bluuebunny/crossref_metadata_2025 huggingface dataset:
Curing reactions in elastomers. II. Carboxy‐terminated polybutadiene
Authors: Kishore K. , Verneker V. R. Pai , Vasanthakumari R.
Published: April 2003

Attempts have been made to understand the curing reactions in carboxy‐terminated polybutadiene (CTPB), which happens to be the most practical binder in advanced solid composite propellants. The curing of CTPB has been studied for different ratios of curing agents (MAPO and Epoxide) by gel content, molecular weight, crosslink density, and penetration temperature measurements, and the optimum composition of curators for effective curing of CTPB has been determined. Activation energy calculations on the curing of CTPB with 9.5% epoxide and 0.5% MAPO in the temperature range 75–100°C gave 14.1 kcal/mol for which a diffusion‐controlled or acid‐catalyzed epoxide ring opening mechanism has been suggested for the curing process in CTPB.
Thermal stability of polymerization reactors
Authors: Brooks B. W.
Published: April 2003

Temperature 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

Heat 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

A 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

Decomposition 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

A 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

The 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

Literature 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

Structure‐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

A 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

A 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

The 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

The 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

Fabric 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

Graft 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

Dissolving 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

A 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

Small‐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

ABA 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

Synthesis 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

The 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

The 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

The 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.
Viscoelastic properties of sulfonated ethylene–propylene terpolymer neutralized with zinc cation
Authors: Granick Steve
Published: April 2003

Stress–relaxation measurements in uniaxial extension, in the terminal zone, were made of sulfonated ethylene–propylene terpolymer (EPDM), neutralized with zinc cation. The sulfonation levels were 15 to 20 meq/100 g polymer (0.47 and 0.62 mol %), and for each level the effect of the ionic plasticizer, zinc stearate, was investigated. For all the polymers, the decay of the modulus with elapsed time was gradual and featureless, reflecting a broad distribution of relaxation times. Sensitivity of the ionomers' structures to thermal history before an experiment was suggested by irreproducibility in the magnitudes, but not the distribution, of relaxation times at a given temperature. For polymers containing zinc stearate measured at 80°C, the amount of permanent set was low for relaxation up to about 20h, but increased rapidly with additional hours of stretch. Time–temperature superposition did not apply. Composite curves were constructed by matching the stress–relaxation response at short times; moduli measured at long times fell above the composite curve. The shapes of the composite curves were similar, regardless of the level of EPDM sulfonation or the presence of zinc stearate. The apparent Arrhenius activation energy for short‐time relaxation at similar levels of the modulus was about 35 kcal/mol at 140°C for the unplasticized polymers and about 70 kcal/mol at 90°C for the polymers containing zinc stearate, in contrast to the usual effect of plasticizer on the rate of relaxation of amorphous polymers except near the glass transition temperature.
Synthesis and viscoelastic properties of new thermosetting resins having isocyanurate and oxazolidone rings in their molecular structures
Authors: Kinjo Noriyuki , Numata Shun‐Ichi , Koyama Toru , Narahara Toshikazu
Published: April 2003

A new type of thermosetting resin can be obtained from solventless varnishes composed of polyfunctional isocyanates and epoxides. The IR spectra show that the cured resins have isocyanurate and oxazolidone rings in their chemical structure, hence their name, isocyanurate–oxazolidone resins. The viscoelastic behavior of the cured resins can be varied considerably by selecting an appropriate reactant species and changing the equivalent ratio of the isocyanate and epoxy groups in the varnishes. Three relaxations, labeled α, β, and γ, characterize their dynamic mechanical spectra. The α‐dispersion is due to the glass transition, the β‐dispersion, to local mode motions of the backbone chains of resins, and the γ‐dispersion, to the molecular motions of long alkyl chains. If certain additives are mixed into the varnishes before curing, microphase separation takes place during the reactions. The resins finally obtained have a peculiar physical structure in which rubber particles are dispersed throughout a matrix phase as confirmed by scanning electron‐microscopic analysis and viscoelastic behavior.
Electron beam irradiation induced grafting of acrylonitrile to polyethylene powder
Authors: Morgan Paul W. , Corelli John C.
Published: April 2003

This study focuses on the influence of various parameters on the post‐irradiation grafting of acrylonitrile monomer to a low density polyethylene powder having an average particle size of 20 μm diameter. The type of radiation used was 0.8 MeV electrons with a dose rate of either 0.1 Mrad/min or 4.0 Mrad/min. Irradiations were carried out in vacuum, air, and dry oxygen environments at room temperature to total doses ranging from 1 Mard to 15 Mrad. Several experimental techniques were used to investigate various interrelated aspects of both the graft copolymer product and the graft process, including infrared spectroscopy to measure percent graft, electron spin resonance to measure radical concentrations, scanning electron microscopy to investigate surface morphology, and differential scanning calorimetry to measure crystalline content. Comparisons of the percent graft determined from different probes were found to be consistent. The dose dependence of grafting exhibited a linear relationship below 8 Mrad. Initiation by both alkyl and peroxy radicals at 77°C was supported by results of decreased grafting with decreased temperature, increased dose rate or vacuum irradiation. Decreased grafting after oxygen irradiation suggested a unique change in grafting mechanism. Higher grafting yields were found for quenched relative to annealed samples. The amount of extractable homopolymer formed was found to be ∼ 10% at a dose of 10 Mrad and a dose rate of 4 Mrad/min.
Stress optical behavior in polystyrene; residual stresses and birefringences in large, quenched samples
Authors: Wust C. J. , Bogue D. C.
Published: April 2003

In a basic study of the nonequilibrium glassy state of polystyrene, two related areas have been investigated. The first dealt with homogeneous samples and included work on volume aging and the effect of temperature on the stress (and strain) optical coefficients and on the modulus. The second dealt with nonhomogeneous samples and included measurement of the frozen‐in birefringence in large, quenched samples and analysis of this residual birefringence, and also the stress, with residual stress theory. The theory used was that of Aggarwala and Saibel, which is a special case of the more general theory of Lee, Rogers, and Woo.
Viscoelastic properties of a gum vulcanizate at large static deformations
Authors: Sullivan J. L.
Published: April 2003

The loss tangent corresponding to small sinusoidal oscillations superposed on a large static deformation is found to decrease with increasing static deformation ratio for a natural rubber gum vulcanizate. Further, the response functions of the stress–relaxation and the incremental stress–relaxation vs. time and the storage modulus vs. frequency are found not to be separable functions of time and strain effects. These findings are shown to indicate that the elastic contribution to the viscoelastic response of this elastomer increases more rapidly with the static deformation than does the relaxation contribution. The loss modulus, however, is found to be a separable function of time and strain effects. Hence, only one relaxation function is needed in the viscoelastic constitutive theory applied to this elastomer. The finite linear viscoelasticity theory as modified by Morman has a form which can account for these results. Predictions of the incremental stress–relaxation function from dynamic data are within 1% of experimental values.
Synthesis, characterization, and study of thermal properties of methyl‐substituted arylene sulfone ether polyimides, polyamides, and poly(amide–imides)
Authors: Adduci J. , Chapoy L. L. , Jonsson G. , Kops J. , Shinde B. M.
Published: April 2003

A number of methyl‐substituted bis[(phenyleneoxy) sulfone] dianilines were synthesized and reacted with pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA), terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), and trimellitic anhydride acid chloride (TMAC) to prepare a series of polyimides, polyamides, and poly(amide–imides), respectively. Low temperature solution and interfacial polymerization techniques were utilized to prepare the above polymers. Most of the polymers prepared formed tough, transparent flexible films. The prepared polymers were characterized by solution viscosity, thermal gravimetric analysis (dynamic and isothermal), and differential scanning calorimetry. The effect of the number and the ring substitution of methyl groups on polymer properties is discussed.
Dynamic mechanical analysis of polymers in the liquid state: Use of a perforated shim stock support
Authors: Keinath Steven E. , Boyer Raymond F.
Published: April 2003

This report summarizes some initial results on the use of a perforated brass shim stock support to extend the useful range of dynamic mechanical testing well over 100 degrees above the traditional limiting polymer softening points of Tg or Tm. Weak secondary relaxations were observed above Tg in both polyisobutylene (PIB) and polystyrene (PS) homopolymer, copolymer, and blend systems and above Tm in gutta percha (trans‐polyisoprene). The DuPont 981 Dynamic Mechanical Analyzer (DMA)–990 Thermal Analyzer system was used to characterize these weak liquid state processes. The DMA instrument deforms the specimen in flexure, thus minimizing the shear component present in some other techniques. Specimen‐coating weights are typically in the range 20–40 mg. The perforations are particularly useful for polymers having low inherent adhesion to metals or systems which are very brittle in the glassy state, e.g., low MW PS's and many methacrylates.
Analysis of the calendering of compressible fluids
Authors: Chung Tai‐Shung
Published: April 2003

Assuming that the compressible behavior of polymeric melt obeys the Spencer–Gilmore equation of state, the effect of melt compressibility on calendering process has been investigated. The compressible model is distinctly different from the incompressible model in three ways. (1) It has substantially lower maximum pressure, (2) the location having maximum pressure moves closer to the nip region; (3) the contact point shifts closer to the nip region.
Gradient innterpenetrating polymer networks. II. Polyacrylamide gradients in poly(ether urethane)
Authors: Elsabee M. Z. , Dror M. , Berry G. C.
Published: April 2003

The surface of poly(ether urethhane) is modified by preparing gradient interpenetrating polymer networks (IPNs) with polyyacrylamide hydrogels. Soveral experimental methods are used for preparing the gradient IPNs. Attenuated total reflection Fourier transform infrared (ATR‐FTIR) is used as the main characterization technique.
Crystallinity of pure and nucleated PET
Authors: Aharoni S. M. , Sharma R. K. , Szobota J. S. , Vernick D. A.
Published: April 2003

Pure and Al(OH)3‐containing PET films were prepared, quenched, and subsequently annealed under identical conditions. The level of crystallinity of the films was determined by three methods: density measurements, X‐ray crystallinity determination, and measurements by IR of the relative concentration of trans OCCO conformation in the polymer. For pure PET it was found that the percentage crystallinity measured in annealed samples by X‐ray and IR is about the same. The density measurements agree with these techniques only when the amorphous density is taken as 1.348 g/cm3. In the case of quenched pure PET, a 7% correction to the concentration of trans conformation must be introduced (in agreement with recent literature) to fit the IR results to the X‐ray and density data. Annealed PET containing Al(OH)3 crystallizes to about the same level as annealed pure PET. The agreement between X‐ray and IR data is reasonably good. In the quenched PET/Al(OH)3 there exists a higher level of trans conformation (enhanced order), probably resulting from adsorption of relatively extended PET chain segments on the surface of the hydroxide particles. These extended units may possibly serve as nucleation sites for PET crystallization upon cooling from the melt.
Photoinduced graft copolymerization of nylon 6 fibers with acrylamide. II. Characterization and evaluation of properties
Authors: Mukherjee A. K. , Sachdev H. S. , Gupta Achla
Published: April 2003

Nylon 6‐g‐polyacrylamide graft copolymer prepared by photoinduced initiation was characterized and some of its properties were evaluated. Intrinsic viscosity of the graft copolymer increased continously with percent grafting. Thermal stability decreased corresponding to the increase in add‐on %. The moisture regain, diameter, and density showed an increase with percent grafting. The acid dyeability of the graft copolymer decreased with increase in graft level, whereas the disperse dye uptake increased initially up to a graft add‐on of 28.9% and then showed a decrease.
Kinetics of swelling of cotton fibers in aqueous ethylenediamine solutions using moisture regain data
Authors: Lokhande H. T. , Pawar A. D. , Shukla S. R. , Chidambareswaran P. K. , Patil N. B.
Published: April 2003

Kinetic studies of swelling of cotton cellulose with 75% (w/w) EDA solution have been carried out. Three rates of the reaction were observed in the temperature range 10–35°C: first, the very fast rate (k1) lasting for about 10 s; second, the extremely slow rate (k2) lasting for 30–50 s; and third, once again a fast rate (k3), k1 being faster than k3. k1 was attributed to the swelling action of EDA–monohydrate in amorphous regions of cellulose; k2 was assigned to the penetration of swelling species into crystallities accompanied by breakage of H bonds in these regions; and k3 was assigned to the opening up of the crystallites. Activation energy values confirmed this trend. At higher temperatures (35–55°C), the middle rate k2 merged with k3, giving only two rates, k1 and k2+3, as the higher temperatures brought about simultaneous diffusion of swelling agent into, and decrystallization of, the crystalline portions of cellulose. EDA solution of 65% (w/w) concentration gave only two rates: the initial fast rate assigned to the swelling of the amorphous portion, followed by a slow one, operating in mesomorphous regions of cellulose, without any appreciable decrystallization. This was atributed to the important fact, viz., the absence of EDA–monohydrates in the solution.
Wide‐angle X‐ray diffraction studies of nylon–ionomer blends
Authors: Venkatesh G. M. , Fornes R. E. , Gilbert R. D.
Published: April 2003

Blends of nylon 6 with poly(acrylic acid) polyacrylamide, poly(ethylene‐co‐acrylic acid), poly(ethylene‐co‐vinyl alcohol), poly(acrylamide‐co‐acrylic acid), and polypropylene were prepared by melt blending. Annealing treatments included treatments in Vacuum, in water, and in 20% formic acid at various temperatures. WAXS (wide‐angle X‐ray scattering) patterns of melt chips and of undrawn, drawn and textured yarns were obtained. The melt chips of 100% nylon 6 crystallize in the α form while the chips of all the blends exhibit a single diffracton ring. All the blends behave similarly during different annealing treatments. When annealed in 20% formic acid at 102°C, the α structure results. The as‐spun fibers of nylon 6 and of the blends with poly(acrylamide‐co‐acrylic acid) and poly(ethylene‐co‐vinyl alcohol) exhibit a broad diffraction maximum in the region 2θ = 19–25°. The α content and its purity increase with increasing severity of the annealing treatment. The as‐spun fibers of the blend with poly(acrylic acid), on the other hand, exhibit a highly oriented γ structure which is highly resistant to conversion to the α from during the annealing treatments. Only when treated in 20% formic acid at 102° does the pure α form result. The drawn textured yarns of nylon 6 exhibit both the α and the γ forms. However, the γ content of the textured yarns from the blends varies with the type and concentration of the additives. The textured yarns from the blends with low levels (0.125%) of poly(acrylic acid) have a very high α content. It is very unusual that the as‐spun fibers with almost pure γ structure, when drawn, produce a structure with a high α content.
Influence of long chain branching on extrudate swell of low‐density polyethylenes
Authors: Hamielec L. A. , Vlachopoulos J.
Published: April 2003

An experimental study of extrudate swell has been carried out, involving five low‐density polyethylene (LDPE) samples of approximately the same molecular size but of different frequencies of long‐chain branching (LCB). The results show that the samples with higher frequencies of LCB exhibit a tendency to swell more than samples of lower frequency. This tendency is more pronounced for short L/D dies and high shear rates. It seems possible that LDPE samples of varying LCB frequencies can be differentiated by determining the swelling ratio (d/D) with orifice dies (L/D ⋍ 0) at high throughput rates.
Effect of high pressure on some electrophysical properties of polymers: Polyconjugated systems doped by iodine
Authors: Zhorin V. A. , Beshenko S. I. , Berlin Yu. A. , Enikolopian N. S.
Published: April 2003

The effect of pressure P up to 2.5 × 103 MPa on the dielectric constant ε and conductivity G of a number of conjugated polymers doped by iodine has been studied. Polyphenylacetylene prepared with FeAcAc, polyphenylacetylene obtained with Ziegler catalyst, anionic polydiphenylacetylene, and polydiphenylbutadiene were chosen for investigation. It has been found that after doping the values ε and G increase and strongly depend on P. The possible mechanism of this phenomenon has been discussed.
Isothermal transient current studies in cellulose acetate films
Authors: Kumar Ashok , Nath Rabinder
Published: April 2003

Step voltage transient current studies have been made in cellulose acetate films as a function of filed and thickness. A logarithmic plot (Scherr‐Montroll plot) of the transient current vs. time gives a knee at a time tT, which is interpreted as the transit time of the charge carrier. The value of the carrier mobility has been estimated to be 3.9 × 10−9 cm2.V−1.S−1 in cellulose acetate film. The carrier mobility in iodine‐doped (2% w/w) cellulose acetate film has also been determined from Scher‐Montroll plot and is found to be 3.3 × 10−7 cm2.V−1.S−1.
Synthesis of rigid polyurethane foams from oligoester alcohols based on the residues from the distillation of crude dimethyl terephthalate and recrystallization of the dimethyl terephthalate/dimethyl isophthalate fraction
Authors: Troev K. , Todorov K. , Borisov G.
Published: April 2003

Oligoester alcohols are synthesized from the resudes from the distillation of crude dimethyl terephthalate and recrystallization of the fraction dimethyl terephthalate/dimethyl isophthalate, diols, triols, tetrols, and tall oil. The polyol component containing various oligoester alcohols is suitable for preparing rigid polyurethane foams with good thermal stability and improved resistance to combustion.
Syntheses and properties of urethane prepolymers and their corresponding crosslinked films
Authors: Yang Chin‐Ping , Wu Wen‐Lin
Published: April 2003

Trimethylol propane (TMP), polyglycol (PG), and toluene diisocyanate (TDI) were reacted in various molar ratios to produce TMP–TDI–PG–urethane prepolymers and then mixed with equivalent isocyanate generator (Desmodur AP‐Stable) in a mixture of m‐cresol and naphtha to give polyurethane varnishes which finally became crosslinked films by the casting method. The mechanical properties and viscoelasticities of the PG‐modified and PG‐free polyurethane crosslinked films and the practicability of magnet wires coated with them were studied in this article. Three different PGs used in this experiment were polyethylene glycol, PEG(#400), polypropylene glycols, PPG(#1000) and PPG(#2000). In the case of adding PEG(#400) for modification, strength at break increased but elongation did not change. Meanwhile, glass transition temperature (Tg) shifted to lower temperature with increasing molar ratio. In the case of adding PPG(#1000) and PPG(#2000) for modification, the samples changed their mechanical properties from hard and brittle to soft and tough. With increasing molar ratios, strength at break initially increased and then decreased gradually, and elongation varied a lot and was consistently contrary to strength at break. Tg occurred at two regions: one at high temperature above 100°C for small molar ratios and the other at low temperature below 100°C for high molar ratios. Besides, for all PG‐modified polyurethane crosslinked films, strength at break showed a local maximum at TMP/TDI/PG = 1/1/0.5, which indicated their homogeneous structures. The molar ratios of PG‐modified urethane prepolymers, which are suitable for manufacturing practical magnet wires according to testing method JIS‐C‐3211, are as follows: TMP/TDI/PPG(#100) = 1/1/0.15–0.35 and TMP/TDI/PPG(#2000) = 1/1/0.10. PEG(#400)‐modified magnet wires were not accepted on the aging test. The properties of crosslinked films of practical magnet wires are generally as follows: strength at break at 200–700 kg/cm2, elongation less than 41%, and Tg at 100–200°C.
The radiation crosslinking of poly(vinyl chloride) with trimethylolpropanetrimethacrylate. III. Effect of diundecyl phthalate: Chemical kinetics of a three‐component system
Authors: Bowmer T. N. , Vroom W. I. , Hellman M. Y.
Published: April 2003

The radiation chemistry of poly(vinyl chloride) (PVC) blended with trimethylolpropanetrimethacrylate (TMPTMA) and diundecyl phthalate (DUP) has been examined. This three‐component mixture contains a base resin (PVC), a crosslinking sensitizer (TMPTMA), and a physical modifier (DUP). These are the basic components in any radiation‐curable coating. The kinetics and mechanism of the crosslinking reactions were studied with reference to the dependence on radiation dose and blend composition. The polyfunctional TMPTMA underwent polymerization incorporating the PVC into a 3‐dimensional network. DUP remained chemically inert during the irradiation, not being bound to the network. However, DUP by plasticizing the macromolecules and diluting the monomer, changed the kinetics extensively. DUP enhanced TMPTMA homopolymerization, TMPTMA grafting, and PVC crosslinking reaction rates. The effect on the competition between polymerization, grafting, and degradation reactions was examined in terms of enhanced mobility of the reacting species. The influence of these kinetic considerations in selecting a blend composition for a coating application was discussed.
Accelerated heat age testing of phenolics: Applicable temperature range
Authors: Stransky Paul D. , Yates W. Ross , Johnson Julian F.
Published: April 2003

An upper bound in temperature for accelerated heat aging of a phenolic molding compound has been determined. Oxidative degradation based on time and temperature follows the Arrhenius relationship up to this upper temperature bound, after which thermal shock becomes the primary mode of failure.
On Zhurkov's approach to the strength of solids
Authors: Papazian Harold A.
Published: April 2003

Two modifications to the Zhurkov kinetic concept of static (creep) rupture is discussed: (a) solids where the common pole τ0 is much larger than that associated with a vibrational frequency of bonded atoms in the solid and (b) materials where a common pole does not occur. Both cases are discussed within the Zhurkov framework. The activation thermodynamics and the association with transition state theory are revealed.
Reinforcement mechanism of polyester‐fiber‐reinforced rubber—A model study
Authors: Xue Gi , Koenig Jack L. , Wheeler Donald D. , Ishida Hatsuo
Published: April 2003

The reinforcement mechanism of polyester tire cord was studied by Fourier‐transform infrared spectroscopy using various model compounds. Three model compounds representing the main chain of polyester and the terminal groups, namely carboxylic acid and hydroxyl groups, were used. Chemical reactions between these polyester models and an epoxy functional silane coupling agent were studied qualitatively as well as quantitatively. Among the many possible reactions, the reaction between the carboxylic acid and epoxy group was found to proceed readily. Kinetic studies of the major reactions also show quantitative differences in their activation energies as well as the rate constants. Based on the quantitative studies, we have estimated the expected rate of interfacial reaction at the heat treating temperature of polyester tire cord.
Studies of jute fiber composites with polyesteramide polyols as interfacial agent
Authors: Mukherjea R. N. , Pal S. K. , Sanyal S. K.
Published: April 2003

Polyesteramide polyols have been synthesized by melt condenstion using a mixture of alkanolamines, polyethylene glycols, and dicarboxylic acids/anhydrieds, and the behavior or resin samples as interfacrial agents in unidirectional as well as random composites of jute/epoxy and jute/polyester has been evaluated. Mechanical properties of these composties with or without interfacial agents have been determined along with the effect of water uptake on such properties. The incorporation of polyesteramide polyol (PEAP) resins as interfacila agents has been found to significantly improcve the mechanical properties of jute fiber composites. It has also been found that increasing the hydroxyl value of PEAP results in a better bonding of the composities up to a certain optimum limit of hydroxyl value beyond which the molecular weight of the interfacila agent as well as its bonding strenght decreases. Use of PEAP resin of optimum hydroxyl value and molecular weight also significantly improves the water resistance capacities of jute/epoxy composites.