bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(N5‐benzyl‐l‐glutamine)‐coated silica gels as chiral stationary phase for direct resolution of hydantoins
Authors: Chen Yun , Yu Duu‐Haur 
Published: April 2003

AbstractPoly(N5‐benzyl‐L‐glutamine) (PNLG), Poly[N5‐(+)‐1‐phenylethyl‐L‐glutamine] [P(+)NLG], and poly[N5‐(±)‐1 phenylethyl‐L‐glutamine) [P(±)NLG] were synthesized from poly [γ‐(β‐chloroethyl)‐L‐glutamate], which, in turn, was obtained by ester exchange of poly(γ‐methyl‐L‐glutamate) with 2‐chlorethanol. The PNLG was found to exist mainly in an α‐helical conformation in the film state by using circular dichroic and infrared spectra. Moreover, the PNLG, P (+) NLG, and P (±) NLG have been coated on macroporous silica gels (10μm) and packed as chiral stationary phases for direct chromatographic resolution of 10 hydantoins. The column bearing PNLG resolved satisfactorily four hydantoins (α = 1.34–1.73), and the enantioselectivity (α) increased with the bulkiness of 5‐substituent in hydantoins. On the other hand, an increase in 2‐propanol concentration of the eluent (2‐propanol/hexane) resulted in a smooth decrease of the capacity factor. However, the selectivity (α) increased slightly, indicating that the α‐helix of PNLG plays an important role in chiral resolution. From these results, it is concluded that the main chiral recognition force is the steric hindrance between the 5‐substituents of hydantoin and the side chains of PNLG. The temperature effect on the resolution of the hydantoins by PNLG was also investigated. © 1993 John Wiley & Sons, Inc.
Graft copolymers of wood pulp and 1‐phenylethene. I. Generality of synthesis and proof of copolymerization
Authors: Meister John J. , Chen Meng‐Jiu 
Published: April 2003

AbstractA method of grafting lignin‐containing materials is now known that allows 1‐phenylethylene (styrene, [100‐42‐5]) graft copolymers of a lignin source to be quantitatively made. The grafting reaction is a solution polymerization often run in aprotic, polar, organic solvents. Grafting changes solubility and surface properties of the lignin‐containing material. The lignin‐containing materials grafted are unbleached wood pulps produced by chemical, thermal, and mechanical pulping. Grafting wood pulp produces a wood‐reinforced, thermoplastic composite. © 1993 John Wiley & Sons, Inc.
Supercritical fluid fractionation of copolymers based on chemical composition and molecular weight
Authors: Pratt J. Alan , Lee Sang‐Ho , McHugh Mark A. 
Published: April 2003

AbstractPoly(ethylene‐co‐methyl acrylate) copolymers of 30, 40, 60, and 70 wt % acrylate in the backbone have been fractionated with supercritical (SCF) propane, propylene, butane, 1‐butene, and chlorodifluoromethane. The fractionations were performed isothermally using an increasing pressure profile that provided gram‐sized fractions with molecular weight distributions of ∼ 1.2 to 2.2 as compared to those of the parent copolymers, which were ∼ 2.6 to 3.5. If the chemical composition distribution of the copolymer is greater than ±2%, it is possible to fractionate with respect to chemical composition by chosing solvents that preferentially dissolve the nonpolar ethylene‐rich or the polar acylate‐rich oligomers. Cloud‐point curves were determined for each copolymer in the SCF solvents to provide an indication of whether the solvent would dissolve the copolymer at temperatures and pressures within the range of the fractionation apparatus. © 1993 John Wiley & Sons, Inc.
Removal of color from effluents using polyamide–epichlorohydrin‐cellulose polymer. II. Use in acid dye removal
Authors: Hwang M. C. , Chen K. M. 
Published: April 2003

AbstractThe ability of polyamide–epichlorohydrin‐cellulose (PAE‐cell) to remove various acid dyes from aqueous solutions was investigated. The classes of acid dyes included the milling type, levelling type, and metal‐complex type. Operational conditions such as PAE‐cell type, dye type, PAE‐cell particle size, dye bath flow rate, filling density in the column, initial dye concentration, pH of solution, and adsorbent mass were studied. The results show that these PAE‐cell polymers exhibit better capacity for acid dye removal than some commercial activated carbons. © 1993 John Wiley & Sons, Inc.
Dangling polymer networks: Glass transition of PU elastomers
Authors: Lee Yng‐Long , Sung Po‐Hou , Liu Hsin‐Tzu , Chou Lain‐Ching , Ku Wen‐Hsiung 
Published: April 2003

AbstractPolyurethane elastomers possessing dangling chains were prepared by partial substitution of the multifunctional polyol with a monohydroxyl alcohol in the reaction with an isocyanate terminated prepolymer. The dynamic mechanical spectroscopy showed that created dangling segements resulted in a broader glass‐transition region. This indicated material with potentially good energy absorbing properties might be prepared from a ‘dangling polymer’ system. © 1993 John Wiley & Sons, Inc.
Studies on co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyester (III): Morphological observation by polarizing microscopy
Authors: Shinn Ted‐Hong , Lin Chen‐Chong 
Published: April 2003

AbstractA series of co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyesters with various compositions were prepared by the copolymerization of either poly(ethylene terephthalate) (PET) polymer or its oligomer as moiety (I) and p‐acetoxybenzoic acid as moiety (II). A detailed description of the crystalline morphology of copolyesters with different compositions as well as under different preparation temperatures is discussed by using a polarized optical micrograph. It is found that the p‐oxybenzoate (POB)/PET copolyesters with the POB moiety content above 60 mol % were shown to be highly anisotropic. It is also believed that the copolyester made from the PET oligomer (OET) as moiety (II) has shorter repeating units than that of the copolyester made from PET polymer (PET) in the main‐chain structure. The solid‐state polymerization may cause the randomization of two units due to a transesterification reaction that is examined by NMR spectroscopy analysis. Using the micrographs with different compositions, parallels between before and after the solid‐state polymerization are contrasted. © 1993 John Wiley & Sons, Inc.
Size exclusion chromatographic measurement of PVC molecular weight distributions
Authors: Pang Simon , Rudin Alfred 
Published: April 2003

AbstractAggregates that may exist in poly(vinyl chloride) (PVC) solutions at ambient temperatures compromise the accuracy of SEC measurements of molecular weight distributions. Aggregate‐free solutions can be produced in 1,2,4‐trichlorobenzene (TCB) by controlling the dissolution time and temperature. SEC measurements were made in trichlorobenzene at 110°C after dissolution for 12 h at 120°C. An on‐line continuous viscometer can be used to determine when aggregate‐free solutions have been produced. The Mark‐Houwink parameters (K = 0.161 mL/g, α = 0.762) can be used for universal calibration procedures in TCB at 110°C. Complete dissolution of the PVC affects the high molecular weight end of the molecular weight distribution. Measured M̄n values are not affected, but Mz's are much higher than those estimated, for example, from room‐temperature SEC analyses in tetrahydrofuran. Molecular weight distributions are also seen to be broader, especially for higher molecular weight PVCs. © 1993 John Wiley & Sons, Inc.
Acrylic acid γ‐ray irradiation‐grafted nylon 4 membranes
Authors: Lai J. Y. , Chen M. H. , Shih C. Y. , Hsu K. Y. 
Published: April 2003

AbstractThis study was to improve the performances of nylon 4 membranes for washing waste‐water treatment of nuclear power plants, e.g., removal of detergent and salt by membranes. The effects of the degree of grafting and ionization on the reverse osmosis performances of acrylic acid (AA)‐grafted nylon 4 membranes by γ‐ray irradiation modification were investigated. The relationships of operating conditions, such as feed concentrations of salt and detergent, operating temperature, and pressure, and the performances of water flux and solute rejection of the prepared membranes were obtained. Water flux of the prepared membranes was highly sensitive with the operating temperature. It was found that an increase in the operating pressure could increase the water flux and the impaction effect directly. Water flux and salt rejection were significantly improved by both ionized and nonionized AA‐grafted nylon 4 membranes compared to ungrafted nylon 4 membranes. Water flux increased rapidly and solute rejection dropped off slightly as the grafted membranes were ionized. The 100% detergent rejection could be obtained by the nonionized AA‐grafted nylon 4 membranes with 38.6 and 69.6% degrees of grafting under various operating conditions. Results obtained showed that these modified nylon 4 membranes were usable for washing waste‐water treatment of nuclear power plants. © 1993 John Wiley & Sons, Inc.
Fractionation of a diblock copolymer in a demixing‐solvent system
Authors: Podes̆va Jir̆í , Stejskal Jaroslav , Kratochvíl Pavel 
Published: April 2003

AbstractPhase behavior of a hydrogenated styrene/isoprene diblock copolymer in a dimethylformamide/methylcyclohexane demixing‐solvent pair has been studied. At a fixed copolymer concentration (1% w/v), the scheme of phase behavior (temperature vs. mixed‐solvent composition) of the system has been found to be complex, with several areas where various supramolecular structures are spontaneously formed. In a particular area of the scheme, a multistep demixing‐solvent fractionation of the copolymer has been performed. The resulting fractions have been characterized and the data used to construct integral distribution functions of copolymer molar mass and copolymer composition. These functions have been compared with those obtained by a previously reported light‐scattering characterization of the whole, unfractionated, nonhydrogenated precursor of the copolymer © 1993 John Wiley & Sons, Inc.
Ultrasonic and thermal properties of γ‐irradiated low‐density polyethylene
Authors: Zahran A. R. R. , Kandeil A. Y. , Higazy A. A. , Kassem M. E. 
Published: April 2003

AbstractThe ultrasonic pulse‐echo technique and differential thermal analysis were utilized to characterize and to monitor the effect of γ‐irradiation on the sonic modulus and the heat effect of low‐density polyethylene. The sonic wave velocity, sonic modulus, and specific gravity exhibit a minimum for samples irradiated at 10 Mrad. A minimum in the heat capacity was observed at 1 Mrad. The estimated relative change of the activation energy of ordering exhibits a minimum at 100 Mrad. Below 10 Mrad, the perturbation and the loss of the crystalline phase override the effect of radiation cross‐linking. From 10 to 100 Mrad, the effect of cross‐linking as well as that of crystallinity are prevailing. Oxidative degradation is dominating above 100 Mrad. © 1993 John Wiley & Sons, Inc.
A stepwise scheme for the calculation of molecular weight distribution in condensation polymers. I. Scheme for monomolecular condensation polymers
Authors: Tung L. H. 
Published: April 2003

AbstractA stepwise scheme has been devised for the calculation of molecular weight distribution in condensation polymers prepared under the condition of unequal reactivity. In the scheme, a condensation polymerization is arbitrarily subdivided into a number of steps. The polymer obtained in one step is treated as the monomer for the next step. In each of the steps, Flory's distribution for the condensation polymer under equal reactivity is used as the molecular weight distribution for that step. Reactivity variances are incorporated into the calculation through the application of weighing factors on the concentrations of the reacting molecules in each of the steps. The distributions of polymers prepared under other unusual conditions, such as monomers with only limited solubility or endcapping at late stages of the condensation reaction, can also be conveniently calculated by this scheme. The treatment presented in this paper is devoted only to polymers prepared by monomolecular condensation. Extension to bimolecular condensation will not be trivial and will be the subject of another paper. © 1993 John Wiley & Sons, Inc.
Characterization of spinel and hydrated spinel‐filled ABS: Antioxidant effect and strength properties
Authors: Cousin P. , Magdzinski L. 
Published: April 2003

AbstractDifferential thermal analyses (DTA) were conducted on spinel‐filled and hydrated spinel‐filled acrylonitrile–butadiene–styrene (ABS) terpolymer. Spinel and hydrated spinel displayed antioxidizing properties in the ABS composite. The enthalpies of oxidation for ABS, spinel‐filled ABS, and hydrated spinel‐filled ABS were 130, 15, and 0 J/g, respectively. Mechanical property measurements show that hydrated spinel reinforcing properties equal that of precipitated calcium carbonate treated with zinc stearate. © 1993 John Wiley & Sons, Inc.
Die extrusion behavior of carbon black‐filled block copolymer thermoplastic elastomers
Authors: Kim Jin Kuk , Han Min Hyeon , Go Jin Hwan , Oh Se Chul 
Published: April 2003

AbstractThe properties of carbon black‐filled thermoplastic elastomers were studied. We compared the extrudate swell behavior and the rheological properties of carbon black‐filled polymers with those of raw polymers. The shear viscosity increases with increasing amount of carbon black. The extrudate swell becomes smaller with increasing carbon black amount, indicated by the decreased elasticity of the material when adding carbon black. © 1993 John Wiley & Sons, Inc.
Bead‐spring polymer melts
Authors: Grisafi S. 
Published: April 2003

AbstractThis analysis of polymer rheology uses conditional probability distributions to describe the phase space dynamics of all macromolecules in a polymer melt. The result is a viscoplastic constitutive equation for the polymer stress. Using conditional probability distributions makes the use of a large number of bead‐spring chains in the modeling system possible, but precludes evaluating the intermolecular contribution to the total stress. Both the kinetic and intramolecular contributions are evaluated for a system composed of an arbitrary number of bead‐spring chains that interact with one another using molecular dispersion forces. The analysis predicts that the kinetic contribution is isotropic and the intramolecular contribution is viscoplastic. The intermolecular contribution is assumed negligible in comparison to the intramolecular contribution because it results from physical bonds among chains, while the intramolecular contribution results from chemical bonds within a chain. © 1993 John Wiley & Sons, Inc.
Hydrogels based on copolymers of N‐(2‐hydroxyethyl) methacrylamide, 2‐hydroxyethyl methacrylate, and 4‐t‐butyi‐2‐hydroxycyclohexyl methacrylate
Authors: Friends G. , Künzler J. , McGee J. , Ozark R. 
Published: April 2003

AbstractA nonionic, high water content, high‐strength hydrogel based on N‐(2‐hydroxyethyl)methacrylamide (HMA), 2‐hydroxyethyl methacrylate (HEMA), and a strengthening agent, 4‐t‐butyl‐2‐hydroxycyclohexyl methacrylate (TBCM). The HMA was prepared by the reaction of methacryloyl chloride with ethanol amine. The copolymerization of HMA with varying concentrations of HEMA and TBCM resulted in transparent hydrogel films possessing a wide range of mechanical and physical properties. A copolymer composition of 79 parts HMA, 20.7 parts TBCM, and 0.3 parts ethylene glycol dimethacrylate (EGDMA) gave a transparent, flexible film possessing a water content of 72.6%, a Young's modulus of 0.45 MPa, oxygen permeability of 28 barrers, and a tear strength of 28 N/m. In contrast, a copolymer composition of 40 parts HMA, 59.7 parts TBCM, and 0.3 parts EGDMA gave a hard, transparent film possessing a water content of 33% and a modulus of 504 MPa. © 1993 John Wiley & Sons, Inc.
Chemiluminescence and thermo‐oxidation stability of poly(2,6‐dimethyl‐p‐phenylene ether) in blends with polystyrene and polybutadiene
Authors: Matisová‐Rychlá Lyda , Chodák Ivan , Rychlý Jozef , Bussink Jan 
Published: April 2003

AbstractIt has been ascertained that chemiluminescence‐time curves for samples of poly(2,6‐dimethyl‐p‐phenylene ether) blended with high‐impact polystyrene containing polybutadiene yield a very reproducible pattern even at a temperature of 190°C. The chemiluminescence light emission has been associated with consumption of double bonds in polybutadiene, and a corresponding rate constant and activation energies of chemiluminescence decay from both the isothermal and nonisothermal parts of chemiluminescence‐time curves have been determined. As demonstrated by these curves, an attempt, to stabilize the blends toward thermooxidation by the peroxide decomposer and stabilizer led to retardation of the oxidation process only and further investigation searching for an optimum stabilizing system is required. © 1993 John Wiley & Sons, Inc.
A fatigue crack initiation map for polycarbonate
Authors: Chen T.‐J. , Bosnyak C. P. , Kao C.‐I. , Chudnovsky A. 
Published: April 2003

AbstractThe mechanisms of fatigue crack initiation for various stress levels and thicknesses have been determined for single‐edge notched specimens of polycarbonate and used to assemble a map. Three basic fatigue crack initiation mechanisms were identified and named as cooperative ductile (the damage zone formed ahead of crack consisting of yielded material), solo‐crack brittle (very little damage zone development), and cooperative brittle (identified as a cloud of microcracks or crazes that developed at the notch tip). With a given applied stress and within the same failure mechanism, the values of the number of cycles to crack initiation decrease with increase in thickness. The transition from cooperative ductile to solo‐crack brittle initiation mechanisms is sudden with increasing thickness. Transition from cooperative ductile to cooperative brittle with decreasing stress was less well defined. Regions where combinations of mechanisms were observed are also identified in the map. © 1993 John Wiley & Sons, Inc.
A new binary accelerator system for the sulfur vulcanization of natural rubber latex
Authors: Mathew George , Kuriakose A. P. 
Published: April 2003

AbstractVulcanization of latex products are usually carried out at lower temperatures compared to dry rubber products. It has been suggested that, in latex vulcanization systems where thiourea is used as a secondary accelerator, it acts as a nucleophilic reagent facilitating the cleavage of the sulfur bonds in the primary accelerator like TMTD or CBS at lower temperature. But no conclusive proof is given to such a postulate. In the present study 1‐phenyl‐2,4‐thiobiuret (DTB II) and 1,5‐diphenyl‐2,4‐dithiobiuret (DTB III), which are more nucleophilic than thiourea and which vary in their nucleophilic reactivity, were studied as secondary accelerators along with tetramethyl thiuram disulphide (TMTD) and N‐cyclohexylbenzothiazyl sulphenamide (CBS) in the vulcanization of natural rubber latex. These binary systems were found to be very effective in reducing the optimum vulcanization time. Also it was noted that 1‐phenyl‐2,4‐dithiobiuret, which is more nucleophilic, is more reactive (as observed from the reduction in optimum cure time) as a secondary accelerator, indicating a nucleophilic reaction mechanism in the vulcanization reactions under review. The optimum dosages of the secondary accelerators required were derived. Physical properties like tensile strength, 300% modulus, and elongation at break of the latex vulcanizates were also studied. There is a definite advantage with respect to many of these properties for dithiobiuret systems compared to the systems containing TMTD alone or TMTD/thiourea. DTB III gives higher values in many of these physical properties than DTB II. Chemical characterization of the vulcanizates was also carried out to correlate the physical properties with the type of chemical crosslinks formed. © 1993 John Wiley & Sons, Inc.
A new class of biodegradable materials: Poly‐3‐hydroxy‐butyrate/steam exploded straw fiber composites. I. Thermal and impact behavior
Authors: Avella Maurizio , Martuscelli Ezio , Pascucci Beniamino , Raimo Maria , Focher Bonaventura , Marzetti Annamaria 
Published: April 2003

AbstractBiodegradable thermoplastic composites reinforced with wheat straw fibers were prepared. The matrix was an expensive polyester, poly‐3‐hydroxy‐butyrate (PHB), produced by bacterial fermentation. Before being mixed with the PHB, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structural changes in lignocellulosics. Such changes enhance the interaction with the thermoplastic matrix. The two components were melt mixed and the composite molded under hot compression. Compared with neat PHB, not only does the composite material show better mechanical properties but, moreover, production costs are dramatically reduced because wheat straw is a very inexpensive product. Finally, FTIR measurements revealed some PHB/straw fiber molecular interactions that interfere with the PHB crystallization. © 1993 John Wiley & Sons, Inc.
High performance semi‐interpenetrating polymeric networks based on acetylene‐terminated sulfone. Part I. Cure and thermal characteristics
Authors: Mai Kancheng , Zeng Hanmin 
Published: April 2003

AbstractA series of semi‐interpenetrating polymer networks (semi‐IPN) have been prepared from acetylene‐terminated sulfone (ATS‐C) oligomer and high‐performance thermoplastic (TP) blends. The cure characteristics and thermal properties of ATS‐C and semi‐IPNs are presented in this paper. The addition of thermoplastics has no effect on the mechanism of ATS‐C cure reaction and thermal behavior of cured systems. The glass‐transition temperature (Tg) and heat distorsion temperature (HDT) of thermoplastics are remarkably decreased with adding ATS‐C. The higher the Tg and HDT of the thermoplastics, the more obvious the reduction of Tg and HDT. In the case of fully cured semi‐IPNs, the Tg and HDT value of the TP phase are higher than or equal to the Tg and HDT of pure TP. The thermal stabilities of semi‐IPNs decrease as the content of ATS‐C oligomer increases. © 1993 John Wiley & Sons, Inc.
Synthesis and thermal characterization of chemically modified cardanol polymers
Authors: Antony Rosy , Pillai C. K. S. 
Published: April 2003

AbstractCardanol was functionalised to incorporate elements such as phosphorus and bromine and polymerised with formaldehyde or hexamethylenetetramine (HMTA) to get flame retardant polymers. Thus, monocardanyl phosphoric acid (MCPA), its bromoderivative (BrMCPA), and their formaldehyde condensates (MCPAF and BrMCPAF) and cross‐linked polymers were prepared and characterized by IR, NMR, and GPC. Flammability and thermal stability of these polymers were evaluated by LOI and TGA, respectively, and compared with those of conventional cardanol‐formaldehyde (CF) resin and its bromoderivative. TGA of MCPAF showed that although it is initially less stable than that of CF, its stability increases above 500°C over that of CF. Char yields of MCPAF and BrMCPAF are 21 and 27, respectively, and corresponding LOI values are 27 and 49. The present data do not support any synergism nor any additive effect between phosphorus and bromine, but a positive interaction between them is indicated with phosphorus mainly contributing in the condensed phase and bromine in the vapour phase mechanism. The activation energies in the range 20–30 kcal/mol for MCPAF suggest an ionic mechanism for its decomposition, whereas mainly a free radical type of decomposition is inferred for BrMCPAF with an activation energy in the range of 35–50 kcal/mol. © 1993 John Wiley & Sons, Inc.