bluuebunny/crossref_metadata_2025_split huggingface dataset:
Association phenomena between copolymers of p‐styrenesulfonate(Cs+)/3‐methacryloxypropyltrimethoxysilane and hydroxypropylcellulose in aqueous solution and solvent‐cast films
Authors: Schultz Gerald 
Published: April 2003

AbstractAssociation between copolymers of p‐styrenesulfonate (Cs+)/3‐methacryloxypropyltrimethoxysilane [copolySS(Cs+)/MAPTMS], and hydroxypropylcellulose (HPC) are shown to exist in dilute aqueous solution. Gels form at concentrations as low as 0.05 g/dL. The tendency to form gels is a function of mol % MAPTMS in the copolymer and molecular weight of HPC. Gels can be dispersed by the addition of dimethylformamide (DMF), a known disruptor of hydrogen bonding. Homopolymers of SS(Cs+) and MAPTMS were also prepared. PolyMAPTMS shows anamolous behavior with regards to association with HPC in that gels form to a lesser degree than the trend exhibited by the copolymers. This is rationalized on the basis of the lack of chain expansion due to the absence of salt groups and their intrapolymer repulsions. In addition to the hydrodynamic data, the phase relationship of blends of HPC with either copolySS(Cs+)/MAPTMS, polySS(Cs+), or polyMAPTMS cast from aqueous solution strongly suggests specific interactions between polymers.
Thermal degradation of epoxy/silica composites monitored via dynamic mechanical thermal analysis
Authors: Unsworth J. , Li Y. 
Published: April 2003

AbstractA dynamic mechanical thermal analyzer (DMTA) was used to monitor changes of dynamic mechanical properties during thermal degradation of two types of epoxy/silica composites, both of which are used as electrical insulation in power apparatus. It was found that the peak value of the dynamic loss factor (tan δ), glass transition temperature (Tg), and dynamic storage modulus (E′) above Tg changed considerably with increasing thermal degradation, while E′ at the glassy state only underwent a moderate change with increased thermal degradation. It is concluded that the DMTA technique is very sensitive to the structural changes in the investigated epoxy composites due to the thermal degradation. It is also confirmed by DMTA tests that further cross‐linking and loss of dangling chains are occurring slowly during the stage prior to the onset of the severe degradation. © 1992 John Wiley & Sons, Inc.
Effect of chemical cross‐linking under elongation on shape restoring of poly(vinyl alcohol) hydrogel
Authors: Hirai Toshihiro , Maruyama Hidetoshi , Suzuki Takashi , Hayashi Sadao 
Published: April 2003

AbstractAn anisotropically swollen hydrogel of poly(vinyl alcohol) (PVA) was found to be able to restore an isotropic physical shape by restoring isotropic physical cross‐links induced by anisotropically distributed chemical cross‐links. The anisotropic chemical cross‐links were introduced in the isotropic physical gel by cross‐linking with glutaraldehyde under elongation. The physical gel was made from the PVA aqueous solution by repetitive freezing and thawing. The chemically cross‐linked gel had kept its original shape and physical properties despite the chemical treatment under strain. However, by the heat treatment in boiling water, the gel changed its form anisotropically depending on the strain applied in the chemical treatment. The anisotropically swollen gel was deswollen in methanol and then reswollen in water. The reswollen gel took back its original isotropic shape, suggesting that the anisotropic chemical cross‐links thus introduced in the gel have a memory effect on the restoration of isotropic physical cross‐links. © 1992 John Wiley & Sons, Inc.
Reaction mechanisms of the metal chelates with epoxy oligomers and the structures of the epoxy—chelate metal‐containing matrixes
Authors: Kurnoskin A. V. 
Published: April 2003

AbstractA theoretical generalization of the experimental results of the investigation of the properties of the metalliferous epoxy chelate polymers (MECP) based on diglycidyl ether of bisphenol‐A (DGEBA) has been carried out. Shown is the possibility of adjusting the structure and properties of MECP by changing the temperature of hardening and the content of a chelate hardener in an epoxy compound and by varying the composition of a chelate molecule, i.e., its structural fragments—a metal, ligand, and anion, which leads to changing the predominant mechanism of the reaction of the epoxy oligomer with the hardener, which can be catalytic or can proceed with the amino groups of a complex cation or unconnected ligand and with an anion. As a result, the epoxy chelate matrixes of different structures are formed. A correlation between the tensile strength (σt) and tensile modulus (Et), flexural strength (σf), and flexural modulus (Ef) of MECP—σt (Et) and σf = f(Ef)—has been established. The form of this correlation corroborates the presumption that the polymerization mechanism of the epoxy oligomer is changed and the various structures of the polymer matrixes are formed. © 1992 John Wiley & Sons, Inc.
Specialty polyurethane soft segments. III. Synthesis and characterization ofN‐isopropyl polyether polyamine oligomers containing backbone urea or amide moieties
Authors: Harris Robert F. , Habermann Clarence E. 
Published: April 2003

AbstractPrimary polyether polyamine oligomers containing preformed urea or amide moieties in their backbones were converted to the correspondingN‐isopropyl polyether polyamine oligomers (secondary amines) by reaction with acetone and hydrogen in the presence of a catalyst. The best results were from reactions carried out at about 150°C using a supported platinium or palladium catalyst in a fixed bed. Reactants and products were monitored by quantitative carbon‐13 NMR, size exclusion chromatography, and amine titration. Perchloric acid titration was used to quantify the number of urea moleties per molecule. Amide backbone materials gave very little backbone degradation. However, some backbone degradation was observed with urea backbone materials, leading to products with lower molecular weights. These polyether polyamine oligomers, containing urea or amide moieties in their backbones, are useful in urethane/urea polymer systems. The lower reactivity of these secondary amines (toward polyisocyanates) results in their utility in a broader range of polyurethane fabrication technologies. © 1992 John Wiley & Sons, Inc.
Chemically induced porogen decomposition in premembranes for porogen derived membranes
Authors: Eyal A. M. , Hajdu K. , Hazan B. , Edelstein D. 
Published: April 2003

AbstractStudies of chemically induced porogen decomposition in Porogen Derived Membranes show that substantially complete decomposition of porogen molecules, molecularly dispersed in the polymeric matrix, is attainable. Several hours are required for decomposition by reagents penetrating into the premembrane at ambient. Decomposition rate is determined by characteristics of polymer, porogen, and reagent used, by polymer/porogen weight ratio, by reagent concentration, and by temperature. The concept of decomposition by an internal catalyst was also validated. In addition to direct relevance to the new method of membrane formation, the study provides better understanding of phenomena of general interest, such as transport of small molecules through changing polymeric matrices. © 1992 John Wiley & Sons, Inc.
Solvent effect on the curing of polyimide resins
Authors: Hsu Tzu‐Chien J. , Liu Zu‐Ling 
Published: April 2003

AbstractThe effect of the solvent 1‐methyl‐2‐pyrrolidinone (NMP) on the curing of polyimide resins synthesized from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA) has been investigated. Three polyimide precursors, i.e., the polyamic acid (PAA), with controlled amount of NMP were prepared. The study was aimed first to independently investigate the decomplexation process, which involved the evolution of hydrogen‐bonded NMP from PAA, without interference from imidization. This was accomplished by TGA at varying heating rates using different solvent content in PAA. The observed one‐stage decomplexation process suggested that the complex formation of NMP and PAA was not the same as the model compound studied by others. An average value of 150 kJ/mol for the activation energy of the decomplexation process was obtained. The study then sought to identify the effect of the decomplexation on the imidization kinetics by employing DSC at several drying temperatures and also varying heating rates. This allowed one to control the extent of plasticization that occurred to facilitate the imidization process. Our DSC data showed that over‐drying PAA resulted in prolonged imidization due mainly to the lack of plasticization by decomplexed NMP. The estimated enthalpy of imidization and that of decomplexation were 114 KJ/mol and 53 kJ/mol NMP, respectively. Finally, the imidization kinetics was independently investigated using FTIR, without the interference from decomplexation process. The results indicated that there were four stages during the entire imidization process. Up to a temperature of 150°C, less than 20% of amide groups had reacted to give imide groups and the reaction was slow. Most of the imidization took place between 150 and 180°C with conversion as high as 90%. The imidization process was completed after the temperature was further raised to 250°C. Above 250°C, the reverse reaction became more significant (due probably to configurational and packing preference) and resulted in a lowering of final conversion back to 80%. © 1992 John Wiley & Sons, Inc.
Toughening of graphite–epoxy composites with an electrocopolymerized high‐temperature thermoplastic interphase
Authors: Wimolkiatisak Angel S. , Bell James P. 
Published: April 2003

AbstractElectrocopolymerization of a high‐temperature 3‐carboxyphenylmaleimide‐styrene interphase onto graphite fibers was carried out in an effort to toughen graphite—epoxy composites. The effects of the interphase and its thickness on the mechanical properties and the failure modes were investigated. The optimum interphase thickness was found to be about 0.16 μm. At this thickness, the average value of the DCB Mode I critical strain energy release rate is improved by about 100%, the average notched Izod impact resistance is improved by about 60%, and the average interlaminar shear strength is maintained at about the same value as the control composites. The failure mode was shifted toward more ductile failure with the inclusion of an interphase. © 1992 John Wiley & Sons, Inc.
Structure of heat‐treated nylon 6 fibers. II. Structural stability and dye leveling
Authors: Simal Abigail Lisbão , De Godoy Oriani Luis Alberto 
Published: April 2003

AbstractNylon 6 fibers were submitted to three types of heat treatments at different temperatures and times in order to find the best conditions to achieve structural stability. The boiling water treatment proved to be more effective in promoting profound structural modifications than the other treatments (dry treatment and the dry treatment followed by a 5‐h boiling water heat setting). Also, the fibers reached their maximum structural transformations after 1 h of treatment. Thus, a 5‐h boiling water treatment was chosen to heat‐set the fibers. Then, the heat‐set fibers were submitted to dyeing and migration experiments with different disperse dyes. The obtained results demonstrate that the discontinuities observed in the curves of migration factor versus square root of time might be related to the mechanism of the migration experiments. The different solubilities of the disperse dyes in water helped the understanding of this mechanism. Also, this study with nylon 6 fibers reveal that the proposed model can be used for leveling time prediction, and the discontinuities mentioned above can for practical purposes be neglected. © 1992 John Wiley & Sons, Inc.
Pervaporation of ethanol–water mixtures through styrene‐substituted N‐phenylmaleimide copolymer membranes
Authors: Lokaj J. , Bílá J. 
Published: April 2003

AbstractA number of copolymers of styrene with substituted N‐phenylmaleimides were synthesized and their solutions in chloroform were used in the casting of homogeneous membranes. The latter were applied in the separation of variously concentrated ethanol—water mixtures by pervaporation at 35°C. The membranes were characterized by the separation factor related to preferentially transported water and by the flux of the permeate. In contrast to membranes made from copolymers of styrene with N‐phenylmaleimide, the separation factor of membranes containing substituted N‐phenylmaleimides increased with increasing amount of ethanol in the feed solution. The effect of incorporated imide units on the properties of the membranes under investigation is discussed. © 1992 John Wiley & Sons, Inc.
Solvent‐assisted graft copolymerization of acrylamide on poly(ethylene terephthalate) films using benzoyl peroxide initiator
Authors: Şanli Oya , Pulat Emsal 
Published: April 2003

AbstractGraft‐copolymerization of acrylamide (AAm) on poly(ethylene terephthalate) (PET) films using benzoyl peroxide (Bz2O2) initiator has been studied. Four organic solvents, namely, pyridine (Py), 1,2‐dichloroethane (DCE), DEC/H2O (20/80, v/v), and dimethyl sulfoxide (DMSO), were used as swelling agents. DMSO was found to be the most suitable swelling agent. Solvent inclusion in the films increased with increased length of solvent treatment time and temperature. Elevated temperatures had a greater effect on the inclusion of swelling agents than did the length of swelling. Variation of graft yield with the type of solvent, initiator concentration, monomer concentration, temperature, and polymerization time were also investigated. The graft yield increased in the order of toluene, benzene, DMSO. The optimum temperature for grafting was found to be 70°C. The graft yield was observed to increase with monomer concentration and polymerization time, then reached a plateau. The graft yield increased up to a certain Bz2O2 concentration, then decreased. © 1993 John Wiley & Sons, Inc.
Gas sorption in poly(butylene terephthalate). I. Influence of gas molecules
Authors: Zhou Z. , Springer J. 
Published: April 2003

AbstractThe sorption of CO2 and the noble gases Ne and Ar in semicrystalline glassy poly(butylene terephthalate) (PBTP) films was measured by the gravimetric method with a recording microbalance at 298 K. The sorption of CO2 was found to be significantly higher than that of Ne and Ar. This is attributed to a specific interaction between CO2 and PBTP. The sorption isotherm for CO2 was analyzed by the dual‐mode sorption model, while the sorption behaviors for Ne and Ar did not follow this model. Their sorption isotherms can be described by the sorption model developed here for the noble gases in PBTP. A critical adsorption pressure p* that is dependent mainly on the relative size of the frozen microvoids and the noble gas atoms is defined in this model. The Langmuir adsorption for describing the sorption in this gas/polymer system in addition to Henry's solubility happens just above this p*, whereas only Henry's solubility takes place below p*. © 1993 John Wiley & Sons, Inc.
Investigations on vinylene carbonate. V. Immobilization of alkaline phosphatase onto LDPE films cografted with vinylene carbonate and N‐vinyl‐N‐methylacetamide
Authors: Chen Guohua , van der Does Leen , Bantjes Adriaan 
Published: April 2003

AbstractLow‐density polyethylene (LDPE) films cografted with vinylene carbonate (VCA) and N‐vinyl‐N‐methylacetamide (VIMA) were studied as a matrix for the immobilization of the enzyme alkaline phosphatase (ALP) either by direct fixation or by inserting spacers. When water‐soluble alkyldiamines such as diaminoethylene, diaminobutane, diethylenetriamine, and diaminohexane were used as spacers between the matrix and the enzyme, the surface concentration (SC) of the active ALP coupled on the matrix was increased, whereas the effect of the spacer on the SC was dependent on the length of the spacer. Bovine serum albumin (BSA) was preimmobilized onto the LDPE films to provide a better simulation of the biological environment for the enzyme, and the SC of ALP on the matrix was significantly increased by coupling ALP onto the BSA preimmobilized surfaces. Compared to native ALP, some physicochemical properties of ALP could be improved by the covalent immobilization. © 1993 John Wiley & Sons, Inc.
Mechanism of the electrocopolymerization of styrene and N‐(3‐carboxyphenyl)maleimide onto graphite fibers in aqueous solution
Authors: Iroh J. O. , Bell J. P. , Scola D. A. 
Published: April 2003

AbstractElectrochemical copolymerization of styrene and N‐(3‐carboxyphenyl)maleimide was performed in an aqueous sulfuric acid solution using AS‐4 graphite fibers as the working electrode. Cyclic voltammetric analysis results suggest radical initiation of polymerization via the reduction of the N‐(3‐carboxyphenyl)maleimide and sulfuric acid. Radical chain electrocopolymerization was strongly suggested by the inhibition of chain growth in the presence of hydroquinone and 2,2‐diphenylpicrylhydrazyl (DPPH). Compositional analysis of copolymers and reactivity ratios rs ∼ 0.014 and rm ∼ 0.041 for styrene and N‐(3‐carboxyphenyl)maleimide [N‐(3‐CMI)], respectively, confirmed a 1 : 1 alternating electrocopolymerization. Kinetic analysis shows a first‐ and 1/2‐order dependence of the rate of chain growth on initial monomer concentration and initiator concentration, respectively. A model incorporating these data is presented. © 1993 John Wiley & Sons, Inc.
Influence of microstructure on dynamic mechanical behaviour of polymeric composites with complex inclusions
Authors: Kim K. R. , An J. H. , Cho K. W. , Park C. E. 
Published: April 2003

AbstractThe dynamic mechanical properties of polymeric composites composed of crosslinked poly(n‐butyl methacrylate) continuous‐phase and crosslinked polystyrene dispersed phase with poly(n‐butyl methacrylate) occlusion have been examined. The composite samples were prepared by mixing and swelling of the crosslinked polystyrene particles obtained by emulsifier‐free emulsion polymerization, with n‐butyl methacrylate and crosslinker, then photopolymerizing at the desired temperature. The composite microstructure was varied by either changing the crosslink density of polystyrene, and temperature of swelling and polymerization, or using different sizes and contents of polystyrene particles. The tan δ peak positions of composite samples are found to be dependent on morphological characteristics as well as the properties of the dispersed phase while the peak height seems to be dependent on the effective volume of dispersed phase composed of polystyrene and poly(n‐butyl methacrylate) occlusions. Special attention has been paid to the comparison among composite, homonetworks, and bulk IPN samples that are expected to have the identical structure with the complex dispersed phase of the composite samples. © 1993 John Wiley & Sons, Inc.
Radiation initiated grafting of acrylic acid onto tetrafluoroethylene–ethylene copolymers
Authors: Kostov G. K. , Atanassov A. N. 
Published: April 2003

AbstractHydrophilic carboxyl containing fluoropolymers was obtained by radiation grafting of acrylic acid onto tetrafluoroethylene—ethylene copolymers with different compositions. By using simultaneous (60Co) and preirradiation (electron beam) techniques, the effect of the grafting conditions (monomer concentration, dose rate, dose, film thickness, etc.) on the degree of grafting was studied. A considerable effect of the polymer compositions, especially the CF bonds content, and the batch irradiation on the degree of grafting was found. It was observed by scanning electron microscopy that the grafting took place mainly on the polymeric film surface and developed inward with increasing diffusion of the acrylic acid through the grafted layers. © 1993 John Wiley & Sons, Inc.
Studies on the synthesis of block copolymers of acrylonitrile and ethylene oxide
Authors: Wódka Tadeusz 
Published: April 2003

AbstractThe synthesis of polyacrylonitrile–poly(ethylene oxide) block copolymers was carried out with the use of modified initiator containing azo groups, being a product of reaction between poly(ethylene oxide) (mol wt 6000) with azobisisobutyronitrile. Effects of initiator concentration, temperature, and synthesis time on the yield, composition, and intrinsic viscosity of the copolymers were examined. To confirm the segmental structure of the obtained products, precipitation, fractionation, gel permeation chromatography, infrared, and 1H nuclear magnetic resonance methods were used. © 1993 John Wiley & Sons, Inc.
Functional polymers for colloidal application. VI. Syntheses and dispersing ability of lipomodified naphthalenesulfonate formaldehyde condensates
Authors: Kuo Ping‐Lin , Lin Jiaau‐Shahng , Wey Bih‐Shiuh 
Published: April 2003

AbstractButyl‐substituted naphthalenesulfonate formaldehyde condensates (C4NSF) with different molecular weights were synthesized. The structures were confirmed by NMR in terms of the appearance of the signal at δ = 3.3–4.0 ppm, and the molecular weights of the synthesized C4NSFs were compared by gel permeation chromatography (GPC). C4NSFs used as dispersants were compared to unmodified naphthalenesulfonate formaldehyde condensates (NSF) in their ability to disperse nonpolar particles (carbon black) and polar particles (TiO2) in water. Their dispersing ability was evaluated by both a viscosity method and a microscopy method. For dispersing carbon black in water, it was found that using C4NSFs as dispersing agents results in a lower viscosity, a lower yield value by the viscosity method, and a more homogeneous dispersion of particles as determined by microscopy. These results indicate that the butyl group enhances the dispersing ability of C4NSF. The effect of the butyl group on the dispersing ability of C4NSF was interpreted by the results of the measured adsorption amount that was also enhanced by the existence of the butyl group. For dispersing TiO2 in water, C4NSF results in a higher viscosity and a higher adsorption amount of the dispersed system than NSF. These phenomena were interpreted in terms of the hydrophobic interaction between the butyl groups and the bridging effect. © 1993 John Wiley & Sons, Inc.
Viscoelastic behaviour of vinylic copolymers of cellulose and their glass transition temperature by DSC
Authors: Flaqué C. , Montserrat S. 
Published: April 2003

AbstractThe viscoelastic response of some vinylic copolymers of cellulose prepared with vinyl acetatemethyl acrylate mixtures and with Ce(IV) ion as initiator, and native cellulose, were studied at 110 Hz in a range of temperatures from −120–100°C.The viscoelastic spectrum of cellulose shows the β‐relaxation that is not shown in its vinylic copolymers. We observed the same effect in the dielectric β‐relaxation.For the vinylic copolymers of cellulose, one viscoelastic relaxation attributed to the α‐relaxation of the grafted vinylic chains is observed. Some differences in the characteristics of this relaxation may be related to the composition of PVA/PMA vinylic side chains and to the ratio of cellulose in the copolymer. The plots of the Argand diagrams give us a better understanding of the viscoelastic behaviour of these materials. The results seem to indicate that the cellulose hinders the large‐scale motions of the vinylic chains grafted onto it. The glass transition temperature (Tg) determined by differential scanning calorimetry (DSC) also shows the same fact: the Tg of the vinylic copolymers of cellulose are higher than both the Tg of polyvinyl acetate–polymethyl acrylate copolymers (PVA–PMA) without cellulose and the Tg of some blends of cellulose and the PVA–PMA whose composition was as similar as possible to the cellulosic copolymers. The importance of the covalent bonds between cellulose and the vinylic side chains in the structural transitions are revealed. The present results are compared with the dielectric α‐relaxation that we described elsewhere. © 1993 John Wiley & Sons, Inc.