bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nylon/Kevlar composites. II: Investigation of interfaces
Authors: Yu Z. , Ait‐Kadi A. , Brisson J. 
Published: May 2005

AbstractThe aim of this article was the investigation of the fiber‐matrix interface of nylon/Kevlar composites. Both washed fibers and chemically treated fibers were used as reinforcements for nylon‐6 and nylon‐l1. Improvements of the mechanical properties were related to the increase in the nucleating abilities of the fibers, which was modified considerably by chemical treatments. Differential Scanning Calorimetry (DSC), X‐Ray diffraction, optical microscopy, and scanning electron microscopy were used to investigate the interface between the matrix and the fibers. The chemical treatments performed on the Kevlar fibers were found to affect the size of the transcrystalline zone and its crystal structure.
Morphology and mechanical performance of polyphenylenesulfide carbon fiber composite
Authors: Caramaro L. , Chabert B. , Chauchard J. , Vu‐Khanh T. 
Published: May 2005

AbstractThis paper presents the influence of fibers on crystallization kinetics and on matrix morphology for poly(phenylene sulfide)/carbon composite. The following parameters were also considered: thermal stability, fusion/crystallization conditions and surface treatment of carbon fibers. In order to correlate these results with mechanical properties, composite samples were prepared and tested in both static and dynamic modes. The delamination resistance of the composite in shear Mode II is also discussed.
Impact damage resistance of graphite/epoxy laminated composites
Authors: Choi Hyung Yun , Chang Fu‐Kuo 
Published: May 2005

AbstractDamage in graphite/epoxy laminated composites resulting from low‐velocity impact was studied. The impact damage mechanisms and mechanics were first investigated by adopting the impactors with a line‐nosed head from which the damage was simplified from a complicated three‐dimensional pattern to a two‐dimensional one. Based on the results of the line‐loading impact study, a model was developed for predicting the impact damage in the materials resulting from point‐loading impact. The model consists of a stress analysis for calculating transient dynamic stresses during impact and a failure analysis for predicting the extent of delaminations resulting from the impact. A computer code, “3DIMPACT”, was developed based on the model during the investigation. The predictions from the code agreed fairly well with the test data.
Fluorescence monitoring of twin screw extrusion
Authors: Bur Anthony J. , Gallant F. Mitchell 
Published: May 2005

AbstractAn optical fiber probe has been constructed in order to obtain real‐time measurements of fluorescence radiation during twin screw mixing and extrusion of plasticized polybutadiene and calcium carbonate particulate. The probe consists of an optical fiber bundle which was inserted along the axis of a half‐inch sensor bolt, and it was used to transmit optical excitation energy to the processed material and to detect the subsequent fluorescence. The source of fluorescence radiation was a fluorescent dye which was doped into the processed ingredients at very low concentrations. Although most of our measurements were taken with the probe positioned close to the exit die, the sensor bolt can be placed in any instrumentation port along the extruder line. Experiments were carried out to measure residence time distribution, quality‐of‐mix, and mix concentrations as a function of processing conditions. Product mix changes in response to variations in material feed rates and screw RPM were also observed. Values of residence time were obtained by measuring the transit times for the dye to travel from an upstream injection port to the measurement probe, a distance of 63 cm. Flow instabilities, such as mat formation of the solids, were observed by noting the abrupt changes and discontinuities in the fluorescence signal.
Parametric study of a 2‐d model of the nip region in a counter‐rotating, non‐intermeshing twin screw extruder
Authors: Bigio David , Zerafati Saeid 
Published: May 2005

AbstractWithin the polymer processing industry, the demand for more efficient mixing within the existing mixer geometries and keeping a tighter control over increasingly difficult applications calls for a quantitative understanding of the role of the mixer geometry on the mixing performance. An important extruder geometry to consider is the Counter‐Rotating, Non‐Intermeshing Twin Screw Extruder (CRTSE). Recent studies suggest that the greater than linear mixing performance in this geometry may be attributed to the flow in the nip region. Solution of the fluid dynamic equations for a 2‐D model of the nip region was found in order to quantify mixing using a FEM software called FIDAP which was available to us on the CRAY X‐MP supercomputer at San Diego Supercomputer Center. In order to study the effects of design parameters in the nip region, an arbitrary interface was placed in the entrance of the region. A program called “LINE” tracks the path and growth of the interface through the region. Measures of mixing are computed and compared. Effect of several design parameters on mixing performance are studied. Conclusions are presented as to the relative effect of various design parameters. Discussions regarding the measures of mixing and mixing efficiency are presented.
Isothermal and dynamic reaction kinetics of high performance epoxy matrices
Authors: Kenny J. M. , Trivisano A. 
Published: May 2005

AbstractThe reaction kinetics of the epoxy matrix of a commercial prepreg for high performance composites, based on tetraglycidyl diamino diphenyl methanediamino diphenyl sulfone (TGDDM‐DDS) formulation, has been characterized by differential scanning calorimetry (DSC). A phenomenological kinetic model, able to describe the behavior of the system during normal processing operations has been formulated. The diffusion control phenomena, related to the evolution of the glass transition temperature as a function of the degree of polymerization, has been considered in the formulation of the kinetic model. Isothermal and dynamic tests have been used to calculate the model parameters and to verify the proposed model. The model is able to describe incomplete reactions in isothermal tests and heating rate dependence of dynamic test thermograms, and it has been also successfully applied to DSC experiments performed with complex thermal conditions commonly used in the processing of high performance composites.
Effects of thermoplastic additives on the cure of unsaturated polyester resins
Authors: Hsu C. P. , Kinkelaar M. , Hu P. , Lee L. James 
Published: May 2005

AbstractThermoplastic additives tend to promote the phase separation during the reaction of unsaturated polyester resins. Consequently, they reduce the amount of shrinkage during curing. Several thermoplastic additives which resulted in significant different microstructure of cured resins were investigated. The effects of microstr acture formation on the sol‐gel transition, reaction kinetics, and gelation time were studied. The mechanism of microstructure formation and causes of macro‐gelation were explained by the influence of thermoplastic additives on the particle formation rate and inter‐particle reaction rate during curing.
Application of compensation phenomena to the thermal analysis characterization of polymers: Introducing the degree of disorder (DOD) number:
Authors: Ibar J. P. 
Published: May 2005

AbstractThe objective of this article is to show that a deconvolution of the globalTgrelaxation peak obtained by thermal stimulated current characterization technique leads to a better understanding of the coupling characteristics between the relaxation modes. The degree of coordination, i.e., coupling, is function of the state of the system and is revealed by the compensation phenomenon characteristics. In a compensation phenomenon, Arrhenius lines gather into packs of lines which converge to a single point, “the compensation point”. The coordinates of the compensation point are dependent on the actual state of the glass. We find that plots of the thermo‐kinetic variables against the polarization temperatureTp, whenTpvaries, leads to characteristic results of the Relaxation Map:Tgis characterized by a maximum of the Entropy of activation (and of the enthalpy of activation), and also by the existence of two compensation lines, one positive one negative, which intercept forTp=Tg. The relaxation map looks like a “Z” acrossTg, as the Arrhenius relaxation lines gather into either a positive or negative compensation. We introduce a new method to characterizeTg, and to determine, from theZ‐structure, the activation entropy ΔSg, and the activation enthalpy ΔHgatTg.
Effects of polymer structure on the onset of processing defects in linear low density polyethylenes
Authors: Karbashewski E. , Rudin A. , Kale L. , Tchir W. J. , Schreiber H. P. 
Published: May 2005

AbstractLinear low density polyethylenes are manufactured by copolymerizing ethylene with 1‐alkenes, yielding a linear polyethylene backbone with short side chains. Due to the nature of the catalyst used in the polymerizaton, multimodal branching distributions are typically obtained. In this report, we have investigated the processability of four 1‐octene linear low density polyethylenes as a function of the short chain branching distribution. Analytical techniques such as 13C nuclear resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, and temperature rising elution fractionation, in particular were used to elucidate the molecular structure. Processability measurements were made using various extrusion techniques and dynamic mechanical analyses.It was determined that in the absence of any variations in molecular weight, the polymers with the higher proportions of linear polyethylene showed inferior processability In terms of onset of surface imperfections at lower extrusion rates. Polymers with worse processability characteristics also exhibited higher zero shear viscosities.
Shear and elongational viscosities of a thermotropic liquid crystalline polymer and its blend with polycarbonate
Authors: Beery D. , Kenig S. , Siegmann A. , Narkis M. 
Published: May 2005

AbstractThe shear and elongational viscosities of a thermotropic liquid crystalline polymer (LCP), polycarbonate (PC), and their 20%LCP/80%PC blend, were studied using a capillary rheometer. The investigation focused on experimental studies using two sets of capillaries. The first set comprised capillaries having a converging entrance followed by a cylindrical section. The second set, “zero length” set, included capillaries having only the converging section. In the two sets various entrance angles were used. Experimental results have shown that shear viscosities and entrance pressures are practically independent of the entrance angles. The entrance pressure drop was small in the case of PC and reached 50% of the total pressure drop for LCP. The elongational viscosities of the LCP were found to be higher than those of the PC in the elongational‐rate range studies, while shear viscosities of the LCP were higher in the lower shear rate region and lower in the higher shear rate region compared to those of PC. This was attributed to the orientability of LCP in elongational and shear flows.
Reduction in domain size in polymer mixtures via charge transfer interactions
Authors: Clark J. N. , Higgins J. S. , Peiffer D. G. 
Published: May 2005

AbstractBlends of zinc neutralized sulfonated ethylene‐propylene‐diene elastomer (ZnS‐EPDM) with poly(styrene‐co‐vinyl pyridine) have been compared with mixtures of the unfunctionalized rubber with the same copolymer. These binary component blends contain relatively low levels of interacting groups, which are, however, sufficient for the formation of intermolecular complexes. As a result of these interactions, marked enhancement in properties have been observed. In this study, small angle neutron scattering (SANS) is used to determine domain dimensions. The SANS experiments clearly show a decrease in domain size by three orders of magnitude when compatibilization via the sulfonate groups takes place. This reduction correlates with large changes in mechanical properties.
The effect of reactive monomers and functional polymers on the mechanical properties of an unsaturated polyester resin
Authors: Rodriguez Ernesto L. 
Published: May 2005

AbstractA general‐purpose unsaturated polyester resin with 2:1 mol ratio of styrene to polyester unsaturation was modified with three vinyl monomers and two hydroxyl terminated polybutadienes. Tensile, flexural, and puncture impact properties were examined. The three acrylate monomers were tetraethylene glycol dimethylacrylate, 1,3 butylene glycol dimethacrylate, and trimethylpropane trimethylacrylate with weight percents of 2.5, 5, 15, and 30. Two hydroxyl terminated polybutadienes with slightly different contents of hydroxyl functionality were also employed in the weight percents of 2.5, 5.0, and 10.0. Results showed that an increase in the number of crosslinks and crosslink density resulted in a deterioration in the mechanical properties. The addition of an immiscible polybutadiene polymer to the polyester resin also showed a decrease in the mechanical performance of the resulting thermoset materials.
Computational study of chaotic mixing in co‐rotating two‐tipped kneading paddles: Two‐dimensional approach
Authors: Lawal Adeniyi , Kalyon Dilhan M. , Ji Zhenghua 
Published: May 2005

AbstractThis study attempts to investigate the kinematics of the mixing occurring in the lenticular kneading disc section of the co‐rotating twin screw extruder, employing the tools of dynamics. The Eulerian velocity field distributions, generated by a two‐dimensional isothermal and creeping flow of Newtonian fluid under the periodic co‐rotation of the kneading discs, were obtained by Finite Element Method. A simple and novel particle tracking technique based on the FEM solution of the velocity field was employed to follow individual particles, and to produce the Poincare section mapping. Furthermore, fingerprints of chaotic motion were revealed essentially through the Lyapunov exponents, which were positive. The results suggest that the dynamics in the two‐dimensional kneading disc section of the twin screw extruder can be characterized as capable of imparting chaotic motion. The tools developed in this study should facilitate a better understanding of the mixing capabilities of the twin screw extrusion process.
Processing of thermotropic liquid crystalline polymers and their blends—analysis of melt‐spinning TLCP fibers
Authors: Lee Wan‐Chung , Dibenedetto Anthony T. , Gromek Jack M. , Nobile M. R. , Acierno D. 
Published: May 2005

AbstractIsothermal melt‐spinning of two thermotropic liquid crystalline polymers (TLCPs), a wholly aromatic copolyester KU‐9211 (also named K161 from Bayer AG) and an aliphatic containing TLCP, PET/PHB60 (Tennessee Eastman), was studied to analyze the effect of processing conditions on fiber properties. Fibers were melt‐spun from a capillary rheometer equipped with an isothermal chamber in which cross‐flowed air was used as the cooling medium. The processing variables studied included the extrusion temperature, the extrusion rate, the cooling conditions, and the draw ratio. As‐spun fibers were characterized by measuring storage moduli and molecular orientation parameters as a function of draw ratio under various processing conditions. Among the processing variables studied, the draw ratio was the primary factor in determining both the fiber modulus and the molecular orientation. The extrusion rate did not appear to affect the fiber properties within the range studied. The properties of K161 fibers were also dependent on the extrusion and cooling temperatures, while PET/PHB60 fibers were rather insensitive to the processing temperatures within data scatter and temperatures studied. A composite model based on a rigid‐rod rotation mechanism and the deformation of nematic domains in an elongational flow field was used to model the experimental results and was compared with other theories available. Conformance of data to the composite model was obtained by use of a single temperature dependent parameter n, suggesting that the rigid‐rod rotation mechanism could be used to predict the orientation development of TLCPs. The Halpin‐Tsai equations and the orthotropic equation for angular dependence were used to describe the elastic properties of the TLCP fibers.
Reactive processing of polymer blends: Analysis of the change in morphological and interfacial parameters with processing
Authors: Okamoto Masami , Inoue Takashi 
Published: May 2005

AbstractThe change in morphology and interface quantities have been analyzed for an immiscible polymer blend during reactive processing. A model polymer/polymer combination, hydroxy‐terminated poly(ε‐caprolactone)/liquid rubber with α, ω‐carboxy groups, was employed. The blend was subjected to light scattering measurements, ellipsometry, and gel permeation chromatography (GPC). Size reduction of the dispersed phase during processing was followed by a systematic decrease in the correlation distance ζ and an increase in the specific interfacial area Ssp, both by the Debye‐Bueche plot of light scattering profiles. Also observed was the time variation of the volume fraction of interface Vλ estimated as a product of the Ssp and the interfacial thickness by ellipsometry. The changes in ζ, Ssp, and Vλ with processing were accelerated when a coupling agent,γ‐aminopropyltriethoxysilane (APS), was added. The amount of block copolymer formed in‐situ in the APS‐loaded system was estimated by GPC with RI and UV detectors. For the size reduction kinetics in both APS‐loaded and ‐unloaded systems, Rittinger's law was found to be applicable.
Development of high performance, waterborne coatings. Part II: Factors affecting adhesion performance
Authors: Kojima Shunji , Moriga Toshinori 
Published: May 2005

AbstractA new manufacturing process for high performance, waterborne coatings for can coating application was developed, which includes emulsification of an epoxy resin with or without a hardener by incorporation of an acrylic resin. It is possible by this new process to emulsify a variety of resins with minimum effects of the surfactant. (acrylic resin). The effects of surfactant and neutralizer on adhesion performance were studied. It was found that the effects of the acrylic resin amount were relatively small, and that the effects of the neutralizer were significant. It was confirmed that the usage of ammonia or amines with a branched alkyl group is required to achieve balanced dry and wet adhesion.
Development of high performance, waterborne coatings. Part III: Characterization of coatings and cured film
Authors: Kojima Shunji , Moriga Toshinori 
Published: May 2005

AbstractHigh performance waterborne coatings were developed which could be utilized as an adhesive primer for sideseam bonded cans. The manufacturing process is unique; blending an epoxy / phenolic solution and an acrylic resin solution and dispersing the mixture in an aqueous medium by the phase transition method. The epoxy resins are neither chemically modified by grafting nor esterified by acrylic resin, which is thought to develop the excellent performance of epoxy / phenolic coatings. The morphology of the coatings and cured film was characterized and found to be quite different from the conventional waterborne coatings, i.e., the acrylic‐modified epoxy resin systems. It was confirmed that acrylics and epoxy / phenolic resins exist in separate phases in the cured film, and that the epoxy / phenolic resin constitutes the continuous phase.
Instrumented charpy impact test of epoxy resin filled with irregular‐shaped silica particles
Authors: Nakamura Yoshinobu , Yamaguchi Miho , Okubo Masayoshi 
Published: May 2005

AbstractThe effect of particle size on the impact properties of an epoxy resin has been studied. This resin was filled with irregular‐shaped silica particles prepared by crushing fused natural raw quartz. These particles were sorted into six groups of different mean sizes ranging from 2 to 47 μm. The impact properties were measured by an instrumented Charpy type impact tested, which can record a load‐displacement curve during impact fracture. The impact absorbed energy (U) was measured using specimens having a U‐shaped blunt notch, and the impact fracture toughness (KCI) was measured using specimens having a sharp crack introduced by a fresh razor blade. As the particle size decreased. U increased and KCI decreased. The fractured surfaces and crack tip regions were observed using a scanning electron microscope to clarify the above phenomena.
The effect of processing on rheological and molecular characteristics of a low density polyethylene
Authors: Baker W. E. , Rudin A. , Schreiber H. P. , El‐Kindi M. 
Published: May 2005

AbstractThe viscoelastic responses of some molten polymers, and particularly of low density polyethylene (LDPE), are known to vary with processing history. Reasons for the variations include the effects of shear history on morphological states of the polymer, or on its molecular weight parameters. A typical low density polyethylene has been used to test the shear‐history dependence concept following a variety of processing steps. The polymer was sheared in single‐screw and twin‐screw extruders, and in a high speed melter / mixer (Gelimat). Samples also were precipitated from very dilute solutions in trichlorobenzene and in p‐xylene. GPC analyses showed that, in general, these procedures did not affect the various moments of molecular weight. An exception was the Gelimat‐mixed sample, for which mild reductions in Mn and Mw were noted. In contrast, melt viscosity and elasticity readings, the former from low shear evaluations and the latter from extrudate swelling, were affected by the various procedures. A drop in melt viscosity and in elasticity was observed, being most pronounced for precipitated and twin‐screw extruded versions of the LDPE. Reductions also were observed in the specimen sheared in the Gelimat instrument. Following conditioning at the test extrusion temperature (170°C), viscous and elastic responses tended to revert to those of the unsheared control sample, the exception again being the sample sheared in the Gelimat melter / mixer. Of the various mechanisms proposed in the literature to account for transient property changes such as those reported, temporary changes in the degree of chain entanglement appear the most satisfactory explanation. Irreversible alterations in viscoelastic properties may be associated with changes in molecular weights due to processing at high shear.