bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization of diallyl phthalate at high temperatures
Authors: Strumik M. I. , Królikowski W. , Jankowska M.
Published: April 2003

The influence of high temperature (160–250°C) on diallyl phthalate polymerization has been investigated. Polymerization was carried out in a nitrogen atmosphere both with and without benzoyl peroxide as initiator, and also in a air atmosphere. A considerable increase in the conversion degree to the gelation point with a parallel increase in temperature has been established. Unsaturation degree of prepolymers remains unchanged independently of temperature and the way of polymerization initiation.
Prediction of osmotic pressures of polymer solutions
Authors: Kok Chong Meng , Rudin Alfred
Published: April 2003

A theory which has been developed to account for the effects of concentration on the equivalent hydrodynamic volumes of dissolved polymers has been combined with a statistical mechanical relation for the virial coefficients of dilute suspensions of rigid spheres. With a scaling factor for solvent goodness, osmotic pressures of polymer solutions can be predicted with good accuracy. The input parameters needed are the number‐average molecular weight of the polymer sample and its intrinsic viscosity in the solvent of interest, as well as its intrinsic viscosity under theta conditions. The intrinsic viscosities can be estimated with sufficient accuracy from tabulated Mark–Houwink coefficients. The model developed contains no adjustable parameters. Comparisons of predicted and reported experimental osmotic pressures are presented, and a method for prediction of second virial coefficients is described.
Suspension polymerization of methyl methacrylate. I. Modeling of reaction kinetics
Authors: Lin Chen‐Chong , Wang Yao‐Feng
Published: April 2003

A semiempirical model, which can simulate the behavior of free‐radical polymerization of MMA in the suspension process, is proposed. Correlation of apparent termination rate constant with conversion of such system is established as follows, log (kt/kD) = n log x′ + C. It is found that the large values of n correspond to a large gel effect and vice versa. As conversion is increased, the chains become longer and the polydispersity of product becomes larger. As temperture is increased, the polydispersity also becomes larger.
Covercoat retardation of permeation through sheet molding compound
Authors: Graedel T. E. , Franey J. P.
Published: April 2003

Permeation of gases through polymers may be retarded by applying to the polymers a coating of a less permeable material. We have devised techniques to quantitatively measure rates of water vapor permeation at typical atmospheric pressures and compositions through polymer and coating films, and we apply these techniques here to a crosslinked polyester resin with glass fiber reinforcement, coated with a crosslinked thio‐ene formulation. The coating is shown to inhibit water vapor permeation by about a factor of thirty over the uncoated value. H2S permeation constants are also derived; they are some three orders of magnitude smaller than those of H2O but show similar coated/uncoated permeation effects. The controlling factor in the retardation is suggested by experimental evidence to be a graft copolymer formed at the covercoat–sheet molding compound interface by the ultraviolet curing process.
Rubber elasticity of poly(n‐butyl acrylate) networks formed with multifunctional crosslinkers
Authors: Yeo J. K. , Sperling L. H. , Thomas D. A.
Published: April 2003

The rubber elasticity characteristics of poly(n‐butyl acrylate) networks crosslinked with tetrafunctional (EGDM and TEGDM), hexafunctional (TMPTM), and octafunctional (PETMA) vinyl crosslinkers were investigated. Both gel—sol analyses and crosslinking efficiency theories were used to evaluate the chemical crosslink contribution vc and the entanglement contribution vp to the elastically effective network chains ve, and the effect of the crosslink junction functionality f on the front factor g. The front factors obtained were in the range of 0.50–0.92, depending upon the network system and the counting method for vc. The relationship of g = [(f − 2)/f]/〈r2〉/〈r2〉o seems reasonable in the case of the tetrafunctional and hexafunctional networks, but deviates in the case of the octafunctional network. It is also evident that the functionality scheme for the front factor could only be valid under the postulate of a high vp, which increases with increasing vc, especially in the high vc region near the Gaussian limit. The average energetic contribution to the retractive force of the present systems, expressed as Fe/F, is −0.30 ± 0.1.
Novel oxidatively drying urea resin. I. Drying properties of urea resins prepared from N,N′‐bis(methoxymethyl) urea and alcohols containing allyl ether groups
Authors: Toivonen Hannu
Published: April 2003

A new type of urea resin prepared by copolycondensating N,N′‐bis(methoxymethyl) urea with an alcohol containing allyl ether groups have been studied and found to have adequate drying properties when used for surface coating purposes. The drying behavior of the resins can be controlled by conventional drier metals, cobalt being an efficient catalyst. Calcium was found to have a synergetic effect with cobalt on drying, zinc and lead had no synergetic effect, and manganese and sodium hydroxide acted as drying inhibitors. Increasing the amount of allylic alcohol in the monomer mixture and higher molecular weight led to the formation of a faster drying resin. The molecular weight distribution of the resins was found to have an effect on the surface coating properties. It was found that for resins having an equal drying rate those with a broader molecular weight distribution had higher solution viscosities. Resins with a narrow molecular weight distribution were also found to be advantageous when formulating coating compositions containing a minimum concentration of solvents.
Semicontinuous emulsion copolymerization of ethyl acrylate and butyl acrylate at high conversions
Authors: Šňupárek Jaromír , Kašpar Karel
Published: April 2003

Semicontinuous emulsion copolymerization of ethyl acrylate and butyl acrylate was studied at conversions higher than 0.9. It was found that, in the cases in which the mole fraction of ethyl acrylate in the reaction mixture was over 0.65, the copolymerization diagram differs from the one given by the reactivity ratios. It was suggested that this deviation was caused by the diffusion control of the process. This suggestion was also supported by the differences in the free‐monomer composition of the systems with and without seed latex, respectively, at the beginning of the copolymerization.
Study of the thermal degradation of acrylic copolymers
Authors: Tomescu Margareta , Demetrescu Ioana , Segal E.
Published: April 2003

The thermal degradation of the following copolymers prepared by radical polymerization: acrylonitrile–butyl acrylate–vinylidene chloride, acrylonitrile–butyl acrylate–vinylidene chloride–styrene, and acrylonitrile–methacrylic acid–vinylidene chloride–styrene was investigated. The techniques of thermogravimetry and differential thermal analysis were used. The IR spectra of degradated copolymers are discussed.
Transport from an aqueous phase through cellulosic gels and membranes
Authors: Brown Wyn , Johnsen Robert M.
Published: April 2003

Diffusion of some homologous series of solutes [polyhydric alcohols, oligosaccharides, poly(ethylene oxide) polymers] has been studied in cellulose gels (<20% w/w) and membranes (<60% w/w) and the same materials when acetylated. It was found that (1) The molecular weight dependence of D approximates that for the solutes in water alone; the activation energies are also identical to the value for diffusion in pure solvent. (2) The presence of the cellulose chains reduces the rate of diffusion to a degree which is approximately given by the Mackie—Meares equation. (3) Exclusion is pronounced, particularly with the acetylated membranes, and gives a high degree of molecular size discrimination by a sieving mechanism. The membranes have a very narrow range of “pore” sizes, whereas the gels have a contrastingly broad distribution.
Anodic synthesis of polyaniline coatings onto fe sheets
Authors: Mengoli Giuliano , Munari Maria Teresa , Bianco Paolo , Musiani Marco M.
Published: April 2003

Aniline Black coatings were obtained on Fe anodes by electrolyzing a basic solution of aniline in a water—methanol medium. Allylamine (an inhibitor of Fe corrosion), although not essential to the process, imparts better efficiency to it. The deposited polymers contain 15–20% azobenzene and exhibit semiconductor properties. The three nitroaniline isomers need a more efficient corrosion‐inhibition system. They may be polymerized to adherent films in the presence of both allylamine and K2CrO4.
Effects of polydispersity on critical concentration of polymer solutions
Authors: Chee K. K.
Published: April 2003

A semiempirical equation is developed to compute the unperturbed parameter from the critical concentration of polymer solutions derived from the viscometric and kinetic data. This equation gives satisfactory results for various vinyl polymers including poly(vinyl chloride), polystyrene and poly(methyl methacrylate) among others that follow the Schulz molecular weight distribution function. It is found that the segments of a Gaussian polymer chain are associated with an equal number of foreign segments near its center of mass, when the polymer solution has attained a uniform segment density at the critical concentration. The effect of molecular weight distribution on the present studies is significantly large that it merits an empirical treatment. Defects of the model is also discussed.
Chain extension of partially neutralized carboxyl‐terminated liquid polybutadiene with bisepoxide
Authors: Matsuda Hideaki
Published: April 2003

Chain extension of partially neutralized carboxyl‐terminated liquid polybutadiene (PB) with bisepoxide was investigated by the carboxyl–epoxide reaction. The partially neutralized liquid PB were prepared, by the partial neutralization with MgO and CaO, from a carboxyl‐terminated liquid PB (Hycar CTB 2000X162). As the bisepoxide, hydroquinone diglycidyl ether was used. The metal carboxylate groups in the system catalyzed the reaction and, further, the Mg carboxylate group showed higher catalytic activity than the Ca carboxylate group. The chain‐extended metal‐containing PB obtained by the reaction were found to be elastic when subjected to a rapid impact, but plastic under slowly applied stress and their solution behavior in pyridine was examined. The viscosities were very low at very low concentrations but increased markedly as the concentration increased. This solution behavior is attributed to ionic associations of carboxylate anions and metal cations to longer chains. Further, thermal and other properties were evaluated.
Vapor phase dyeing of synthetic fibers with disperse dyes
Authors: Bendak A. , Abdou L. A. , El‐Kashouti M.
Published: April 2003

Dyeing of synthetic fibers by the heat transfer process of disperse dye vapors is performed by contacting white receptor polyester or polyamide fabric with other dyed polyester fabrics (donor) under the influence of heat. The dye vapours flowing away will diffuse across the very slight air gap enclosed between the inner donor and receptor surfaces under the applied pressure. It is found that the dye uptake by the receptor fabric is dependent on the original dye content of the donor fabric, transfer temperature and dwell time. The released dye from the donor fabric under the influence of heating is found to be dependent on the original dye content of the donor fabric as well as the transfer temperature. The efficiency of the dye transfer is also attributed to the original shading of the donor fabric. Evaluation of the imparted colors on the receptor fabric (polyester, polyamide) obtained by heat contact with the same donor fabric showed visually the same colour level up to the 13th run. Thermodynamic interpretation of the standard affinity (Δu0) and heat of dyeing (ΔH0) as well as the partition coefficient of the dye show that the dyeing process has an exothermic character. The rate controlling step in this dyeing process is found to be dependent on the diffusion of the dye vapors into the fiber phase.
Graft polymerization of acrylic acid onto polyethylene film by preirradiation method. I. Effects of preirradiation dose, monomer concentration, reaction temperature, and film thickness
Authors: Ishigaki Isao , Sugo Takanobu , Senoo Keiji , Okada Toshio , Okamoto Jiro , Machi Sueo
Published: April 2003

Low‐and high‐density polyethylenes were irradiated by electron beams with dose of 2–50 Mrad and then immersed in aqueous solution of acrylic acid (monomer concentration from 30 to 100 wt %) for 10 min−5 h at a temperature of 25–40°C. The degree of grafting increases with time and levels off. High density polyethylene shows lower grafting rate and higher final % grafting in compared with low‐density polyethylene. Both grafting rate and final % grafting increase with total dose of preirradiation, but show some saturation at high doses. The highest grafting rate was observed at 60 wt % of monomer concentration where the grafted polyethylene swells to the largest extent in the monomer mixture. Apparent activation energies for the grafting are 19.6 and 27.3 kcal/mol for low‐ and high‐density polyethylenes, respectively, reflecting the proces of monomer diffusion in the film. Grafting rate decreases with increasing film thickness. Graft polymerization starts on the surface of the film and proceeds to the inner part with monomer diffusion through the grafted layer.
Effects of foaming variables on density and morphology of expanded ethylene–propylene terpolymers
Authors: Wang C. S.
Published: April 2003

An experimental study of the relationships between foaming variables and foamed structures of expanded ethylene–propylene terpolymer (EPDM) is reported. The study was carried out using EPDM composition containing azobisformamide blowing agent. The compositions were expanded and cured in hot air into a foamed structure consisting of dense skin and foamed core. The results showed that the foam density, skin thickness, average cell size, and number of cells of the expanded rubbers can be controlled closely by the foaming variables such as residence time, foaming temperature, and blowing agent concentration.
Rheological properties of liquid crystalline copolyesters
Authors: Prasadarao M. , Pearce E. M. , Han C. D.
Published: April 2003

Copolyesters were synthesized by modifying poly(ethylene terephthalate) (PET) withp‐acetoxybenzoic acid (PAB) and hydroquinone diacetate/tetrasubstituted (tetramethyl, tetrachloro, and tetabromo) terephthalic acid (HQTS). It was found that the copolyesters containing 33 mol% or higher concentrations of (PAB+HQTS) from mesomorphic liquid crystalline structures. Rheological properties of copolyesters formed of PET, modified with PAB and hydroquinone diacetate/tetramethyl terephthalic acid (HQTM), were measured using a cone‐and‐plate rheometer. It was found that the copolyesters in the mesomorphic state exhibit yield values at a low shear rate (or at a low shear stress), and negative values of first normal stress difference were observed for certain compositions of (PAB+HQTM), over the range of shear rates (or shear stresses) tested.
Resistance of a polyetherimide to environmental stress crazing and cracking
Authors: White S. A. , Weissman S. R. , Kambour R. P.
Published: April 2003

The environmental stress crazing and cracking (ESC) behavior of an aromatic polyetherimide (PEI) has been characterized in a wide spectrum of organic liquids and compared to the behavior of several other glassy thermoplastics. PEI's response is qualitatively similar to that of the other resins for each of which ESC resistance reaches a minimum in solvents having solubility parameters close to that of the resin. Taken as a whole, the ESC resistance of PEI is found to be quantitatively superior to that of any other glassy resin for which similar data are available for comparison.
Water‐soluble copolymers. V. Compositional determination of random copolymers of acrylamide with sulfonated comonomers by infrared spectroscopy and C13 nuclear magnetic resonance
Authors: McCormick Charles L. , Chen Gow‐Sheng , Hutchinson Brewer H.
Published: April 2003

Compositional analyses of random copolymers of acrylamide with sodium‐2‐sulfoethyl methacrylate and with sodium‐2‐acrylamido‐2‐methylpropane sulfonate have been performed utilizing elemental analysis, infrared spectroscopy, and C13 NMR. A mathematical method involving nitrogen to sulfur ratios has been developed to eliminate errors which often arise from associated water in hydrophilic copolymers. The ratios of infrared absorbances at 1043 cm−1 and 1664 cm−1 were used to determine the composition of AM—NaAMPS copolymers; likewise, absorbance ratios at 1040 cm−1 and 3200 cm−1 were utilized for determination of the AM—NaSEM copolymer composition. Carbon‐13 NMR spectra of the copolymers were also obtained, and characteristic peaks were utilized to quantitate copolyer composition. The results obtained by elemental analyses, infrared spectroscopic studies, and NMR were in excellent agreement. These techniques are of great value for determining composition of hygroscopic copolymers which can crosslink or form strong intramolecular hydrogen bonds, often precluding further characterization.
Polymorphism and orientation development in melt spinning, drawing, and annealing of nylon‐6 filaments
Authors: Gianchandani J. , Spruiell J. E. , Clark E. S.
Published: April 2003

A new method has been developed for determining the total crystallinity and relative amounts of α‐ and γ‐phases in nylon‐6 samples. The procedure is based on a combination of X‐ray and density data and does not require complicated analytical procedures to separate overlapping reflections. The technique has been applied to study the structural changes accompanying the melt spinning, annealing, and drawing of nylon‐6 filaments. Higher spin draw ratios result in higher crystallinity, greater relative amounts of γ‐phase, and higher orientation. Annealing up to 2 h in boiling water or a 20% aqueous formic acid solution decreases the γ‐phase content, increases the α‐phase content and total crystallinity, but does not eliminate all of the γ‐phase in samples spun with high spin draw ratios. Annealing in vacuum also increases the α‐phase content when annealing is carried out at temperatures above 120°C, but there is little effect below this temperature. Drawing of as‐spun and conditioned filaments at 90°C also increases the α‐phase content and decreases the γ‐phase content. The total crystalline content increases with draw ratio for samples with low spin draw ratios, but drawing has little effect on the total crystalline content of samples spun with higher spin draw ratios. Drawing also results in substantial increases in orientation, especially for samples spun with low spin draw ratios. The effects of these changes in structure on the mechanical properties are also described.
A comparative study of stress‐induced crystallization of guayule, hevea, and synthetic polyisoprenes
Authors: Shimomura Yasushi , White James L. , Spruiell Joseph E.
Published: April 2003

A comparative study of the stress induced crystallization of natural (Hevea, Guayule) and synthetic high cis‐1,4‐polyisoprenes at room temperature is presented. Hevea and Guayule are both found using WAXS to crystallize into the unit cell of Morss and Bunn previously described for Hevea. DSC studies of polyisoprenes held at −25°C indicate that Hevea and Guayule crystallize more rapidly than synthetics. Studies of relative birefringence and stress decay following uniaxial extension confirm this. Under conditions of comparison at the same stress, raw Hevea crystallizes more rapidly than extracted Hevea, Guayule, and the other polyisoprenes.
Vinyl graft polymerization‐induced modification of some properties of poly(ethylene terephthalate) fabric
Authors: Hebeish A. , Shalaby S. E. , Bayazeed A. M.
Published: April 2003

Polymerization of glycidyl methacrylate (GMA), methyl methacrylate (MMA), and acrylic acid (AA)/styrene (St) mixtures with poly(ethylene terephthalate) (PET) fabric to different polymer add‐ons was performed. Moisture regain, dyeability, and soiling properties of the modified PET were examined. It was found that introduction of poly(GMA) in PET structure brings about (a) improved moisture regain, (b) enhanced dyeing with disperse dyes, (c) affinity and possible dyeing with acid, direct, and reactive dyes, (d) improved aqueous and nonaqueous oily soil resistance, and (e) decreased ease of soil removal. The magnitude of moisture regain, dyeability, and soiling properties are dependent upon the percent of polymer add‐on. Polymerization of MMA with PET improved the dyeability of the latter with the disperse dye as well as its resistance to nonaqueous oily soil while decreasing the resistance to aqueous soiling and ease of both aqueous and nonaqueous soil removal. In the case of PET polymerized with poly(AA/St), there was a considerable enhancement in moisture regain, dyeing with the disperse dye, and resistance to aqueous and non‐aqueous oily soiling. On the other hand, both aqueous and nonaqueous soil characteristics of PET were imparted by polymerization of the latter with AA/St mixtures.
Craze initiation and growth in high‐impact polystyrene
Authors: Donald Athene M. , Kramer Edward J.
Published: April 2003

Quantitative transmission electron microscopy and optical microscopy is used to study craze initiation and growth in thin films of high‐impact polystyrene (HIPS). Dilution of the HIPS with unmodified polystyrene reduces the craze–craze interactions, permitting equilibrium growth and craze micromechanics to be studied. It is found that the equilibrium craze length depends on the size of the nucleating rubber particle, but not the internal structure; no short crazes less than a particle diameter are observed. The long crazes can be adequately modelled by the Dugdale model for crazes grown from crack tips. The effects of particle size and particle internal occlusion structure on craze nucleation have been separated. Craze nucleation is only slightly enhanced at highly occluded particles relative to craze nucleation at solid rubber particles of the same size. There is a strong size effect, however, which is independent of particle internal structure. Crazes are rarely nucleated from particles smaller than ∼1 μm in diameter, even though these make up about half the total number. These craze nucleation and growth effects may be understood in terms of two hypotheses for craze nucleation: (1) the initial elastic stress enhancement at the rubber particle must exceed the stress concentration at a static craze tip and (2) the region of this enhanced stress must extend at least three fibril spacings from the particle into the glassy matrix. Since the spatial extent of the stress enhancement scales with the particle diameter, the second hypothesis accounts in a natural way for the inability of small rubber particles to nucleate crazes.
Light scattering from polyethylene solutions
Authors: Stejskal Jaroslav , Horska Jitka , Kratochvíl Pavel
Published: April 2003

The technique of measurement of light scattering from dilute polyethylene (PE) solutions is reviewed. Conditions are discussed under which various PE samples can be characterized. The choice of the solvent affects the accuracy of molecular weight determination. It appears that measurement with thermodynamically poorer solvents yields results subjected to a smaller error. The interpretation of light scattering data is often disturbed by the presence of supermolecular structures in PE solutions. The effect of reprecipitation on the behavior of PE samples is described. The measurements were mostly performed on PE standards and on the Czechoslovak sample Liten Macro.
Melting and crystallization behavior of miscible copolyester–polycarbonate blends
Authors: Barnum R. S. , Barlow J. W. , Paul D. R.
Published: April 2003

The melting and crystallization behavior of Kodar, a copolyester formed from 1,4‐cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids, and its miscible blends with polycarbonate was examined. The results of the melting behavior are discussed in terms of crystallization‐induced chemical rearrangements and the copolymeric character of Kodar and interchange reactions between components when polycarbonate is present in the blend. For various reasons, the melting behavior cannot be extrapolated to infinite crystal size using the Hoffman–Weeks approach. Crystallization kinetics follows the Avrami equation, with rates being higher when the crystallization temperatuare is approached from the glass rather than from the melt. The kinetic data are discussed in terms of modern theories. An approximate melting point depression analysis is used to estimate the interaction parameter for the blend, and the result obtained is compared to a value from another technique.
Effects of water on starch‐g‐polystyrene and starch‐g‐poly(methyl acrylate) extrudates
Authors: Henderson Alex M. , Rudin Alfred
Published: April 2003

Polystyrene and poly(methyl acrylate) were grafted onto wheat starch by gamma radiation and chemical initiation, respectively. The respective percent add‐on values were 46 and 45;68% of the polystyrene formed was grafted to starch, and the corresponding proportion of poly(methyl acrylate) was 41%. The molecular weight distributions of the homopolymer and graft portions were characterized, and extrusion conditions were established for production of ribbon samples of starch‐g‐PS and starch‐g‐PMA. Both copolymer types were considerably weakened by soaking in water, and this effect was more immediate and drastic for starch‐g‐poly(methyl acrylate). Both graft copolymers regained their original tensile strengths on drying, but the poly(methyl acrylate) specimens did not recover their original unswollen dimensions and retained high breaking elongations characteristic of soaked specimens. Tensile and dynamic mechanical properties of extruded and molded samples of both graft polymers are reported, and the plasticizing effects of water are summarized.
Ionic conductivity of hybrid films based on polyacrylonitrile and their battery application
Authors: Watanabe Masayoshi , Kanba Motoi , Nagaoka Katsuro , Shinohara Isao
Published: April 2003

The alternate current (AC) and direct current (DC) ionic conductivity of hybrid films composed of polyacrylonitrile (PAN), lithium perchlorate (LiClO4), and a plasticizer was studied. Three kinds of the plasticizer [ethylene carbonate (EC), propylene carbonate (PC), N,N‐dimethylformamide (DMF)] were used. Suitability of these hybrid films for lithium battery was investigated. The AC conductivity, which represents bulk ionic conductivity, was dependent on the component and the composition of the hybrid films, ranging from 10−4−10−8 Scm−1. The AC conductivity was mainly determined by the molar ratio of [plasticizer]/[LiClO4] in the hybrid films and increased with the increase in this ratio. The effect of the plasticizer on the enhancement in the AC conductivity was in the following order. DMF>EC>PC. The hybrid films with both electrodes of lithium showed the stable DC conductivity of about 1/10 of the AC conductivity, except for the hybrid films containing DMF. The hybrid films were found to be effective as a lithium ionic conductor. The galvanic cell. Li/sample/MnO2, at the discharge current density of 90 μA/cm2 showed the stable electromotive force of about 3 V for 70 h.
Separation of proteins by polymeric adsorbents containing azobenzene moiety as a ligand
Authors: Ishihara Kazuhiko , Kato Shinji , Shinohara Isao
Published: April 2003

Polymeric adsorbents containing an azobenzene moiety as a ligand were prepared, and the photoinduced adsorption behavior of proteins to the adsorbent was studied. This method regulates by light the adsorption/desorption of proteins in hydrophobic chromatography. In the dark, the amount of protein adsorbed onto the adsorbent increased with increasing hydrophobicity of either adsorbent or protein. On irradiation with UV light, the amount of protein adsorbed decreased. Such a photoinduced change of the adsorption of protein was considered to be caused by the change of the hydrophobic interaction between the adsorbent and the protein due to the photoisomerization of the azobenzene moiety accompanying the polarity change of the adsorbent. It is also found that the desorption of protein was dependent on the balance of the hydrophobicity between the adsorbents and proteins. When column chromatography was carried out, the proteins were adsorbed in the dark and could be eluted after photoirradiation, with water as the single solvent. Furthermore, mixture of proteins could be separated by using a hydrophobic gradient column which was constituted by two polymeric adsorbents having different hydrophobicity.
Effect of particulate fillers on short jute fiber‐reinforced natural rubber composites
Authors: Murty V. M. , De S. K.
Published: April 2003

The effect of carbon black on the processing characteristics and physical properties of jute fiber‐reinforced composites and the role of silica and carbon black in promoting the adhesion between jute fiber and natural rubber have been studied. It was found that presence of silica is not essential to develop adhesion between fiber and rubber in the presence of carbon black. However, silica and carbon black can improve adhesion by minimizing the resin formation and controlling it to a low molecular weight species. Processing properties like green strength and mill shrinkage are improved by the addition of fiber. Carbon black does not affect mill shrinkage, but improves the green strength. Breakage of jute fiber during mixing is severe, but the extent of breakage is not affected by the presence of carbon black. The minimum loading of fiber to achieve reinforcement is reduced in the presence of carbon black. It was also found that the presence of clay in jute fiber rubber composites impairs the properties. Scanning electron microscopy (SEM) has been used to assess the failure criteria.
A heat and mass transfer study—analysis of continuous processes for the coloration of polyester fabric. II. Modelling and characteristics of the (polyester) fabric heating
Authors: Akaoui Sami E.
Published: April 2003

First it is shown how the equations used for the numerical solution of the transient heat transport to a body can be reduced to the simple transport model (of Paper I), which is commonly used in the textile literature for estimating the heat transfer coefficient (h) of the various fabric heating equipment. During the thermal treatment of a fabric that can be approximated by a geometrically stable homogeneous plate, the simple transport model should not be used for calculating h in cases of high heating rate equipment (e.g., direct contact units) instead; the numerical solution should be used. For a fabric that becomes geometrically unstable during a thermal treatment, like polyester knits, the h value obtained by fitting the numerical solution to the fabric heating rate measurement becomes an apparent coefficient that is the function of the fabric thermal history rather than the equipment heating efficiency. However, if the objective of the modelling is to represent the geometrically unstable fabric heating rate, the simple transport expression is a viable alternative to an otherwise intricate model.
Carbon‐fiber‐reinforced phenolics
Authors: Chang E. P. , Kirsten R. O. , Harrington H. J. , Slagowski E. L.
Published: April 2003

Carbon‐fiber‐reinforced (CFR) phenolic composites with equivalent mechanical properties and much superior thermal stability to laboratory‐prepared and present commercial epoxy analogs have been achieved by reinforcing 35‐50 wt % of an amine‐catalyzed resole with either the Hercules' Magnamite carbon fabric or the Great Lakes' Varinit carbon fiber/glass cloth hybrid. Improvement of the interlaminar shear strength (ILSS) of the hybrid‐reinforced phenolic laminates was observed with increasing molding pressure and alternate carbon/glass/carbon/glass geometry. Sizings on the carbon fiber do not have any significant effect on the mechanical properties.
Mechanical properties of polypropylene/crosslinked rubber blends
Authors: Dao K. C.
Published: April 2003

Mechanical properties of rubber‐modified polymers are not single‐valued functions of rubber/matrix type and rubber content, but also vary with processing conditions. The variations in mechanical properties with processing conditions arise mainly from changes in rubber‐phase dispersion. In our past work, by lightly crosslinking the rubbers to increase their melt tenacity and strength, we have succeeded in producing fine and consistent dispersions despite diverse processing conditions. In this study, mechanical properties of polypropylene/lightly crosslinked rubber blends are compared with those of polypropylene/uncrosslinked rubber blends. The results indicate that, like dispersion, mechanical properties of polypropylene/crosslinked rubber blends also appear to be consistent and independent of process variables. The influences on mechanical behavior of degree of crosslinking, rubber content, and rubber/matrix type are also discussed.
High‐temperature coupling of high‐speed GPC with continuous viscometry. I. Long‐chain branching in polyethylene
Authors: Lecacheux D. , Lesec J. , Quivoron C.
Published: April 2003

The coupling of a high‐temperature liquid chromatograph (Waters 150C) with a home‐made continuous capillary viscometer is described. This detector is the only one suitable for high‐speed GPC when the small volume of the mobile phase prohibits the coupling with a classical viscometer. The pressure drop of the GPC effluent through the capillary is continuously measured along with the refractive index change. This dual detection leads to the determination of the intrinsic viscosity as a function of the elution volume, thus allowing a precise use of Benoit's universal calibration. The accuracy of our system is demonstrated in the case of the characterization of linear and branched polyethylene samples. The results concerning the average molecular weights as well as the branching factors (structure parameter g′ and long‐chain branching frequencyλ) are in close agreement with those obtained by the classical way (coupling traditional GPC and discontinuous viscometry). It is well known that an estimate of the λ coefficient is extremely dependent on several hypotheses. However, for a set of commercial low‐density polyethylenes, we obtained λ values about 0.5 × 10−4, with no marked change along the molecular weight range.
Static versus dynamic evaluation of cushioning properties of plastic foams
Authors: Gruenbaum Gad , Miltz Joseph
Published: April 2003

The protective properties of several plastic foams, represented by cushioning curves calculated from static stress–strain curves, were compared to those obtained in shock tests. It was found that the amount of energy absorbed in the two types of tests is almost the same, while the force applied to the product is about 30–50% higher in the dynamic test. Accordingly, the relatively simple static test may be used for choosing the most suitable foam for protection of a fragile product.
Addition polyimides. I
Authors: Varma Indra K. , Gupta Ashok K. , Sangita  , Varma D. S.
Published: April 2003

Crosslinking of 4,4′(bismaleimido)diphenyl ether (BM) was investigated in presence of bis(m‐aminophenyl)methylphosphine oxide (BAP), tris(m‐aminophenyl)phosphine oxide (TAP), diaminodiphenyl ether (E) and 3,3‐bis(p‐aminophenyl)phthalide (AP). These crosslinked resins were examined for thermal stability by thermogravimetric analysis. A slight decrease in initial decomposition temperature, the temperature of maximum rate of weight loss, was observed, though the char yield in nitrogen atmosphere at 800°C did not change appreciably. Glass‐cloth‐reinforced laminates were fabricated from BM and amine mixtures. An improvement in mechanical properties was observed in the presence of phosphorus‐containing di‐ and triamines.
Transient sorption of sulfur dioxide in epoxy resin of aliphatic diglycidyl ether
Authors: Ranade G. R. , Nadgir V. M. , Plank C. A. , Laukhuf W. L. S.
Published: April 2003

Diffusion of sulfur dioxide in epoxy resin of aliphatic diglycidyl ether was studied performing differential sorption kinetic measurements at temperatures ranging from 1°C to 45°C and activities varying from 0.12 to 0.55. The diffusion of sulfur dioxide appears to be Fickian over the entire temperature range studied. There is a marginal increase in the diffusion coefficient with increase in concentration. The diffusion coefficients evaluated from both “small times” data and “large times” data are in reasonable agreement.
Crosslinking kinetics and network formation in organic coatings containing hexamethoxymethylmelamine
Authors: Bauer D. R. , Budde G. F.
Published: April 2003

We have developed a kinetic model of the crosslinking reaction of hydroxy‐functional acrylic copolymers with fully alkylated melamines. This model accurately describes the extent of the crosslinking reaction as a function of cure time and melamine concentration in coating films. Using this model, we have determined the effects of acid catalyst concentration and strength and the effects of cure temperature on the rate constant of the crosslinking reaction. The rate constant is proportional to the catalyst concentration and to the square root of the acid constant of the catalyst. The temperature dependence of the rate constant follows an Arrhenius rate law with an activation energy of 12.5 kcal/mol independent of catalyst type. Amine salts of p‐toluenesulfonic acid have been compared with p‐toluenesulfonic acid as catalysts in these coatings at different bake temperatures. These kinetic results have been used in a network structure model to calculate the cure response of these coatings as a function of formulation variables.
Effect of metal cyanourates on some properties of PVC
Authors: Gancheva Tamara Stancheva , Kolarova Maria Nikolova , Marinova Atanasia Todorova , Alaminov Christo
Published: April 2003

The effects of barium, lead and calcium cyanourate on the properties of poly(vinyl chloride) and its compositions were investigated. In concentrations up to 2 vol. % they decreased the Tg and Tm of the polymer. Physical and mechanical properties (tensile strength, impact strength, and hardness) are improved. The thermostability (dynamic and static) increases with increasing concentration.
Stabilization of gamma‐irradiated poly(vinyl chloride) by epoxy compounds. III. Conjugated double bonds and degree of unsaturation in gamma‐irradiated PVC–stabilizer mixtures
Authors: Lerke G. , Lerke I. , Szymański W.
Published: April 2003

The concentration of conjugated polyene sequences was studied in γ‐irradiated PVC with 4% admixture of four epoxy stabilizers: diglycidyl ether of 2,2‐bis(4‐hydroxy‐3‐methylphenyl)propane (I), styrene oxide (1,2‐epoxy ethyl benzene) (IV), epoxidized ricinus oil (VI), and epoxidized soybean oil (Drapex 6.8) (VII). As in the former investigations (Papers I and II), the process of the formation of the polyenes occurs in two stages. The concentration of polyene sequences with n double bonds, Hn the total amount of polyene sequences, ∑Hn, the average length of the polyene sequence, n, and the two extents of reaction x and p, were computed. The stabilizing effect of all compounds used agrees with the increasing content of epoxy groups. The addition of stabilizers diminishes the value of n. The decrease of the fraction of long sequences and the increase of short ones occurs. Apart from the binding of evolved HCl, the protective effect towards the macromolecules of PVC consists mainly in the inhibition of growth of chain dehydrochlorination by the epoxy groups.
Differential gel permeation chromatography for quality control
Authors: Runyon J. R.
Published: April 2003

For the direct comparison of similar polymers, as, for example, for quality control, differential gel permeation chromatography provides a simple, sensitive technique that is relatively insensitive to operational variables. One polymer is chosen as a standard and a solution of that polymer is used as the eluent in an otherwise conventional GPC. Differential chromatograms of slightly different polymers are both positive and negative with respect to the baseline. Positive portions represent an excess and negative portions a deficiency as compared to the standard. As in conventional GPC, the elution volumes of the differences indicate the molecular size ranges of the differences. The algebraic sum of the differences is zero. Examination of the raw curves with only general information about calibration and operating conditions tells nearly as much about the differences as carefully executed conventional GPC with complex data reduction.
Rheological properties of mixtures of molten polymer and fluorocarbon blowing agent. I. Mixtures of low‐density polyethylene and fluorocarbon blowing agent
Authors: Han Chang Dae , Ma Chin‐Yuan
Published: April 2003

The viscosities of mixtures of low‐density polyethylene and fluorocarbon blowing agent were determined from the measurement of wall normal stress along the longitudinal axis of a capillary die. For the study, three different grades of commercial high‐pressure low‐density polyethylene were used, together with the following fluorocarbon blowing agents, dichlorodifluoromethane (FC‐12), dichlorotetrafluoroethane (FC‐114), and blends of FC‐12 and FC‐114. In the experiment, blowing agent concentration and melt temperature were varied for each combination of polymer and blowing agent employed. Analysis of the experimental data has led to a correlation between the viscosity reduction factor (VRF) and the blowing agent concentration, in which VRF is defined as the ratio of the viscosity of polymer‐blowing agent mixture to that of the polymer alone. It was found that the correlation obtained is independent of shear rate and temperature and dependent upon only the type of fluorocarbon blowing agent. The practical significance of the correlation is discussed. We have shown that the entrance pressure drop obtained in the absence of phase separation in the entrance region may be used as a measure of the elastic properties of mixtures of fluorocarbon blowing agent and low‐density polyethylene resin.
Morphology of polyurethane modified by plasticizing, blending, or reinforcing
Authors: Blaga A. , Feldman D.
Published: April 2003

The morphology of modified thermoplastic PU has been studied by SEM and DSC. The PU was modified by addition of various amounts of dibutyl phthalate (DBP) plasticizer, vinyl polymers (PVA, PVAc, PVC, VAc–VC copolymer), polysiloxane or fiber reinforcement (glass or cotton) to diolpolyether, followed by mixing and vigorous stirring with dephenylmethane diisocyanate. SEM observations indicated that PU and its modifications have a cellular (foam) structure. A homogeneous matrix was observed in binary blends of PU and DBP in ratios of 20:1 down to 6.6:1; PVA, PVAc, VAc–VC copolymer with a weight ratio of 40:1, PU containing glass fiber (20:1) or cotton fiber (40:1). Blends of PU—with PVA at a weight ratio of 20:1, with PVC in ratios from 20:1 down to 5:1, or with polysiloxane polymer—were heterogeneous and thus not miscible, as evidenced by SEM observations. With the exception of the PU—PSO mixtures, the thermal behavior of the heterogeneous blends did not permit any conclusion regarding miscibility.
Resorbable materials of poly(L‐lactide). II. Fibers spun from solutions of poly(L‐lactide) in good solvents
Authors: Gogolewski S. , Pennings A. J.
Published: April 2003

Fibers of poly(L‐lactide) (PLLA) with a tensile strength up to 1.2 GPa and Young's modulus in the range of 12–15 GPA were obtained by a hot drawing of fibers spun from solution of PLLA in good solvents such as dichloromethane and trichloromethane. The tensile strength of fibers was strongly dependent on the molecular weight of PLLA and on polymer concentrations in the spinning solution. Changing of the polymer concentration in the spinning solution gives rise to formation of fibers with different shape and porosity. Fibers spun from 10–20% solutions at room temperature exhibit a regular structurization, due to the melt fracture. These fibers had knot strengths up to 0.6 GPa, whereas fibers with a smooth surface spun from more dilute solutions had weaker square knots up to 0.3 GPa.
Electron spin resonance measurements of Cu++ distribution in cation exchange membranes
Authors: Vásquez R. , Ávalos J. , Volino F. , Pineri M. , Galland D.
Published: April 2003

Electron spin measurement of the local Cu++ concentrations have been performed in different cation exchange membranes by comparison with reference frozen aqueous solutions of Cu++ salts. Comparison of the obtained values with the average chemical concentrations has therefore permitted direct evidence of microphase separation in these systems. Local concentrations approximately four times larger than average chemical concentrations have been found. Information about composition of this ion‐containing phase has also been obtained from changes in local Cu++ concentrations versus water content.
The time–temperature dependence of the complex modulus of keratin fibers
Authors: Danilatos G. D. , Postle R.
Published: April 2003

The dynamic modulus and loss angle of wet keratin fibers have been measured at frequencies between 6 and 1500 Hz in the temperature range 0.2–45°C. Some further measurements were performed at different relative humidities. These results have been compared with other known results, and the agreement or discrepancies found are discussed. A theoretical curve fit has been introduced for a selected set of experimental results.
A new method of determining the optical properties of cotton fibers using polarizing interference microscopy
Authors: Żurek W. , Zakrzewski S.
Published: April 2003

The refractive indices, birefringence, and cross‐sectional area of cotton fibers was measured using interference polarizing microscope constructed by M. Pluta. A new technique was suggested by realizing the measurements at the perpendicular position of the duplicated image of fiber to the interference fringe. The proposed procedure is a combination of modification of Hamza method and Pluta dual wavelength method, and it was possible to measure at once the three mentioned features of single fiber at one time.
Miscible blends of a vinylidene chloride/vinyl chloride copolymer with aliphatic polyesters
Authors: Woo E. M. , Barlow J. W. , Paul D. R.
Published: April 2003

A copolymer of vinylidene chloride and vinyl chloride containing 13.5% by weight of the latter has been solution blended with four aliphatic polyesters: poly(ϵ‐caprolactone), poly(2,2‐dimethyl‐1,3‐propylene adipate), poly(1,4‐cyclohexanedimethylene succinate), and poly(2,2‐dimethyl‐1,3‐propylene succinate). Each blend was examined visually and by differential scanning calorimetry. All blends with the copolymer form a single miscible amorphous phase at all compositions and all temperatures except for the latter mentioned polyester, which exhibits liquid–liquid phase separation at temperatures above a measured cloud point curve. Information about interactions between the components in each blend is estimated from melting point data and discussed.