bluuebunny/crossref_metadata_2025 huggingface dataset:
Induced accelerated autocondensation of polyflavonoid tannins for phenolic polycondensates. I. 13C‐NMR, 29Si‐NMR, X‐ray, and polarimetry studies and mechanism
Authors: Meikleham N. , Pizzi A. , Stephanou A.
Published: April 2003

Polyflavonoid tannins have been found to autocondense and harden when in presence of small amounts of SiO2 at high pH. Small amounts of boric acid and AICI3 were found to have the same effect. The mechanism of tannin autocondensation to hardening was found to depend on the Lewis acid behaviour of the additives used. Such mechanism involves Lewis acid acceptance of electrons from the ether oxygen of the flavonoid unit pyran ring with subsequent facilitation of base‐induced heterocycle opening. The reactive C2 site created by heterocycle opening proceeds to autocondense with the reactive A‐ring of a flavonoid unit on another chain denying to the flavonoid the possibility of intramolecular rearrangements to catechinic acid and phlobatannin which occur in model compounds. Si has been shown to pass through a coordination state of 5, by CP‐MAS 29Si‐NMR. The portion of Si, which has not been able to complete the reaction due to premature hardening, remains attached to the flavonoids, in this coordination state, in the hardened network. The Si portion, which has completed the reaction and caused the hardening, reverts instead to SiO2 and is detached from the flavonoid. The SiO2, H3BO3, and AICI3 mechanism shows that their presence also reverses the relative facility of cleavage between interflavonoid bond and heterocycle opening in mainly procyanidin and profisetinidin tannins. © 1994 John Wiley & Sons, Inc.
Effect of the low‐temperature relaxation on toughness of cured epoxy resins
Authors: Ochi Mitsukazu , Ikegawa Kayo , Ueda Shigehisa , Kotera Kazuhiro
Published: April 2003

The relation between the magnitude of low‐temperature relaxation and toughness was investigated for epoxy resins cured with some position isomers of naphthalenediols. A well‐defined relaxation was observed near room temperature for a system cured with 2,6‐dihydroxynaphthalene. The relaxation was denoted here as the β′‐relaxation. The values of the stress intensity factor, Kc, in this system was considerably higher than those of the other cured systems in the temperature region over the β′‐relaxation temperature. This is explained by the increase in the plastic deformation region at the crack front with an increase in the temperature near the crack tip caused by the presence of the β′‐relaxation. © 1994 John Wiley & Sons, Inc.
Composition control in emulsion copolymerization. II. Application to binary and ternary systems
Authors: Canegallo Stefano , Canu Paolo , Morbidelli Massimo , Storti Giuseppe
Published: April 2003

The optimal monomer feed policy for producing in a semibatch reactor a given amount of polymer with constant instantaneous composition, in the minimum reaction time and complete monomer depletion, as developed in Part I of this work, has been implemented experimentally. Conversion has been monitored on‐line using a densitometer suitably connected to the laboratory reactor. The procedure has been applied to two binary and one ternary systems. The composition of the polymer produced has been characterized through various experimental techniques. The composition control procedure is insensitive to most types of irreproducibilities that arise in batch reactions performed in industrial appli‐fjcations. © 1994 John Wiley & Sons, Inc.
Crosslinking by etherification of bisepoxide with divalent metal salts of p‐aminobenzoic acid
Authors: Takechi Shicetoshi , Matsuda Hideaki
Published: April 2003

Crosslinking by etherification of a large excess of bisepoxide with divalent metal salts of p‐aminobenzoic acid was investigated. Mg and Ca were selected as the divalent metal salts, and bisphenol A diglycidyl ether was the bisepoxide used. In the crosslinking reactions, the metal salts exhibited catalytic activity for the etherification, with the Ca salt showing higher catalytic activity than the Mg salt. Hence, the etherification proceeded via an ionic mechanism in which carboxylate anion is concerned. The orders of reaction with respect to carboxylate anion concentration were one order for the both systems. The overall ac‐tivation energies of the crosslinking reaction were 13.4 kcal/mol for the system containing Mg and 23.0 kcal/mol for the system containing Ca. The metal‐containing cured resins obtained showed higher flexural strength, Rockwell hardness, and compressive strength than the resins without metal. Heat distortion temperature and glass transition temperature determined by dynamic mechanical properties increased with an increase in the metal salt content in the feed. Thermal decomposition was accelerated by the incorporated metal. In addition, the metal‐containing cured resins have high boiling water and water resistances.
Characterization of crosslinking of random polymer network by rheological and equilibrium swelling data
Authors: Espinasse I. , Cassagnau P. , Bert M. , Michel A.
Published: April 2003

The transesterification reaction in the molten state of ester groups of ethylene vinyl acetate (EVA) copolymers and ethylene acrylic ester (EMA) copolymers has been used to crosslink the chains of this polymeric system. The relative EVA copolymers (or EMA copolymers) concentration dependence of the network formation by co‐crosslinking of EVA/EMA miscible blends has been assessed. EVA/EMA networks were characterized by swelling experiments, rheological measurements, and determination of the extent of the reaction through a chromatographic technique. All results can be compared in a master curve. The influence of the polydispersity and the microstructure of EVA and EMA samples was put in evidence. On the other hand, a scaling law (v2∼Mc−3/5) was observed in agreement with predictions of the Flory‐Rhener expression. © 1994 John Wiley & Sons, Inc.
Fluorinated poly(butylene terephthalate): Preparation and properties
Authors: Toselli M. , Pilati F. , Fusari M. , Tonelli C. , Castiglioni C.
Published: April 2003

Fluorinated poly(butylene terephthalate) (PBT) can be easily prepared using a telechelic perfluoropolyether (PFPE) as a comonomer. The functional groups of the PFPE react completely with other monomers, but the distribution of the PFPE blocks is not homogeneous and in the final polymeric material there is a significant fraction of PFPE bonded to very short segments of polyester. Due to the very poor miscibility of PFPE and PBT, the PFPE is present as a separate phase dispersed in an almost pure PBT matrix. Accordingly, both thermal and mechanical properties of PBT are little affected by the PFPE. The presence of PFPE induces a slight improvement on the fracture resistance and on surface properties such as wear resistance and coefficient of friction. © 1994 John Wiley & Sons, Inc.
Single‐step dyeing and finishing treatment of cotton with 1,2,3,4‐butanetetracarboxylic acid
Authors: Choi Hyuang‐Min , Srinivasan Magesh , Morris Nancy M.
Published: April 2003

A single‐step dyeing and finishing (SDF) process was developed to eliminate dyeing problems associated with cotton crosslinked by polycarboxylic acid such as 1,2,3,4‐butanetetracarboxylic acid (BTCA). This process consisted of several steps: (a) impregnation of the fabric by the bath containing BTCA, dye, and catalyst; (b) drying; and (c) curing at high temperature. Color strength (K/S) and dye fixation of cotton treated by the SDF process were excellent, especially with reactive dyes containing mono‐ or dichlorotriazinyl compounds and, in some cases, were higher than those of the sample dyed by a conventional batch process without finishing treatment. The presence of dye in the SDF process did not interfere with crosslinking of cotton. We believed that the reaction occurred between carboxyl groups of BTCA and s‐triazinyl groups in reactive dyes in the presence of imidazole and other catalyst. FTIR, Raman, and X‐ray fluorescence spectroscopies were used to confirm the mechanism of dye fixation. Elemental analysis also supported this mechanism. The SDF process can be an excellent way to dye fabric that also requires crosslinking treatment for smooth drying appearance. © 1994 John Wiley & Sons, Inc.
Slow crack growth in polyethylene: A novel predictive model based on the creep of craze fibrils
Authors: Rose L. J. , Channell A. D. , Frye C. J. , Capaccio G.
Published: April 2003

An extensive series of homopolymers and copolymers has been investigated to test earlier indications of a possible link between resistance to slow crack growth and creep of macroscopic oriented samples. It was found that in the majority of cases a good correlation exists between a single creep parameter and slow crack growth. The existence of such a correlation supports the model presented, in which crack growth is primarily controlled by the creep of fibrils spanning the craze zone. The limit of improvement achievable by increasing molecular weight and the greater effectiveness of short‐chain branching to improve fibril creep have been highlighted. © 1994 John Wiley & Sons, Inc.
Water absorption effects on the thermal transition and stiffness of ethylene ionomers
Authors: Tachino Hitoshi , Hara Hisaaki , Hirasawa Eisaku , Kutsumizu Shoichi , Yano Shinichi
Published: April 2003

Changes in the thermal transition and stiffness of ionomers occuring during aging or water absorption were investigated. Ionomers used in this study are Na, K, Mg, and Zn salts of poly(ethylene‐co‐methacrylic acid) (EMAA), whose methacrylic acid unit is 5.4 mol %. It was found that ionomer stiffness is subject to water absorption and the effect differs with the neutralizing cations. Water absorption effects on the thermal transition, measured by differential scanning calorimetry (DSC), indicate that there are no significant changes in the higher‐temperature endotherm assigned to a melting of polyethylene (PE) crystallities. However, the lower‐temperature endotherm, which we attribute to an order‐disorder transition of ionic aggregates (Ti), exhibits significant changes upon water absorption. The mechanism of the water absorption effects on the thermal transition and stiffness is described. © 1995 John Wiley & Sons, Inc.
Recognition of amino acids by membrane potential of immobilized globulin membranes
Authors: Yun K.‐S. , Tak T.‐M. , Shimada S. , Nakagawa T. , Hara M. , Higuchi A.
Published: April 2003

The shifts in membrane potential, caused by the injection of some amino acids into a permeation cell, were measured using immoblized γ‐globulin membranes. The shifts in membrane potential were observed to be positive or negative when the isoelectric point of each amino acid injected into the cell was less or higher than 6.0. The potential response caused by the injection of each amino acid shows an individual and characteristic curve depending on the amino acid, and the difference in potential curves between D‐aspartic acid and L‐aspartic acid is significantly observed in the immobilized γ‐globulin membranes. The t3/4 value was found to increase in the following order: lysine = glutamic acid <arginine < D‐aspartic acid = asparagine < L‐aspartic acid < histidine < alanine, where t3/4 indicates the time at which 75% of the shifts in membrane potential has been observed. The modified membrane potential theory provides satisfactory explanations for the membrane potential obtained experimentally before and after the injection of L‐alanine, and the theoretical shifts can explain the experimental shifts in membrane potential due to the injection of L‐alanine into the cell. © 1995 John Wiley & Sons, Inc.
Structure and physical properties of grafted jute fiber
Authors: Kundu S. K. , Ray P. K. , Sen S. K. , Bhaduri S. K.
Published: April 2003

Jute fiber was grafted by acrylonitrile and methylmethacrylate monomers in raw and bleached condition. It was also noted that optimum grafting takes place after about 4 h of grafting. It was also noted that in bleached jute fiber, the grafting percentage is higher at all stages of grafting but the tenacity value at the highest add‐on is practically the same as that of raw fiber with much less add‐on. The crystalline orientation of the grafted jute fiber was correlated with the fiber tenacity. The moisture regain (%) of the fiber after grafting showed a decreasing trend with an increase in grafting percentage. No structural change of the fiber occurred due to grafting. © 1995 John Wiley & Sons, Inc.
Size‐exclusion chromatography of cross‐linked superabsorbent polymers
Authors: Cutié Sergio S. , Martin Steven J.
Published: April 2003

Superabsorbent polymers are cross‐linked poly(acrylic acid) with some degree of neutralization. These polymers have found extensive use as constituents in personal care products such as sanitary napkins, incontinent devices, and disposable baby diapers that absorb body fluids. Polymer networks are formed, which makes the chromatography of these materials impossible. In this study, hydrolysis under heat and high pH was used to break the cross‐links, which allows for traditional size‐exclusion chromatography to determine molecular weight and molecular weight distribution of the primary chains. For the chromatography, TSK‐GEL®†PWXL columns and TSK‐GEL PW columns were used. The mobile phase was buffered with sodium chloride and sodium phosphate salts to eliminate ionic interactions. Detection was by refractive index. © 1995 John Wiley & Sons, Inc.
Preparation and characterization of pH‐sensitive, interpenetrating networks of poly(vinyl alcohol) and poly(acrylic acid)
Authors: Gudeman Linda F. , Peppas Nikolaos A.
Published: April 2003

Hydrogels with varying cross‐linking ratio and ionic content were prepared from interpenetrating networks of poly(vinyl alcohol) and poly(acrylic acid). Equilibrium swelling studies were conducted and the average molecular weight between cross‐links, Mc, and mesh size were determined. Hydrogels with large Mc, values were found to swell to a greater extent than those with small Mc values. It was also observed that an increase in Mc yielded faster swelling and deswelling rates, as the rates for membranes with Mc = 18,000 were about twice as fast as were the rates for membranes with Mc = 34,000. Oscillatory swelling behavior was investigated in response to changes in the pH and ionic strength of the swelling medium. A change in pH from 3 to 6 caused an ionization of the hydrogels and an increase in the weight swelling ratio, with a greater increase exhibited by IPNs with a higher ionic content. Increase in pH also caused an increase in the average mesh size. © 1995 John Wiley & Sons, Inc.
A 13C‐NMR analysis method for phenol–formaldehyde resin strength and formaldehyde emission
Authors: Panamgama L. A. , Pizzi A.
Published: April 2003

A method based on the use of 13C‐NMR relative peak intensity ratios for different characteristic chemical groups, known or supposed to contribute to phenol–formaldehyde (PF) resin strength and formaldehyde emission is presented. The method relates results obtained by 13C‐NMR analysis of liquid PF resins with the strength and formaldehyde emission in the resin‐hardened state. Correlation of differnt peak ratio with experimental results allows the proposal of equations relating the sum of different 13C‐NMR peak ratios with the two mentioned physical properties of the same resins in their hardened state. The equations presented appear to have some applied value in predicting physical properties of hardened industrial‐type PF resins from a single 13C‐NMR spectrum of the original liquid resin, as well as to render easier comparison between different PF resin formulations. © 1995 John Wiley & Sons, Inc.
Blends of a PPO–PS alloy with a liquid crystalline polymer
Authors: Viswanathan R. , Isayev A. I.
Published: April 2003

Blends of a PPO–PS alloy with a liquid crystalline polymer have been studied for their dynamic properties, rheology, mechanical properties, and morphology. This work is an extension of our previous work on PPO/LCP blends. The addition of the LCP to the PPO–PS alloy resulted in a marked reduction in the viscosity of the blends and increased processibility. The dynamic studies showed that the alloy is immiscible and incompatible with the LCP at all concentrations. The tensile properties of the blends showed a drastic increase with the increase in LCP concentration, thus indicating that the LCP acted as a reinforcing agent. The tensile strength, secant modulus, and impact strength of the PPO–PS/LCP blends were significantly higher than that of PPO/LCP blends. Morphology of the injection molded samples of the PPO–PS/LCP blends showed that the in situ formed fibrous LCP phase was preserved in the solidified form. A distinct skin–core morphology was also seen for the blends, particularly with low LCP concentrations. The improvement of the mechanical properties of the blends is attributed to these in situ fibers of LCP embedded in the PPO–PS matrix. The improvement in the properties of PPO–PS/LCP over PPO/LCP is also attributed to the addition of the PS which consolidates the matrix. © 1995 John Wiley & Sons, Inc.
Surface modification of poly(vinyl chloride) with poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers
Authors: Gorelova M. M. , Pertsin A. J. , Muzafarov A. M. , Gritsenok O. T. , Vasilenko N. G.
Published: April 2003

X‐ray photoelectron spectroscopy is used to study the surface segregation of siloxane in dilute blends of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers in poly(vinyl chloride)(PVC). The graft copolymers are found to be extremely efficient surface modifiers, which form, when added in amounts of 0.5% or more, a continuous siloxane overlayer on the surface of PVC. © 1995 John Wiley & Sons, Inc.
The effect of a liquid isothermal bath in the threadline on the structure and properties of poly(ethylene terephthalate) fibers
Authors: Wu Gang , Zhou Qiang , Chen Jiunn‐Yow , Hotter Joseph F. , Tucker Paul A. , Cuculo John A.
Published: April 2003

The process of melt‐spinning poly(ethylene terephthalate) (PET) filament at high speeds was modified through the inclusion of a liquid isothermal bath (LIB) in the spinline. A wide range of positions, temperatures, and depths associated with the operation of the LIB were utilized in this study. The structural characteristics and mechanical properties of the as‐spun fibers were characterized by birefringence, wide‐angle X‐ray diffraction (WAXD), infrared spectroscopy, and tensile testing. Experimental results showed that the structure and mechanical properties of the as‐spun fibers were significantly influenced by the LIB operating conditions. The as‐spun fibers prepared under optimum LIB conditions exhibit high birefringence and excellent mechanical properties. Results suggest the development of a critical value of threadline stress that is determined primarily by LIB depth and take‐up velocity. Below this critical value, raising of LIB temperature, LIB depth, and take‐up velocity resulted in increases of the apparent crystallite size, sample crystallinity, and both the crystalline and amorphous orientation. As would be expected, the mechanical properties of the fiber samples were improved in a corresponding manner. Above this critical stress value, molecular chains in the amorphous phase are stretched tautly, but the crystal growth process is restricted, resulting in a decrease in crystallite size and crystallinity, as well as a continued increase in mechanical properties. The fiber properties were also found to be very responsive to the relative location of the LIB. A unique structure, believed never before obtained in a one‐step high‐speed PET melt‐spinning process, has been achieved that combines high amorphous orientation, low crystallinity, and high tenacity. © 1995 John Wiley & Sons, Inc.
Plasma polymerization of copper phthalocyanines and application of the plasma polymer films to NO2 gas sensor device
Authors: Inagaki N. , Tasaka S. , Ikeda Y.
Published: April 2003

Four copper phthalocyanines without substituent (CuPc) and with chlorine (CuPc‐Cl), hydroxymethyl (CuPc‐CH2OH), and phthalimidomethyl substituents (CuPc‐CH2N‐[C(O)]2Ph) were plasma‐polymerized to obtain amorphous and thin films having the extended π‐electron system. The chemical composition of the plasma polymer films was discussed from the data of the electronic spectra, IR spectra, and XPS spectra. The application of the plasma polymer films was discussed with regard to the NO2 sensitivity, the NO2 selectivity, the response time, and the reversibility. Plasma polymerization of CuPc, CuPc‐Cl, CuPc‐CH2OH, and CuPc‐CH2OH gives amorphous films having the extended π‐electron system. In the plasma polymerization process, a part of the extended π‐electron system is broken down. The CH2OH and CuPc‐CH2N[C(O)]2Ph substituents contribute to minimizing the degradation. The Cu atoms liberated from the chelation in the plasma polymerization process exist as CuO in the deposited films. The plasma polymer films of CuPc‐CH2OH and CuPc‐CH2N[C(O)]2Ph show good sensitivity to NO2 molecules. With regard to the sensitivity, the selectivity, the response time and the reversibility, the plasma polymer films are applicable materials to the NO2 sensor device. © 1995 John Wiley & Sons, Inc.
Copolymeric systems with pendant thioxanthone and α‐morpholinoacetophenone moieties as photosensitizing and photoinitiating agents for UV‐curable pigmented coatings
Authors: Angiolini Luigi , Caretti Daniele , Corelli Elena , Carlini Carlo
Published: April 2003

The synthesis and structural characterization of copolymers of 1‐[(2‐acryloyloxy) ethoxycarbonyl]thioxanthone (ATX) with 1‐[4‐(2‐acryloyloxyethylthio)phenyl]‐2‐methyl‐2‐morpholino‐propan‐1‐one (AMMP), as well as ATX, AMMP and n‐butyl acrylate (BA) terpolymers, is reported. These copolymeric systems have been checked in the photoinitiated polymerization in film matrix of the 1,6‐hexanediol diacrylate (HDDA)–BA equimolar mixture under UV irradiation over 380 nm, i.e., under conditions simulating a TiO2‐pigmented acrylic coating formulation, and compared with the corresponding mixture of low‐molecular‐weight structural models 1‐[(2‐isobutyroyloxy)ethoxycarbonyl]thioxanthone (ITX) and 1‐[4‐(2‐isobutyroyloxyethylthio)phenyl]‐2‐methyl‐2‐morpholino‐propan‐1‐one (IMMP). The much higher photoinitiation activity shown by the copolymers is discussed in terms of close vicinity of thioxanthone and α‐morpholinoacetophenone moieties along the backbone, which favors the excitation energy transfer from the former to the latter photosensitive group. © 1995 John Wiley & Sons, Inc.
Crystallization and compatibility of poly(vinyl alcohol)/poly(3‐hydroxybutyrate) blends: Influence of blend composition and tacticity of poly(vinyl alcohol)
Authors: Yoshie Naoko , Azuma Yoichiro , Sakurai Minoru , Inoue Yoshio
Published: April 2003

Compatibility of a crystalline/crystalline polymer blend, poly(vinyl alcohol) (PVA)/poly(3‐hydroxybutyrate) (PHB), was studied by high‐resolution solid‐state 13C‐NMR spectroscopy. The 1H T1 measurement demonstrated that both the compatibility and the domain size depend on the composition of the blend. The PVA/PHB blend is compatible only when the blend contains a large amount of PVA. The domain sizes of the compatible blend are less than 200 Å. In the pulse saturation transfer (PST) MAS NMR spectra, the carbonyl carbon resonance from PHB showed a downfield shift, which indicates that the compatibility of the PVA/PHB blends is due to the hydrogen‐bonding interaction in the amorphous phase. The DSC measurement showed that the compatible blends adopt low crystallinity for both PHB and PVA. The crystallization in these blends is likely to be distributed by the hydrogen‐bonding interaction in the amorphous phase. The compatibility of PVA/PHB is also affected by the tacticity of PVA. The compatible composition range of the syndiotacticrich PVA/PHB blend is wider than that of the atactic‐PVA/PHB blend. It is likely that the capacity to form the hydrogen bond depends on the tacticity of PVA. © 1995 John Wiley & Sons, Inc.
Morphology and tensile properties of styrene–butadiene copolymer reinforced asphalt
Authors: Blanco R. , Rodríguez R. , García‐Garduño M. , Castaño V. M.
Published: April 2003

Morphology and tensile properties of several styrene‐butadiene copolymer reinforced asphalts have been investigated. In all cases, the raw materials were commercial samples; for the styrene‐butadiene copolymer, a branching (nonlinear) block polymeric chain of high molecular weight was used. On the other hand, the asphalt was a nonoxydized commercial sample. The raw materials were characterized prior to making the composite. The morphology and mechanical properties of composites obtained at different chemical compositions were determined, and a comparison of these experimental results to different models, according to the composite morphology, is shown. © 1995 John Wiley & Sons, Inc.
Phenomenology of surface failure of poly(methylmethacrylate) resulting from rolling contact fatigue
Authors: Hosseini S. M. , Stolarski T. A.
Published: April 2003

Results of phenomenological study into the forms of surface failure of poly(methylmethacrylate) (PMMA) are presented. Surface failure of the polymer resulted from rolling contact fatigue produced in a model configuration consisting of a PMMA disc with nominally flat surface loaded against three steel balls able to roll free over the surface of the disc. It was found that the performance of the polymer under the test conditions used is influenced by lubricating medium and the main form of failure is of surface fatigue type. © 1995 John Wiley & Sons, Inc.
Emulsion copolymerization of vinyl esters in continuous reactors: Comparison between loop and continuous stirred tank reactors
Authors: Abad Carlos , De La Cal José C. , Asua José M.
Published: April 2003

The high solids emulsion copolymerization of vinyl acetate and veova 10 was studied in a continuous loop reactor and in a continuous stirred tank reactor (CSTR) in an attempt to elucidate the similarities and differences between these reactors. Reactions were carried out under comparable conditions, namely, similar macromixing and the same feed composition and space time. The behavior of both reactors was almost the same when the heat generation rate was low; otherwise, thermal runaway occurred in the CSTR whereas the loop reactor temperature was easily controlled. © 1995 John Wiley & Sons, Inc.
Thermal stability studies of transparent conducting polyaniline composite films on their conductivity and optical spectra
Authors: Byun Sung Weon , Im Sung Soon
Published: April 2003

The thermal stability of highly transparent and conducting polyaniline–Nylon 6 (PAn‐N) composites films doped with various protonic acids such as hydrochloric acid (HCI), benzenesulfonic acid (BSA), sulfosalicylic acid (SSA), and p‐toluenesulfonic acid (TSA) was investigated at different elevated temperatures under air atmosphere. Two different degradation kinetic processes of electrical conductivity were found depending on the species of protonic acids. The conductivity degradation of PAn‐N composite films doped with SSA and TSA were found to obey first‐order reaction kinetics, while that of the other dopants was found to follow multiorder kinetics. Spectroscopic studies revealed that the thermal de‐doping process of doped composite films, which reversed the doping process, took place without major structural modifications of the polyaniline in the composite system but was not completely reversible. From the differential scanning calorimetry (DSC) study, the crystal structure of the composite films was found to be affected by the formation of polyaniline in matrix polymer and depended on the types of dopant species. © 1995 John Wiley & Sons, Inc.
Polymer‐anchored metal complexes. III. Preparation, structural, thermal stability, dielectric, and conductivity characterization of polycondensates from Cu(II)–1, 10‐phenanthroline and trimellitic anhydride/pryromellitic dianhydride
Authors: Biswas Mukul , Mukherjee Amit
Published: April 2003

Trimellitic anhydride and pyromellitic dianhydride have been polycondensed with Cu(II)–phenanthroline complex as a comonomer in the presence of anhydrous ZnCl2 under selective conditions. Elemental diffuse reflectance and infrared spectroscopic and X‐ray diffraction (XRD) analysis data of these polymers have been correlated with the tentative structure Proposed for these polycondensates. Thermal stability and dielectric and conductivity characteristics of these polycondensates have been evaluated to understand the effect of the ligand and the anhydride moieties on these properties. Unlike the polymer‐anchored 3d‐metal complexes, these polycondensates fail to initiate the cationic polymerization of N‐vinylcarbazole. © 1995 John Wiley & Sons, Inc.
Effects of processing parameters on material properties of mechanically processed polyamide
Authors: Pan J. , Shaw W. J. D.
Published: April 2003

A semicrystalline polyamide polymer was processed using a new technique known as mechanical alloying. The material processed by this technique was first introduced into a high‐energy ball mill and ground over long periods of time, resulting in the production of extremely fine powders. These powders were subsequently consolidated well below the materials' melting‐point temperature. The effect of processing parameters including mechanical milling time, consolidation temperature, and the length of consolidation time were studied fairly extensively. The investigation shows that polyamide powders are continually refined with increasing mechanical milling time and the resulting materials have improved mechanical properties. The influence of both consolidation temperature and the length of consolidation time on material properties indicate that materials with higher density, crystallinity, hardness, strength, and ductility are produced when consolidated using higher temperatures and longer times. © 1995 John Wiley & Sons, Inc.
Real‐time monitoring of diffusion in polymer films using fluorescent tracer
Authors: Krongauz V. V. , Mooney W. F. , Palmer J. W. , Patricia J. J.
Published: April 2003

A method for real‐time nondestructive monitoring of small molecules diffusion in polymeric films was developed. The method was based on detection of a fluorescent tracer eluting from the investigated polymer film into the solution in which this film was immersed. The kinetics of the tracer elution, monitored by the increase in solution fluorescence intensity, was used to deduce tracer diffusivity in polymer film. The data were treated using a straightforward mathematical model, describing diffusion from an infinite plane of a certain thickness immersed into a finite solvent bath. Fluorescent 7‐diethylamino‐4‐methyl coumarin was used as a tracer. The diffusion of this tracer within plasticized poly(methyl methacrylate) and styrene‐isoprene‐styrene block copolymer matrices was monitored. The diffusion coefficients equal to 2 × 10−9 cm2/s and 1 × 10−9 cm2/s, respectively, were obtained. © 1995 John Wiley & Sons, Inc.
Grafting maleic anhydride and comonomers onto polyethylene
Authors: Samay Geza , Nagy Tibor , White James L.
Published: April 2003

Grafting dicarboxylic anhydrides onto polyolefins has great practical importance. The process of grafting maleic anhydride onto high‐density polyethylene in the presence of various comonomers in an intermeshing corotating twin‐screw extruders was studied. Three types of comonomers were investigated: (i) vinyl monomers, including styrene and methacrylic acid; (ii) esters of dicarboxylic acids forming succinic groups after grafting, such as fumaric acid; and (iii) esters of fumaric and maleic acid and ethylenically unsaturated cyclic dicarboxylic anhydrides, such as Diels–Alder adducts of maleic anhydride; and (iv) dienes and dodecenyl succinic anhydride. © 1995 John Wiley & Sons, Inc.
Gas permeation property of polyaniline films
Authors: Hachisuka Hisao , Ohara Tomomi , Ikeda Ken‐Ichi , Matsumoto Kenji
Published: April 2003

We examined the influence of polyaniline (PAn)'s unit sequence and doping with low molecular weight dopants or polymer dopants on permeation property. It was found that CO2 permeability was increased by the formation of a quinonediimine unit in PAn with the oxidation. CO2 sorption amount of PAn was decreased by oxidation. The increase of CO2 permeability with oxidation, therefore, resulted from the increase of diffusivity, which was attributable to morphological variation by the increase of a quinonediimine unit. The permselectivity of PAn films was found to be remarkably improved by doping. In particular, the selectivity value of the PAn film doped with polyvinyl sulphonic acid as a polymer dopant went up to over 2,000. This remarkable increase of selectivity was found to result in the increase of selectivity, depending on diffusivity. It was also found that the permselectivity of the PAn film doped by polymer dopants was surpassed, as compared with that doped by low molecular dopants. © 1995 John Wiley & Sons, Inc.
Polarity measurements in block copolymers (polyurethaneimides) and correlation with their pervaporation features
Authors: Jonquières Anne , Roizard Denis , Cuny Joël , Vicherat André , Lochon Pierre
Published: April 2003

EtOH/ETBE azeotropic mixture was separated by pervaporation through films of polyurethaneimides (PUI), i. e., alternating block copolymers varying in their structure only by their oligomeric soft blocks. Pervaporation performances strongly depend on the flexible segments: fluxes on the molecular weight and selectivity towards ethanol on the chemical structure in the decreasing order: PEG, PCL, PCD, PTMG, PPG. In order to correlate selectivity with segment polarity, a new solvatochromic polarity probe that was well soluble in PUI was synthesized. Using 13 solvents covering a wide polarity range, Vis λmax of the photochromic indicator open form was linearly correlated with the ET(30) polarity scale. By illumination of the dissolved dye, PUI polarity was investigated in relation to soft segment nature and size. The very high PUI polarity values and their splitting for highest size segments were assigned to preferential probe solvation by interblock urethane junctions combined with phase segregation. Polarity values consistent with the chemical structure of the flexible segments were provided by similar measurements on suitably end‐capped precursors of these segments and were then linearly correlated with the related PUI pervaporation selectivity. © 1995 John Wiley & Sons, Inc.
Effects of polymer matrix and salt concentration on the ionic conductivity of plasticized polymer electrolytes
Authors: Whang Wha‐Tzong , Lu Chou‐Ling
Published: April 2003

Two polar polymers with different dielectric constants, poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide) (PEO), were each blended with a chlorine‐terminated poly(ethylene ether) (PEC) and one of the two salts, LiBF4 and LiCF3CO2, to form PEC plasticized polymer electrolytes. The room‐temperature ionic conductivity of the PEC plasticized polymer electrolytes reached a value as high as 10−4 S/cm. The room‐temperature ionic conductivity of the PVDF‐based polymer electrolytes displayed a stronger dependence on the PEC content than did the PEO‐based polymer electrolytes. In PVDF/PEC/LiBF4 polymer electrolytes, the dynamic ionic conductivity was less dependent on temperature and more dependent on the PEC content than it was in PEO/PEC/LiBF4 polymer electrolytes. The highly plasticized PVDF‐based polymer electrolyte film with a PEC content greater than CF4 (CF4 defined as the molar ratio of the repeat units of PEC to those of PVDF equal to 4) was self‐supported and nonsticky, while the corresponding PEO‐based polymer electrolyte film was sticky. In these highly plasticized PVDF‐based polymer electrolytes, the curves of the room‐temperature ionic conductivity vs. the salt concentration were convex because the number of carrier ions and the chain rigidity both increased with increase of the salt content. The maximum ionic conductivity at 30°C was independent of the PEC content, but it depended on the anion species of the lithium salts in these highly plasticized polymer electrolytes. © 1995 John Wiley & Sons, Inc.
Mechanism of polyphenolic tannin resin hardening by hexamethylenetetramine: CP–MAS 13C‐NMR
Authors: Pizzi A. , Tekely P.
Published: April 2003

Polyflavonoid tannins have been shown by 13C‐NMR to react with hexamethylenetetramine (hexamine) at considerably higher rates than with phenol with the formation of both benzylamine and methylene crosslinks to form hardened resins. Predominantly prodelphinidintype tannins appear to present a much higher proportion of benzylamine bridges than of methylene bridges, while in procyanidin‐type tannins the proportion of the two types of crosslinks appear to be comparable. The greater the nucleophilicity of the flavonoid tannin A‐rings, the greater is the proportion of benzylamine bridges which appear to form. At parity of the type of tannins, the faster the reaction with hexamine, the higher the proportion of benzylamines which appear to form. © 1995 John Wiley & Sons, Inc.
Nonaqueous chromatography of biopolymers by means of their poly(ethylene glycol)‐mediated solubilization in alcohols
Authors: Bromberg Lev
Published: April 2003

Freeze‐drying of aqueous solutions of biopolymers and excess poly(ethylene glycol)s leads to formation of hydrophobic complex. Complexation with PEG increases solubility of low molecular weight DNA, RNA, and several proteins in neat ethanol and methanol. Solubilized nucleic acids can be fractionated, and proteins separated by nonaqueous reversed phase HPLC. © 1995 John Wiley & Sons, Inc.
Preparation and solution properties of ionomer originated from styrene–coumarin copolymer
Authors: Chen Yun , Chen Yung‐Hsiu
Published: April 2003

A novel ionomer was successfully prepared by lactone ring opening of stryrene–coumarin copolymer, containing 9.28 mol % of coumarin, with aqueous NaOH solution. Its solution properties in methanol, including reduced viscosity and surface tension, were investigated as a function of temperature, concentration, and pH value. The reduced viscosities of the ionomer solution decrease smoothly with increasing temperature and concentration. Moreover, the viscosities of the ionomer solution (0.3 g/dL MeOH) are ca. twofold of the copolymer solution (0.3 g/dL THF) between 25 and 45°C. It increases from ca. 0.14 to 0.59 dL/g as pH value decreases from 10.6 to 6, then decreases slightly and reaches a constant value of 0.47 dL/g below pH 4.7. The surface tension of methanol solution decreases with increasing concentration and reaches an asymptotic value of 24.1 dyne/cm as the concentration is above 0.50 g/dL due to the surface‐active effects. These properties can be related to the balance between hydrogen bonding and charge–charge interactions that occur along the ionomer backbone. © 1995 John Wiley & Sons, Inc.
Colorimetric evaluation of thermooxidative degradation of nylon 6 fibers
Authors: Hamza A. A. , El‐Tonsy M. M. , Fouda I. M. , El‐Said A. M.
Published: April 2003

Nylon 6 fibers were annealed in air at 160°C for periods ranging from 1 to 10 h. Their spectral reflectance values were measured. Color parameters, including luminance factor, dominant wavelength, purity, and the color difference between annealed nylon 6 fiber samples and unheated ones were calculated. The observed variations in the colors of samples were assumed due to the thermal and oxidation degradations. The behavior of the color parameters with heating duration was compared with the general kinetic curve of thermooxidative degradation of polymers and the match between them is discussed. The color difference ΔE values is recommended for monitoring the thermooxidative degradation of nylon 6 fibers. © 1995 John Wiley & Sons, Inc.
Cure characterization of triglycidyl epoxy/aromatic amine systems
Authors: Padma A. , Rao R. M. V. G. K. , Subramaniam C. , Nagendrappa G.
Published: April 2003

The curing of triglycidyl para‐aminophenol (TGPAP) epoxy resin with three aromatic amine hardeners, diaminodiphenye sulphone (DDS), pyridinediamine (PDA), and toluenediamine (TDA), has been investigated. A series of iosthermal cures was conducted and analyzed by Fourier transform infrared spectrometry (FTIR) and differential scanning calorimetry (DSC). The chemical reactions occurring during cure were monitored at different temperatures by qualitative and quantitative estimation of different groups in the IR spectra, and the ratio of rate constants (k2/k1) were evaluated. Dynamic DSC analysis of TGPAP/TDA resulted in two exothermal peaks, indicating cure kinetics different from those of TGPAP/DDS and TGPAP/PDA systems, which gave a single exothermal peak. Various kinetic parameters such as total heat of reaction. ΔH′, activation energy Ea, Frequency factor z, and order of reaction n were evaluated for all the three systems. From the initial kick‐off temperatures and activation energy values it was concluded that the rate of curing followed the order TDA > PDA > DDS. The reaction conversions during cure, evaluated from IR analysis, were exactly the same as those obtained from DSC Borchardt–Daniels kinetics. Using this model, the plots of time vs. temperature for different conversions were constructed for all the three systems; on the basis of these, the cure cycles can be fixed. © 1995 John Wiley & Sons, Inc.
Gas transport properties of siloxane polyurethanes
Authors: Pegoraro Mario , Severini Febo , Gallo Raffaele , Zanderighi Luciano
Published: April 2003

Polyurethanes (PUs) were synthesized from toluenediisocyanates (TDIs) and a polymeric diol having polydimethylsiloxane and polyoxyethylene blocks of the ABA type, ended with OH groups. Prepolymers, prepared in toluene solution using ratios [NCO]/[OH] ≥ 2, were crosslinked with triisopropanolamine (TIPA) (ratio [OH]/[NCO] = 1.1) (two‐step process). PUs were also obtained with a one‐step process using, contemporaneously, TDI, block copolymer, and, as crosslinking agent, TIPA or the glyceride of ε‐hydroxyhexanoic acid. Polydimethylsiloxane (PDMSO) was prepared as a reference material. The course of the reaction between block copolymer and TDI was studied by differential scanning calorimetry in the absence and presence of benzoyl chloride (BzCl). Without BzCl, with ratios [NCO]/[OH] > 2, uncontrolled crosslinking side reactions occur. The properties of the PU films obtained with the two methods were studied both for the density of crosslinking and for gas transport properties. The two‐step polymers are less crosslinked than the others and are characterized by higher diffusion coefficients and by higher permeability to gases. The permeability order is 10−9 (N cm3 cm−1 cm−1 cm Hg−1 s−1) for CH4, O2, CO, and N2 and is 10 times higher for CO2. The selectivity for the couple O2/N2 is higher than that obtained with PDMSO films. Considerable selectivities are shown for the couples CO2/N2 and CO2/CO. © 1995 John Wiley & Sons, Inc.
Grafting of acrylonitrile copolymer membranes with hydrophilic monomers for immobilization of glucose oxidase
Authors: Godjevargova T. , Dimov A.
Published: April 2003

Poly(acrylonitrile‐methylmethacrylate‐sodium vinylsulphonate) membranes were subjected to modification by grafting of 2‐dimethylaminoethyl methacrylate (DMAEM) and 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPSA). An Fe2+ H2O2 system was used to initiate the polymerization. Reaction time, temperature, pH, and concentration of an initiator and modifying agent were the variable parameters. Tertiary amino groups, quaternary ammonium groups, and sulfo groups were determined quantitatively by potentiometric titration. The degree of grafting and hydrophilicity and charge density of the modified membranes were studied. Glucose oxidase was immobilized onto modified acrylonitrile copolymer membranes with DMAEM and AMPSA and showed high relative activity. The amount of bound protein and storage of the activity of the immobilized enzyme were determined. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of a monofunctional analog to BIS‐GMA: A dental monomer
Authors: Tamareselvy K. , Rueggeberg F. A.
Published: April 2003

A new monofunctional BIS‐GMA monomer, 4‐(2‐phenyl isopropyl)‐3‐phenoxy‐2‐hydroxy propyl methacrylate (monofunctional‐BIS‐GMA, hereafter abbreviated as MF‐BIS‐GMA) was synthesized as an adduct of 4‐cumylphenol and glycidyl methacrylate for use as a dental monomer. The new monomer was characterized by FTIR, 1H, 13C (attached proton test, APT), UV, HPLC, and GPC. The viscosity and solubility of the new resin are also presented. The results were compared with the difunctional analog, BIS‐GMA (2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxypropoxy)]phenyl propane), which is commercially available and currently used in dental restorative materials. Both monomers were light‐cured using 0.3% camphorquinone and 0.75% 2‐(dimethylamino)ethyl methacrylate as photoinitiators. The extent of monomer conversion and the potential for residual monomer leachability were compared between the two cured resins. The monofunctional resin was found to yield higher monomer conversion values (74 vs. 39%) and lower leachable components (0.03 vs. 30.6 mol %) than those of the difunctional analog. © 1995 John Wiley & Sons, Inc.
Solvent concentration measurement for spin coating
Authors: Gu J. , Bullwinkel M. D. , Campbell G. A.
Published: April 2003

Planarization of spin‐coated polymer films is of great importance for the lithographic process in the microelectronic industry. Solvent retention is an important factor for determining the coating profile during spinning. In this research, solutions of polystyrene in toluene are spin‐coated. The coating concentration during spinning is measured on‐line using a laser interferometry technique. The optical measurement is evaluated by an off‐line gel permeation chromatograph technique. The experiments indicate that a smooth coating surface is required to use the optical method for concentration measurement. The optical technique also provides information regarding the coating surface structure during spinning. © 1995 John Wiley & Sons, Inc.
Viscoelastic properties of short carbon fiber thermoplastic (SBS) elastomer composites
Authors: Ibarra L. , Macías A. , Palma E.
Published: April 2003

The determination of viscoelastic property variation in short fiber‐reinforced composites, as a function of strain, temperature, and frequency, constitutes a useful tool when the existence or the strength of matrix–fiber interfaces are to be examined. In this work, these properties are studied in thermoplastic elastomer matrix materials (SBS) filled with commercial carbon fiber (PAN), oxidated, and subsequently treated with diazide, which generates SO2N3 groups on the fiber surface, theoretically capable of chemical reaction with the polymeric chain. For the composite containing diazide‐treated oxidated fiber, certain phenomena have been proven to occur, such as lesser storing modulus losses in case of increasing strain, greater equivalent interfacial thickness values, and higher mechanical energy loss values than those of composite containing oxidated fiber. An increase in glass transition temperature and apparent activation energy of the relaxation process, with respect to composite‐containing commercial fiber, are also observed, which, altogether, allow for the statement that new matrix–fiber bonds are generated through the sulfonyl azide group, conferring greater strength to the interface, although it is less stiff than the one formed with oxidated fiber. Finally, the experimental results are in agreement with those obtained from Huet's rheological model. © 1995 John Wiley & Sons, Inc.