bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermodynamic and structural properties of acrylonitrile–butadiene rubber/polyethylene blends
Authors: Frenkel R. , Ducháček V. , Kirillova T. , Kuzmin E.
Published: April 2003

Thermodynamics of interaction, adhesive properties, and the structure of acrylonitrile‐butadine rubber/low density polyethylene blends have been investigated. Enthalpy and entropy components of interaction parameters supporting an incompatibility of studied systems and a possibility of highly organized structure formation on the phase interface were determined by inversion gas chromatography. The formation of highly organized structures on the interface is made possible by a local diffusion of polybutadiene fragments into polyethylene phase. That is why acrylonitrile microblocks are oriented. By this manner adhesion between rubber and polyethylene phase is enforced and simultaneously a number of morphological changes take place.
Anomalies in the rheological behavior of polyethylene with very broad molecular weight distribution
Authors: Masson Patrick , Spitz Roger
Published: April 2003

The rheological behavior of high density polyethylenes with very broad molecular weight distribution is studied in the molten state starting from freshly synthesized powders. The complex viscosity increases slowly up to a limiting value as a function of ageing of the polymer and faster when the molten polymer is stirred. The phenomena are explained by an heterogeneous distribution of very high molecular weight nodules in the polymer arising from the synthesis and is proved by the preparation and characterization of polymers presenting the opposite heterogeneity and behavior (very low molecular weight nodules).
Hydrolysis and condensation mechanisms of a silane coupling agent studied by 13C and 29Si NMR
Authors: Nishiyama Norihiro , Horie Kozo , Asakura Tetsuo
Published: April 2003

The mechanisms of hydrolysis and condensation of a silane coupling agent, γ‐methacrylo‐xypropyltrimetoxysilane (γ‐MPTS) were investigated by the use of both 13C and 29Si nuclear magnetic resonance (NMR) spectroscopies. The NMR peaks of the hydrolyzed monomer and condensed polymer were assigned readily. The rate of hydrolysis and condensation of γ‐MPTS was dependent on water content. On the basis of the time‐dependent behavior of these peaks, the mechanisms of hydrolysis and condensation were clear.
A fourier analysis dynamic birefringence apparatus
Authors: Kumar Satish , Stein R. S.
Published: April 2003

Molecular motion in a polymeric system can be studied using dynamic birefringence. Computer interfacing of the dynamic birefringence apparatus and the data treatment using Fourier analysis are reported in this paper. Experiments are done under sinusoidal strain; stress, strain and birefringence signals are monitored. Birefringence is measured using the optical transmission technique. An AIM‐65 microcomputer was interfaced with this apparatus for the purposes of data acquisition and data analysis. First‐order Fourier coefficients are used to determine the real and imaginary components of the modulus, the strain optical coefficient, and the stress optical coefficient. Higher order Fourier coefficients can be used to study the nonlinear viscoelastic behavior in the polymer.
Correlation of mechanical property, crosslink density and thermogravimetric behavior of castor oil polyurethane–polystyrene divinyl benzene simultaneous IPN networks
Authors: Kumar V. G. , Rao M. Rama , Guruprasad T. R. , Rao K. V. C.
Published: April 2003

Several simultaneous interpenetrating networks (IPN) of castor oil polyurethane (COPUN) and polystyrene divinyl benzene (PSN) were synthesized under conditions where the free radical polymerization of styrene and the crosslinking reaction of castor oil and toluene diisocyanate progress at comparable rates. Comparison of the mechanical properties and crosslink density of the COPUN and COPUN/PSN‐IPNs indicates a marginal increase in tensile strength and crosslink density from COPUN to 60COPUN/40 PSN IPN. IPN samples prepared with further increased PSN content show steady decrease in the above properties. This reversal of the expected trend was attributed to the possible greater molecular interpenetration achieved due to similar gelation times with resultant extension of chains and increase in free volume between crosslinks. This was further confirmed from thermogravimetric data on the initial stages of decomposition of the IPNs.
Studies on the temperature dependence of extinction oxygen index values for cellulosic fabrics. I. Cotton
Authors: Horrocks A. R. , Price D. , Tunc M.
Published: April 2003

The concept of extinguishability as a measure of textile flammability is reviewed. Definition and determination of extinction oxygen index enables a parameter to be defined from which the effects of ignition time and fabric structure may be removed. This so‐called extinction oxygen index (EOI) and the derived value at zero ignition time [EOI]0 more exactly define the burning/nonburning fabric boundary than does the more widely used limiting oxygen index (LOI). This first paper reports the determination of EOI and [EOI]0 values for a series of cotton fabrics in the temperature range 20–200°C. The influence of the various fabric parameters of area density, air permeability, sample thickness, bulk density, and moisture content was investigated. The advantages of using the EOI rather than the LOI concept as a measure of textile flammability is indicated in the discussion of the results of this study with reference to previous work concerned with LOI data for cotton. In particular, the significance that environmental temperature has on EOI and related parameters reported here and previously reported LOI data is discussed in terms of various published models which define the burning/extinction threshold.
Retarding and antioxidant activity of 1‐cyclohexylthio‐2‐mercaptobenzimidazole in the vulcanization of NR accelerated by thiocarbamyl sulfenamide
Authors: Das Prasanta Kumar , Datta Rabindra Nath , Basu Dipak Kumar
Published: April 2003

The effect of 1‐cyclohexylthio‐2‐mercaptobenzimidazole (CMB) on the vulcanization of NR accelerated by N‐oxydiethylene thiocarbamyl‐N′‐oxydiethylene sulfenamide (OTOS) has been studied. It is found that CMB delays the onset of cure and generates 2‐mercaptobenzimidazole during vulcanization. The results indicate the retarding as well as antioxidant activity of CMB.
Dynamic compression characteristics of flexible foams. I. Similarity model, analysis, and experiments
Authors: Yossifon S. , Szanto M.
Published: April 2003

A simple mathematical model is proposed, based on dimensional similarity parameters, to describe the characteristics of flexible plastic foams under impact conditions. The model assumes that the foam is rate‐dependent material, when the dynamic stress is a function of the strain and the strain rate. The similarity parameters include the geometric dimension of the foam, the mass of the absorbing body, and the drop height. By using this model, one can predict the maximum deformation, the maximum decelerations, and the time‐pulse period for a wide range of drop heights and masses, by conducting several drop tests. We verified the efficacy of this model by performing free‐fall drop tests with flexible polyurethane foam having a uniform density of 240 kg/m3.
Interpenetrating polymer networks from caster oil‐based‐polyurethanes and poly(ethyl acrylate). VII
Authors: Patel Mayur , Suthar Bhikhu
Published: April 2003

Liquid prepolyurethanes were synthesized from castor oil and toluene‐2, 4‐diisocyanate (TDI) under different experimental conditions and varying NCO/OH ratios. All these prepolyurethanes were subsequently reacted with ethyl acrylate/ethylene glycol dimethacrylate mixtures by radical polymerization using benzoyl peroxide as initiator to obtain interpenetrating polymer networks (IPNs) by transfer molding. The novel polyurethane/poly(ethyl acrylate) IPNs are found to be tough films. These IPNs are characterized in terms of their resistance to chemical reagents, thermal behavior (DSC, TGA), mechanical behavior including tensile strength, Young's modulus, and elongation. The dielectric properties, namely electrical conductivity (σ), dielectric constant (ε′), dielectric loss (ε″), and loss tangent (tan δ) were computed. The mechanothermal behavior was analyzed by dynamic mechanical spectroscopy. The morphological behavior was studied by scanning electron microscopy.
Poly(phenylene oxide) composites containing crosslinked polystyrene microspheres. II. Dark crosses observed in microscope
Authors: Zhikuan Chai , Qipeng Guo
Published: April 2003

Extinction phenomena observed between crossed polaroids in microscope were classified into three groups: (1) Poly(2, 6‐dimethyl‐1, 4‐phenylene oxide)/polystyrene composite with crosslinked polystyrene microspheres. Negative dark crosses were observed in the shells of the spheres, the cores of the spheres were completely extinct. The crosses disappeared at 170°C, which is 20°C above Tg of the matrix polymer. (2) Polycarbonate composite with glass beads. The dark crosses were positive and outside the glass beads. The crosses disappeared at 130°C, which is 20°C below Tg of the matrix polymer. (3) In situ polymerized composites with crosslinked polystyrene microspheres. The dark crosses were the same size of the spheres. They were negative in poly(methyl methacrylate) and poly(vinyl acetate) and positive in polystyrene. The disappearing temperatures of the crosses were 150, 110, and 285°C, respectively. The first two groups of phenomena are explained as the photoelastic effects caused by the thermally induced stresses. The last group is due to the inhomogeneous swelling or contracting of polystyrene networks in the matrices.
An analysis of the accuracy of determining molar‐mass averages of polymers by GPC with an on‐line light‐scattering detector
Authors: Procházka Ondřej , Kratochvíl Pavel
Published: April 2003

The effect of errors of concentration and molar‐mass detectors in GPC on the accuracy of determining molar‐mass averages Mn and Mw was analyzed. Model calculations show that by means of GPC with an on‐line low‐angle laser light‐scattering (LALLS) photometer only Mw can be determined with acceptable accuracy. Mn can be determined with acceptable accuracy only for polymers that have very small polydispersities. Mn can be determined with greater accuracy from data of a concentration detector and chromatographic‐column‐calibration data. The most suitable procedure for the determination of Mw seems to be a direct integration of the molar‐mass detector output, even if the error due to neglecting the second virial coefficient term is significant. Compared with the inaccuracy of detectors, axial dispersion appears not to be the main source of errors in GPC with an on‐line molar‐mass detector.
Copolymerization of vinyl chloride with 1‐olefins. III. An investigation of the copolymerization reaction of vinyl chloride with 1‐butene and 1‐pentene
Authors: Mrázek Z. , Jungwirt A. , Kolínský M.
Published: April 2003

Series of suspension copolymerization of vinyl chloride with various contents of 1‐butene and 1‐pentene (5–30 mass%) were carried out under the same reaction conditions. By applying a method which utilizes periodic sampling of heterogeneous reaction mixture from the reactor during the reaction and a gas chromatographic determination of unreacted vinyl chloride in the sample, the conversion curves of vinyl chloride were determined and the initial reaction rates were compared.
Separation and characterization of low‐conversion poly(styrene‐co‐methyl methacrylate) by liquid adsorption chromatography
Authors: Mori Sadao , Uno Yoshitaka
Published: April 2003

Poly(styrene‐co‐methyl methacrylate) copolymers of narrow chemical composition distributions were separated according to composition by linear gradient elution at column temperatures between 10 and 80°C using silica gel as an adsorbent. The initial mobile phase was a mixture of chloroform and ethanol (99.0 : 1.0, v/v) and the final one (95.5 : 4.5). The relationship of retention volume and the composition of the copolymers was obtained. Higher column temperature (and/or less ethanol content in the mobile phase) is preferable for the separation of copolymers having less MMA and vice versa. Molecular weight dependence on retention volume was not observed. The chromatographed copolymers were still chemical heterogeneous: the compositional difference of the front and rear halves of an adsorption chromatogram of a copolymer was 2.1 %. The front half had a higher styrene content and lower molecular weight averages than those for the rear half of the peak. This separation method was reproducible and the relative standard deviation was about 0.6%. Recovery of fractions was 98.2% by isocratic elution and 96.4% by gradient elution.
Synthesis of new flame‐retarding epoxy resin based on 3′, 5′, 3″, 5″‐tetrabromophenolphthalein
Authors: Yang Chin‐Ping , Lee Tzong‐Ming
Published: April 2003

New flame‐retarding epoxy is synthesized by reacting 3′, 5′, 3Prime;, 5″‐tetrabromophenolphthalein (TBPP) with epichlorohydrin and characterized in comparison with commercially available tetrabromobisphenol‐A(TBBA) epoxy on their flame retardancy and thermostability. TBPP epoxy show better results in promoting flame resistance than TBBA epoxy. However, TBPP epoxy exhibits a greater effect on thermal decomposition temperature. The order of char yield at 800°C under nitrogen for the cured products is TBPP epoxy > phenolphthalein (PP) epoxy > TBBA epoxy. Meanwhile, there is a linear relationship between oxygen index and char yield for cured products of TBPP‐PP epoxy and TBBA‐BA epoxy systems.
Thin polymer films from fluidized electrode bed reactors
Authors: Teng F. S. , Mahalingam R.
Published: April 2003

The formation and deposition of a polymer as a thin, uniform solid film on a metal particle substrate is investigated in detail in a fluidized electrode bed reactor. Experiments were carried out in different designs of fluidized bed electrode cell reactor, using various metal particles and monomers. It was observed that diacetone acrylamide (DAA) monomer in 0.1N H2SO4 with aluminum particles (3530 μm) as cathode, in a concentric dual compartment cell, appeared to yield the best films. Infrared and elemental analyses were used to characterize the polymer film on the metal particles. Scanning electron microscopy (SEM) was employed to examine the surface and cross‐sectional profiles of the films. The potential profiles in both particulate and solution phases were measured and the importance of particulate electrical conductivity in the polymerization is thus explained. It was observed that the optimum particulate conductivity and hence the maximum yield occurs in the range of 10–20% bed expansion. The experimental product yields for various liquid superficial velocities (i.e., bed expansion) at different feeder current densities were compared to explain the possible controlling mechanism in packed and fluidized bed cells, noting that both chemical reaction and mass transfer control in the low bed expansion region while chemical reaction controls in the high bed expansion region. The current effciency decreases in the high current region due to side reactions at the fluidized bed electrode and due to pore diffusion in the polymer film.
Sorption of methylene chloride in polyethylene terephthalate
Authors: Liu C.‐P. Anthony , Neogi P.
Published: April 2003

Sorption of methylene chloride in polyethylene terephthalate has been performed at three different temperatures: 21, 34, and 48°C. The solubility data are explained through dual sorption. The diffusivities are more difficult to explain since some anomalous effects were present.
Nylon 6,6 copolyamides of bis(2‐carboxyethyl) methylphosphine oxide
Authors: Ridgway James S.
Published: April 2003

Copolyamides of nylon 6,6 with bis(2‐carboxyethyl)methylphosphine oxide (CEMPO) were prepared by melt polycondensation of nylon 6,6 salt with CEMPO and hexamethylene diamine. The effect of CEMPO upon melting point, moisture regain, boiling water shrinkage, water wicking, tensile properties, thermal stability, static dissipation, and flammability of nylon 6,6 fibers and fabrics was determined. The fiber properties were greatly affected by the high water absorption and solubility characteristics of the phosphine oxide linkage. However, crystallinity and orientation were not greatly disturbed by up to 30–40M% CEMPO substitution in nylon 6,6. The copolyamides were of improved flame resistance compared to nylon 6,6 and were also found to give improved flame resistance in blends of the copolymer with various commercial plastics. In addition, CEMPO and the corresponding diamine, bis(3‐aminopropyl)methylphosphine oxide were used to prepare a series of cycloaliphatic and aromatic ring‐containing polyamides, but problems were encountered with moisture sensitivity and low melting points with some of these polymers.
Structures, properties, and alkali metal ion transport membrane of polyelectrolyte complexes consisting of methyl glycol chitosan, glycol chitosan, and poly(vinyl sulfate)
Authors: Kikuchi Yasuo , Kubota Naoji , Mitsuishi Hiroshi
Published: April 2003

Mixtures of methyl glycol chitosan and glycol chitosan were reacted with poly(vinyl sulfate) to form many different water‐insoluble polyelectrolyte complexes (PEC) in aqueous solution at various hydrogen ion concentrations. It was revealed from elemental analyses, infrared (IR) spectroscopy, and solubilities of PEC that molecular structures of each PEC are dependent on [H+]. PEC membranes were made from casting solutions of all kinds of PEC, and transport phenomena through the membrane of PEC prepared in a pH 13.0 solution were investigated under various conditions. The transport ratio of Na+ and the electric potential difference between the left‐ and right‐hand sides of the membrane were measured, and it is suggested that the driving force for active transport depends on the membrane potential, Donnan potential and diffusion potential. Moreover, permeability of K+ was higher than that of Na+ in selective transport.
Characterization of styrene–methyl methacrylate–n‐butyl acrylate terpolymers. II. Effects of sequence distribution on glass transition temperature
Authors: Kobayashi Minoru
Published: April 2003

The effects of sequence distribution on the glass transition temperature (Tg) of the title terpolymers prepared by radical polymerization were studied. Tg was examined by thermomechanical analysis. The average diad concentrations, as estimation of sequence distributions were calculated from monomer reactivity ratios. A modified Gibbs–Dimarzio equation for binary copolymers was extended to terpolymers to explain the relation between observed Tg and average diad concentrations. The observed Tg showed good agreement with the calculated values determined by the extended equation.
High activity mixed metal alkyl cocatalysts for α‐olefin polymerization
Authors: Bacskai R.
Published: April 2003

High activity α‐olefin polymerization catalysts are generally obtained by mixing MgCl2‐supported TiCl4 (MgCl2/TiCl4) with an aluminum trialkyl cocatalyst. Surprisingly, AlEt2Cl, which is the preferred cocatalyst in polymerizations employing nonsupported Ti compounds, is a poor cocatalyst when used with MgCl2/TiCl4. It was found that in propylene and 1‐butene polymerizations, using different MgCl2/TiCl4 catalysts, the cocatalyst activity of AlEt2Cl can be greatly improved by the addition of a magnesium or lithium alkyl. The mixed metal alkyl obtained from AlEt2Cl and MgBu2 is a particularly effective cocatalyst always yielding more polymer, of about the same stereospecificity, than the conventional aluminum trialkyls. The exact nature of the mixed metal alkyl cocatalysts is not known, but the available evidence argues against in situ aluminum trialkyl formation resulting from the alkylation of AlEt2Cl by the second metal alkyl.
Development of crystalline structure during tubular film blowing of low‐density polyethylene
Authors: Kwack Tae Hoon , Han Chang Dae , Vickers M. E.
Published: April 2003

Development of crystalline structure during the tubular film blowing of low‐density polyethylene was investigated, using wide‐angle X‐ray diffraction technique, low‐angle light scattering, and scanning electron microscopy. In the study, commercial grades of both high‐pressure low‐density polyethylene (HP‐LDPE) and low‐pressure low‐density polyethylene (LP‐LDPE) (also, commonly referred to as linear low‐density polyethylene, LLDPE) were used. The applied stresses at the freeze line were determined using theoretical expressions derived in an earlier publication [C. D. Han and T. H. Kwack, J. Appl. Polym. Sci., 28, 3399 (1983)]. The applied stresses, S11F and S33F, at and above the freeze line in the machine and transverse directions were expressed in terms of the tension at the take‐up device, take‐up ratio, blow‐up ratio, and the pressure difference across the film of the bubble. These applied stresses were used to interpret the crystalline axes' orientation in the tubular blown films. It was found that the magnitude of S11F is an important process parameter for the crystalline axes' orientation and that the biaxial stress ratio (S11F/S33F) appears to be a determining factor in the distribution of fibrillous nuclei and crystalline texture, as well as film anisotropy.
Photopolymerization of vinyl monomers using benzophenone‐tetrahydrofuran initiation system and aldehydes at low temperatures
Authors: Matsuzawa Shuji , Yamaura Kazuo , Yamada Sinichiroh , Shinke Yosihide , Nakano Yasumasa , Koike Yohtaroh
Published: April 2003

The photopolymerizations of vinyl trifluoroacetate (VTFAc), vinyl acetate (VAc), and methyl methacrylate (MMA) using the initiation system benzophenone–tetrahydrofuran were studied at low temperatures. At −78°C the rate of polymerization of VTFAc was higher than that of VAc, while MMA, which was solidified, did not polymerize. After melting the irradiated solid mixture the polymerization occurred at 4°C. The photoinduced polymerization of VTFAc occurred in the presence of butylaldehyde or isobutylaldehyde at −70°C. The degrees of polymerization and syndiotacticities of the polymers prepared were investigated.
On the structure of glassy polymers. VIII. Use of Z contrast to elucidate the microstructure of epoxy and polyimid resins
Authors: Di Filippo G. V. , Sande J. B. Vander , Uhlmann D. R.
Published: April 2003

The technique of ultramicrotomy of polymers, followed by staining of the resulting thin sections with heavy metal ions and viewing with Z enhancement in the scanning transmission electron microscope is described. When applied to anhydride‐cured epoxy resins, the structure is found to be heterogeneously crosslinked on a scale of a few hundred angströms. When the technique is applied to amine‐cured epoxy resins, the microstructure is found to change from homogeneous to inhomogeneously crosslinked, depending on stoichiometries and cure cycles. For amine‐cured resins whose cure conditions are within the range of microstructural change, the bright field of the stained specimens alone does not detect heterogeneities, and the Z contrast becomes crucial to discern the kind of microstructure. A commercial polyimide film examined in the same way is found to exhibit systematic variations in structure through the thickness of the film.
Thermovulcanization of polychloroprene rubber and its blends with poly(vinyl chloride)
Authors: Běhal Miroslav , Ducháček Vratislav
Published: April 2003

Heat and mechanical stressing at higher temperatures effect changes in polychloroprene rubber leading to network formation. During thermovulcanization of polychloroprene rubber in the temperature range of 150–200°C, two reactions have been observed and their kinetic parameters determined. When the rubber is stressed by shearing forces, the rate of degradation crosslinking is fairly high even at relatively low temperatures (90–150°C). Thermovulcanization of polychloroprene rubber/poly(vinyl chloride) blends has been investigated in the entire concentration range at 180°C. Maxima have been observed on the dependences of some kinetic parameters of the thermovulcanization reaction on polymer blend composition.
Influence of agitation on the creation of coagulum during the emulsion polymerization of the system styrene–butylacrylate–acrylic acid
Authors: Matějíček Alois , Pivoňková Alena , Kaška Jiří , Ditl Pavel , Formánek Leopold
Published: April 2003

This paper gives the results of the estimated coagulum content in the final sample of a dispersion based on styrene–butylacrylate–acrylic acid, prepared by semicontinuous emulsion polymerization. The results were gained from experiments on 25 L and 5 m3 reactors. The dependence of the amount of coagulum on the agitation intensity was studied. It was found that it is necessary to divide the results into two regions: (a) for specific power input smaller than 80 W/m3; (b) for specific power input greater than 80 W/m3. It was found that polymerization scaling up from the point of constant coagulum content in the system studied is possible under the conditions of constant specific power input. The specific power input varied in the range from 5 to 3000 W/m2. For the first region was gained the empiric correlation Y = 2.16(ℰV)−1 and for the second region the equation Y = 3.5 × 10−5(ℰV)1.5, where Y is the amount of coagulum (wt %). For the existence of two regions we propose the following hypothesis according to which increasing mixing intensity improves the temperature and concentration nonuniformity which results in the decrease of coagulum content. From the certain value of specific power input, which is specific for each system, the amount of coagulum starts to increase due to increasing shear stress.
Properties of syndiotactic‐rich poly(vinyl alcohol) thin film in water. V. Effect of initial temperature of heating on elongation
Authors: Yamaura Kazuo , Masuzawa Tatsuaki , Tanigami Tetsuya , Matsuzawa Shuji
Published: April 2003

The effect of the initial temperature of heating on the elongation of syndiotactic‐rich poly(vinyl alcohol) thin films was investigated in water under a load. The elongation ratios Ei after 4 h at fixed temperatures increased roughly with an increase in the initial temperature Ti and a decrease in the annealing temperature. Ei after 4 h was the smallest at Ti = 45°C for the films annealed at temperatures below 100°C. Ei was 6.8 at Ti = 60°C for the unannealed film and 1.12 at Ti = 70°C for the film annealed at 200°C. The elongation at break decreased and the temperature at break increased with an increase in annealing temperature, but those at the annealing temperature of 100°C were the smallest. The films annealed at 200°C did not break even at 98°C (boiling temperature) in water and the elongation ratio was 1.42–1.97 in the initial temperature range of 10–70°C. From these results, the relation between the elongation in water and the state of polymer chains in film was discussed.
Copolymerization of N‐vinyl‐2‐pyrrolidone and 2‐phenyl‐1,1‐dicyanoethene
Authors: Kharas Gregory B.
Published: April 2003

Radical copolymerization of N‐vinyl‐2‐pyrrolidone (NVP) with 2‐phenyl‐1,1‐dicyanoethene (PDE) was studied in benzene at 70°C. Terminal, penultimate, and monomer complex participation kinetic models were applied to compositional data for best prediction of the copolymer composition. Both penultimate and complex models described satisfactorily the deviation from the terminal copolymerization model, although the complex model did not predict as well as the penultimate model at high NVP/PDE monomer feed ratios. Copolymerization reactivity ratios rNVP = 0.08 and r′NVP = 1.8 indicated substantial effect of the penultimate PDE monomer unit associated with polar repulsion of cyano groups. Equilibrium constant of NVP‐PDE comonomer complex formation was found to be 0.08 L/mol as estimated by proton nuclear magnetic resonance (NMR) analysis of PDE's vinylic proton chemical shift upon complexation. Rate constants of propagation reactions were estimated by applying terminal complex copolymerization model.
Molecular orientation and young's modulus of plasticized and nonplasticized poly(vinyl chloride)
Authors: King J. , Bower D. I. , Maddams W. F.
Published: April 2003

The Young's moduli of samples of poly(vinyl chloride) containing either no plasticizer or 5 pph of dioctyl sebacate were drawn uniaxially at 80°C to draw ratios, λ, in the range 1–3.3. The moduli, determined by a three‐point bending method were found to increase monotonically with λ to a value of 6.3 GPa for the nonplasticized samples and to reach a maximum value of about 4.5 GPa for the plasticized samples above λ = 2.3, which showed voiding. The lower moduli of the plasticized samples for a given degree of orientation, as assessed from birefringence measurements, can be attributed to the diluent effect of the plasticizer on the load‐bearing chains. The Raman measurements suggest that the crystallites probably orient rather like rigid rods in an affinely deforming matrix, with some relaxation.
Effects of thermodynamic models on the predictions of free volume diffusion theory for concentrated polymer solutions
Authors: Mossner Linda S. , Grulke Eric A.
Published: April 2003

Three thermodynamic models were used to demonstrate the effects of model choice on solvent–polymer binary diffusion coefficients predicted by free volume theory. Poly(vinyl acetate) and four solvents were used as typical solutions for these calculations. Thermodynamic models affect the predictions the most at high solvent weight fractions and for solutions which exhibit positive enthalpic interactions. For solutions dilute in solvent where Henry's law might describe phase equilibria, diffusion coefficients can be estimated without reference to thermodynamic data.
Quantitative branching of linear and branched polysaccharide mixtures by size exclusion chromatography and on‐line low‐angle laser light scattering detection
Authors: Yu Li‐Ping , Rollings J. E.
Published: April 2003

The quantitative branching characterization of polysaccharide via size exclusion chromatography (SEC) and on‐line low‐angle laser light scattering (LALLS) detection is presented from both theoretical arguments as well as direct experimental evidence. The two measurable branching parameters gv(m) [= (Ml/(Mn)m)v] and g′v(m) [ = (Ml/(Mw)m)v] of a sample mixture have been related theoretically to the mixture's composition. There exists linear relationships between gv(m) and Wb,v (the mass fraction of branched component in mixture) as well as between g′v(m)−1 and wb,v. The latter correlation has been demonstrated experimentally employing a combined SEC/LALLS technique, and displays excellent agreement with the theoretical predictions. Furthermore, this polymer branching characterization method has been applied to study enzymatic starch hydrolysates products. The molecular weight distribution and branching distribution have been obtained.
Structural determination of pyrolyzed PI‐2525 polyimide thin films
Authors: Hu C. Z. , Andrade J. D. , Dryden P.
Published: April 2003

Polyimide was pyrolyzed in an argon atmosphere at various temperatures, and thermally converted to amorphous carbon films. The irreversible change of polyimide under progressive heat treatment is characterized by three successive structural changes: pyrolysis, carbonization, and graphitization. X‐ray photoelectron spectroscopy (XPS) studies show that the polyimide starts to dissociate at pyrolysis temperatures above 500°C. At temperatures higher than 650°C most functional groups of polyimide decompose to evolve gases from the sample. The polyimide then gradually becomes more carbon rich. It is believed that at pyrolysis temperature higher than 650°C the polyimide starts to form heterocyclic structures with residual oxygen and nitrogen incorporated into the heterocyclic carbon rings. X‐ray analyses indicate that the polyimide at pyrolysis temperatures less than 1000°C is amorphous carbon and no long‐term periodic structure can be detected. At pyrolysis temperatures higher than 2000°C, the polyimide is converted to microcrystalline graphite.
Pervaporation separation of acetic acid‐water mixtures using modified membranes. I. Blended polyacrylic acid (PAA)‐nylon 6 membranes
Authors: Huang R. Y. M. , Moreira A. , Notarfonzo R. , Xu Y. F.
Published: April 2003

Membranes consisting of ionically crosslinked polyacrylic acid (PAA) and Nylon 6 were prepared and tested for the pervaporation separation of acetic acid‐water mixtures. The polyacrylic acid (PAA) membranes were crosslinked in aluminum nitrate aqueous solution while the polyacrylic acid (PAA)‐Nylon 6 blends were cast from homogeneous PAA‐Nylon 6 mixtures to appropriate thicknesses and then crosslinked in aqueous aluminum nitrate solutions. Optimum pervaporation results were obtained from blends of Nylon 6 and PAA in the weight ratio of 60–75 wt% Nylon 6 and 25–40 wt% PAA which have separation factors (water/acetic acid) of over 60 and flux rates higher than 100 g/m2 h at 15°C for the separation of acetic acid‐water mixtures. The flux rates and separation factors could be altered by changing the blend composition of the membrane. The effects of the feed composition on the separation factors were investigated.
Electrophoretic, dynamic, and static light scattering on charged polymer emulsions
Authors: Lin F.‐M. C. , Berry G. C. , Frye R. L. , Scala L. C.
Published: April 2003

Light scattering studies on dispersions formed by phase separation of a polymer‐solvent‐non‐solvent mixture show that the dispersions comprise charged droplets of the polymer‐rich phase. The charge number is not large, and data on the electrophoretic‐scattering and the dynamic scattering in the absence of an external electric field are both consistent with distribution of charge among the droplets. Data on the dependence of the static scattering on concentration and scattering angle show that the droplets are also disperse in radius. The data are discussed in terms of an interaction potential among the charged droplets relating the electrostatic interactions to the charge number and radius of the droplets, and the ionic strength of the solvent.
Surface tension considerations for membrane casting systems
Authors: Darcovich K. , Kutowy O.
Published: April 2003

Surface energy considerations in the context of membrane preparation are examined. The viability of a membrane‐casting system can be successfully assessed with pertinent surface tension data. It is illustrated how surface tension data for multicomponent casting solutions can be used to resolve the surface structure of asymmetric reverse osmosis membranes.
Degradation of polyester waste by aliphatic and aromatic alcohols
Authors: Joshi K. A. , Naik G. A. , Nevrekar N. B.
Published: April 2003

Polyester waste was degraded with ethanol, n‐propanol, and benzyl alcohol in an autoclave at 280°C under pressure to give seven unknown compounds. The products of each reaction were isolated by using column chromatography and were identified on the basis of elemental analysis and spectral data.
The kinetics of polyarylate hydrolytic embrittlement
Authors: Golovoy A. , Cheung M. F. , Zinbo M.
Published: April 2003

The hydrolysis of polyarylate in water between 55 and 98°C was found to be a zero‐order process with an activation energy of 19.2 kcal/mol, determined by changes in molecular weight. The equation for the effect of temperature on the rate of hydrolysis is ln k = 34.1 − 104/T, where k is in day−1. The decrease in molecular weight is accompanied by a loss in ductility. The transition from a ductile to brittle failure in tension occurs at M̄w of about 35,000 and M̄n of 12,700. At 27°C (80°F) and high humidity environment this would occur after 21 years. But during injection molding, the material, if not properly dried, would embrittle in a matter of seconds.
Solid state C‐13 NMR characterization of textiles: Qualitative and quantitative analysis
Authors: Colletti Ronald F. , Mathias Lon J.
Published: April 2003

Cross‐polarization magic angle spinning (CP/MAS) carbon 13 NMR was used to qualitatively and quantitatively characterize textiles of various compositions. Rapid and accurate determination of cotton/polyester blends was accomplished with minimal sample preparation using an empirical peak height relationship. Qualitative identification was demonstrated for various fiber blends.
Surface composition of polystyrene
Authors: Goldblatt Ronald D. , Scilla Gerald J. , Park Jae M. , Johnson Julian F. , Huang Samuel J.
Published: April 2003

The physical and chemical properties of bulk polymers are well understood and have been measured exhaustively for numerous systems, but the properties of polymer surfaces are quite often different from those observed in the bulk and are usually not as easily measurable. Since many polymer properties vary with molecular weight, it is of interest to determine whether or not there is any segregation in a homopolymer system based on molecular weight. In particular, does the surface of a polymer sample have the same molecular weight composition as the bulk? The current work answers this question for a polystyrene system. Through the use of secondary ion mass spectrometry and tagged polystyrene, it has been shown that surface and bulk molecular weight composition are indistinguishable within the limits of the experimental method's sensitivity. The sensitivity of the technique is documented using samples artificially created with different surface and bulk molecular weight compositions.
Dyeing of silk cloth with colloidal gold
Authors: Nakao Yukimichi , Kaeriyama Kyoji
Published: April 2003

Silk cloth was dyed successfully by dipping it in a gold hydrosol which was prepared in the presence of a cationic surfactant, stearyltrimethylammonium chloride (SC). The color of thus dyed silk cloths is due to colloidal gold particles adsorbed on silk fibers and varies from reddish purple to dark purple according to the periods of dipping time and the amounts of SC in the gold hydrosol used. The mechanism for the adsorption of colloidal gold on the silk fibers is proposed.
Radiation‐induced polymerization of methyl methacrylate and alkyl acrylates at high dose rate
Authors: Hayashi Kanae , Takezaki Jun'ichi , Okada Toshio , Sakurada Ichiro
Published: April 2003

Polymerization of methyl methacrylate and methyl, ethyl, and n‐butyl acrylates was carried out in a wide range of dose rate, 10–106 rad/s by γ‐ray and electron beam irradiation. With methyl methacrylate and n‐butyl acrylate, and steady‐state kinetics in radical polymerization was maintained in an entire dose rate range at about the initial stage of the polymerization. With methyl and ethyl acrylates, the rate of polymerization increased much less markedly than expected from the square root law and the molecular weight decreased much less gradually with dose rate. In all these monomers it was found that autoacceleration of the rate of polymerization due to gel effect becomes vague at high dose rate. Two‐peaked molecular weight distribution was observed for the polymers obtained at high dose rate.
A qualitative model for the mechanical behavior of pretreated asbestos‐epoxy composites
Authors: Papaspyrides C. D. , Papanicolaou G. C.
Published: April 2003

The aim of the present work was to investigate the effect of fiber pretreatment, fiber content, coating concentration, and also pretreatment procedure on the tensile properties of asbestos‐epoxy composites. These composites comprise materials of considerable industrial importance. Asbestos exhibits unique properties. Occasionally it is difficult to disperse asbestos properly because the individual fibrils are very small and tend to agglomerate, but there is no evidence that asbestos is not easily wetted out by all systems. However, the higher potential aspect ratio of asbestos fibers compared with glass is not always realized in practice because the fibers break in length to fine diameters. Accordingly, the very considerable new surface created makes successful wetting difficult or impossible. For this reason, asbestos was precoated with a well adhered film of poly(hexamethylene adipamide), a polymer especially compatible with the epoxy phase. The pretreatment procedure followed was based on the principles of the interfacial polymerization involving the serial application to the asbestos of two immiscible solutions of hexamethylenediamine and adipoyl chloride. Accordingly, epoxy‐nylon‐chrysotile composites were made while varying pretreated fiber volume fraction, concentration of the polyamide coating, and reactants application order. Results obtained from tensile measurements proved quite interesting: Relative modulus of elasticity and relative ultimate strength exhibited a similar behavior when correlated with the ratio of polyamide to asbestos concentration. The corresponding curves pass through distinct maxima at which severe improvement of the material performance is effected. A thorough interpretation of these results is also included.
Polyethers. I. Polyethers from 2,4‐dichloroquinolines and alkylene diols
Authors: Patel M. G. , Patel K. C. , Patel S. R.
Published: April 2003

Polyethers are prepared by condensing, respectively, 2,4‐dichloroquinoline and its 6‐methyl and 6‐methoxy derivatives separately with ethylene, propylene, butylene, diethylene and triethylene glycols. These polyethers are characterized and the electrical conductivity of polyethers is measured at various temperatures up to 150°C.
Viscoelastic properties and coating performance of acrylic copolymers crosslinked with melamine resin
Authors: Takahashi Seiichi , Okoshi Noboru , Matsumoto Takanori , Ikeda Takenori
Published: April 2003

For 8 carboxy and hydroxy functional acrylic copolymers crosslinked with melamine resin, glass transition temperature (Tg), molecular weight of chain segments between crosslinked point (Mc), and polymer‐solvent interaction parameters (χg ) were determined by dynamic mechanical measurements and swelling measurements. Tg increases and Mc decreases with the increase of hydroxyl value and the molecular weight of acrylic copolymers. Tg decreases and Mc increases with the increase of alkyl chain length of acrylate in acrylic copolymers. The film hardness, Tg and polarity of methyl methacrylate (MMA) containing acrylic‐melamine‐cured films are higher than those of styrene‐containing acrylic‐melamine‐cured films, but both films are almost the same in the degree of crosslinking (maximum loss tangent, tan δmax, and Mc). Tg increases and Mc decreases with the increase of melamine resin content for acrylic‐melamine coatings. The cured film consists of the acrylic‐melamine segments and the melamine‐melamine segments at crosslinking points. The carboxy group enhances the crosslinking reactions at low temperatures. All films crosslinked have single glass transition temperatures and broad damping peaks, which show good compatibility. The values of χg of acrylic copolymer‐melamine films in polar and nonpolar solvents depend on the polarity of acrylic composition and the degree of crosslinking. χg values of carboxy functional acrylic‐melamine film in any solvents are smaller than that of carboxy and hydroxy functional acrylic‐melamine film. χg values of MMA‐containing acrylic‐melamine film in polar solvents are smaller than those of styrene‐containing acrylic‐melamine film, but χg values of MMA‐containing acrylic‐melamine film in nonpolar solvents are larger than those of styrene‐containing acrylic‐melamine film. χg values of acrylic‐melamine film in polar and nonpolar solvents increase with the increase of alkyl chain length of acrylate. The χg values of acrylic‐melamine coatings in toluene are less than 0.3 and smaller than those of alkyd coatings.
Behavior of azo dyes dispersed in fluid polymeric matrices with different rheological properties. A kinetic study of the cis‐trans isomerization of 3′‐nitro‐4‐diethylamino azobenzene in polyethylenoxides
Authors: Dubini‐Paglia Ernestina , Beltrame Pier Luigi , Marcandalli Bruno , Seves Alberto , Vicini Loredana
Published: April 2003

The thermal cis‐trans isomerization of 3′‐nitro‐4‐diethylaminoazobenzene in seven polyethyleneoxides at different molecular weight has been studied kinetically in the temperature range 35–70°C. The dependence of the reaction rate on the polymer polarity and viscosity is discussed. The kinetics of the isomerization of the dye dispersed in the fluid polymeric matrix was found to be a useful probe of the structural features of the polymer.
Heat distortion of phenolic fiber reinforced thermoplastics
Authors: Jinen Eiichi
Published: April 2003

Heat distortion temperature of phenolic short fiber‐reinforced thermoplastics (FRTP) (polystyrene, polypropylene, nylon 66), which are molded by injection, have been estimated by an ASTM standard and the reinforced effect is examined from the standpoint of the dependence on the fiber content and maximum fiber stress (bending stress). For polystyrene (PS), the temperature dependence on the fiber content and the maximum fiber stress dependence on the gradient (increase in heat distortion temperature with an increase in 1% of fiber) of these lines show a fine relation, and in regard to the heat distortion temperature, also indicates a nearly linear relation on a log–log scale. However, for the other two polymers, a good relation cannot be recognized but shows a nonlinear one. For polypropylene (PP), a decrease in the phenomenon in the heat distortion temperature dependence on fiber content is found and an interpretative explanation of the results is given.
Thermotropic polyester carbonates. II. Polyester carbonates as high performance fibers
Authors: Lai Y. C. , Debona B. T. , Prevorsek D. C.
Published: April 2003

The fiber spinning and heat treatments of spun fibers from thermotropic polyester carbonates are described. Thermotropic polyester carbonates derived from t‐butylhydroquinone, methylhy‐droquinone, diphenyl terephthalate, and diphenyl carbonate in the molar ratios of 50 : 50 : 55 : 45; 50 : 50 : 57.5 : 42.5; can be spun successfully, and after proper heat treatment, yield fibers with tenacity as high as 20 g/denier. Normally the best spinning temperature is 10–20°C above melting.
Drag reduction by polymer–polymer mixtures
Authors: Malhotra J. P. , Chaturvedi P. N. , Singh R. P.
Published: April 2003

An extensive study on the turbulent drag reduction caused by the various mixtures of polyacrylamide, purified guargum, xanthangum, and their graft copolymers has been conducted at low concentrations and Re = 14,000 using a turbulent flow rheometer. It has been found in most of the cases that the drag reduction caused by mixtures shows a positive deviation from the linearly additive straight line. This effect is more prominent when the drag reduction caused by both the constituents differ appreciably. In most of the cases, the drag reduction caused by the mixtures is higher than the DR caused by either of the constituent polymers; however, the drag reduction caused by the mixture is less than the sum of the drag reduction caused by both the constituents at their respective concentration in the mixture. It has also been noticed that there is no evidence of synergism in these mixtures at low concentrations.