bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosslinkable, nonlinear optical copolymers: Processing, corona poling, and second harmonic generation studies
Authors: Kawatsuki Nobuhiro , Schmidt Hans‐Werner , Pakbaz Khashayer 
Published: April 2003

AbstractPolymethacrylate copolymers, containing nonlinear optically active 4′‐dialkylamino‐4‐nitroazobenzene side groups and crosslinkable 2‐butenyl side groups were synthesized and characterized. Films of these copolymers can be thermally crosslinked at elevated temperatures and photochemically crosslinked by exposure with UV light. Both methods allow the control of the crosslinking density. A precrosslinking step, prior to the corona‐poling step, can be applied to optimize alignment and relaxation of the chromophores. During corona‐poling, the temperature dependence of the second harmonic generation (SHG) of an Nd‐YAG laser (1.064 μm) was studied for films with different degrees of precrosslinking. Depending on the conditions of precrosslinking, the SHG signal intensity and the alignment stability can be maximized. © 1993 John Wiley & Sons, Inc.
Solid‐phase modification of chitosan hydrogel membranes and permeability properties of modified chitosan membranes
Authors: Kubota Naoji , Kikuchi Yasuo , Mizuhara Yukako , Ishihara Tatsumi , Takita Yusaku 
Published: April 2003

AbstractA novel preparation method for modified chitosan membranes was developed. Chitosan hydrogel membranes were prepared by immersing an aqueous acetic acid solution of chitosan in KOH solution and modified with 3,3′‐dithiodipropionic acid (DTPA), which has a functional group that causes the thiol ⟷ disulfide transition through a redox reaction. It was smoothly modified with DTPA even in a solid‐phase modification when carbodiimides were used as the condensing reagents. The chitosan membrane modified with DTPA was reduced with tri‐n‐butyl phosphine (MSH membrane) and then oxidized with iodine (MSS membrane). Permeabilities of KCl, sucrose, and urea through these modified chitosan membranes were investigated. The permeability of urea was quite high and followed by KCl and sucrose in that order. The permeabilities of KCl and sucrose through the MSS membrane showed a decrease compared to those through the MSH membrane. The thiol ⟷ disulfide transition was responsible for changes in the permeabilities of KCl and sucrose. The permeability of urea was almost the same for both membrane systems, i.e., permeation of urea was not affected by the thiol ⟷ disulfide transition, probably due to the break of hydrogen bonding in the membranes. © 1993 John Wiley & Sons, Inc.
A compatibility study of waste poly(ethylene‐terephthalate) with poly(vinylchloride)
Authors: Akovali G. , Aslan S. 
Published: April 2003

AbstractMixtures of PET and PVC were prepared in three different compositions by a solution blending technique. A plasma surface modification method was applied to PET powder surfaces in order to enhance the miscibility of both components because of their mutual insolubility. The intrinsic viscosities of blends were measured in a phenol/tetrachloroethanemixed solvent system. The degree of compatibility of blends was characterized by the use of the parameter Δb, as derived by Krigbaum and Wall. © 1993 John Wiley & Sons, Inc.
Tetrabutylammonium benzoate‐initiated polymerization of propylene oxide
Authors: Chen Xuemin , Van De Mark M. R. 
Published: April 2003

AbstractThe polymerization of propylene oxide by the benzoate anion was aided through the use of the tetrabutylammonium counterion. The effect of the tetrabutylammonium ion was to increase the solubility of the salt and to increase the ion separation. The polymerization was carried out in a pressure reactor at temperatures from 40 to 108°C, producing polymer yields of 2–78%. The study addressed the general effects of solvent, temperature, and ratio of initiator to monomer. © 1993 John Wiley & Sons, Inc.
Star‐shaped condensation polymers: Synthesis, characterization, and blend properties
Authors: Gorda K. R. , Peiffer D. G. 
Published: April 2003

AbstractA series of ϵ‐caprolactone linear and star polymers were prepared and characterized in order to determine the effect of the star architecture (i.e., star number and arm length) on the morphology of these semicrystalline polymers. A spherulitic morphology was found in all the polymers investigated. However, for six arm stars containing low degrees of polymerization, it appears that the star core dominates its morphological behavior (presumably due to its relatively high volume fraction). The star core effects, however, are markedly reduced in star polymers were the arms contain higher degrees of polymerization.The impact of the star core was further explored by investigating several poly(ϵ‐caprolactone) (PCL):styrene–acrylontrile copolymers (SAN) blends. In all instances, miscible blends were the result because a single compositionally dependent glass‐transition temperature (Tg) was observed. A moderate elevation in the Tg of the star‐shaped polymers does occur, however, compared to their linear analogs. This effect is presumably due to the inability of the SAN chains to completely mix with all segments of star structure. © 1993 John Wiley & Sons, Inc.
Swelling of poly[methacrylic acid‐co‐poly(oxytetramethylene) dimethacrylate]s
Authors: Kojima Takakazu , Masuda Kazuhisa , Taco Kazuaki 
Published: April 2003

AbstractAn equation of swelling equilibrium is derived for crosslinked copolymer including incomplete network structures, to be applied to the swelling data on copolymer of poly(oxytetramethylene) dimethacrylate (POTMDM) with methacrylic acid (MAA). Poly(MAA‐co‐POTMDM)s with various monomer contents, is prepared by copolymerization in N,N‐dimethylformamide (DMF). The equation shows good applicability to the swelling behaviors of poly(MAA‐co‐POTMDM) for tetrahydrofuran (THF) and DMF systems. A difference in polymer‐polymer interaction parameter between THF and DMF systems, derived from the results of curve fitting is explained in terms of dependence of polymer‐solvent interaction parameter on crosslink density. © I993 John Wiley & Sons, Inc.
Alkaline PF resins linear extension by urea condensation with hydroxybenzylalcohol groups
Authors: Pizzi A. , Stephanou A. , Antunes I. , De Beer G. 
Published: April 2003

AbstractThe linear increase of phenol–formaldehyde (PF) resins by reaction under alkaline conditions of the ortho‐ and para‐hydroxybenzylalcohol groups of the PF resin with small molar percentages of urea was followed by model compounds reactions. Apparent rate constants of the reactions of urea with o‐and p‐hydroxybenzylalcohols were obtained. Both the ortho‐ and para‐isomerides appeared to react faster with urea than for their autocondensation. The ortho‐isomeride appears to react faster with urea than the para‐isomeride, under alkaline conditions. Autocondensation under alkaline conditions instead appears to be faster in the case of p‐hydroxybenzylalcohol. The properties of PF resins prepared with the addition of small amounts of urea appear to be consistent with what is observed in the model compounds reactions: Their gel times become faster and viscosity increases with increasing amounts of urea addition. © 1993 John Wiley & Sons, Inc.
Mass transfer effects in emulsion polymerization systems. I. Diffusional behavior of chain transfer agents in the emulsion polymerization of styrene
Authors: Nomura M. , Suzuki H. , Tokunaga H. , Fujita K. 
Published: April 2003

AbstractOn the basis of the so‐called two‐films theory for mass transfer, a mathematical model for transfer of chain transfer agents from monomer droplets to polymer particles, where chain transfer agent molecules are consumed by the chain transfer reaction, is developed for an emulsion polymerization system. It is shown by the model that the concentration of chain transfer agent in the polymer particles during the polymerization is decreased to a value much less than that which would be attained if thermodynamic equilibrium for chain transfer agent were reached between the polymer particles and the monomer droplets, due mainly to the resistance to transfer of chain transfer agent molecules across the diffusion films at the interface between the monomer droplets and the water phase. The validity and utility of the model developed for predicting the diffusion and consumption rates for chain transfer agent are demonstrated experimentally using five normal aliphatic mercaptans from n‐C7 to n‐C12 as chain transfer agents in the seeded emulsion polymerization of styrene. © 1994 John Wiley & Sons, Inc.
Critical parameters for heat transfer and chemical reactions in thermosetting materials
Authors: Gebart B. Rikard 
Published: April 2003

AbstractThe equations of one‐dimensional heat transfer with chemical reactions with isothermal initial conditions and constant wall temperature are solved approximately for all types of kinetic models. The general solution is valid for low exothermal peaks and it is characterized explicitly by two dimensionless parameters. The first parameter is the ratio between the time scale for heat conduction and that for the chemical reaction; the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The number of additional parameters depends on the particular choice of kinetic model. The maximum temperature in the solution always occur at the center line and its magnitude is proportional to the maximum rate of reaction. For a second‐order autocatalytic kinetic model, closed from results can be obtained. The solution is in this case characterized by two additional dimensionless parameters. The analytical solution agrees excellently with numerical solutions for small exothermal temperature peaks (<10% of the adiabatic temperature rise), but the qualitative agreement is very good also for cases with significant exothermal peaks. The general solution can be used also for the case when the kinetic model is unknown and only experimental DSC results are available. © 1994 John Wiley & Sons, Inc.
The interaction of sulfenamide accelerators with sulfur, ZNO, and stearic acid in the absence of rubber
Authors: Gradwell M. H. S. , Mcgill W. J. 
Published: April 2003

AbstractThe interaction of sulfur, ZnO, stearic acid, and the three sulfenamide accelerators N‐cyclohexylbenzothiazole sulfenamide (CBS), 2‐(4‐morpholinothio) benzothiazole (MOR), and 2‐t‐butylaminobenzothiazole sulfenamide (TBBS) were investigated by differential scanning calorimetry in the absence of rubber. In the presence of sulfur, the same product spectrum is formed as in its absence, but at lower temperatures. Thus, CBS gives N‐cyclohexylamino‐2‐benzothiazole polysulfides (CBP), 2‐bisbenzothiazole‐2,2′‐disulfide (MBTS), 2‐bisbenzothiazole‐2,2′‐polysulfides (MBTP), and 2‐bisbenzothiazole‐2,2′‐monosulfide (MBTP), 2‐mercaptobenzothiazole (MBT), and 2‐N‐cyclohexylaminobenzothiazole (CB). In the presence of sulfur, the amount of polysulfides formed initially is higher but the polysulfides are unstable, and on prolonged heating, only MBT and CB remain. MOR and TBBS form analogous product spectra. The sulfenamides do not react with ZnO or zinc stearate. The MBT–amine complex prevents MBT, formed on decomposition, from reacting to give zinc mercaptobenzothiazole (ZHBT). Reaction mechanisms are proposed to account for the formation of the products. © 1994 John Wiley & Sons, Inc.
Effect of viscosity ratio and processing conditions on the morphology of blends of liquid crystalline polymer and polypropylene
Authors: Heino Markku T. , Hietaoja Pirjo T. , Vainio Tommi P. , Seppälä Jukka V. 
Published: April 2003

AbstractThe effect of viscosity ratio and processing conditions on LCP/PP blend morphology was studied. The viscosity ratio (ηLCP/ηPP) was varied from 0.1 to 3.6 by using five different polypropylene grades as the matrix and two LCPs as the dispersed phase (20 wt %). The most spontaneous fiber formation was achieved when the viscosity ratio was between 0.5 and 1. In addition to shear forces, elongational forces are important in achieving a highly fibrillar structure and significant mechanical reinforcement. The lubricating effect induced by the low viscosity of LCP was most pronounced for the blends exhibiting a fibrillar morphology. The morphologies of blends produced by different mixing equipment differed only slightly. The greatest variation in the mixing efficiency was found for blends whose components had totally dissimilar melt viscosities. The slight differences in morphology due to melt blending in dissimilar equipment were decreased after injection molding, whereas the differences in morphology due to dissimilar viscosity ratios were still evident in the injection molded blends. Thus, the viscosity ratio at processing in the actual processing conditions is of great importance. © 1994 John Wiley & Sons, Inc.
Polymer dissolution. I. On the dissolution behavior of copolymers of methyl methacrylate and methacrylic acid
Authors: Reinhardt M. , Pfeiffer K. , Lorkowski H.‐J. 
Published: April 2003

AbstractCopolymers of methyl methacrylate with methacrylic acid [P(MMA/MA)] are interesting resist materials for microlithography. At moderate baking temperatures, these copolymers undergo an intramolecular cyclization, yielding terpolymers containing anhydride moieties. This process has striking consequences for the dissolution behavior and results in higher ketone solubilities. The dissolution rates in methyl ethyl ketone (MEK) and in mixtures with ethyl glycol (EG) correlate in an Arrhenius‐like manner with the reciprocal baking temperatures. Two distinct temperature ranges with different slopes between 130–180°C and 180–230°C are found. This is in good agreement with other findings, indicating a different mechanism of anhydride formation in these temperature regions. The activation energies for the dissolution of P(MMA/MA) in EG or EG/MEK mixtures are about 17 kcal/mol and those of the thermally treated material in MEK or MEK/EG or mixtures of MEK with methyl isobutyl ketone (MIBK) are in the range of 20–30 kcal/mol. For the investigation of the Mn dependence, γ‐irradiated probes of the copolymer were used. We obtained the usual exponential Mn dependence with an exponent of 0.7–0.8 in MIBK and 0.3–0.4 in EG. Our findings are in agreement with a “relaxation‐controlled” dissolution behavior, especially for the anhydride‐containing terpolymer. No residual layers or pronounced inhibition periods indicative for gel‐layer formation, however, could be found. We suggest a normal dissolution process with a very small gel layer. For the copolymer in an alcohol‐containing solvent, a stress‐driven dissolution behaviour is more likely. © 1994 John Wiley & Sons, Inc.
Radiochemical graft copolymerization of methacrylonitrile and binary mixture of methacrylonitrile with 4‐vinylpyridine onto isotactic polypropylene fiber
Authors: Kaur Inderjeet , Barsola Raghuvir , Misra B. N. 
Published: April 2003

AbstractGraft copolymerization of methacrylonitrile (MAN) and its binary mixture with 4‐vinylpyridine (4‐VP) onto isotactic polypropylene (IPP) fiber has been studied in aqueous medium by the preirradiation method. Optimum conditions for obtaining the maximum percentage of grafting have been evaluated. Rate of grafting (Rg) has been determined as a function of total initial monomer concentration. The graft copolymers are characterized by IR spectroscopy, by thermogravimetric analysis, and by isolating the polymer from the graft copolymer. The effect of MAN, an acceptor monomer, on percentage of grafting of 4‐VP, a donor monomer, has been discussed in the light of the mechanism proposed for grafting by the radiochemical method. © 1994 John Wiley & Sons, Inc.
Investigation of ethylene/1‐octene copolymerization models by carbon‐13 NMR
Authors: Bailey A. L. , Kale L. T. , Tchir W. J. 
Published: April 2003

AbstractStatistical reaction models have been used to fit C‐NMR spectra for ethylene/1‐octene copolymers and to describe the polymerization reaction probabilities. Ten models ranging in complexity from a one‐site Bernoulli probability to multiple site second‐order Markov systems were studied. Model parameters were determined by fitting the experimental integrations of replicated spectra using a maximum likelihood method. The best fit to the experimental NMR spectra was obtained with a two‐site model, one site producing mainly high‐density polymer following a Bernoulli probability model, while the second site allows more incorporation of octene following a chain‐end controlled probability described by first‐order Markov statistics. © 1994 John Wiley & Sons, Inc.
Preparation and application of low molecular weight poly(vinyl chloride). IV. Preparation and characteristics of poly(vinyl chloride) with broad molecular weight distribution
Authors: Yamamoto Kikuo , Maehara Takashi , Mitani Katsuo , Mizutani Yukio 
Published: April 2003

AbstractPoly(vinyl chloride) (PVC) with a broad molecular weight distribution (BMD‐PVC) was prepared by suspension polymerization in the presence of PVC with relatively lower molecular weight (LMW‐PVC), which was prepared by suspension polymerization in the presence of 2‐mercaptoethanol as a chain‐transfer agent. It is elucidated using porosity measurement, scanning electron microscopy (SEM), and energy dispersion X‐ray microscopy (EDXM) that the resultant BMD‐PVC grains have an interesting internal structure at the level of primary particles. Discoloration time and fusion time of the BMD‐PVC was studied. Discoloration time and fusion time of BMD‐PVC is particularly dependent on the polymerization degree (Pw) of LMW‐PVC and LMW‐PVC content in the BMD‐PVC samples. © 1994 John Wiley & Sons, Inc.
The synthesis and gas‐transport properties of some hydrosilylation condensation polymers
Authors: Rickle Greg K. 
Published: April 2003

AbstractHigh‐permeance collection layers are needed in composite membranes but few polymers have the required permeability. Hydrosilylation condensation polymers, because of their high silicon content, were thought to be good candidates to have high permeabilities. Several novel polymers were made and a new and simpler synthesis of ethynylated silanes is reported. One polymer, poly(divinyldimethylsilane‐co‐1,4‐bis [dimethylsilyl] benzene), appears to be of a liquid crystalline nature and has a low oxygen permeability (1.10 barrers). Two others [poly(diethynyldimethylsilane‐co‐1,4‐bis) [dimethylsilyl] benzene and poly(divinyldimethylsilane‐co‐p,p′diethynylbiphenyl‐co‐tetramethyldisiloxane)] were viscous liquids that could be thermally cured to give elastomers with oxygen permeabilities of ˜ 85 barrers. © 1994 John Wiley & Sons, Inc.
Structural changes and dyeability of silk fibroin fiber following shrinkage in neutral salt solution
Authors: Tsukada Masuhiro , Kato Hiroshi , Freddi Giuliano , Kasai Nobutami , Ishikawa Hiroshi 
Published: April 2003

AbstractThe fine structural changes of Bombyx mori silk fibroin fibers, induced by shrinking with concentrated calcium chloride aqueous solution at elevated temperature were investigated as a function of shrinking rate. Tensile strength decreased and elongation at break increased in the shrinkage range 13–67%, the shape of the stress–strain curve changing from rubberlike to brittle at high shrinkage values (70–90%). The birefringence gradually decreased over the entire shrinking range examined, the curve becoming steep as the shrinkage exceeded about 67%. The behavior of isotropic refractive index (niso) closely resembled that of birefringence (Δn) in the shrinking range 13–67%. Beyond shrinkage of 67%, the niso showed a tendency to increase, especially for the sample with 80% shrinkage. Dichroism measurements showed that the molecular orientation within the amorphous regions decreased sharply at the beginning of the shrinking treatment, within the range 0–13%, then attained a saturation at about 55%. The position and intensity of the major X‐ray diffraction peak at 20.5° remained essentially unchanged regardless of the shrinking treatment. The results of dyeing behavior showed that the saturation value attained by shrunk silk fibers was significantly larger than that of the untreated control sample. Both standard affinity and the heat of dyeing increased slightly for the shrunk silk fibroin fiber, suggesting that a larger number of reactive sites became available for the interaction between dye molecules and fibroin chains. A schematic model is proposed for explaining the relation between structural changes and enhanced dyeability of the silk fibers following shrinkage in neutral salt solution. © 1994 John Wiley & Sons, Inc.
Influence of electrolyte on electrical properties of thin cellulose acetate membranes
Authors: Friebe A. , Moritz W. 
Published: April 2003

AbstractThe electrical behavior of thin cellulose‐2.5‐acetate membranes for chemical semiconductor sensor applications was investigated. The influence of electrolyte on the electrical membrane properties was studied by means of electrochemical impedance spectroscopy. The polymeric membranes can be described using the electrical model of Cole and Cole. The membrane electrolyte distribution equilibria were investigated by means of an absorption–desorption method using conductivity measurements. The desorption kinetics for thin cellulose acetate membranes differ significantly from those of thicker cellulose acetate reverse osmosis membranes because here the rate of the ionic exchange at the membrane interface cannot be neglected. The experimentally determined distribution coefficients were used for the discussion of the electrolyte influence on the electrical membrane parameters. A functional dependence was found between the specific membrane resistance of cellulose acetate membranes and the ionic hydration enthalpy. The effect of electrolyte on the relative permittivity can be explained by a theoretical model. © 1994 John Wiley & Sons, Inc.
Crystallization of nylon 6–clay hybrid by annealing under elevated pressure
Authors: Kojima Yoshitsugu , Matsuoka Takaaki , Takahashi Hideroh , Kurauchi Toshio 
Published: April 2003

AbstractNylon 6–clay hybrid (NCH) is a molecular composite of nylon 6 and uniformly dispersed silicate layers of montmorillonite. We found that the phase with the high melting temperature (HMT phase) in the NCH annealed under elevated pressure. The melting temperature of the HMT phase was 240°C. Nylon 6 annealed under elevated pressure did not have the HMT phase. Thus, the presence of the HMT phase was characteristic of the NCH. The relative heat of fusion of the HMT phase (heat of fusion of HMT phase/heat of fusion in the pressure annealed NCH) increased with increase in pressure. High‐pressure differential thermal analysis (DTA) measurement revealed that the temperature, at which the relative heat of fusion showed a maximum value, was below about 20°C of the melting temperature of the original NCH under elevated presssure. It was considered that the nylon 6 crystallite near the melting temperature and the molecular mobility under elevated pressure were necessary to the appearance to the HMT phase. © 1994 John Wiley & Sons, Inc.