of copolymers by the dynamic thermogravimetric analysis. The increased inhibiting activity of polyconjugated blocks is explained by their improved compatibility and distribution in polymer substrate and by the increase of conjugation degree owing to intermolecular interaction of polyconjugated blocks.
The diffusion time lag in polymer membranes containing adsorptive fillers
Authors: Paul D. R. , Kemp D. R. 
Published: June 2010

AbstractImmobilizing adsorption of diffusing penetrants is known to occur in a number of polymer membrane systems. It will cause very large increases in the diffusion time lag but will have only minor effects on the steady‐state permeation. This effect may be troublesome in that considerable errors may be incurred when the time lag method is used to analyze quantitatively the sorption and diffusion behavior in such systems. On the other hand, this effect can be utilized in a beneficial way to design very effective protective coatings, packaging materials, timed release mechanisms, etc. for special situations. The time lag in this case can be predicted very accurately from a theoretical result reported previously. This point is demonstrated here by comparing theoretical predictions with experimental time lag data obtained for various gases in a model membrane synthesized by dispersing highly adsorptive molecular sieves into silicone rubber. The agreement is excellent.
The effect of solutes on the pervaporation of water‐methanol mixtures through cellophane
Authors: Misra Ashok , Kroesser F. William , Shelden Ronald A. 
Published: June 2010

AbstractThe effects on permeation rate and permeate composition of the addition of sodium formate to mixtures of methanol and water pervaporating through cellophane have been examined. In general, the addition of the salt increased the water content of the permeate, but decreased the total rate of pervaporation and that of each of the components. The effect was greater in water‐poor feeds. The effect of the salt on the permeate composition was opposite to the expected effect on the relative volatility of the feed components. The possible causes of this “solute effect” are discussed.
Polymerization of capryllactam initiated with acids under anhydrous conditions
Authors: Puffr R. , Šebenda J. 
Published: June 2010

AbstractAn investigation was made of the kinetics of polymerization initiated with carboxylic acids of different acidity, namely, caprylic, p‐fluorobenzoic, and o‐chlorobenzoic acids at 220–280°C and also with capryllactam hydrochloride for comparison. The polymerization proceeds without an induction period, is little dependent on the acidity of the initiator, and can be expressed in terms of a simple kinetic equation: ‐dL/dt = k I0aL. If carboxylic acids are used for initiation, the exponent a is 0.82, the pre‐exponential factor and the activation energy of polymerization is 1.85 × 1012 and 30 kcal/mol respectively. In the discussion, the polymerization of capryllactam is compared with the polymerizations of caprolactam and laurolactam.
The free radical bulk polymerization of ethylene at low temperatures
Authors: van der Molen Th. J. 
Published: June 2010

AbstractA method is presented to recover the polymer formed in the free radical bulk polymerization of ethylene as a powder rather than as a melt. The paper mentions several advantages of this new approach, which has been used in a study on the production of medium and high density polyethylene with the aid of radical initiators at temperatures below the melting point of polyethylene (suspension bulk polymerization). The method of preparing products with a very high stiffness comparable to that of homopolymers made by the Ziegler process is, in principle, also applicable at polymerization termperatures above the melting point of polyethylene, provided (meth) acrylamide is employed as a comonomer.
Anionic polymerization of caprolactam. XLVII. Effect of polymerization conditions upon the keto groups content in anionic polycaprolactam
Authors: Čefelín P. , Stehlíček J. , Šebenda J. 
Published: June 2010

AbstractIn the anionic polymerization of ε‐caprolactam, approximately 0.5–1 keto group is formed per one activator molecule very quickly at 250–280°C. The concentration of the keto groups in the polymerizate depends on the initial concentrations of the catalytic components, the temperature, and the polymerization time. At a low effective basicity, the majority of keto groups originates during the first minutes, whereas at higher basicities most of the keto groups are formed in the later stages of the process. In polymers prepared in the presence of sodium caprolactam and N‐benzoylcaprolactam there occurs transitional branching and the primary branched chains become linearized during extended heating.
On the polymerization of acetylenic derivatives. XIX. Synthesis of poly (α‐ethynyl naphtalene) and its electrophysical properties
Authors: Simionescu Cr. , Dumitrescu Sv. , Percec V. , Negulescu I. , Diaconu I. 
Published: June 2010

AbstractThe polymerization of α‐ethynyl naphtalene, (EN) with Ziegler soluble catalysts and tertiary phosphine‐transition metal complexes has been investigated.The following catalysts, MeII(dmg)2. 2X/Al(R)2R′, (where MeII = Fe, Ni; dmg = dimethylglyoxime; X = pyridine, Py, or NH3; R = C2H5, i ‐ C4H9 and R′ = C2H5, i‐C4H9, Cl), specific to cis polymerization of acetylenic monomers and (PPh3)a. MeXb (where Ph = C6H5; a = 2,3; Me = transition metal of group VIII; X = Cl, Br, I, SCN and b = 2, 1) specific to trans polymerization of these monomers have been used.The influence of some reaction parameters (i.e., polymerization temperature, temperature of the first catalyst‐monomer contact, catalyst nature and concentration, etc.) have been followed and two different mechanisms of EN with the said catalysts were proposed.The obtained polymers were analysed from the point of view of their structural and electrophysical properties.
Polymerization by high electric fields: Field emission and field ionization
Authors: Schnabel Wolfram , Schmidt Werner F. 
Published: June 2010

AbstractThe polymerization of styrene (St) and α‐methylstyrene (α‐MSt), initiated by high electric fields, has been investigated by using an electrode assembly comprised of a tip (sharp edge) and a flat counter electrode. Maximum specific yields obtained under field ionization (FI) conditions amount to ca. 6000 kg/Faraday (St) and 3000/Faraday (α‐MSt), respectively, and are higher than under field emission (FE) conditions: 1500 kg/Faraday (St) and 100 kg/Faraday (α‐MSt), respectively. In the case of FE initiated polymerization polymer is formed via a cationic mechanism. Part of the polystyrene formed under FE conditions is generated via free radicals. Evidence is obtained by gel permeation chromatography and scavenger experiments. A mechanism via free cations could be established for the FI initiated polymerization.