bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analytical solution of the molecular weight distribution of reversible step growth polymerization in homogeneous continuous flow stirred tank reactors
Authors: Khanna Ashok , Kumar Anil 
Published: April 2003

AbstractMole balance for the molecular weight distribution in homogeneous continuos‐flow stirred tank reactors (HCSTRs) for reversible step‐growth polymerization has been written. The relation for the moment generating function G is found to be a nonlinear ordinary differential equation and has been solved analytically. The solution of the MWD of the polymer formed is shown to be valid even if the condensation product is removed. At equilibrium, the solution reduces to the Flory distribution. The computations show that the polydispersity of the polymer first increases with the residence time θ of the reactor, but, for large θ, it reduces to the equilibrium value after undergoing a maximum.
Measurement of diffusion of antioxidants in isotactic polypropylene by isothermal differential thermal analysis
Authors: Schwarz T. , Steiner G. , Koppelmann J. 
Published: April 2003

AbstractThe diffusion of the phenolic antioxidant 1,3,5‐tris(3,5‐di tert‐butyl‐4‐hydroxybenzyl)mesitylene (IRGANOX 1330) in extruded sheets of isotactic polypropylene (iPP) was investigated over the temperature range from 80 to 120°C by isothermal differential thermal analysis (DTA). The measurements showed a clear relation between oxidation induction time and oxidation maximum time (both determined by isothermal DTA) and the concentration of the stablizer. It was possible to calculate the diffusion coefficients and the activation energy of diffusion of IRGANOX 1330 in iPP by measuring the oxidation maximum times across stacks of isotactic polypropylene sheets.
Etching of plasma‐polymerized tetrafluoroethylene, polytetrafluoroethylene, and sputtered polytetrafluoroethylene induced by atomic oxygen [O(3P)]
Authors: Wydeven Theodore , Golub Morton A. , Lerner Narcinda R. 
Published: April 2003

AbstractA study was carried out of the surface recession (etching) of thin films of plasma‐polymerized tetrafluoroethylene (PPTFE), polytetrafluoroethylene (PTFE), and ion‐beam sputter‐deposited polytetrafluoroethylene (SPTFE), exposed to atomic oxygen [O(3P)] downstream from a nonequilibrium radio‐frequency O2 plasma. At 22°C, the etch rates for PTFE, SPTFE, and PPTFE were in the ratio of 8.7 : 1.0. A thin, conformal coating of PPTFE (etch rate of 0.3 nm/h at 22°C) was found to protect an underlying, cast film of a reactive polymer, cis‐1,4‐polybutadiene (etch rate of 0.13 mg/cm2 h ≡ 1300 nm/h at 22°C), against O(3P) attack for the time required to fully etch away the PPTFE coating. From ESCA analysis, PTFE exhibited only minor surface oxidation (uptake of 0.5 atom % O) upon etching, its F/C ratio decreasing slightly from 2.00 to 1.97; PPTFE exhibited considerable surface oxidation (uptake of 5.9 atom % O) and a decrease in F/C ratio from 1.30 to 1.23; and SPTFE exhibited a surface oxidation (uptake of 2.2 atom % O) intermediate between those of PTFE and PPTFE, with a decrease in F/C ratio from 1.73 to 1.67. The O(3P)‐induced etching of PTFE had an activation energy of 3.8 Kcal/mol, but no activation energy value was obtained for PPTFE which gave a nonlinear Arrhenius plot apparently because of thermally induced thinning above 50°C.
Simultaneous sorption and diffusion of a 4‐aminoazobenzene derivative and its conjugate acid in cellulose membrane carrying sulfonic acid groups
Authors: Shibusawa Takao , Weber Ruth , Rys Paul 
Published: April 2003

AbstractAn azo dye, 2‐methyl‐N,N‐bis(2‐hydroxyethyl)‐4‐aminoazobenzene (nonionic dye) and its conjugate acid (cationic dye) are simultaneously adsorbed by the cellulose membranes carrying sulfonic acid groups from a slightly acidic aqueous solution. Sorption equilibria of the nonionic and the cationic dye are described in terms of the Henry's partition and the ionic exchange mechanism, respectively, in the latter case, the ion exchange constants obtained for the membrane with sulfonic acid group content (SAG) = 261 meq/kg at 30°C are K = 1.43 × 10−5 and K = 0.542, respectively, where Na, H, and DH refer to sodium, hydrogen, and cationic dye ions. The diffusion coefficients of the nonionic dye (DN) and the cationic dye (DC) in the membranes were estimated from the permeation data of the dyes through the membrane. Both DN and DC decrease with increasing SAG. The ratio DN/DC ranged in 2.2–10, the ratio increases with the SAG.
A study of inverse relaxation in some textile fibers
Authors: Nachane R. P. , Hussain G. F. S. , Patel G. S. , Iyer K. R. Krishna 
Published: April 2003

AbstractThis article discusses the phenomenon of inverse relaxation in some textile fibers, namely cotton, ramie, wool, polyester, and viscose. If anextended viscoelastic specimen is allowed to recover a part of the deformation given to it, such that its tension has not become zero, the stress in it tends to increase. This phenomenon is termed as “inverse relaxation.” This property is measured in terms of an index referred to as the inverse relaxation index. The values of this index at various extension and retraction levels for the above materials are presented and discussed in this article.
Decrystallization and acetylation and benzoylation of cotton fibers
Authors: Subramaniam V. , Vasugi N. 
Published: April 2003

AbstractThe general effects of chemical modification such as acetylation and benzoylation on cotton yarns and fabrics are described and it is demonstrated that the physical properties of yarns and fabrics in terms of their elongation, moisture regain, friction, abrasion resistance, and recovery are enhanced significantly. Thermal analysis data show that benzoylated sample is the most stable product.
Melting behavior of cis‐polybutadiene crystallized under stress
Authors: De Candia F. , Romano G. 
Published: April 2003

AbstractSamples of crosslinked cis‐polybutadiene were crystallized at different temperature and drawing degree. The melting behavior of the crystallized samples was analyzed detecting the retractive stress as a function of temperature. The experimental melting data were extrapolated to the equilibrium conditions to obtain the thermodynamic melting temperature as a function of the drawing degree. The extrapolated data were analyzed with different theoretical approaches. Results agree with a model in which chain‐folding and extended‐chain crystallization can coexist, depending on crystallization temperature and drawing degree.
Isocyanate–epoxy reactions in bulk and solution
Authors: Senger J. S. , Yilgor I. , McGrath J. E. , Patsiga R. A. 
Published: April 2003

AbstractThe reaction between diisocyanates and diepoxides can produce polyoxazolidones. However, the reaction may be accompanied by concurrent cyclization of isocyanate to produce trimeric isocyanurate. Studies were performed with pure phenyl isocyanate or diphenylmethane‐4,4′‐diisocyanate (MDI) and the diglycidyl ether of bisphenol‐A (DGEBA). Reactions were followed by FT‐IR and differential scanning calorimetry in order to determine relative rates of conversion to polyoxazolidone and isocyanurate. Various catalysts were utilized, with the most effective being 2‐ethyl‐4‐methylimidazole (EMI). Bulk reactions between MDI and DGEBA at 150°C resulted in considerable amounts of trimerization, thus giving crosslinked polymers. Solution reactions at 180–185°C in dry N‐methylpyrrolidone using 0.1% EMI gave soluble and moldable polyoxazolidones.
Compositional analysis and infrared spectra of styrene–methyl methacrylate random copolymers
Authors: Mori Sadao 
Published: April 2003

AbstractCompositional analysis of styrene–methyl methacrylate random copolymers by UV spectrophotometry at 260 nm, proton‐NMR, and IR at 1730 cm−1 have been accomplished and agreement between these three independent methods was excellent. IR spectra of the copolymers in the region of 1100 and 1300 cm−1 are mainly characteristic absorption bands for the methyl methacrylate (MMA) component, but not the same for those of MMA homopolymer, that is, the IR spectra of the copolymers were not additive with those of polystyrene and PMMA. Information about the sequence distribution of copolymers of the same composition can be obtained by comparing the wavenumbers and absorption coefficients of the IR spectra in the region of 1100–1300 cm−1
Fourier transform infrared analysis of plasma‐polymerized hexamethyldisiloxane
Authors: Krishnamurthy V. , Kamel Ihab L. , Wei Yen 
Published: April 2003

AbstractThe plasma‐induced polymerization of hexamethyldisiloxane onto solid surfaces is studied by FTIR. An inductively coupled RF reactor was used to produce the thin polymer coatings. Analysis of the plasma polymer indicates a long chain polysiloxane structure resulting from the removal of some methyl groups from the monomer structure. Increasing the plasma power level from 30 to 100 W increased the chain length in the resultant polymer as indicated by the widening and splitting of the Si–O stretching absorptions. Thermal aging of the vapor phase polymer at 120°C for 1 h in vacuum and at 410°C for 30 min in a nitrogen atmosphere revealed the removal of some methyl groups from the polymer structure with temperature. TGA runs on the vapor phase polymer at 20°C/min in air showed the polymer retaining almost 65% of its weight at 1000°C. The residue remaining after the TGA run had very little organic content and may represent a glass type silicate network. Wettability values determined on coated glass slides revealed the hydrophobicity of the coatings with water contact angle values > 100°. SEM micrographs showed uniform and featureless coating on glass fibers which was etched by boiling water and was attributed to the loss of vapor phase polymer on the surface.
Thermal properties of drawn polytetrafluoroethylene
Authors: Grebowicz J. , Pan R. , Wunderlich B. 
Published: April 2003

AbstractPolytetrafluoroethylene as polymerized (virgin) was drawn, sintered, and annealed. By thermal analysis the changes in crystal type and crystallinity and melting kinetics was analyzed. It is shown that this analysis permits control and optimization of the various processes. In addition, a new, high melting polytetrafluoroethylene (654 K) is described. It is assumed to be metastable due to strain in the surrounding amorphous fraction.
Polymerization of methane
Authors: Sharma Ashok K. , Yasuda H. 
Published: April 2003

AbstractPlasma polymerization of methane in a magnetically enhanced capacitively coupled bell jar reactor operating at a frequency of 10 kHz is reported. Dependence of polymer deposition rate on monomer feed rate (F), composite power parameter (W/FM), electrode temperature, and electrode cleanliness have been examined. Such functional properties as wettability, adhesion, and thermal stability of the polymer are found to depend on the composite power parameter (W/FM) of the plasma. The permeability studies indicate highly crosslinked nature of the polymer. ESCA studies reveal codeposition of electrode material with the polymer under high W/FM conditions, potential applications of plasma polymer of methane are suggested.
Effect of polypropylene morphology on thermal cis‐trans isomerization and photofading of some azo dyes: A kinetic study
Authors: Beltrame Pier Luigi , Paglia Ernestina Dubini , Marcandalli Bruno , Seves Alberto 
Published: April 2003

AbstractFive polypropylene films were prepared having different crystallinity and morphology, the latter having been modified by stretching. They were colored with azo dyes XC6H4NNC6H4N(C2H5)2 (where XH, OCH3, CN, and NO2). The kinetics of the thermal cis‐trans isomerization of these dyes has been studied in the range 21–41°C, much above the glass transition temperature of the polymer. The isomerization process was found to be strictly first‐order; the kinetic parameter values have been correlated with the free volume extent in the amorphous regions of the matrix. Lightfastness of the dyes in the polymer matrices has been also investigated: It appeared to be more important for the unoriented samples with respect to the stretched ones and substantially independent on the crystalinity degree.
Torsional braid analysis and gelation in thermoset resins
Authors: Stutz H. , Mertes J. 
Published: April 2003

AbstractThe origin of the two damping maxima observed during curing of thermoset resins by torsional braid analysis has been studied using a standard epoxy resin. The first peak is not caused by gelation of the resin, but is due to certain flow phenomena prior to gelation. This first peak always occurs at approximately the same viscosity and is observed only when a fiber braid is used as support. It is therefore, in principle, not possible to detect gelation by torsional braid analysis. The second (vitrification) peak is correct, but it is indicated somewhat too early.
Internal stress in epoxide resin networks containing biphenyl structure
Authors: Ochi Mitsukazu , Yamashita Kiichi , Yoshizumi Makoto , Shimbo Masaki 
Published: April 2003

AbstractBisphenol‐A type and biphenyl type epoxide resins were cured with two types of aromatic diamines which have or do not have the carbon bridge between aromatic rings. Internal stress of these cured resins decreased with the introduction of a biphenyl structure into the networks. This reduction of the internal stress is attributed to the decrease of the elastic modulus in the glassy region caused by the low mobility of the biphenyl segment. On the other hand, the glass transition temperature increased with increasing the concentration of the biphenyl unit in the networks. These results revealed that the consistency of the decrease of the internal stress with the improvement of the heat resistance of the cured systems is possible by introducing the biphenyl structure to the epoxide resin networks.
Kinetics of radiation‐induced graft copolymerization of 2‐hydroxyethyl methacrylate onto polyethylene membranes
Authors: Yue‐E Fang , Tianyi Shi , Wenfeng Wang , Fang Shi 
Published: April 2003

AbstractThe kinetics of radiation‐induced graft copolymerization of 2‐hydroxyethyl methacrylate onto polyethylene membranes in ethanol has been studied with radiation sources of cobalt‐60. The influences of concentration of monomer, dose rate, and temperature on grafting rate were investigated. The results show the following functional relationship equations: dG0/dt ∝ [M]0 and dG0dt ∝ Ḋ1/2. The apparent activation energy and the collision frequency factor of the grafting copolymerization are 8.0 kcal/mol and 1.505 × 107 G% h−1/2 Mrad−1/2 mol−1 L, respectively. The work established that the relationship of the grafting rate constant k with the temperature relational expression at arbitrary temperature: in k = 16.5269 − 4026(1/T).
The xanthate method of grafting. XII. Effect of operating conditions on the grafting of vinyl monomers onto wood pulp
Authors: Daneault Claude , Kokta Bohuslav V. , Maldas Debesh 
Published: April 2003

AbstractThe present paper examines the influence of various reaction parameters (e.g., pH, type, and concentration of peroxide, reaction time, oxygen as well as reaction medium) on the graft copolymerization of methacrylic acid, butyl methacrylate, epoxypropyl acrylate, and epoxypropyl methacrylate onto chemithermomechanical pulps, initiated by the xanthate method. The optimum concentration of H2O2 changes with the monomer used. Among the peroxides investigated, H2O2 offered the best performance. Oxygen and organic solvents, e.g., acetone and vegetable oil, inhabited grafting reaction. In addition, epoxy monomers showed better results compared to other monomers; this may be due to the participation of epoxy groups in the polymerization reaction
Sequential vapor sorption of additional penetrants in preswollen polymers
Authors: Bontoux Laurent G. , Soane David S. 
Published: April 2003

AbstractUptake and removal of a second penetrant in polymer samples preexposed to another vapor dictate many industrially important processes. Both the kinetics and equilibrium sorption can be strongly affected by the presence of the first permeant in the polymeric matrices. A novel experimental setup was constructed to study penetrant uptake in sequence. Sorption of the second vapor took place while the partial vapor pressure of the first vapor was maintained, so that diffusion into the preswollen polymer approximated transport in a pseudobinary system. Polybutylene was chosen in this work to illustrate the capability of this versatile experimental system. Both the rate of diffusion and equilibrium sorption of the second vapor were found to depend on the prevailing composition of the preswollen polymer for all penetrant pairs studied.
The effect of the soft segment of polyurethane on copolymer‐type polyacetal/polyurethane blends
Authors: Chiang Wen‐Yen , Huang Chi‐Yuan 
Published: April 2003

AbstractMechanical blends of copolymer‐type polyacetal (POM) with ester‐based and ether‐based polyurethane (PU) are immiscible over the 0–50% PU compositional range. The PU elastomer was added to the rigid POM matrix to increase its toughness. The mechanical, physical, thermal, dielectric, and dynamic mechanical properties and morphology of POM/PU blends were investigated. The notched Izod‐impact strength of blends reaches a maximum at 10 wt % PU. The tensile strength, Young's modulus, volume resistivity, crystallinity, and density decrease with increasing concentration of PU. The elongation of blends reaches a maximum at 20 wt % PU. The dielectric constant and dissipation factor increase with increasing PU content. From dynamic mechanical measurements, as the elastomer content increases, the height of the damping peak also increases, but there is no transition temperature shift. SEM shows that the blends exhibit a continuous morphology with domain size varying from 1 to 10 μm for PU. However, at a concentration of 50 wt % PU, the dispersed PU particles tend to aggregate. Characterization of morphology by a metallurgical microscope has shown that the crystalline materials in the pure POM and the blends exist in a spherulitic superstructure.
The selective sorption of D,L‐amino acids by chemically modified chitosan gels and its application to liquid chromatography
Authors: Seo Toshihiro , Gan Yoke Ai , Kanbara Takaki , Iijima Toshiro 
Published: April 2003

AbstractThe sorption of D,L‐amino acids, DNP‐L‐amino acids and dipeptides by N‐octanoyl‐ and N‐benzoyl‐chitosan gels was investigated under various conditions. The results indicate that optical resolution of D,L‐amino acids by liquid column chromatography has been achieved, using the chemically modified chitosan gels as a stationary phase.
Fourier transform infrared and high‐resolution solid‐state carbon‐13 NMR spectroscopic characterization of cured polystyrylpyridine resins
Authors: Menif R. , Jasse B. , Laupretre F. , Bloch B. 
Published: April 2003

AbstractInteresting crosslinked materials possessing good mechanical and thermal properties are obtained by condensation of 2,4,6‐trimethylpyridine (collidine) with terephthalic aldehyde in the presence of an acidic catalyst. Fourier transform infrared spectroscopy has been used to follow the kinetics of the chemical reactions involved in the formation of the tridimensional network using aldehyde and ethylene absorption bands. The first steps of the reaction consist in the addition of aldehyde groups on the methyl groups of collidine followed by a dehydration reaction which leads to the formation of ethylenic functions. Crosslinking is obtained by an addition reaction of the methyl groups of collidine on the double bonds created in the first processes. These reactions are strongly dependent on the reaction temperature. Cured resins prepared with different acidic catalysts have been studied by carbon‐13 NMR. p‐Toluene sulfonic acid leads to residual aldehyde groups in the cured resins whereas no residual aldehyde groups are observed after a relatively short curing time when sulfuric acid is used as the catalyst. The networks created in the two cases are not equivalent and present different mechanical properties.
Crosslinking structure of keratin. I. Determination of the number of crosslinks in hair and wool keratins from mechanical properties of the swollen fiber
Authors: Arai Kozo , Sasaki Naokazu , Naito Sachio , Takahashi Toshie 
Published: April 2003

AbstractHair and wool keratin fibers which had been treated with an 11 M LiBr solution containing N‐ethyl maleimide showed typical rubberlike elasticity in a solution composed of equal volume of 8 M LiBr and diethylene glycol mono‐n‐butyl ether. Stress–strain curves and equilibrium force–temperature relations were measured for swollen hair and wool fibers. The non‐Gaussian effects on deformation and the energy component in retractive forces were analyzed. On the basis of rubber elasticity theory, a method for estimation of the number of mechanically effective crosslinks in keratin fibers was proposed. A linear relationship between the crosslink density and the disulfide content was obtained from the data for a variety of keratin fibers (i.e., two different human hairs, horse hair, and 17 different wools). From the results of thermodynamical and non‐Gaussian treatments for swollen keratin, it was suggested that the swollen fiber consists of a two‐phase structure: a mechanically stable phase of higher crosslinked domains and rubbery phase with lower crosslink density. It was further found that considerable amounts of nondisulfide covalent crosslinks are present in wool and hair keratins.
The compatibility of a polymer catalyst–substrate–solvent and its reaction rate. I
Authors: Jiadong Hua , Ruofeng Wu , Lu Liu , Peirong Yu 
Published: April 2003

AbstractAn attempt was made which expressed in a compatibility rule not only the polymer effect but the solvent effect in a given polymeric catalyst system. Here the compatibility refers to interaction energy effects among the polymer backbone, substrate, and solvent, which can be measured by chesive energy density or the solubility parameter. A polymer catalyst adopted here is poly(diethylaminoethyl acrylate)–palladium ion complex. The experiments showed that the activity of the polymer catalyst had a bell‐shaped solubility parameter profile and an optimum solubility parameter value for some substrates, and had an inverse bell‐shaped solubility parameter profile and a minimum solubility parameter value for some solvents. Perhaps these results might be utilized to design a polymer catalyst having high activity for a given substrate.
Internal mixer studies of poly(vinyl chloride)/epoxidized natural rubber blends
Authors: Nasir Zainal A. , Ratnam Chantera T. 
Published: April 2003

AbstractBlends of polyvinyl chloride/epoxidized natural rubber (PVC/ENR) blends were studied. Their rheological properties were studied with a Brabrender Plasticorder. It was found that the rheological properties of any PVC/ENR blends are governed by their blending conditions. To ensure homogenous PVC/ENR blends, adequate and suitable blending conditions must be utilized. PVC thermoplastics phases enhances rigidity while ENR rubbery phases imparts flexibility and processability to the blends. With premixing, Ba/Cd/Zn‐based PVC stabilizer is effective in stabilizing the PVC/ENR blends. Their properties are further enhanced by the addition of curatives.