bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction kinetics of vinyl acetate emulsion polymerization
Authors: Chern Chorng‐Shyan , Poehlein Gary W.
Published: April 2003

Transport of free radicals out of latex particles into the aqueous phase plays an important role in the emulsion polymerization of vinyl acetate. This so‐called “desorption” process involves chain transfer to monomer which generates a mobile and rather stable monomer‐unit free radical followed by the diffusion of this free radical out of the latex particle. A kinetic model is developed based on the reaction mechanisms of such an emulsion system. The experimental data available in the literature are used to test the model under various polymerization conditions. Reasonable agreement between the model predictions and experimental data is observed.
Polymer degradation in porous media flow
Authors: Farinato Raymond S. , Yen Wei S.
Published: April 2003

The hydrodynamic degradation of high molecular weight poly(acrylamide‐co‐Na acrylate) in 1M NaCl in porous media flow was studied as a function of polymer concentration in the dilute and semidilute concentration ranges. Porous media rheometry was used to monitor molecular weight changes due to chain scission. At equivalent superficial velocities of flow through a glass bead pack, polymers at dilute concentrations showed greater loss of molecular weight than polymers at semidilute concentrations.
Correlation of the solubility of volatile liquids in molten polymers
Authors: Han Chang Dae
Published: April 2003

The solubility of volatile liquids at infinite dilution (i.e., in the Henry's law region) in poly(vinyl acetate) (PVAc) and polystyrene (PS) at elevated temperatures has been correlated by plotting ln(1/Kp) against (Tc/T)2, where Tc is the critical temperature of the solute and Kp is Henry's constant at temperature T and a total pressure of approximately at 1 atm, defined as P1 = KpV10, where P1 is the partial pressure of the solute in the vapor phase and V10 is the solubility (cm3 solute per g polymer at 273.2 K and 1 atm). For this correlation, we have used experimental data available in the literature for 16 solutes covering 81 data points for PVAc and 17 solutes covering 82 data points for PS. We have calculated values of 1/Kp from the literature data reported in terms of the retention volume Vg0, weight‐fraction Henry's constant H1, and activity coefficient at infinite dilution Ω1∞. We have made the following observations: (1) for PVAc, ln(1/Kp) = −1.564 + B(Tc/T)2; and (2) for PS, ln(1/Kp) = −2.028 + B(Tc/T)2. In both cases, we found that values of B, the slope in the ln(1/Kp) versus (Tc/T)2 plots, vary with the acentric factor ω of the solutes. It has been found that, in both PVAc and PS at the same value of ω, values of B for slightly polar aromatic solutes are larger than those for nonpolar aliphatic solutes. Further, in PS at the same value of ω, values of B are smaller for strongly polar solutes than for slightly polar solutes, whereas in PVAc the opposite trend holds. This observation may be interpreted as that the solubility of strongly polar solutes in a polar polymer (e.g., PVAc) is greater than that of slightly polar and nonpolar solutes, whereas the solubility of strongly polar solutes in a nonpolar polymer (e.g., PS) is less than that of slightly polar solutes but greater than that of nonpolar solutes. The dependence of B on ω, observed in this investigation, is at variance with the correlations reported by Tseng, Lloyd, and Ward for PVAc and by Stiel and Harnish for PS.
Synthesis and characterization of castor oil urethane triamine networks
Authors: Saikumar C. , Rajadurai S.
Published: April 2003

Castor oil was polymerized with diisocyanate and crosslinked with primary triamine (Jeffamine T‐403) to form networks. The effect of triamine as a crosslinking agent on rubbery castor oil urethane elastomer was determined by measuring network parameters such as average molecular weight between crosslinks (MC) number of polymer chains per unit volume (N), tensile strength, and modulus of the networks. The crosslinking density was varied by varying the ratio of NCO : NH2 from 0.60 to 0.95. The results indicated the formation of highly crosslinked elastomers at all NCO : NH2 ratios employed. The tensile stregth and modulus increased with increasing crosslink density up to a value of NCO : NH2 0.85 and after this there was no significant change, indicating the maximum limit of improvement attainble in terms of network characteristics.
Polymerization of olefins through heterogeneous catalysis. VII. Particle ignition and extinction phenomena
Authors: Hutchinson R. A. , Ray W. H.
Published: April 2003

The possibility of multiple steady states for a polymer particle is examined for propylene and ethylene, liquid and gas phase polymerizations. It is shown that multiple steady states should not occur in conventional diluent slurry polymerizations, but are always a possibility for gas phase and bulk propylene slurry reactions. Simulations to determine particle temperatures as a function of particle diameter show that polymer melting is predicted immediately upon catalyst injection for many cases in a gas phase reactor and for some cases in bulk polymerization. The practical implications of this result are discussed.
Photolysis of segmented polyurethanes. The role of hard‐segment content and hydrogen bonding
Authors: Hoyle Charles E. , Kim Kyu‐Jun , No Y. G. , Nelson G. L.
Published: April 2003

The photodegradation of segmented polyurethanes based on methylene 4, 4′‐diphenyldiisocyanate (MDI) is shown to be dependent on the physical structure of the polymer. As the hard segment content of the polyurethane is increased, the photodegradation efficiency is lowered. In particular, the extent of the photolytic decomposition is inversely dependent on the degree of hydrogen bonding in the aryl carbamate groups in the polyurethane backbone. Utilizing appropriate model compounds for comparison, the formation of the ortho photo‐Fries rearrangement product, as detected by fluorescene spectroscopy, is also shown to be dependent onthe degree of hydrogen bonding. In general, the restrictive mobility imposed by hydrogen bonding is a critical factor which must be considered in the photochemistry of segmented polyurethanes.
Investigation of PVC life at sinusoidal loading
Authors: Natov M. , Vassileva St. , Trifonov P.
Published: April 2003

The durability of polyvinylchloride (PVC) at static and cyclic loads during establishing of tensile and flexural strength is studied. It is found out that bulk static and cyclic durability can be described by a kinetic equation assuming that the tension changes the temperature‐energy factor. During testing of tensile strength it is established that the maximum deformation at break depends upon the tension of loading in an elaborate way with the existance of a peak at 32 MPa.
Role of reinforcing material in ion exchange membranes prepared by the paste method
Authors: Mizutani Yukio , Ikeda Katsuhiro
Published: April 2003

Ion exchange membranes prepared by the paste method contain polyvinylchloide cloth as a reinforcing material, which is necessarily used to endow the membranes well‐balanced properties: electrochemical and mechanical properties. The role of the reinforcing material was studied in terms of the membrane structure.
Photosensitized grafting of acrylamide and hydroxyethyl methacrylate onto cellulose
Authors: Silva M. Alves Da , Gil M. Helena , Lapa Elisa , Guthrie J. T.
Published: April 2003

The photoinitiated copolymerization of acrylamide and hydroxyethyl methacrylate onto cellulose substrates, from acetone/water solutions, was studied using isopropyl thioxanthone as the photoinitiator. The graft copolymerization was carried out over a range of monomer and photoinitiator concentrations. Grafting is shown to be dependent on the nature of the monomer and the concentration of monomer and photoinitiator. In the case of acrylamide, it was found that there is an optimum concentration of the photoinitiator for grafting to occur effectively. The kinetics of graft copolymerization were studied in some detail and the results are considered.
A critical evaluation of the single‐point determination of intrinsic viscosity
Authors: Chee K. K.
Published: April 2003

The general validity of four single‐point methods for intrinsic viscosity ([η]) determination is verified to be unacceptable even for dilute polymer solutions. Also, a direct method based on a truncated version of Huggins equation is shown to be less practical in that it involves advanced experimentation and is valid only at sufficiently low concentrations. In view of the shortcoming and sophistication of the above procedures, an effective approach is introduced to resolve these problems. This novel computation expresses the Huggins coefficient in terms of [η], and the associated equations are calibrated against the polymer system of interest. This procedure is tested using various polymer solutions with results compatible with those acquired by other means. The advantage of the proposed technique is discussed.
Permselectivity of cellulose acetate membranes; separation of H2/CO mixtures and the effect of added transition metals
Authors: Feldman Julian , Shim Il Wun , Orchin Milton
Published: April 2003

Cellulose acetate membranes permit permeation of H2 and CO2 but are relatively impervious to CO and N2. Permselectivity was demonstrated by effective separation of H2 from its mixtures with CO. The presence of RuCl3 in the membrane does not result in any appreciable change in permselectivity. The exposure of RuCl3‐ and RhCl3‐modified membranes to H2/CO mixtures results in the formation of RuCl2(CO)x and [RhCl(CO)2]2, respectively. However, these complexes are not covalently anchored to the cellulose acetate matrix and apparently function only as additives that block access to the press and channels in the cellulose acetate membrane.
Homo‐ and copolymerization of ethylene with highly active catalysts based on TiCl4 and grignard compounds
Authors: Muñoz‐Escalona A. , García H. , Albornoz A.
Published: April 2003

In this paper, the synthesis of different catalytic systems based on the reduction of TiCl4 by Grignard compounds has been systematically studied. The catalysts exhibited the highest activities when used in the copolymerization of ethylene with n‐hexene. The profile of the kinetic curves also changed when the comonomer was present during polymerization. By thermal analysis and scanning electron microscopy techniques, it could be found that the incorporation of the comonomer to the polymer chain brings about a decrease in the polymer crystallinities and an increase in the porosities of the growing particles. Due to that, the diffusion of the monomer to the catalytic active centers takes place more easily, consequently increasing the polymerization rate. In addition, catalysts control better the morphology (size and shape) of the nascent polymer particles when used for copolymerization.
Silicone polymerization by glow discharge application
Authors: Hasirci N.
Published: April 2003

Polymerization of hexamethyldisiloxane (HMDS) on aluminum by application of capacitively coupled plasma was carried out under different polymerization conditions. The effect of applied frequency, power, and discharge duration on polymerization rate was investigated. Film adhesion was found to be directly related to applied frequency and power. Polymer deposits were examined with SEM and ATR, and the effect of the coat on wattability was sought by measuring the contact angles. The chemical structure of the coat was affected by the energy density applied during coat preparation.
Interaction of cation‐exchange membrane with polycation I. Poly(N‐methyl‐4‐vinylpyridinium chloride)
Authors: Ohmura Nobuhiko , Kagiyama Yasuhiro , Mizutani Yukio
Published: April 2003

We elucidated the effect of the molecular weight of poly(N‐methyl‐4‐vinylpyridinium chloride) (PMVP) on its adsorbed or ion‐exchanged amount on the cation‐exchange membrane and the preferntial permselectivity of the membrane for sodium ion to calcium ion. The amount of the adsorbed or ion‐exchanged PMVP increases with time and then attains to a definite value at a definite concentration. Also, the ultimate value increases with increasing the concentration of PMVP. When the molecular weight of PMVP is 3090, the ratio of the pyridinium groups of PMVP ion‐exchanged with the sulfonic acid groups on the membrane surface to the total pyridinium groups of the cohered PMVP is in the range of 70–80%. The relative transport number of calcium ions to sodium ions(PNaCa) decreases with increasing the amount of adsorbed or ion‐exchanged PMVP and the numbe rof non‐ion‐exchanged pyridinium groups of PMVP and the number of non‐ion‐exchanged pyridinium groups of PMVP on the membrane surface. The smaller the molecular weight of PMVP, the more the adsorbed or ion‐exchanged amount and the more preferable the permselectivity for sodium ion.
Dilute solution behavior and Mark‐Houwink constants for a non‐linear cationic polyelectrolyte
Authors: McCarthy Kevin J. , Burkhardt Charles W. , Parazak Dennis P.
Published: April 2003

Mark‐Houwink coefficients and radius of gyration dimensions are presented for six unfractionated cationic polyelectrolytes of the poly(dimethylamine‐epichlorohydrin‐ethylendiamine) type. The copolymer system was studied in .05M, .10M, and 1.0M NaCl, and .12M NaClO4 aqueous solutions. Their solution behavior, as studied by intrinsic viscosity and light‐scattering technique, suggests these polymers adopt a somewhat spherical or star‐like conformation in aqueous salt solutions.
Recovery of uranium from seawater V. Preparation and properties of the macroreticular chelating resins containing amidoxime and other functional groups
Authors: Egawa Hiroaki , Nakayama Morio , Nonaka Takamasa , Yamamoto Hideki , Uemura Keiji
Published: April 2003

We have synthesized macroreticular chelating resins containing amidoxime groups from acrylonitrile (AN)‐divinylbenzene (DVB)‐alkyl acrylate, alkyl methacrylate, or vinylpyridine (VPy) copolymer beads. It was found that the chelating resin (RNMH)‐containing amidoxime groups prepared from AN‐DVB‐methyl acrylate (MA) indicated the highest adsorption ability for uranium in seawater. Hydroxamic acid and carboxylic groups in addition to amidoxime groups were formed during the reaction of the copolymer beads with a methanol solution of hydroxylamine. The adsorption ability for uranium was greatly influenced by the physical pore structure (macropore) and the pore structure formed by the swelling(micropore). RNMH (RNMH10‐10) prepared with 10 mol% of DVB and 10 mol% of MA had the highest adsorption ability and physical stability for uranium. On the other hand, improved adsorption ability for uranium was not observed in the case of the macroporous resins (RNPyH) prepared by the copolymerization of VPy as the basic component. After seawater was passed through the column packed with RNMH10‐10 at a space velocity (SV) of 180 h−1 (up‐flow) for 10 days, the amount of uranium adsorbed on the resin was about 100 mg/dm3‐R and 260 mg/kg‐R.
Transport of ethylene oxide through polymer films
Authors: Phatak A. , Burns C. M. , Huang R. Y. M.
Published: April 2003

The transport of gaseous ethylene oxide (EtO) in several polymer films is studied using the carrier gas method of measurement. Permeability, solubility, and diffusion coefficients describing ethylene oxide (EtO) transport in polypropylene, polyvinylchloride, Teflon‐FEP copolymer, and polyethylene films have been obtained over a 30 Celsius degree range at a low concentration of EtO using the carrier gas method of measurement. The results indicate that the diffusion of EtO in polyethylene is independent of penetrant concentration over the range of concentrations used. However, concentration‐independent diffusion could not be verified directly for the other films studied. Two different techniques of determining diffusion coefficients were used, and within the precision of the data both yield the same result. An excess enthalpy of solution for the solubility of EtO in Teflon‐FEP copolymer was calculated, an observation that suggests that dual‐mode sorption may be taking place.
Dynamic mechanical behavior and structure of polyurethaneimides
Authors: Masiulanis B. , Hrouz J. , Baldrian J. , Ilavský M. , Dušek K.
Published: April 2003

Dynamic mechanical behavior and X‐ray diffraction of two series of segmented polyurethaneimides (PUI) prepared either from poly(ethylene adipate) glycol (PEA), pyromellitic dianhydride (PMDA) and 4,4′‐diphenylmethane diisocyanate (MDI), or from PEA, PMDA, and a mixture of 2,4‐ and 2,6‐tolylene diisocyanate (TDI) were studied. All samples have a two‐phase structure of the soft polyester (PE) phase and hard polyimide (PI) phase. PI microdomains containing MDI units are semicrystalline, whereas those with TDI are crystalline only at highest contents of TDI. The storage modulus E′ increases with increasing fraction of the hard phase. The MDI‐containing hard phase has a stronger effect on E′ and also makes the plateau on the dependence of E′ on temperature more pronounced.
New aspects in cationization of lignocellulose materials. VIII. Modification of immitted spruce wood with quarternary ammonium groups
Authors: Šimkovic Ivan , Alföldi Juraj , Antal Miroslav
Published: April 2003

Immitted spruce wood meal (ISWM) was modified with 3‐chlor‐2‐hydroxypropyltrimethyl‐ammoniuchloride (CHMAC) or 1,3‐bis(3‐chlor‐2‐hydroxypropyl)imidazoliumhydrogensulphate (BCHIHS) in alkaline medium. The obtained material was gradually extracted with water and 5% NaOH. The yields of water‐soluble hemicelluloses modified with quarternary ammonium groups were lower in comparison to healthy spruce material obtained under the same conditions but even more material could be obtained from ISWM‐holocellulose. The quantity of alkali‐soluble polysaccharides from ISWM was the same as obtained from undamaged spruce. The residues after alkali extractions are suitable ion exchangers with low solubility in dilute alkali solutions. The yields of extracts from material modified with BCHIHS were lower than yields of extracts from material modified with CHMAC because ISWM was crosslinked when alkylated with bifunctional chemicals.
Release routes of incorporated desmetryn from EVA‐films. An example for the behavior of low volatility additives in polymers under outdoor conditions
Authors: Kraxenberger M. , Pfister G. , Bahadir M.
Published: April 2003

Release of desmetryn into the gas phase from films of ethylene‐vinyl acetate copolymer, in which the herbicide was incorporated for special agricultural applications, was investigated for comparison with release into water and under outdoor conditions. It could be shown that the rate of release of the active chemical into the gas phase was negligible compared with that into water and only slightly dependent on temperature in the range 0–75°C.
Model for prediction of the elastic response of reinforced materials over wide ranges of concentration
Authors: Farber Jorge N. , Farris Richard J.
Published: April 2003

A model for the prediction of the elastic response of reinforced materials over wide ranges of concentration is presented. The method is based on the mathematical analogy between the motion of particles suspended in viscous media and the elastic deformation of solids. The system is locally described by linearized forms of the elastic moduli. The validity of these relations is then extended to all concetrations under the assumption that any new portion of filler “sees” the existing structure as a noniteracting homogeneous matrix. The method predicts the behavior of reinforced materials with solid spherical inclusions and foams over wide ranges of concentration. The model, free from adjustable parameters, shows excellent agreement with existing experimental data. The extension of the method to other inclusion geometries is straightforward.
Electro‐copolymerization of acrylonitrile and methyl acrylate onto graphite fibers
Authors: Chang J. , Bell J. P. , Shkolnik S.
Published: April 2003

Electro‐copolymerization of methyl acrylate, acrylic acid, methacrylic acid, acrylamide, and methyl methacrylate with acrylonitrile onto graphite fibers has been successfully done in our laboratory. The coatings are relatively uniform and their properties, especially their modulus, can be systematically varied by controlling the monomer ratio in the eletrolyte solution. This technique is being used to introduce a ductile interlayer of contrlled composition and thickness between the composite fibers and matrix. Copolymers of methyl acrylate and acrylonitrile formed by this technique are random copolymers, with Tg′s varying from 10 to 90°C. These copolymers have fairly high molecular weight, in the range of 100,000 g/mol. Monomer reactivity ratios were determined, based upon free radical polymerization kinetics, from cyclic voltammetry. An indirect initiation mechanism is suggested. Bonding between interlayer and matrix can be improved by introducing vinyl monomers with proper functional groups, capable of reacting with the epoxy resin, at the last stage of the electropolymerization process.
The effect of stretching conditions on properties of amorphous polyethylene terephthalate film
Authors: Sharma S. K. , Misra A.
Published: April 2003

The effect of stretching condition on stress‐induced crystallization of amorphous polyethylene terephthalate (PET) film has been studied. Cast PET film was stretched at 85°C with stretching rates ranging from 100% per minute to 600% per minute for various stretching ratios. The stretched film samples were annealed at 140°C both under tension as well as under relaxed conditions. Tensile properties were determined using Instron Tensile Tester and results were compared. Tenacity, yield stress, and initial modulus were found to increase while elongation at break decreased with the increase in stretching rate. The degree of crystallinity was measured by x‐ray diffraction as well as density methods. Birefringence and crystalline orientation factor values were determined experimentally and using these, amorphous orientation factor values were calculated. Birefringence, crystalline orientation and amorphous orientation values were found to increase with the increase in stretching rate. These studies showed that at low stretching rates a significant amount of relaxation takes place, resulting in lower orientation and strength. On the other hand, at higher stretching rates relaxation is minimized thus providing high orientation and strength. Upon annealing the crystallinity values increased as expected, however the trend of orientation and mechanical properties with respect to stretching rate was similar to those of unannealed films.
Mechanical properties of grafted casein films
Authors: Somanathan N. , Arumugam V. , Sanjeevi R. , Narasimhan V.
Published: April 2003

Casein was grafted with mixtures of acrylonitrile (AN) and n‐butyl methacrylate (n‐BMA). The mole ratios of AN: n‐BMA were 0.9:0.1 and 0.8:0.2. The mechanical properties of the grafted casein films were studied under uniaxial and biaxial stress conditions. A reduction in longitudinal stress and elongation at break was observed with the simultaneous application of lateral stress. Scanning electron micrographs of the stretched films (uniaxial and biaxial stress) are also presented.
Synthesis, characterization, and polymerization of bismaleimides and bisnadimides chain‐extended by N,N′‐substituted ureas
Authors: Melissaris Anastasios P. , Mikroyannidis John A.
Published: April 2003

A series of new polymer precursors such as bismaleimides, bisnadimides, and bismethylnadimides chain‐extended by N,N′‐substituted ureas was synthesized and characterized. They were prepared by reacting a diamine containing ureylene linkages with maleic/nadic/methylnadic anhydride. Another alternative method for preparing these monomers included reaction of a diamine (1 mol) with an equimolar amount of maleic/nadic/methylnadic anhydride, subsequent reaction with a diisocyanate (0.5 mol) followed by cyclodehydration of the itermediate diamic acid. The monomers were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Their thermal polymerization was investigated by differential thermal analysis (DTA). The thermal stability of the polymers was evaluated by dynamic thermogravimetric analysis (TGA) and isothermal gravimetric analysis (IGA). No weight loss was observed when the polymers containing arylureas in their backbone were heated up to 324–334°C in nitrogen or air atmospheres. Their anaerobic char yield at 800°C fluctuated between 41 and 61%.
Formation of primary particles in vinyl chloride polymerization
Authors: Törnell Bertil , Uustalu Jaan
Published: April 2003

The formation of primary particles in agitated bulk polymerizations of vinyl chloride was found to proceed in two stages. The first stage occurred at the very beginning of the polymerization; the second stage started as the initially nucleated particles began to agglomerate, and continued up to at least 7% conversion. Upon formation, the primary particles were stable and did not agglomerate until reaching a limiting size, which was found to be lower at higher stirring speeds. The number of particles formed in the first stage was independent of agitation and other polymerization parameters. The rate of particle formation during the second stage was equal to the rate of particle agglomeration. Thus the total number of primary particles formed was determined almost exclusively by the rate of particle agglomeration. Addition of the surfactant Span 20 caused an increase in the total number of primary particles. Also, this addition increased the tendency of the particles to fuse together after agglomeration. These effects can be understood to be a consequence of particle destabilization by the surfactant. When a small amount of a high molecular weight PMMA was dissolved in the monomer, the polymerization behaved quite differently. In this case, the primary particles were prevented from agglomeration, reaching a limiting size independent of stirring speed.
Synthesis of polymer materials by low energy electron beam. III. Effects of polymerization temperature in EB solid‐state polymerization of semicrystalline urethane‐acrylate film
Authors: Ando Masayuki , Uryu Toshiyuki
Published: April 2003

In an electron beam (EB) polymerization of a urethane‐acrylate prepolymer, the polymerization temperature greatly affected the structure and properties of the resulting gel film. Urethaneacrylate, which was synthesized by the reaction of poly(butylene adipate)diol, 4,4′‐diphenylmethane diisocyanate, and 2‐hydroxyethyl acrylate, was used as a prepolymer. The prepolymer was semicrystalline and showed a melting point in the region of 50–60°C. The maximum polymerization rate of the prepolymer was obtained when the prepolymer film was irradiated in the temperature range of 25–40°C. EB polymerization below the melting point (Tm) of the prepolymer produced semicrystalline polyurethane‐acrylate gel films with a spherulitic texture. On the other hand, EB polymerization above the Tm destroyed the crystalline phase of the prepolymer to give transparent gel films. The gel film cured below the Tm had higher stress at yield, Young's modulus, and tensile strength than those cured above the Tm. Such temperature effects are attributed to whether or not the EB polymerization proceeds with retention of crystalline structure of the prepolymer.
Rheological properties of liquid crystalline solutions of ethyl celluloses with different molecular weight in m‐cresol
Authors: Suto Shinichi , Ohshiro Masahiko , Nishibori Wataru , Tomita Hisashi , Karasawa Mikio
Published: April 2003

Steady‐state shear rheological properties of liquid crystalline solutions of four ethyl celluloses (ECs) were determined at a low shear rate (1 s−1) and at relatively high shear rates by using two rheometers (cone‐plate and capillary types), and were compared with those of liquid crystalline hydroxypropyl cellulose (HPC). The effect of molecular weight (MW) on the viscoelastic behavior was also determined. The viscoelastic behavior was also determined. The viscometric behavior of EC solutions was similar to that of HPC solutions: (1) with respect to temperature, the shear viscosity (η) at shear rate of 1 s−1 exhibited a minimum (ηmin) and a maximum (ηmax), and the concentration–temperature superposition for η could be applied; (2) the behavior of η at relatively high shear rates as a function of shear rate or polymer concentration was typical of lyotropic liquid crystals. The MW dependence of ηmin was greater than that of ηmax for EC solutions. The behavior of the elastic parameters such as Bagley correction factor (v), entrance pressure drop (ΔPent), and die swell (B) at relatively high shear rates for EC solutions was essentially similar to that for HPC solutions: (1) the shear rate or stress dependence of the elastic parameters was greatly dependent on whether the polymer solution was in a single phase or biphase; (2) with respect to concentration the elastic parameters showed a maximum and a minimum and the maximum or minimum point for each parameter was not always identical to each other. η for the isotropic or fully anisotropic solutions at a given concentration (C) increased, whereas η for the solutions in the vicinity of the biphasic region showed a minimum, with respect to MW. The slope of η at a given shear rate vs. CMw depended on shear rate, and this slope for the isotropic solutions appeared to be greater than that for fully anisotropic solutions. ΔPent and v at a given concentration showed either a monotonical increase or a maximum or minimum with MW, and this behavior was not fully consistent with that of η. B for the isotropic solutions increased and B's for both biphasic and fully anisotropic solutions were almost constant, with MW.
Infrared spectral study on the heat curing reaction of glycerin‐terminated urethane prepolymers
Authors: Yang Chin‐Ping , Lee Lung‐Ta
Published: April 2003

Glycerin, toluene diisocyanate (TDI), and polyglycol (PG) were reacted at various molar ratios to produce glycerin‐terminated urethane prepolymers of different molecular weights. The prepolymers were mixed with equivalent phenol‐blocked trimethylol propane–TDI–urethane triisocyanate in m‐cresol to give a coating solution. The solution was coated and baked to give polyurethane crosslinked films. The changes of the functional groups during the crosslinking reaction and the mechanical properties of the polyurethane crosslinked films were studies. Experimental results show that the phenol‐blocked urethane triisocyanate will deblock phenol to regenerate free isocyanate groups above 120°C and then react with the hydroxyl groups of urethane prepolymers. At 220°C, the rate of deblocking phenol to regenerate isocyanate groups is faster than that of the reaction of urethane prepolymers with isocyanate groups. The deblocking reaction is contemporaneous with the reaction of isocyanate groups with hydroxyl groups, so that the characteristic absorption peaks of isocyanate groups can be observed from IR spectra during the crosslinking reaction. The absorption peak of isocyanate groups gradually decreased with the crosslinking reaction, but the absorption peak increased after curing for about 50–60 min. This feature is caused by the reactivity of the secondary hydroxyl groups of glycerin which is slower than that of the primary hydroxyl groups of glycerin.
Flame‐retardation studies of poly(ethylene terephthalate) fabrics treated with tris dibromo alkyl phosphates
Authors: Day M. , Suprunchuk T. , Omichinski J. G. , Nelson S. D.
Published: April 2003

The flammability characteristics of tris(2,3‐dibromopropyl) phosphate (TRIS‐BP), a known carcinogen, has been compared with other tris dibromo alkyl phosphates which show reduced mutagenic responses in experimental studies. The effectiveness of these alternative chemicals in releasing hydrogen bromide (HBr), a recognized combustion inhibitor, has been measured and the results compared with flammability evaluation of polyester fabrics treated with these chemicals. Results indicate that tris(2,3‐dibromo‐3,3‐dimethyl propyl) phosphate, while having reduced mutagenicity and nephrotoxicity in comparison to TRIS‐BP, exhibits excellent flame‐retardant characteristics when applied to polyester fabrics. Meanwhile, other chemicals studied show comparable flame retardation to TRIS‐BP, but with substantial reduced mutagenicity.
Composite materials of radiation‐treated coconut fiber and thermoplastics
Authors: Owolabi O. , Czvikovszky T.
Published: April 2003

Following our previous work using fibrous biomass byproducts for radiation‐treated composite materials, polypropylene and two different kinds of PVC have been compounded with chopped coconut fiber (coir). Preirradiation of coir has been applied together with some crosslinking additive to achieve chemical bond between thermoplastics and fibrous biopolymer. Effect of addition of 10–50% coir to PVC and PP on the processability was monitored by Brabender plastograph. Dynamical mechanical analysis (DMA) data as well as tensile and impact strength of these coir composites have not been found superior to that of the starting thermoplastics. Considering, however, coconut fiber as a cheap filler, composites with acceptable tensile and impact strength could be produced with coir content as high as 30%.
Morphology of water‐blown flexible polyurethane foams
Authors: Armistead James Paul , Wilkes Garth L. , Turner Robert B.
Published: April 2003

A series of four TDI–polypropylene oxide (PO) water‐blown flexible polyurethane foams was produced in which the water content was varied from 2 to 5 pph at a constant isocyanate index of 110. A portion of each foam was thermally compression molded into a plaque. The morphology of both the foams and plaques was investigated using dynamic mechanical spectroscopy (DMS), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), scanning electron microscopy (SEM), swelling, wide angle X‐ray scattering (WAXS), and small angle X‐ray scattering (SAXS). A high degree of microphase separation occurs in these foams, and its degree is nearly independent of water (hard segment) content. In the foam with the lowest water content the morphology possesses many similarities to that of typical linear segmented urethane elastomers. Small hard segment domains are present with a correlation distance of about 7.0 nm. When the water content is increased a binodal distribution of hard segment material appears. There are the small hard segment domains typical of segmented urethane elastomers as well as larger “hard aggregates” greater than 100 nm in size. The larger domains are thought to be aggregates of rich polyurea that develop by precipitation during the foaming reaction. WAXS patterns of the foams suggest urea and possibly hard segment ordering that may be of a paracrystalline nature but certainly lacking in true 3‐dimensional crystallinity.
Deformation behavior of HDPE/(PEC/PS)/SEBS blends
Authors: Schwarz M. C. , Keskkula H. , Barlow J. W. , Paul D. R.
Published: April 2003

Immiscible blends of high density polyethylene (HDPE) and an amorphous glassy phase consisting of either pure polystyrene (PS) or a miscible blend of PS and a polyether copolymer (PEC) were compatibilized with various amounts of a styrene‐hydrogenated butadiene block copolymer (SEBS). PEC is structurally similar to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). Using a liquid displacement stress dilatometer, the volume change of samples during uniaxial mechanical straining was determined and related to the various modes of deformation. Blends were fabricated by both injection and compression molding. Miscible PEC and PS blends were found to undergo a craze to shear yielding transition between 40 and 60% PS, which occurred at higher PS concentrations as SEBS was added. Blends with a HDPE matrix and a dispersed glassy phase showed reduced volume dilatation on adding SEBS, indicating better interfacial adhesion between the incompatible blend components. Increases in the sample volume were substantially less in blends with a PEC/PS glassy phase instead of pure PS, suggesting more effective compatibilization by the SEBS copolymer in blends with PEC. This trend is presumed to stem from an exothermic heat of mixing between the PS endblocks of SEBS and the PEC‐rich phases in the blend. Microscopic evidence of the improved adhesion and modes of deformation agrees with the results obtained by dilatometry. The volume dilatation of compression‐molded materials do not seem to be similarly affected by the composition of the glassy phase which may reflect morphological differences between injection‐and compression‐molded blends.
Polypropylene composites. I. Studies of the effect of grafting of acrylic acid and silane coupling agent on the performance of polypropylene mica composites
Authors: Chiang Wen‐Yen , Yang Wen‐Der
Published: April 2003

To improve adhesion between polypropylene (PP) and mica in PP composites, acrylic acid (AA) is graft‐copolymerized onto PP by a melt‐mixing method. At the same time, applying a silane coupling agent to treat the surface of inorganic filler enhances the mechanical, thermal, and electrical properties, as well as decreases mold shrinkage and color difference of the composites.
Studies on the cure characteristics and vulcanizate properties of 50/50 NR/SBR blend
Authors: Joseph Rani , George K. E. , Francis D. Joseph
Published: April 2003

Blends of 50/50 natural rubber (NR) and styrene‐butadiene rubber (SBR) are vulcanized using several conventional and semi‐EV systems. The cure characteristics and vulcanizate properties are compared. The quantity and quality of crosslinks in each case are deciphered by chemical probes to correlated them with the vulcanizate properties.
Toughening bismaleimide resins by reactive liquid rubbers
Authors: Takeda Shinji , Kakiuchi Hiroshi
Published: April 2003

The modification of bismaleimide resins with carboxyl‐terminated butadiene–acrylonitrile rubbers (CTBN) was studied. The effects of the rubbers on mechanical and thermal properties such as flexural strength, tensile strength, fracture toughness, glass transition temperature, and decomposition temperature of the rubber‐modified bismaleimide resins are discussed. The morphology of these resins were investigated by means of scanning electron microscopy and dynamic mechanical analysis. Addition of the rubbers improved the toughness of the bismaleimide resins without significant reductions in heat resistance of the resins.
Thermal behavior of cast polyurethane elastomers
Authors: Pandya M. V. , Deshpande D. D. , Hundiwale D. G.
Published: April 2003

Thermal properties like glass transition temperature (Tg), initial decomposition temperature (idt), integral procedural decomposition temperature (ipdt), and temperature at various % weight loss of a number of polyurethane systems are reported in this paper. Glass transition temperature was determined on TMA, and other thermal properties were determined by thermogravimetry. The experiments were designed to understand various factors such as length of chain extender moiety, flexibility of chain extender units by substitution of ether link in the diol chain, nature of bonds (unsaturation) in the extender unit, and nature of diisocyanates.
Grafting of vinyl acetate onto poly(vinyl chloride) in solution
Authors: Vigo Fernando , Uliana Claudio
Published: April 2003

Radiation‐induced grafting of vinyl acetate (VAc) onto poly(vinyl chloride) (PVC) was performed in solution with dimethylformamide (DMF). Grafting was studied as a function of dose, dose rate, and VAc/PVC ratio. The amount of grafting was measured by IR spectroscopy on the graft copolymer fraction insoluble in hot methanol. The homopolymerization of VAc was also studied in the same conditions, in order to check the influence of the solvent on radiochemical reactions leading to graft copolymers. The results show that the grafting can be easily obtained and the graft copolymer will be tested for the preparation of ultrafiltration membranes.
Effect of impurities on emulsion polymerization: Case I kinetics
Authors: Penlidis A. , MacGregor J. F. , Hamielec A. E.
Published: April 2003

The effect of water‐ and monomer‐soluble impurities on the kinetics of emulsion polymerization for Case I systems (e.g., vinyl acetate and vinyl choride) was investigated. Model predictions on the effect of these impurities on polymer particle nucleation and growth rate are shown to be in satisfactory agreement with experimental results. The effect of monomer‐soluble impurities is shown to be quite different from that observed in Case II emulsion polymerization systems.
Bonding of untreated cellulose fibers to natural rubber
Authors: Flink Per , Westerlind Bo , Rigdahl Mikael , Stenberg Bengt
Published: April 2003

Sulfur‐ and peroxide‐cured natural rubbers (NR) reinforced with short fibers of cellulose and carbon black have been studied with respect to water absorption, crosslink density, tensile strength, and the dependence of the dynamic storage modulus on strain amplitude. The results indicate that there is bonding between fiber and matrix even in the absence of a specific bonding system.
Studies of temperature and atmosphere composition influence on thermal degradation products of polyurethane foam
Authors: Włodarczak Daniela
Published: April 2003

The paper presents studies on the influence of temperature and atmosphere composition on the thermal degradation products evolved from flexible polyurethane foam. The experiments have been carried on within the temperature range 200–700°C in air atmosphere and oxygen–nitrogen–helium mixtures. The main volatile toxic products and weight losses during thermal degradation of the polyurethane foam have been determined. The test results have been presented graphically.
Surface energy of untreated and surface‐modified cellulose fibers
Authors: Westerlind Bo S. , Berg John C.
Published: April 2003

Average advancing and receding contact angles made against cotton and glass fibers by a set of probe liquids are determined using the Wilhelmy technique. The dispersive and polar components of the surface energy are calculated from the measured contact angles using both the geometric and the harmonic mean methods. It is found that these components are similar for untreated cellulose and glass fibers, and that they both have a high polar component, corresponding to a hydrophilic surface. Changes in surface energy caused by treatment of the cellulose fiber surfaces with melamine, polyethyleneimine (PEI), and a silane coupling agent are reported. It is found in particular that polyethyleneimine treatment of cellulose significantly reduces the polar component of its surface energy. While treatment of glass fibers with a silane coupling agent reduces the polar component and increases the dispersive component of the surface energy it shows little effect on the surface energy of cellulose.
Effect of inorganic salt on adsorption of sodium alkyl sulfates and fatty acid sodium salts from aqueous solution onto ion exchange resins
Authors: Ihara Yasuji
Published: April 2003

The adsorption isotherms of sodium salts of alkyl sulfonic acid and fatty acid with various carbon numbers onto ion exchange resins were measured in the absence and in the presence of sodium chloride in aqueous solutions. In the absence of the inorganic salt, the amount of adsorption remarkably increased with an increase in the length of alkyl groups in the adsorbates. Furthermore, the amount of adsorption apparently decreased with addition of sodium chloride into the solutions and almost reached a constant value at high concentrations of NaCl. This behavior strongly suggested that the electrostatic interaction on the adsorption decreased with increasing salt concentration and that the effect of hydrophobic interaction seems to play an important role on adsorption.
Kinetics of reaction of ethylenediamine and dimeric fatty acids
Authors: Kale Vijay , Vedanayagam H. Sumathi , Devi K. Sita , Rao S. Venkob , Lakshminarayana G. , Rao M. Bhagwant
Published: April 2003

Kinetic studies were carried out on the reaction between ethylenediamine and dimeric fatty acids in melt phase. The reaction was performed at 124, 130, 145, 160, 174, and 190°C and followed by determining the acid value of the product. The polyamidation reaction was found to be of overall second order with an activation energy of 18.2 kcal/g mol up to 90% conversion and of overall third order with an activation energy of 16.4 kcal/g mol above 90% conversion.
Studies on irradiation of agar–agar in the solid state: On the changes of water holding capacity of agar–agar hydrogel produced by irradiation
Authors: Nisizawa Mizuho
Published: April 2003

Solid agar–agar was irradiated with 60Co gamma‐rays, and effects of radiation on the water‐holding capacity of agar–agar molecules were studied by measuring the water content of the agar–agar hydrogel. The effects of postirradiation were also studied. Empirical equations of changes of water holding capacity were obtained.
A model for service life of polyethylene pipe exhibiting ductile–brittle transition in failure mode
Authors: Derringer George C.
Published: April 2003

This article proposes a model for predicting failure time of stressed polyethylene pipe materials that exhibit a failure mode transition from brittle to ductile as stress is increased. The model is based on data obtained using the constant tensile load (CTL) test and takes into account stress‐versus‐failure‐time behavior in both brittle and ductile regimes, as well as in the transition regime. The model permits quantification of the ductile–brittle transition behavior not only from the standpoint of the location of the transition but also its breadth. It is illustrated that knowledge of these two separate parameters opens new avenues for understanding the molecular basis of the transition process. This research was conducted under the sponsorship of the Gas Research Institute.
Mixing characteristics of urethane based materials and polyurea in RIM
Authors: Nelson M. , Lee L. James
Published: April 2003

To facilitate the study of new reaction injection molding (RIM) materials on a practical scale, a lab‐scale mini‐RIM machine was constructed. This machine is capable of delivering up to approximately 250 cc of material at rates of up to 125 cc/s. The RIM machine was first tested with conventional materials such as crosslinked and linear polyurethanes. The effect of varying the nozzle Reynolds number upon the adiabatic temperature rise corresponded to the results reported in previous works. Following this verification, two developmental materials, a polyurethane/polyester interpenetrating polymer network and a polyurea, were examined. The polyurea material showed a very strong dependency on mixing up to a Reynolds number above 400. The 75/25 PU/PEster reaction exotherms also showed a dependency upon mixing. However, this dependency is noticeable only in the polyester portion of the reaction, which can be attributed to the mixing sensitivity of the redox‐type initiators used.
Application and development of synthetic polymer membranes. II. Separation of aqueous ethanol solution through poly(tert‐butyl methacrylate‐co‐styrene) membranes
Authors: Yoshikawa Masakazu , Ohsawa Tomoki , Tanigaki Masataka , Eguchi Wataru
Published: April 2003

Separation of aqueous ethanol solution was carried out by pervaporation using a membrane which consisted of common polymer membranes. A membrane obtained from poly(tert‐butyl methacrylate‐co‐styrene) was effective for a selective separation of ethanol from aqueous ethanol solution by pervaporation technique. The pervaporation ethanol–water mixture through the present membranes was analyzed as a solution–diffusion process, on the assumption that the both diffusion coefficients of each component are an exponential function of ethanol concentration.