bluuebunny/crossref_metadata_2025_split huggingface dataset:
In situ study of photopolymerization by fourier transform infrared spectroscopy
Authors: Udagawa Atsushi , Sakurai Fumio , Takahashi Tatsuo 
Published: April 2003

AbstractThe Fourier transform infrared (FTIR) in situ method was developed for the investigation of photopolymerization. Ultraviolet (UV) cure of a mixture of a cycloaliphatic epoxide, a 2‐ethylhexyl acrylate, and photoinitiators, which forms simultaneous interpenetrating polymer network (IPN), was monitored while the sample was irradiated with UV light. Triphenylsulfonium salt and benzoin ether were used as photoinitiators. For the sake of comparison, similar experiments were performed for the epoxide with the triphenylsulfonium salt photoinitiator and the acrylate with the benzoin ether photoinitiator. The epoxy photopolymerization was monitored using an epoxy CH stretching band at 3005 cm−1 and a ring vibration band at 790 cm−1. The acrylic photopolymerization was monitored using a CC stretching band at 1637 cm−1. The epoxy conversion was less than 60% when the acrylic polymerization was completed in the IPN.
Entry and exit rate coefficients in emulsion polymerization of styrene
Authors: Asua J. M. , De La Cal J. C. 
Published: April 2003

AbstractThe rate coefficient for entry of radicals into the polymer particles and the radical exit rate coefficient were estimated in seeded emulsion polymerization of styrene. The dependence of both coefficients on the particle size was used in an attempt to discriminate between the models proposed for these coefficients. The results obtained were found to be consistent with a model in which the entry of radicals into the polymer particles occurs by the propagational mechanism and the radicals desorb from the polymer particles by diffusion. A comparison between the estimated values of the coefficients and those calculated theoretically using the equations derived from the corresponding mechanisms was performed.
A correlation between critical end‐to‐end distance for entanglements and molecular chain diameter of polymers
Authors: Zang Yong‐Hua , Carreau Pierre J. 
Published: April 2003

AbstractThe critical molecular weight Mc of 36 flexible and semirigid polymers has been studied. A unique correlation between the critical end‐to‐end distance 〈Rc〉 for entanglements and the average polymer chain diameter D is found. This correlation is discussed in the light of the reptation concept.
Acoustic emission in bonded elastomer discs subjected to uniform tension. II
Authors: Kakavas P. A. , Chang W. V. 
Published: April 2003

AbstractThe aim of this paper is to evaluate and analyze the growing and tearing mechanisms of existing microvoids within bonded elastomer discs using the acoustic emission (AE) technique. It was shown that the existing microvoids in the deformed disc are responsible for the reduction of the apparent modulus (M) of the elastomer disc, the stress softening, and the hysteresis when the material is subjected to triaxial stress conditions. A series of experiments performed in our laboratory confirmed the existence of microvoids within the deformed bonded unfilled nitrile rubber discs. Valuable information about the size of the deformed voids in the material was obtained using the frequency spectrum of the detected AE signals. More information on the tearing of voids was extracted from the count, event, amplitude, and duration time distribution of the received AE pulses.
An ESR study of the film formation steps of vapor deposition polymerization of polyamic acid
Authors: Iijima Masayuki , Takahashi Yoshikazu , Ueda Hisashi 
Published: April 2003

AbstractA film of polyamic acid is formed by vapor deposition polymerization of pyromellitic dianhydride (PMDA) and 4,4′‐diaminodiphenyl ether (ODA). We have taken ESR spectrum during the polymerization process and compared it with the ESR spectrum of films obtained from solution polymerization. In the intermediate polymers during vapor deposition polymerization, the amide bond (CONH) is coplanar with the benzene ring and two protons in the PMDA molecule. This intermediate polymer has one unpaired electron that interacts with the two nitrogen nuclei equally. On the other hand, in the polymer obtained by solution polymerization, the amide bond and the benzene ring of PMDA are not coplanar. In this polymer, too, some of the molecules have an unpaired electron that seems to have almost no coupling with NH groups. These results imply that the polymer formation via vapor deposition proceeds through different intermediates and different molecular configurations from that via the solution process.
Comparative studies on the thermal stability of commercial poly(vinyl chloride)
Authors: Al‐Ghamdi Ali M. S. , Al‐Diab Salem S. 
Published: April 2003

AbstractThe thermal stability of a polymer is a characteristic function of its structure. In this study molecular weight measurements, differential thermal analysis, dehydrochlorination, and IR are the methods used to determine the thermal stability of commercial PVC products. The study was performed on Saudi Basic Industries Corporation (SABIC) products as well as established products for comparative purposes. The study showed comparable results for both types of products.
Complexes of starch polysaccharides and poly(ethylene co‐acrylic acid): Structural characterization in the solid state
Authors: Shogren R. L. , Thompson A. R. , Greene R. V. , Gordon S. H. , Cote G. 
Published: April 2003

AbstractThe structural characterization of model complexes of amylose (AM) and amylopectin (AP) with poly(ethylene‐co‐acrylic acid) (EAA) was undertaken in order to better understand the interactions that occur between the polysaccharides and EAA in starch‐EAA‐polyethylene films. X‐ray diffraction and CP/MAS 13C‐NMR studies showed that precipitates from solution mixtures of AM and EAA form crystalline, helical V ‐type inclusion complexes. The proportion of AM forming the V ‐type complex in the EAA/AM blends, estimated from shifts in the C1 resonance of AM, increased with increasing EAA/AM ratio, reaching a value of about 80% at EAA/AM = 0.5 (w/w). Similar measurements for EAA/AP complexes showed < 10% V structure. Approximately 80% of the AM and 4% of the AP in these blends was resistant to amylase digestion, in good agreement with their V ‐structure contents as determined above. Resonances at 184 and 181 ppm were observed for the carboxyl carbon of EAA in the EAA/AM and EAA/AP complexes. The resonance at 181 ppm, which was not observed in pure EAA, probably reflects greater shielding of the carboxyl inside the polysaccharide helix as well as changes in hydrogen bonding. The intensity of this peak was 2–3 times larger for the EAA/AM than for the EAA/AP complexes. FTIR experiments suggest that most (> 50%) of the EAA carboxyl groups were hydrogen bonded to polysaccharide hydroxyl groups in both AM and AP complexes when EAA/polysaccharide < 1.
Surface and interfacial FTIR spectroscopic studies of latexes. II. Surfactant–copolymer compatibility and mobility of surfactants
Authors: Evanson Kevin W. , Thorstenson Timothy A. , Urban Marek W. 
Published: April 2003

AbstractWhereas molecular level interactions between sulfonate groups of SDOSS surfactant and COOH groups of EA/MMA copolymer have been discussed in part I of this series, the major focus of this work is to establish the effect of compatibility on the distribution of surfactants at the film–air and the film–substrate interfaces. It is found that the exudation of anionic surfactants is inhibited in neutralized ethyl acrylate/methacrylic acid latex films. On the other hand, nonionic surfactants do not exhibit enrichment at the film interfaces. The inhibited exudation of anionic surfactants is attributed to the increased compatibility resulting from surfactant penetration into the swollen latex particles. This is followed by the formation of solubilized polymer–surfactant complexes through the adsorption of surfactant onto the hydrophobic polymer segments. The effect of neutralization of the carboxylic acid groups on the exudation of anionic surfactants suggests the formation of hydrophobic interactions that overwhelm surface tension effects and prevent surfactant enrichment at either interface.
Continuous heating transformation (CHT) cure diagram of an aromatic amine/epoxy system at constant heating rates
Authors: Wisanrakkit Guy , Gillham John K. 
Published: April 2003

AbstractThe overall reaction kinetics of a high‐Tg tetrafunctional aromatic diamine/difunctional epoxy system (maximum glass transition temperature, Tg∞ = 182°C), which can satisfactorily describe the rate of the reaction in both kinetically and diffusion‐controlled regimes, had been determined earlier from isothermal conversion/Tg data by differential scanning calorimetry (DSC). The mathematical expression of the kinetics, together with the unique one‐to‐one relationship between Tg and chemical conversion, is used to calculate the material's Tg vs. time under heating at constant rates. For a heating scan from below Tg0 (the glass transition temperature of the unreacted material), initial devitrification corresponds to the reaction temperature (Tcure) first passing through the Tg of the reacting material; vitrification corresponds to Tg becoming equal to the increasing Tcure after initial devitrification; and finally, upper devitrification corresponds to Tg eventually falling below the rising Tcure. The results of the calculation correlate well with the available experimental data of the dynamic mechanical behavior of the material during temperature scans at constant rates that were obtained by the torsional braid analysis (TBA) technique. Tg is calculated to remain slightly higher than Tcure after vitrification due to the influence of diffusion control, the difference being greater for lower heating rates. The limiting heating rate with no initial devitrification and that with no vitrification are also calculated.
XPS characterization of surface fluorinated poly(4‐methyl‐1‐pentene)
Authors: Mohr J. M. , Paul D. R. , Taru Y. , Mlsna T. E. , Lagow R. J. 
Published: April 2003

AbstractThe fluorinated surface layer of poly(4‐methyl‐1‐pentene) membranes exposed to a dilute stream of fluorine gas has been characterized with X‐ray photoelectron spectroscopy. The concentration and profile of reacted fluorine as a function of exposure time is determined. A computer routine was employed to deconvolute the poorly resolved carbon spectra after various fluorine exposure times. The concentrations of mono‐, di‐, and trifluorocarbon groups thus determined were used to propose specific structures of PMP at the surface after 1 and 15 min of fluorination. The carbon spectra collected at electron takeoff angles of 15°, 30°, and 90° were also deconvoluted, giving insight into the placement of fluorine as a function of depth. Oxygen is incorporated into the polymer during the fluorination reaction, and the O1s spectra was deconvoluted to determine how the oxygen is bound.
Interfacial polyfunctional condensation: Effect of the reaction conditions
Authors: Chern Yaw‐Terng , Chen Leo‐Wang 
Published: April 2003

Abstract1,2,4,5‐Benzenetetra acyl chloride (BTAC) was prepared from pyromellitic anhydride and phosphoric chloride. The behavior in interfacial polycondensation of 4,4′‐methylene dianiline (MDA) or ethylene diamine (EDA) in water with BTAC in dichloromethane with tetrabutyl ammonium chloride (TBAC) as the catalyst was examined with Fourier transform infrared spectroscopy (FTIR), fast atom bombardment mass spectroscopy (FABMS), and scanning electron microscope (SEM). A heat‐resistant film can be obtained by successive heating of the resulting thin films.Because BTAC is a tetrafunctional compound with high reactivity, the interfacial reaction is a competitive reaction of hydrolysis and amidation among the reacting groups. The optical density of FTIR spectra was employed for calculating the percentage of hydrolysis. The hydrolysis is suppressed when (1) the temperature is decreased, (2) sodium carbonate is added, (3) the proportion on the concentration of diamine is increased relative to the concentration of BTAC, (4) the diamine solution is agitated, and (5) TBAC is added to the diamine (as).The percentage of hydrolysis can be controlled at will, e.g., 50%. A high‐resistant polyimide can be prepared through thermal treatment in a nitrogen atmosphere. By increasing the concentration of the reactants or using a good sovlent, the film obtained is thicker, but in our system, the maximum thickness of the film seldom exceeded 20 pm.
Comparative crystal morphology study using WAXS and CDT techniques
Authors: Johnson A. , Popoola A. V. 
Published: April 2003

AbstractChanges brought about in the crystal morphology of drawn (oriented) PET fibers following both heat and liquid treatments were studied using wide angle X‐rays and critical dissolution time techniques. The results obtained showed that the two techniques were sensitive to different but closely related morphological properties of the polymer, the former being sensitive to the apparent degree of the crystalline content, and the latter, a measure of the size of such crystallites that were produced.
Studies on irradiation of agar–agar in the solid state: On the changes of thermal property of agar–agar hydrogel produced by irradiation
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractSolid agar–agar was irradiated with 60Co gamma‐rays, and effects of radiation on the cross‐links of agar–agar molecule were studied by measuring the melting and setting points of the agar–agar hydrogel at different radiation dose and elapsed time after irradiation.
Particle size distribution and molecular size distribution of polymers in soap‐free emulsion polymerization of styrene
Authors: Chiu Wen‐Yen , Lai Sun‐Mou , Chen Leo‐Wang , Chen Chao‐Cheng 
Published: April 2003

AbstractPolystrene (PS) particles, generated from soap‐free emulsion polymerization of styrene monomer, water, and potassium persulfate, were investigated by photon correlation spectroscopy (PCS) and TEM. The particle size distribution (PSD) was quite uniform. From the data of PCS, it could be said that lots of particles flocculated in the final stage of reaction. It was also deduced from the molecular weight distribution (MWD), measured by GPC, that, during the early stage of reaction, molecules with low molecular weight (<4000) might exist and the particles were perhaps formed through micellar‐type nucleation mechanism. When initiator concentration increased, reaction rate increased but weight average molecular weight, tensile modulus, and elongation decreased. The number density of particles was found to be proportional to 0.49 power of initiator concentration. However, monomer concentration did not seem to have any great effect on all of them above.
Molecular transport of some industrial solvents through a polyurethane membrane
Authors: Aithal U. Shanthamurthy , Aminabhavi Tejraj M. 
Published: April 2003

AbstractSorption and transport studies of several industrial solvents have been investigated through a Uralite 3142 polyurethane. Diffusion coefficients have been measured for the preswollen and fully swollen polyurethanes. For majority of solvents, non‐Fickian transport mode was observed and these results have been interpreted in terms of polymer‐penetrant interactions. Temperature‐dependent diffusion parameters followed the Arrhenius relation from which energy of activation have been obtained. The Flory–Rehner equation, in spite of its limitations, has been found to be useful to estimate the molar mass between crosslinks of the network polyurethane.
Particle size as it relates to the minimum film formation temperature of latices
Authors: Jensen D. P. , Morgan L. W. 
Published: April 2003

AbstractThe relationship between the particle sizes and minimum film formation temperature (MFT) of polymer colloids was studied. Early workers had developed theoretical models predicting small particle colloids should coalesce easier and have lower MFTs than those of large colloids. Early published work examining this question reported that MFT was independent of particle size. In 1990, Eckersley and Rudin, using monodisperse acrylic latexes ranging from 148–1234 nm, reported finding that MFT was a function of particle size as predicted.We synthesized a series of monodisperse acrylic copolymer latexes ranging from 63–458 nm and measured MFTs of these latexes and blends of them. We have also found particle size does affect MFT with small particle polymer colloids having lower MFTs than larger ones. Our results differ somewhat in that the MFTs of our latexes are below the glass transition temperatures (Tg) of the polymers while Eckersley et al. report MFTs above Tg.
MWD control in continuous free‐radical polymerizations through forced oscillations of the transfer agent feed
Authors: Gugliotta L. M. , Couso D. A. , Meira G. R. 
Published: April 2003

AbstractThis paper studies the effect of forced‐feed oscillations of an intentionally added chain transfer agent on isothermal free‐radical polymerizations carried out in continuous stirred‐tank reactors (CSTRs). A solution polymerization is first considered. The influence on the molecular weight distribution (MWD) of rectangular waves and impulsive trains of the transfer agent feed is theoretically and experimentally investigated. The main result is that (within certain limits) the average polydispersity can be increased at will with respect to its corresponding steady‐state (SS) value, without affecting the average number average chain length or the instantaneous monomer and initiator conversions. This result is extended to an emulsion copolymerization under sinusoidal oscillations of the transfer agent feed, where the “decoupling” between the average molecular polydispersity and other parameters (conversions, number average molecular weight, average number of branches per molecule, and the particle‐size distribution) is also produced.
Effect of yarn geometry and fiber properties on tensile behavior of cotton yarns swollen and stretched in aqueous zinc chloride
Authors: Iyer P. Bhama , Sreenivasan S. , Patel G. S. , Iyer K. R. Krishna , Patil N. B. 
Published: April 2003

AbstractSingle‐ and two‐ply yarns of different counts were swollen slack under optimum conditions in aqueous zinc chloride and stretched back to original length. While two‐ply yarns showed an improvement in tenacity that was less pronounced in finer counts, single yarns always showed a fall in tenacity. Various properties of the treated yarns like packing fraction, fiber and yarn orientation, cross‐sectional morphology, etc. were evaluated to ascertain the likely factors responsible for the differential behavior of the chemically treated single‐ and two‐ply yarns.
Infrared spectra of jute stick and alkali‐treated jute stick
Authors: Roy A. K. , Sen S. K. , Bag S. C. , Pandey S. N. 
Published: April 2003

AbstractDefatted jute stick was treated with sodium hydroxide solution (2% w/v) at ambient temperature (∼ 32∼C) and boiling water bath temperature (95–97°C). Infrared (IR) spectra of defatted jute stick and alkali‐treated jute stick were studied. The IR spectra of the alkalitreated jute stick were conspicuous by the absence of the 1730 cm−1 band, as compared to that of jute stick. Another characteristic feature of the alkali treated jute sticks is the absence of the band at 1240 cm−1, which is replaced by the 1265 and 1225 cm−1 bands; other bands in the above samples also recorded significant changes.
Permeation of carbon dioxide in a thermotropic liquid‐crystalline polyester
Authors: De Candia F. , Capodanno V. , Renzulli A. , Vittoria V. 
Published: April 2003

AbstractThe transport properties of a thermotropic liquid crystalline polyester have been analyzed using carbon dioxide as permeant. Carbon dioxide, in the analyzed range of temperature and pressure, gives some information on the phase organization of the system. The structural model compatible with the transport behavior assumes the presence of a disordered phase within the well‐ordered liquid crystalline domains. The same structural model was previously suggested on the basis of the transport behavior of methylene chloride vapors in nematic and smectic liquid‐crystalline polymers.
Elongational flow studies on the molecular properties of collagen and its thermal denaturation
Authors: Sasaki Naoki , Atkins Edward D. T. , Fulton W. Stephen 
Published: April 2003

AbstractAn elongational flow method established in polymer physics was applied to study dynamic structure and properties of biopolymers in solution. Type I collagen solutions in the dilute to semidilute region are studied in elongational flow fields, generated in a Taylor four‐roll mill, for temperatures from 20°C through the melting temperature to 60°C. A nonlocalized birefringent signal, characteristic of stiff molecules, is observed at all temperatures. The conformational changes as a function of temperature can be divided into two separate temperature dependent stages. In stage I, at lower temperatures, the collagen molecule behaves as a rigid rod and the birefringent signal Δn rises as a function of increasing strain rate ε. Throughout this stage the type of molecular interaction in semidilute solution does not change but the rate of interaction is increased by thermal excitation. In stage II, a characteristic criticality in the Δn vs. ϵ plot is observed. For strain rates up to a characteristic value, ϵ0, the birefringence remains zero and for ϵ>ϵ0 whole field bright birefringence is observed. The plateau values of birefringence, Δnp, at high strain rates in the Δn vs. ϵ curve decreased with rising temperature in stage II. This criticality in behavior and the decreasing tendency in Δnp with temperature are explained by the collagen molecule changing to a hinged‐rod conformation. Thus the untwining of collagen as a function of temperature initiates at several places simultaneously, probably at specific amino acid sequences, within the collagen rodlike molecule.
Polyamine‐modified urea‐formaldehyde resins. I. Synthesis, structure, and properties
Authors: Ebewele Robert O. , Myers George E. , River Bryan H. , Koutsky James A. 
Published: April 2003

AbstractThe objective of this study was to improve the durability and stability of urea–formaldehyde‐bonded wood products by decreasing the internal stress developed during resin cure and by improving the ability of the cured resin to withstand cyclic stresses. This paper presents initial results from modifying a urea–formaldehyde resin by incorporating di‐ and trifunctional amines. The amines were incorporated by adding them as amines during resin synthesis, by adding urea‐capped amines during resin synthesis, and by using amine hydrochlorides as acidic curing agents. Addition of amines during resin synthesis produced uncurable resins. However, modification with urea‐capped amines or curing with amine hydrochlorides provided cure rates comparable to that of unmodified resin cured with ammonium chloride. These modifications also reduced the tendency of the resin to crack and fracture and substantially improved the resistance of bonded joints to cyclic stress imposed by cyclic wet–dry exposures. Resins cured with amine hydrochlorides had lower formaldehyde liberation than those cured with ammonium chloride. Thus, incorporation of flexible di‐ and triamines offers promise for improving the durability and stability of urea–formaldehyde‐bonded wood products.