bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linear polythioesters. IV. The effect of hydrogen chloride acceptor on interfacial polycondensation of 4,4′‐di(mercaptomethyl) benzophenone with isomeric phthaloyl chlorides
Authors: Podkoscjelny Wawrzyniec , Kultys Anna 
Published: April 2003

AbstractNew polythioesters of better physicochemical and mechanical properties have been obtained by interfacial polycondensation of 4,4′‐di(mercaptomethyl)benzophenone with terephthaloyl, isophthaloyl, and phthaloyl chlorides with the use of sodium hydroxide excess as a hydrogen chloride acceptor. According to preliminary experiments, the best yield and the highest reduced viscosity are reached when the polycondensation at a 1:l ratio of the aqueous to the organic phase is carried out at a temperature of 5–7°C with a little excess of acid chloride with addition time of 0.5–2 min in the presence of 100% excess of NaOH as hydrogen chloride acceptor. The structure of the polythioesters was determined from elemental analysis and infrared spectra. Thermal properties of all polythioesters were determined. Mechanical and electrical properties of only the most interesting polythioesters obtained from isophthaloyl chloride were determined.
The functional role of molybdenum trioxide as a smoke retarder additive in rigid poly(vinyl chloride)
Authors: Lattimer Robert P. , Kroenke William J. 
Published: April 2003

AbstractThe most effective smoke retarders for poly(vinyl chloride) are compounds of transition metals, such as molybdenum trioxide. MoO3 when added to a rigid PVC compound shows three general effects. First, smoke formation is reduced dramatically as measured either by the NBS smoke chamber test or Goodrich smoke–char test. Second, volatile aromatic pyrolyzate formation is also reduced dramatically. The “pure” conjugated aromatic compounds (particularly benzene and naphthalene) are reduced more than the “mixed” aliphatic–aromatic compounds (such as toluene). Third, char formation is effectively promoted. Based on results from studying MoO3 (and other metal‐;based additives) in regular, perdeuterated, and syndiotactic PVC, we propose a “reductive coupling” scheme as the dominant mechanism to explain the smoke retarder action. In this mechanism the MoO3 acts in the condensed phase to promote extensive crosslinking of the PVC polymer chains very early in the thermal degradation process. Specifically, the metal additive forms a redox catalyst system which promotes intermolecular crosslinking of polymer chains to form char, rather than the conventional degradation process which gives rise to aromatics and smoke.
Numerical simulation of a tubular polymerization reactor
Authors: Lynch D. , Kiparissides C. 
Published: April 2003

AbstractA mathematical model for a tubular emulsion polymerization reactor is developed. The partial differential equations describing the mass balances on initiator, monomer, and number of polymer particles are numerically solved using an implicit–explicit scheme based on the Crank–Nicholson method. The model adequately simulates experimental results reported by Rollin and co‐workers and sufficiently explains the unusual behavior of the reactor when operating at relatively low emulsifier concentrations.
Conduction in polydiacetylene bilayers
Authors: Day David R. , Lando Jerome B. 
Published: April 2003

AbstractSurface active diacetylene monolayers were polymerized at the gas–water interface and bilayers formed from these layers were deposited onto lock‐and‐key devices. Samples exhibited intial conductivities on the order of 10−7 Ω−1 cm−1, which decayed at varying rates depending on sample composition to 10−11 Ω−1 cm−1. This initial space charge current was found to be strongly dependent on the presence of small amounts of water. A current increase was observed of over three orders of magnitude in some samples upon doping with iodine. Current flow decreased, however, back to original values after removal of the iodine. Polydiacetylene bilayers were also found to exhibit photo conductive current increases of over an order of magnitude.
Morphological changes in twisted nylon monofilament
Authors: Kurokawa Masataka , Nohara Nobuo , Konishi Takashi 
Published: April 2003

AbstractThe changes in structure of oriented nylon monofilaments due to an applied twisting action was investigated using wide angle x‐ray scattering analysis and microscopy. The surface layer of the twisted filaments changes to a single texture after being repeatedly twisted in one direction at high temperature. Simultaneously, kink bands were produced on their surface. Characteristic features of kink bands are observed on the surface layer of the filaments first twisted in one direction and then twisted in the opposite direction at high temperature. X‐ray diffraction patterns of the surface layer also changed remarkably. These changes in surface layers are related to the twist direction, the repeated number of twists, and the temperature of untwist. At lower temperatures, kink bands are not formed and a structural change to a single texture does not occur spontaneously.
Cation exchange resin from sulfonated N‐vinylcarbazole and divinylbenzene copolymer
Authors: Biswas Mukul , Mishra Girish Chandra 
Published: April 2003

AbstractA copolymer of N‐vinylcarbazole and divinylbenzene has been sulfonated to yield a cation exchange resin of improved thermal properties compared to other vinylcarbazole‐based resins. The resin has been characterized by measuring its total and salt‐spliting capacities, pH metric titration, and thermal stability characteristics.
Enhancement of adhesive joint strength by surface texturing
Authors: Chang W. V. , Wang J. S. 
Published: April 2003

AbstractProper substrate preparation is an indispensible step for achieving strong adhesive joints. One consequence of such surface treatment is the enhancement of degree of mechanical interlocking between polymers and substrates, which, according to the literature, seems to increase the strength of the joint. A novel method based on photolithography is developed to texture aluminum oxide surface by controlling the pit size and its spatial distribution. Surface profile, surface physical chemical properties of this sample, and the lap shear strength of epoxy adhesive joints are compared with those of the phosphoric acid anodized (PAA) sample. It is shown that the lap shear strength of the textured sample is superior to that of the PAA sample. Surface profile data and mathematical analysis suggest that the inferiority of the PAA sample is probably due to the trapped air in the large pit in the surface resisting the penetration of adhesives. It also concludes that the high surface area provided by the multitude small pits in PAA sample is far from being fully utilized. This study opens up a new avenue to rationally improve the strength of adhesive joint by controlling the surface profile, the surface chemical properties, and the pressure during bond formation.
Influence of drawing speed on some properties of acrylic fibers
Authors: Stoyanov A. I. , Krustev V. P. 
Published: April 2003

AbstractThe effect of drawing speed on several properties of acrylic fibers has been examined. The acrylic fibers were prepared by the wet‐spinning process. The coagulation bath contained 30–70% DMF and was held at a temperature varying from 10–45°C. From x‐ray diffraction measurement, the orientation of finished fibers increased with an increase in drawing speed, and became constant when the drawing speed exceeded 40–50 m/min. The tenacity and stability to repetitive deformation also increased to a drawing speed of 40–50 m/min, but then decreased. The spinning conditions (spin‐bath composition and temperature) influenced the most attainable properties of the finished fibers. The results are discussed from the point of view of structural changes in fibers during drawing.
Application of a constitutive equation to polymer melts
Authors: Shroff Ramesh N. , Shida Mitsuzo 
Published: April 2003

AbstractYamamoto's integral constitutive equation in which the memory function is dependent on the second invariant of the rate of deformation tensor at past times has been found to be successful in predicting many of the nonlinear viscoelastic functions from the linear viscoelastic data for melts of linear polyethylenes, polypropylenes, and polystryene but not for those of branched polyethylenes with high level of long‐chain branching. A specific functional form for the rate‐dependent relaxation spectrum is used and is based on the physical meaning resulting from the molecular entanglement theory of Graessley on steady shearing flow. No arbitrary constant is involved in such an interconversion scheme. The data examined are dynamic storage modulus and loss modulus, steady flow viscosity, first normal stress difference, and parallel superimposed small oscillations on steady shear flow. The theory predicts that in such parallel superimposed experiments, storage modulus G′(ω,\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) divided by the square of frequency shows a maximum under finite shear and that G′(ω,\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) would itself become negative at a frequency whose value is about one third the superimposed rate of shear. The experiments are in line with such predictions. Possible reasons for the failure of the theory for branched polyethylenes are considered, and a possible approach is suggested so that the interconversion scheme may be successful for such resins.
Adhesive properties of systems of partially neutralized carboxyl‐terminated liquid rubber–anhydride–bisepoxide
Authors: Matsuda Hideaki , Dohi Hidemi 
Published: April 2003

AbstractSystems of partially neutralized carboxyl‐terminated liquid rubber (PNCTLR)‐anhydride–bisepoxide were evaluated for adhesive properties. The PNCTLRs were prepared by the partial neutralization with MgO and CaO from a polymer of butadiene (BD) (Hycar CTB 2000X162) and copolymers of BD–acrylonitrile (Hycar CTBN 1300X8 and CTBNX 1300X9). As the bisepoxide, bisphenol A diglycidyl ether was used, and hexahydrophthalic anhydride was the anhydride used. The adhesive properties of the metal‐containing systems were superior to those of the reference systems not containing metal, owing to the polarity effect of the metal carboxylate groups. Further, the CTBN‐ and CTBNX‐series systems showed higher tensile shear and peel strengths than the CTB‐series systems, owing to the enhanced polarity effect of the nitrile groups.
A study on hydroxyl groups in polyethylene
Authors: Sato Yukihiko , Hoshino Mitsutoshi , Ebisawa Fumihiro 
Published: April 2003

AbstractThe possibility of the presence of hydroxyl groups in polyethylene molecular chains has been investigated in observations of infrared spectra of OH and CO stretching vibrations in olefinic molecular chains. n‐Paraffins and fresh medium‐pressure process polyethylenes containing the primary alcohols were used as a model of polyethylene containing hydroxyl groups in the molecular chains. The characteristic wavenumber of the hydroxyl groups slightly contained in the polyethylene in the region 3600–3200 cm−1 becomes constant over about 10 of carbon‐atom number of the alcohols, approximately 3336 cm−1. The wavenumber does not agree with ∼3370 cm−1, which has been hitherto assigned to hydroxyl groups in polyethylene molecular chains. Although the absorption due to the hydroxyl groups must appear in the region of CO stretching band in the vicinity of 1050 cm−1 if the absorption around 3370 cm−1 is due to the hydroxyl groups, the absorption has not been observed. Changes in infrared spectra of polyethylene absorbing water as much as 10 ppm corresponding to the water absorbing capacity are not observed in comparison with those of extremely dried polyethylene. It is concluded that the absorption at 3370 cm−1 in polyethylene is not due to the hydroxyl groups and that the groups are not contained at least in fresh polyethylene.
Grafting of acrylate monomers onto chlorinated rubber
Authors: Kaleem K. , Reddy C. R. , Rajadurai S. 
Published: April 2003

AbstractGrafting of chlorinated rubber with ethylacrylate and butyl methacrylate in xylene solution has been studied using benzoyl peroxide as the initiator. It is observed that the grafting reaction follows conventional kinetic behavior under the present experimental conditions. The energies of activation obtained for both monomers were 10.8 and 10.95 K.cals, respectively. The grafting efficiency and percent grafting were calculated. Additional proof for grafting onto chlorinated rubber was also obtained by characterization of the graft copolymer by gel permeation chromatography.
Ultradrawing of polystyrene by solid‐state coextrusion: Shear‐induced crystallization in isotactic polystyrene
Authors: Appelt Bernd , Porter Roger S. 
Published: April 2003

AbstractPolystyrene with a 60% isotactic dyad content (iPS) was subjected to two‐stage solid‐state coextrusion at 124 and 160°C. It was shown that only shear‐induced crystallization occurred with the amount of crystallinity strongly dependent on draw ratio. The steep increase in crystallinity from 0 to 29% is accompanied by a marked increase in the absolute total birefringence from 0 to 30 × 10−3 and the tensile properties, from 2.5 GPa to 4.5 GPa, giving strong evidence for the necessity of a crystalline phase to achieve higher tensile moduli. Wide‐angle X‐ray scattering showed a higher crystal orientation for the extrudate produced at 124°C than for the one produced at 160°C. Thermal shrinkage experiments support a partial dissipation of orientation after extrusion at 160°C and on reextrusion in general. Electron microscopy revealed a fibrous nature for the solid‐state coextrudates produced at both temperatures.
Novel ion‐containing reverse osmosis membranes. II. Reverse osmosis properties
Authors: Bittencourt E. , Stannett V. , Hopfenberg H. B. , Williams J. L. 
Published: April 2003

AbstractThe reverse osmosis properties of ion‐containing membranes prepared by60Co mutual irradiation grafting of 2‐vinylpyridine to poly(3,3‐bis(chloromethyl)oxetane) (polyoxetane, Penton) followed by quaternization with methyl bromide are presented. In general, the volumetric fluxes varied linearly with pressures up to 55 atm. Katchalsky's treatment of membrane permeability was used to analyze the data. Membrane constants and diffusion coefficients of water and sodium chloride were determined with membranes containing different volume fractions of water. The diffusion coefficients of water in the membranes were of the same order of magnitude as the self‐diffusion coefficient of water (∼3 × 10−5cm2/s). The diffusion coefficients of sodium chloride in the membrane were of the order of 10−7cm2/s. The diffusion coefficients increased with hydration, and the salt rejections were markedly affected by the external salt concentrations. The apparent energies of activation for the volumetric flux were calculated in distilled water and in 0.5% sodium chloride solution.
Accelerated photo‐oxidation of polyethylene. II. Further evaluation of selected additives
Authors: Taylor Lynn J. , Tobias John W. 
Published: April 2003

AbstractA number of additives previously observed to promote photo‐oxidative degradation of polyethylene films have been evaluated with respect to their relative photoinitiating effectiveness at wavelengths near 300 nm and their effects on thermal‐oxidative stability of polyethylene. Depending on the nature of the additive, the photo‐oxidation process may display autoretarding or autoaccelerating behavior. Thermomechanical analyses and gel content measurements on UV‐exposed films containing substituted anthraquinones suggest that at short exposure times, photo‐oxidative degradation is accompanied by photochemical crosslinking.
Chromic titanate catalysts for high‐melt‐index polyethylene by the particle‐form process
Authors: Hoff R. E. , Pullukat T. J. , Shida M. 
Published: April 2003

AbstractA novel thermal activation procedure for ethylene polymerization catalysts made from silica, a chromium compound, and a titanium ester greatly increases the melt index of the polyethylene product under commericla polymerization conditions in comparison with conventional air activation. The novel activation has two steps. The first is heating under a reducing gas atmosphere (N2 + CO). The second step is partial oxidation at a lower temperature for a shorter time. The size of the melt index increase is related to the average oxidation number of the chromium, but oxidized chromium can be reduced and the effect persists with less intensity. Additionally, the magnitude of the effect is dependent upon gas flow rates during activation and prior chemical and thermal history of the chromium–silica combination. Since titanium is required for the two‐step activation to be effective in increasing melt index, titanium atoms have a critical influence on the catalyst active sites. An experiment with tetraethoxysilane added to the catalyst shows that titanium and chromium atoms must be next nearest neighbors (separated by oxygen atoms).
Selective permeability of PVA membranes. I. Radiation‐crosslinked membranes
Authors: Katz Moshe G. , Wydeven Theodore 
Published: April 2003

AbstractThe water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution–diffusion model for transport across the membranes, in which pressure‐dependent permeability coefficients are employed.
Initial flux and rejection characteristics of partially permeable ultrafiltration membranes
Authors: Waters A. G. , Fane A. G. 
Published: April 2003

AbstractSolutions of bovine serum albumin (BSA) were ultrafiltered with and without stirring through membranes partially permeable to the solute, over a range of pH values. At the isoelectric point, flux was a minimum and rejection was a maximum. For all conditions, the flux for stirred ultrafiltration was greater than without stirring, as expected from conventional theory, and in contrast to recently reported “anomalous” behavior measured at the isoelectric point. Some evidence of unusual behavior at the isoelectric point was obtained when the flux of a freshly ultrafiltered solution of BSA was compared to that when the permeate and retentate were recombined, and when the retentate concentration was adjusted to the original concentration. For pH values other than the isoelectric point, the fluxes were similar for each set of experiments. At the isoelectric point, it was also found that flux was insensitive to changes in stirring speed. The unusual behavior at the isoelectric point is attributed to protein aggregation and precipitation causing loss of membrane permeability.
Diffusion coefficient measurements by solvent absorption in concentrated polymer solution
Authors: Hansen Charles M. 
Published: April 2003

AbstractDiffusion coefficient measurements for solvents in concentrated polymer solutions require consideration of both concentration dependence of the diffusion coefficient and surface resistance to mass transport. Solutions to the diffusion equation have been generated where these effects are explored. A method to account for both concentration dependence and surface (absorption) resistance in the experimental determination of diffusion coefficients is given and demonstrated with an example where a multiplying factor of over 300 is required to adjust the apparent diffusion coefficient to the value sought.
Polymerization of diallyl phthalate at high temperatures
Authors: Strumik M. I. , Królikowski W. , Jankowska M. 
Published: April 2003

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractPermeation 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.