bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal stability of polymerization reactors
Authors: Brooks B. W. 
Published: April 2003

AbstractTemperature rises which occur in the early stages of polymerization in batch reactors are discussed. Comparisons between experimental results and a reactor model shows that realistic predictions of temperature rises can be made when the model allows for changes in density and specific heat of the reaction fluid. In the case of styrene polymerization, the neglect of density and specific heat changes leads to the prediction of large temperature increases, which are not found in practice. When allowance for these changes in physical properties is made, agreement between theoretical prediction and experimental results is good.
Quantitative studies by differential scanning calorimetry of the reaction between hydrogen peroxide and lignocellulose
Authors: Nguyen Tinh , Zavarin E. , Barrall E. M. 
Published: April 2003

AbstractHeat of reaction and kinetic parameters were determined by differential scanning calorimetry for decomposition of hydrogen peroxide, reaction of hydrogen peroxide with lignocellulosic materials, glucose and pinitol, and for the reaction of the same materials with produced or introduced oxygen. The heat of decomposition of hydrogen peroxide obtained in N2 (720 cal/g H2O2) was in fair agreement with literature data, considering the different temperature and pressure conditions. The heats of reaction of hydrogen peroxide and lignocelluloses were higher when determined in N2 (1670–2500 cal/g H2O2) than in O2 (1450–2020 cal/g H2O2) atmosphere. The activation energy for decomposition of hydrogen peroxide amounted to 20.3 kcal/mol in N2 and 15.9 kcal/mol in O2 with frequency factors of 5.7 × 109 and 3.7 × 107 min−1, respectively. The activation energies for the reaction of hydrogen peroxide and lignocellulosic materials tested were similar and not influenced by the atmospheric composition, ranging overall between 19.7 and 22.4 kcal/mol. The corresponding frequency factors ranged between 2.77 × 109 and 2.23 × 1011.
Thermal effects of interaction between macronet isoporous styrene polymers and solvents or precipitators for linear polystyrene
Authors: Tsyurupa M. P. , Volynskaya A. V. , Belchich L. A. , Davankov V. A. 
Published: April 2003

AbstractA study has been made of the heats of swelling of macronet isoporous polymers of styrene in toluene and methanol. The swelling of hypercrosslinked networks (degree of crosslinking ≥40%) is shown to be accompanied by liberation of large amounts of heat: 30 and 25 cal/g, respectively. The small difference in the heats of swelling in these media is indicative of small differences in the energy of dispersional interactions of exposed polystyrene chains with “good” and “poor” solvents. This conclusion is corroborated by calculations of the free energy of interaction between hypercrosslinked networks and organic solvents from the isotherms of sorption of their vapors. ΔG reaches high values (500–600 cal/mol) independently of the solvent nature.
Study on triazine thiols. IV. Action of triazine thiols and their metal salts to peroxide
Authors: Mori Kunio , Nakamura Yoshiro 
Published: April 2003

AbstractDecomposition of t‐butylhydroperoxide was retarded by triazine thiols and their zinc salts, but accelerated by the copper salts of triazine thiols as well as sulfur compounds such as dithiocarbamates and mercaptobenzothiazolates. Triazine thiols and their zine salts are effective antioxidants for polyethylene crosslinked with peroxide and containing copper, and for protecting epichlorohydrin vulcanizates against attack by “sour” or hydroperoxide‐containing gasoline.
Solubility of isobutane and propane in polyethylene at high temperatures and low pressures
Authors: Meyer J. A. , Blanks R. F. 
Published: April 2003

AbstractA novel procedure was developed to measure the solubility of isobutane and propane in both low and high‐density polyethylene at temperatures to 500°F (260°C) and vapor pressures from 1 to 1500 torr (33 psia). These measurements represent the first known solubility measurements at these combined extremes of pressure and temperature. Excellent agreement was found when our data were extrapolated to higher pressures and compared with data from another source. In the temperature and pressure regions of interest in this work, the linear isotherms were fit with a form of the Flory–Huggins equation. With the equation in that form we can now estimate the ratio of solubilities of two solutes in a given polymer from pure solute data only. We can also predict the absolute solubility of nonpolar solutes in polyethylene at various temperatures and pressures using only critical temperatures and acentric factors of the solutes.
Rheology of unsaturated polyester resins. II. Thickening behavior of unsaturated polyester and vinyl ester resins
Authors: Han Chang Dae , Lem Kwok‐Wai 
Published: April 2003

AbstractThe rheological properties of mixtures of unsaturated polyester resin and viscosity thickener were determined as thickening progressed. Two commercially available resins were used: (1) general purpose unsaturated polyester resin (Ashland Chemical, Aropol 7030), and (2) vinyl ester resin (Dow Chemical, XD‐7608.05). As thickening agent, a magnesium oxide (MgO) paste dispersed in styrene monomer was used. No fillers, pigments, or other additives were used. During thickening, the following measurements were also made: (1) acid number by titration and (2) molecular weights by gel permeation chromatography (GPC). For the Ashland Chemical polyester resin, it was found that, over a period of 300 h, the titration method indicated that the number‐average molecular weight (Mn) increased by a factor of 2 and the weight‐average molecular weight (Mw) increased by a factor of 3. The GPC measurements, however, showed that Mn increased very little whereas Mw increased by a factor of about 2. Over the same period, the viscosity of the Ashland Chemical polyester resin increased from 0.9 N·s/m2 (9 P) to 104 N·s/m2 (105 P), and the viscosity of the Dow Chemical vinyl ester resin increased from 0.7 N·s/m2 (7 P) to 2 × 103 N·s/m2 (2 × 104 P). Such a large increase in viscosity cannot be explained by the existing molecular theory, in view of the fact that the molecular weights increased relatively little. We speculate that the exceedingly large increase in viscosity during thickening is attributable primarily to ionic associations between the carboxylic anions and the magnesium ions, rather than to the formation of chain branching suggested in the literature. It was found further that mixtures of polyester resins and viscosity thickener exhibit normal stress effects, increasing with thickening time and following the behavior of a second‐order fluid when the first normal stress difference was plotted against shear rate. Interestingly enough, however, plots of first normal stress difference vs. shear stress yield a correlation which becomes independent of thickening time. An explanation is offered to the correlation obtained.
Extending the continuum of molecular weight distributions based on the generalized exponential (Gex) distributions
Authors: Gloor Walter E. 
Published: April 2003

AbstractLiterature data on the average molecular weights Mn, MW, Mz, and/or Mv for several polymers indicated that they fell outside the continuum originally proposed to model molecular weight distribution (MWD), where the log‐normal (LN) distribution, or positively valued Gex parameters m and k, define the continuum. Following the papers of Kubin, it is possible to embrace these polymers in an extended continuum by including these parameters, both negatively valued, in it. To the extent that m ≥ −1 and k < −5, the extended continuum models average molecular weights through Mz+2. The correspondence of Gex models of MWD of a polymer obtained from data on its Mn, Mw, and Mz with that obtained from data on its Mn, Mv, and Mw is indicated, using published data. The numerical value of the m parameter in a Gex model is of use in polymerization kinetics; when m values are obtained for each analysis from multiple analyses upon a given polymer, their consistency indicates the concordance of the three average molecular weights from each test run. The Gex parameters based upon Mn, Mw, and Mv or Mz can be used to estimate values for higher average molecular weights of linear, unimodal homopolymers. This is of use in interpreting rheological data on such polymers.
Cyclomatrix poly(organo phosphazenes)—some aspects of synthesis, characterization and adhesive heat resistance
Authors: Devadoss Eswaran 
Published: April 2003

AbstractStructure‐property relationships of a phosphazene‐modified epoxy‐based cyclomatrix system were studied using aromatic diamine condensates of hexachlorocyclotriphosphazene (PNCl2)3and a diglycidyl ether of bisphenol‐A. Synthesis and characterization of the condensates and difficulties associated with these aspects are described. Adhesive heat resistance and thermal stability are reported as functions of the “active hydrogen” content of the condensates, molar ratios of the epoxy and “active hydrogen,” and amine structures. Modification of the OH groups formed in the amine–epoxy reaction via cyanoethylation and transesterification was not effective in improving high‐temperature adhesion. The polymer systems were stable up to 380°C in air, exhibited higher char contents at elevated temperatures, and were optically clearer when compared with the corresponding nonphosphazene systems. Presence of phosphazene rings was also helpful in lowering the cure time and temperature.
Ethylene–styrene diblock copolymers: Synthesis by Ziegler–Natta catalysis and identification
Authors: Soum Alain , Siove Alain , Fontanille Michel 
Published: April 2003

AbstractA new way of directly synthesizing ethylene–styrene diblock copolymer by Ziegler–Natta catalysis was studied. It consists of using a soluble complex prepared by the reaction of

with TiCl4 in the ratio r = [Li]/[Ti] = 2 to initiate the formation of the polyethylene block. The well‐defined linear diblock structure was established both by GPC of the polyethylene block and by 13C NMR and DSC analyses of the copolymer. Moreover, by using such a catalytic system, the efficiency was found to be 0.88 with respect to carbon‐titanium bond. This value is relatively high compared to those of conventional Ziegler‐Natta catalytic systems.
The microwave dielectric constants of water–paper mixtures: The role of sheet structure and composition
Authors: Habeger C. C. , Baum G. A. 
Published: April 2003

AbstractA precise technique for determining dielectric constants at microwave frequencies from slotted line measurements is adapted to paper samples. The effects of refining, wet pressing, calendering, and TiO2 addition on the dielectric constants vs. moisture curves are reported and discussed. The observed in‐plane dielectric anisotropy is discussed. The importance of considering geometry at the fiber level in explaining the dielectric behavior of paper is stressed.
The mechanism of cure of tetraglycidyl diaminodiphenyl methane with diaminodiphenyl sulfone
Authors: Gupta A. , Cizmecioglu M. , Coulter D. , Liang R. H. , Yavrouian A. , Tsay F. D. , Moacanin J. 
Published: April 2003

AbstractThe curing reaction of tetraglycidyl diaminodiphenyl methane (TGDDM) with diaminodiphenyl sulfone (DDS) has been investigated using differential scanning calorimetry, Fourier transform IR spectroscopy, and ESR spin trapping techniques. A mechanism has been proposed, and the cure kinetics has been obtained at 177°C. The major conclusion is that cure proceeds mainly through chain extension, while crosslinking occurs through the reaction of hydroxyl groups with epoxides, resulting in formation of ether linkages.
Reaction of 3‐methyl phenol with tung oil
Authors: Yoshimura Yukio 
Published: April 2003

AbstractThe aromatic ring substitution reaction of 3‐methyl phenol with tung oil under acidic conditions was carried out. The product was analyzed to find out if 3‐methyl phenol was subjected to the ring substitution reaction with tung oil at its conjugated double bonds. Up to two molecules of 3‐methyl phenol were addition‐reacted with the conjugated triene of one eleostearyl group of triglyceride of α‐eleostearic acid which is the major component of tung oil. The 4‐position of 3‐methyl phenol was preferentially subjected to the cresol's ring substitution. Therefore, up to 6 mol of 3‐methyl phenol was added to 1 mol of tung oil, most of which was bonded to 3‐methyl phenol at its 4‐position. When 3‐methyl phenol was reacted with a relatively large amount of tung oil, the substitution reaction occurred at the 6‐as well as 4‐position of 3‐methyl phenol to yield a tung oil dimer having 3‐methyl phenol units in its molecule. The above results were confirmed by infrared (IR), nuclear magnetic resonance (NMR), and high‐speed liquid chromatographic (HLC) analyses.
Chemical factors affecting soiling and soil release from cotton‐containing durable press fabric. VIII. Grafting of polyester/cotton blend fabrics with carboxyl‐containing polymer
Authors: Hebeish A. , Abou‐Zeid N. Y. , El‐Kharadly E. , Shalaby S. E. , El‐Alfy E. A. , Abdel‐Fattah S. H. , Bayazeed A. M. , Nasr H. 
Published: April 2003

AbstractFabric samples of polyester/cotton blend were graft copolymerized to different levels (add‐ons) with poly(acrylic acid) and poly(methacrylic acid) using the mutual γ‐irradiation technique and the Fe2+–H2O2 redox system, respectively. The copolymers so obtained were given durable press treatments with and without conventional nonionic softener using DMDEU as the crosslinking agent. The susceptibility of the copolymers before and after crosslinking to aqueous and nonaqueous oily soiling and their ability to release the soils were examined. It was found that hydrophilization of the surface of polyester/cotton blend through grafting with the said carboxyl‐containing polymers brings about a significant improvement in the resistance of the blend to aqueous and nonaqueous oily soil particularly after crosslinking in presence of nonionic softener. A certain improvement in the ease of oily soil removal could be achieved by grafting. The opposite holds true for aqueous soil release. Soiling and soil release depends on the magnitude and method of grafting, medium of soiling, as well as the formulation of crosslinking treatments. The effect of grafting on some properties of the blend fabric before and after crosslinking was also examined.
Grafting of vinyl monomers onto silk fibers: Trivalent‐manganese‐initiated graft copolymerization of acrylamide onto silk fibers
Authors: Samal Rajani K. , Nanda C. N. , Satrusallya S. C. , Nayak B. L. , Suryanarayan G. V. 
Published: April 2003

AbstractGraft copolymerization of acrylamide (AM) onto silk fibers, using Mn(III)–sulphate as initiator, has been investigated, in aqueous sulphuric acid in the temperature range of 30–55°C. Grafting reaction has been studied by varying the concentration of monomer, Mn(III), sulphuric acid, temperature, and also with the modified silk. The graft yield increases significantly with increase of monomer concentrations to the extent of 0.85M, after which the rate falls. With increase in Mn(III) concentration and H+ ion concentration the graft yield increases, but after an optimum concentration a depression in the graft yield is noticed. The rate of the reaction is temperature‐dependent; with increase of temperature the graft‐on increases. Among the solvent composition studied a solvent/water mixture containing 10% of the solvent seems to constitute the most favorable medium for grafting, and a further increase of solvent composition decreases the graft yield. The effect of various additives such as transition metal salts, aromatic and heterocyclic amines on grafting reaction has been studied. A suitable mechanism for grafting has been proposed. Finally physical characterization such as thermal analysis (TGA) of the grafted samples has been carried out in order to ensure grafting and to study the change in the properties of the fibers.
Effect of stirring on cellulose graft copolymerization
Authors: Graczyk T. , Hornof V. 
Published: April 2003

AbstractDissolving pulp was grafted with several monomers ranging from hydrophilic (dimethylaminoethyl methacrylate) to hydrophobic (styrene). The conversion of these monomers to polymer and copolymer was investigated in dependence on the number of revolutions of the agitator. The formation of grafted copolymer was found to be strongly influenced by stirring. For all the monomers employed, almost no copolymer was formed above 400 rpm. The formation of homopolymer was also severely reduced at higher stirring speeds. For some monomers, a maximum was obtained at about 200–300 rpm with both copolymer and homopolymer yields dropping off sharply at both lower and higher stirring speeds. The position of this maximum was affected by the size of the reactor. The behavior displayed by the xanthateFe2+–H2O2, Fe2+–H2O2, and ceric ion initiation systems was very similar. Also, monomer solubility in water seemed to have little importance in determining the general behavior.
The development of a new technique for the evaluation of polymer burning behavior
Authors: Hsieh You‐Lo , Yeh Kwan‐Nan 
Published: April 2003

AbstractA new research technique was developed for the evaluation of fundamental burning characteristics of polymers. Burning characteristics examined included heat release, mass change, oxygen consumption, and carbon monoxide and carbon dioxide generation. A laboratory apparatus was designed and constructed so environmental conditions could be controlled. The detection of selected parameters was realized by the use of various devices and instrumentation. Instrumental potentiometric outputs were processed with a data acquisition system to accommodate simultaneous data collection in the calibration and the material study. Each device used for parameter measurement was standardized and calibrated by itself as well as in connection with the system. Systematic errors were estimated to be less than 6%. The technique was tested with flame retardant systems containing antimony trioxide (Sb2O3) and decabromodiphenyl oxide (DBDPO) on polyethylene film. Significant different effects on the heat reduction and CO formation in the system containing DBDPO alone and that containing both DBDPO and Sb2O3 were observed. Different flame‐retardation mechanisms for these two systems were postulated and confirmed by additional thermal and elemental analyses. Results demonstrated that this technique can be an effective mean in the evaluation of polymer‐burning behavior and flame‐retardant mechanisms.
Light scattering studies of hi‐impact polystyrene
Authors: Tabar R. J. , Hu S. R. , Stein R. S. 
Published: April 2003

AbstractSmall‐angle light scattering techniques have been used to evaluate the factors controlling the transparency of two hi‐impact polystyrene films. These factors were found to include surface smoothness, volume fraction of the phases in the system, the difference of the refractive indices of the phases, and the sizes of the phases. The elongation of the rubber phase during processing was also determined.
Adhesion of block copolymers to glass: Lap shear strengths as a function of bonding conditions
Authors: Widmaier J. M. , Meyer G. C. 
Published: April 2003

AbstractABA poly(styrene‐b‐isoprene) block copolymers with various molecular weights and composition were used as heat activated films in simple overlap glass joints. The influence of bonding temperature on their shear strength at break was investigated. On increase of temperature, the joint resistance for most of the copolymers passed through a maximum, which temperature was dependent on the molecular characteristics of the copolymers. The decrease in melt viscosity or chemical degradation could not explain the data. A morphological interpretation which fits well the present and previous observations is proposed and verified for one copolymer used in this work.
Studies on polyurea membrane
Authors: Joshi S. V. , Rao A. V. 
Published: April 2003

AbstractSynthesis of polyurea by interface polymerization of diisocyanate and diamine for preparation of polymer membrane for use in separation problems was investigated. A sulfuric‐acid‐based casting formulation was developed for the polymer prepared from 1,6‐hexamethylene diamine and 1,6‐hexamethylene diisocyanate. The resulting membrane is porous and highly permeable to water. However, salt rejection was found to be <20%, while high molecular weight solutes like milk, papain, and Na‐alginate were found to be rejected 100%. The membrane is more like a sieve structure with the absence of an asymmetric layer. It is found to be resistant to many organic solvents, thus making it suitable for use in ultrafiltration applications.
Rheological studies of cellulose derivatives solutions
Authors: Dayan S. , Gilli J. M. , Sixou P. 
Published: April 2003

AbstractThe rheological behavior of solutions of cellulose derivatives, acetate, and hydroxypropyl was studied as a function of different parameters; molecular weight, concentration,…, at T = 25°C in the vicinity of the liquid crystal phase transition. A variation of the strain rate sensitivity parameter with concentration is found. A degradation of the solution in trifluoroacetic acid is demonstrated.
Investigation on the effect of the acid number of the plasticizer on some PVC properties
Authors: Gancheva T. S. , Dinev P. D. , Bukovska K. G. 
Published: April 2003

AbstractThe effect of polyester plasticizer of differing acid number on the properties of PVC compositions, to be used for electric insulation purposes, is investigated. It is established that the acid number affects both the temperature dependence of the specific bulk resistance in vitreous and highly elastic state and the process of formation of a polymer matrix with minimum ion diffusion factor. The assumption is made that the effects observed are due both to the different stability of plasticizers of differing acid number towards destruction at thermal processing and to the difference in density of the polymer matrix depending on the acid number of the plasticizer. It is considered that polyester plasticizer (PEP) is a cheap and efficient plasticizer, which, irrespective of the nontraditional high acid number, could successfully be used for PVC plastication.
Concentration of radioactive liquid streams by membrane processes
Authors: Ramachandhran V. , Misra B. M. 
Published: April 2003

AbstractThe possibility of concentrating radioactive effluents by reverse osmosis was investigated. Cellulose acetate membranes of the Loeb–Sourirajan type were used, and their performance was evaluated for CsCl and SrCl2 solutions in concentrations ranging from millimolar to trace level. The applicability of solution–diffusion and irreversible thermodynamic models for predicting solute separation in the above concentration range has been investigated. Some aspects of the selectivity with reference to trace radionuclides are also reported.