bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheological properties of polypropylene/high‐density polyethylene blend melts. II. Dynamic viscoelastic properties
Authors: Fujiyama Mitsuyoshi , Kawasaki Youtoku
Published: April 2003

Three kinds of isotactic polypropylenes with different MFI were melt‐blended with three kinds of high‐density polyethylenes with different MFI using a screw extruder and the dynamic viscoelastic properties were studied. The storage moduli G′(ω) of the blends showed second plateaus and the dynamic viscosities η′(ω) of the blends showed two‐step drops with increasing angular frequency ω. Such phenomenon was particularly notable for blend systems in which particles of lower viscosity were suspended in the disperse medium of higher viscosity and is considered to be the cause of abnormally large die swell.
Permeability properties of glycol chitosan membrane modified with thiol groups
Authors: Kubota Naoji , Ohga Kazuya , Moriguchi Mitsuaki
Published: April 2003

Water‐soluble glycol chitosan (GC), having the ability to form a membrane, was modified with 3,3′‐dithiodipropionic acid (DTPA), a functional group that causes the thiol ⟷ disulfide transition through redox reaction. The membrane derived from this modified GC was water‐insoluble. The permeabilities of KCI and socrose through the GC membrane modified with DTPA (MDTPA), the reduced membrane (MSH), and the oxidized membrane (MSS) were investigated. The permeability through the MSH membrane increased twofold relative to that through the MDTPA membrane, and the MSS membrane showed a 60% decrease in the permeability, which had increased in the case of the MSH membrane. The permeability of sucrose was lower and more changeable than that of KCl. These permeation phenomena were discussed from the viewpoint that the thiol ⟷ disulfide transition is responsible for the water content of each membrane.
Determination of molecular weight for poly(vinyl butyral) using size exclusion chromatography/low‐angle laser light scattering (SEC/LALLS) in hexafluoroisopropanol
Authors: Remsen Edward E.
Published: April 2003

Size exclusion chromatography/low‐angle laser light‐scattering (SEC/LALLS) determinations of molecular weight for poly(vinyl butyral) (PVB) using hexafluoroisopropanol (HFIP) as the polymer solvent and chromatographic mobile phase are described. The use of HFIP provided aggregate‐free SEC/LALLS chromatograms from which molecular weight distribution averages were calculated. Comparison of SEC/LALLS molecular weights determined in HFIP with similar data obtained using tetrahydrofuran as the polymer solvent and chromatographic mobile phase indicated that the former is more generally applicable for PVB of different vinyl alcohol content.
Prediction of cure time for a rubber cement used for conveyer belt splicing
Authors: Focke W. W. , Van Eeden G. S.
Published: April 2003

The evolution of bonding strength for a commercial cold vulcanizing rubber cement was determined using small–mscale simulated conveyer belt splicing. Peel and shear data obtained under isothermal conditions fit a modified Avrami model X = 1 − exp(−kt1/2), where X is the degree of ultimate shear or peel bond strength obtained and the rate constant k shows a typical Arrhenius type temperature dependence k = 42 exp(1670/T) min1/2 for peel strength, and k = 57 exp(−2000/T) min1/2 for shear strength. (T is the absolute temperature in K.) Bonding strength evolution under nonisothermal cure conditions can be estimated by integrating the general rate expression dX/dt = 0.5k2(1 − X)/(−ln[1 − X]).
Particle size control in emulsions of hydrocarbon soluble polymers
Authors: Falk John C. , Benedetto M. A.
Published: April 2003

Hydrocarbon solutions of polybutadiene, polyisoprene, and polystyrene may be converted into emulsions. The hydrocarbon solvent may then be removed by distillation. The molecular weight of the polymer controls the particle size of its emulsion. An increase in polymer molecular weight causes an increase in the particle size of its emulsion.
Epoxy resins based on aromatic glycidylamines. IV. Preparation of N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane from aniline and analysis of the product by GPC and HPLC
Authors: Podzimek Š. , Dobáš I. , Švestka Š. , Tkaczyk M. , Kubín M. , Štěrba V.
Published: April 2003

Epoxy resins containing N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) were prepared from aniline and epichlorohydrin and analyzed by GPC and HPLC. The product composition was compared with that of resins prepared from 4,4′‐diaminodiphenylmethane (DDM) and epichlorohydrin, which had been analyzed in our previous work. A new byproduct designated Y4 was isolated by semipreparative HPLC and identified by NMR and mass spectroscopy. The course of formaldehyde condensation with N,N‐dichlorohydrin of aniline (DCHA) was followed by GPC and HPLC and the mechanism of formation of Y4 was proposed on the basis of obtained results. Attention was also paid to the differences in reactivity of DCHA diastereoisomers.
Effects of fibers on the glass transition temperature of polyphenylene sulfide composites
Authors: Rebenfeld Ludwig , Desio Glenn P. , Wu James C.
Published: April 2003

The glass transition temperature (Tg) of polyphenylene sulfide (PPS), and of several commercial and model PPS prepregs with aramid, carbon, and glass fibers was studied by means of differential scanning calorimetry. The Tg of unreinforced PPS was found to range between 83–90°C, depending on source and molecular weight. The Tg of the commercial prepregs was depressed by about 3–5°C from that of the corresponding unfilled PPS, an effect that was ascribed to the plasticization of the PPS by one or more components of the fiber finish (size) that was assumed to have diffused into the PPS polymer. In the case of model prepregs prepared with finish‐free reinforcing fibers, an expected increase in Tg was observed. In model prepregs prepared with finished (sized) aramid fibers, the Tg was depressed as in the case of the commercial prepregs. With sized AS‐4 carbon fibers, the Tg was increased, but significantly less so than with unsized AS‐4 fibers. With sized glass fibers, the same slight increase in Tg was observed as with unsized glass fibers. The increase or decrease of Tg in all cases was a function of the fiber content in the model PPS prepregs.
Preceramic organoboron–silicon polymers
Authors: Hsu Ming‐Ta S. , Chen Timothy S. , Riccitiello Salvatore R.
Published: April 2003

Several boron‐containing organosilicon polymers were synthesized from a sodium‐coupling reaction of silicon and boron halides with and without alkyl halide in hydrocarbon solvents. The B–Si preceramic polymers were characterized using techniques such as IR, UV, and NMR spectrometry, gel permeation chromatography, elemental analysis, molecular weight measurement, and thermal analyses (TGA, DSC, DTA, and TMA). The chemical structures of the preceramic polymers were postulated based on the analytical results. Black ceramic materials were obtained from the precursor polymers upon thermal degradation at temperatures above 1000°C in an inert atmosphere. The precursor polymers had a ceramic yield of up to 70%. Thermogravimetric analysis of the ceramic material in air at a flow rate of 100 mL/min showed it was stable up to 1000°C with little weight gain or loss. Several methods were used to characterize the ceramic materials: XRD, solid NMR, high‐temperature DTA, elemental analysis, and acid digestion. The analyses indicated that the ceramic materials comprised a mixture of silicon carbide (SiC), silicon borides (SiB4, SiB6), and amorphous Si–B–C ceramics, with small amounts of silica and free silicon.
Liquid crystalline polymer laminates
Authors: Avramova N. , Fakirov S.
Published: April 2003

On the basis of a poly(ethylene terephthalate) copolyester containing 60 mol %p‐hydroxybenzoic acid, thin liquid crystalline films (160 μm thick) are obtained by melting the polymer at 300°C and chilling at 0°C. The undrawn films obtained have a high degree of orientation as evidenced by X‐ray measurements. Due to molecular orientation, these films are characterized by their excellent mechanical properties. In order to avoid losses in the mechanical strength due to increase in their thickness, laminates are prepared using thin liquid crystalline films. Lamination is carried out by annealing under pressure at 170°C for 6 h, resulting in samples with excellent mechanical properties regardless of their thickness. A method is proposed that makes it possible to combine the unique mechanical properties of thin films of liquid crystalline polymers with a lamination process in order to obtain thick and very strong materials.
Chemical modification of jute fibers. II: A study on the Fe2+/H2O2‐initiated graft copolymerization of methyl methacrylate, acrylonitrile, and acrylamide onto jute fibers
Authors: Moharana Sibendu , Tripathy S. S.
Published: April 2003

The study of graft copolymerization of methyl methacrylate, acrylonitrile, and acrylamide onto both defatted and bleached jute fibers using the ferrous ammonium sulfate / H2O2 redox initiator system has been made. To determine the optimum conditions of grafting, the effects of concentrations of ferrous ammonium sulfate, monomer, H2O2; time and temperature on percentage of graft yield have been studied. Acrylamide was found to graft onto the fiber only at a fixed ferrous ammonium ion concentration (5 × 10−4M). Kinetic studies showed that the rates of grafting follow the second‐order mechanism. The activation energies of the reactions were found to be 3.351 and 2.53 kcal/mol in the methyl methacrylate and acrylonitrile systems, respectively. The grafted fibers have been characterized by thermogravimetric analysis, IR spectroscopy, and XRD studies.
Thermal behavior and curing kinetics of poly(carbosilane)
Authors: Suwardie Herman , Kalyon Dilhan M. , Kovenklioglu Suphan
Published: April 2003

This study focuses on the thermal behavior and curing kinetics of a commercially available poly(carbosilane). Poly(carbosilane) is used for the production of silicon carbide (SiC) fibers by high‐temperature pyrolysis. Thermal characterization studies were carried out by employing a differential scanning calorimeter and thermogravimetric analyzer. The change in the chemical structure during curing with oxygen was studied with an infrared spectrometer. It was found that the uncured poly(carbosilane) would froth under a nitrogen environment around 450°C. Curing with oxygen, which results in crosslinking at the surface, enables the sample to retain its shape during high‐temperature pyrolysis. Curing was carried out at various temperatures, and the kinetics of the curing reactions were characterized.
Thermal conductivity of glass fiber reinforced polypropylene under high pressure
Authors: Yen C. L. , Tseng H. C. , Wang Y. Z. , Hsieh K. H.
Published: April 2003

The thermal conductivities of molten polypropylene and its glass fiber composites were measured by the compensating hot wire method. The testing apparatus empolyed was designed and tested in our laboratory. The measurements were carried out with temperatures ranging from 170 to 230°C and pressures from 1 to 2000 kg/cm2. The results show that the thermal conductivity increases with increasing pressure and glass fiber content, but is almost independent of temperature. The thermal conductivity data were fitted satisfactorily with a proposed empirical equation for polypropylene and Lewies‐Nielsen equation for the composites, respectively.
Translucent blends of chlorinated polyethylene with poly(vinyl chloride)
Authors: Tse A. , Laakso R. , Baer E. , Hiltner A.
Published: April 2003

Some experimental chlorinated polyethylene (CPE) resins that produced translucent blends with PVC were used to study the effects of CPE chlorine content and chlorine distribution on the morphology, optical clarity, and toughness of blends with PVC. The CPE resins were characterized in terms of the glass transition temperature, residual crystallinity, density, and refractive index. Increasing residual crystallinity and increasing chlorine content both increased the refractive index closer to that of PVC. A linear relationship was observed between the fourth power of the refractive index and the CPE glass transition temperature. With a phase‐separated blend morphology in all cases, improved transparency was achieved in this system by reducing the refractive index difference between CPE and PVC. Both haze and transparency showed the predicted linear dependence on the square of the refractive index difference. To a first approximation, modifications of the experimental CPE resins that improved optical transparency of the blends also tended to reduce the toughness enhancement.
Unified theory and guidelines on adhesion
Authors: Chung Frank H.
Published: April 2003

A new approach was proposed to consolidate the many adhesion theories into one coherent concept. The maximum attractive force between two sets of molecules (adhesion strength) is derived from the Lennard–Jones potential function and calculated with measured bond length and bond energy. It leads to two criteria for strong adhesion: intimate molecular contact of closer than 9 Å (necessary condition), and maximum attractive force with minimum potential energy (sufficient condition). The criteria conform to the key elements of most prior adhesion theories. Seven prior adhesion theories and their relevance to these two criteria were briefly reviewed/discussed. In order to draw up a set of guidelines on adhesion and supplement the missing pieces of information, 21 model polymers of varied functionality were synthesized to study (1) the effect of polar groups on adhesion and (2) the effect of polymer conformations on adhesion. The results indicate that polar groups are more effective in polymer backbone than in side chains for promoting adhesion. The presence of both hydrogen donors and acceptors in the same backbone maximizes adhesion. True (active) solvents enhance adhesion, cosolvents (latent solvents) boost adhesion by inducing favorable conformation of polymers in solution, but thinners (diluents) reduce adhesion. The set of guidelines covered the effects of functional groups, solvent blends, pigment loadings, adhesion promotion, and adhesion loss.
Dielectric properties above the glass transition for a series of epoxide prepolymers
Authors: Koike Tsuneo , Tanaka Ryohei
Published: April 2003

Dielectric properties above the glass transition have been investigated for a series of bisphenol‐A type epoxide prepolymers (388 ≤ M̄w ≤ 2640). Dielectric measurements were performed over a frequency range of 50 Hz–1 MHz using a vertical parallel plate cell which was constructed in the laboratory. The dielectric α‐relaxation for each prepolymer fits the empirical model of the Havriliak–Negami equation. The temperature dependence of the dielectric relaxation time τ is described by the Williams–Landel–Ferry (WLF) equation as well as that of the direct current conductivity σ, which can be measured using the same cell. The relationship between τ and σ, σ· τm = const, is derived from experimental results. The exponent m, which depends on the molecular weight of the prepolymer, is considered to correspond to the ratio of the segmental mobility to ionic mobility. The dielectric loss ε″ can be used as an indicator of the direct current conduction in the temperatures where the ionic component in ε″ becomes much larger than the dipole one.
The analysis of the surface chemical structure of biomedical aliphatic polyanhydrides using XPS and ToF‐SIMS
Authors: Davies M. C. , Khan M. A. , Domb A. , Langer R. , Watts J. F. , Paul A. J.
Published: April 2003

The surface chemical structure of a range of aliphatic polyanhydride films has been examined using XPS and ToF‐SIMS. The XPS data confirms the purity of the surface, and the experimental surface elemental ratios are in good general agreement with the known stoichiometry of the polyanhydrides. The ToF‐SIMS spectra of the polyanhydrides are shown to be significantly different. The SIMS data conforms to a systematic fragmentation, in both negative‐ and positive‐ion SSIMS spectra, occurring throughout the entire series of polyanhydrides examined. Radical cations are observed in the positive‐ion spectra. These results are discussed in terms of the general fragmentation patterns observed in the SIMS analysis of polymers. The combined use of ToF‐SIMS and XPS is shown, to provide a detailed insight into the interfacial chemical structure of these polyanhydrides.
On the dynamic mechanical behavior of poly(ethyl methacrylate) reinforced with kevlar fibers
Authors: Ribelles J. L. Gómez , Sebastià J. Mañó , Soler R. Martí , Pradas M. Monleón , Greus A. Ribes , Antón J. J. Suay
Published: April 2003

The dynamic mechanical relaxation spectra of a series of composites with a matrix of poly(ethyl methacrylate) reinforced with continuous Kevlar fibers present several characteristics that have been proposed in the literature regarding polymer composites as a proof of the existence of an interphase between the polymeric matrix and the filler with mechanical properties different from both: The α‐relaxation, associated with the glass transition of the matrix, is shifted in the temperature axis, and a peak appears in the tan δ vs. temperature plot, which was not present either in the matrix or in the fiber relaxation spectra. Nevertheless, a simple block model which does not include the existence of such an interphase is able to reproduce not only the dependence of the loss tangent and storage modulus with the fiber content, but also the shift of the α‐relaxation and the presence of the new α′ peak in the composites.
Studies on polyurea‐amide membranes
Authors: Joshi S. V. , Rao A. V.
Published: April 2003

Different polyurea‐amides were synthesized by interfacial polymerization of acid chloride, diamine, and diisocyanate. The polymers and the membranes were characterized for their RO/UF applications. Highly porous membranes could be prepared from the sulfuric acid‐based casting formulation and the membrane casting conditions were established. The resulting membranes are not asymmetric as they give high permeability to water and salt solutions. They are found to be resistant to many organic solvents, thus making them useful in concentration/separation applications. Whole milk, egg albumin and Na‐alginate were found to be rejected 100% by these membranes, while solutes of about 20,000 Mw are found to be rejected to the extent of 70‐80%.
In situ study of photopolymerization by fourier transform infrared spectroscopy
Authors: Udagawa Atsushi , Sakurai Fumio , Takahashi Tatsuo
Published: April 2003

The 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

The 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

The 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

The 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

A 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

The 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

The 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

Whereas 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

The 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

The 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

1,2,4,5‐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

Changes 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

Solid 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

Polystrene (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

Sorption 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

The 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

This 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

Single‐ 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

Defatted 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

The 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

An 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

The 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.
Spectroscopic studies on the effect of doping with iodine on metal chloride‐treated poly(vinyl alcohol)
Authors: Moharram M. A. , Rabie S. M. , El‐Hamouly W. S.
Published: April 2003

The ultraviolet and infrared spectra of films of PVA treated with Co(11), Ni(11), and Cu(11) and then doped with iodine were studied. The spectra of the films preheated in air at temperatures from 25 to 180°C for 2 h were investigated. The obtained data revealed that treatment of PVA with different concentrations of each of the mentioned metal salts causes profound spectral changes. The analysis of UV spectra showed that the intensity of the band at 280 nm decreases with increasing metal concentration. It was also found that doping with iodine results in an appearance of an additional peak at about 360 nm. Careful examination of the infrared spectra indicated that the crystallinity of the samples depends on the concentration of metals and is affected by temperature treatment.
Mechanical properties of i‐PP/CaCO3 composites
Authors: Maiti S. N. , Mahapatro P. K.
Published: April 2003

Tensile and impact behavior of CaCO3‐filled polypropylene was studied in the composition range 0–60 wt % filler. Tensile modulus increased while tensile strength and breaking elongation decreased with increase in CaCO3 content. The modulus increase and elongation decrease were attributed to increased filler–polymer interaction resulting in reduction in molecular mobility, while increased amorphization and obstruction to stress transfer accounted for the tensile strength decrease. Analysis of tensile strength data showed introduction of stress concentration in the composites. Izod impact strength at first increased up to a critical CaCO3 content, beyond which the value decreased. Surface treatment of CaCO3 with a titanate coupling agent LICA 12 enhances the adhesion of the filler and polymer, which further modifies the strength properties. Scanning electron microscopic studies indicated better dispersion of CaCO3 particles upon surface treatment, which effected the changes in the strength properties of the composites.
Parametric study of EAA polymer thin film deposition on carbon substrates in a fluidized electrode bed reactor
Authors: Desai V. M. , Mahalingam R. , Subramanian R. V.
Published: April 2003

Electrodeposition of ethylene‐co‐acrylic acid (EAA) polymer, as thin films on carbon particle substrates, was carried out in a fluidized electrode bed reactor. Feeder current, time of deposition, and flow rate of anolyte (i.e., bed expansion or bed porosity) were the key parameters investigated. The film characteristics were evaluated through SEM and FTIR analyses and the amounts determined by weighing. The effect of these parameters on the electrodeposition process is discussed, and optimum conditions for deposition are proposed. Also, a possible mechanism for electrodeposition, particularly for the EAA–carbon system, is discussed.
Estimation of diffusion coefficient for solute–polymer systems
Authors: Vahdat Nader
Published: April 2003

Diffusion coefficients are needed for the analysis of many mass transfer problems involving polymers. Since the diffusivity for such systems are strong functions of temperature and concentration, the analysis of these problems is greatly facilitated if predictive methods are available for the determination of the required diffusion coefficient. Because of the limitations of the theoretical approaches for estimating diffusivity, empirical correlation of solute–polymer diffusion coefficient data with physical properties of the solute were investigated. Chemical permeation measurements were made for several organic liquids through three elastomers (polychoroprene, butyl and nitrile rubber) at five different temperatures, ranging from 25 to 65°C. The collected diffusivities were correlated with liquid kinematic viscosity. Diffusivities (at different temperatures) depend mainly on the kinematic viscosity of solutes. The results also indicate a close relation between the variation of diffusivity and viscosity with temperature.
Distribution of higher‐order structures in injection‐molded polypropylenes
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo
Published: April 2003

Flexural test specimens were injection‐molded from six homoisotactic polypropylenes with MFI = 0.49‐25.1 dg/min under cylinder temperatures of 200‐320°C. Distributions in the flow direction of higher‐order structures such as crystallinity Xc, thickness of skin layer, a*‐axis‐oriented component fraction [A*], and crystalline orientation functions and distributions in the thickness direction of higher‐order structures such as Xc, β‐crystal contents, [A*], and crystalline orientation functions were studied. These higher‐order structures are inhomogeneous in the flow and thickness directions, which strongly influences the product properties such as mechanical and thermal properties. Molecular orientation process in injection molding was theoretically analyzed from a viewpoint of growth of recoverable shear strain at the gate and its relaxation in the cavity, which could considerably well explain the variations in the flow and thickness directions of the quantities such as thickness of the skin layer and crystalline orientation functions which express the degree of molecular orientation.
Surface characterization of plasma‐derivatized polyurethanes
Authors: Giroux Thomas A. , Cooper Stuart L.
Published: April 2003

The use of plasma deposition to introduce sulfonate groups to the surface of a polyurethane was attempted. In previous work, the bulk incorporation of sulfonate groups was found to improve the blood contacting properties of the base polyurethane but physical properties in the hydrated state were adversely affected. Plasma deposition schemes involving ammonia and sulfur dioxide were utilized in an attempt to incorporate sulfonate groups. Surface characterization by X‐ray photoelectron spectroscopy (XPS) and contact angle measurements was used to follow polymer surface rearrangement dynamics and to address the issue of plasma chemistry specificity. Concerns of reaction specificity were alleviated by using the plasma as a pretreatment which is followed by a chemical surface derivatization.