bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrostatic properties of UV‐irradiated and surface‐grafted polymers
Authors: Uyama Yoshikimi , Ikada Yoshito 
Published: April 2003

AbstractA polystyrene film, a poly(ethylene terephthalate) (PET) film, and PET fabrics were UV‐irradiated or surface‐grafted with various hydrophilic monomers. Their electrostatic properties were studied by measuring the triboelectric charges generated upon mechanical rubbing of these materials and by following the decay of the charges generated upon exposing the polymeric materials to a high electric field. The UV‐irradiated polymers carried lower electrostatic charges than those unirradiated after their surfaces were rubbed with a cotton fabrics under the same conditions. The generation of triboelectric charge depends on both the surface hydrophilicity and the past history of the specimens. Although hydrophilic groups introduced on the polymer surface by UV exposure exhibited little effect on decaying of the electrostatic charge, polymeric materials grafted with a large amount of water‐soluble polymers, especially with ionic polymers, showed lower triboelectric generation and faster decay of the static charge.
Glass transition temperatures of poly(methyl vinyl ether‐co‐maleic anhydride) (PMVEMA) and poly(methyl vinyl ether‐co‐maleic acid) (PMVEMAC) and the kinetics of dehydration of PMVEMAC by thermal analysis
Authors: Chung K. H. , Wu C. S. , Malawer E. G. 
Published: April 2003

AbstractThree distinct peaks at 80, 175, and 325°C were identified in the dynamic derivative TGA curves of PMVEMA and PMVEMAC at a 10°C/min heating rate. These peaks were attributed to free water removal, anhydride formation, and polymer degradation, respectively. The kinetics of the anhydride formation were studied by isothermal TGA in the temperature range of 150–200°C. It was found to be an endothermic and first‐order intramolecular reaction with an activation energy of 18.8 kcal/mol. It was concluded from FT‐IR and DSC results that no intermolecular anhydride structure was present in the dehydration of PMVEMAC. This is different from the cases of the dehydration of poly(acrylic acid) and poly(methacrylic acid) in the literature. The limiting glass transition temperatures of PMVEMA and PMVEMAC were found to be 153 and 144°C, respectively. The higher glass transition temperature in PMVEMA as compared to PMVEMAC is attributed to the increase in stiffness in the main polymer chain by the five‐membered ring anhydride structure in PMVEMA.
The equation of state of a polydimethylsiloxane fluid
Authors: Fakhreddine Y. A. , Zoller P. 
Published: April 2003

AbstractExperimental data for the dependence of the specific volume on temperature and pressure (PVT data) of a polydimethylsiloxane fluid with 100 cS viscosity are presented. The temperature range covered is 30–344°C and the pressure range is 0–200 MPa (0–29,000 psi). Coefficients for an empirical equation of state are reported. This equation of state is based on a polynomial fit to the zero‐pressure isobar, combined with the Tait equation. The maximum deviation in specific volume between the data and the fitted empirical equation of state is less than 0.006 cm3/g, or less than 0.05% of the volume, except at the highest temperature, where sample degradation is likely to occur. The isothermal compressibility and thermal expansivity are derived from the empirical equation of state, and both show a strong temperature and pressure dependence. Reducing parameters for the Simha–Somcynsky theoretical equation of state were found to be P* = 502 MPa, V* = 0.9765 cm3/g, and T* = 8175 K. A comparison between theory and experimental data at temperatures to 245°C (recommended upper use temperature) revealed volume deviations comparable to those obtained using the Tait equation.
Surface modification by continuous graft copolymerization. III. Photoinitiated graft copolymerization onto poly(ethylene terephthalate) fiber surface
Authors: Yao Zhang Pei , Rånby Bengt 
Published: April 2003

AbstractPhotoinitiated grafting is an excellent method to modify the surface properties of a polymer. The presoaking photografting method applied to poly(ethylene terephthalate) (PET) with acrylic acid or acrylamide as monomer using benzophenone as photoinitiator has been investigated. The photografting proceeds under nitrogen atmosphere in a continuous process. The relative intensity of the ESCA lines of nitrogen over carbon of the fiber grafted with acrylamide increased from 3–4% (background) to 8% for 20‐s irradiation time. Measured by titration, the amount of grafted poly(acrylic acid) is 0.821 and 1.528 mg/m2 with 0.5 M and 2.0 M acrylic acid concentration, respectively, in the presoaking solution at 10‐s irradiation time. The dyeability of the fiber, measured by UV absorption, improved. The concentration of initiator and monomer and the solvent used affected the grafting yield. Appropriate conditions promoted photografting of the poly(ethylene terephthalate) fiber. Acetone was a somewhat better solvent than methylethylketone and methylpropylketone.
The glass transition temperature (tg) as a parameter for monitoring the cure of an amine/epoxy system at constant heating rates
Authors: Wisanrakkit G. , Gillham J. K. , Enns J. B. 
Published: April 2003

AbstractA continuous heating transformation (CHT) cure diagram displays the time and temperature of events that a material encounters during the course of continuous heating at different heating rates. For thermosetting systems, these events include gelation, vitrification, and devitrification. Analysis of isothermal data for a diglycidyl‐type epoxy/tetrafunctional aliphatic amine system, which is initially liquid at room temperature, indicated that kinetic control applied prior to vitrification; i.e., for Tg<Tcure (temperature of reaction). The parameters so obtained (i.e., order of reaction, Arrhenius pre‐exponential term, and activation energy) together with an experimental relationship between Tg and extent of reaction were used as a basis for modeling the onset of vitrification and devitrification in the CHT diagram. For heating scans from below Tgo (glass transition temperature of the reactants), initial devitrification occurs when Tcure first passes through the Tg of the initial reacting material, except for very low heating rates for which inital devitrification is not encountered. Vitrification is identified as the point at which Tg becomes equal to the increasing curing temperature. Diffusion control retards the reaction rate beyond vitrification. In the limiting case of complete retardation of the rate after vitrification, the reaction can proceed along the Tg = Tcure path as long as the additional reaction with increasing temperature is sufficient to increase Tg at least at the same rate as the heating temperature; devitrification occurs thereafter. The critical heating rates at which the material does not devitrify in the vicinity of Tgo, and that at which no vitrification is encountered, are calculated.
Study of particle morphology in polymer emulsions and their minimum film formation temperatures
Authors: Tongyu Cao , Yongshen Xu , Yuncheng Su , Fu Long , Xing Li , Yuhong Hu 
Published: April 2003

AbstractIn the present paper, the emulsion polymerization of methyl methacrylate–butyl acrylate and styrene–ethyl acrylate were carried out. Polymer emulsions with latex particles of different morphology were prepared. The relationship between the minimum film formation temperature of the polymer latexes and the morphology of the latex particles were studied, and the film‐forming mechanism of the polymer latexes with varied particle morphology was also discussed.
Deformation behavior of Kevlar fibers studied by Raman spectroscopy
Authors: Prasad Keshav , Grubb David T. 
Published: April 2003

AbstractThe tensile deformation of Kevlar fibers has been studied using Raman spectroscopy. The Raman bands shifted to lower wavenumbers and broadened with stress. The shift of the 1610 cm−1 Raman band per unit stress was about −2.5 cm−1/GPa in both Kevlar 29 and Kevlar 49. A simple one phase paracrystalline model is used to explain the observed shifts. The total increase in the width of the 1610 cm−1 Raman band was about 2.5 cm−1 and the increase in width was negligible till a stress of about 0.5 GPa.
Functionalization of polyethylenes and their use in reactive blending
Authors: Liu N. C. , Baker W. E. , Russell K. E. 
Published: April 2003

AbstractThe grafting of maleic anhydride (MAn) to low density polyethylenes (PEs) dissolved in 1,2‐dichlorobenzene (DCB) has been studied. Grafting was successful at temperatures of about 160°C both in air without initiator and under nitrogen with the radical initiator 2,5‐di(t‐butylperoxy)‐2,5‐dimethyl‐3‐hexyne (LPO). The presence of succinic anhydride grafts was shown by FTIR spectroscopy of the product; 1H‐NMR spectroscopy indicates that the grafts consist of single succinic anhydride units. The graft content was determined by nonaqueous titration, and the extent of crosslinking inferred from the melt flow rates (MFR) of the products. The effects of concentration of initiator, MAn, and PE on the graft content were determined; the influence of PE structure, reaction time, and temperature was also studied. Melt blending of the grafted PE with polystyrene containing oxazoline functional groups (OPS) was investigated using a Rheomix mixer. The interpolymer reaction which occurs during blending was studied by means of FTIR, and the morphology of the blends by scanning electron microscopy (SEM). Information was also gained from the change in torque viscosity during the blending process.
Dimensionless groups for the description of sorption equilibria in dyeing with anionic dyes. I. Inorganic co‐ion exclusion
Authors: Mcgregor Ralph , Iijima Toshiro 
Published: April 2003

AbstractThe equations of a general Donnan Model have been simplified and used to describe the equilibrium sorption of anionic dyes by fibers containing acidic and basic groups. By examining simple situations, the dependence of the sorption behavior on specific dimensionless groups of variables has been clarified. This approach emphasizes common features of different ionic dyeing systems, it can be applied in graphical methods of data analysis, and it has potential applications in process control.
The glass transition temperature (Tg) as an index of chemical conversion for a high‐Tg amine/epoxy system: Chemical and diffusion‐controlled reaction kinetics
Authors: Wisanrakkit G. , Gillham J. K. 
Published: April 2003

AbstractThe glass transition temperature (Tg) is used as a parameter to monitor the isothermal cure of a tetrafunctional aromatic diamine and a difunctional aromatic epoxy system. There is a one‐to‐one relationship between Tg and conversion that is independent of cure temperature, Tcure. Prior to vitrification (Tg = Tcure), the reaction is only kinetically controlled; after vitrification, the reaction becomes diffusion‐controlled. Time‐temperature shifts of Tg vs. In (time) data at different cure temperatures to form a master curve for the kinetically controlled reaction at an arbitrary reference temperature yield a single Arrhenius activation energy (15.2 kcal/mole). The master curve and the reaction activation energy are used in calculating iso‐Tg contours prior to vitrification and also the vitrification contour in the time‐temperature‐transformation (TTT) isothermal cure diagram for the system. The chemical kinetics of the reaction is satisfactorily described by an autocatalyzed reaction mechanism. The overall rate constant of the reaction in both kinetically and diffusion‐controlled regimes is modeled by a combination, in parallel, of the chemical rate constant and the diffusion rate constant. The chemical rate constant has the usual Arrhenius form, whereas the diffusion rate constant is assumed to be given by a modified form of the WLF equation. Results suggest that both primary and secondary amino hydrogens are equally reactive. A theoretical model for calculating Tg as a function of conversion is presented for a network‐forming system with one bond‐forming reaction.
Radiopaque polymers based on acrylated phosphonate esters derived from polyols
Authors: Cabasso Israel , Smid Johannes , Sahni Suresh K. 
Published: April 2003

AbstractA number of miscible metal salt–polymer systems of acrylated phosphonates derived from various polyols such as glycerol, D‐mannitol, D‐sorbitol, pentaerythritol, and dipentaerythritol are described. The salt–monomer systems could be polymerized radically to form homogeneous transparent glassy polymers. Incorporation of heavy metal salts in polymers imparts radiopacity on otherwise radiolucent materials rendering them useful for X‐ray imaging. The polymer–salt systems have been characterized with the aid of infrared spectroscopy and thermal and radiographic analyses. In these salt–polymer systems, salts are bonded to the polymers predominantly through the phosphoryl's oxygen. The results indicate that about 11 wt % of uranyl nitrate hexahydrate and 12.5 wt % of bismuth bromide impart a radiopacity equivalent to that of aluminum. The glass transition temperatures (Tg) of the salt‐containing polymers are substantially higher than the salt‐free polymers. TheTgvalues seem to depend on the chemical nature of the polymers, concentration of metal salts, and the extent of crosslinking induced through chelation. The analysis indicated complete solubility in the polymer matrices. No melting point endotherms of free salt crystals were detected. Some preliminary adhesion measurements revealed that acrylated phosphonates are excellent adhesion promoters for hard tissues.
Protease immobilization onto porous chitosan beads
Authors: Hayashi Toshio , Ikada Yoshito 
Published: April 2003

AbstractWater‐insoluble proteases were prepared by immobilizing papain, ficin, and bromelain onto the surface of porous chitosan beads with any length of spacer by covalently fixation. The activity of the immobilized proteases was found to be still high toward small ester substrate, N‐benzyl‐L‐arginine ethyl ester (BAEE), but rather low toward casein, a high‐molecular‐weight substrate. The relative activity of the immobilized proteases with spacer gave an almost constant value for the substrate hydrolysis within the surface concentration region studied. The values of the Michaelis constant Km and the maximum reaction velocity Vm for free and immobilized proteases on the porous chitosan beads are estimated. The apparent Km values were larger for immobilized proteases than for the free ones, while Vm values were smaller for the immobilized proteases. The pH, thermal, and storage stability of the immobilized proteases were higher than those of the free ones. The initial enzymatic activity of the immobilized protease maintained almost unchanged without any elimination and inactivation of proteases, when the batch enzyme reaction was performed repeatedly, indicating the excellent durability.
Chemical modification of poly(substituted‐acetylene). V. Alkylsilylation of poly(1‐trimethylsilyl‐1‐propyne) and improved liquid separating property at pervaporation
Authors: Nagase Yu , Takamura Yuriko , Matsui Kiyohide 
Published: April 2003

AbstractIn order to improve the separation characteristic at pervaporation, the introduction of several kinds of trialkylsilyl groups into poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) was achieved via metalation of PTMSP followed by treating with trialkylchlorosilanes to afford trialkylsilylated PTMSP. Ratio of TMSP monomer unit and trialkylsilylated unit, x/y, was in the range of 95/5 to 80/20. All the chemically modified PTMSP membranes showed ethanol permselectivity at pervaporation of aqueous ethanol solution. Introduction of appropriate length of alkyl groups (methyl, ethyl, propyl, butyl, hexyl, octyl, and decyl groups) into PTMSP effectively enhanced the selectivity. However, excess introduction of octyl and decyl groups or introduction of dodecyl and octadecyl groups caused decrease of selectivity, of which the value was smaller than that of PTMSP membrane. Furthermore, acetone, acetonitrile, dioxane, and isopropanol were efficiently separated from their aqueous solutions at pervaporation through trimethylsilylated PTMSP membrane.
Fracture toughness of particle filled fiber reinforced polyester composites
Authors: Dharmarajan N. , Vipulanandan C. 
Published: April 2003

AbstractFracture behavior of polyester composite systems, polyester mortar and glass fiber reinforced polyester mortar, was investigated in mode I fracture using single edge notched beams with varying notch depth. The beams were loaded in four‐point bending. Influence of polymer content on the flexural and fracture behavior of polyester composites at room temperature was studied using a uniform Ottawa 20–30 sand. The polymer content was varied between 10 and 18% of the total weight of the composite. The flexural strength of the polyester mortar systems increase with increase in polymer content while the flexural modulus goes through a maximum. The critical stress intensity factor (KIC) for the optimum polyester mortar (14%) was determined by two methods including a method based on crack mouth opening displacement. TheKICfor polyester mortar is linearly related to the flexural strength. Polyester mortar (18%) reinforced with 4% glass fibers was also investigated, and crack growth resistance curve (KR) was developed with crack extension (Δa). A model has been proposed to represent the fracture toughness with change in crack length,KR‐ Δarelationship, of fiber reinforced polyester composite.
Kinetic model for short‐cycle bulk styrene polymerization through bifunctional initiators
Authors: Villalobos M. A. , Hamielec A. E. , Wood P. E. 
Published: April 2003

AbstractA model describing the kinetics of bulk styrene polymerization through bifunctional initiators has been developed. The diffusion‐controlled propagation and termination reactions at high monomer conversions are modeled with the free volume theory for polymer solutions. Three different commercially available bifunctional initiators were experimentally evaluated for a wide range of polymerization conditions to study the effect of the reaction rate on the molecular weight and molecular weight distribution. The model predictions for the same polymerization conditions show excellent agreement with the experimental data, for the whole range of conversions, for both reaction rate and molecular weight distribution development, under all the conditions tested. It is demonstrated throughout this study that high molecular weights, very high reaction rates, and narrow molecular weight distributions can be achieved simultaneously by using bifunctional initiators. A comparison between monofunctionally initiated systems with the bifunctionally initiated ones shows that short‐cycle reactions with reductions in polymerization time of up to 75% may be achieved with the bifunctional initiators for a wider range of conditions without significantly affecting the molecular weight and molecular weight distribution of the final product.
New method for the preparation of thick conducting polymer composites
Authors: Ruckenstein Eli , Park Jun Seo 
Published: April 2003

AbstractA highly porous and absorbable crosslinked polystyrene, prepared by the concentrated emulsion polymerization method, was used as host polymer for the preparation of conducting, large objects, polymer composites. The composites, whose conductivity can be as high as 0.80 S/cm, were prepared by (i) imbibing the host polymer with a pyrrole (or oxidant) solution, (ii) partially drying the imbibed host polymer, and (iii) imbibing again with an oxidant (or pyrrole) solution for polymerization to take place. The electrical conductivity of the composite and the penetration of polypyrrole in the host polymer are influenced by the polymerization conditions (i.e., the concentrations of oxidant and pyrrole and the nature of the solvents used for the oxidant and pyrrole), the order in which the two imbibing solutions are introduced, and the drying time used after the first imbibation. The mechanical properties of the host polymer are improved with the incorporation of polypyrrole. Scanning electron micrographs of the composites indicate that the polypyrrole coats uniformly as a film the inside of the porous host polymer.
Thermal, mechanical, and fracture properties of copolyureas formed by reaction injection molding: Effects of hard segment structure
Authors: Ryan Anthony J. , Bergstromcu Todd B. , Willkomm Wayne R. , Macosko Christopher W. 
Published: April 2003

AbstractA series of copolyureas containing 50% by weight hard segment have been formed by RIM. The hard segment structure was systematically varied to investigate the effects of urea group density, hard segment crosslinking, relative reaction rates, and to compare the properties of aromatic and aliphatic hard segment materials. In each case the soft segment was based on a 2000 molecular weight polyether diamine. The RIM materials formed ranged from flexible elastomers to brittle plastics depending on composition and were characterized by SAXS, DSC, DMA, tensile stress–strain and fracture mechanics studies. SAXS, DSC, and DMA showed that microphase separation had occurred to give materials with a non‐equilibrium morphology. DMA and tensile stress–strain studies showed the small strain properties to be very sensitive to the volume fraction of glassy material whereas the ultimate properties were dependent on chemical structure of the hard segment. Fracture properties were determined using the single‐edge notch technique. In most cases ductile failure occurred with Gc > 2.5 kJ m−2 and the fracture surfaces showed gross yielding and tearing. In the case of the copolyurea with the highest urea group content, brittle fracture occurred with Gc = 0.06 kJ m−2.
Styrene–butadiene rubber/lead oxide composites as gamma radiation shields
Authors: Abdel‐Aziz M. M. , Badran A. S. , Abdel‐Hakem A. A. , Helaly F. M. , Moustafa A. B. 
Published: April 2003

AbstractComposites of styrene–butadiene rubber were prepared with three different types of lead oxide, namely, monolead oxide (PbO), lead dioxide (PbO2), and red lead oxide (Pb3O4). Concentrations of Pb3O4 ranging between 17 and 88 wt % were utilized, whereas 87 wt % was used for PbO and PbO2. The prepared composites were investigated for their gamma radiation shielding properties. Moreover, physical and mechanical properties, and electrical conductivity were measured for both the unirradiated and irradiated composites. The highest value obtained for the linear absorption coefficient was 0.424 cm−1 for 88% Pb3O4.
Thermal conductivities of composites in several types of dispersion systems
Authors: Agari Y. , Ueda A. , Nagai S. 
Published: April 2003

AbstractWe measured thermal conductivities as well as electric conductivities of some composites in several types of dispersion systems. The dispersion state, that is, the ease in forming conductive chains in these composites, was estimated by the characteristic electric conductivities and compared with the thermal conductivities. Thus, it became clear that thermal conductivity of a composite was significantly affected by the dispersion state in the composite. Further, it was confirmed that the predictive model proposed in the previous report was adaptable to the thermal conductivity of the composites in several types of dispersion systems. It was made clear that the dispersion state of a composite affected the values C1 and C2 in the previous model.