bluuebunny/crossref_metadata_2025_split huggingface dataset:
A proposed mechanism for the degradation of addition polymers in cavitating ultrasonic fields
Authors: Doulah M. S. 
Published: April 2003

AbstractA mechanism for the degradation of polymer molecules in ultrasonic cavitation has been proposed which takes into account the energy released by imploding cavitation bubbles in the form of hydrodynamic waves. Relationships for degradation rate constant and limiting chain length linking with the cavitation energy have been derived and are compared with published results on 1% solutions of polystyrene in benzene. These results show satisfactory agreements with the theory presented when the cavitation wave energy is taken proportional to the energy supplied to the ultrasound generating transducer.
The chemistry and development of tannin‐based adhesives for exterior plywood
Authors: Pizzi A. , Scharfetter H. O. 
Published: April 2003

AbstractCondensed tannins are phenolic in nature and undergo reaction with formaldehyde to form resins. Tannin/formaldehyde condensates tend to have a low degree of condensation resulting in bonds lacking strength and water resistance. Small amounts of short‐length phenol/resorcinol/formaldehyde, phenol/formaldehyde, and urea/formaldehyde polymers are used to increase the degree of polymerization of tannin‐formaldehyde resins, decreasing brittleness and increasing water resistance. Furfural is used to plasticize tannin/formaldehyde resins to improve the distribution of stress forces on the glueline, overcoming weakness due to stress concentration. Exterior plywood panels were prepared using these modified tannin/formaldehyde resins as adhesives. The modified tannin/formaldehyde adhesives perform well, have similar characteristics to and are as easy to use as phenol/formaldehyde adhesives, and also have a few advantages, especially tolerance to faster pressing times.
The effect of polar groups on the dielectric loss of polyethylene
Authors: Sato Yukihiko , Yashiro Takamasa 
Published: April 2003

AbstractThe dielectric loss tangent for polyethylene with low dielectric loss was approximated by tan δ = Cf Σ(nμ2), where n and μ are the number and dipole moment of polar groups, respectively, and Cf is a parameter. The type and number of polar groups in the polyethylenes were mainly determined from infrared spectra obtained with a Fourier transform spectrometer. It was found that the contribution of hydroxyl and carbonyl groups to tan δ was significantly large, but the contribution of double bond groups was less significant. The tan δ was observed to decrease with a decrease of methyl group density although the overall contribution of methyl groups to tan δ was small. This suggests that tan δ is closely related to the secondary structure of polyethylenes, thus indicating the methyl groups seem to play an important role in the secondary structure.
A free‐volume interpretation of the influence of the glass transition on diffusion in amorphous polymers
Authors: Vrentas J. S. , Duda J. L. 
Published: April 2003

AbstractA new version of the free‐volume theory of diffusion is used to describe polymer–solvent diffusion both above and below the glass transition temperature. Expressions are derived for the temperature dependence of the mutual diffusion coefficient and for the effective activation energy in the limit of zero penetrant concentration. The theory also describes the effect of the glass transition on the diffusion process. Predictions of the theory are compared with available diffusivity data for amorphous polymer–solvent systems.
Temperature dependence of critical fiber length for glass fiber‐reinforced thermosetting resins
Authors: Ohsawa Tadashi , Nakayama Akira , Miwa Minoru , Hasegawa Akira 
Published: April 2003

AbstractIn discontinuous fiber‐reinforced composites, the critical fiber length plays an essential role in determining the mechanical properties. A method was devised to accurately determine the critical fiber length and the temperature dependence of the critical fiber length was studied for glass fiberepoxy and glass fiber‐unsaturated polyester resin composites. If a continuous glass fiber is embedded in the matrix and the system is subjected to a tensile strain greater than the fiber ultimate tensile strain, the fiber breaks into many pieces. If the average length of these broken pieces (l̄) is measured, the critical fiber length (lc) is expressed as lc = 4/3l̄. The critical fiber length greatly increases with increasing temperature and the apparent shear strength at the interface, calculated from the critical fiber length, decreases linearly with increasing temperature.
Graft copolymerization of 2‐methyl‐5‐vinyl pyridine to poly(ethylene terephthalate) fibres using a post‐radiation technique
Authors: Hebeish A. , Shalaby S. E. , Bayazeed A. M. 
Published: April 2003

AbstractRadiation‐induced grafting of 2‐methyl‐5‐vinyl pyridine (MVP) to poly(ethylene terephthalate) fibers (PET) was investigated under a variety of conditions employing a post‐radiation technique. Over a range of a total dose of 1–10 Mrad, increasing the total dose from 1 up to 3 Mrad was accompanied by a significant enhancement in the extent and rate of grafting. Further increase in the total dose caused a decrease. The same situation was encountered with respect to MVP concentration (5%–10%) and polymerization temperature (75°–90°C). A MVP concentration of 8% and a temperature of 85°C constituted the optimal. Addition of copper sulfate at a concentration of 0.05 mmole/l. offset grafting. The effect of the said parameters on homopolymerization occurring during grafting was also investigated.
Physicochemical properties of kevlar 49 fiber
Authors: Penn Lynn , Larsen Fred 
Published: April 2003

AbstractThe high‐strength, high‐modulus Kevlar 49 fiber is widely used today because of its superior properties. In this paper, we discuss the fundamental physicochemical nature of the commercial fiber. It is an extended chain polymer, poly(p‐phenylene terephthalamide), which is highly crystalline. Extensive analysis shows that the material composition is quite consistent from lot to lot and is low in impurities. The fiber absorbs water reversibly; the extent of absorption is related to the ash content. The well‐known interaction of the fiber with ultraviolet light is illustrated with spectra, and the thermal stability of the fiber is demonstrated with various thermal analysis techniques.
Applicability of the two‐dimensional approach to polymer miscibility in pure and mixed organic liquids
Authors: Chen Show‐An , Lai Wen‐Jen 
Published: April 2003

AbstractPreviously it was proposed that the solvent power of a pure or mixed organic liquid for a given polymer can be characterized by two parameters δh and χH. Using these two parameters, a two‐dimensional (2D) solubility diagram can be constructed to predict solubility or insolubility. In the investigation only the polymers, poly(methyl methacrylate), polystyrene, and poly(vinyl acetate), were used to demonstrate the applicability of the 2D method. In this note, applicability of the 2D method to the 33 polymers investigated in Hansen's works is presented.
Radiation‐Induced graft copolymerization of methyl methacrylate on natural and modified wool. II. Sorption behavior
Authors: Varma D. S. , Sadhir R. K. 
Published: April 2003

AbstractThe water vapor sorption‐desorption isotherms of graft copolymers of methyl methacrylate with natural and chemically modified wool (i.e., oxidized, reduced, methylated, and crosslinked) has been investigated. As a result of graft copolymerization a reduction in water absorption was observed. The results have also been analysed in the light of Hailwood–Horrobin equations.
Effect of short thermal treatment on cotton degradation
Authors: Hebeish A. , El‐Aref A. T. , El‐Alfi E. A. , El‐Rafie M. H. 
Published: April 2003

AbstractCotton fabric was subjected to thermal treatment for durations ranging from 0.5 to 5 min at a temperature range of 160°C. In comparison with the untreated cotton, the copper number (measure of the aldehyde content) decreased after heating cotton for up to 3 min at 160°, 180°, and 190°C but increased when heating was prolonged to 5 min. Thermal treatment at 200°C or above caused an appreciable increase in the copper number. The carboxyl content increased with time of heating, attained a maximum, and then fell down to reach values which in some cases were lower than that of untreated cotton. Thermal treatment at 180°C caused a substantial reduction in the D. P.; this reduction increased with time of treatment. At the other temperatures there was no significant decrease in D. P. when cotton was heated up to 3 min. The D. P. decreased in these cases only when the thermal treatment was conducted for 5 min. The tensile strength remained practically unimpaired after thermal treatment of the cotton for up to 2 min, regardless of the temperature used within the range studied. A loss in tensile strength of ca. 9% and 13% was observed with fabrics treated for 5 min at 160° and 180°C, respectively. This contrasts with a loss of ca. 4% at 190°C, 7% at 200°C, and 8% at 220°C. The highest dye exhaustion was obtained on cotton which was thermally treated at 180°C prior to dyeing, while the lowest dye exhaustion was obtained on cotton heated at 220°C. Thermal treatment at 160°C left the susceptibility of cotton toward the dyestuff practically unaltered.
The dielectric behavior of natural resin shellac
Authors: Goswami Dipendra Nath 
Published: April 2003

AbstractThe Cole‐Cole method has been applied for an analysis of the dielectric relaxation data of the natural resin shellac, obtained by Bhattacharya in the temperature range 20–110°C. Three relaxation processes were observed for temperatures 20–60°C. At 70°C, two relaxation processes were noticed, whereas only one was observed by Bhattacharya between 20 and 110°C. The relaxations at 80°C and above represented typical Cole‐Cole type. The variation of the static dielectric constant with temperature revealed three distinct slopes, which indicated different phases of the resin during its thermal transition from solid to liquid state. Two “transformation points,” around 40 and 70°C were noted, i.e., the glass transition temperature and melting point of the resin, respectively. Significant changes in static dielectric constant, dielectric increment, relaxation time, and Cole‐Cole distribution parameter were observed during a rise of temperature from 80 to 110°C. The results of the present study indicate that some rearrangement in the teriary disposition of the resin molecules takes place during the rise of temperature from 20 to 110°C.
Removal of trace quantities of nickel from solution
Authors: Randall J. M. , Randall V. G. , McDonald G. M. , Young R. N. , Masri M. S. 
Published: April 2003

AbstractChitosan, which is produced from the natural polymer chitin, is a much more efficient scavenger of nickel ion than other natural ion exchange materials tested. An industrial waste containing about 7 ppm Ni2+ and 10,000 ppm Na+ was reduced to less than 0.1 ppm Ni2+ by contact in a packed column of chitosan. Capacity of the chitosan substrate under these conditions was a little more than 1 meq/g. The substrate can be regenerated by contact with buffered NH4Cl at pH 10. The high sodium content of the nickel waste did not prevent sorption of Ni2+, but it apparently produced an interference with atomic absorption spectrophotometer analyses, giving a spurious reading of 0.8 ppm Ni2+ when the major nickel line at 232 nm was used for analysis.
Gel permeation chromatography in the study of the molecular weight distribution vinyl chloride–vinyl acetate copolymer. III. Influence of the incompatibility of polymers and some problems of interpretation of experimental data
Authors: Janča J. , Pokorný S. , Kolínský M. 
Published: April 2003

AbstractThe influence of incompatibility in the ternary systems gel–polymer–solvent and polymer–polymer–solvent on the results of gel permeation chromatography of the copolymer vinyl chloride–vinyl acetate was investigated. The measurements were performed on styrene–divinylbenzene gels and on porous silica gels. Detection in GPC was made using a differential refractometer together with a UV detector, which permitted evaluation of the extent of interactions of the polymer components in the mixture. Some aspects of the GPC data are discussed for the application of universal calibration, the validity of which for the copolymer vinyl chloride–vinyl acetate has been proved.
Controlled release of drugs from hydrogel matrices
Authors: Hosaka Shuntaro , Ozawa Hitoshi , Tanzawa Hiroshi 
Published: April 2003

AbstractA series of polymers with wide ranges of water absorptivity were prepared and utilized as matrices for the controlled release of drugs. The drugs were introduced into the matrices by use of an appropriate organic solvent. Release rates of erythromycin and erythromycin estolate from hydrogel were analyzed kinetically and found to conform to Higuchi's equation, that is, Mt = A(2DtCsC0)1/2, where Mt is the accumulated amount of released drug at time t, A is the surface area, D is the diffusion coefficient, Cs is the solubility of drug in the hydrogel matrix, and Co is the initial drug content of the preparation in the swollen state. The relationship between the water content of hydrogel and the diffusion coefficient of erythromycin in hydrogel is expressed by the equation D = 3.03 × 10−10 W3.03 (cm2/sec), where W is the water content (%). The release rate of drug can be controlled quantitatively by adjustment of the water content of the hydrogel matrix. A guide to the design for the preparation is suggested.
The radiation‐induced emulsion copolymerization of vinyl chloride with vinyl acetate in an engineering flow system
Authors: Tsai J. T. , Stahel E. P. , Stannett V. T. 
Published: April 2003

AbstractA flow reactor system was used to study the radiation‐induced emulsion copolymerization of vinyl chloride with vinyl acetate. The emulsion was recirculated from a stirred vessel through transfer lines to a tubular reactor located within a high‐intensity Co‐60 source. The effects of physical chemical variables such as soap concentration, phase ratio, reaction temperature and residence time distribution on the molecular weight properties were investigated. The rate of copolymerization was found to be proportional to the 0.17 power of the soap concentration. Variation of the monomer‐water ratio produced no significant change in rate. The rate increased with an increase in temperature over the range 5–50°C, while the average molecular weights of the copolymer increased with decreasing polymerization temperature. The molecular weight distribution in this engineering system was found to be essentially similar to those produced in a batch system.
New acetylene‐terminated phenylquinoxaline oligomers
Authors: Hedberg F. L. , Arnold F. E. 
Published: April 2003

AbstractA series of new acetylene‐terminated phenylquinoxaline oligomers and diacetylene compounds have been prepared utilizing 4‐(3‐ethynylphenoxy)benzil. The amorphous materials with molecular weights from 500 to 1460 exhibited softening in the 25–160°C range with a strong polymerization exotherm reaching a maximum at 270–290°C. The addition nonvolatile cure provides materials which show excellent thermoxidative stability and processability for high‐temperature matrix and adhesive resins.
Temperature dependence of the brittleness of cellulose fibers and of chemically modified cellulose fibers
Authors: Zeronian S. H. , Ellison M. S. 
Published: April 2003

AbstractThe temperature dependence of the brittleness of cellulose fibers was studied by the breaking twist angle method. The selected fibers were purified ramie cells, the same cells after fibrous acetylation to form the triacetate, annealed acetylated ramie cells, and mercerized ramie cells. Water acts as a plasticizer to reduce the brittleness of ramie and of mercerized ramie cells but does not appear to affect the brittleness of ramie cells after acetylation. The brittleness of ramie cells is reduced by similar amounts by fibrous acetylation and by mercerization. The brittleness of acetylated ramie cells is increased by annealing, which induces additional crystallization in the cells. The brittleness of ramie and acetylated ramie before and after annealing varied as the test temperature was progressively increased in the range 100–200°C. The effect of temperature on the brittleness of the fibers is interpreted in terms of the relaxation transitions previously determined on the same types of fibers, and in terms of the supramolecular structure of the fibers.
Influence of the ratio of styrene and acrylonitrile in crosslinked polymeric binders for use in high‐temperature polymer concrete composites
Authors: Zeldin A. , Kukacka L. E. , Carciello N. 
Published: April 2003

AbstractThe feasibility of using a monomer composition based on a styrene–acrylonitrile copolymer as a binder in high‐strength and chemically resistant polymer concrete was demonstrated earlier. From this work it is clear that properties of the polymer concrete composite are dependent on the styrene/acrylonitrile ratio. This paper deals with the study of the effect of the styrene/acrylonitrile ratio in styrene–acrylonitrile–acrylamide–trimethylolpropane trimethacrylate monomer formulations on the thermomechanical properties of polymer concrete composites.
Polyether‐based thermoplastic polyurethanes. I. Effect of the hard‐segment content
Authors: Zdrahala R. J. , Gerkin R. M. , Hager S. L. , Critchfield F. E. 
Published: April 2003

AbstractA series of Polyether‐based thermoplastic polyurethanes, varying in hard‐segment content between 20 and 80 wt. %, was prepared using an (oxypropylene‐oxyethylene) diol of Mn = 2000 as the soft segment and 4,4′‐diphenylmethane diisocyanate extended with 1,4‐butanediol as the hard segment. Physical‐mechanical, dynamic‐mechanical, and specific heat (DSC) data are used to elucidate the mechanical and morphological behavior of these materials. The polyurethanes varied from soft elastomeric (continuous soft phase) to high‐modulus plastic (continuous hard phase) and showed changes in their tensile properties at about 60% hard‐segment content, possibly due to phase inversion.
Polymer effect in electrochromic behavior of oligomeric viologens
Authors: Sato Hirotsugu , Tamamura Toshiaki 
Published: April 2003

AbstractA series of oligomeric viologens were synthesized in order to investigate the polymer effect in electrochromic behavior of viologen compounds. These materials have a lower first‐step reduction potential and a higher second‐step reduction potential compared with monomeric viologens. As a result, they have wider potential separation, where stable viologene radical salts are produced. Spectroscopic analysis suggests that stable monomeric viologen radical salts do not exist in water, but there is some intramolecular interaction between viologen radicals of the oligomers. This intramolecular interaction is responsible for the reduction behavior and the stability of radical films of oligomeric viologens.
Surface modification of polyethylene by radiation‐induced grafting for adhesive bonding. V. Comparison with other surface treatments
Authors: Yamakawa Shinzo , Yamamoto Fumio 
Published: April 2003

AbstractHelium gas plasma treatment of low‐density polyethylene (LDPE) yields much lower peel strength than oxidative treatment using chromic acid and oxygen gas plasma. The practical adhesion, the bondability retention, and the bond durability of oxidatively treated LDPE sheets, bonded with epoxy adhesives, have been compared with those of partially hydrolyzed LDPE–methyl acrylate surface grafts. The oxidized surfaces easily lose the bondability by light rubbing with tissue paper, solvent extraction, heat aging, and artifical weathering, whereas the grafted surfaces retain the bondability. The bondability loss is due to removal of the oxidized layer, and the bondability retention is due to retention of the surface homopolymer layer. Conventional antioxidants stabilize the grafted but not the oxidized surfaces against thermal oxidative degradation. The grafted LDPE joints have much higher bond durability in humid environments than those of the oxidized LDPE joints. The dry and wet peel strengths of oxidized LDPE joints are greatly improved by application of primers consisting of a base epoxy resin and organic solvents. An adhesion mechanism involving penetration of epoxy adhesives into the oxidized layers and subsequent reinforcement of the layers by curing of the penetrated epoxy is proposed.
Reinforcement of acrylonitrile copolymer by polymer blending
Authors: Lawton E. L. , Murayama T. , Holland V. F. , Felty D. C. 
Published: April 2003

AbstractBlends of an acrylonitrile copolymer and a reinforcing polymer were formed by polymerization of the second component in a concentrated solution of the first component. The second component, polyureas or polycarbodiimides, precipitated as an intimate dispersion of particulate domains in the liquid medium. Film or fiber formation by coagulation of the solution containing the second component as particulate matter resulted in a distinct two‐phase blend. Reinforcement of the acrylonitrile copolymer was evidenced by significant increases in dry and wet moduli above the glass transition temperature of the polyacrylic component. The blends were characterized with dynamic mechanical testing and optical and electron microscopy. The blends exhibited two glass transitions corresponding to those of the individual components. The phase domains were evident over the compositional range examined. The method of blending is illustrative of effective reinforcement by interpenetration of phases in the absence of compatibility of the components at the macromolecular level.
Experimental investigations of the influence of molecular weight distribution on melt spinning and extrudate swell characteristics of polypropylene
Authors: Minoshima Wataru , White James L. , Spruiell Joseph E. 
Published: April 2003

AbstractAn experimental study of the influence of molecular weight distribution on the melt spinning and extrudate swell of a series of polypropylenes of varying molecular weight and distribution is reported. Emphasis is given to effects of variations of molecular weight distribution. Narrowing the molecular distribution increases the slope of the elongational viscosity–elongation rate curve, stabilizes the spinline relative to both random disturbances and draw resonance, and decreases both instantaneous and delayed extrudate swell. These results are interpreted in terms of viscoelastic fluid mechanics and earlier experimental studies by the authors of the influence of molecular weight distribution on rheological properties. The influences of these rheological factors on spinline structure development is discussed.