bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of a surface active pyrrole on the conductivity of polypyrrole composites
Authors: Ruckenstein Eli , Chen Jyh‐Herng 
Published: April 2003

AbstractA surface active pyrrole, which has a long hydrophobic chain attached to the 3 position of the pyrrole ring, is used to modify the surface properties of the pores of a porous, crosslinked polystyrene. The latter is prepared starting from a concentrated emulsion (an emulsion with a large volume fraction of the dispersed phase, here 0.81) of water dispersed in a continuous medium composed of styrene, divinyl benzene, a suitable surfactant, an initiator, and the surface active pyrrole. This modified crosslinked porous medium is emplyed as the host for a polypyrrole composite that is prepared first by imbibing the host with a solution of pyrrole and subsequently with an oxidant solution. The latter plays the role of catalyst for polymerization as well as the role of dopant. The presence of the head groups of 3‐alkyl pyrrole molecules on the surface of the pores of the host polymer increases the affinity of the surface for pyrrole. The improved wetting thus achieved for the pyrrole solution ensures a higher connectivity among the pyrrole films present on the internal surface of the host polymer and increases the conductivity of the polypyrrole composites by a factor of 2 to 14, depending upon the solvents employed for pyrrole and oxidant.
Experimental investigation of vinyl chloride polymerization at high conversion—reactor dynamics
Authors: Xie T. Y. , Hamielec A. E. , Wood P. E. , Woods D. R. 
Published: April 2003

AbstractA series of suspension polymerizations of vinyl chloride monomer (VCM) was carried out in a 5‐L pilot plant reactor over the temperature range, 40–70°C. The reactor pressure and monomer conversion were monitored simultaneously every 7–8 min. The critical conversion Xf, at which the liquid monomer phase is consumed, was considered to occur when the reactor pressure fell to 98% of the vapor pressure of VCM for suspension at the polymerization temperature. The reactor model predictions of pressure are in excellent agreement with the experimental data over the entire conversion and temperature ranges studied. The mechanism of reactor pressure development for VCM suspension polymerization is discussed herein in some detail. For isothermal batch polymerization, the reactor pressure falls in two stages due to the effect of polymer particle morphology on pressure drop. The first stage is due to the volume increase of the vapor phase as a result of volume shrinkage due to conversion of monomer to polymer. The monomer phase is not yet consumed at this stage, but it is trapped in the interstices between primary particles creating a mass transfer resistance; therefore, the reactor pressure drops slowly. The second stage is due to both the volume increase of the vapor phase and to the monomer in the vapor phase diffusing into the polymer phase because of the subsaturation condition with respect to monomer in the polymer phase. The reactor pressure drops dramatically with an increase in monomer conversion at this stage. The present model can be used to predict reactor dynamics during suspension polymerization under varying temperature and pressure conditions.
Etch rate studies of base catalyzed hydrolysis of polyimide film. II
Authors: Pawlowski W. P. , Coolbaugh D. D. , Johnson C. J. , Malenda Mary J. 
Published: April 2003

AbstractThe influence of a potassium carbonate (K2CO3) additive on the base catalyzed hydrolysis of polyimide (Kapton†) film in aqueous potassium hydroxide (KOH) was determined experimentally. The etch rate is significantly greater for KOH/K2CO3 solutions compared with solutions composed of KOH only. The experimental order of the reaction with respect to the KOH concentration was found to be 1.5. In addition, the rate was found to increase linearly with respect to the K2CO3 concentration at a fixed KOH concentration. Visual observations of a thinner gel layer on the surface of the film, combined with increased solubility of the etch by‐products in KOH/K2CO3 relative to KOH, help to explain the difference in etch rate. It appears the ability of K2CO3 to enhance the solubility of the hydrolyzed polyimide (polyamic acid salt) results in faster etch rates.
Free volume effects on rheological and thermal properties of polymers and polymer blends
Authors: Steller Ryszard , Zuchowska Danuta 
Published: April 2003

AbstractUsing the free volume theory, general relations between viscometric and volumetric properties of polymers as functions of temperature and deformation conditions (shear rate or shear stress) have been derived. In particular, it has been shown that thermal expansion of polymers can be calculated from viscometric data. The obtained relations have been applied for description of the rheological behavior of polymer blends. Theoretical predictions have been compared with experimental data. Good agreement between theory and experiment has been stated if rheological properties of blends were compared at a constant shear rate.
Residual reactivity for surface grafting of acrylic acid on argon glow‐discharged poly(ethylene terephthalate) (PET) films
Authors: Hsieh You‐Lo , Wu Meiping 
Published: April 2003

AbstractThe wettability of poly(ethylene terephthalate) (PET) films in water was significantly improved upon exposure to argon glow discharge. Depending upon the lengths of glow‐discharge exposure, the water contact angle (CA) of the untreated film (73.1° ± 0.1°) was reduced to between 33.7° and 41.0° on the argon glow‐discharged films. Wettability decay was observed during the initial few days. Depending upon the treatment time, the water CA stabilized 4–7 days after the treatment and the extent of the wettability decay ranged from 4.3° to 7.6°. The residual reactivity of the glow‐discharged surfaces was captured by exposing the glow‐discharged PET to acrylic acid in the liquid and vapor phases. Optimal water CAs of 54.0° and 41.9° were achieved in the liquid‐phase and the vapor‐phase exposures, respectively. Wettability decay of these acrylic acid‐grafted PET surfaces was very small (0°–1.9°) for the liquid‐phase reactions and negligible (0.3°–0.6°) for the vapor‐phase reactions. The near absence of wettability decay or the greater stability of the grafted surfaces suggested the almost complete dissipation of the residual reactivity through reactions with acrylic acid. Surface morphology of the untreated as well as the acrylic acid‐grafted PET surfaces were examined and detailed by scanning electron microscopy.
IPDI‐based polyurethane ionomer dispersions: Effects of ionic, nonionic hydrophilic segments, and extender on particle size and physical properties of emulsion cast film
Authors: Kim Chang Kee , Kim Byung Kyu 
Published: April 2003

AbstractIsophoron diisocyanate (IPDI) ‐based polyester polyurethane (PU) dispersion in water was prepared in a prepolymer mixing process. Dimethylol propionic acid (DMPA), triethylamine (TEA), and triethyl tetramine (TETA) were used, respectively, as potential anionic center, neutralizing agent, and chain extender in aqueous phase. The effects of DMPA, butanediol (BD), and nonionic hydrophilic segment, viz. monofunctional ethylene–propylene oxide ether polyol, on the particle size of dispersion and the mechanical and viscoelastic properties of the emulsion cast films were systematically analyzed.
Preparation of cation‐exchange starches containing phosphoric acid groups
Authors: Khalil M. I. , Waly A. , Farag S. , Hebeish A. 
Published: April 2003

AbstractPoly(glycidyl methacrylate) ‐starch graft copolymer was prepared using hydrogen peroxide/ferrous sulphate/thiourea dioxide redox system as initiator. The copolymer was treated with orthophosphoric acid (H3PO4) under a variety of conditions to discover appropriate conditions for synthesizing the copolymer that can serve as cation exchanger. Results obtained indicated that the cation‐exchange capacity is enhanced by: (a) increasing the H3PO4/epoxy molar ratio up to 4; (b) using material‐to‐liquor ratio 1 : 2; (c) increasing duration (15–300 min) and temperature (60–90°C); (d) increasing the amount of epoxy groups of the copolymer; and (e) increasing the percent neutralization of H3PO4 up to 33.3%. Based upon the results obtained with these parameters, it was postulated that three reactions are involved during treatment of the copolymer with H3PO4. These reactions are phosphorylation, crosslinking, and hydrolysis. Conditions were established under which the phosphorylation reaction occurs exclusively. Studied also were the ion‐exchange properties of the phosphorylated copolymer, namely, pKa values, capacity for heavy metal ions removal, moisture content, durability, swellability, and solubility.
The drawing behavior of polyvinylalcohol fibers
Authors: Schellekens R. , Bastiaansen C. 
Published: April 2003

AbstractThe solid‐state drawing behavior and properties of solution‐spun polyvinylalcohol fibers were investigated. A comparsion was made with solution‐spun, ultra‐drawn polyethylene fibers. The maximum attainable draw ratio of polyvinylalcohol fibers is low (∼ 20), even at optimized conditions with respect to polymer concentration in solution. In contrast to polyethylene, the maximum attainable draw ratio hardly increases with increasing molecular weight. However, high modulus (∼ 70 GPa) and strength (∼ 2.3 GPa) polyvinylalcohol fibers can be produced, despite the low maximum attainable draw ratio. It is suggested that the observed phenomena, with respect to both the drawing behavior and properties of polyvinylalcohol fibers, originate from intermolecular hydrogen bonds in the polymer.
Bending‐beam measurement of solvent diffusions in polyimides: Theoretical and experimental
Authors: Jou Jwo‐Huei , Hsu Li 
Published: April 2003

AbstractA general formula correlating the bending curvature variation ratio of a layered structure caused by solvent‐induced swelling in its polymer overcoat with diffusion time under case II diffusion has been presented. In the event of case II diffusion, the diffusion front velocity, v, can be calculated by using this formula and measured by a bending‐beam apparatus. At room temperature, the diffusion of n‐methyl‐pyrrolidone (NMP) solvent in the film of pyromellitic phenylene diamine (PMDA‐PDA) is case II. While in PMDA‐B (‐benzidine) and benzophenone tetracarboxylic dianhydride (BPDA‐PDA), no diffusion progress can be observed. But, the diffusion in 6F‐dianhydride‐ (6FDA‐PDA) is case I with D = 0.85 × 10−9 cm2/s. It becomes anomalous when mixing with 25% PMDA‐B, but becomes case II diffusion with more PMDA‐B. The preabsorbed moisture in the films does not affect the v value. In PMDA‐PDA, v = 7.3 × 10−8 cm/s. In the 25/75 and 50/50 6FDA‐PDA/PMDA‐B blends, v = 6.3 and 11.3 × 10−8 cm/s.
Effect of flame‐retardant treatment on the mechanical properties of some tropical timbers
Authors: Eboatu A. N. , Amanfo I. , Akpabio I. O. 
Published: April 2003

AbstractPotassium aluminum sulphate, hereafter referred to as alum, was used as a flame‐retardant for some African timbers. It was observed that this treatment did not drastically reduce the strength of these timbers. Reasons are adduced to explain this result.
Surface modification of UHSPE fibers through allylamine plasma deposition. II. Effect on fiber and fiber/epoxy interface
Authors: Li Z.‐F. , Netravali A. N. 
Published: April 2003

AbstractThe surface of ultra‐high strength polyethylene (UHSPE) fibers was modified using allylamine plasma deposition to improve their adhesion to epoxy resins. Allylamine plasma polymerization was investigated at different power inputs and polymerization times. The adhesion of treated fibers to epoxy resin was studied by single‐fiber, pull‐out tests. A special silicon rubber mold was developed to embed the single fiber in epoxy resin. The results show that the interfacial shear strength (IFSS) increased by a factor of 2 to 3 after allylamine plasma treatments. The greatest improvement, by a factor of 3.25, was obtained at 30 W for 10 min. Scanning electron microscopy (SEM) was also used to study the surface topography of fibers pulled from the epoxy resin. In most cases, it was observed that pull‐out failure occurred at the interface, as evidenced from clean fiber surfaces. In a few cases, however, fibrils were peeled from fibers. The fiber strength decreased, but initial modulus increased after the plasma treatments. The decrease in fiber strength was insignificant for treatments at a lower power input, but was significant at higher power inputs. Treatment time, however, had no significant effect on fiber strength.
Crystallization behavior of high‐density polyethylene/linear low‐density polyethylene blend
Authors: Gupta A. K. , Rana S. K. , Deopura B. L. 
Published: April 2003

AbstractBinary blend of high‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE), prepared by melt mixing in an extruder, in the entire range of blending ratio, is studied for crystallization behavior by differential scanning calorimetry (DSC) and X‐ray diffraction measurements. Cocrystallization was evident in the entire range of blend composition, from the single‐peak character in both DSC crystallization exotherms and meltingendotherms and the X‐ray diffraction peaks. A detailed analysis of DSC crystallization exotherms revealed a systematic effect of the addition of LLDPE on nucleation rate and the subsequently developed crystalline morphology, which could be distinguished in the three regions of blending ratio, viz, the “HDPE‐rich blend,” “LLDPE‐rich blend,” and the “middle range from 30–70% LLDPE content.” Variations in crystallinity, crystallite size, and d spacing are discussed in terms of differences in molecular structure of the components.
Living carbocationic polymerization of isobutylene by tert‐amyl alcohol/BCl3/1‐methyl‐2‐pyrrolidinone initiating system
Authors: Pratap G. , Mustafa S. A. , Hollis W. K. , Heller J. P. 
Published: April 2003

Abstract1‐Methyl‐2‐pyrrolidinone has been investigated, for the first time, as an efficient electronpair donor in conjunction with tert‐amyl alcohol and BCl3 in CH2Cl2 diluent at −40°C for the living polymerization of isobutylene. The use of this new monofunctional initiator ‐trans fer (minifer) system has led to the synthesis of low molecular weight, living (near‐monodisperse) polyisobutylenes carrying “ethyl” head group and “tert‐chloro” end group (asymmetric telechelic polyisobutylenes). The nature of these groups was confirmed by 1H‐NMR spectroscopy. The living nature of the α‐ethyl‐ω‐(tert‐chloro)polyisobutylenes has been demonstrated by a linear plot, passing through the origin, of number‐average molecular weight (M̄n) vs. the amount of polymer formed (Wp) and a horizontal N (number of polyisobutylene molecules) vs. Wp plot. These results are further substantiated by gel permeation chromatography data of these polymers, and the molecular weight distributions of these polymers are narrow (low M̄w/M̄n = 1.1–1.2). The initiating efficiencies (Ieff) are close to 100% with this system. Dehydrochlorination of the prepolymer has yielded an isopropylidene (exo‐olefin) end group. Structure of the end group in the resulting polymer, α‐ethyl‐ω‐(isopropenyl)polyisobutylene, was confirmed by FTIR spectroscopy.
Specific volume of molten thermoplastic polymer composite at high pressure
Authors: Wang Y. Z. , Chia W. J. , Hsieh K. H. , Tseng H. C. 
Published: April 2003

AbstractThe specific volume of thermoplastic polymers and composites with glass fiber have been measured at high pressure, up to 2000 kg/cm2, in the molten state by a dilatometer. The specific volume and thermal expansion coefficient of the melts increase with increasing temperature at a constant pressure at a constant temperature. The data of specific volume of molten polymers were satisfactorily fitted to an empirical equation of state based on the Tait equation. Furthermore, it is found that the data of specific volume of molten composites were suitably fitted by an additive rule of Tait equation from the volume fractions of specific volume of polymers and the glass fiber in composites. The thermal expansion coefficients of molten polymers and composites are approach to the derivative values of the Tait equation, and the additive Tait equation, respectively.
Effects of curing accelerators on physical properties of epoxy molding compound (EMC)
Authors: Ogata Masatsugu , Kinjo Noriyuki , Eguchi Shuji , Hozoji Hiroshi , Kawata Tatsuo , Sashima Hiroki 
Published: April 2003

AbstractThe effects of various curing accelerators on the physical properties of epoxy molding compounds (EMCs) were investigated. Such properties as elasticities in rubbery and glassy regions, glass transition temperature, thermal expansion coefficient, and water absorption at 60°C of neat epoxy resins using various curing accelerators were found to be directly reflected in the properties of the EMCs that were prepared by using each resin system. However, volume resistivity and saturated water absorption at 120°C were not reflected. This was attributed to differences in the catalytic reactivity of accelerators causing different melt viscosity for the EMC, which resulted in different densities (packing degrees) and affected physical properties of molded EMC. On the other hand, it was found that the density of molded EMC was also affected by the molding conditions. To improve the physical properties of the molded EMC, in addition to proper selection of accelerators, it was very important to set the melt viscosity of the EMC as high as possible within the moldable range and to select suitable molding conditions.
Adsorption of anionic surfactants and related compounds from aqueous solution onto activated carbon and synthetic adsorbent
Authors: Ihara Yasuji 
Published: April 2003

AbstractThe adsorption isotherms of two anionic surfactants and sodium alkyl sulfonates with various carbon numbers onto activated carbon and synthetic adsorbent were measured in aqueous solutions. The adsorption affinities remarkably increased with an increase in the length of alkyl group in the adsorbates for both adsorbents. Furthermore, the amount of adsorption increases with addition of sodium chloride into the solutions. These behaviors suggested that the effect of hydrophobic interactions seem to play an important role on adsorption of both adsorbents.
Polymer compatibility and biodegradation of starch–poly(ethylene‐co‐acrylic acid)–polyethylene blends
Authors: Shogren R. L. , Thompson A. R. , Felker F. C. , Harry‐Ókuru R. E. , Gordon S. H. , Greene R. V. , Gould J. M. 
Published: April 2003

AbstractX‐ray diffraction, CP/MAS C‐13 NMR, DSC, FTIR and fluorescence microscopy have been used to study the structure, compatibility, and morphology of films made from starch, poly(ethylene‐co‐acrylic acid) (EAA), and polyethylene (PE) before and after exposure to a mixture of highly amylolytic bacteria. The components of starch, amylose and amylopectin, interact with EAA via the formation of V‐type inclusion complexes and hydrogen bonds. PE appears to be immiscible with the starch–EAA complex, with each forming sheetlike domains. The amylopectin in the films is susceptible to digestion by the bacterial consortium while the crystalline EAA–amylose complex is resistant. Digestion begins at the film surface and then proceeds inwards with sheetlike areas of starch removed. The good compatibility between starch and EAA as well as migration of EAA to the film surface explains the resistance of such films to digestion by conventional amylases.
In situ compatibilization of polystyrene/polyethylene blends using amino‐methacrylate‐grafted polyethylene
Authors: Song Zhiqiang , Baker Warren E. 
Published: April 2003

AbstractBlends of a styrene–maleic anhydride copolymer (SMA) with polyethlene (PE) or polyethylene melt grafted with tertiary (PE‐g‐DMAEMA) or secondary (PE‐g‐tBAEMA) amino methacrylate were prepared by blending in a batch melt mixer. The morphology of these blends at various compositions was examined with a scanning electron microscope (SEM) and related to their tensile and impact properties. The SMA/PE blends are found to have the typical coarse morphology of incompatible blends and poor mechanical properties, while their reactive conterparts, SMA/PE‐g‐DMAEMA or SMA/PE‐g‐tBAEMA blends, show finer morphology and modestly improved tensile and impact strength. This was attributed to chemical interaction of the acidic anhydride and the basic amino groups. The greater improvement in morphology for SMA/PE‐g‐tBAEMA than for SMA/PE‐g‐DMAEMA suggests a stronger interaction between the secondary amino groups and the anhydride groups, possibly with the formation of SMA‐g‐tBAEMA‐g‐PE graft polymer through amide covalent bonds. The amide formation appears to occur at the interfacial region in the blends and is too little to be detected by Fourier transform infrared (FTIR) spectra. However, differential scanning calorimeters (DSC) and the viscosity measurements indicate crystallinity and molecular weight changes for the SMA/PE‐g‐tBAEMA blends, supporting an argument for the formation of SMA‐g‐tBAEMA‐g‐PE grafts at the phase interface.
Photocrosslinked norbornene–thiol copolymers: Synthesis, mechanical properties, and cure studies
Authors: Jacobine A. F. , Glaser D. M. , Grabek P. J. , Mancini D. , Masterson M. , Nakos S. T. , Rakas M. A. , Woods J. G. 
Published: April 2003

AbstractA number of norbornene‐functionalized resins were prepared and their photoinitiated crosslinking reaction with a multifunctional thiol was studied. Access to these novel resins can be gained by several synthetic routes. The most general of these routes is the [4π + 2π] cycloaddition reaction (the Diels–Alder reaction) of the corresponding multifunctional acrylate ester with cyclopentadiene (CPD) monomer. The photocrosslinking reaction of these resins with multifunctional thiols such as pentaerythritol tetramercaptopropionate (PETMP) is quite rapid and sensitive to low UV dose as well as dose rate. FT‐IR cure studies also indicated that the cure rate slows down dramatically as the conversion approaches the calculated gel points for the systems under study. Mechanical properties of cured thin films of these materials exhibited a wide range of tensile and dynamic mechanical properties, which depended on the structure of starting materials used in the preparation of the norbornene resin and the crosslinking thiol.
Crystallinity and isotactic index of polypropylene samples prepared by VOCI3 and aluminum alkyls
Authors: Pandya M. V. , Maryam G. , Desai M. R. , Kumar K. Suresh 
Published: April 2003

AbstractThe X‐ray crystallinity and the isotactic index [II(%)] values were measured for polypropylene (PP) samples prepared by VOCI3 and various aluminum alkyls. The reaction parameters, such as aging time, temperature, reaction medium, and additives, have some effect on the crystallinity of the samples. Among the three systems studied, a combination of VOCI3 + Et2AICI was found to give PP with higher crystallinity and II. In general, the tacticity of the samples prepared were much lower than the samples prepared with α‐, β‐, γ‐TiCl3 as the catalyst.
Application of the blister test to the study of polymer–polymer adhesion
Authors: Chu Y. Z. , Durning C. J. 
Published: April 2003

AbstractThis article demonstrates the use of the blister test for measuring the fracture energy, Ga, of the interface between two incompatible polymers. We describe an apparatus in which a fluid was injected at constant rate at the interface between a solid, glassy polymer, and a thin rubbery overcoating to create a “blister.” The fluid pressure and blister geometry were measured as functions of time. An energy balance analysis reveals three independent methods for the calculation of Ga from the data. The method was applied to the system of polyisoprene/poly(methylmethacrylate). We used a sequential debonding procedure to obtain reproducible data following the theoretical predictions. The self‐consistency of the data suggested that the adhesion energy could be calculated reliably from the pressure alone, without using the blister geometry.