bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation between mechanical damping and interphase content in interpenetrating polymer networks
Authors: Song M. , Hourston D. J. , Schafer F.‐U.
Published: September 2002

Recently, some interpenetrating polymer networks with good mechanical damping properties have been synthesized. However, the effect of morphology on this property has not yet been clearly elucidated. Herein, two polystyrene–polyurethane interpenetrating polymer networks, which were grafted using TMI [benzene‐1‐(1‐isocyanato‐1‐methyl ethyl)‐3‐(1‐methylenyl)] and HEMA (2‐hydroxyethyl methacrylate), respectively, have been investigated, as model samples, by modulated‐temperature differential scanning calorimetry and by dynamical mechanical thermal analysis. The results indicate that there is a correlation between mechanical damping and both interphase content and the distribution of composition in the interphase region. The findings should provide valuable information for the design of future damping materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2439–2442, 2001
Foaming of aliphatic polyester using chemical blowing agent
Authors: Kim D. J. , Kim S. W. , Kang H. J. , Seo K. H.
Published: September 2002

Poly(butylene adipate‐co‐succinate) (PBAS), a saturated aliphatic polyester cured by dicumyl peroxide (DCP), was prepared and the viscoelastic property was investigated. The viscosity of crosslinked PBAS increased, and it exhibited rubbery behavior as the content of curing agent was increased. The results suggested that the viscosity and elasticity of PBAS could be regulated by adding a small amount of DCP; hence, the processibility could be improved. Prior to foaming, a proper formulation of blowing agent (blowing agent/urea activator = 100:8 phr) was examined to prepare expanded PBAS foam. Low‐density PBAS expanded foams were prepared using a chemical blowing agent and DCP. The effect of the foaming temperature, additive content, and curing agent content on the blowing ratio and morphology of expanded PBAS foams was investigated. A closed‐cell structure PBAS foam of high blowing ratio (density about 0.05 g/cm3) could be obtained by adding 3 phr DCP. To manufacture expanded PBAS foam under 0.1 g/cm3 using a chemical blowing agent, the storage modulus of the matrix polymer should exceed the loss modulus by enough to stabilize growing bubbles. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2443–2454, 2001
IGC study of filler–filler and filler–rubber interactions in silica‐filled compounds
Authors: Zhang Wenjin , Leonov Arkady I.
Published: September 2002

A modification of the existing methods for evaluating the dispersive and specific components of surface free energy (γd and γs, respectively) was made to investigate filler–rubber and filler–filler interactions by inverse gas chromatography. Four silicas as fillers and various probes that mimic elastomers were employed in this study. It was shown that the pretreatment of silicas with helium could increase γd and decrease γs. Modification of the silica surface with silane could enhance the dispersive interaction and weaken the specific interaction. The temperature dependence of the interfacial interaction was also investigated, and it was found that lower temperatures favored filler–rubber interactions and mixing efficiency. Tests on different sizes of agglomerates demonstrated the existence of a filler–rubber and filler–filler network. It was also found that γd played a role in agglomeration or filler–filler interaction. Our study showed that the larger the specific surface area was, the stronger the dispersive and specific interactions were. The effectiveness of various fillers and elastomer probes was also compared. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2517–2530, 2001
Mechanism of morphology development in dynamically cured EPDM/PP TPEs. I. Effects of state of cure
Authors: Goharpey F. , Katbab A. A. , Nazockdast H.
Published: September 2002

Attempts were made to follow and correlate morphological development with the crosslinking density, or state of cure (SOC), and the surface tension (γ) of the rubber phase in dynamically cured thermoplastic elastomers (TPEs) based on ethylene propylene diene rubber and polypropylene (PP) with 60/40 (w/w) ratios. Samples were taken from a hot running mixer without interruption and quickly quenched in liquid nitrogen both before and after the onset of vulcanization at various SOCs to carry out this process. The quick cooling of the samples prevented the coalescence and agglomeration of the dispersed rubber particles. A two‐phase morphology with the rubber particles dispersed throughout the PP matrix was observed for the uncured but frozen samples, whereas unfrozen blend samples showed a particulate cocontinuous morphology in the uncured state. An increase in the mixing torque with the SOC was observed after the addition of a curing system. This was understood to be caused by the increase in the rubber crosslinking density and also by the enhancement of the interfacial adhesion between the cured rubber phase and the PP matrix, leading to the better wetting of the two phases. Above a certain crosslinking density (SOC), γ of the rubber particles decreased through elastic shrinkage. This phenomenon, together with the breakdown of the agglomerate structure formed by the cured rubber particles, led to a decrease in the mixing torque after a maximum was passed and, finally, to a defined morphology. Based on the obtained results, a four‐stage model is proposed to describe the microstructural development in dynamically vulcanized TPEs. Dynamic mechanical thermal analysis and differential scanning calorimetry results are also used to support the model. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2531–2544, 2001
Reactive processing of polyethylenes on a single screw extruder
Authors: Kumari Isac Sheela , George K. E.
Published: September 2002

The modification of low density polyethylene, linear low density polyethylene, and their blend by dicumyl peroxide at the time of the extrusion on a single screw extruder is reported. The study shows that the optimum conditions of modification can be determined on a torque rheometer and these can then be applied for actual extrusion. A low level of crosslinking can be introduced by reactive extrusion for improving the heat stability without adversely affecting the processing behavior. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2545–2549, 2001
Influence of pendent groups on the tensile properties of polyisoprene vulcanizates
Authors: Van Der Merwe M. J. , Gradwell M. H. S. , McGill W. J.
Published: September 2002

Gum compounds of polyisoprene were vulcanized with a number of different curing systems to give networks with crosslink densities in two different ranges. Stress–strain curves were obtained upon rapid (500 mm/min) and slow (0.5 mm/min) extension. In tetramethylthiuram disulfide (TMTD)/sulfur and zinc dimethyldithiocarbamate/sulfur vulcanizates, which crystallize readily, failure occurred at higher tensile values upon rapid than upon slow extension and this is attributed to a greater contribution to tensile strength by a larger amount of stress‐induced crystallites. X‐ray diffraction showed that 2‐benzothiazole‐2,2′‐disulfide (MBTS)/sulfur vulcanizates did not stress‐crystallize and failure occurred at lower tensile values. Furthermore, samples extended rapidly failed at lower tensile values than did slowly extended samples. These differences, compared to TMTD vulcanizates, are attributed to extensive main‐chain modifications (pendent groups), causing delays in the movement of sections of the chain, leading to the load being unequally distributed between chains. The fewer load‐bearing chains ensure earlier failure. The addition of zinc stearate to TMTD/sulfur and MBTS/sulfur formulations increases the ability of vulcanizates of similar crosslink density to crystallize and enhances tensile properties of vulcanizates with similar crosslink densities, outcomes that are attributed to zinc stearate's promoting crosslinking of pendent groups and reducing impediments to crystallization and chain movement. Dicumyl peroxide–cured networks crystallize readily and exhibit a very rapid upturn in the stress–strain curve. However, failure occurs at lower stress values than apply to accelerated sulfur networks and it is suggested that the distribution of subchain lengths between crosslinks may contribute to their inferior properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2587–2596, 2001
Reactive bonding of natural rubber to metal by a nitrile–phenolic adhesive
Authors: Sasidharan Achary P. , Gouri C. , Ramaswamy R.
Published: September 2002

The mechanism of adhesive bonding of rubber to metal using an interlayer of bonding agent (adhesive) is discussed with respect to various physical and chemical events such as adsorption at the metal surface, chemical crosslinking within the adhesive, interdiffusion, and formation of interpenetrating networks at the rubber–adhesive interface. An investigation on the peel strength of a natural rubber (NR)–adhesive–metal joint, made by vulcanization bonding using nitrile–phenolic adhesive containing various concentrations of toluene diisocyanate–nitrosophenol (TDI–NOP) adduct, is presented. A single‐coat adhesive, consisting of a p‐cresol phenol formaldehyde resin, nitrile rubber (NBR), and vulcanizing agents in methyl ethyl ketone solvent, was selected for the study. Considerable improvement in the peel strength was obtained by the incorporation of TDI–NOP adduct into the nitrile–phenolic adhesive. The peel strength increases as the concentration of TDI–NOP adduct in the adhesive composition increases, then levels off with a transition from interfacial failure to cohesive tearing of rubber. The peel strength improvement is believed to be attributed to the interfacial reactions between the bonding agent and natural rubber, when TDI–NOP adduct is incorporated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2597–2608, 2001
Morphology of the transparent IPN‐like system PE: (BMA‐co‐S)
Authors: Borsig Eberhard , Thomann Ralf , Fiedlerová Agnesa , Mülhaupt Rolf
Published: September 2002

In the study of interpenetrating polymer networks (IPN)‐like systems consisting of polyethylene (PE) and butyl methacrylate (BMA)–styrene (S) copolymer PE/(BMA‐co‐S), the effect of the crosslinker on the morphology of IPN by using electron microscopy and atomic force microscopy (AFM) was investigated. The IPN‐like system PE/(BMA‐co‐S) represents a two‐phase system with finely dispersed domains of crosslinked PE matrix. The interphase between dispersed domains and PE matrix is inhomogeneous and is considered the most interpenetrated part of this IPN‐like system. The size of the domains decreases with the content of crosslinker used. The AFM micrographs allowed the observation of PE lamellae with lengths of about 25 nm. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2615–2620, 2001
Grafting of methyl methacrylate (MMA) onto Antheraea assama silk fiber
Authors: Das A. , Saikia C. N. , Hussain S.
Published: September 2002

Graft copolymerization of methyl methacrylate (MMA) onto nonmulberry silk fiber Antheraea assama was investigated in aqueous medium using the KMnO4–oxalic acid redox system. Grafting (%) was determined as a function of the reaction time, temperature, and monomer and initiator concentrations. The rate of grafting increased progressively with increase of the reaction time up to 4 h and then decreased. The extent of grafting was maximum at 55°C. The extent was also dependent upon monomer and initiator concentrations up to 75.5 × 10−2 and 6 × 10−3 M, respectively. The grafted products were evaluated by infrared spectroscopy and their thermal decompositions were studied by TG and DTG techniques in static air at 20°C min−1 and 30°C min−1 in the range 30–800°C. The kinetic parameters for ungrafted and grafted fibers were evaluated using the Coats and Redfern method. The grafted products were found to be thermally more stable than were those of the ungrafted fibers. The surface characteristics of the ungrafted and grafted fibers were evaluated by scanning electron microscopy. The water‐retention values (WRVs) of the grafted fibers were in decreasing order with increase in the grafting (%). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2633–2641, 2001
Phase behavior of semicrystalline polyester resin in supercritical fluid solvents and solvent mixtures: Implications for supercritical fluid processing
Authors: Conway S. E. , Lim J. S. , McHugh M. A. , Wang J. D. , Mandel F. S.
Published: September 2002

Cloud‐point data between 40 and 240°C and pressures to 2750 bar are presented for a low molecular weight, semicrystalline polyester resin of 53.4 mol % adipic acid and 46.6 mol % 1,4‐cyclohexanedimethanol in supercritical CO2, dimethyl ether (DME), and chlorodifluoromethane (CDFM), and in mixtures of CO2 with DME, CDFM, methanol, ethanol, butanol, octanol, hexafluoroisopropanol, acetone, and cyclohexane. Carbon dioxide, by itself, is an extremely weak supercritical fluid (SCF) solvent because this polyester only dissolves at pressures in excess of 2000 bar and at temperatures over 180°C. However, DME and CDFM are excellent solvents for this polyester, which dissolves at 16 bar and 40°C in CDFM and at 167 bar and 55°C in DME. The melting point of this polyester is reduced from 105 to 40°C in CDFM and to 55°C in DME, which makes the polyester amenable to high intensity mixing for the efficient dispersion of inorganics or crosslinking agents and other hard to deposit materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2642–2648, 2001
Cure kinetics of biphenyl epoxy resin system using latent catalysts
Authors: Kim Whan Gun , Yoon Ho Gyu , Lee Jun Young
Published: September 2002

The investigation of the cure kinetics of a biphenyl epoxy–phenol resin system with different kinds of latent catalysts was performed by differential scanning calorimetry using an isothermal approach. All kinetic parameters of the curing reaction including the reaction order, activation energy, and rate constant were calculated and reported. The results indicated that the curing reaction of the biphenyl epoxy resin system in this experiment proceeded through an autocatalytic kinetic mechanism, irrespective of the kind of catalyst. The epoxy resin system with acid/diazabicycloundecene (DBU) salt as the latent catalyst showed a second overall reaction order; however, a third reaction order was represented for microencapsulated triphenylphosphine (TPP). The storage stability tests for these systems were performed, and a good shelf life was observed in the epoxy resin system with pyromellitic acid/DBU salt, trimellitic acid/DBU salt, and microencapsulated TPP as the latent catalyst. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2711–2720, 2001
Syntheses and thermal properties of poly(hydroxy)urethanes by polyaddition reaction of bis(cyclic carbonate) and diamines
Authors: Kim Mi‐Ra , Kim Hooi‐Sung , Ha Chang‐Sik , Park Dae‐Won , Lee Jin‐Kook
Published: September 2002

In this study, we synthesized poly(hydroxy)urethanes by the polyaddition reaction of bis(cyclic carbonate) and diamine. Bis(cyclic carbonate) was prepared from diglycidyl ether based on bisphenol S and carbon dioxide. Thermal properties and solubilities of the poly(hydroxy)urethanes of five different diamines were compared. The thermal properties of the poly(hydroxy)urethanes depended on the structure of the diamine as well as the structure of the monomer. These poly(hydroxy)urethanes were soluble only in aprotic solvents because of the hydrophilic character of the hydroxy group. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2735–2743, 2001
Ultrasonic modification of aramid fiber–epoxy interface
Authors: Liu L. , Huang Y. D. , Zhang Z. Q. , Jiang B. , Nie J.
Published: September 2002

An ultrasonic irradiation technique is used during the process of fabricating aramid fiber–epoxy resin reinforced composites to improve the interfacial adhesion performance. Under the ultrasonic treatment, the change of the resin viscosity is studied. The results of a microbond test show obvious improvement in the interfacial shear strength after ultrasonic treatment. The mechanical properties of the composites, such as the interlaminar shear strength and tensile strength, are measured. Combined with the SEM results, these show it is the mechanical properties that are improved and the fracture modes are varied from the interface between the fibers and resin to the fibrillation of fibers and resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2764–2768, 2001
Surface characterization and antibacterial activity of chitosan‐grafted poly(ethylene terephthalate) prepared by plasma glow discharge
Authors: Huh Man Woo , Kang Inn‐Kyu , Lee Du Hyun , Kim Woo Sik , Lee Dong Ho , Park Lee Soon , Min Kyung Eun , Seo Kwan Ho
Published: September 2002

Poly(ethylene terephthalate) (PET) texture was exposed to oxygen plasma glow discharge to produce peroxides on its surfaces. These peroxides were then used as catalysts for the polymerization of acrylic acid (AA) in order to prepare a PET introduced by a carboxylic acid group (PET‐A). Chitosan and quaternized chitosan (QC) were then coupled with the carboxyl groups on the PET‐A to obtain chitosan‐grafted PET (PET‐A‐C) and QC‐grafted PET (PET‐A‐QC), respectively. These surface‐modified PETs were characterized by attenuated total reflection Fourier transform IR spectroscopy, electron spectroscopy for chemical analysis, and a contact angle goniometer. The amounts of AA, chitosan, and QC grafted on the PET surfaces as determined by the gravimetric method were about 6, 8, and 9 μg/cm2, respectively. The antibacterial activity of the surface‐modified PET textures was investigated using a shake flask method. After 6 h of shaking, the growth of bacteria was markedly inhibited by PET with ionically (86% in PET‐A−‐C+) and covalently (75% in PET‐A‐C) grafted chitosan and with covalently grafted QC (83% in PET‐A‐QC). After the laundering the inhibition of the growth of the bacteria was maintained in the range of 48–58%, showing the fastness of the chitosan‐grafted PET textures against laundering. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2769–2778, 2001
Photopolymerizable acrylic resin: Effect of curing time and temperature
Authors: Dolez Patricia , Marek Monica , Love Brian J.
Published: September 2002

A photopolymerizable resin was closely examined for its capacity as an adhesive via cure advancement in submerged water at cold temperatures. The effects of curing time and temperature were studied by bond strength measurements and extracted monomer quantification with high pressure liquid chromatography. In both cases the cure was performed under water, and there was one wet interface. Both methods showed the progression of the photopolymerization with time and had similar characteristic times. The adhesion strength was measured by lap shear and remained nearly constant over the entire temperature range studied (around 2 MPa for a 2‐min cure), while a slight increase in the extracted uncured monomer quantity of one of the resin components was obtained for increasing temperatures. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 546–554, 2001
Structure and control release of chitosan/carboxymethyl cellulose microcapsules
Authors: Zhang Lina , Jin Yong , Liu Haiqing , Du Yuming
Published: September 2002

Microcapsules of chitosan/sodium carboxymethyl cellulose (NaCMC) were successfully prepared using a novel method of emulation phase separation. Their structure and morphology were characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), and X‐ray diffraction. Bovine serum albumin (BSA) was encapsulated in the microcapsules to test their release behavior. The swelling behavior, encapsulation efficiency, and release behavior of the microcapsules with different chitosan contents and pH conditions were investigated. The results indicated that the microcapsules have a high encapsulation efficiency (75%) and a suitable size (20–50 μm). The BSA in the microcapsules was speedily released at pH 7.2, namely, in intestinal fluid. The BSA release was reduced with increase of the chitosan content from 17 to 38% in the microcapsules. Acid‐treated microcapsules have a compact structure, owing to a strong electrostatic interaction caused by —NH2 groups of chitosan and —COOH groups of CMC, and the encapsulated BSA was hardly released at pH 1.0, namely, in gastric juice. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 584–592, 2001
Polymer‐bound ethylenediamine–borane reagent: A new class of polymeric reducing agent
Authors: Rajasree K. , Devaky K. S.
Published: September 2002

A polymer‐supported ethylenediamine (EDA)–borane reagent was prepared under mild reaction conditions. The reagent was found to be efficient and selective in the reduction of aldehydes to the corresponding alcohols in high yields at room temperature. The polymeric reagent was prepared on a Merrifield resin and on a 1,6‐hexanediol diacrylate‐crosslinked polystyrene resin (HDODA–PS). HDODA–PS was prepared by suspension polymerization and chloromethylated by a Friedel–Crafts reaction. The preparation of the polymer‐bound EDA–borane reagent involves a series of polymer analogous reactions, such as amination of the chloromethyl resin, conversion to amine hydrochloride, and, finally, complexation with sodium borohydride. The reagent exhibited good chemoselectivity in the reduction of aldehydes. The reduction reactions were carried out with a 2 molar excess of the polymeric reagent. In the competitive reduction of a 1:1 molar mixture of benzaldehyde and acetophenone, benzaldehyde was selectively reduced to benzyl alcohol. The spent resin could be recycled by treating with sodium borohydride. The recycled resin was used several times without much loss in chemical reactivity and mechanical stability. The HDODA–PS resin was found to be more efficient than was the Merrifield resin in the preparation of the reagent as well as in the reduction reactions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 593–600, 2001
Complexation between poly(methacrylic acid) and poly(vinylpyrrolidone)
Authors: Liu Shouxin , Fang Yu , Hu Daodao , Gao Gailing , Ma Jianbiao
Published: September 2002

The complexation between poly(methacrylic acid) (PMAA) and poly(vinylpyrrolidone) (PVP) in aqueous phase was studied by various fluorescence techniques, including fluorescence anisotropy measurements, fluorescence probe studies, and nonradiation energy transfer. It was demonstrated that the complexation of PMAA with PVP occurs within a pH range of 1 to 5 and along with complexation, the conformation of PMAA changed from a hypercoiled to a loosely coiled form. The complex ratio between the two polymers is 2:1 (PMAA/PVP, in monomer unit). Salt effect studies showed that the complexation occurred due to formation of hydrogen bonds between the two polymers. Based on these conclusions and the “connected cluster model” for PMAA at low pH, a “ladder with connected cluster” model was proposed for the structure of PMAA/PVP complex formed at low pH. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 620–627, 2001
Development of a methodology for characterizing commercial chlorinated latex gloves
Authors: Sen Sumit , Mabuni Clayton , Walsh Donna
Published: September 2002

Chlorination of gloves has gained popularity as a more permanent method of reducing the inherent tackiness of natural rubber latex compared to using powder as a dusting lubricant. Transmission of proteins in natural rubber latex into the air as a result of using powder on natural rubber latex gloves may cause serious complications to allergic individuals. A methodology for characterizing commercial chlorinated natural rubber latex gloves using a combination of attenuated total reflectance (ATR)–Fourier transform infrared (FTIR) spectroscopy and ion chromatography (IC) is described. ATR–FTIR studies established that 930–915 and 670–650 cm−1 are definitive wavenumber ranges for the identification of chlorine in commercial chlorinated latex gloves. Confirmation of the ATR–FTIR results and semiquantification of the chlorine content in the latex gloves was carried out by the IC technique. This methodology can be used by glove manufacturers to determine the amount of chlorine in batches of commercial gloves, and thereby prevent possible threats to public health arising from the deterioration of surgical and examination chlorinated latex gloves under severe storage conditions before the end of their expected shelf life. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 672–682, 2001
Development and application of triglyceride‐based polymers and composites
Authors: Khot Shrikant N. , Lascala John J. , Can Erde , Morye Shantaram S. , Williams George I. , Palmese Giuseppe R. , Kusefoglu Selim H. , Wool Richard P.
Published: September 2002

Triglyceride oils derived from plants have been used to synthesize several different monomers for use in structural applications. These monomers have been found to form polymers with a wide range of physical properties. They exhibit tensile moduli in the 1–2 GPa range and glass transition temperatures in the range 70–120 °C, depending on the particular monomer and the resin composition. Composite materials were manufactured utilizing these resins and produced a variety of durable and strong materials. At low glass fiber content (35 wt %), composites produced from acrylated epoxidized soybean oil by resin transfer molding displayed a tensile modulus of 5.2 GPa, a flexural modulus of 9 GPa, a tensile strength of 129 MPa, and flexural strength of 206 MPa. At higher fiber contents (50 wt %) composites produced from acrylated epoxidized soybean oil displayed tensile and compression moduli of 24.8 GPa each, and tensile and compressive strengths of 463.2 and 302.6 MPa, respectively. In addition to glass fibers, natural fibers such as flax and hemp were used. Hemp composites of 20% fiber content displayed a tensile strength of 35 MPa and a tensile modulus of 4.4 GPa. The flexural modulus was ∼2.6 GPa and the flexural strength was in the range 35.7–51.3 MPa, depending on the test conditions. The flax composite materials had tensile and flexural strengths in the ranges 20–30 and 45–65 MPa, respectively. The properties exhibited by both the natural‐ and synthetic fiber‐reinforced composites can be combined through the production of “hybrid” composites. These materials combine the low cost of natural fibers with the high performance of synthetic fibers. Their properties lie between those displayed by the all‐glass and all‐natural composites. Characterization of the polymer properties also presents opportunities for improvement through genetic engineering technology. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 703–723, 2001
Water diffusion studies in polyimide thin films
Authors: Seo Jongchul , Han Haksoo
Published: September 2002

The water diffusion behaviors and activation energies of PDA‐ and ODA‐based polyimide thin films were quite dependent on both the chemical structure and the morphological structure in the films. The water diffusion coefficients of polyimide thin films increased with increasing temperature. The activation energies varied in the range of 5.81 to 9.27 kcal/mol and were relatively higher for the PDA‐based polyimide thin films than for the corresponding ODA‐based polyimide thin films. For the PDA‐ and ODA‐based polyimide films, the differences in the morphological structures and the chemical affinity to water molecules might be reflected directly on the water diffusion behaviors. The PDA‐based polyimide films exhibited a relatively more ordered morphological structure (high crystallinity and good in‐plane orientation) than that of the corresponding ODA‐based polyimide thin films, which may serve as impenetrable obstacles for the water diffusion in the out‐of‐plane direction. Consequently, it may lead to a relatively slower water diffusion and high activation energy in the PDA‐based polyimide thin films. Additionally, the PDA‐based polyimide films with relatively lower chemical affinity showed relatively low diffusion coefficients and high activation energies. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 731–737, 2001
Dissolution and characterization of regenerated Antheraea pernyi silk fibroin
Authors: Kweon Haeyong , Park Young Hwan
Published: September 2002

Dissolution of Antheraea pernyi silk fiber was carried out in a calcium nitrate solution with various dissolving conditions. The solubility was significantly dependent on the concentration of calcium nitrate, dissolving temperature, and time. The proper conditions of dissolution were found as 7M calcium nitrate, 100°C temperature, and 3 h dissolving time. The aqueous solution of A. pernyi silk fibroin was composed of a mixture of polypeptides with several molecular weights above 14 kDa. FTIR and XRD showed that regenerated A. pernyi silk fibroin was composed of an α‐helix as well as a random‐coil conformation while silk fiber had a traditional β‐sheet structure. The endo–exo transition in the temperature ranges of 228–232°C also supports these conformations of regenerated silk fibroin film. TGA and DTG curves showed that the thermal decomposition of regenerated A. pernyi silk fibroin proceeded by three steps, not dependent on the conformation. The mechanical damping peaks (tan δ) appeared about 227°C with a minor shoulder maximum about 240°C, which were somewhat lower than those of tussah silk fiber. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 750–758, 2001
Novel formulations of high‐performance epoxy–amine networks based on the use of nanoscale phase‐separated antiplasticizers
Authors: Sauvant Valérie , Halary Jean Louis
Published: September 2002

The addition of an antiplasticizing agent in epoxy–amine resin formulations was revisited. The choice, as the antiplasticizer, of a chemical species which is fully miscible with the mixture of monomers but gives rise to nanoscale phase separation along the network construction was shown to be greatly favorable. Small domains, enriched in additive molecules, segregate in the polymer matrix, which is itself plasticized by residual additive molecules. Use of the additives did not change markedly the cure cycle and the total extent of reaction after full cure. The main effects of this special morphology on network properties were the depression of the glass transition temperature, Tg, of the matrix and the appearance of some damping (so‐called μ‐relaxation) in the temperature range intermediate between the secondary relaxation and the main mechanical relaxation. Networks prepared in this way were shown (1) to save a sufficiently high value of Tg in the view of the applications, (2) to present a higher modulus and higher toughness around room temperature than those of the conventional systems without an additive, and (3) to exhibit a lower water uptake at equilibrium than that of their regular homolog. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 759–774, 2001
Energetic studies on epoxy–polyurethane interpenetrating polymer networks
Authors: Park Soo‐Jin , Jin Joong‐Seong
Published: September 2002

A blend system prepared from epoxy resin (EP) and polyurethane (PU) was investigated in terms of glass‐transition temperature (Tg), contact angle, mechanical interfacial, and mechanical properties. Deionized water and diiodomethane were chosen as the angle testing liquids. In this work, the models of Owens–Wendt and Wu, using a geometric mean, were studied to analyze the surface free energy of the EP/PU blend system. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the intermolecular hydrogen bonding and functional group changes. The impact test was carried out at room and cryogenic temperatures to determine the low‐temperature performance of PU. As a result, mechanical interfacial and mechanical properties give a maximum value at 40 phr of PU, and the deviation of Tg of EP/PU was the closest at 40 phr of PU. Thus it is concluded that EP and PU have the best compatibilities at this ratio. Furthermore, the specific (or polar) component of the surface free energy of the blend system was largely influenced on the addition of the PU, resulting in increasing the critical stress intensity factor (KIC) and the impact strength for the excellent low‐temperature performance. These results could be explained by means of improvement of hydrogen bonding between the hydroxyl group in EP and isocyanate group in PU. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 775–780, 2001
Pulmonary appendix of the short‐tailed shrew (Blarina): A unique immunologic organ
Authors: Parke Wesley Wilkin
Published: September 2002

The right bronchus of the short‐tailed shrew, Blarina brevicauda, terminates in a nonrespiratory pulmonary appendix (PA) containing two bronchial extensions. The experimentally demonstrated ability of these structures to collect and peristaltically expel aspirated material was initially assumed to be a sufficient reason for their developmental persistance, but as bronchus associated lymphoid tissue (BALT) became a subject of immunologic interest in other species, a possible immunologic role for the concentrations of BALT observed in the shrew PA were investigated. As the BALT of the PA contained many well‐differentiated plasma cells and numerous particle‐containing macrophages, 6‐μ paraffin sections were treated with an immunoperoxidase avidin‐biotin preparation that chromogenically identified alpha chains of IgA in many of the PA plasma cells and their associated luminal secretions. Also, vascular injections revealed that the PA had a complex relationship with anastomotic sinusoids connecting the bronchial and pulmonary circulation systems, and scanning electron microscopy showed that the luminal epithelial surfaces of the PA were virtually identical to the scattered BALT aggregates in the bronchi of other animals. It thus appeared that these unique structures in the shrew are morphologically and topographically suited to receive aspirated antigens that induce secretory IgA production, while possibly providing other humoral and cellular immunologic products to the general circulation. Anat Rec 266:184–191, 2002. © 2002 Wiley‐Liss, Inc.
Proliferation and apoptosis in the developing human neocortex
Authors: Chan Wood Yee , Lorke Dietrich E. , Tiu Sau Cheung , Yew David T.
Published: September 2002

The cell kinetics of the developing central nervous system (CNS) is determined by both proliferation and apoptosis. In the human neocortex at week 6 of gestation, proliferation is confined to the ventricular zone, where mitotic figures and nuclear immunoreactivity for proliferating cell nuclear antigen (PCNA) are detectable. Cell division is symmetric, with both daughter cells reentering mitosis. At week 7, the subventricular zone, a secondary proliferative zone, appears. It mainly gives rise to local circuit neurons and glial cells. Around week 12, the ventricular and subventricular zones are thickest, and the nuclear PCNA label is strongest, indicating that proliferation peaks at this stage. Thereafter, asymmetric division becomes the predominant mode of proliferation, with one daughter cell reentering mitosis and the other one migrating out. Towards late gestation, the ventricular and subventricular zones almost completely disappear and proliferation shifts towards the intermediate and subplate zones, where mainly glial cells are generated. A remnant of the subventricular zone with proliferative activity persists into adulthood. In general, proliferation follows a latero‐medial gradient in the neocortex lasting longer in its lateral parts. Apoptotic nuclei have been detected around week 5, occurring in low numbers in the ventricular zone at this stage. Apoptotic cell death increases around midgestation and then spreads throughout all cortical layers, with most dying cells located in the ventricular and subventricular zones. This spatial distribution of apoptosis extends into late gestation. During the early postnatal period, most apoptotic cells are still located in the subcortical layers. During early embryonic development, proliferation and apoptosis are closely related, and are probably regulated by common regulators. In the late fetal and early postnatal periods, when proliferation has considerably declined in all cortical layers, apoptosis may occur in neurons whose sprouting axons do not find their targets. Anat Rec 267:261–276, 2002. © 2002 Wiley‐Liss, Inc.
Midline corpus callosum is a neuroanatomical focus of fetal alcohol damage
Authors: Bookstein Fred L. , Sampson Paul D. , Connor Paul D. , Streissguth Ann P.
Published: September 2002

Prenatal exposure to high levels of alcohol often induces birth defects that combine morphological stigmata with neurological or neuropsychological deficits. But it has proved problematic to diagnose these syndromes in adolescents and adults, in whom the morphological signs are absent or attenuated, the behavioral deficits nonspecific, and the exposure history often difficult to reconstruct. Localizing the associated brain abnormalities might circumvent most of these difficulties. To this end, three‐dimensional (3D) locations were recorded for 67 homologous points on or near the corpus callosum in magnetic resonance (MR) brain images from 60 adolescents and adults who were normal, 60 diagnosed with fetal alcohol syndrome, and 60 diagnosed with fetal alcohol effects. We combined the standard statistical approach to this type of geometric data, Procrustes analysis, with a multivariate strategy focusing on differences in variability. In this data set, the shape of the corpus callosum and its vicinity proves systematically much more variable in the alcohol‐affected brains than in those of the normal subjects. From this excess variability follows a promising classification rule, having both high sensitivity (100 out of 117) and high specificity (49 out of 60) in this sample. The discrimination uses four landmark points and two summary scores of callosal outline shape. The information from the corpus callosum and vicinity, as viewed in MR brain images of full‐grown subjects, may serve as a permanent record of the prenatal effects of alcohol, even in patients who are first suspected of these syndromes relatively late in life or who lack the facial signs of prenatal alcohol damage. The statistical pattern underlying the callosal diagnosis also leads to speculations on mechanisms of the prenatal damage. Anat Rec (New Anat) 269:162–174, 2002. © 2002 Wiley‐Liss, Inc.
A closer look at Neanderthal postcanine dental morphology: The mandibular dentition
Authors: Bailey Shara E.
Published: September 2002

Neanderthals are known to exhibit unique incisor morphology as well as enlarged pulp chambers in postcanine teeth (taurodontism). Recent studies suggest that their overall dental pattern (i.e., in morphologic trait frequencies) is also unique. However, what this means in a phylogenetic sense is not known. Although exploring the polarity of dental morphologic characters is essential to understanding the phylogenetic implications of unique patterns of variation, few have undertaken this task. This study moves beyond standard scoring methods, which are based on modern humans, to include several postcanine traits that have not been considered previously. In addition, Homo erectus is used as an outgroup to Neanderthals and modern humans to explore the polarity of these traits. The findings of this study suggest that Neanderthals are not only unique in their pattern of dental trait frequencies (as found in previous studies) but that they present several dental autapomorphies, as well. These include a high frequency of the mid‐trigonid crest in lower molars and unique morphology of the lower premolars. Interestingly, these characters are not observed in the Mauer mandible, which some have claimed to be a member of a chronospecies that is a unique ancestor to Neanderthals. Anat Rec (New Anat) 269:148–156, 2002. © 2002 Wiley‐Liss, Inc.
Rapid technique for imaging the blood vascular system using stereoangiography
Authors: Sedlmayr Jayc C. , Witmer Lawrence M.
Published: September 2002

Data on vascular anatomy traditionally have been derived from time‐consuming gross dissection and histology, which has prevented the assembly of large sample sizes. Vascular injection of radiopaque medium (angiography) is a rapid technique, but, as typically performed, it has limitations (e.g., superimposition and poor subsequent dissectibility). We present a novel angiographic technique comprised of two elements: 1) a new, dissectible injection medium; and (2) stereoradiography. The injection medium consists of liquid barium (providing radiopacity) and latex (providing dissectibility). Domestic duck heads were the study system. The relative concentrations of barium and latex were varied, and the resulting radiographs were assayed for vessel radiopacity and the number of observable vessels. A wide range of barium percentages yielded excellent results, suggesting that preparation of the medium can be “eyeballed” for most applications, which enhances processing speed. The stereoradiographic element solved the superimposition problem, allowing stunning resolution of the spatial relationships of vessels to each other and to other tissues. Stereoangiography is a fast and easy technique that permits the acquisition of detailed anatomical data from many specimens, thereby enabling something rarely achieved: population‐level anatomical studies. Anat Rec 267:330–336, 2002. © 2002 Wiley‐Liss, Inc.
Mapping the roots of agriculture in southern Arabia: the application of satellite remote sensing, global positioning system and geographic information system technologies
Authors: Harrower M. , McCorriston J. , Oches E. A.
Published: September 2002

Satellite remote sensing, global positioning system (GPS) and geographical information system (GIS) technologies form a powerful methodological and analytical triad for archaeological research, particularly in remote regions where few large‐scale maps are available. This paper outlines the application of these technologies as a component of the Roots of Agriculture in Southern Arabia (RASA) research project and provides a review for archaeologists interested in potential applications, particularly in arid and semi‐arid environments. We used LANDSAT satellite imagery and GPS data to construct a GIS and provide a foundation for the management and analysis of archaeological, geomorphological and palaeoecological evidence of middle Holocene environmental conditions and human land‐use in the remote highlands of southern Yemen. Using both supervized and unsupervized multispectral landscape classification procedures we categorized the landscape into seven classes based on landform and sedimentary cover characteristics. The resulting GIS helps us evaluate the relationship between landscape characteristics, site location, site preservation, and investigate associations with sociocultural and environmental variables. Copyright © 2002 John Wiley & Sons, Ltd.
Dysregulation of transforming growth factor β signaling in scleroderma: Overexpression of endoglin in cutaneous scleroderma fibroblasts
Authors: Leask A. , Abraham D. J. , Finlay D. R. , Holmes A. , Pennington D. , Shi‐Wen X. , Chen Y. , Venstrom K. , Dou X. , Ponticos M. , Black C. , Jackman J. K. , Findell P. R. , Connolly M. K.
Published: September 2002

Objective

As an initial approach to understanding the basis of the systemic sclerosis (SSc; scleroderma) phenotype, we sought to identify genes in the transforming growth factor β (TGFβ) signaling pathway that are up‐regulated in lesional SSc fibroblasts relative to their normal counterparts.

Methods

We used gene chip, differential display, fluorescence‐activated cell sorter, and overexpression analyses to assess the potential role of TGFβ signaling components in fibrosis. Fibroblasts were obtained by punch biopsy from patients with diffuse cutaneous SSc of 2–14 months' duration (mean 8 months) and from age‐ and sex‐matched healthy control subjects.

Results

Unexpectedly, we found that fibroblasts from SSc patients showed elevated expression of the endothelial cell–enriched TGFβ receptor endoglin. Endoglin is a member of the nonsignaling high‐affinity TGFβ receptor type III family. The expression of endoglin increased with progression of disease. Transfection of endoglin in fibroblasts suppressed the TGFβ‐mediated induction of connective tissue growth factor promoter activity.

Conclusion

SSc is characterized by overproduction of matrix; that is, genes that are targets of TGFβ signaling in normal fibroblasts. Our findings suggest that lesional SSc fibroblasts may overexpress endoglin as a negative feedback mechanism in an attempt to block further induction of profibrotic genes by TGFβ.
Stromelysin 1 (matrix metalloproteinase 3) and HLA–DRB1 gene polymorphisms: Association with severity and progression of rheumatoid arthritis in a prospective study
Authors: Constantin Arnaud , Lauwers‐Cancès Valérie , Navaux Frédérique , Abbal Michel , Meerwijk Joost van , Mazières Bernard , Cambon‐Thomsen Anne , Cantagrel Alain
Published: September 2002

Objective

To test the hypothesis of an association between a polymorphism in the matrix metalloproteinase 3 (MMP‐3) gene promoter and the susceptibility, severity, and progression of rheumatoid arthritis (RA), and to further document the association between HLA–DRB1 alleles encoding the shared epitope (SE) and the severity and progression of RA.

Methods

Patients with early RA (n = 103) were included in this prospective study. A total radiographic damage score (TDS; by the Sharp/van der Heijde method) was used to quantify RA severity at baseline and after 4 years of followup. The 5A/6A biallelic polymorphism in the MMP‐3 gene promoter was analyzed using fluorescence‐based polymerase chain reaction (PCR). HLA–DRB1 genotyping was performed using PCR methods. Control subjects (n = 127) were unrelated healthy individuals.

Results

MMP‐3 allele carriage rates and allele and genotype frequencies did not differ between patients and controls. The MMP‐3 6A/6A genotype was associated with the highest TDS both at baseline and after a 4‐year followup and with the highest progression of the TDS over the 4 years of followup. The DRB1 SE+/+ genotype was associated with the highest TDS after a 4‐year followup and with the highest progression of the TDS over the 4 years of followup. Patients homozygous for MMP‐3 6A and DRB1 SE had the highest progression of the TDS.

Conclusion

This study provides the first evidence of an association between a polymorphism in the MMP‐3 gene promoter and the severity and progression of RA, but not RA susceptibility. Investigation of this polymorphism could be combined with that of DRB1 gene polymorphism to improve the predictive accuracy and management strategy in early RA.