bluuebunny/crossref_metadata_2025_split huggingface dataset:
In situ determination of calcium carboxymethylcellulose on a cellulose film via ion exchange
Authors: Chen H. H. 
Published: April 2003

AbstractA simple and rapid ion exchange method is presented for the in situ determination of calcium carboxymethylcellulose (CaCMC) on a cellulose film. The method is based on the ion‐exchange reaction between the calcium ion in CMC and a large quaternary ammonium ion, such as hexadecyltrimethylammonium ion, followed by a second ion exchange reaction in which the quaternary ammonium ion is displaced by 3,9‐bisdimethylaminophenazothionium ion. The development of a blue color allows for the determination of the CaCMC distribution on the film by using a scanning densitometer. The reasons that CMC prefers a relatively large quaternary ammonium ion to the divalent calcium ion are suggested. This method is also applicable for the determination of sodium carboxymethylcellulose film where it is only necessary to carry out the second ion‐exchange reaction. The minimum detection limit for a CaCMC (degree of substitution is 0.7) coating is at least 1 μg/cm2.
Compatibility of epoxidized natural rubber with thermoplastic and thermosetting resins
Authors: Kallitsis John K. , Kalfoglou Nikos K. 
Published: April 2003

AbstractThe compatibility behavior of epoxidized natural rubber (ENR) at two different degrees of epoxidation with hydroxyl‐containing polymeric resins was investigated. These included Novolac and Resole resins, the cured epoxy of bisphenol A (CER), and phenoxy. For each system, compositions covering the complete range were studied using the dynamic mechanical (DMA), DSC and phase‐contrast microscopy techniques. ENR/Novolac blends were compatible, ENR/Resole, and ENR/phenoxy semicompatible, and ENR/CER incompatible. The results were interpreted in terms of the acid character of the aromatic or aliphatic hydroxyl contained in the resin and a predictive compatibility scheme based on copolymer‐copolymer miscibility theory was tested.
Optimal compositions of molded phenolic resins and its properties
Authors: Chiang Wen‐Yen , Yang Sung‐Yeng 
Published: April 2003

AbstractPhenolic resins [commercial (CP), pure (PP), and woodflour‐filled (WP)] containing different levels of hexamine, were evaluated in terms of curing behavior as well as thermal, electrical, and mechanical properties. The degree and rate of curing increase markedly with the rise of the hexamine content; however, the dielectric constant, dielectric loss, and dissipation factor decrease gradually. Dielectrical values decrease with the increase of the applied frequency. When the ratios of hexamine to phenolics are increased, samples become harder and experience increased molding shrinkage. With the increase of molding time or temperature, the surface hardness and molding shrinkage improve. The optimal hexamine contents of WP and PP are determined with respect to the above properties.
Quality assessment of polyester chips and yarn by TMS‐2
Authors: Joshi K. A. , Naik G. A. , Nevrekar N. B. 
Published: April 2003

AbstractPenetration in polyester chips of different manufacturers and yarn (undrawn and drawn) was studied between 323 and 423 K on a thermomechanical system (TMS‐2) using a penetration kit. It was observed that the penetration of the probe varied in the case of chips from manufacturer to manufacturer. The undrawn and drawn yarns from different batches and also within the same batch showed a clear variation in penetration curve, which may be attributed to the degree of crystallization. The same technique can be utilized for an assessment of the quality of yarn in continuous production and for differentiating the manufacturing process of polyester chips.
ESCA and other morphological investigations of the brittle failure caused by an environmental stress cracking (ESC) of a HDPE milk crate
Authors: Kulshreshtha A. K. , Kaushik V. K. , Pandey G. C. , Chakrapani S. , Sharma Y. N. 
Published: April 2003

AbstractThe causes of a drastic reduction in the service life of a HDPE milk crate have been investigated. The mechanism and the type of crate failure have been deduced from a detailed morphological examination of its fracture surface as well as the interior. Various factors responsible for a rapid failure of the milk crate have been identified. An ESCA study of ESC of weathered milk crate surfaces revealed the presence of heavy oxidative degradation on the surface and a diffusion‐controlled oxidation mechanism being operative in successive inner layers. The brittleness of this surface layer and formation of sharp cracks therein have been exhibited in SEM micrographs. Optical micrographs clearly show the presence of a surface layer, formed due to degradation, which is nonspherulitic and thus identifiable from the bulk, which is imperfectly spherulitic. Evidence for a migration of polymer additives from bulk to the surface is provided by the ESCA data and the SEM micrographs. DSC thermogram of the microtomed surface layer reveals bimodal endothermic peaks attributed to two phases present in the surface layer—one original phase and the second being degradation‐induced. The formation of this brittle surface layer and its effect on the long‐term fracture performance of milk crates are discussed, and suggestions for improving their durability are given.
Analysis of radiation chemical yields of chlorinated polystyrene derivatives
Authors: Hartney Mark A. 
Published: April 2003

AbstractA technique for determining radiation chemical yields from lithographic exposure curves for crosslinking type negative electron beam resists has been extended to include polymers with a general Poisson distribution. The technique is applied to several different chlorine‐containing styrene‐based resists. The radiation yields show good agreement with the differences in lithographic sensitivity and are explained by recent mechanistic studies. Optimal synthetic approaches for preparing this type of resist are described.
Steady‐state and transient behavior of a continuous polyethylene terephthalate condensation polymerization process. I. Melt transesterification stage
Authors: Khan A. A. , Choi K. Y. 
Published: April 2003

AbstractThe steady‐state and transient behavior of a continuous stirred‐tank reactor for melt transesterification of dimethyl terephthalate with ethylene glycol in the presence of metal acetate catalyst is presented. The kinetic model includes the main transesterification reactions and side reactions leading to diethylene glycol and carboxylic acid end groups. The effect of various reactro operating parameters such as [EG]/[DMT] mole ratio and feed catalyst concentration on the product distribution under steady‐state reactor operating conditions is analyzed. The dynamic process model has also been solved and the reactor transients to step changes in various reactor parameters are reported.
Interpenetrating polymer network from castor oil‐based polyurethanes and poly(methyl acrylate). XIV
Authors: Patel Prashant , Suthar Bhikhu 
Published: April 2003

AbstractCastor oil containing hydroxyl functionality was reacted with 4,4′‐diphenylmethanediisocyanate under different stoichiometric ratios of NCO/OH to obtain liquid polyurethanes. These polyurethanes were subsequently interpenetrated with methyl acrylate monomer using ethylene glycol dimethacrylate as a crosslinker by radical polymerization using benzoyl peroxide as an activator. The polyurethane/poly(methyl acrylate) interpenetrating polymer networks (PU/PMA IPNs) were obtained as tough films by transfer molding techniques. All IPNs were characterized by their resistance to chemical reagents, optical properties, thermal behavior, and mechanical properties: tensile strength, Young's modulus, elongation at break (%) and hardness Shore A. The morphology of the IPNs was studied by scanning electron microscopy and dielectric properties: electrical conductivity (σ), dielectric constant (ϵ′), dielectric loss (ϵ″), and loss tangent (tan δ) at different temperatures.
A comparison of the determination of macromolecular orientation in polypropylene by attenuated total‐reflection fourier‐transform infrared spectroscopy and X‐ray diffraction
Authors: Mirabella Francis M. , Shankernarayanan M. J. , Fernando Priya L. 
Published: April 2003

AbstractAttenuated total reflection‐infrared (ATR‐IR) spectroscopy and wide‐angle x‐ray diffraction (WAXD) were used to determine the macromolecular orientation of a series of six uniaxially oriented polypropylene sheets with elongations of 0% to 500%. The orientation functions were expressed as fractions of chains oriented along the machine, trasverse, and normal directions in the sheets. Good agreement was found between the orientation functions for the two techniques. Sources of potential difference between the two techniques were discussed. The ATR‐IR technique is surface sensitive to a depth of about 5 or 10 μm into the surface while the WAXD technique is bulk sensitive. The ATR‐IR technique is sensitive to both the crystalline and noncrystalline material while the XRD technique is sensitive only to the crystalline material.
Epoxy–lignin polyblends. III. Thermal properties and infrared analysis
Authors: Feldman Dorel , Banu Dorina , Khoury Marwan 
Published: April 2003

AbstractDifferential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and IR analysis were performed on a nonviscous epoxy polymer system (EP) with Kraft lignin (L) up to 20%. Mixtures of EP with similar amounts of silica (S) as in EP–L polyblends were used as a reference system for the analyses performed. EP–L polyblends cured at room temperature exhibit a single Tg, a fact characteristic for the monophasic systems. One‐step tensile storage modulus vs. temperature curves, and related one‐peak tensile loss modulus vs. temperature curves were found for all the EP–L polyblends. At about 30°C the tensile storage modulus of EP does not change in the presence of lignin in amounts up to 20% by weight. All these showed that L is miscible with EP and it does not affect the crosslinking at room temperature. IR spectra led to similar conclusions. The gradual decrease of the peak values of tan δ with the amount of L in polyblends is due to an increase in the tensile storage modulus and a decrease of the tensile loss modulus at temperatures close to Tg. This fact is explained by a stronger bond between EP and L, which could be formed at higher temperatures. The DSC and DMA data are in agreement with the mechanical properties of EP–L polyblends, which were reported previously.
Accumulation and desorption of free radicals in emulsion copolymerization
Authors: Hagiopol Cornel , Deleanu Theodor , Memetea Tatiana 
Published: April 2003

AbstractThe emulsion copolymerization of styrene with acrylonitrile, seeded on a polybutadiene support and initiated either potassium persulfate or γ‐rays has been studied. The original technique of support activation consists of two steps: the start of the copolymerization in the presence of a small fraction of monomers, followed by the addition of the rest of monomers, which leads to a great increase in the reaction rate. The experimental data provide evidence for a new mechanism that takes into account the desorption–reentry of the free oligoradicals into another particle, their transfer to the polybutadiene support, which results in the accumulation of trapped free radicals. As a consequence of free radicals' accumulation, the overall copolymerization rate increases. The accumulation as well as the desorption processes place this type of copolymerization far from Smith–Ewart theory case II.
Kinetics of vinylchoride removal from polyvinylchloride by thermal treatment in a flow of inert gas
Authors: Peev G. , Trifonova M. , Peeva L. 
Published: April 2003

AbstractThe kintetics of free monomer removal from powdered suspension polyvinylchloride at elevated temperatures in a nitrogen flow is studied. It is found that in fluidized bed the monomer concentration decreases linearly with time. This behavior cannot be explained by a model of molecular diffusion in single spheres because of particle degradation during the treatment. Conditions for complete vinylchloride removal from the polymer are proposed.
Die geometrical effect on annular die swelling
Authors: Seo Yongsok , Wissler Eugene H. 
Published: April 2003

AbstractDie geometrical effect on Newtonian annular jet swelling was studied using a finite element method. Numerical result shows what we expected in the limiting cases of die swelling with annular die geometries, i.e., variation of the die gap for straight dies follows the limiting behavior of capillary and planar die swellings. Also the effect of upstream die geometry was investigated. The result shows that final extrudate dimensions are generally influenced by its previous history in the die, i.e., not only by shearing action but also by elongational effect caused by narrowing die gap.
The effect of corona discharge treatment of ethylene copolymers on their adhesion to aluminum
Authors: Hjertberg T. , Sultan B.‐Å , Sörvik E. M. 
Published: April 2003

AbstractThe efficiency of different techniques of obtain improved adhesion in polyethylene‐aluminum laminates have been studied. Both surface treatments, such as thermal oxidation and corona discharge, and the use of copolymers with polar comonomers, i.e., vinyl acetate (EVA) and butyl acrylate (EBA), have been included. Thermal oxidation performed by high temperature extrusion including an ozone shower seems to be more effective than corona discharge. In a model experiment thermal oxidation was studied in more detail. The adhesion, as measured by a T‐peel test, increased with the content of carbonyl measured by reflexion IR, except for relatively long thermal treatments. In the latter case molecular scission gave a large fraction of low molecular weight material with low cohesive strength. For EBA and EVA the peel strength increased linearly with the bulk concentration of comonomer from about 100 N/m for untreated polyethylene to 450 and 300 N/m, respectively, at 5 mol % comonomer. Corona discharge treatment of these copolymers had, however, a most remarkable effect on the adhesion properties. The increases, relative to untreated EBA and EVA, were much more dramatic compared to polyethylene, e.g., three to four and less than two times, respectively. The higher values obtained with EBA are suggested to be due to the conversion of acrylate groups into carboxylic acid. In the case of EVA, loss of acetic acid might instead decrease the content of polar groups.
Reinforcement of EPDM matrices with carbon and polyester fibers—mechanical and dynamic properties
Authors: Ibarra L. , Chamorro C. 
Published: April 2003

AbstractThis paper reports on the study of the mechanical and dynamic properties of composites with an EPDM matrix and short fiber, either polyester or carbon, at three different fiber concentrations. In general, the properties prove to be dependent on fiber concentrations and type, in particular on the final ratio fiber length/diameter. This ratio ranges for carbon fiber over 35–45 and for polyester over 135–175, thus placing the former near the lower limit of acceptability. Evidence is supplied of the existence of adhesion between the matrix and the fiber, in the form of measurements of the swelling and dynamic properties, especially through variation of relative damping and the displacement of the dynamic glass transition temperature towards higher ranges. Composites present a marked property anisotropy.
Influence of solvent penetration on the electrical conductance of pre‐extended FEF carbon black‐loaded rubbers
Authors: Amin M. , Nasr G. M. , Khairy S. A. , Ateia E. 
Published: April 2003

AbstractThe penetration of organic solvent and its influence on the electrical conductance of pre‐extended styrene butadiene (SBR), butadiene (BR), acrylonitrile butadiene (NBR), butyl (IIR), and natural (NR) rubbers are investigated. A model is proposed for a process by which it is possible to estimate the separation distance between carbon black particles (or aggregates) and its dependence on the extent of penetration of the liquid. An empirical formula is suggested to describe the variation of the conductance of rubber composites with swelling time in terms of the interspacing distance.
Reaction rate and MWD changes in crosslinking of PVC, with dithioltriazine
Authors: Hjertberg Thomas , Dahl Roger , Sörvik Erling 
Published: April 2003

AbstractThe reaction rate of crosslinking of PVC with dithioltriazine has been studied by following gel formation and changes in the molecular weight distribution (MWD). Compounding was performed on a roll mill at 145°C and crosslinking by heat treatment at 180 or 90°C. In this system crosslinking is executed by the thiolate anion, formed in situ by reaction with MgO. We have studied the catalyzing effect of several polyols in order to achieve a more efficient reaction. Most likely, these catalysts work by chelating the Mg2+ ions, thus increasing the nucleophilic character of the thiolate. With the most efficient ones, ditrimethylolpropane and HO(CH2CH2)6‐7H, complete crosslinking can be obtained in 3 min at 180°C, i.e., at processing temperatures. We also followed the changes in the MWD before gelation at a considerably lower temperature, 145°C, and found an extensive molecular enlargement even after 5‐10 min. Most surprisingly, μMn increased up to 100% without formation of insoluble material. By 1H‐NMR measurements on low molecular weight extracts, we have shown this to be due to a fast and selective reaction with allylic chlorine in the unsaturated end groups, ∼ CH2CHCHCH2Cl, formed in the mechanism of chain transfer to monomer. Due to this reaction, formulations with too high reactivity may crosslink during processing, which calls for a careful balancing of the reactivity for each processing case.
Studies on polypyromellitimides containing phosphorus
Authors: Varma Indra K. , Saxena Sneh , Varma D. S. 
Published: April 2003

AbstractThe paper describes the synthesis of several polypyromellitimide samples containing phosphine oxide in the backbone and maleimido groups as pendant side chains. These polymers were obtained by solution polycondensation reaction in DMF in three steps. First step involved the reaction of equimolar amounts of maleic anhydride (MA) and tris(3‐aminophenyl) phosphine oxide (TAP) in DMF at 60°C for 2 h. Low temperature polycondensation was carried out at 0–5°C by the addition of 4,4'‐diaminodiphenyl ether (DADPE) and pyromellitic dianhydride. Cyclodehydration of poly(amide acid) thus obtained was done by chemical means. Various copolymers thus obtained were characterized by intrinsic viscosity measurements, elemental analysis, and IR spectroscopy. Thermal behavior and curing characteristics of copolyimides were evaluated by thermogravimetry and differential scanning calorimetric studies. An increase in the char yield at 800°C was observed on increasing phosphine oxide content of polyimides.
Invariant kinetic parameters of polymer thermolysis. II. Butyl rubber pyrolysis
Authors: Levchik S. V. , Levchik G. F. , Lesnikovich A. I. 
Published: April 2003

AbstractThe methodological problem of correct estimation of invariant Arrhenius parameters Ǎ and Ě from nonisothermal experiments has been analyzed for thermal decomposition of commercial butyl rubber in inert atmosphere. It is shown that restriction of the kinetic analysis by varying n in the function f(α) = (1 − α)n may yield incorrect Ǎ and Ě. It is necessary to apply the set of f(α) known in the formal topochemical reactions kinetics for correct estimation of Ǎ and Ě.
Influence of steric length in electrosteric surfactants on emulsion polymerization
Authors: Dittman‐McBain Carla B. , Piirma Irja 
Published: April 2003

AbstractFour PPG Avanel Series S surfactants (sodium alkyl polyether sulfonates) with varying ethylene oxide content (n = 3, 7, 9, and 15) were used to investigate the influence of the steric length in this type of electrosteric stabilizers on emulsion polymerization. The polymerization studies employing potassium persulfate as an initiator with styrene, methyl methacrylate, and vinyl acetate monomers showed no apparent change in particle size, number of particles, and polymerization rate with the changing steric length of the surfactant. Steric influences were observed in the redox‐initiated systems of styrene, butyl acrylate, and methyl methacrylate. Increasing the ethylene oxide unit content from three to nine units decreased the rate of polymerization, the particle size and number in the polystyrene latexes. Polymerizations with the acrylates displayed the same trend except that the polymerization rate reached a minimum value at nine ethylene oxide units and increased when the surfactant containing 15 ethylene oxide units was used.
Plasma‐modified Nylon 4 membrane for dialysis
Authors: Lai J. Y. , Chou C. C. 
Published: April 2003

AbstractThe effects of plasma treatment conditions, such as supply power, treatment time, gases used in reactor, surface energy, water content, dialysis permeability, partition coefficient, diffusion coefficient, and free volume of Nylon 4 membranes, were studied. The solutes considered for dialysis system were NaCl, urea, and MgCl2. The permeabilities of NaCl and urea of membranes with plasma treated in argon at 80 W for 20 min are 5.57 × 10−5 and 5.89 × 10−5 cm2/min, respectively. Much higher permeabilities of NaCl and urea obtained by oxygen plasma‐treated membranes under 20 W and for 20 min are 30.74 × 10−5 and 17.66 10−5 cm2/min, respectively, compared to that of untreated Nylon 4 membranes.
Stress evolution analysis in postforming cooling
Authors: Cohen A. , Dibbs M. G. 
Published: April 2003

AbstractAn interaction between heat transfer, shrinkage, and stress relaxation during postforming cooling of thermoplastic materials was studied. In order to arrive at a treatable mathematical formulation, while retaining the basic physical effects, the one‐dimensional case was analyzed with the relaxation spectrum approximated by a single relaxation time depending on temperature. An effective relaxation parameter β controlling the postforming behavior was identified. Its dependence upon the relaxation time, rate of heat transfer, and a temperature interval was established. An analytical approximation for a maximal tensile stress was developed. This result enables an understanding of the interaction between cooling conditions and material behavior.
Synthesis, characterization, and kinetic study on the thermal decomposition of polyamidoethers
Authors: Ahmed I. K. , Rashid M. A. M. , Kafaf B. T. 
Published: April 2003

AbstractSome new polyamidoethers have been synthesized by condensation reaction of N,N'‐dichloroacetyl‐1,4‐phenylene‐diamine with bisphenols (4,4'‐isopropylidenediphenol, 4,4'‐dihydroxydiphenyl sulfone, 4,4'‐dihydroxydiphenyl sulfide, and 4,4'‐dihydroxybiphenyl) in N‐methylpyrrolidone medium using DB‐24‐Crown‐8 as a phase‐transfer catalyst. The structure of these polymers has been characterized by infrared (i.r.) and 1H nuclear magnetic resonance (NMR) spectroscopy. Kinetic method of thermal decomposition of these polymers and their 2% mixture with polyvinylchloride (PVC) has been studied.
Mechanism of poly(methyl methacrylate) fire retardation by Wilkinson's salt
Authors: Sirdesai Sunil J. , Wilkie Charles A. 
Published: April 2003

AbstractThe reaction of Wilkinson's salt, CIRh(PP3)3, and poly(methyl methacrylate) (PMMA) has been studied. Char formation is observed, and some 30% of the reaction product is nonvolatile at 600°C. In order to understand the pathway of this reaction, the reaction of dimethylglutarate (DMG) and CIRh(PP3)3 has been studied. A pathway is proposed in which the initial step is the oxidative addition of the rhodium species into a carbon—oxygen bond of the DMG molecule. Six different products have been isolated from this reaction and can be seen to result from the oxidative insertion. This pathway also seems to apply to the PMMA reaction and leads to an interpretation of the results of this reaction and permits one to understand the role of this, and similar, compounds as flame retardants.