bluuebunny/crossref_metadata_2025_split huggingface dataset:
A theoretical analysis of the strength of composite gels with rigid filler particles
Authors: Gao Y. C. , Lelievre J. 
Published: May 2005

AbstractThe strength, under uniaxial load, of composite gels containing filler particles has been investigated by calculating the stress concentration in the gel matrix. The particles were assumed to be rigid spheres, and the interaction between the particles was taken into account based on a self‐consistent model. The bonding between the particles and matrix was treated for two typical cases, (1) perfectly bonded, (2) smoothly connected. For case 1, the analytical result shows that the stress concentration factors decrease with the increasing of the volume fraction of filler. For case 2, the stress concentration factors are independent of the volume fraction of filler. The structural failure caused by the stress concentration was analyzed.
Merits and limitations of the drop and shock tests in evaluating the dynamic properties of plastic foams
Authors: Ramon O. , Mizrahi S. , Miltz J. 
Published: May 2005

AbstractCushioning curves for different plastic foams were determined using drop and shock tests. It was found that at intermediate static stresses the two methods give comparable results. At low and very high static stresses however, different results were obtained. An explanation was given why the shock test is more appropriate and reliable at low and the drop test at very high static stresses.
Water soluble copolymers. 54: N‐isopropylacrylamide‐co‐acrylamide copolymers in drag reduction: Synthesis, characterization, and dilute solution behavior
Authors: Mumick Pavneet S. , McCormick Charles L. 
Published: May 2005

AbstractCopolymers of N‐isopropylacrylamide (IPAM) and acrylamide (AM) have been synthesized by free radical polymerization in deionized water using potassium persulfate as the initiator. Copolymer compositions were obtained by elemental analysis and 13C NMR. An r1r2 value of 0.99 indicates ideal copolymerization with random incorporation of the comonomers in the copolymers. Weight average molecular weights, second virial coefficients, diffusion coefficients, and average diameters were obtained via classical and quasielastic low angle laser light scattering. The molecular weights for all the copolymers and the homopolymers of IPAM and AM ranged from 2.2 × 106 to 5.2 × 106 g/mol. The second virial coefficients in deionized water increased with increasing acrylamide content in the copolymers. The dilute solution properties of the copolymers were studied by turbidimetry, microcalorimetry and viscometry. All the copolymers, with the exception of IPAM‐40 (the copolymer synthesized with 40 mole% IPAM in the feed), showed lower critical solution temperatures below 100°C. The solution studies were performed in deionized water, 0.514 M NaCl, and 1 M urea. The properties of the IPAM copolymers were influenced by both hydrophobic associations and hydrogen bonding. In 0.2% (∼7mM) sodium dodecyl sulfate, the alkyl chain of the surfactant molecules associates with the IPAM moieties on the copolymer backbone, leading to high intrinsic viscosities and the elevation of the LCST above 100°C.
The onset of wall slip and sharkskin melt fracture in capillary flow
Authors: Hatzikiriakos Savvas G. 
Published: May 2005

AbstractThe capillary die flow of high density and linear low density polyethylenes is simulated under slip conditions to investigate the origin of sharkskin melt fracture. As suggested in the literature, it is shown that sharkskin originates at the exit of the die and is due to the acceleration (high stretching rate) of the melt as it exits the die. It is also shown that both adhesion and slip promoters eliminate surface defects by decreasing the stretching rate of the polymer melt at the exit region of the die. The effect of length‐to‐diameter ratio of the die on the sharkskin melt fracture is also examined. It is found that sharkskin is more pronounced in short dies which is in accord with experimental observations. Finally, it is suggested that applied pressure at the capillary exit suppresses surface defects.
Effect of moisture absorption on the tensile properties of short glass fiber reinforced poly(butylene terephthalate)
Authors: Ishak Z. A. Mohd , Lim N. C. 
Published: May 2005

AbstractInjection molded short glass fiber reinforced poly(butylene terephthalate) was subjected to hygrothermal aging at two different relative humidities—81.2% and 100% RH. A single free phase model of diffusion has been used to analyze the data obtained from the kinetics of moisture absorption study. The diffusion coefficient and the equilibrium moisture content were found to be dependent on the volume fraction of fibers and relative humidity. Incorporation of short glass fibers into a poly(butylene terephthalate) matrix has led to a significant improvement in the retention and recoverability of the tensile properties. Examination of fracture surfaces using a scanning electron microscope (SEM) has revealed some evidence for the hydrolysis of the polymer matrix. The hydrolysis resulted in the formation of microvoids, the absence of a plastic deformation process, and degradation at the fiber‐matrix interface.
Morphology and properties of an epoxy alloy system containing thermoplastics and a reactive rubber
Authors: Woo E. M. , Bravenec L. D. , Seferis J. C. 
Published: May 2005

AbstractA novel approach for toughening thermosetting epoxy matrices using both thermoplastics and liquid reactive rubbers as modifiers has been investigated. The network structure of the modified epoxy systems was characterized using dynamic mechanical analysis, and the morphology of the multiphase structure was examined using scanning electron microscopy (SEM). To investigate the continuity of the phase domains, the constituents in the phase domains were positively identified using solving etching and RuO4 staining techniques for transmission electron microscopy (TEM). The fracture toughness of the modified and basic epoxy samples was measured using compact tension (CT) specimens. Quite limited toughness improvement was achieved for the epoxy modified with only the PSu thermoplastic, or the liquid rubber by itself. However, the fracture toughness was found to increase dramatically when a proper combination of both the liquid reactive rubber and thermoplastic was simultaneously incorporated into the epoxy. Toughening by using dual modifiers resulted in maximum improvement of fracture toughness with minimal compromises in processability and Tg depression by rubbers.
In‐line monitoring of titanium dioxide content in poly(ethylene terephthalate) extrusion
Authors: Batra Jitender , Khettry Atul , Hansen Marion G. 
Published: May 2005

AbstractPeak absorbance changes correlated to changes in species concentration have been the norm in applied spectroscopy, while baseline shifts have been more of an inconvenience. Taking the first or second derivative of the spectra eliminates these baseline shifts. However, with multivariate techniques becoming more readily available, repeatable baseline changes may now be monitored and correlated to specific physical changes. This concept has been studied by monitoring the concentration of titanium dioxide (TiO2), a white inorganic filler, in molten poly(ethylene terepthalate) (PET). Various mixtures of filled and unfilled PET resins were run through a single‐screw extruder, and near infrared spectra were collected in‐line by using a flow cell, housing two fiber‐optic probes, and mounted downstream of the extruder. The presence of titanium dioxide caused the scattering of light that resulted in a systematic baseline shift. The baseline shifts were correlated to the TiO2 concentration data. Multivariate techniques involving the use of singular value decomposition (SVD) to perform partial least squares regression (PLS) were applied to quantitatively determine TiO2 content in the PET melt stream. Standard error of prediction (SEP) values of about 1% were obtained for a model based on two factors.
Phase stability of ternary blends
Authors: Kim C. K. , Kim Jae‐Jin , Paul D. R. 
Published: May 2005

AbstractThe phase behavior of ternary blends of tetramethyl polycarbonate (TMPC), polycarbonate (PC), and styrenic polymers has been examined by experiment and analyzed in terms of thermodynamic theories. The phase boundaries were predicted using both the modified Flory‐Huggins theory and the lattice fluid theory. The boundaries predicted using the lattice fluid theory agree best with the experimental results. The experimental phase behavior of ternary blends was compared with binary blends having exactly the same chemical components and compositions except that the TMPC and PC units were present in the form of a copolycarbonate in the binary. The miscible region of these ternary blends is much narrower than that of the corresponding binary blends, even though the entropic and energetic terms of such ternary blends are more favorable than those of the binary blends. It is shown that a negative value of noncombinatorial free energy in multicomponent systems is not a sufficient condition for miscibility, because of asymmetries of mer‐mer interactions. A comparison of the stability conditions for these binary and ternary blends shows that increasing the degrees of freedom tends to destabilize the mixture.
On the significance of the standardized notched impact strength for materials selection and design
Authors: Jancar J. , Dibenedetto A. T. 
Published: May 2005

AbstractExperimental data on the standard Charpy notched impact strength (CNIS) for a large sampling of particulate‐filled and rubber‐modified polypropylenes were analyzed. To determine the significance of the CNIS for material selection and design, CNIS data were compared with fracture toughness measurements expressed as the critical strain energy release rateG′c, measured under impact loading. A scale factor representing the state of stress at the crack tip was calculated, assuming small scale yielding, Class I linear elastic fracture mechanics (LEFM). Based on the data, three principal groups of materials were identified. In the smallest of the three, CNIS andG′cmeasurements showed the same functional dependence on the material variables studied and were characterized by a scale factor independent of the composition. In these cases, one can justify comparisons of toughness of different compositions using single values of the CNIS, since the materials are probably being compared in equivalent states of stress. In a second group, CNIS andG′calso show the same functional dependence on material variables, but exhibit large variations in the scale factor with composition. One should not compare the toughness of different materials from this group based on single values of CNIS, since it is likely that the comparisons would not be made relative to equivalent states of stress. In these cases, only measurements ofG′ccan separate the effect of specimen geometry from those of the intrinsic properties of the material. The majority of materials studied fell into a third group, in which the CNIS andG′cexhibited substantially different functional dependencies on the material properties, and the scale factors depended also on composition. In these latter cases, a comparison of CNIS values for different compositions is not a reliable indication of the relative toughness and is of little value as a parameter for material selection and design.
Interfacial tension in polymer melts. I: An improved pendant drop apparatus
Authors: Demarquette N. R. , Kamal M. R. 
Published: May 2005

AbstractAn apparatus is described to measure interfacial tension for molten polymer pairs. The apparatus is based on the pendant drop method. A CCD color video camera captures the image of a pendant drop profile, which is analyzed on‐line using a microcomputer. These almost continuous measurements permit the detection of possible changes in the behavior of the melt that might affect the interfacial tension through thermal degradation. A special syringe to inject the pendant drop has been designed in order to avoid problems such as the capillary effect of the tube of the syringe and the necking and detachment of the pendant drop. The accuracy of the apparatus was verified using water/n‐hexane and water/n‐octane. Experimental results for polypropylene/polystyrene (PP/PS) are presented. The interfacial tension between the polymer pair decreases as temperature increases and as molecular weight decreases. Interfacial tension is estimated from the drop shape when the drop is at mechanical equilibrium. For polymer systems, mechanical equilibrium normally takes from 1 to 10 h to occur. However, transient values of interfacial tension (apparent interfacial tension values obtained before mechanical equilibrium is reached) may be used to estimate the interfacial tension at equilibrium by extrapolation, thus reducing the required experimental time.
Quiescent nonisothermal crystallization kinetics of isotactic polypropylenes
Authors: Hammami Ahmed , Spruiell Joseph E. , Mehrotra Anil K. 
Published: May 2005

AbstractRecently, a model was developed for the nonisothermal crystallization of normal alkanes with chain lengths between 30 and 50. The model was derived based on the fundamental equation of Ozawa for nonisothermal crystallization, the surface nucleation theory, and the growth rate theory for extended chain crystals. In this paper, the proposed model is modified and extended to the case of polymer crystallization. Experimental differential scanning calorimetry data for three isotactic polypropylene resins with different molecular weights are presented at five cooling rates from 2 to 40 K/min. Model predictions are in excellent agreement with the experimental data for the three polymers at low and high supercoolings.
Dilatometric study of low profile unsaturated polyester resins
Authors: Kinkelaar Mark , Muzumdar Shailesh , Lee L. James 
Published: May 2005

AbstractAn in‐house‐built and designed dilatometer was applied to the study of low profile unsaturated polyester resins. This article first describes the dilatometer used including its calibration then its application to low profile unsaturated polyester resins. Several series of dilatometry experiments were performed, to study the effect of low profile additive concentration and cure temperature on shrinkage control. Scanning electron micro‐graphs of the samples were also prepared to show the correlation between shrinkage control and polymer morphology.
Fiber structure development in high‐speed melt spinning of copolyesters: Poly(ethylene terephthalate‐co‐ 1,4‐cyclohexylene dimethylene terephthalate)
Authors: Kikutani Takeshi , Morohoshi Katsumi , Yoo Hee Yeoul , Umemoto Susumu , Okui Norimasa 
Published: May 2005

AbstractHigh‐speed melt spinning of poly(ethylene terephthalate) (PET), poly(1,4‐cyclohexylene dimethylene terephthalate) (PCT) and ET/CT copolysters were performed and the structure and properties of as‐spun fibers were investigated. Molecular orientation increased with an increase in the take‐up velocity, and orientation‐induced crystallization of PET and PCT started at ∼4.5 and 3.5 km/min. With the addition of CT component to PET, and ET to PCT, the onset of crystallization shifted to higher velocities. In as‐spun fibers of the copolymer of ET/CT = 66/34 mol%, which is known as an amorphous copolyester, the crystallization was not observed even at the attained highest take‐up velocity, 6 km/min. On the other hand, crystallization of these fibers occured on annealing suggesting that although the incorporation of copolymer component suppresses the crystallization, the molecular orientation enhances the crystallization of copolymer systems as in the cases of homopolymers.
An overview of the basic aspects of polymer adhesion. Part I: Fundamentals
Authors: Fourche Georges 
Published: May 2005

AbstractAdhesion between two substrates is a complex phenomenon which at present is still not well understood. The important existing adhesion models (electrical, diffusion, thermodynamic adsorption, chemical, etc.) are reviewed in order to try to explain their mechanisms. Thermodynamic adsorption is now believed to be one of the most importnat mechanisms by which adhesion is achieved. Difusion and wetting are kinetic means in attaining good adsorption of a polymer at the interface. In the case of this model (thermodynamic adsorption), the notion of surface energy is developed and the importance of this property in the understanding of adhesion phenomena is emphasized. The methods of determining the surface characteristics of low and high energy solids are presented. The role played by acid‐base interactions in adhesion is also mentioned.
Indentification of plastic waste using spectroscopy and neural networks
Authors: Scott D. M. , Waterland R. L. 
Published: May 2005

AbstractIn this paper we investigate a new approach for the automated sorting of post‐consumer plastic waste. We show that rapid and relible identification of polymers can eb achieved using a combination of fixed‐filter near‐infrared spectroscopy and neural network data analysis, and we demonstrate the effectiveness of the proposed method for sorting polyethylene terephthalate, high density polyethylene, and poly(vinyl chloride). Finally, we discuss a proposed compact, rugged instrument based on the new sorting method. Owing to the flexibility gained by incorporating neural networds in our system, thismethod can easily be extended to include additional polymers.
Elongational, hysteresis, and oscillatory flows of complex fluids
Authors: De Kee D. , Fong C. F. Chan Man 
Published: May 2005

AbstractThe simple model proposed earlier to describe te rheological properties of complex fluids is used to calculate (a) the extensional viscosity, (b) the hysteresis loops, and (c) the complex viscosity. It has been found that the rheological properties predicted by the model agree with experimental observations. It is shown that for some viscoelastic fluids the extensional viscosity is always finite and for some other fluids the extensional viscosity tends t infinity at finite extensional rate. In the latter case, steady flow is not attainable. The shape of the hysteresis loops depends on the maximum shear‐rate. It also depends on the material properties. In a small amplitude oscillatory flow, our model reduces t a linear viscoelastic fluid.
Double yield points in poly(tetramethylene terephthalate) and its copolymers under tensile loading
Authors: Muramatsu Shigeru , Lando Jerome B. 
Published: May 2005

AbstractDouble yield points before necking were observed in injection molded specimens of poly(tetramethylene terephthalate) (PTMT) and its copolymers under tensile loading. The first yield is associated with deformation of the amorphous region and the second yield is caused by the alpha to beta transition of PTMT crystallites. The first yield point became less apparent with an increase of crystallinity of the specimens. The second yield point became more apparent with an increase of crystallinity. Annealing of injection molded specimens increased the crystallinity and increased the second yield point on stress‐strain curves. Copolymerization decreased the crystallinity and made the first yield point more prominent. Effects of annealing on mechanical and thermal properties of the specimens were also measured. The specimens changed their properties from ductile to brittle during annealing. Their change during annealing was mainly attributed to the increase of crystallinity and not to thermal degradation and/or crosslinking.
Toughening of unsaturated polyester and vinyl ester resins with liquid rubbers
Authors: Ullett Jill S. , Chartoff Richard P. 
Published: May 2005

AbstractA comprehensive study of toughening unsaturated polyster and vinyl ester resins by addition of liquid rubbers was carried out by considering the effects of cure temperature and gel time on final resin/rubber morphology. The objective was to produce a dispersed rubber phase consisting of particles less than 15 μm in diameter with the addition of limited amounts of rubber, so as not to seriously reduce the modulus and strength of the base resin. A variety of liquid rubbers was used including those based on poly(butadiene acrylonitrile), poly(epichlorohydrin), and two poly(acrylates). Fracture toughness of unmodified and rubber modified materials was measured using the compact tension (CT) test geometry. Significant improvements in fracture toughness were achieved with little to no change in Young's modulus or glass transition temperature. With modest rubber additions, the fracture toughness increased up to 62% for the polyester resin and up to 116% for the vinyl ester resin. In general, fracture toughness increases with increases in volume fraction of rubbery second‐phase particles. However, results suggest that two‐phase particles may be more effective tougheners than single‐phase particles. The toughening mechanism appears to depend on the type of rubbery particle morphology present.
The double yield in the tensile deformation of the polyethylenes
Authors: Lucas J. C. , Failla M. D. , Smith F. L. , Mandelkern L. , Peacock Andrew J. 
Published: May 2005

AbstractDouble yields, as well as other complex yielding behavior, that are observed during the tensile deformation of the polyethylenes have been studied in a systematic manner. The conditions under which such yielding is observed were established by studying a set of linear polyethylenes and well‐characterized ethylene copolymers of narrow molecular weight and composition distributions. A wide range in crystallinity levels were developed and the rate of deformation and the deformation temperature were varied. These experimental results make clear why such complex yielding processes are not always observed. A qualitative explanation, based on the postulate of a partial melting‐recrystallization process during deformation, is given that encompasses all of the experimental data.
Tesile toughness of microcellular foams of polystyrene, styrene‐acrylonitrile copolymer, and polycarbonate, and the effect of dissolved gas on the tensile toughness of the same polymer matrices and microcellular foams
Authors: Collais Dimitris I. , Baird Donald G. 
Published: May 2005

AbstractThis paper reports on the tensile properties of microcellular foams of three different thermoplastics, since there have been several reports in the literature, but with indefinite conclusions so far, that microbubbles act in a manner similar to rubber particles in toughening thermoplastics. Polystyrene (PS), styreneacrylonitrile copolymer (SAN), and polycarbonate (PC), were selected based on their different intrinsic ductilities. The gas supersaturation technique was used to generate samples with microbubbles. The effect of the presence of microbubbles inside the polymer matrix was separated from the effects of the pressure and thermal history experienced by the samples. Nitrogen gas dissolved into PS, and to a lesser extent into SAN, caused and increase of the tensile toughness, but this increased decayed with time as nitrogen gas diffused out of the samples. Furthermore, microcellularly foamed PS samples showed some limited improvement in terms of tensile toughness after all the nitrogen gas diffused out. SAN and PC showed deterioration of the tensile toughness in the presence of microbubbles.