bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization kinetics of PPS composites and quantification of fiber nucleation density using a computer simulation
Authors: Mehl Nathan A. , Rebenfeld Ludwig 
Published: April 2003

AbstractDifferential scanning calorimetry and hot‐stage optical microscopy were used to study the isothermal crystallization kinetics of unreinforced poly(phenylene sulfide) (PPS) and PPS reinforced with aramid, carbon, and glass fibers. The influence that fibers have on the crystallization kinetics of PPS was found to depend on the characteristics of the fiber as well as the type of PPS used. For one kind of PPS, fibers enhanced the crystallization rate, while for another type of PPS, reinforcing fibers had a moderate depressing effect on the polymer crystallization rate. To clarify these effects, we used a new method of quantifying the nucleation process in fiber‐reinforced composites that employs a 3‐D computer simulation of spherulitic crystallization. Using this method, the nucleation density in the bulk polymer, Nb, and the nucleation density on fiber surfaces, Nf, were calculated for PPS composites as a function of crystallization temperature. The calculated values of Nb and Nf were used to explain differences in the effectiveness of the fibers as well as differences in the nucleating characteristics of the two polymers. © 1995 John Wiley & Sons, Inc.
Synthesis and biological activities of copolymers of N‐glycinyl maleimide with methacrylic acid and vinyl acetate
Authors: Gam Gi‐Tak , Jeong Jin‐Gon , Lee Neung‐Ju , Lee Young‐Woo , Ha Chang‐Sik , Cho Won‐Jei 
Published: April 2003

AbstractCopolymerizations of N‐glycinylmaleimide (GMI) with methacrylic acid (MA) and vinyl acetate (VAc) were carried out in 2‐butanone using lauroylperoxide as an initiator at 70°C. Synthesized GMI, poly(GMI‐co‐MA), and poly(GMI‐co‐VAc) were characterized by IR and 1H‐NMR spectroscopies, elemental analysis, and gel permeation chromatography. The in vitro cytotoxicities of poly(GMI‐co‐MA) and poly(GMI‐co‐VAc) were evaluated using K‐562 human leukemia cells and HeLa cells. From the cytotoxicity data against HeLa cells, the copolymers are less cytotoxic than monomeric GMI at dosage of 0.02, 1.0, and 5.0 mg/mL. Copolymers were very effective at any dosage tested. The in vivo antitumor activities of poly(GMI‐co‐MA) and poly(GMI‐co‐VAc) were also evaluated against mice bearing sarcoma 180. Monomeric GMI and its copolymers showed higher antitumor activity than 5‐fluorouracil (5‐FU) at any dosage tested. © 1995 John Wiley & Sons, Inc.
Modeling of transfer phenomena on heterogeneous Ziegler catalysts: Differences between theory and experiment in olefin polymerization (an introduction)
Authors: McKenna T. F. , Dupuy J. , Spitz R. 
Published: April 2003

AbstractThis article begins by briefly reviewing the more important contributions to the area of modeling heat and mass transfer, and particle growth during the polymerization of olefins on Ziegler–Natta catalysts. It is shown that these models are capable of identifying the critical areas involved in heat and mass transfer, and of modeling polymerizations where the observed activity is less than approximately 5,000 g of polymer per gram of catalyst per hour (g/g/h). However, it is not possible to use these models “as‐is” to model more modern catalysts whose activity levels can surpass the 50,000 g/g/h mark because they predict prohibitively large concentration gradients inside the growing particles during slurry polymerizations, and temperature gradients outside the particles during polymerization in the gas phase. An analysis of the mass and heat transfer Peclet numbers (Pe) reveals that certain simplifying assumptions may not always be valid. Pe values in the transition range suggest that convection inside the particles during polymerization in the liquid phase may help to explain why observed mass transfer rates are higher than the predicted rates. In an opposite vein, a Pe analysis shows that conductive heat transfer may play an important role at length scales characteristic of those in the early stages of polymerization. A new mechanism for heat transfer at reduced length scales is proposed. © 1995 John Wiley & Sons, Inc.
Characterization of surface‐modified polyurethane blends, poly(vinyl alcohol), and poly(4‐hydroxybutyl acrylate) for biomedical application by electron spin resonance spectroscopy
Authors: Lorenz Günter , Klee Doris , Höcker Hartwig , Mittermayer Christian 
Published: April 2003

AbstractTwo polyurethane blends—poly(carbonate urethane)/poly(vinyl alcohol) [PCU/PVA] and the aliphatic poly(ether urethane) (Tecoflex™)/poly(pentanedioic acid mono‐4‐(acryloyloxy)butyl ester) [Tecoflex™/COOH]—were surface‐modified. Poly(vinyl alcohol) [PVA] and poly(4‐hydroxybutyl acrylate) [PHBA] were used as model surfaces. 4‐Isocyanato butanoic acid methyl ester was coupled as a spacer molecule to PVA and the PVA‐containing polyurethane blend. Saponification of the generated ester group was verified by means of Electron Spin Resonance (ESR) spectroscopy using the nitroxyl radical 4‐amino‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (4‐amino‐TEMPO) as a reporter group. In the case of Tecoflex™ and PHBA, glutaric anhydride served as a spacer molecule. 4‐Amino‐TEMPO was coupled to this spacer as well. ESR spectroscopy as a bulk method was used together with the surface‐sensitive method X‐Ray Photoelectron Spectroscopy (XPS) verifying the modification steps by elemental composition, ESR line shapes, and determination of the rotational correlation time τc. © 1995 John Wiley & Sons, Inc.
High TC superconductor polymer composite based on YBa2Cu3O7−x. II. Conduction mechanisms and temperature effect on conductive and dielectric properties of polypropylene composites
Authors: Acosta José Luis , Jurado José Ramón 
Published: April 2003

AbstractTo improve the connectivity of YBaCuO particles in a polypropylene matrix, different amounts of carbon black (N) or copper (C) were incorporated into the binary base system. In this research the effects of these conductor fillers on the conduction mechanism of the experimental composites were studied using complex impedance spectroscopy as the analytical technique. In addition the effects of temperature on certain electrical properties were examined in the synthesized materials. © 1995 John Wiley & Sons, Inc.
Exploration of the difference of reaction rates for polyester and polyether urethane prepolymers with 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane
Authors: Xiaolie Luo , Jin Liu , Dezhu Ma 
Published: April 2003

AbstractPolyester (PEPA) and polyether (PTMO) prepolymers with NCO end groups were synthesized. The chain extension reaction of these prepolymers with MOCA diamine was studied by FTIR spectrometry and found to be a second‐order reaction. Data on chain extension reaction rate constants and activation energy showed that the chain extension reaction rate of the PEPA prepolyme with MOCA was faster than that of PTMO prepolymer with MOCA. Such a difference of chain extension reaction rate for PEPA and PTMO prepolymers with MOCA can be explained by hydrogen bonding interaction and miscibility between hard and soft segments in the cast polyurethane elastomer. The hydrogen bonding interactions of MOCA with PEPA prepolymer and PTMO prepolymer without chain extension reaction convincingly demonstrated the difference of chain extension reaction in the polyurethane‐urea systems. © 1995 John Wiley & Sons, Inc.
Effects of cholesteric order on mechanical properties of (E‐CE)C/PAA composites
Authors: Jiang S. H. , Huang Y. , Shen J. R. 
Published: April 2003

AbstractThe ethyl‐cyanoethyl cellulose [(E‐CE)C]/poly(acrylic acid) [PAA] composites were prepared via in situ photopolymerization of the (E‐CE)C/acrylic acid (AA) solutions, in which the morphology and structure of (E‐CE)C was retained as the same as that in the solution. The strength and the modulus of the composites depended on their morphology and structure. The strength of the composites with a completely amorphous state or with a completely cholesteric order did not significantly change with increasing (E‐CE)C content, although the strength of the composites with completely cholesteric order is much higher than with the completely amorphous state. However, when the (E‐CE)C content changed from 33.8% to 42.5%, in which the composites had both cholesteric order and amorphous phases, the strength of the composites greatly increased with increasing (E‐CE)C. The elastic modulus of the composites with completely isotropic structure decreases with increasing (E‐CE)C content but abruptly increases with increasing the fraction of cholesteric phase in the composites. The (E‐CE)C with cholesteric order had a significant enhancing effect on the strength of the composites. The stress–strain curves indicated that the composites with completely amorphous or completely cholesteric order were breakable, while they were tough in the case when they had both cholesteric and amorphous phases. © 1995 John Wiley & Sons, Inc.
Morphological and rheological properties of PS melts filled with grafted and ungrafted glass beads
Authors: Friedrich Chr. , Scheuchenpflug W. , Neuhäusler S. , Rösch J. 
Published: April 2003

AbstractGlass beads carrying different amounts of polystyrene (PS) grafted to their surface were prepared by solution and melt‐mixing processes. These beads are mixed with a nearly mono‐disperse PS. The morphology of polymers filled with different volume amounts, ϕ, of modified and unmodified glass beads was investigated by scanning electron microscopy (SEM). In the case of PS‐grafted glass beads, the fracture surfaces show cohesive failure. The rheological properties of these filled polymers were investigated by mechanical spectroscopy. The material functions, the storage modulus G″ and the loss modulus G″, for PS melts filled with unmodified beads can be presented in an invariant from, e.g., independent of temperature and concentration. The temperature‐shift factors follow WLF behavior, and the concentration shift factors a generalized Maron Pierce equation. The rheological material functions of melts filled with modified glass beads can be superposed for different temperatures. However, a concentration invariant representation is only possible in the frequency range belonging to the plateau region. For small frequencies, a systematic deviation occurs whose strength depends on the amount of polymer grafted to the filler surface. It is argued that this behavior may be attributed to an additional relaxation process originating from the hindered flow of the modified glass beads. This process has to be investigated in more detail in the future. © 1995 John Wiley & Sons, Inc.
Polymeric systems bearing side‐chain 2,6‐dimethylbenzoyldiphenylphosphinoxide moieties for UV curable coatings: Synthesis and photoinitiation activity
Authors: Angiolini Luigi , Caretti Daniele , Carlini Carlo 
Published: April 2003

AbstractPolymeric photoinitiators with pendant 2,6‐dimethylbenzoyldiphenylphosphinoxide moieties were prepared by reacting the hompolymer of 4‐acryloyloxy‐2,6‐dimethyl benzoic acid, and its copolymers with n‐butyl acrylate with thionyl chloride followed by methoxydiphenylphosphine. These polymeric systems were characterized and their photoinitiation activity checked in the UV curing of a standard acrylic mixture, by irradiation both at 330 and over 380 nm, the latter conditions being applied to simulate a TiO2‐pigmented coating formulation. The results were compared with those obtained by using the low molecular weight analog 2,4,6‐trimethylbenzoyldiphenylphosphinoxide and previously prepared polymeric systems based on the benzoyldiphenylphosphinoxide moiety. The stability to light and to hydrolytic conditions of the polymeric photoinitiators with respect to the model compound was also tested. The results obtained are discussed and related to the structural requirements of these systems. © 1995 John Wiley & Sons, Inc.
Stereoblock polypropylene/isotactic polypropylene blends. III. Isothermal crystallization kinetics of iPP component
Authors: Canevarolo S. , De Candia F. 
Published: April 2003

AbstractThe isothermal crystallization of blends of stereoblock polypropylene and isotactic polypropylene were analyzed. The main interest in this phenomenon is related to the steric affinity between the two components. The composition of the blend was changed over a wide range. The obtained results demonstrate the incompatibility of the two components both in the liquid phase and the solid state. © 1995 John Wiley & Sons, Inc.
Kinetic study on the poly(methyl methacrylate) seeded soapless emulsion polymerization of styrene. II. Kinetic model
Authors: Lee Chia‐Fen , Chiu Wen‐Yen , Chern Yuan‐Chen 
Published: April 2003

AbstractA seeded soapless emulsion polymerization was carried out with poly(methyl methacrylate) (PMMA) as seeds, styrene as monomers, and potassium persulfate (K2S2O8) as the initiator to synthesize the PMMA/polystyrene (PS) composite latex. The morphology of the latex particles was observed by transmission electron microscopy (TEM). It showed a core‐shell structure. A core‐shell kinetic model was proposed for the seeded emusion polymerization, in which the thickness of the shell was not constant. An increase of the conversion would increase the thickness of the shell. The entire course of polymerization could be divided into three regions: In the first region, the propagation rate constant (Kp) and termination rate constant (Kt) were kept constant at constant temperature. The kinetic data showed that the square root of polymer yield (W) was proportional to the reaction time. In the second region, the gel effect was considered and the termination rate constant (Kt) was empirically modified. The Kt would decrease with increasing the conversion. In the third region, both the gel effect and the glassy effect were considered; the propagation rate constant was also empirically modified. The prediction on the conversion and the number‐average molecular weight of polymers during the seeded emusion of polymerization on the basis of our core‐shell kinetic model fitted well with the experimental data. © 1995 John Wiley & Sons, Inc.
Investigation on the simulation of the reactive extrusion of nylon 6
Authors: Yang Zhen‐Guo , Lauke Bernd 
Published: April 2003

AbstractIn this article, a novel simulation of the processing conditions of the anionic ring‐opening polymerization of nylon 6 in a counterrotating twin‐screw extruder by use of a modified Haake Rheometer run at elevated temperatures is described. Experimental results for several combinations of processing parameters are presented. General relations between processing parameters, conversion ratio, and molecular weight of the product are observed. These observations can be used in the eventual scaling up of investigation to an actual twinscrew extruder. © 1995 John Wiley & Sons, Inc.
Perfluoropolyethers with acid end groups: Amphiphilicity and emulsification
Authors: Kasai Paul H. 
Published: April 2003

AbstractInteractions of PFPE‐acids (perfluoropolyethers with carboxylic end groups) with a metal oxide surface and with aqueous systems were examined. The study revealed that (1) PFPE‐acids are preferentially adsorbed on metal oxide (ZrO2) surfaces over PFPE of nonfunctionalized form, (2) PFPE‐acids of shorter chain length are preferentially adsorbed over PFPE‐acids of longer dimension, and (3) the low molecular weight fraction (MW = 1300) of Demnum‐SH is abundant in molecular chains terminated with the acid end group at both ends. The study also revealed that PFPE‐acids, if agitated with aqueous solution of electrolyte, form an extremely stable macroemulsion of the water‐in‐oil type. The emulsion is extremely viscoelastic and may contain 50% by weight (hence, 65% by volume) of water. Water is occluded as droplets of diameter of 1–100 microns. A mechanism exists whereby aqueous protons are transported between droplets with the transfer rate ≥ 50 Hz at room temperature. Relevance of these observations in the lubricant application of PFPEs in magnetic recording media is discussed. © 1995 John Wiley & Sons, Inc.
Temperature and frequency effects on fatigue crack growth in acrylonitrile–butadiene–styrene (ABS)
Authors: Kim Ho Sung , Wang Xiang Ming 
Published: April 2003

AbstractFatigue crack growth (FCG) in a commercial‐grade acrylonitrile–butadiene–styrene (ABS) over the temperature and frequency ranges of 10–70°C and 0.01–10 Hz was studied. A model for the effects of temperature and frequency on the FCG rate was refined. The refined model is shown to accurately predict FCG rates in ABS. Three different types of fatigue fracture surfaces have been found. The first type is characterized by discontinuous growth bands; the second, by a rather smooth surface; and the last, by a rough surface relative to the second. The transition between the first and second types was found to be dependent on temperature and frequency as well, whereas the transition between the second and last types was found to be only dependent on temperature. These findings are discussed in relation to crazing. The apparent activation energy (ΔHth) was evaluated for both the first and second types to be 19.22 kJ/mol. © 1995 John Wiley & Sons, Inc.
Toughening of aromatic diamine‐cured trifunctional epoxy resins by modification with N‐phenylmaleimide–styrene copolymers containing pendant p‐hydroxyphenyl groups
Authors: Iijima Takao , Miura Satoru , Fukuda Wakichi , Tomoi Masao 
Published: April 2003

AbstractN‐Phenylmaleimide (PMI)–N‐(p‐hydroxy)phenylmaleimide (HPMI)–styrene (St) terpolymers (HPMS), containing pendant p‐hydroxyphenyl (HP) groups, were prepared and used to improve the toughness of triglycidyl aminocresol epoxy resin cured with p,p′‐diaminodiphenyl sulfone. HPMS was effective as a modifier for the toughening of the epoxy resin. When using 15 wt % of HPMS (1.0 mol % HP unit, Mw 129,000), the fracture toughness (KIC) for the modified resin increased 190% with a medium loss of flexural strength. The toughening of epoxies could be attained because of the cocontinuous phase structure of the modified resins. The decrease in flexural strength was suppressed to some extent by introducing a functional group into the modifier. The toughening mechanism was discussed in terms of the morphological behavior of the modified epoxy resin system. © 1995 John Wiley & Sons, Inc.
Preparation and characterization of porous polysulfone membranes with spacer‐bonded N‐containing groups
Authors: Rodemann Klaus , Staude Eberhard 
Published: April 2003

AbstractUltrafiltration membranes were prepared from epoxidized polysulfone by the conventional phase separation procedure. For epoxidizing, the polymer was first lithiated and a reaction followed with glycidyl‐4‐oxohexylether providing an eight atomic spacer. The reaction of the epoxy group with N‐containing substituents was performed heterogeneously using the ready membranes. The stability of the substituted membranes is visible by the fact that they are reacted under reflux conditions for 24 h. The reagents were trimethyl amine, diethylamine, n‐butyl amine, and tauric acid. Thus, positively charged, negatively charged, and neutral membranes were obtained. The membranes were characterized via ultrafiltation using dextran solution as well as human albumin solutions. In addition, the streaming potential was measured in the presence and absence of the protein. By these measurements the obviously neutral membranes were surprisingly identified to be positively charged. This is related to subsequent reactions of the spacer‐bonded epoxy groups with the amino groups. © 1995 John Wiley & Sons, Inc.
Codiluent effect on the properties of UV‐cured films
Authors: Khan Mubarak A. , Ali K. M. Idriss , Zaman M. M. , Hossain M. A. 
Published: April 2003

AbstractDifferent formulations were developed with an urethane oligomer combined with a number of reactive diluents with different functionalities such as N‐vinylpyrrolidone (monofunctional), butanediol diacrylate (difunctional), tripropylene glycol diacrylate (difunctional), and trimethylolpropane triacrylate (trifunctional). The films were prepared with these formulations and cured under UV radiation in the presence of the photoinitiator Irgacura 184. Their properties were characterized. The effect of codiluents of low glass transition temperatures like ethyl hexyl acrylate and methoxyethyl acrylate on the properties of these films was studied. These formulations were then applied as thin coatings on the leather surface in order to study the improvement of the leather substrate. Both tensile strength and elongation of the treated leather increased. The gloss of the coated leather was also enhanced. Incorporation of a plasticizer into these systems substantially improved the rheological properties of the coated leather. © 1995 John Wiley & Sons, Inc.
Physical aging of high‐performance thermoplastics: Enthalpy relaxation in PEK‐C and PES‐C
Authors: Di Yingwei , D'Amore Alberto , Marino Giuliano , Nicolais Luigi , Li Binyao 
Published: April 2003

AbstractThe developments of physical aging in phenolphthalein poly(aryl‐ether‐ketone) (PEK‐C) and poly(aryl‐ether‐sulfone) (PES‐C) with time at two aging temperatures up to 20 K below their respective glass transition temperatures (Tg = 495 and 520 K) have been studied using differential scanning calorimetry (DSC). Substantial relaxation within the aging course of several hours were observed by detecting (Tg) decreasing during physical aging process at the two aging temperatures. The relaxation processes of both polymers are extremely nonlinear and self‐retarding. The time dependencies of their enthalpies during the initial stages of annealing were approximately modeled using the Narayanaswamy‐Tool model. The structure relaxation parameters obtained from this fitting were used to predict the possibility of physical aging occurring at their respective using temperatures. © 1995 John Wiley & Sons, Inc.
Effect of the concentration of dye on the physical property of dye‐based polyurethane ionomer
Authors: Lee J. J. , Chi Z. K. , Kuo Y. M. , Chao D. Y. 
Published: April 2003

AbstractWe have successfully prepared Congo Red‐based polyurethane ionomers at our lab, and these ionomer structures have been proven by infrared (IR) spectra. For a dye‐based polyurethane ionomer molecule solution, the surface tension was found to decrease, but the number‐average particle size was found to increase with increasing concentration of Congo Red employed to prepare this ionomer molecule. Interestingly, the number‐average particle size of dye‐based polyurethane ionomer molecules decreases with increasing concentration of Congo Red in the presence of other dyes (i.e., Remajol Brilliant Blue R and Amaranth), as a result of Congo Red intramolecular interaction. It is important to point out that the addition of a fixed concentration of Amaranth to prepare Congo Red‐based polyurethane ionomer molecules will significantly enhance the tensile strength but will decrease the elongation of this ionomer molecule. © 1995 John Wiley & Sons, Inc.
New perfluoropolyether soft segment containing polyurethanes
Authors: Tonelli Claudio , Trombetta Tania , Scicchitano Massimo , Castiglioni Giovanni 
Published: April 2003

AbstractNew segmented polyurethanes (FPU) with perfluoropolyether (PFPE) blocks have been synthesized by a two‐step process. In the first step, a fluorinated isocyanate end‐capped prepolymer has been obtained by reaction of a fluorinated macrodiol with alicyclic diisocyanates in the presence of solvent. The following chain extension has been carried out by reaction of the prepolymer with short hydrogenated polyols giving a polymeric matrix. Tensile properties, dynamical–mechanical (DMA), and calorimetric (DSC) analyses have been evaluated, and relationships between chemical structure and final properties are established. These polymers show unusual low‐temperature elastomeric behavior, due to the low glass transition (Tg) of the continuous fluorinated phase. In general, with respect to traditional polyurethanes (HPU), thermal stability and chemical resistance are strongly improved by the effect of the highly inert fluorinated chains. © 1995 John Wiley & Sons, Inc.