bluuebunny/crossref_metadata_2025_split huggingface dataset:
A systematic approach for the design of a spiral mandrel die
Authors: Huang Chung‐Ching 
Published: April 2004

AbstractAn effective design strategy is presented for the determination of optimal flow channel geometry of a spiral mandrel die, which can produce annular, thin, and uniform products of polymer melt. This strategy includes two steps: First, a two‐dimensional flow simulation associated with the Taguchi approach is applied to search several sets of die geometric parameters, from which process the flow uniformity is assessed. Second, the optimum one parameter set selected by further considering total pressure drop, mixing degree and residence time distribution (RTD). The strategy is illustrated through the design of a spiral mandrel die with four spirals traveling a full 360°, and the viscosity of polymer melt is assumed to be power law model. The results indicated that the design criteria such as high flow uniformity, low pressure drop, good mixing degree and narrow RTD are difficult to attain simultaneously. For a particular polymer melt, there exists a design window for the geometric parameters; within the window the geometric parameter set may satisfy most of the design criteria.
Shear viscosity of rubber modified thermoplastics: Dynamically vulcanized thermoplastic elastomers and ABS resins at very low stress
Authors: Araki Takumi , White James L. 
Published: April 2004

AbstractThe shear viscosity of PP‐EPDM dynamically vulcanized thermoplastic elastomers and ABS resins were investigated using (a) a constant shear stress creep instrument, (b) a rotational rheometer, and (c) a capillary extrusion rheometer. It was found that stresses exist for some of these materials below which they exhibit only finite deformations. This indicates they exhibit yield values. Much attention was given to measurements of creep at low stresses especially in the neighborhood of yield values. The magnitudes of the yield stresses obtained from these low stress measurements are significantly lower than those obtained using standard extrapolation to zero shear rate of higher stresses from rotational instruments. We also observed a high shear viscosity (∼109 PA s) plateau in the materials of high rubber content. We contrasted our results to those found in the literature.
A multiscale model for polymer crystallization. I: Growth of individual spherulites
Authors: Swaminarayan Sriram , Charbon Christian 
Published: April 2004

AbstractIn this two‐part paper, we present a model for the solidification of semicrystalline thermoplastic polymers that links the microscopic and macroscopic length scales. The model accounts for the important physical phenomena occurring during spherulitic cyrstallization and predicts microstructural evolution. In this first part, we concentrate on the growth of individual spherulites. We present a fast and accurate model that predicts the shape of a spherulite as well as the path of its constitutive lamellae in any thermal situation. In part II of this paper we shall couple this new model for spherulite growth with a nucleation law and a macroscopic heat flow computation, thus enabling us to model realistic crystallization conditions.
Stress monitoring in thin polymer coatings using time resolved fluorescence
Authors: Shiga Tohru , Narita Takeshi , Ikawa Taiji , Okada Akane 
Published: April 2004

AbstractStress monitoring in thin polymer coatings was monitored using time resolved fluorescence from organic molecules. The decay time of fluorescence from an organic molecule in a uniaxially stretched polymer coating decreases with increasing tensile stress. The substance 9‐methylanthracene (9‐MeAn) is an effective dye for detecting internal stresses up to 10 MPa. Compared with the traditional bimetallic method, time resolved fluorescence of 9‐MeAn gave reliable values for internal stresses in a thin polymer coating. The internal stress in a polymer coating cured on a glass plate was measured during exposure to an outdoor weathering test. The internal stress diminished significantly in three days. The decrease in the internal stress was caused mainly by light irradiation. Because 9‐MeAn degraded in sunlight, it was a useful probe for stress monitoring only for periods less than two weeks.
Radiation effects of low refractive index, fluorinated methacrylate polymers for fiber cladding
Authors: Bertolucci P. R. H. , Harmon J. P. , Biagtan E. , Schueneman G. , Goldberg E. , Schuman P. , Schuman W. 
Published: April 2004

AbstractThe gamma radiation stability, optical properties, and mechanical properties of 1H, 1H, 3H‐hexafluorobutyl and 1H, 1H‐heptafluorobutyl methacrylate homopolymers and copolymers were determined and compared to poly(methyl methacrylate), PMMA. The aim of this study was to identify polymers for fiber cladding materials that exhibit improved optical radiation resistance and physical properties. Using 60Co source, the samples absorbed 10 Mrads of gamma radiation at 0.04 Mrads/hr in an air environment. UV/Vis transmission spectra were obtained before irradiation, just after 10 Mrads, and regularly thereafter, to track recovery in transmittance. The glass transition temperatures, decomposition temperatures, refractive indices and flexural moduli were also obtained. Poly(heptafluorobutyl methacrylate) exhibited the greatest resistance to radiation induced discoloration and the lowest refractive index of the compositions tested. As the composition of the copolymers increased in hexafluorobutyl methacrylate concentration, both the radiation induced discoloration and the refractive index increased.
Effect of particle morphology on the emulsion stability and mechanical performance of polyolefin modified asphalts
Authors: Sabbagh Amiel B. , Lesser Alan J. 
Published: April 2004

AbstractRecent federal regulations concenrning roadbed performance have motivated research in polymer modified asphalt binders. Earlier studies on these binders have shown that many of them are susceptible to gross phase separation when the binder is stored at high temperatures under quiescent conditions. This phase separation, in turn, is affected by the initial morphology and storage conditions. In this effort we investigate the effect of particle morphology on the high‐temperature emulsion stability of a low‐density polyethylene‐modified asphalt binder, as well as the concomitant effects on the mechanical behavior. We show for unstabilized emulsions that the dominant phase separation mechanism shifts from coalescence to creaming at a critical particle radius of 4 μm at 110°C. However, stabilized emulsions showed no evidence of gross phase separation for up to 48 hours at 110°C. Dramatically different morphologies were observed for the unstabilized and stabilized emulsions; unstabilized emulsions having teardrop shaped particles and stabilized emulsions having both spherical particles and long cylindrical domains. The mechanical behavior, including the high‐temperature dynamic viscoelastic behavior and low‐temperature fracture toughness, increased with polyolefin content, but was insensitive to the particle morphology.
Melting model for modular self wiping co‐rotating twin screw extruders
Authors: Bawiskar Santosh , White James L. 
Published: April 2004

AbstractA model for the melting process in a self wiping co‐rotating twin screw extruder is described. Self‐wiping co‐rotating twin screw extruders are modular and starve fed. This leads to melting mechanisms that are different from single screw extruders. The melting process in the modular screw configurations generally occurs in specialized sections such as kneading disk blocks. The model, based on our previous experimental observations, considers the formation of two stratified layers of melt in contact with the hot barrel and solid pellets in contact with the relatively colder screw. In the kneading disk blocks, a part of the solid bed is blocked because of the relative stagger between successive disks. The model predicts both the location of melting and melting lengths in a screw configuration. Calculations for individual screw elements and kneading disc elements are presented first. Melting in a modular configuration of these elements is then considered. The effect of operating variables such as mass flow rate and screw speed on melting is then studied. The model is put in a dimensionless form and the effect of various dimensionless groups is discussed. We make a comparison to the experiment and agreement is good.
Electrocapillary wave studies of different poly(dimethyl siloxane)s
Authors: Seo Yongsok , Skarlupka Randy , Yu Hyuk 
Published: April 2004

AbstractThe monolayer behavior of different end‐functionalized poly(dimethyl siloxane)s (PDMSs) and a block copolymer, poly(dimethyl siloxane‐co‐ethylene oxide) (PDMS‐co‐EO) spread on an oligomeric poly(ethylene glycol) (PEG) substrates, were studied by means of electrocapillary wave diffraction (ECWD). Over a relatively small temperature range (40–70°C), the damping constant was more dependent on temperature than on the wave vector. Different surface layer properties were observed for two PDMS: one terminated with a methyl group (PDMS‐CH3) and the one terminated with a hydroxy group (PDMS‐OH). PDMS‐OH showed a larger reduction in surface tension compared to PDMS‐CH3 because of a higher interfacial affinity with PEG, which indicated that its monolayer surface activity was weaker. A lower surface elasticity of PDMS‐OH than that of PDMS‐CH3 supported that conclusion. The block copolymer showed no surface activity, since the short siloxane moiety did not repel the strong interaction between PEG and the ethylene oxide.
Effect of surface properties on the adhesion between PVC and wood veneer laminates
Authors: Matuana Laurent M. , Balatinecz John J. , Park Chul B. 
Published: April 2004

AbstractThe interface between plastic and wood fibers strongly influences the mechanical properties of a plastic/wood‐fiber composite. This paper presents a means for evaluating the effectiveness of surface treatment on the wood‐fibers in the PVC/wood‐fiber composites by investigating the adhesion between PVC and laminated wood veneers. Wood veneers were first treated with γ‐aminopropyltriethoxysilane, dichlorodiethylsilane, phthalic anhydride, and maleated polypropylene for surface modification. The chemical modification made on the wood surfaces was then characterized using different complementary surface analytical techniques: X‐ray photoelectron spectroscopy and surface tension measurements. The surface tension was determined from the equation of state for interfacial tensions and the measured contact angles of glycerol sessile drops on the wood veneers (both untreated and treated) and on PVC using the Axisymmetric Drop Shape Analysis–Contact Diameter (ADSA‐CD) approach. The adhesion property was evaluated by measuring the tensile shear strength of single lap joints between two wood veneers bonded with a PVC film. The adhesion between PVC and wood veneer laminates was significantly improved when wood veneers were treated with amino‐silane, while no improvement was observed for the other adhesion promoters. Our experimental results indicate that matching the surface tension is not sufficient to ensure good adhesion between PVC and wood veneers.
Simple formulae for the effective moduli of unidirectional aligned composites
Authors: Hui C. Y. , Shia David 
Published: April 2004

AbstractSimple closed form expressions for the effective tensile moduli of an unidirectionally aligned two phase composite reinforced by fiber‐like or flake‐like inclusions of aspect ratio α are obtained. The case of α ≫ 1 corresponds to fiber‐like inclusions whereas the case of α ≪ 1 corresponds to flake‐like inclusions. These expressions are based on the exact results obtained by Tandon and Weng, who used the Mori‐Tanaka method to obtain the effective moduli of such composites. These expressions are then compared with various empirically based formulae such as the Halpin‐Tsai equation and the Modified Rule of Mixtures equation. It is found that very large discrepancies result when the modulus ratio E0/E1 is sufficiently small compared with the aspect ratio of the flake‐like inclusions, where E1 and E0 are the Young's modulus of the inclusions and the matrix, respectively. Simple criteria for the validity of the rule of mixtures relation are also given. Also, the predictions of the simple closed form expressions are compared to available experimental results and favorable agreements are obtained.
Homogeneous and heterogeneous sulfonation of polymers: A review
Authors: Kučera F. , Jančář J. 
Published: April 2004

AbstractThis paper reviews the various reactions used to sulfonate polymers, especially polystyrene. The mechanisms for the sulfonation of low molar mass compounds are also discussed. The commonly used sulfonation reagents are described, with an emphasis on SO3and its physical and chemical properties. Polymer sulfonations can be grouped into two general routes: one involving homogeneous sulfonation and the other heterogeneous reactions.
Effect of processing conditions on shrinkage in injection molding
Authors: Jansen K. M. B. , Van Dijk D. J. , Husselman M. H. 
Published: April 2004

AbstractA systematic study on the effect of processing conditions on mold shrinkage was undertaken for seven common thermoplastic polymers. It turned out that the holding pressure was always the key parameter. The effect of the melt temperature is slightly less important. Injection velocity and mold temperature do not show a general trend for all polymers. It was shown that at least for amorphous polymers a simple thermoelastic model could describe all experimental results. For semi‐crystalline materials the model overpredicts shrinkage.
Kinetics of forming poly(butylene succinate) (PBS) oligomer in the presence of MBTO catalyst
Authors: Park Sang Soon , Jun Ho Wook , Im Seung Soon 
Published: April 2004

AbstractThe direct‐esterification reaction of succinic acid (SA) with 1,4‐butanediol (BD) was investigated in the temperature range from 170°C to 190°C with and without a monobutyl tinoxide (MBTO) catalyst. The extent of reaction was measured by the quantity of water distilled from the reaction. The effects of reaction temperature, molar ratio of SA and BD, and MBTO concentration on the kinetics were studied. The experimental kinetics results for uncatalyzed reactions agreed quite well with the Flory model. A new complex model was developed for the MBTO catalyzed reaction, and the experimental results showed good agreement with the complex model.
Preparation and characterization of LDPE/starch blends containing ethylene/vinyl acetate copolymer as compatibilizer
Authors: Prinos J. , Bikiaris D. , Theologidis S. , Panayiotou C. 
Published: April 2004

AbstractA series of LDPE blends with plasticized (PLST) and granular starch (FILST) were prepared. Ethylene/vinyl acetate (EVA) copolymer was used as a compatibilizer in three different amounts: 10, 25 and 50 wt% based on starch. The blends were studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Second derivative IR spectra showed peak shifts similar to those observed in V‐type starch complexes with ethylene/vinyl alcohol copolymers. The possibility for V‐type complex formation is supported by the lower biodegradation rates of the blends containing higher amounts of EVA. Mechanical properties of the blends, especially elongation at break, were satisfactory even for blends containing high amounts of starch (20–30 wt%).
Mechanism of corona treatment on polyolefin films
Authors: Zhang Dong , Sun Qin , Wadsworth Larry C. 
Published: April 2004

AbstractThis paper reviews recent studies on the mechanism of corona treatment of polyolefin films, specifically the chemical and physical changes of this process and the self‐adhesion mechanism. Corona discharge of polymeric films introduces polar groups into the surfaces, which increases the surface energy and, as a consequence, improves substrate wettability and adhesion. The main chemical mechanism of corona treatment is oxidation. In addition, corona treatment can crosslink surface regions and increase the film cohesive strength.
The cause of the grey discoloration of PET prepared by the use of antimony‐catalysts
Authors: Aharoni Shaul M. 
Published: April 2004

AbstractHeating three antimony catalysts with several glycols and other model compounds in open and sealed vessels with various degrees of oxygen availability was followed by analyses of the volatile products in the head‐space and of the nonvolatile products. Bis(hydroxyethylene terephthalate)(Bis‐HET) and terephthalic acid (TA) plus ethylene glycol (EG) were separately polymerized to poly(ethylene terephthalate)(PET) and TA plus triethylene glycol (TEG) was polymerized to poly(triethyleneglycol terephthalate) (PTEGT). Analyses of the polymers and of the model compounds revealed that: (1) Free glycols or the glycolate moieties in polyesters degrade upon heating in the presence of oxygen to produce equal amounts of CO and CO2. (2) In the presence of Sb(III) species, the CO oxidizes to CO2 at elevated temperatures with the concomitant reduction of Sb(III) to very fine black particles of the elemental Sb(O). This is the cause for the grey discoloration of PET made with Sb‐catalysts. The redox reaction starts at about 200°C and is fully dominant at about 235°C and above. (3) At temperatures lower than ˜200°C, the Sb(III) usually converts to the white Sb2O3 and the CO does not oxidize the CO2.
An experimental comparison of cooling time for cylindrical plastic components using heat conduction models in the non‐conservative and conservative forms
Authors: Dubay Rickey , Bell Adam C. 
Published: April 2004

AbstractIn the manufacture of plastic components, predicting cooling duration and temperature distribution are critical for maintaining optimum productivity costs and part quality. We investigated the cooling cycle of injection molding for cylindrical shaped plastic components. A numerical model was formulated using the full conservative form of the energy equation with temperature dependent polymer properties having continuous equations of state. The cooling time predictions from this numerical method were in good agreement with our experimental results. This model predicted shorter cooling times than the often used non‐conservative heat conduction model that uses constant polymer properties or a temperature dependent thermal diffusivity. Good agreement in cooling time was obtained using the model of Ballman and Shusman and the conservative model for part thicknesses #3 mm. The investigation indicated that the statistical cooling time model of Busch et al. is more suitable for predicting plastic part cooling.
An experimental study on the effect of polymer viscoelasticity on layer rearrangement in coextruded structures
Authors: Dooley Joseph , Hyun Kun Sup , Hughes Kevin 
Published: April 2004

AbstractPrevious work on the layer thickness uniformity of coextruded structures has centered primarily on the effects of differing polymer viscosities in the individual layers. These differences in viscosities result in a phenomenon known as “viscous encapsulation” in which the less viscous layer tends to encapsulate the more viscous layer producing nonuniform layer thicknesses. In this study, the effect of polymer viscoelasticity on the layer thickness uniformity of multilayer coextruded structures was investigated by coextruding multilayer structures through die channels of different cross‐sectional shapes and observing the location of the interface. In order to minimize the viscosity effects, the coextrusion experiments were conducted with identical materials in each layer that were pigmented to allow observation of the layer interface. It was shown experimentally that coextruding identical polymers through channels of various geometries can cause the layers to rearrange. This layer rearrangement appears to be caused by secondary flows that occur in different channel geometries due to the viscoelastic characteristics of the polymer. Layer rearrangement of identical polymers implies that even resins with viscosities well matched for coextrusion may experience nonuniform layer thicknesses when coextruded through large dies.
Modeling warpage in reinforced polymer disks
Authors: Fahy E. J. 
Published: April 2004

AbstractA circular disk mold is sometimes employed to test how a reinforced polymer will induce part warpage or distortion after removal from an injection mold. These polymer disks are modeled by developing an analogy to axially symmetric disks that have the reinforcement either in the disk radial or tangential direction and warp to a cup or saddle shaped disk during cooling. The governing mechanisms causing warpage are discussed with analytical and numerical models employed to quantify the impact of in‐plane thermal anisotropy on warpage. The cup and saddle warpage formulae that are derived can guide the engineer on estimating the underlying polymer properties as well as evaluating the impact of part design on thermal warpage.
Numerical simulation of multi‐layer flow for polymer melts—A study of the effect of viscoelasticity on interface shape of polymers within dies
Authors: Matsunaga K. , Funatsu K. , Kajiwara T. 
Published: April 2004

AbstractA two‐dimensional simulation was developed for multi‐layer confluent viscoelastic flow in dies, using a finite element method. The simulated interface shape was compared with the experimental results of previous researchers, and the simulated results were confirmed. Two‐layer and three‐layer flows of two or three kinds of viscoelastic fluids were simulated. Fluids with different non‐Newtonian viscosities and the first normal stress differences were used. The layer thicknesses in dies are mainly determined by the shear viscosity and less by the elasticity of the fluid. The normal stress difference between the fluids forming an interface may be related to interfacial instability, and normal stresses near the interface were examined. The normal stress difference between both fluids was affected by the first normal stress difference and elongational viscosity.
Extrusion of PE/PS blends with supercritical carbon dioxide
Authors: Lee Minhee , Tzoganakis Costas , Park Chul B. 
Published: April 2004

AbstractThe effects of dissolved supercritical carbon dioxide on the viscosity and morphological properties were investigated for polyethylene/polystyrene blends in a twin‐screw extruder. The viscosities of the blend/CO2 solutions were measured using a wedge die mounted on the extruder. A considerable reduction of viscosity was found when CO2 was dissolved in the blend. It was observed that the dissolution of CO2 into PE/PS blends, regardless of the CO2 content used, led to decreased shear thinning behavior resulting in an increase of the power law index from 0.29 to 0.34. The cell structures of foamed PE/PS blends showed a typical dependence of pressure and CO2 concentration, with higher operating pressures and CO2 content leading to a smaller cell size. Also, it was noted that the size of the dispersed PS phase in the PE/PS phase blends decreased by increasing the CO2 concentration, and that the dispersed PS phase domains were highly elongated in the direction normal to the cell radius.