bluuebunny/crossref_metadata_2025_split huggingface dataset:
Boric acid esters as secondary plasticizers for poly (vinyl chloride)
Authors: Potnis S. P. , Khanolkar A. G. 
Published: June 2010

AbstractIn addition to the primary plasticizers which are essential for giving the required ease of processing to and improving desirable mechanical properties of polyvinyl chloride (PVC) compounds, secondary plasticizers also play a significant role in confering specific properties to PVC. It was from this point of view that the boric acid esters were evaluated in PVC compositions. Because of the limited compatibility of boric acid esters with PVC by themselves, their use could be recommended only as secondary plasticizers. In the present paper various boric acid esters prepared in this laboratory [S. P. Potnis and A. G. Khanolkar, Popular Plastics, 15, 20 (1969)] have been evaluated for their performance in PVC compounds, and results obtained indicate that the monomeric and alicyclic esters of boric acid could be used with definite advantage and improve such properties as electrical resistance, heat stability, and in some cases even the mechanical properties.
Long chain branching in poly(vinyl chloride)
Authors: Small K. W. , Yearsley F. , Greaves J. C. 
Published: June 2010

AbstractThe intrinsic viscosity [η]‐weight average molecular weight Mw, relation has been studied for fractions of a range of vinyl chloride homopolymers prepared at 40–80°C in aqueous suspension. In addition to curvature of the log [η]‐log Mw plots for Mw > 2 × 105, at constant Mw a slight but definite trend to lower [η] as polymerization temperature is increased was also observed. Both these effects are ascribed to long chain branching due to an increasing incidence of intermolecular chain transfer as polymerization temperature is increased. Limited examination of poly(vinyl chloride) prepared by emulsion polymerization indicates, by the same criterion, a greater incidence of branching than found in poly(vinyl chloride) prepared at the same temperature by the aqueous suspension process. It is concluded that no single correlation of the Mark‐Houwink type can be expected to apply to vinyl chloride homopolymers prepared over a range of conditions.
Some problems of the thermal degradation of poly(vinyl chloride)
Authors: Kelen T. , Bálint G. , Galambos G. , Tüdös F. 
Published: June 2010

AbstractThe effect of hydrogen chloride on the thermal degradation of poly(vinyl chloride) was studied in dibutyl‐sebacate solution. It was found that hydrogen chloride exerts no catalytic effect at these conditions.The assumption of hydrogen chloride readdition to the double bonds formed is forwarded as a factor lowering the average length of polyenes. The possible mechanism of stabilizing action of metal soaps is discussed on this basis.
Investigations on the stabilization of poly(vinyl chloride) by metal soaps
Authors: Braun D. , Hepp D. 
Published: June 2010

AbstractThe degradation of mixtures of poly(vinyl chloride) (PVC) and metal soaps was investigated in solution as well as in bulk in an inert atmosphere at 180°C. There are marked differences between stabilized and unstabilized PVC in the dehydrochlorination and in the distribution of the length of the resulting polyene sequences in the polymer. Cadmium octoate retards the dehydrochlorination and causes a shift of the sequence length distribution towards shorter polyene sequences. Thermal dehydrochlorination of stabilized PVC is more strongly retarded in solution than in bulk. Furthermore, there is a more pronounced shift in the sequence length distribution towards shorter polyene sequences when PVC‐stabilizer mixtures are degraded in solution rather than in bulk. The formation of primarily short polyene sequences that absorb in the ultraviolet range is attributed to a direct reaction between stabilizer molecules and PVC in which an acid residue of the stabilizer is exchanged with a “labile” chlorine atom of the polymer chain.
Study of the degradation of poly(vinyl chloride) compounds by dielectric spectroscopy
Authors: Hedvig Peter 
Published: June 2010

AbstractA continuously recording dielectric spectrometer was constructed to investigate the effects of degradation on the dielectric spectra and ac conductivities of poly(vinyl chloride) (PVC) compounds. Dielectric spectra were found to be affected by the thermal history of the sample. The elimination‐type degradation in hard PVC and in plasticized PVC compounds could be kinetically studied by recording ac conductivity as a function of reaction time. The method was found to be useful for studying the efficiency of stabilizers in a simple way. Changes in the physical structure during the course of degradation could be measured by observing shifts and distortions of the Tg‐dispersion signals.
Peculiar behavior of blood at solid interfaces
Authors: Vroman Leo , Adams Ann L. 
Published: June 2010

AbstractAdsorption of proteins out of normal and afibrinogenemic blood plasma onto oxidized silicon crystal slices and glass was studied with the recording ellipsometer and by other means. Adsorbed matter was identified by its ability to adsorb specific antibody or to function in blood clotting. Our previous data suggest that fibrinogen as well as factor XII (the protein thought responsible for surface activation of clotting) are adsorbed first. If the plasma was not previously activated, it converts this fibrinogen, and then, in the presence of unactivated factor XII, it removes some. Both conversion and removal are retarded by previous activation of the plasma, or by lowering its concentration or temperature. Blood platelets (the elements that start thrombosis in vivo) adhere most to films on glass that contain unconverted fibrinogen. Present data suggest that plasma from a patient totally lacking plasma fibrinogen, had all properties of normal plasma when fibrinogen was added. Fibrinogen in bulk or pre‐adsorbed state neither helped nor hindered adsorption of factor XII activity. After prolonged contact of normal plasma with an activating interface, adsorbed fibrinogen could be recovered by elution. Readsorption was then followed by reconversion.
Compression mechanics of polymer monolayers
Authors: Yin T. P. , Wu Souheng 
Published: June 2010

AbstractA theory based on a simple buckling mechanism has been developed to describe the deformation and rupture mechanics of a polymer monolayer. It assumes that the closely packed monomer units are forced to buckle in successive pairs under compression. When the protruding angle of the rupture site reaches 90°, the monolayer collapses. This model is found to accommodate the essential features of compression isotherms of polymer mono‐layers in the condensed region (below the closest packing area at zero surface pressure) up to and beyond the collapse point. The stress‐bearing capacity of the interface is greatly influenced by the ratio of cohesion to adhesion. The compression isotherm may take either a positive or a negative slope beyond the collapse point, depending on whether adhesion is greater or smaller than cohesion.
Air infrared spectroscopy study of the epoxy‐cellulose interface
Authors: O'Brien R. N. , Hartman K. 
Published: June 2010

AbstractSome aspects of the adhesion of paint to wood were studied by the selection of a well characterized substance to take the place of wood, in this case, cellulose and a well‐known polymer, an epoxy system, which is frequently used as the polymeric constituent of a modern paint. Attenuated total reflectance (ATR) infrared spectra of some wood surfaces from which the correlation with the cellulose ATR spectra can be seen, have been reported [1]. The synthetic spectrum of cured epoxy system and cellulose was prepared by placing a cast and cured epoxy system sheet on one side of a KRS5 internal reflection plate and compressed, reconstituted cellulose on the other side. This spectrum was compared with that of a cast and cured cellulose‐epoxy system mixture. The OH‐stretching band (3350 cm−1) and the C‐O stretching bands (1050‐1000 cm−1) of the cellulose were greatly decreased in intensity, while the epoxy band (915 cm−1) and the band at 1160 cm−1 had virtually disappeared.A total frequency assignment of both the epoxy system and the cellulose are presented. The adhesion at the cellulose‐epoxy system interface is discussed with respect to the chemical changes inferred from the above‐mentioned spectra.
Oxygen/alkali oxidation of cellulose and model alcohols and the inhibition by iodide
Authors: Minor J. L. , Sanyer N. 
Published: June 2010

AbstractCertain aspects of cellulose depolymerization by oxygen in alkali were investigated with model compounds. Oxidation of hydroxyl groups was studied using low molecular weight glycols and alcohols. Hydrogen peroxide was identified as the peroxidic intermediate observed during oxygen oxidations of carbohydrates. Oxidation of glucitol by either alkaline hydrogen peroxide or oxygen is autocatalytic with a discrete induction period. When hydrogen peroxide is initially present in the oxygen oxidation, the induction period is considerably reduced. In the presence of potassium iodide, the induction period is lengthened. Potassium iodide inhibits the depolymerization of cellulose by oxygen and alkali and, in the presence of magnesium ions, provides more stabilization than either alone. A mechanism to explain these results is proposed.
Study of cellulose structure and its relation to reactivity
Authors: Nelson Russell , Oliver Don W. 
Published: June 2010

AbstractInformation is presented to show that the total volume of micropores in acetic acid swollen fibers correlates closely with acetylation reactivity. Pore size distribution measurements indicate that the pores with diameters of 25–75 Å may be particularly influential for promoting reactivity since fibers which perform well in acetylation processing have a characteristically high volume of pores in this size range. Internal surface area also correlates with acetylation reactivity if allowances are made for the large fraction of surface area which is associated with pores that are too small for reagent penetration. This lower limit is calculated to be 20–25 Å. Based on estimates of void spaces within and between the cellulose structural building units, acetylation of acetic acid swollen fibers should occur on the external surfaces of the elementary fibrils, the microfibrils and the lamellae as well as on the internal surfaces of the microfibrils and the lamellae. The overall effect of cellulose structure on reactivity seems to be the control of the inward flow of reagents to reaction surfaces but not the outward transport of reaction products. Internal void volume may function to accommodate reaction products as they swell inwardly and thus provide a means for allowing the reaction to go to completion. The relationship between cellulose structure and reactivity can be extended to chemical reactions other than acetylation.
Neutral hydrolysis of alkali lignin to monomeric phenols
Authors: Benigni J. D. , Goldstein I. S. 
Published: June 2010

AbstractAlkali lignin has been found to undergo neutral hydrolysis to produce simple phenolic materials. Data on the effects of time and temperature on the yields of oil and monomeric phenolic materials produced are presented. Also the use of acidic or basic reaction conditions and other types of lignin are discussed.
Enzymatic degradation of carboxymethylcellulose and other cellulose derivatives
Authors: Bhattacharjee S. S. , Perlin A. S. 
Published: June 2010

AbstractSeveral water‐soluble cellulose derivatives have been subjected to degradation with a cellulase preparation from Streptomyces sp. QM B814. Structural analysis of the enzymolysis products is described, particularly in relation to carboxymethylcellulose. For comparison, corresponding derivatives of lichenin, a soluble β‐glucan structurally related to cellulose, have been examined with the use of this enzyme. The results indicate that the distribution of substituents in the cellulose derivatives is not uniform and that accessibility is important in determining the pattern of derivatization. Both carboxymethyl‐and hydro‐xyethylcellulose appear to be attacked by the cellulase in a similar fashion, and the two kinds of substituent groups are equally effective in limiting hydrolysis by this enzyme.
Textile properties of cotton cellulose graft copolymers and terpolymers
Authors: Mares Trinidad , Arthur Jett C. 
Published: June 2010

AbstractCotton cellulose graft copolymers and terpolymers were prepared by radiation initiated processes. Monomers copolymerized with irradiated cellulose from solutions of methanol‐water were: methacrylic acid (MAA), methacrylonitrile (MAN), and hexafluoroisopropyl acrylate (6FIPA). Cotton cellulose, immersed in solutions of N‐vinyl carbazole (NVC) in 1,2‐dichloroethane, was irradiated to form a copolymer. Terpolymers prepared were; cellulose‐poly(MAA)‐poly(MAN), cellulose‐poly(MAA)‐poly(6FIPA), and cellulose‐poly(MAN)‐poly(6FIPA). Textile properties of the cotton fabric copolymers and terpolymers determined included: flex and flat abrasion resistance, breaking strength, and water repellency. The properties of the cellulose copolymers and terpolymers were related to chemical structures of the monomers used and the glass transition temperatures of their homopolymers.
Structural changes during deformation of high molecular weight and low molecular weight polyethylene
Authors: Steidl J. , Pelzbauer Z. 
Published: June 2010

AbstractStructural changes caused by cold drawing low and high molecular weight polyethylene (M = 7 × 104 and 1.5 × 106) were investigated by using wide‐angle x‐ray diffraction, light and electron microscopy. Results obtained from drawn samples subjected to stress and samples at zero stress, revealed important differences in the behavior of these two polymers. In contrast with the low molecular weight polyethylene, the high molecular weight samples were deformed homogeneously without neck formation; the orthorhombic lattice, when subjected to stress, is transformed into a monoclinic one, not only in the initial stage, but over the whole deformation range up to breaking. The spherulitic structure in both polymers changes into the fibrillar one, while the degree of orientation attainable for the low molecular weight polyethylene is higher than that for the high molecular weight sample. During deformation of the low molecular weight polymer, cracks form between fibrils, and the fibrils become separated. Such an effect has not been observed with the high molecular weight material. After the external stress has been removed, a considerable contraction and decrease in orientation characterize the high molecular weight polyethylene. The differences in behavior of the two types of polymers are discussed in terms of different structural models.
Polymer morphology and mechanism of macrocrack propagation on fracture surfaces
Authors: Kireenko O. Ph. , Marichin V. A. , Miasnikova L. P. , Regel V. R. 
Published: June 2010

AbstractTh0e relief of fracture surfaces of oriented monofilaments of nylon 66 has been studied with the help of both transmission and scanning electron microscopy. It has been shown that at different speeds of macrocrack propagation the relief of the so‐called mirror zone can show the original structural features of the material (e.g., the existence of supermolecular structures of the order of a micron, the influence of annealing, the distribution of micropores in the fibrillar amorphous regions) as well as effects connected with deformation processes at the tip of the crack, with discrete and auto‐oscillatory mechanisms of crack growth, the interaction of the macrocrack with the secondary fracture processes, etc.
Morphological investigations of ordered gel formation in polyelectrolytes
Authors: Purz H. J. 
Published: June 2010

AbstractThe diffusion of certain counter ions, such as T1, Ni, Cd or Zn ions, into the anionic polyelectrolyte Na‐cellulose xanthate results in ionotropic formation of ordered gels. These gels show birefringence, swelling anisotropy, ion exchange capability, and, under certain condition, capillary structure. The gel structure depends on the ion species. The factors affecting the capillary structure can advantageously be investigated with Zn‐and Tl‐cellulose xanthate gels. The gels formed under various geometrical arrangements have been investigated by optical, polarization and electron microscopy. The concept of the formation of ordered gels and capillaries is discussed. The gel properties (birefringence, coherent network structure, membrane and capillary structure) are maintained after splitting off the‐CSSH groups of the unstable metal cellulose xanthate gels. This offers the possibility of controlling the formation of supermolecular structure in cellulose by synthesis of ionotropic polyelectrolyte gels.
Structural changes of poly(vinyl chloride) particles
Authors: Ponížil František 
Published: June 2010

AbstractMinute particles of emulsion paste‐forming poly(vinyl chloride) (PVC) sinter when dried in a nubilous dryer. In contact with a plasticizer they change their structure‐depending on the hardness of their surface they disintegrate into many small particles. Some substances, especially those belonging to a group of simple glycolethers, have been found to considerably accelerate the disintegration process. To study the process, chiefly microscopic observations were carried out completed with additional viscosity and refraction measurements.In the microscope an unusual interaction of PVC particles with glycolether itself has been observed. In contrast to plasticizer action, irregular fragments are formed instead of small particles. Calorimetric measurements done during the interaction indicated that the interaction is a strongly exothernic process.Based on the above mentioned measurements a mechanism is suggested for these disintegration processes which greatly affect viscosity of PVC pastes.
A partition function for chain molecules applicable to high and low densities
Authors: Bonner D. C. , Bellemans A. , Prausnitz J. M. 
Published: June 2010

AbstractThe quantitative calculation of vapor‐liquid equilibria in mixtures consisting in part of chain molecules requires a partition function valid at both low and high densities. A preliminary partition function for this purpose is described. It is based on the hole theory of liquids and incorporates the concepts of Prigogine and Hijmans for chain molecules. The new partition function is used to represent the vapor‐liquid coexistence curves of long‐chain n‐alkanes.
Generalization of the flory‐huggins treatment of polymer solutions
Authors: Kennedy J. W. , Gordon M. , Koningsveld R. 
Published: June 2010

AbstractThe Flory‐Huggins form of the free enthalpy (Gibbs free energy) of mixing expression for solutions of linear homopolymers, generalized to make the interaction parameter × a function of concentration (as well as temperature) has been extended further to cover in general copolymeric and branched systems. From the resulting expression it is still possible to obtain the chemical potential, spinodal, and consolute state relationships in closed form. One simple case to which this treatment can be applied is that of the linear homopolymer system in which the interaction parameter is regarded as a function of molecular weight.A particular form for the molecular weight dependent interaction function is considered. After reducing the number of parameters by applying some thermodynamic restrictions, the remaining constants are evaluated with the aid of critical point data. The resultant interaction function is compared with other available experimental data. The process of reducing the number of floating parameters by means of restrictions of a thermodynamic nature is of general significance.
Quasichemical equilibrium approach to crosslinked polymer solutions
Authors: Dušek K. 
Published: June 2010

AbstractThermodynamic functions for mixing of a solvent with a crosslinked (branched) polymer are derived by considering the primary chains as copolymers of crosslinked and uncrosslinked units. Primary chains and solvent molecules are placed on a lattice with coordination number z. The crosslinked units bear one crosslinkable (C) and z‐3 (inner units) or z‐2 (end units) uncrosslinkable (U) contact surfaces. The free enthalpy of mixing is obtained by the quasichemical equilibrium approach and Tompa's modification for polymer molecules with different contact points. The condition of quantitative pairing (of purely entropic nature) of C contact surfaces is then introduced leaving only U contact surfaces available for the quasichemical equilibrium. In the polydisperse case, primary chains with a constant number of crosslinked and uncrosslinked units are taken as components. If mixing causes the dimensions of elastically active network chains (EANC) to be different from their reference (rest) dimensions, an elastic contribution proportional to the number of EANCs is added to the free enthalpy change. Comparing the result with the swelling equation of Flory relating the chemical potential of the solvent to the lattice site fraction of the polymer after swelling (θP) and at crosslinking (θP) and the fraction of EANCs per polymer unit (ve) ΔμS/RT = In (1 ‐ θP) + θP + XθP2 + ve (θP1/3θP02/3 ‐ αθP) (with α ± 1/2), it is shown that the interaction parameter × is a function of the coordination number, degree of crosslinking, molecular weight of primary chains (and concentration); the depedence vanishes if z goes to infinity. The coefficient α depends on the network structure and is equal to 1/2 only for an ideal network obtained by crosslinking of an infinite primary chain.
A refractometric and gel sorption study of the system poly(vinyl alcohol)‐water‐n‐propanol
Authors: Nagy M. , Wolfram E. , Györfi‐szemerei A. 
Published: June 2010

AbstractIt has been found that direct measurement of selective sorption of solvent mixture on the loosely crosslinked gels with low polymer concentration would yield some information on the preferential solvation and also on the nature of the interactions. Experimental data obtained by refractometry and sorption measurements carried out with the system poly(vinyl alcohol)‐water‐n‐propanol have shown the proposed way of approximation to be successful. Based on the experimental results a solvate model for this system was proposed in which the n‐propanol is bound to the polymer chain by both hydrogen and hydrophobic bonds.
Etudes spectroscopiques de transitions “helice‐pelote” de polypeptides en solution acide
Authors: Combelas Ph. , Garrigou‐Lagrange C. 
Published: June 2010

AbstractInfrared spectra of various polypeptides (poly‐L‐alanine, or PLA; poly‐L‐methionine or PLM; poly (γ ‐ benzyl‐L‐glutamate), or PBLG) in CF3COOH‐CHCl3 solutions have been investigated in regions characteristic of the peptide group (amide A, I and II) and of the acid solvent (vOH, vC=O). These spectra have been analyzed by comparison with the infrared spectrum of a model amide (N‐methylacetamide). This analysis shows that by addition of acid the simple amide and the polypeptides exhibit at first a similar behavior by forming complexes by hydrogen bonding, i.e., >C=O…HOOCCF3. At higher acid concentrations, unlike the model amide, polypeptides are not protonated. Furthermore, the evolution of the spectra as a function of complexation clearly indicates the helix‐random coil transition of these polymers and agrees well with optical rotatory dispersion measurements. Thus, steep transitions have been obtained for PBLG and PLM in a small range of acid concentration or of temperature. To the contrary, no discontinuity in the evolution of PLA spectra has been seen. This observation compares well with the slow transformation observed by optical rotatory dispersion (ORD). Finally, it is possible to compare at the level of the repeat unit the strength of the acid perturbation which triggers the transformation of the three polypeptides. This points out the important part played by the sidechains as stabilization forces of the helix and the cooperative aspect of the transitions.