bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties and structure of never‐dried cotton fibers. III. Cotton fibers from bolls in early stages of growth
Authors: Tsuji Waichiro , Nakao Tokie , Hirai Asako , Horii Fumitaka 
Published: April 2003

AbstractLike other kinds of cotton fibers already studied, American cotton fibers taken from cotton bolls immediately before and after opening show high angles of torsional rotation during ambient humidity changes. Cotton fibers taken from cotton bolls at 19 and 24 days postanthesis show remarkably higher angles of rotation and much lower dry and wet tensile strengths than the fibers taken from cotton bolls immediately before and after opening. The wet tensile strength of cotton fibers at 24 days postanthesis is higher than the dry strength like the fibers taken from bolls immediately before and after opening, but fibers at 19 days postanthesis show almost the same tensile strength in the never‐dried, dried, and rewetted states. CP/MAS 13C NMR spectroscopy reveals that the never‐dried cotton fibers at 19 days or longer postanthesis have high crystallinities. It seems that the degree of crystallinity is somewhat decreased in the dry state and restored by rewetting. The crystallinity increases with the age of growth.
Facile method for the preparation of tri‐O‐(alkyl)cellulose
Authors: Kondo Tetsuo , Gray Derek G. 
Published: April 2003

AbstractA simple way to prepare tri‐O‐(alkyl)cellulose from cellulose acetate (CA) in dimethylsulfoxide (DMSO) using the appropriate alkyl iodide and NaOH has been developed. In this procedure, the addition of a small amount of water to the DMSO solution improved the efficiency of etherification. The substitution pattern of (methyl)cellulose (MC) was investigated to determine the effect of added water on the relative reactivities of the glucose ring substituents. This etherification method can be applied to alkylate other polymers with acetate‐functional groups that are soluble in DMSO.
Facile measurement of phenolic end‐groups in bisphenol‐a polycarbonate using GPC‐UV analysis
Authors: Mork C. O. , Priddy D. B. 
Published: April 2003

AbstractTo maximize polycarbonate (PC) stability, it is extremely important that the polycarbonate manufacturing process be operated in such a way as to minimize uncapped polymer chain‐ends. Insurance of complete end‐capping during manufacture would require constant process monitoring using a fast and accurate phenolic end‐group analysis technique for samples typically having > 5% uncapped chain‐ends. Published end‐group analysis techniques are inaccurate if the polymer samples are contaminated with monomer or other small phenolic molecules. Accuracy can be improved by purifying the polymer before analysis, but this procedure is sometimes tedious. This article describes the development of a facile gel permeation chromatography‐ultraviolet (GPC–UV) technique for quantitative determination of low levels of phenolic uncapped chain‐ends in PC. This technique improves accuracy because monomers and other small molecule impurities are separated and excluded from the PC during the analysis.
Role of surfactant in composite latex particle morphology
Authors: Chen Y. C. , Dimonie Victoria , El‐Aasser Mohamed S. 
Published: April 2003

AbstractComposite particles were prepared by seeded emulsion polymerization at 70°C using K2S2O8 as initiator and two different nonionic surfactants. Monodisperse polystyrene latex particles were used as seed and methyl methacrylate was used as second‐stage monomer. When the surfactant, polyethylene oxide–propylene oxide (Pluronic F‐108), was used, the final particle morphology showed that the PMMA (core) was partially covered by polystyrene. However, when nonyphenol polyethylene oxide (Igepal Co‐990) was used as surfactant, one observed a reversed type of encapsulation (i.e., PS core is partially engulfed by PMMA). The interfacial tensions of the polymer phase against water containing the appropriate surfactant were measured by the drop‐volume method and used in a mathematical model based on thermodynamic analysis to predict the equilibrium particle morphology. The observed particle morphologies were found to differ from the predicted morphologies at low conversion of the second‐stage monomer but agreed with it at higher conversion.
Synthesis and characterization of phenolic and amino resins based on α, β‐unsaturated aldehydes
Authors: Žigon Majda , Šebenik Anton , Osredkar UČi 
Published: April 2003

AbstractPhenolic and amino resins on the basis of α,β‐unsaturated aldehydes were synthesized in bulk or solution. Catalysts were HCl, H3PO4, or formic acid, and in some cases NaOH. The course of the reactions was followed by GPC and NMR while the structure of the reaction products was determined by one‐ and two‐dimensional NMR. The course of the reactions is influenced by experimental conditions: the type of monomers, their molar ratio, the type and quantity of the catalyst, the reaction time and temperature, and the reaction medium. At the beginning of the reaction the addition of a nucleophile to an aldehyde takes place through parallel 1,2‐addition to and 1,4‐addition to group. Oligomers with OH, , and CHO functional groups are able to add new monomer units or to react mutually to form higher molecular weight addition and condensation products. The overall rate constants for the beginning of the reactions were between 10−3 L/mol s for the high reactive mixtures and 10−7 L/mol s for the less reactive mixtures. The resins were cured by heating at temperatures above 135°C with the addition of hexamethylenetetramine.
Citric acid–diethylenetriamine salts as latent curing agents for epoxy resins
Authors: Galego N. , Vazquez A. , Riccardi C. C. , Williams R. J. J. 
Published: April 2003

AbstractCitric acid (CA)–diethylenetriamine (DETA) salts (CADETA) were prepared by using a 4.5 : 1 molar ratio of DETA–CA and removing the DETA excess. The structure of CADETA was analyzed by 13C‐NMR, IR, and DSC associated with weight loss. One‐step formulations consisted on dispersions of CADETA (variable amounts) in an epoxy resin based on diglycidylether of bisphenol A (DGEBA, EEW = 185.5 g/eq). The cure was followed in the pressure cell of a DSC (N2 at 2.5 MPa), to avoid volatilization of DETA in the temperature range where decomposition of CADETA and beginning of reaction took place (T > 175°C). A very small heat of reaction was observed, (−ΔH) ∼ 10 kJ/eq, resulting from the simultaneous endothermic salt decomposition and exothermic network formation. A stoichiometric formulation showed a Tg = 180°C, i.e., some 60°C higher than the one observed for the usual DGEBA/DETA system.
Polymer swelling, 13: Correlation of flory–huggins interaction parameter, χ, with molecular structure in polystyrene–liquid systems
Authors: Errede L. A. 
Published: April 2003

AbstractIt is shown that the Flory–Huggins interaction parameters (χ), for polystyrene–liquid systems, reported by others, vary linearly with the readily and precisely determinable relative swelling power (C) of the selfsame liquid, determined in this laboratory using poly(styrene‐co‐divinylbenzene) as the sorbent polymer. This simple gravimetric method appears to be the most suitable for the determination of χ values of polystyrene–liquid systems over the full range of polymer volume fractions. Accordingly, the C values already determined by this method were used to calculate numerous χ values for polystyrene–liquid systems not yet reported in the literature. The data obtained thereby show that χ reflects sensitively the molecular structure of the liquid.
A new equation for estimating [η] from single‐viscosity measurement in dilute solution
Authors: Raju K. V. S. N. , Yaseen M. 
Published: April 2003

AbstractThe use of a linear two‐parameter approximation for determining limiting viscosity number, [η], of a polymer in the state of infinite dilution requires considerable amount of time, effort, and materials. Several workers who attempted to estimate [η] directly from single‐viscosity measurement also proposed equations for this purpose. Such equations are tested and found to have good applicability to practical data within specified limits of concentration or specific viscosity. A new equation has been derived and tested for polymers of high and low molecular weights in various solvents and at different temperatures. The introduction of a constant in this equation makes it applicable over a wider range of specific viscosity. It is found to serve better for determination of [η] from a single‐viscosity measurement.
Low dose γ‐irradiation of some fluoropolymers: Effect of polymer chemical structure
Authors: Rosenberg Y. , Siegmann A. , Narkis M. , Shkolnik S. 
Published: April 2003

AbstractThe effect of low dose (1–20 Mrad) γ‐irradiation on five fluoropolymers (PVF, PVDF, ETFE, FEP, PFA), differing in fluorine content and chain structure, was studied. The radiation effect, reflected by changes in thermal and mechanical properties, as well as NaOH etched surface morphology, was investigated. The main chain structure was found to predominate the irradiated polymers' behavior. The tensile strength of PVF and its resistance to etching increased with radiation dose, while its degree of crystallinity and melting temperature decreased. These changes were correlated with network formation by irradiation and by the incorporation of crosslinked segments into the crystalline phase during recrystallization. Solvent extraction of PVDF (no solvents were found for the other fluoropolymers) revealed increased gel formation with increasing dose. The degree of crystallinity and the tensile strength dependence on radiation dose for PVDF and ETFE reflected the competition between crosslinking and chain scission events. FEP and PFA undergo predominantly chain scission accompanied by reduction of their mechanical properties. PFA even exhibited an increase in both its melting temperature and degree of crystallinity, stemming from a massive degradation process forming shorter chains. Chemical mechanisms are discussed in an attempt to correlate the irradiation effects with the polymers' chain structure.
Catalytic grafting: A new technique for polymer/fiber composites. II. Plasma treated UHMPE fibers/polyethylene composites
Authors: Wang Qi , Ait‐Kadi Abdellatif , Kaliaguine Serge 
Published: April 2003

AbstractIn this paper, the catalytic grafting technique for preparation of polymer/fiber composites is extended to plasma treated ultra‐high modulus polyethylene (UHMPE) fiber/high density polyethylene (HDPE) system. The OH groups introduced on the UHMPE fiber surface by oxygen plasma treatment were used to chemically anchor Ziegler‐Natta catalyst which then was followed by ethylene polymerization on the fiber surface. The morphology and interfacial behavior, as well as the mechanical properties, of the HDPE composites reinforced by catalytic grafted or ungrafted UHMPE fibers were investigated by SEM, DSC, polarized light optical microscopy, and tensile testing. The experimental results show that the polyethylene grafted on the fibers acted as a transition layer between the reinforcing UHMPE fibers and a commercial HDPE matrix. The interfacial adhesion was also significantly improved. Compared with the composite reinforced by ungrafted UHMPE fibers, the composite reinforced by catalytic grafted UHMPE fibers exhibits much better mechanical properties.
Dynamic mechanical analysis of sulfonated polyurethane ionomers
Authors: Ding Jianfu , Xue Gi , Yang Changzheng , Chen Ronshi 
Published: April 2003

AbstractDynamic mechanical analysis, using a flat‐spring to support the sample, was conducted to study the properties of polyurethane ionomers prepared from poly(epoxy chloropropane) as polyol. The effects of the soft segment length and ionization level on the properties were studied. For the unionized polyurethane, the soft and hard segments had good compatibility and little phase separation was found due to the high polarity of the polyol. For the shorter hard segment ionomers, as the ionization level increased, the matrix Tg rose due to the increase in the compatibility of hard and soft segments. For the longer ionized hard segment ionomers, the aggregating tendency of ion pairs enhanced phase separation. Quenching or annealing the samples showed that clusters existing in bulk materials did not dissociate below the degradation temperature and multiplets can dissociate or transform to clusters below 150°C.
Phase behavior and mechanical properties of injection molded poly(ethylene terephthalate)/polyarylate blends
Authors: Martínez J. M. , Eguiazábal J. I. , Nazábal J. 
Published: April 2003

AbstractDirectly injection molded blends, composed of poly(ethylene terephthalate) and a polyarylate of bisphenol A, and isophthalic/terephthalic acids have been studied. Both their phase behavior and their mechanical properties after this blending method have been determined. After injection molding, the poly(ethylene terephthalate)/polyarylate blends show a single glass transition by differential scanning calorimetry, although the transition peaks of the blends widen when observed by dynamic mechanical analysis. The calorimetric results show a hindered crystallization of poly(ethylene terephthalate), due to the presence of polyarylate and the occurrence of interchange reactions. The mechanical behavior observed shows an improvement in the small‐strain properties of the blends with respect to those of the pure components. The break and impact properties of the blends show negative deviations with respect to linearity. These deviations are less important when high polyarylate content exists in the blends.
The thermo–oxidative degradation of acrylonitrile–butadiene–styrene copolymers during processing as studied by chemiluminescence
Authors: Memetea Tatiana , Vuluga Zina , Hagiopol Cornel 
Published: April 2003

AbstractThe glow curve obtained upon processing acrylonitrile–butadiene–styrene copolymers (ABS), through various machines, reaches a peak at 180°C. The proper assignment of that peak has required the study of the chemiluminescence (CL) shown by related polymers such as: polybutadiene (PB), styrene–acrylonitrile copolymer (SAN), and polyacrylonitrile (PAN). Three hydroperoxide types associated with the structural units, that is, 1, 2, and cis‐ and trans‐1,4, exhibiting CL peaks at 180, 240, and 340°C, respectively, have been identified in the PB sample. The activation energy (Ea), recorded for the hydroperoxides thermal decomposition, was 15.0 ± 1.0, 17.85 ± 0.9, 20.7 ± 0.8 kcal/mol. PAN shows a CL peak at 180°C. Its occurance is related to the color developed during the thermal treatment. That PAN peak has been attributed to the hydroperoxides generated on the acrylonitrile units neighboring the azomethinic structures. The corresponding Ea is 23.3 ± 1.0 kcal/mol. The same peak (having an identical position and Ea) has been identified with processed ABS and SAN copolymers. As is evident by CL studies, the processing induced oxidation mainly occurs within the SAN phase of the ABS copolymers, though it was also noted within 1,2 units of the PB phase.
Intrinsic viscosity and molecular weight measurement of nylon 66 polymers
Authors: Samanta S. R. 
Published: April 2003

AbstractIntrinsic viscosity of several nylon 66 polymers in the molecular weight range 25,000–105,000 was measured in hexafluoroisopropanol (HFIP). The experimentally measured viscosity was compared with the data obtained by least‐squares fit of the classical equations of Huggins and Kraemer. The utility of the single‐point viscosity measurement is also discussed and compared with the measured data. The apparent hydrodynamic parameters obtained from the Huggins equation indicate the applicability of HFIP for studying polyamide polymers. The molecular weight of these polymers was also determined by the gel permeation and low‐angle laser light scattering technique (GPC–LALLS). The molecular weight data combined with the viscosity data provide the Mark–Houwink parameters. The agreement between these parameters and the same parameters obtained in tetrafluoropropanol (TFP) is excellent.
Thermal stability of in situ filled siloxane elastomers
Authors: Sohoni G. B. , Mark J. E. 
Published: April 2003

AbstractPoly(dimethylsiloxane) elastomers that had been filled with in situ precipitated silica were studied by thermogravimetric analysis, under nitrogen and in air. Both types of measurements indicated that the filler raises the temperature of thermooxidative degradation of the polymer, possibly by inactivating the terminal OH groups on the chains. Commercial fume silica was found to cause more severe degradation problems than did the in situ precipitated silica. In all cases, the degradation was more pronounced in air than in the inert atmosphere provided by nitrogen. © 1992 John Wiley & Sons, Inc.
A new technique for preparing monodisperse polymer particles
Authors: Hou Wei‐Hsin , Lloyd Thomas B. 
Published: April 2003

AbstractA procedure is described for preparing fairly uniform spheres of three different nylon polymers by phase separation. The mean diameter and polydisperse index were 5 μm and 1.056 for Griltex nylon, 5.7 μm and 1.046 for nylon 6/6, and 12.9 μm and 1.016 for nylon 6. The phase separation is done by taking a 1 wt % solution in a theta solvent above the theta temperature and cooling it rapidly. The spheres of the three nylons have various degrees of roughness. Formation of highly uniform particles during phase separation is discussed in a preliminary way. © 1992 John Wiley & Sons, Inc.
Morphology of polymer wear debris resulting from different contact conditions
Authors: Hosseini S. M. , Stolarski T. A. 
Published: April 2003

AbstractAn investigation into the wear process of five polymers tested under different contact conditions is presented. Polymer pin on metal plate and metal pin on polymer plate configurations were used. The metal pin on polymer plate configuration gave significantly lower wear rates compared to that observed for the polymer pin on metal plate configuration. The results are discussed in terms of morphology of wear debris generated.
Structure and physical properties of seed proteins. I. Glass transition and crystallization of zein protein from corn
Authors: Magoshi Jun , Nakamura Shigeo , Murakami Ken‐Ichi 
Published: April 2003

AbstractThermal behavior of a seed protein, zein from corn, was studied by differential scanning calorimetry (DSC), thermogravimetry (TG), thermal expansion, X‐ray diffraction, and infrared spectroscopy. Zein film cast from aqueous ethanol is amorphous in the randomcoil conformation. Water in the specimen is lost by evaporation at about 100°C. The glass transition is observed at 165°C. The amorphous zein crystallize to β‐crystals at about 210°C accompanied by the random‐coil → β‐form conformational transition. The thermal degradation of zein occurs at about 320°C. Steam treatment of zein film results in the conformational change to the α‐ and β‐forms, simultaneously, irrespective of treating temperature. © 1992 John Wiley & Sons, Inc.
Thermal aging of plasticized PVC. I. Weight loss kinetics in the PVC—didecylphtalate system
Authors: Audouin L. , Dalle B. , Metzger G. , Verdu J. 
Published: April 2003

AbstractWeight‐loss kinetics were studied for 10 industrial extruded samples of poly(vinyl chloride) (PVC) plasticized by 20–30% by weight of didecylphtalate at 85, 95, 105, 110, and 120deg;C. For the most unstable samples, which contained a light coplasticizer, the weight‐loss rate obeyed Fick's law. In the other cases, it was constant in the early period of exposure. The apparent Arrhenius parameters (i.e., preexponential factor and activation energy) were intercorrelated and varied strongly from one sample to another. This was explained by the existence of two distinct kinetic regimes corresponding, respectively, to diffusion or evaporation, the whole process being controlled by the slowest step, and a transition between both regimes occurring in the temperature range of exposure. In the proposed model, small changes of the preexponential factor of diffusion from one sample to another are sufficient to take into account the observed behavior.
Poly(vinyl chloride) composition. II. Study of the flammability and smoke‐evolution of unplasticized poly(vinyl chloride) and fire‐retardant additives
Authors: Stoeva S. , Karaivanova M. , Benev D. 
Published: April 2003

AbstractThe influence of natural, activated, and modified microzeolite with the general formula Me2/m · Al2O3 · nSiO2 · pH2O (where Me = Fe3+, Ca2+, Mg2+, Zn2+, K+, Na+) and an organic additive, such as ammonium sulfamate combined with ammonium sulfate on smoke formation and flammability of suspension poly(vinyl chloride) has been studied in the present work. Microzeolite in native (i.e., natural), activated, and modified forms has been found to possess both fire‐retardant and smoke‐suppressant effects in solid poly(vinyl chloride) compositions. Such effects have been best revealed by modified microzeolite containing 3,5–4% zinc. On the other hand, the ammonium sulfamate combined with ammonium sulfate is believed to act as a strong smoke‐suppressant additive. Thermogravimetric examinations and limited oxygen index measurements show that microzeolite acts as a fireresistant and smoke‐suppressant additive predominantly in the condensed phase. The ammonium sulfamate in combination with ammonium sulfate gives evidence of the same effects, mostly in the gaseous phase.
Physical and mechanical behavior of tetraglycidyl diaminodiphenyl methane (TGDDM)/m‐phenylene diamine (m‐PDA) epoxy systems
Authors: Imaz J. J. , Jurado M. J. , Corcuera M. A. , Mondragon I. 
Published: April 2003

AbstractThe rheological behavior of a tetraglycidyl diaminodiphenyl methane with a tetrafunctional aromatic diamine has been studied in terms of the influence of curing agent content and temperature. In this work, critical times corresponding to gelation are used as a measure of activation energy. The dynamic mechanical behavior has been used to analyze the curing extent of these epoxy systems with different amine contents before and after thermal posttreatment. The β‐relaxation peak temperature is found to increase with the curing agent content and also after thermal posttreatment. This has been related to the rise of crosslinking extent. Dependence of flexural mechanical properties on curing agent content and the postcure process has also been determined.
Application of compressed carbon dioxide in the incorporation of additives into polymers
Authors: Berens Alan R. , Huvard Gary S. , Korsmeyer Richard W. , Kunig F. W. 
Published: April 2003

AbstractIt has been found that carbon dioxide remarkably accelerates the absorption of many low molecular weight additives into a number of glassy polymers. This effect is due to the high diffusivity, solubility, and plasticizing action of compressed CO2 in polymers. The transport of CO2 and the effects of CO2 pressure on the transport of other low molecular weight compounds in polymers have been studied by a simple gravimetric method: Polymer film samples were contacted in a pressure vessel with compressed CO2, or with CO2 plus various organic liquids or solids, and the sample weight was followed with a fast‐response electronic balance during subsequent desorption at atmospheric pressure. Upon release of the pressure, absorbed CO2 rapidly diffuses from the polymer, while the other compounds desorb much more slowly. The amount of additive absorbed can be determined from the plateau weight of the sample after most of the CO2 has escaped. Extensive kinetic and equilibrium data are reported for the model system poly(vinyl chloride)/dimethyl phthalate/CO2, and a number of other examples of CO2‐assisted additive absorption are given. This “infusion” process, in effect, amounts to the partitioning of the additive between the CO2‐ and polymer‐rich phases; consequently, the relative solubility of the additive in CO2 and in the polymer is a major factor governing the amount of additive absorbed. Data reported here illustrate the generality and potentially broad applicability of CO2‐assisted polymer impregnation.