bluuebunny/crossref_metadata_2025_split huggingface dataset:
Curing of unsaturated polyester resins: Effects of comonomer composition. II. High‐temperature reactions
Authors: Huang Yan‐Jyi , Chen Chaur‐Jeng 
Published: April 2003

AbstractThe effects of comonomer composition of the curing kinetics of unsaturated polyester (UP) resins at 100–120°C were investigated by differential scanning calorimetry (DSC) and infrared spectroscopy (IR) over the entire conversion range. One commercial UP resin, UP2821, with 6.82 unsaturated CC bonds per polyester molecule, was used. For styrene/UP2821 reactions, experimental results of the initial and maximum reaction rates by DSC at 100–120°C revealed that the styrene content, as well as the reaction temperature, would affect the formation of microgel structures. As the initial molar ratio of styrene to polyester CC bonds increased, the styrene swelling effect could enhance the intramicrogel crosslinking reactions, while the styrene dilution effect could diminish the intermicrogel crosslinking reactions. The competition between the two reactions would depend on the reaction temperatures. Finally, a microgel‐based reaction mechanism was proposed for the high temperature reactions. © 1993 John Wiley & Sons, Inc.
The reaction engineering of the anionic polymerization of isoprene
Authors: Chang C. C. , Halasa A. F. , Miller J. W. 
Published: April 2003

AbstractThe anionic solution polymerization of isoprene with n‐butyllithium (n‐BuLi) initiator and tetramethylethylenediame (TMEDA) modifier or n‐butyllithium (n‐BuLi)initiator and tripiperidinophosphine (TPPO) modifier was studied and kinetic and reactor models are proposed for both systems. Reactor conversion, molecular weight distribution, and polymer glass transition temperature had been calculated from the model and compared favorably to actual data for various combinations of reactor system and operating conditions. Simulations of the models can be used to design reactor systems, and predict polymer properties of a large‐scale operation from results of small‐scale batch reactor runs. © 1993 John Wiley & Sons, Inc.
Aerobic biodegradation of cellulose acetate
Authors: Buchanan Charles M. , Gardner Robert M. , Komarek Ronald J. 
Published: April 2003

AbstractTwo separate assay systems were used to evaluate the biodegradation potential of cellulose acetate: anin vitroenrichment cultivation technique (closed batch system), and a system in which cellulose diacetate (CDA) films were suspended in a wastewater treatment system (open continuous feed system). Thein vitroassay employed a stable enrichment culture, which was initiated by inoculating a basal salts medium containing cellulose acetate with 5% (v/v) activated sludge. Microscopic examination revealed extensive degradation of CDA (DS = 2.5) fibers after 2–3 weeks of incubation. Characterization of the CA fibers recovered from inoculated flasks demonstrated a lower average degree of substitution and a change in the mol wt profiles.In vitroenrichments with CDA (DS = 1.7) films were able to degrade > 80% of the films in 4–5 days. Cellulose acetate (DS = 2.5) films required 10–12 days for extensive degradation. Films prepared from cellulose triacetate remained essentially unchanged after 28 days in thein vitroassay. The wastewater treatment assay was less active than thein vitroenrichment system. For example, approximately 27 days were required for 70% degradation of CDA (DS = 1.7) films to occur while CDA (DS = 2.5) films required approximately 10 weeks before significant degradation was obtained. Supporting evidence for the biodegradation potential of cellulose acetate was obtained through the conversion of cellulose [1‐14C]‐acetate to14CO2in thein vitroassay. The results of this work demonstrate that cellulose acetate fibers and films are potentially biodegradable and that the rate of biodegradation is highly dependent on the degree of substitution. © 1993 John Wiley & Sons, Inc.
Crystallization of rare earth oxide‐filled polypropylene
Authors: Liu Jingjiang , Tang Gongben , Qu Guijie , Zhou Huarong , Guo Qipeng 
Published: April 2003

AbstractA study has been made of the crystallization behavior of polypropylene (PP) filled with rare earth oxides under isothermal conditions. These rare earth oxides include lanthanum oxide (La2O3), yttrium oxide (Y2O3), and a mixture of rare earth oxides containing 70% Y2O3 (Y2O3–0.70). A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt. During isothermal crystallization, dependence of the relative degree of crystallinity on time was described by the Avrami equation. It has been shown that the addition of any of the three rare earth oxides causes a considerable increase in the overall crystallization rate of PP but does not influence the mechanism of nucleation and growth of the PP crystals. The analysis of kinetic data according to nucleation theories shows that the increase in crystallization rate of PP in the composites is due to the decrease in surface energy of the extremity surfaces. The relative contents of the β‐form in the composites are somewhat higher than that in the plain PP. However, the contents of the β‐form in the plain PP and the composites are all very low relative to those of the β‐form and the influence of the formation of the β‐form on the crystallization kinetics can be neglected. © 1993 John Wiley & Sons, Inc.
Effect of solid‐state curing on the viscoelastic properties of poly(phenylene sulfide)
Authors: Scobbo James J. 
Published: April 2003

AbstractPPS is a thermosetting/thermoplastic resin. The resin, upon exiting the polymerization process, is generally a low viscosity, low molecular weight material. The thermosetting character is therefore exploited in a solid state cure process in the presence of air at elevated temperatures. This produces a resin with a more desirable property profile. Melt state dynamic mechanical measurements have been made on a series of cured PPS resins to elucidate structural changes that occur on the molecular level during the cure process. Increases in viscosity, non‐Newtonian behavior, and relative elastic response were observed with increasing cure time and have been attributed to an increasing molecular weight and broadening molecular weight distribution achieved through branching/crosslinking. The effects of various environments on curing have also been investigated. © 1993 John Wiley & Sons, Inc.
Mixtures of tetrabromobisphenol‐A polycarbonate and bis (2‐ethoxyethyl) ether: Examples of a lower critical solution temperature
Authors: Beck H. N. 
Published: April 2003

AbstractTetrabromobisphenol‐A polycarbonate was found unexpectedly to form mixtures with the solvent bis(2‐ethoxyethyl) ether that display a lower critical solution temperature at about normal room temperature and less than about 10 wt % polymer. © 1993 John Wiley & Sons, Inc.
A generalized model to predict the viscosity of solutions with suspended particles. I
Authors: Sudduth Richard D. 
Published: April 2003

AbstractSeveral suspension equations available in the literature have been found to have a common derivative form. This common derivative was found to be equivalent to a ratio of the intrinsic viscosity, [η], and a quantity, Vint, defined as the ldquo;relative suspension interaction volume” available for particle flow. Vint was, in general, found to be a relatively simple function of the suspension particle volume fraction, φ, the maximum particle packing fraction, φn, and a new variable, σ, defined as the particle interaction coefficient. Different forms of this common derivative were obtained by modifying VInt with a simple adjustment for the value for the interaction coefficient, σ. Integration of this generalized derivative yielded a generalized suspension viscosity equation that was found to predict the form of many suspension equations that have previously appeared in the literature. For example, by varying the interaction coefficient, σ, the Arrhenius equation resulted when σ = 0, the Kreiger‐Dougherty equation resulted when σ = 1, and when σ = 2, the Mooney equation resulted. Fractional values for the particle interaction coefficient were also found to be useful when optimizing the empirical fit of the literature data of Vand and Eiler. Additional insight from such a data fit can also be obtained from the magnitude of both the particle interaction coefficient, σ, and the packing fraction, φn. © 1993 John Wiley & Sons, Inc.
Preparation and performance of poly(vinyl butyral) membrane for ultrafiltration
Authors: Gotoh Masao , Tamiya Ellchi , Karube Isao 
Published: April 2003

AbstractUltrafiltration membrane was prepared from poly(vinyl butyral). The effects of membrane thickness, polymer concentration, evaporation time, and evaporation temperature, etc., on the performance of the resulting membranes have been studied. Dimethylacetamide was used as a casting solvent. The membrane formed by casting the polymer from a 15 wt % solution and evaporation at 25°C for 30 s had a flux value of 250 cm3 / cm2 h (4.8 kg/cm2, 26°C) at 92.9% rejection level for dextran sodium sulfate (average mol. wt. 550,000) separation. © 1993 John Wiley & Sons, Inc.
Kinetics of epoxy resins formation from bisphenol‐A, bisphenol‐S, and epichlorohydrin
Authors: Jungang Gao 
Published: April 2003

AbstractThe kinetics of formation of epoxy resins derived from bisphenol‐A, bisphenol‐S, and epichlorohydrin under stoichiometric conditions was considered. The kinetics of reaction was studied by taking into account the consumption of the added alkali and epoxide value of epoxide oligomers. The obtained results satisfactorily explained that the reactivity of bisphenol‐A with epichlorohydrin is higher than that of bisphenol‐S, the rate of dehydrochlorination of chlorohydrin ether in the presence of alkali and water is much higher than that of the rate of condensation of phenolic hydroxyl group with epichlorohydrin. The apparent reaction order of phenolic groups with epichlorohydrin and terminal epoxide group in the oligomer are all second order. The rate constants and activation energy were determined. The results are discussed. © 1993 John Wiley & Sons, Inc.
Structure‐property relationship of HTPB‐based propellants. II. Formulation tailoring for better mechanical properties
Authors: Manjari R. , Somasundaran U. I. , Joseph V. C. , Sriram T. 
Published: April 2003

AbstractThere has been a constant endeavor to improve the mechanical properties of hydroxylterminated polybutadiene (HTPB) ‐based composite solid propellants. A systematic study has been conducted on different batches of HTPB resins with varying molecular weights and hydroxyl values. Propellant formulation experiments were conducted wherein the ratio of chain extender to crosslinker was systematically varied, with a view to achieve the maximum possible strain capability and moderately high tensile strength, keeping all other parameters constant. The influence of increasing hydroxyl content from trimethylolpropane at the expense of hydroxyl content from butanediol, on the mechanical properties of the finished propellant, has been depicted on 3‐dimensional graphs. The isoproperty lines, plotted as a triangular chart with the percentage hydroxyl contents from the three constituents, can be used to arrive at the suitable formulation for a specified application depending upon the OH value of the resin. HTPB resins with high molecular weight, low functionality, and low hydroxyl value require higher levels of trifunctional curing agent and higher NCO / OH ratios to obtain outstanding mechanical properties, especially elastic properties, compared to low molecular weight, high functionality resins. The impact of hard and soft segment domain structure on the mechanical behavior of the cured systems is more pronounced in the low molecular weight resin formulations due to the higher hard segment content compared to those attainable in high molecular weight resin formulations. © 1993 John Wiley & Sons, Inc.
The removal of color from effluents using polyamide‐epichlorohydrin‐cellulose polymer. I. Preparation and use in direct dye removal
Authors: Hwang M. C. , Chen K. M. 
Published: April 2003

AbstractA novel series of adsorbents have been prepared by reacting adipic acid, diethylenetriamine, epichlorohydrin, and cellulose. The structural features of these polyamide‐epichlorohydrin‐cellulose (PAE‐Cell) polymers have been confirmed by IR analysis. The ability of PAE‐Cell polymers to adsorb direct dyes from aqueous solution has been evaluated in a fixed bed column system. These PAE‐Cell polymers have been found to exhibit a better capacities for direct dye removal than some commercial activated carbons.© 1993 John Wiley & Sons, Inc.
Water penetration in glassy polymers: Experiment and theory
Authors: Best M. , Halley J. W. , Johnson B. , Vallés J. L. 
Published: April 2003

AbstractWe describe the design and implementation of a method based on infrared monitoring of the OD stretch mode which permits measurement of the diffusion profiles of water permeating glassy polymers for the first time. Results for several glassy polymers are compared with a theory of trapping diffusion which leads to a nonlinear diffusion problem in which the trapped water penetrates the polymer as a sharp front if there is a large amount of trapping. In the case of two of the polymers studied, the trapping model describes the data, very well (much better than a simple diffusion model) and permits determination of parameters related to the free volume and the residence time of the water on traps in the model. © 1993 John Wiley & Sons, Inc.
Molecular weight estimation by pressure during polymerization
Authors: Otake Katsuto , Yasuda Toshiyuki , Aihara Akio , Yokoyama Chiaki , Takahashi Shinji 
Published: April 2003

AbstractExperimental studies for the mol wt estimation by pressure was performed with a batch polymerization of phthalic anhydride (PA) and ethylene glycol (EG). Experimental results show that the pressure in the reactor can be utilized to estimate the mol wt of products. © 1993 John Wiley & Sons, Inc.
Primers for adhesive bonding to polyolefins
Authors: Yang Jiyue , Garton Andrew 
Published: April 2003

AbstractWhen polypropylene (PP) and low density polyethylene (LDPE) are coated with about 100 nm of triphenylphosphine (TPP) or cobalt acetylacetonate (CaAcac2) primers, adhesive bonds can be made using ethyl cyanoacrylate (CA) adhesive. These bonds are sufficiently strong so that the bond strength exceeds the bulk shear strength of the polyolefin, and are sufficiently durable as to withstand immersion in boiling water for long periods of time. The dependence of adhesive bond performance on primer thickness, application solvent, aging of primed surface, and the durability of bond, are explained on the basis of a model where the primer dissolves in the polymer surface and facilitates interpenetration of the polyolefin and the monomeric CA. The primer catalyzes cure of the CA, resulting in entanglement of adhesive and adherend chains. This model is tested using infrared (IR) spectroscopic, x‐ray spectroscopic (XPS), and microscopic (SEM) analysis. © 1993 John Wiley & Sons, Inc.
Preparation and characterization of polystyrene terminated with an organic sulfide group and styrene–vinyl acetate block copolymer
Authors: Liu Fu‐Tian , Cao Shu‐Qin , Yu Xian‐Da 
Published: April 2003

AbstractPolystyrene terminated with an organic sulfide group was prepared by styrene bulk polymerization using three organic disulfides as initiators, and the content of the organic sulfide group (X̄n) was determined quantitatively from the data of UV and M̄n.Styrene–vinyl acetate block copolymer was prepared by using polystyrene ended with the organic sulfide group as the photosensitizer to initiate vinyl acetate polymerization. The copolymer was characterized by IR, 1H‐NMR, 13C‐NMR, DSC, and TEM, respectively.Different copolymerization conditions were investigated systematically. The result reveals that the X̄n value is a key factor in the copolymerization and the copolymerization proceeds via living radical mechanism. © 1993 John Wiley & Sons, Inc.
A study of rheological properties and crystallization behavior for HDPE melts during extrusion
Authors: Ness J. N. , Liang J. Z. 
Published: April 2003

AbstractThe influence of temperature and shear rate on the flow behavior of high density polyethylene (HDPE) melts during extrusion has been investigated by using a Ceast Rheovis 2100 capillary rheometer which was manufactured by the Ceast Co. in Italy. It was found that the entry pressure drop for the samples was very low during extrusion, the relationship between shear stress and shear rate did not obey the power law strictly, and the phenomenon of shear‐induced crystallization was easily produced when temperature was near the melting point of the samples, even though the shear rate was not high. The dependence of the shear viscosity for the samples on temperature can be described by using the Arrhenius equation. © 1993 John Wiley & Sons, Inc.
Morphological origin of super toughness in poly(ethylene terephthalate)/polyethylene blends
Authors: Carté Theresa L. , Moet Abdelsamie 
Published: April 2003

AbstractA compatibilization strategy for poly(ethylene terephthalate) (PET) and polyethylene (PE) blends to achieve high toughness is described. Maleic anhydride functionalized styrene–ethylene–butylene–styrene (MA‐g‐SEBS) block copolymer at 20 pph was found to produce an intricate multidomain morphology in which the two major components (50% PE, 50% PET) and the compatibilizer coexist on a hierarchal order. A portion of the PET was dispersed as interconnected rodlike domains oriented along the injection direction. The rest of the PET and the PE constituted beadlike nano domains which served as the matrix. The blend at all these morphological levels responded to deformation in a cooperative fashion giving rise to a super tough material. That is, a blend whose elongation at break (600%) was superior to its two major components (90% for PET and 300% for PE). © 1993 John Wiley & Sons, Inc.
Comonomer enhancement effect of 1‐hexene in ethylene copolymerization catalyzed over MgCl2/THF/TiCl4 catalysts
Authors: Kim I. , Kim J. H. , Choi H. K. , Chung M. C. , Woo S. I. 
Published: April 2003

AbstractHomo‐ and copolymerization of ethylene were performed by using a catalyst system composed of TiCl4/THF/MgCl2 complex activated with AlEt3 at 70°C and 3 atm. To investigate the effect of the compositional difference of the catalyst on the rates of homo‐ and copolymerization and on the reactivity in ethylene–hexene copolymerization, a series of six catalysts with different compositions (Mg/Ti = 0.4–16.5) were prepared by coprecipitation. The catalytic activity in ethylene polymerization increased sharply with the Mg/Ti ratio from 21 (Mg/Ti = 0.4) to 1477 kg PE/g‐Ti h (Mg/Ti = 16.5). The activity in copolymerization with 1‐hexene also increased with Mg/Ti ratio. The values of r1 were 120, regardless of Mg/Ti ratios within the experimental error range. Enhancement of the polymerization rate by the addition of 1‐hexene in the reaction medium was observed only for the catalysts of low Mg/Ti ratio. This unusual effect of 1‐hexene on the polymerization rate was explained by chemical and physical processes that occurred during polymerization. © 1993 John Wiley & Sons, Inc.
The polymerization mechanism and kinetics of DGEBA with BF3‐MEA
Authors: Tackie Michael , Martin George C. 
Published: April 2003

AbstractThe diglycidyl ether of bisphenol‐A (DGEBA) and boron trifluoride monoethylamine (BF3‐MEA) were used in a model system to investigate the chemical and physical changes that occur during polymerization. Experiments using 19F and 1H nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) showed that BF3‐MEA breaks down rapidly into HBF4 and an amine salt at 85°C and above. The HBF4 complexes with the epoxy groups, producing an activated monomer that reacts with epoxy in an etherification reaction. A mechanism is proposed whereby activated epoxy sites (complexes) continuously add epoxy throughout the reaction, but where unactivated epoxies (monomer molecules) are unable to react with each other. The reaction rate and mode (kinetic vs. diffusion control) therefore are strongly influenced by the BF3‐MEA concentration and the reaction temperature. © 1993 John Wiley & Sons, Inc.
Relaxations in thermosets. XXV. Calorimetric studies of the curing kinetics of pure and rubber‐containing epoxy‐based thermosets
Authors: Wasserman S. , Johari G. P. 
Published: April 2003

AbstractThe curing kinetics of diglycidyl ether of bisphenol‐A, with ethylene diamine, propylene diamine, and hexamethylene diamine, with 60 wt % amine‐terminated butadiene acrylonitrile (ATBN) and without, have been measured under both isothermal and ramp‐curing conditions. The phase separation of ATBN is undetectable by calorimetry, but has a significant effect on both the rate of curing and the extent of cure. In all cases, its presence decreases the extent of cure and lowers the Tg of the thermoset formed. The total heat of reaction for the curing is 445 ± 15 J/g and remains unaffected by both the presence of an elastomer and the increase in the molecular size of the curing agent. None of the formalisms available for the curing kinetics of epoxy‐based thermosets is consistent with the results for the neat thermosets. The average activation energy for the reactions increases from 107 to 150 kJ/mol when ethylene diamine is replaced by hexamethylene diamine, but curing reaches near completion in a shorter time with the latter than with the former. The Tg of the latter thermoset is lower than that of the former and follows a decreasing trend with increase in the molecular size of the curing agent—an effect that is related to the increase in the length of cross‐links in the network structure. © 1993 John Wiley & Sons, Inc.
A study on the preparation and performance of polydimethylsiloxane‐coated polyetherimide membranes in pervaporation
Authors: Bai J. , Founda A. E. , Matsuura T. , Hazlett J. D. 
Published: April 2003

AbstractSeparation of acetic acid/water mixtures by pervaporation was attempted by silicone rubbercoated polyetherimide membranes. In particular, the effect of the pore size of the polyetherimide membrane and the condition of silicone rubber coating on the performance of the composite membrane was investigated. It was found that the composite membrane could become either water selective or acetic acid selective, depending on the pore size of the support membrane and the condition of the silicone rubber coating. Thus, the overall performance of the composite membrane can be governed, either by the top coated layer or by the bottom support layer.
Pressure–volume–temperature relationships for polymeric liquids: A review of equations of state and their characteristic parameters for 56 polymers
Authors: Rodgers Patrick A. 
Published: April 2003

AbstractA review of theoretical equations of state for polymer liquids is presented. Characteristic parameters for six equations of state, as well as parameters for the empirical Tait equation, are given for 56 polymers where pressure–volume–temperature (PVT) data over a wide range of conditions could be found in the literature. New PVT data are presented for four polymers: poly(epichlorohydrin), poly(ϵ‐caprolactone), poly(vinyl chloride), and atactic polypropylene. All six equations of state provide adequate fits of the experimental specific volume data for the 56 polymers in the low pressure range (up to 500 bar). The modified cell model of Dee and Walsh, the Simha–Somcynsky hole theory, the Prigogine cell model, and the semiempirical model of Hartmann and Haque, were all found to provide good fits of polymer liquid PVT data over the full range of experimental pressures. The Flory–Orwoll–Vrij and the Sanchez–Lacombe lattice–fluid equations of state were both significantly less accurate over the wider pressure range. © 1993 John Wiley & Sons, Inc.