bluuebunny/crossref_metadata_2025_split huggingface dataset:
XPS surface studies of injection‐molded poly(phenylene ether)/nylon 6,6 and poly(phenylene ether)/HIPS blends
Authors: Bhatia Qamar S. , Burrell Michael C. , Chera J. J. 
Published: April 2003

AbstractThe surface compositions of a series of poly(phenylene ether)/nylon 6,6 blends (PPE/PA), and PPE/HIPS blends, prepared by melt compounding and injection molding, have been quantitatively measured using XPS. For PPE/PA blends, the surface is dominated by the PA component for blends containing more than 25 wt % PA in the bulk. The enrichment of the PA component, which is actually the component of highest surface free energy, is rationalized in terms of the bulk morphology that consists of PPE domains in a PA continuous phase. Blends prepared by reactive extrusion processes, which form compatibilizing PPE/PA copolymers, show a decrease in surface PA enrichment with increasing copolymer content in the final blend. PPE/HIPS blends have a surface composition equal to the formulated value over the entire composition range, for both molded and solvent cast blends. The addition of 5% PVME to a 60/40 PPE/HIPS blend results in a molded surface containing 35–40 wt % PVME. © 1992 John Wiley & Sons, Inc.
Study of the interactions of model polymer surface with cold plasmas. II. Degradation rate versus pressure and gas flow rate
Authors: Shi M. K. , Clouet F. 
Published: April 2003

AbstractThis work deals with the influence of pressure, gas flow rate, and gas mixture on the etching rates of polymer model molecules such as hexatriacontane (C36H74) and octadecyl octadecanoate (OOD) treated in an oxygen or argon plasma. Mass spectrometry and optical emission spectroscopy have been used to monitor the formation and evolution of the fragments coming from chain breaking in terms of their concentration and emission intensity, respectively. It was demonstrated that pressure and gas flow rate are two important parameters in the interaction of cold plasmas and of polymer surfaces. The results obtained can be explained by combined effects such as electron energy and its density, residence time, “quenching effect,” as well as chemical reactions. © 1992 John Wiley & Sons, Inc.
Studies on tributyl tin methacrylate (TBTM). VI. Thermal and tensile behavior of copolymer of tri‐n‐butyl tin methacrylate and methyl methacrylate
Authors: Samui A. B. , Patri M. , Deb P. C. 
Published: April 2003

AbstractThe thermal and tensile properties of polytributyl tin methacrylate (PTBTM) and n‐tributyl tin methacrylate–methyl methacrylate (TBTM—MMA) copolymers have been studied. Thermogravimetric study showed that with increasing the TBTM content in the copolymer the thermal stability decreases. The glass transition temperature (Tg) decreases continuously as the TBTM content increases. All the polymers showed multistep decomposition. MS study showed that in addition to monomer formation several other side reactions also take place during degradation, leading to formation of other products. Studies on tensile properties show that the tensile strength decreases with increasing TBTM content, whereas elongation at break increases. © 1992 John Wiley & Sons, Inc.
The study of curing behavior and thermal properties for soybean oil fatty acid‐modified glycidyl methacrylate
Authors: Lee Wen‐Fu 
Published: April 2003

AbstractThe characteristics of glycidyl methacrylate (GMA)–modifiers, including the polymerization properties, curing properties, and thermal stability, were studied. The degree of crosslinkage for (GMA–modifier)polyols increases with increasing hexamethoxymethylmelamine (HMMM) content and reaches maximum when HMMM content is about 40 wt %. The gels obtained from thermal free‐radical polymerization for GMA‐modifier monomer decrease with increasing acid value. UV curing experiments indicate that the energy of ultraviolet might be insufficient to promote the curing reaction through transetherification with short‐term irradiation. Kinetic parameters for the thermal decomposition of the polymer were measured with TG thermograms. © 1993 John Wiley & Sons, Inc.
Arylidene polymers. XVIII. Synthesis and thermal behavior of organometallic arylidene polyesters containing ferrocene derivatives in the main chain
Authors: Abd‐Alla Mohamed M. , El‐Zohry Maher F. , Aly Kamal I. , Abd‐El‐Wahab Mohamed M. M. 
Published: April 2003

AbstractA new interesting category of organometallic polyesters based on diarylidenecycloalkanones containing ferrocene derivatives in the polymer main chain has been prepared by interfacial polycondensation of 1,1′‐dichlorocarbonyl ferrocene or 1,1′‐dichlorocarbonyl‐4,4′‐diiodoferrocene with 2,5‐bis(p‐hydroxybenzylidene)cyclopentanone, 2,5‐divanillylidenecyclopentanone, 2,6‐bis(p‐hydroxybenzylidene)cyclohexanone, 2,6‐divanillylidenecyclohexanone, and 2,7‐bis(p‐hydroxybenzylidene) cycloheptanone. The resulting polyesters were characterized by elemental analyses, infrared spectroscopy, solubility, and viscometry measurements. The thermal behavior of the synthesized polymers was evaluated by thermal gravimetric analysis and correlated with their structures. The crystallinity of all polymers were examined by x‐ray diffraction analysis. Moreover, the electrical conductivity of a selected example of polymer was investigated above the temperature range (300–500 K) and showed that it followed an Arrhenius‐type equation with activation energy 2.09 eV. © 1993 John Wiley & Sons, Inc.
The chemistry and development of branched PRF wood adhesives of low resorcinol content
Authors: Scopelitis E. , Pizzi A. 
Published: April 2003

AbstractPhenol–Resorcinol–Formaldehyde (PRF) resins of good adhesive performance, and of resorcinol content much lower than in traditional PRF cold‐setting adhesives, were prepared by introducing small amounts of urea as a branching unit during preparation of the resin. Resorcinol contents as low as 10.6% were obtained by this method while still maintaining an acceptable pot‐life of the resin. Resorcinol contents as low as 8%, still with a good adhesive performance, were obtained, although the pot‐life obtained was too short. GPC, FT–IR and C13 NMR indicated that the small amount of urea branching unit used leads to the reduction of resorcinol content mostly by rapid doubling of the average linear length of the PF intermediates and of the final PF oligomers. Tridimensional branching in the liquid resin, contrary to what was previously thought, does not appear to be an important contributory factor and better adhesives are often prepared when branching is totally, or almost totally, absent. Reduction of resorcinol content is achieved simultaneously by two mechanisms: (i) the decrease of resorcinol percentage on resin solids due to the rapid lengthening (doubling) of average oligomers length and (ii) the need for these resins to operate at lower solids content, due to the increased viscosity obtained during their preparation. © 1993 John Wiley & Sons, Inc.
Relationship between melt viscosity and dielectric relaxation time for a series of epoxide oligomers
Authors: Koike Tsuneo 
Published: April 2003

AbstractMelt viscosity has been investigated for a series of bisphenol‐A type epoxide oligomers with different weight‐average mol wts (M̄w), ranging from 388 to 2640. The temperature dependence of the melt viscosity is described by the Williams–Landel–Ferry (WLF) equation. The melt viscosity η is correlated with both the direct current (dc) conductivity σ and the dielectric relaxation time τ. The two relationships between these three properties, σ·ηκ = const (0.63 ≦ κ ≦ 1.12) and η/τℓ = const (0.73 ≦ ℓ ≦ 1.06), are experimentally derived. Both exponents, κ and ℓ, depend on the M̄w of the oligomer. The lower M̄w oligomer has the larger value of κ. The κ value is close to unity for the low M̄w oligomer, which agrees with Walden's rule, σ·.η = const, applicable to most low mol wt liquids. The ℓ value is near unity for the epoxide oligomer with higher M̄w than 2000, which means that the melt viscosity is proportional to the dielectric relaxation time. The low M̄w oligomer (M̄w < 2000), on the other hand, has a smaller value of ℓ below unity. The result indicates that the melt viscosity is not proportional to the dielectric relaxation time for the low M̄w epoxide oligomer, whose dielectric α‐relaxation is not governed by the Debye equation. © 1993 John Wiley & Sons, Inc.
Surface graft polymerization of ionic monomers onto poly(ethylene terephthalate) by UV‐irradiation without degassing
Authors: Uchida Emiko , Uyama Yoshikimi , Ikada Yoshito 
Published: April 2003

AbstractGraft polymerization of anionic and cationic monomers was performed onto the surface of poly(ethylene terephthalate) (PET) film with a simultaneous UV irradiation method, but using no photo‐sensitizer. To effect graft polymerization, the PET film was immersed in an aqueous solution containing a monomer and periodate (NaIO4) of appropriate concentrations, followed by UV irradiation without degassing. The monomers used were 2‐acrylamide‐2‐methylpropane sulfonic acid and acrylic acid as anionic and N,N‐dimethyl aminopropyl acrylamide and dimethyl aminoethyl methacrylate as cationic monomer. The role of NaIO4 at the polymerization was to make the concentration of oxygen dissolved in solution zero by the photochemical reaction with the oxygen. The surface structure of grafted films was characterized by their contact angle, dyeing, X‐ray photoelectron spectroscopy, and zeta potentials. Graft polymerization took place, not merely on the outermost surface, but also within the thin surface region of the PET film without any change in bulk properties. © 1993 John Wiley & Sons, Inc.
TG–Temperature property (TgTP) diagram for thermosetting systems: Anomalous behavior of physical properties vs. extent of cure
Authors: Wang Xiaorong , Gillham John K. 
Published: April 2003

AbstractThe relationships between the isothermal physical properties in the glassy state of amorphous thermosetting crosslinked polymers and chemical conversion are anomalous and complex. In this manuscript, a generalized framework for correlating the basic physical properties of a high‐Tg thermosetting amine/epoxy system vs. extent of cure at isothermal temperatures from above Tg to deep in the glassy state is reported in terms of the Tg‐Temperature Property (TgTP) Diagram. The framework arises from consideration of the isothermal shear modulus and the isothermal physical aging rate vs. extent of cure, both of which display maxima and minima throughout a wide range of temperatures below Tg. Use of Tg as a direct measure of conversion results in linearization of the relationships between the temperatures of the maxima and minima of the physical properties and extent of cure in the TgTP Diagram. The anomalous behavior is related to specific phenomena, such as the glass transition (vitrification) and the glassy‐state β‐transition (Tβ), the temperatures of which change with conversion, and also to gelation. The different types of behavior of a property of the material vs. extent of cure correspond to different regions in the diagram. Such simple diagrams are intellectually useful for understanding the properties of materials for both undercured materials (with change of conversion) and fully cured materials (with change of stoichiometric ratio). © 1993 John Wiley & Sons, Inc.
An X‐ray investigation of terminally carboxyl oligo (ethylene oxide) monomethyl ethers‐substituted side‐chain liquid crystalline polysiloxanes
Authors: Jeng Gow‐Pyng Cheng , Kuo Jen‐Feng , Chen Chuh‐Yung 
Published: April 2003

Abstract4′‐[Oligo(ethylene oxide) monomethyl ether carbonyl] biphenyl‐4‐yl 4‐(alkenyloxy) benzoate side‐chain liquid crystalline (LC) polysiloxane polymers with various lengths of a terminal group and spacer were prepared. The mesophase structure and transition temperature of those polymers were investigated using methods of X‐ray diffraction, polarized optical microscopy, and differential scanning calorimetry, respectively. The mesophases of the polymers were smectic ones. The layer spacing d1s and the side‐chain distance of d2s obtained were around 29–34 Å and 4.4–4.6 Å, respectively. d1s were much shorter than twice the lengths of the side chains presumed in the fully extended conformation. Hence, the two‐layer end‐on packings or the packing with overlapping of tails model seemed not able to interpret the mesophase structure of those polymers studied. The effects of temperature on the mesophase microstructure of 4′‐[ethylene oxide monomethyl ether carbonyl] biphenyl‐4‐yl 4‐(pentenyloxy) benzoate side‐chain LC polysiloxane polymer were also studied using the X‐ray diffraction method. It was found that both d1 and d2 of the polymer in the mesophase temperature range became shorter with decreasing temperature and the long‐and short‐range order could remain, to some extent, at temperatures above the isotropic transition temperature and temperatures below the melting temperature. © 1993 John Wiley & Sons, Inc.
Application of the microbond technique. IV. Improved fiber–matrix adhesion by RF plasma treatment of organic fibers
Authors: Biro David A. , Pleizier Gerald , Deslandes Yves 
Published: April 2003

AbstractThe microbond technique is a modification of the single‐fiber pullout test for measuring interfacial shear strength. Briefly, a cured microdroplet of material is debonded in shear from a single fiber. Ultra‐high modulus polyethylene (Spectra) fibers and aramid fibers (Kevlar) were treated using a radio frequency plasma in order to increase the interfacial bond between the fibers and an epoxy resin. The treated fiber surface was subsequently analyzed by X‐ray photoelectron spectroscopy (XPS). Plasma treatment resulted in an increased concentration of oxygen containing functionalities on the fiber surface. The interfacial shear strength as determined by the microbond test increased by 118% for the Spectra fibers and by 45% for the Kevlar fibers with the same epoxy resin. Scanning electron microscopy indicated little change of the surface topography of either fiber following plasma treatment. Effects of friction and surface composition of the plasma‐treated fibers is discussed. © 1993 John Wiley & Sons, Inc.
Densimetry for on‐line conversion monitoring in emulsion homo‐ and copolymerization
Authors: Canegallo Stefano , Storti Giuseppe , Morbidelli Massimo , Carrà Sergio 
Published: April 2003

AbstractThe use of on‐line densimetry to monitor conversion in batch emulsion polymerization reactors are investigated. Some characteristics of the sampling circuit connecting the reactor to the densitometer, which allow one to obtain reliable on‐line estimations of monomer conversion in the whole range of conversion, are discussed in detail. Moreover, the amount of collected data provides a practically continuous monitoring of the system evolution in time, which allows one to estimate directly the rate of conversion as a function of time. The technique has been applied both to homopolymerization systems [i.e., styrene (STY) and methyl methacrylate (MMA)] as well as to copolymerization systems [i.e., STY–MMA, acrylonitrile (ACN)–MMA, vinyl acetate (VAC)–MMA]. In the latter case, the density measurements are combined with a reliable model which provides for polymer composition as a function of conversion, in order to obtain accurate measurements of monomers conversion. © 1993 John Wiley & Sons, Inc.
Statistical mechanics of “dual‐mode” sorption in polyimides
Authors: Silverman B. D. 
Published: April 2003

AbstractA statistical mechanical description of the gas takeup or sorption in polyimides below their glass transition temperature is proposed. The model treated is formally similar to Fowler's early model of monolayer adsorption of gases on solid surfaces. It is expected to be appropriate for polymers exhibiting a significant degree of crystallization, e.g., the aromatic polyimides at temperatures well below their glass transition temperature. The model assumes that the penetrant gas molecules bind to a spectrum of states characterized by a distribution of binding energies. If it is assumed that the penetrant molecules bind to the polymer with only two well‐defined interaction energies, namely, zero as well as some particular finite value, a “dual‐mode” expression for sorption is obtained. It is pointed out that this “dual‐mode” or “two‐state” model is not consistent with some recent data obtained on carbon dioxide sorption in a polyimide. Two other simplified models are examined, a “uniform‐density‐of‐states” model and a “three‐state” model. The present treatment yields explicit expressions for the temperature dependence of the sorption parameters. This dependence reflects the thermodynamic redistribution of penetrant molecules among the available fixed density‐of‐states as the temperature is varied. It is pointed out that the temperature dependence of the Langmuir capacity constant obtained from nonlinear least squares fitting the standard “dual‐mode” sorption expression to the polyimide sorption data may lead to an erroneous inference concerning the decrease in “unrelaxed volume” as the temperature is increased from well below the glass transition temperature of the polymer. The “three‐state” model yields sorption isotherms that parallel the data of Sada et al. closely. This suggests the presence of multiple carbon dioxide binding sites in the polyimide. © 1993 John Wiley & Sons, Inc.
The modification of porous chromato‐gel surface for liquid chromatography by poly(4‐vinylpyridine) microgels
Authors: Ma Guanghui , Fukutomi Takashi , Nozaki Shohei 
Published: April 2003

AbstractA porous chromato‐gel for liquid chromatography was modified by fixing poly(4‐vinylpyridine) (P4VP) microgels of homogeneous size on its surface, and the microgels were further quarternized by using iodomethane or bromoacetic acid, in order to vary the chromatographic characters of the original chromato‐gel. The character of the porous chromato‐gel before and after modification was investigated by the retention volume (Ve) of dextran and pullulan standards with various molecular weights (MW: 2 × 10–2 × 106 g/mol). It was found that a single layer of microgels had been fixed compactly on the surface of the chromato‐gel, and the retention volume (Ve) and the limit exclusion molecular weight (LEMW) [the molecular weight where the d(Ve)/d(MW) became maximum] were affected remarkably by the sizes and chemical characters of the fixed microgels. The retention volume and LEMW decreased when the pore size formed by microgels was smaller than the hole size of the chromato‐gel, while the reverse result was obtained when the pore size formed by the microgels became larger than the hole size of the chromato‐gel. After the microgels were quarternized, the retention volume decreased further. Furthermore, the chromato‐gel quarternized by bromoacetic acid showed excellent chromatographic character. This study provided an advantage in that the chromatographic characters of the chromato‐gel can be varied and improved easily. © 1993 John Wiley & Sons, Inc.
Optimization of covalently coupling enzymes to polymeric membranes: EPR studies of papain
Authors: Zhuang Ping , Butterfield D. Allan 
Published: April 2003

AbstractIn an effort to better understand bioreactor systems, papain (EC 3.4.22.2) was covalently immobilized onto vinyl alcohol/vinyl butyral copolymer (PMB) membrane by means of glutaraldehyde (GA), 1,1'‐carbonyldiimidazole (CDI), or 2‐fluoro‐1‐methylpyridinium toluene‐4‐sulfonate (FMP). Various kinetic and performance characteristics of the immobilized papain were evaluated. It was found that the characteristics of the membranebound papain depended on the immobilization methods. The CDI‐ and FMP‐immobilized papain bioreactors showed better storage and thermal stability than did the GA‐immobilized papain bioreactor, although the apparent Michaelis constant, Km, of the GA‐immobilized papain was closer to the free enzyme than to the corresponding CDI‐ and FMP‐immobilized enzymes. In separate experiments, a 6‐carbon spacer was inserted between the membrane surface and the covalently bound enzyme. It was found that the insertion of a spacer reduced the disturbance of the enzyme systems, resulting in Km values intermediate between the free and directly bound enzymes for all three immobilization methods. Electron paramagnetic resonance spectroscopy was also used to investigate the conformational change and the active site structure of papain. It was found that the active site SH group of papain immobilized with a 6‐carbon spacer had faster motion than that of directly bound enzyme, but slower motion than that of the free enzyme. With both direct‐coupling and with a spacer, the SH group motion at the active site of papain by CDI and FMP immobilizations was similar, but slower than the corresponding GA immobilization. The conformational changes of the active site of papain upon immobilization with and without a spacer were in agreement with the functional properties of the enzyme. There was a good correlation between the motion of spin‐labeled cysteine in the active site of papain and kinetic properties of this protease: As motion slowed, Km increased and Vmax decreased. Of the immobilization procedures used, GA immobilization with a spacer yielded kinetic and structural characteristics most similar to the free enzyme while providing increased stability and reusability relative to the latter. © 1993 John Wiley & Sons, Inc.
The cure of epoxy novolacs with aromatic diamines. II. Statistical parameters of the resulting networks
Authors: Oyanguren P. A. , Williams R. J. J. 
Published: April 2003

AbstractThe buildup of the network arising from the reaction of an epoxy novolac (derived from a phenol—formaldehyde novolac resin), with 4,4'diaminodiphenylsulfone (DDS), was modeled using a kinetic‐statistical procedure that takes into account (i) the complex structure of the starting novolac, (ii) the actual polymerization kinetics including the different reactivity of primary and secondary amine hydrogens, and (iii) the formation of intramolecular cycles. Predictions of gel conversion and sol fraction were in excellent agreement with experimental results. Glass transition temperaturesTg's of networks prepared at different stoichiometries were predicted using Nielsen's equation (J. Macromol. Sci.‐Rev. Macromol. Chem.,C3, 69, 1969) and the concentration of elastic chains arising from the model. Theoretical predictions explained the presence of a maximum in the experimentalTgfor formulations containing a 20% amine excess. Experimental values ofTgas a function of conversion, for stoichiometric samples, were correlated using a model proposed in the literature. © 1993 John Wiley & Sons, Inc.
The interaction of water with polyurethanes containing block copolymer soft segments
Authors: Schneider N. S. , Illinger J. L. , Karasz F. E. 
Published: April 2003

AbstractThe saturation water uptake and nonfreezing water, determined as a function of temperature in a polyurethane containing the pure polyethylene oxide soft segment (I) and in polyurethanes containing block copolymer polyethylene oxide/polypropylene oxide soft segments (II), show significantly different behavior. In sample I, the water content and nonfreezing water are only weakly dependent on temperature from 276 to 333 K. In the samples based on II, with various ratios of the hydrophilic and hydrophobic segments, there is a strong decrease in solubility with temperature and a steep drop above 303 K. The nonfreezing water exhibits a parallel trend. This behavior is interpreted in terms of the temperature‐dependent phase compatibility of the polyethylene oxide and polypropylene oxide segments of II. © 1993 John Wiley & Sons, Inc.