bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laminating resol varnishes made with crude multivalent phenol
Authors: Sridhar S. , Gadlinge Pavitra , Ratra M. C. 
Published: April 2003

AbstractDuring the carbonization process of a lignite source available in the southern part of India, a very cheap byproduct, crude multivalent phenol, was obtained. This crude consisting of substituted phenols and carbonaceous pitch was distilled to get a pitchfree distillate of about 60% yield. The distillate mixture was used along with other phenols for synthesis of resol varnish using a base catalyst. The properties of the resols were evaluated and found to be similar to that of pure phenol (C6H5OH) resins. The resol varnishes prepared were used for making cotton paper phenolic laminates by hand impregnation and the compression‐molding technique. The paper laminates have been evaluated for physical, chemical, mechanical, and electrical properties. The experimental investigations indicate that the distillate of multivalent phenol is a useful inexpensive substitute for conventionally used phenols in the manufacture of P3 grade laminates. © 1993 John Wiley & Sons, Inc.
Preparation and properties of macromolecular complexes consisting of [2‐(diethylamino)ethyl]dextran hydrochloride and potassium metaphosphate
Authors: Kubota Naoji , Kikuchi Yasuo 
Published: April 2003

AbstractIn aqueous solution [2‐(diethylamino)ethyl]dextran hydrochloride (EA) was reacted with potassium metaphosphate (MPK) to form a series of water‐insoluble macromolecular complexes (MC) at different hydrogen‐ion concentrations (EA–MPK system). EA was also reacted with MPK in the presence of CaCl2 (EA–MPK–CaCl2 system). The structure and properties of MC obtained were compared with each other; elemental analysis, IR spectroscopy, solubilities, thermogravimetric analysis, and scanning electron microscopy were used to characterize these complexes. The molecular structure and properties of each MC were dependent on the hydrogen‐ion concentration and whether the Ca2+ ion coexisted. It was suggested that MC prepared at acidic pH were composed of a relatively loose network including a small quantity of MPK, whereas those prepared at neutral and alkaline pH were composed of a relatively tight network including a large quantity of MPK. This seemed to be due to changes in the degree of dissociation and the conformation of EA and MPK with the hydrogen‐ion concentration. MC in the EA–MPK–CaCl2 system were supposed to have a rather tightly bound network structure due to the Ca2+ ion as compared with those in the EA–MPK system. © 1993 John Wiley & Sons, Inc.
Development of dynamic mechanical methods to characterize the cure state of phenolic resole resins
Authors: Follensbee R. A. , Koutsky J. A. , Christiansen A. W. , Myers G. E. , Geimer R. L. 
Published: April 2003

AbstractWe are interested in using dynamic mechanical analysis (DMA) to measure the degree of cure achieved by aqueous phenol‐formaldehyde (PF) resole resins as a result of previous exposures to various temperature‐humidity‐time regimes. We developed procedures that permit the obtaining of data that properly characterize and quantify the DMA behavior of these aqueous systems. Particularly important factors are substrate selection, sample clamping geometry, and sample humidification prior to analysis. In this report, we illustrate the problems encountered and the steps that we adopted to resolve them. We also present preliminary DMA data that illustrate some approaches for measuring the degree of cure achieved during previous resin exposures. One especially promising approach employs the area under the tan delta curve during isothermal scanning as an inverse measure of precure. © 1993 John Wiley & Sons, Inc.
Polyaminocarboxylic acids–Ce(IV) redox systems as an initiator in acrylamide polymerization
Authors: Erbil Candan , Cin Canan , Soydan A. Bahattin , Sarac A. Sezai 
Published: April 2003

AbstractAcrylamide polymerization by Ce(IV)‐polyaminocarboxylic acids, i.e., EDTA, DTPA, EGTA, and NTA, which have strong chelating properties, have been studied at different [H+], initiator concentration, and reaction time. Initiation of polymerization proceeds through the formation of the free radical after decarboxylation of the carboxyl group of polyaminocarboxylic acid. Results also indicate that the termination of the polymerization reaction is mainly mutual termination. Decrease of the rate of disappearance of the cerium(IV) is in the order of DTPA ≥ EDTA > NTA > EGTA. © 1993 John Wiley & Sons, Inc.
The thermooxidative stability of cured epoxy resins. I
Authors: Burton Bruce L. 
Published: April 2003

AbstractPrior studies have shown that for many epoxy resin systems significant oxidative degradation occurs in air at temperatures as low as 100°C and that thin oxidized surface layers serve as crack initiators in flexural samples at low strains and can reduce flexural strengths to less than 25% of the original values. This study was undertaken in an attempt to identify predominant degradation pathways and cured resin systems that are thermooxidatively stable in 125°C air. Based on flexural property retention and IR spectral data, the thermooxidative resistance ranking of D.E.R.*332 epoxy resin polymerized with the following is p‐toluenesulfonamide > 4,4′‐diaminodiphenyl sulfone or sulfanilamide > methylene dianiline ≫ triethylenetetraamine > 2,5‐dimethyl‐2,5‐diaminohexane. Oxidation of aliphatic amine‐cured D.E.R. 332 epoxy resin is initiated by electrophilic attack of oxygen on the lone‐pair electrons of the nitrogen to form an amine oxide. Polymer chain cleavage then occurs via Cope reactions. A newly proposed oxidative degradation pathway is described wherein the hydroxylamine products of Cope reactions are further oxidized to nitrones, which then decompose to amides via oxaziridine intermediates. Commercial antioxidants added to an aliphatic amine‐cured epoxy resin were ineffective, supporting the conclusion that the predominant degradation mechanism is not free radical in nature. © 1993 John Wiley & Sons, Inc.
Studies on macromolecular entanglement. II. Modification of macromolecular entanglements by heat treatment
Authors: Qian Baojun , Wu Zongquan , Hu Panpan , Qin Jian , Wu Chengxun , Zhao Jiongxin 
Published: April 2003

AbstractThe modifications of macromolecular entanglements in polyacrylonitrile copolymer fibers by heat setting in different mediums such as steam, hot air, and inert liquid are reported. The effects of applied tension, frozen internal stress, temperature, time, medium, crystallization, etc., during heat setting on the modification of entanglements are investigated in detail. These experimental results elucidate clearly the mechanism of entanglement and disentanglement and confirm fully the DSC method of swelling polymers for studying entanglement in solid polymer, as was previously published in Part I of this paper. © 1993 John Wiley & Sons, Inc.
Reactive ion etching of selected polymers in O2 and in CF4/O2
Authors: Hand B. , Long T. , Dems B. C. , Rodriguez F. 
Published: April 2003

AbstractA series of 17 polymers was etched in the reactive ion‐etching (RIE) mode. The etch rates were monitored using a laser interferometer. The gases used were oxygen alone and a mixture of carbon tetrafluoride with oxygen (8% O2). The polymers fell into three groups: the aromatics (polystyrene and derivatives), the aliphatics (methacrylates and vinyl acetate), and the cellulosics (methyl ether and nitrate). In oxygen with a power density of 0.25 W/cm2, the etch rates for the three groups fell in the range of 200–300 nm/min, 350–450 nm/min, and 500–850 nm/min, respectively. The etch rates were also measured at a power density of 0.50 W/cm2. The etch rates at the higher‐power density were about 75–80% higher than those at the lower‐power density. The etch rate in the fluoride mixture was about half that in the oxygen, all other parameters being the same. Plasticizers that lower the glass transition temperature of polymers based on vinyl chloride, methyl methacrylate, or styrene do not change the etch rate of the polymers very much. There is a slight increase in the rate for polystyrene and a slight decrease in the rate for poly(methyl methacrylate). All the effects of composition on etching rate can be correlated to a first approximation with the molar fractions of carbon and oxygen in the resist. © 1993 John Wiley & Sons, Inc.
Curing of unsaturated polyester resins—effects of comonomer composition. III. Medium‐temperature reactions
Authors: Huang Yan‐Jyi , Chen Chaur‐Jeng 
Published: April 2003

AbstractThe effects of comonomer composition on the curing kinetics of unsaturated polyester (UP) resins at 70–90°C were studied by differential scanning calorimetry (DSC) and infrared (IR) spectroscopy over the whole conversion range. One commercial UP resin, UP2660PF2, with cobalt promoter added and with 8.85 unsaturated CC bonds per polyester molecule, was used. It was found that a marked shoulder in the initial DSC rate profile, rather than that reported after the peak of rate profile for low‐temperature and high‐temperature reactions, appeared when the molar ratio of styrene to polyester CC bonds was greater than 1. With the initiator system accelerated by cobalt promoter, the formation rate of microgel particles would be enhanced at the early stage of reaction, as supported by the much higher conversion of polyester CC bonds than that of styrene by IR spectroscopy. Those relatively greater number of microgel particles tended to facilitate the intramicrogel crosslinking reactions, which would be independently identified from the initial DSC rate profile as a shoulder. Consequently, the reaction mechanism was elucidated by decomposing the reaction rate profile into two individual profiles accounting for the intramicrogel dominated and the intermicrogel dominated crosslinking reactions, respectively. © 1993 John Wiley & Sons, Inc.
Photochemically modified thin‐film composite membranes. I. Acid and ester membranes
Authors: Trushinski B. J. , Dickson J. M. , Childs R. F. , McCarry B. E. 
Published: April 2003

AbstractA photochemically active membrane was made by the interfacial copolymerization of 3‐diazo‐4‐oxo‐3,4‐dihydro‐1,6‐naphthalene disulfonylchloride and naphthalene‐1,3,6‐trisulfonylchloride with 1,6‐hexanediamine. The chemical functionality of the membrane surface was modified on irradiation of the surface of the membrane in the presence of various nucleophiles. Surface analysis techniques of attenuated total reflectance‐Fourier transform infrared and scanning electron microscopy have been used to monitor the changes in the chemistry of the thin‐film composite membranes. The surface functionality of the membrane was shown to affect the reverse osmosis flux and separation of various solutes. Results for membranes which have been converted to acid, and ester forms are presented. © 1993 John Wiley & Sons, Inc.
Studies on the swelling of cotton fibers in alkali metal hydroxides. III. Structure‐property relations in fibers swollen at 0°C
Authors: Sreenivasan S. , Iyer P. Bhama , Patel G. S. 
Published: April 2003

AbstractCotton fibers were subjected to swelling in various concentrations of LiOH, NaOH, and KOH at 0°C. Swollen fibers were characterized by measurements of physical, mechanical, and fine structural properties. Slack swelling in LiOH and NaOH produced tremendous changes in fiber properties. Clear‐cut swelling maxima, disorientation, and subsequent deterioration in tensile properties at and near the swelling maxima were evident in both LiOH and NaOH. On the other hand, KOH swelling did not produce any clear swelling maximum. Fibers swollen in this reagent showed better retention of tensile properties due to conducive changes in the structural parameters resulting from a lower but more uniform swelling. © 1993 John Wiley & Sons, Inc.
The short‐ and long‐term mechanical properties of filled and unfilled thermotropic liquid crystalline polymer injection moldings
Authors: Plummer C. J. G. , Wu Y. , Davies P. , Zülle B. , Demarmels A. , Kausch H.‐H. 
Published: April 2003

AbstractThe basic mechanical properties of a series of injection moldings of the thermotropic liquid crystalline polymer Vectra have been investigated to determine the effect of fillers on the short‐ and long‐term mechanical properties of these materials. Mineral‐filler addition results in a slight decrease in strength and an increase in stiffness in the flow direction, but has relatively little effect on the anisotropy. Glass fiber addition, on the other hand, may substantially lower the anisotropy depending on the degree of fiber orientation transverse to the flow direction. The glass fiber‐filled grade investigated also showed improved creep properties at high temperature compared with both the unfilled and mineral‐filled grades. © 1993 John Wiley & Sons, Inc.
The preparation and morphology of PPO–epoxy blends
Authors: Pearson Raymond A. , Yee Albert F. 
Published: April 2003

AbstractPoly(phenylene oxide) (PPO) was found to be miscible in diglycidyl ether of bisphenol A (DGEBA) based epoxy. The PPO–DGEBA system exhibited upper critical solution temperature (UCST) behavior. The cloud point temperatures were measured and found to be sensitive to the mol wt of the epoxy resin. A series of PPO‐modified epoxies were cured with piperidine at 160°C, which is above the cloud point temperature. Upon cure, two phase solids were formed, which contained discrete PPO particles. However, the two‐phase particulate morphology was not uniform and numerous large, occluded PPO particles were observed. In order to improve the uniformity, several styrene‐maleic anhydride copolymers were evaluated as potential surfactants for PPO‐DGEBA bends. The formation of a uniform, particulate morphology was facilitated by the addition of a styrene–maleic anhydride copolymer, containing a 10:1 ratio of styrene to maleic anhydride. To our knowledge, this is the first time that an emulsifying agent has been added to improve the morphology of thermoplastic modified epoxies. © 1993 John Wiley & Sons, Inc.
The preparation of poly[N(n‐butoxymethyl) methacrylamide] grafted silk fibers by polymerization using a low pH system
Authors: Tsukada Masuhiro , Shiozaki Hideki , Crighton John S. 
Published: April 2003

AbstractThe graft polymerizations of the N(n‐butoxymethyl) methacrylamide (BMA) monomer onto silk fibers were effected after reducing the pH of the grafting system to 2.5 by the addition of a formic acid solution. We compared the grafting efficiencies, surface characteristics, and thermal behaviors, as well as the whiteness levels and the extent of reduction of the rate of yellowing following UV irradiation, with the equivalent features of poly(BMA)‐grafted silk fibers, prepared under normal (pH 6) conditions. The grafting efficiency [as poly(BMA) weight gain] onto silk fiber that was attained was almost 100% through optimization of the pH environment in the polymerization system by the addition of formic acid. The stiffness of the silk fabrics observed, following the conventional grafting, was markedly higher than that of equivalent silks after the polymerization at pH 2.5. The rates of yellowness index increase, for these latter silk fabrics following UV irradiation were also reduced, specifically in the initial irradiation period (up to 60 h).The SEM of the grafted silk fabrics reveal the absence of granules on the surface of the grafted silk fiber, when the silk was grafted with poly(BMA), after reducing the pH of the grafting system to 2.5. These findings suggest that the BMA monomer was polymerized specifically within the silk fiber and not on the surface. It is suggested that the increase in the polymer weight gain, and the reduced adverse effect on the fabric handle, arise because of the modified polymer location. © 1993 John Wiley & Sons, Inc.
Aromatic polyimides: Synthesis, characterization, and evaluation of electric strength
Authors: Bjellheim Peter , Helgee Bertil 
Published: April 2003

AbstractAromatic polyimides have been synthesized via the formation of polyamic acids in solution. This solution was cast into films that were thermally imidized. The imidization process was monitored using FTIR. The degree of imidization was also determined with thermo‐gravimetric analysis. The electric breakdown field strength was tested under ac and dc conditions. Ac electric breakdown field strength measured in transformer oil was shown to follow a power‐law dependence on film thickness. This dependence was not affected by the molecular mass of the polymer but changed with the degree of imidization and the electron‐accepting properties of the diamine. High ac breakdown field values of polymides were obtained in dibutyl phthalate medium due to the suppression of partial discharges that occurs under these conditions. Measurements on films with thicknesses up to 60 μ showed no thickness dependence. No significant influence of the chemical structure on the break‐down field strength was observed under these conditions. Breakdown field measurements under dc conditions showed high values, which were in good agreement with the peak values of the ac measurements in dibutyl phthalate. This indicates similarities in the intrinsic ac and dc breakdown processes. © 1993 John Wiley & Sons, Inc.
Surface and interfacial FT–IR spectroscopic studies of latexes. VI. Orientation and spatial distribution of acid functionalities at the film–substrate interface
Authors: Thorstenson Timothy A. , Tebelius Lara K. , Urban Marek W. 
Published: April 2003

AbstractFormation of dimeric carboxylic acid functional groups observed at the film‐substrate interface of ethyl acrylate/methacrylic acid (EA/MAA) and butyl acrylate / methyl meth‐acrylate / methacrylic acid (BA/MMA/MAA) latex films prepared on a high surface tension substrate, such as liquid mercury, is observed when sodium dioctyl sulfosuccinate (SDOSS) is employed as the synthetic emulsifier. To address the acid species assembled at this interface due to the inability of SDOSS to effectively alleviate interfacial tension and to assess the orientation and spatial configuration of acid groups species at the interface, polarized attenuated total reflectance, Fourier‐transform infrared spectroscopy (ATR FT–IR) is employed. It is found that the acid dimer rings adopt an average “on‐edge” configuration at the interface with the hydrogen‐bonded rings perpendicular to the film‐mercury interface. This configuration serves to provide not only the necessary interfacial acid‐dimer layer, but also facilitates favorable ring–ring interactions between groups of opposite polarity on adjacent rings. This study indicates that the on‐edge configuration may also serve to reduce unfavorable interactions between the polar acid functionality and the less polar components present in the bulk of the coalesced latexes. © 1993 John Wiley & Sons, Inc.
Measurement of thermophysical properties of polyester cured with styrene in the range 300–450 K
Authors: Hilal A. S. , Abousehly A. M. , Dessouky M. T. , Abd El‐Hakim A. A. 
Published: April 2003

AbstractA pulse method for the simultaneous determination of thermal diffusivity, α, specific heat capacity, Cp, and thermal conductivity, λ, are measured for a series of curing of polyester and styrene in the presence of 10, 20, and 30% carbon black in the temperature range 300–450 K. The results show a dependence of the above‐mentioned properties on temperature and composition. The mechanism of heat transfer through the specimens is also discussed. © 1993 John Wiley & Sons, Inc.
Dissolution and crystallization behavior of poly(ethylene terephthalate)–diluent mixtures
Authors: Vane L. M. , Rodriguez F. 
Published: April 2003

AbstractThe solution crystallization kinetics and crystal dissolution behavior of three grades of poly (ethylene terephthalate) in N‐methyl–2‐pyrrolidinone were studied were using turbidimetric and calorimetric methods. The influence of concentration on the equilibrium dissolution temperature was described using Flory's melting point‐composition relationship. The effect of the solvent alkyl group was also investigated. N‐ethyl‐2‐pyrrolidinone was found to be a better solvent than N‐ethyl–2‐pyrrolidinone or N‐cyclohexyl–2‐pyrrolidinone for poly (ethylene terephthalate). From the calorimetric experiments, it was determined that two crystallization processes (primary and secondary crystallization) were responsible for the total crystallinity. The primary process dominated the early stages of the crystallization process and accounted for the majority of the final crystallinity for lower polymer concentrations. Based on coherent secondary nucleation theory, the effect of the crystallization temperature on the primary crystallization rate constant was quantified in terms of a temperature coefficient. This temperature coefficient was found to be relatively insensitive to PET concentration, PET structural impurities, and solvent alkyl group. © 1993 John Wiley & Sons, Inc.
Acrylonitrile–acrylic acids copolymers. I. Synthesis and characterization
Authors: Bajaj P. , Paliwal D. K. , Gupta A. K. 
Published: April 2003

AbstractAcrylonitrile (AN) was copolymerized with acrylic acid (AA), methacrylic acid (MAA), and itaconic acid (IA) by the aqueous suspension method at 40°C with ammonium persulfate and sodium metabisulfite as the redox initiator. The reactivity ratios for the AN–AA and AN–IA systems were also calculated by the Finemann–Ross and the Kelen–Tüdõs methods. Higher r2 (AA) for the AN–AA system in comparison to r2 (IA) for the AN–IA system indicates greater reactivity of AA toward the propagating species. The influence of co‐monomers on intrinsic viscosity, tacticity, and number‐average sequence lengths was studied. 13C‐NMR spectra revealed that AN copolymers having approximately 2 mol % of AA have a greater percentage (>30%) of isotactic content than of homopolyacrylonitrile. Tacticity has also been calculated from infrared spectra of the polymers using stereospecific absorption bands at 1250 and 1230 cm−1. © 1993 John Wiley & Sons, Inc.
Preparation and properties of Si‐containing copolymer for near‐UV resist. III. Maleimide/silylstyrene copolymer
Authors: Chiang Wen‐Yen , Lu Jin‐Yuh 
Published: April 2003

AbstractPoly(maleimide‐alt‐p‐trimethylsilyl‐α‐methylstyrene) (α‐PMTMMS) and poly(male‐imide‐alt‐p‐trimethylsilylstyrene) (PMTMSS) were synthesized for positive/negative near‐UV resists in the containing of diazonaphthoquinone sulfonate (DNS). The electron‐rich styrenic monomers tend to undergo alternating copolymerization with an electron‐poor maleimide monomer. The chain‐stiffening effects of the maleimide and α‐methylstyrene group were responsible for high thermal stabilities. A higher glass transition temperature of 226°C was found in α‐PMTMMS. Lithographic positive/negative images were obtained that were stable to temperatures higher than 200°C. Excellent solubility in aqueous base was observed with PMTMSS at 10.3 wt % silicon content and an oxygen‐plasma etching rate of 1:12 compared to hard‐baked HPR–204. © 1993 John Wiley & Sons, Inc.