bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical crosslink densit and network structure of natural rubber vulcanizates modified with phosphorylated cardnol prepolymer
Authors: Menon A. R. R. , Pillai C. K. S. , Nando G. B. 
Published: April 2003

AbstractThe chemical crosslink density (CLD) and network structure of natural rubber (NR) vulcanizates, modified with phosphorylated cardanol prepolymer (PCP), have been studied by equilibrium swelling and other chemical methods. The PCP‐modified NR vulcanizates showed lower CLD, as compared to the unmodified NR samples, the decrease being lesser for the semiefficient vulcanization (SEV) system, as compared to the conventional (CV) and efficient (EV) vulcanization system. The superior tensile characteristics of the PCP‐modified vulcanizates of the SEV system is presumed to be partly due to the presence of an entangled network structure between the aliphatic segment of PCP and the isoprene chains, as evident from X‐ray diffraction studies. The critical role of Zn++ions in the crosslinking reactions, especially at higher concentrations of PCP, was evident from the increase in CLD at higher concentrations of ZnO. The reduction in the IR absorption intensity, in the presence of ZnO, indicated the probable complex formation of Zn++ions with the phosphate groups of PCP. © 1994 John Wiley & Sons, Inc.
Diffusion of methyl esters of higher fatty acid in polypropylene
Authors: Hayashi Hiromichi , Sakai Hiroshi , Matsuzawa Shuji 
Published: April 2003

AbstractDiffusion coefficients of several methyl esters of linear higher fatty acid (C10˜C18) into polypropylene (PP) were determined, over the temperature range of 50 to 110°C, using a mass uptake technique. The relations between an amount of mass uptake and t1/2 were linear within 10 min, indicating Fickian diffusion. The diffusion coefficients were in the range of 4.6×10−8 to 6.2×10−12 cm2 sec−1, increased with temperature, and decreased with increasing n‐alkyl chain length of fatty acid. The plots of In D vs. the molecular weight of methyl esters were approximately linear. The temperature dependence of diffusion followed an Arrhenius relationship, and the activation energies were in the range of 133 ˜ 147 KJ mol−1 and increased with an increase in n‐alkyl chain length of corresponding fatty acid. The diffusion coefficients were discussed with the interaction between methyl esters of higher fatty acid and PP. The diffusion coefficients of methyl esters, at the simultaneous diffusion process, were always higher than that derived from the single diffusion process, except for methyl decanoate with lower molecular weight. The difference in diffusion coefficients in single and simultaneous diffusion was discussed thermodynamically. © 1994 John Wiley & Sons, Inc.
On the effect of treating poly(acrylic acid) with argon and tetrafluoromethane plasmas: Kinetics and degradation mechanism
Authors: Terlingen Johannes G. A. , Takens Gijsbert A. J. , Van Der Gaag Frederik J. , Hoffman Allan S. , Feijen Jan 
Published: April 2003

AbstractPoly(acrylic acid) (PAAc) films were treated with either an argon or a tetrafluoromethane (CF4) plasma and subsequently analyzed with X‐ray photoelectron spectroscopy (XPS). PAAc films were decarboxylated during both types of plasma treatments. In addition, during the CF4 plasma treatment, the PAAc films became fluorinated. The plasma phase during the argon plasma treatment of PAAc films was investigated with optical emission spectroscopy. It was shown that during this plasma treatment carbon dioxide, water, and possibly hydrogen were liberated from the PAAc surface. By covering the surface of PAAc films with different materials (lithium fluoride, UV fused silica, and glass) during the plasma treatment, it was possible to differentiate between photochemically induced and particle‐induced changes of the surface. This method was used to show that decarboxylation during the argon plasma treatment was caused by vacuum UV radiation (wavelength < 150 nm) and the decarboxylation/fluorination during the CF4 plasma treatment was induced by reactive fluorine‐containing species from the plasma phase. Furthermore, during both processes, etching of the PAAc surface occurred. Based on these mechanisms, kinetic models were derived that could be used to describe the measured kinetic data adequately. © 1994 John Wiley & Sons, Inc.
The craze‐tip deformation zone in PC/SAN microlayer composites
Authors: Sung K. , Haderski D. , Hiltner A. , Baer E. 
Published: April 2003

AbstractCrazing in styrene‐acrylonitrile copolymer (SAN) layers of polycarbonate (PC)/SAN microlayer composites and the deformation zone that formed in the PC layer in response to the stress concentration created at the PC/SAN interface by the craze tip were examined by optical and scanning electron microscopy. A 49‐layer composite with relatively thick layers, on the size scale of tens of microns, was chosen in order to confine interactions to the region of a single PC/SAN interface. The SAN craze density, which increased with applied stress, was shown to fit the Weibull distribution function. The distance between crazes was described by a correlation length, and the distribution of correlation lengths indicated that crazing occurred randomly in the SAN layers. In the PC layer, the crazetip deformation zone consisted of a colinear plastic zone together with a pair of microshearbands that grew away from the craze tip at an angle of about 45°. Assuming a blunted craze tip, the plastic zone was analyzed using the slip‐line field theory. The dependence of the micro‐shearband length on remote stress was similar to that predicted by both the BCS and Vitek models. © 1994 John Wiley & Sons, Inc.
Effect of compatibilization on the properties of polypropylene/polyamide‐66 (75/25 wt/wt) blends
Authors: Duvall J. , Sellitti C. , Myers C. , Hiltner A. , Baer E. 
Published: April 2003

AbstractInterfacially compatibilized immiscible blends with an isotactic polypropylene matrix (PP) and dispersed polyamide‐66 (PA) were prepared by extrusion with anhydride‐grafted isotactic PP compatibilizers, one of high‐anhydride content (HAC, 2.7 wt % grafted maleic anhydride) and one of low‐anhydride content (LAC, 0.2 wt % anhydride). On a weight basis, HAC was more efficient than LAC in dispersing PA to submicron domains, but on a total weight % anhydride basis, both compatibilizers were equally efficient. Both compatibilizers imparted similar tensile strength improvement compared to an uncompatibilized blend. Maximum fracture strain was obtained at similar total anhydride content, but much higher maximum fracture strain was achieved with LAC than with HAC. Good adhesion in an 11.25 wt % LAC blend was seen at the microscale as fibrillar ligaments connecting PA particles to the drawn PP matrix. Interfacial failure was observed in a lower fracture strain composition, 11.25 wt % HAC. © 1994 John Wiley & Sons, Inc.
Modified lignosulfonate as adhesive
Authors: Chen Rubie , Wu Quoxiong 
Published: April 2003

AbstractOxidized lignosulfonate (LS‐OB) displays a high crosslinking during thermal condensation. When LS‐OB was used as a partial substitute of urea‐formaldehyde (UF) in wood adhesive, a positive effect on the curing of resin could be observed. With 30–40% substitution, no deteriment in strength properties of particleboard was observed. Polycondensation of lignin and UF could occur between methylol groups in UF resin and hydroxyl and carbonyl groups in lignin, through ether bonds and methylene bridges. A high surface activity of LS‐OB would reduce the surface tension of binder solution and facilitate its distribution on wood particles, improving consequently the strength properties of particleboard. © 1994 John Wiley & Sons, Inc.
Water absorption and disc cracking in urethane–methacrylate resins
Authors: Bucknall Clive B. , Zhang Xiang Cheng , Orton Michael L. , Jackson Graham V. 
Published: April 2003

AbstractWater absorption at 23 and 100°C has been studied in three materials based on a single type of urethane–methacrylate resin: the neat resin, a rubber‐toughened blend containing 15 wt % of core‐shell modifier, and a filled rubber‐toughened resin containing 46 wt % silica plus 8 wt % core‐shell modifier. In all six absorption experiments, water diffusion followed Fick's law. However, in neat resin at 100°C, the period of Fickian diffusion, during which the material appeared to reach saturation, was followed by an additional period of water uptake, which was accompanied by formation of internal disc cracks up to 1 mm in diameter. At both 23 and 100°C, fracture of water‐saturated neat resin was defect dominated: cracks were initiated at inorganic impurities between 40 and 80 μm in diameter. The adverse effects of water are attributed to hydration and consequent swelling of these insoluble impurities. No internal cracking was detected in either the rubber‐modified or hybrid resin, which have higher a KICs than the neat resin. © 1994 John Wiley & Sons, Inc.
Crystallization processes in poly(ethylene terephthalate) as modified by polymer additives and fiber reinforcement
Authors: Reinsch Veronika E. , Rebenfeld Ludwig 
Published: April 2003

AbstractThe effect of fiber reinforcement on the crystallization kinetics of poly(ethylene terephthalate), or PET, was investigated using differential scanning calorimetry. The objective of the study was to determine how the effects of fiber reinforcement on PET crystallization are modified by the presence of polymer nucleating and plasticizing additives. Undirectional fiber composites were prepared using aramid and glass fibers in PET. The rate of crystallization of PET, as reflected by crystallization half‐time, is seen to depend on reinforcing fiber type, crystallization temperature, and presence of nucleant or plasticizer. Howerver, degree of crystallinity of PET is largely unaffected by the presence of additives and reinforcing fibers. Crystallization kinetics are analyzed using the Avrami model for PET volume crystallized as a function of time. Avrami plots for PET and fiber‐reinforced PET exhibit two linear regions, possibly corresponding to primary and secondary crystallization. The crystalline morphology of fiber‐reinforced PET was also studied using polarized light microscopy. Results concerning nucleation density and growth morphology are used in explaining differences seen in crystallization kinetics in fiber‐reinforced systems. © 1994 John Wiley & Sons, Inc.
Kinetics of synthesizing 2,4,6‐tribromophenyl benzyl ether in a triphase catalysis
Authors: Wang Maw‐Ling , Peng Ching‐Zou 
Published: April 2003

AbstractThe reaction of benzyl bromide with 2,4,6‐tribromophenol in an organic solvent/aqueous alkaline solution of KOH to synthesize 2,4,6‐tribromophenyl benzyl ether by triphase catalysis was investigated. The macroporous and microporous polymer pellets that served to support the catalyst were prepared by reacting styrene monomers, chloromethylstyrene monomers, and divinylbenzene in a suspension polymerization. Tributylamine was then immobilized on the surface of the polymer pellet to form the three‐phase phase‐transfer catalysts. The effects of the rate of agitation, degree of cross‐linking of the polymer, solvents, inorganic salts, and temperature on the conversion of benzyl bromide and the reaction rate in the three‐phase catalytic reaction were investigated in detail. We recommend that a macroporous polymer pellet with a small degree of cross‐linking be used to react in a highly polar solvent to obtain high conversion of benzyl bromide and a rapid reaction. © 1994 John Wiley & Sons, Inc.
Studies on the structure and properties of nylon 46 fiber. I. Dimensional stability
Authors: Kudo Kazushige , Mochizuki Masatsugu , Kiriyama Shunichi , Watanabe Masaharu , Hirami Matsuo 
Published: April 2003

AbstractThermal shrinkage, viscoelastic properties, wide‐ and small‐angle X‐ray diffractions, and molecular orientation by fluorescence method were measured for fiber samples of nylon 46 [poly(tetramethylene adipamide)] as compared with nylon 66 [poly(hexamethylene adipamide)]. The structural study of nylon 46 fiber indicated that molecular chains are well‐oriented along the fiber axis in the interlamellar region whose thickness is relatively thin. It was also shown that the onset of thermal movement of nylon 46 molecules is shifted to the higher temperature than nylon 66. These characteristics will be attributed to the cause of good dimensional stability, a significant feature of nylon 46 fiber, attractive for its application to industrial usages. © 1994 John Wiley & Sons, Inc.
Determination of functionality and functionality distribution of polyether polyols by quantitative 13C NMR spectroscopy
Authors: Carr Robert H. , Hernalsteen Jan , Devos Julien 
Published: April 2003

AbstractA method is described for the determination of the number average functionality and functionality distribution of polyols based on the measured intensities of relevant end groups observed in 13C NMR spectra. Longitudinal (T1) relaxation time measurements on glycerol‐, trimethylolpropane‐, and pentaerythritol‐initiated copolymers of propylene oxide and ethylene oxide show that the slowest relaxing moiety that needs to be quantified is the vinyl CH2group of the unsaturated side product of the propoxylation reaction. A. chromium (III)‐containing relaxation reagent allows the analysis to be speeded up by decreasing the relaxation times. The relative precision of the functionality measurement is ca. ±1%, while determinations of the mole percentage levels of species with different functionalities can be carried out with a precision better than ±3 mol %. © 1994 John Wiley & Sons, Inc.
The cross‐linking of acrylic rubber in the presence of group IIB metal oxides
Authors: Chowdhury P. , Chakravorti M. C. , Das C. K. 
Published: April 2003

AbstractEffects of group IIB metal oxides (viz., ZnO, CdO, and HgO) on ethylene thiourea (ETU) accelerated the curing of acrylic rubber (ACM) have been evaluated with a view to elucidate the cross‐linking mechanism with special reference to the role of metal oxides. Best results are obtained with CdO in the presence of ETU. ZnOCdO or CdOHgO blends provide no synergism in the state and rate of cure. Formation of metal sulfide and chloride during the cross‐linking reaction has been confirmed by XRD and XPS. Examination of FTIR spectra reveals that cross‐linking occurs at the CCl cure site of the acrylic polymer. Based on spectral and chemical analysis, a reaction mechanism has been put forward. © 1994 John Wiley & Sons, Inc.
Measurement of diffusivity of a liquid diamine in solid epoxies using attenuated total reflectance infrared spectroscopy (FTIR‐ATR)
Authors: Skourlis T. P. , McCullough R. L. 
Published: April 2003

AbstractA number of studies on thermosetting polymeric composite materials have indicated the existence of a three dimensional region of the matrix in the vicinity of the fiber, which exhibits distinct properties. A key factor in the interphase formation of epoxy‐diamine mixtures is the diffusivity of the diamine relative to the epoxy prepolymer. A technique for measuring diffusion coefficients of a liquid through solid polymeric thin layers is described. Infrared attenuated total reflectance (ATR) spectroscopy is used to analyze diffusion couples with infrared distinguishable bands. A cylindrical germanium crystal, coated with the polymeric layer of interest, is immersed in a boat cell filled with the diffusant, and infrared spectra of the system are taken in real time. By those means, only the region close to the solid surface is scanned without interferences from the bulk. The temperature dependence of diffusivity can also be evaluated by the use of a heated cell. Diffusivities that are evaluated in this way can be used to predict stoichiometric gradients during the curing reaction of the system and, therefore, the structure and property gradients of the material around the fiber. © 1994 John Wiley & Sons, Inc.
NMR study of the stabilities of urea–formaldehyde resin components toward hydrolytic treatments
Authors: Chung I‐Ssuer , Maciel Gary E. 
Published: April 2003

AbstractThe solid residues of nine urea–formaldehyde (UF) resins after hydrolytic treatment at pH4 and 86°C for 20 h and the solid residues of one UF resin after eight different hydrolytic treatments were examined by 13C‐CP–MAS NMR. The relative stability toward hydrolysis of each structural component in each UF resin was established for various hydrolytic conditions. In general, UF resins prepared from starting mixtures with a formal F/U molar ratio of 1.00 show a high degree of stability toward hydrolysis. Cross‐linking methylene linkages in the UF resins show a higher susceptibility to hydrolytic treatments at pH 4 and 86°C than do linear methylene linkages. UF resins prepared with an F/U molar ratio of 2.00 are susceptible to hydrolysis at pH 4 and 86°C. Dimethylene ether linkages, methylols attached to tertiary amides, and poly(oxymethylene glycol) moieties are probably the main formaldehyde emitters in UF resin products. © 1994 John Wiley & Sons, Inc.
Microfiber formation: Immiscible polymer blends involving thermoplastic poly(vinyl alcohol) as an extractable matrix
Authors: Robeson Lloyd M. , Axelrod Robert J. , Vratsanos Menas S. , Kittek Margaret R. 
Published: April 2003

AbstractThe utilization of polymer‐blend technology to prepare microfibers via extraction of one of the components is known technology. Achieving fibrillation (microfiber formation) is not an a priori consequence of polymer blends exposed to a shear or elongational flow field. The viscosity ratio, concentration ratio, interfacial tension, and second normal stress function have all been noted to be important factors in achieving fibrillation in polymer blends. It has been found that thermoplastic poly(vinyl alcohol) is particularly effective in this technology, yielding fibrillated systems that can be easily extracted to yield microfibers (0.1–5 μ diameter). Thermoplastic poly(vinyl alcohol) (PVOH) offers cold‐water solubility, biodegradability, and fibrillation characteristics with many commodity polymers (polyolefins, polystyrene, scrap mixtures), thus offering advantages over previously investigated extractable polymers. In addition, the resultant microfibers via this process can be pulped and handled in paper‐making processes. The process for microfiber formation, the process variables, the polymers applicable to the formation of microfibers using PVOH as an extractable matrix, and the properties of the resultant microfibers are discussed with emphasis on the characterization of the microfibers as a fibrous thixotrope additive. Potential utility of the microfibers via this process include polymeric paper and admixtures with cellulosic‐based pulp, oil‐ or water‐adsorbent mats, fibrous thixotrope additives, filters, filler rentention and pitch control in paper applications, and ultralow denier fibers. © 1994 John Wiley & Sons, Inc.
13C CP–MAS NMR study of absorbed water in polyimide film
Authors: Waters J. F. , Likavec W. R. , Ritchey W. M. 
Published: April 2003

AbstractSolid‐state nuclear magnetic resonance (NMR) relaxation studies were performed on Kapton H polyimide films in order to determine the location of water absorption within the polymer lattice and its effects on the microdomain properties of the polymer. Carbon spin lattice relaxation (13CT1), spin lattice relaxation in the rotating frame (T1ρ), and inversion recovery cross polarization (IRCP) experiments were performed to analyze wet and dry Kapton films and films exposed to D2O. The conventional pulse sequences for these experiments were modified with a TOSS acquisition sequence in order to remove spinning side bands from the 13C‐NMR spectra. The data indicates that the water molecules aggregate near the carbonyl group of the imide ring and are most probably bound via hydrogen bonding. Additionally the water molecules plasticize the polymer network by increasing the amplitude of low‐frequency motions. © 1994 John Wiley & Sons, Inc.
A high reynolds number rotating disk rheometer
Authors: Dickerson James P. , Flesher L. Michael , Hester Roger D. 
Published: April 2003

AbstractThe construction and principles of operation of a rotating disk rheometer are outlined as is its use in the study of polymeric fluid drag reduction. The need for a sensitive measuring system under a wide variation of Reynolds numbers has prompted the development of a computer‐controlled system that allows a systematic measurement of the turbulent fluid frictional difference between dilute polymer solutions. Also, the long‐term drag‐reducing stability of macromolecules in a turbulent flow field can be conveniently measured. Representative data from experimental measurements are presented demonstrating the capabilities of this instrument. © 1994 John Wiley & Sons, Inc.
Analysis of the pullout of single fibers from low‐density polyethylene
Authors: Li Jian‐Xin 
Published: April 2003

AbstractIn the present work, a single‐fiber pullout test was used to study the interface/interphase between various fibers and low‐density polyethylene (LDPE) and between glass fibers and a range of other thermoplastic matrices. For well‐bonded fibers, experimental evidence suggests the involvement of plastic deformation and strain‐hardening prior to debonding and pullout. The interfacial shear strength was determined to be the ultimate shear strength of the matrix and was found to be insensitive to the fiber surface structure. A new theoretical model was developed to predict the relationship between the debonding force and the embedded length. The contribution of friction to the debonding force was found to be insignificant when compared with the contribution of plastic deformation. © 1994 John Wiley & Sons, Inc.
Melting behavior of ultra‐high modulus and molecular weight polyethylene (UHMWPE) fibers
Authors: Hsieh You‐Lo , Ju Jie 
Published: April 2003

AbstractSuperheating and double‐melting endotherms are the characteristic melting behaviors of gel‐spun ultra‐high modulus and molecular weight polyethylene (UHMWPE) fibers in differential thermal analysis (DTA). A mostly orthorhombic structure with very little amorphous content is indicated by wide angle x‐ray scattering (WAXS) data. The melting temperatures are elevated and believed to result from superheating and incomplete chain relaxation in the highly oriented and crystalline structure. The melting behavior of the fibers is shown to be strongly affected by changes in polymorphic transformations and in intercrystalline disordered domains. Compression in the direction perpendicular to fiber axis causes significant increases in the 110 and 200 dimensions of the orthorhombic structure. Such lateral compression increases monoclinic forms and perhaps amorphous content, and decreases the degree of transformation to hexagonal phase. Superheating, which is related to the intercrystalline stress, can be reduced by the presence of interacting solvents such as trichlorbenzene. © 1994 John Wiley & Sons, Inc.