bluuebunny/crossref_metadata_2025_split huggingface dataset:
A semi‐empirical algorithm for flow balancing in multi‐cavity transfer molding
Authors: Manzione L. T. , Osinski J. S. , Poelzing G. W. , Crouthamel D. L. , Thierfelder W. G. 
Published: December 2004

AbstractMulti‐cavity transfer molding is an important process step in several electronic and photonic technologies. In some applications, uniform filling of the cavities of the mold, or mold balancing, is required. A semi‐empirical flow model to predict mold filling patterns was developed. The algorithm is a one‐dimensional network flow simulation that uses experimental pressure drop data to determine the volumetric flow rate through the gates and runners. A comprehensive experimental program was undertaken to determine these hydraulic resistances for different flow rates and mold geometries. A theoretical treatment is also described to compute hydraulic resistance from gate geometry. Uniform gate resistances provide unbalanced filling and higher velocities in the cavities. Balanced filling can significantly reduce the molding compound velocity and the flow induced stresses, but imperfect balancing compromises the benefits. Experimental filling patterns were obtained for two sets of gates. The agreement between the model and the experiments was satisfactory, and the discrepancies were attributed to correctable phenomena.
The effects of blending small amounts of homopolystyrene on the mechanical properties of a low styrene content styrene‐butadiene‐styrene block copolymer
Authors: Flosenzier Linda S. , Rohlfing John H. , Schwark Alodia M. , Torkelson John M. 
Published: December 2004

AbstractTensile, cyclic, and tear properties were compared for several styrene‐butadiene‐styrene (SBS) triblock copolymers, KRATON D2104, D1101 and D1102, and blends of D2104 with monodisperse polystyrene of various molecular weights. D2104 is expected to have a morphology of polystyrene spheres in a polybutadiene continuous matrix. The mechanical properties of D2104 were compared to the properties of SBS materials which have higher styrene contents and exhibit cylindrical or lamellar morphologies. Blending the D2104 with polystyrene (molecular weights ranging from 2000 to 51,000) to 24 and 28 wt % total styrene content showed that the tensile strength obtained for a blend was dependent on the molecular weight of the polystyrene added. Cycle testing of the D2104‐polystyrene blends showed that with increasing polystyrene content the softening effect increases with increasing strain. This indicates that the degree of phase continuity of the polystyrene domains may be changing from a spherical morphology to a cylindrical morphology similar to that of pure SBS with 28 wt % styrene content. Tear test results for the blends were also observed to be similar to the results for pure SBS of the same total polystyrene content.
Characterization of polyester/polycarbonate blends by size exclusion chromatography and melt rheometry
Authors: Miller R. L. , Brooks R. V. , Briddell J. E. 
Published: December 2004

AbstractA major obstacle to the study of polymer blends has been the lack of a convenient technique for measurement of molecular weight. Melt rheometry, while giving useful information related to processing and end‐use performance, is incapable of providing detailed information on the individual components. This work describes the use of size exclusion chromatography (SEC) to study the molecular‐weight distributions of polycarbonates and aromatic polyesters in blends of the two. SEC of the polycarbonate is achieved in a solvent which dissolves the polycarbonate, but not the polyester, while SEC is performed in a solvent which dissolves both components, but using selective detection. Thus, SEC is used to examine the individual components of the blend, while rheometry can be used to study the blend as a whole. This combination of techniques has been successfully used to analyze the effect of moisture, processing conditions, and recycling on blend properties.
On gradual dosage of the initiator in the suspension polymerization of vinyl chloride
Authors: Mrázek Zdeněk , Lukáš Rudolf , Ševčík Stanislav 
Published: December 2004

AbstractInitiator dosage in the solid phase during the suspension polymerization of vinyl chloride has been investigated with the use of a special apparatus developed for this purpose. Results arc reported on a series of polymerizations in which the initiator was divided in various ratios between the starting and additional quantities, added either in one dose or repeatedly to the reaction mixture at various reaction times. Discussed is the kinetic course of polymerization and the effect of dosage on the rate of reaction heat release. It is found for the system used that a suitable dosage regime allows the total amount of the initiator to be reduced by as much as 15 percent, while the yield and the reaction time corresponding to the standard polymerization procedure remain unchanged.
Dynamics of a cascade of two continuous stirred tank polymerization reactors with a binary initiator mixture
Authors: Kim Kee Jeong , Choi Kyu Yong , Alexander James C. 
Published: December 2004

AbstractThe dynamic behavior of two continuous stirred tank reactors in series has been investigated for free radical solution polymerization of styrene with a binary mixture of two initiators having different thermal decomposition activities. For a wide range of initiator feed composition, both reactors exhibit quite complex nonlinear steady state and transient behavior. When the reactor residence time is used as a bifurcation parameter, the second reactor can have up to five steady states. For certain range of reactor operating conditions, bifurcations to various types of periodic solutions have been observed, such as Hopf bifurcation, isolas, period doubling, period‐doubling cascade, and homoclinics. The effects of other reactor variables, such as total initiator concentration, coolant temperature, and reactor volume ratio on the reactor dynamics, are illustrated to show the complex dynamic behavior of the two‐reactor system catalyzed by a mixture of t‐butyl perbenzoate and benzoyl peroxide.
Viscosity buildup in condensation reactions: Reaction conditions and reactor size effects
Authors: Dairanieh I. S. 
Published: December 2004

AbstractThe viscosity of sulfonated melamine‐formaldehyde resins prepared in batch receptors of different sizes is shown to be a function of the reaction time, temperature, and pH. A formula relating these variables to viscosity buildup is presented. It shows that the pH is more influential than the temperature in increasing viscosity. The reactor mixing patterns are also shown to have a profound influence on resin viscosity. The agitator geometry, and not its tip speed, was found to affect considerably the viscosity buildup. Implications of these observations on the scale‐up of condensation reactions are discussed.
Numerical prediction of fiber orientation in injection molding
Authors: De Frahan H. Henry , Verleye V. , Dupret F. , Crochet M. J. 
Published: December 2004

AbstractWe develop a numerical method for calculating fiber orientation in the midsurface of a molded part of small thickness. Two‐dimensional fiber orientation is predicted on the basis of either Jeffery's equation or a constitutive equation for the orientation tensor. The calculation is fully transient; it is performed on a time‐dependent flow domain. The method is based on finite elements. Updated finite element meshes are generated at every instant of filling and allow one to perform an accurate calculation of the orientation even along the boundary of the flow domain. The method is applied to several examples in plane and three‐dimensional geometries.
The impact performance of thermoplastic sheet composites
Authors: Bigg D. M. , Bradbury E. J. 
Published: December 2004

AbstractSheet composites of polypropylene and poly(ethylene terephthalate) were produced by melt consolidation of alternating layers of polymer films and random glass fiber mats. The composites had a nominal glass content of 50 wt% (∼30 vol%). The sheets were stamped into a complex part from which test specimens were machined, and mechanical properties determined. Flexural strengths as high as 159 MPa were recorded for polypropylene composites and 313 MPa for poly(ethylene terephthalate) composites. The flexural modulus of the polypropylene composites reached 9.1 MPa, whereas the modulus of the stiffest poly(ethylene terephthalate) composite was 15 GPa. The impact properties of the composites were equally high. Polypropylene composites absorbed up to 257 J/cm during an instrumented falling dart impact test. Poly(ethylene terephthalate) composites absorbed as much as 116 J/cm in the same test.
Processing of thermotropic liquid crystalline polymers and their blends—analysis of an in‐situ LCP composite system
Authors: Lee Wan‐Chung , Dibenedetto Anthony T. 
Published: December 2004

AbstractThermotropic LCP/LCP fiber blends were prepared by a combination of meltblending and hot‐drawing, using a wholly aromatic copolyester KU‐9211 (also called K161 from Bayer A.G.) and an aliphatic containing LCP (liquid crystalline polymer) PET/PHB60 (from Kodak Tennessee Eastman). Morphological evidence, including scanning electron (SEM) and transmission electron microscopy (TEM), showed that the dispersed phase consisted primarily of highly oriented, 0.5 to 2 μm diameter rigid‐rods of aromatic fibers imbedded in a matrix of predominantly aliphatic LCP fibrils with diameters in the range of 20 to 50 nm. An interphase of approximately 50 nm strongly bonded the two phases together. The fiber blends were characterized using dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), gas chromotography/mass spectroscopy (GC/MS), and rheological measurements. It appears that the processing conditions employed for melt blending had caused PET/PHB60 to undergo chain scission, thereby creating chemical interactions between the two LCP components during the melt blending process. Differential scanning calorimetry (DSC) thermograms as well as nuclear magnetic resonance (NMR) spectra of the extracted fraction from the mixture of 30 wt% K161/70 wt% PET(PHB60) confirmed the chemical interaction between the two thermotropic liquid crystalline polymers.
Electrical conductivity of short carbon fiber‐reinforced polychloroprene rubber and mechanism of conduction
Authors: Jana Purnendu B. , Chaudhuri S. , Pal A. K. , De S. K. 
Published: December 2004

AbstractThe effects of concentration and aspect ratio of carbon fiber and temperature on volume resistivity of polychloroprene‐carbon fiber composites have been studied. The critical concentration of fiber wherein a sharp transition of electrical performance occurs from insulative range to conductive range is in the range of 5 to 10 phr for fibers of higher aspect ratio (∼ 100) and in the range of 20 to 25 phr for fibers with lower aspect ratio (∼ 25). Experimental values of electrical conductivity agreed reasonably well with the calculated values from a theory based on probability of formation of conductive network. Heating and cooling curves in the variation of volume resistivity with temperature do not follow the same path and results in a “hysteresis loop,” up to carbon fiber loadings of 30 phr. Such loops disappear at 40 phr loading. The activation energy of conduction for carbon fiber‐filled polychloroprene varies from 1.10 × 10−20 to 0.96 × 10−20 J. Linearity in current‐voltage relation was observed at room temperature. Increasing interfiber distance at higher temperatures disrupts the linear relation. The type of carrier in carbon fiber‐filled polychloroprene thermovulcanizate was found to be n‐type. The carrier concentration and drift mobility determined by studying the Hall effect were found in the range of 2.5 × 1022 to 2.90 × 1025 m−3 and 1.66 × 10−4 to 14.25 × 10−4 m2 V−1 s−1, respectively.
Non‐Isothermal crystallization of isotactic polypropylene in dotriacontane. II: Effects of dilution, cooling rate, and nucleating agent addition on growth rate
Authors: Lim Gordon B. A. , McGuire Kenneth S. , Lloyd Douglas R. 
Published: December 2004

AbstractNon‐isothermal crystallization growth rates of nucleated and non‐nucleated isotactic polypropylene (iPP) in dotriacontane were determined experimentally by thermal optical microscopy. Adipic acid was used as the nucleating agent. The non‐isothermal growth rates of the nucleated and non‐nucleated systems were compared with experimentally determined isothermal growth rates. The Lauritzen and Hoffman growth rate equation, originally developed for isothermal crystallization, was modified to describe the non‐isothermal growth. The modified Lauritzen‐Hoffman equation was used to predict isothermal growth rates from non‐isothermal crystallization for the nucleated and non‐nucleated polymer‐diluent mixtures. This study is the first to deal with polymer‐diluent‐nucleating agent systems vital to membrane production.
Dielectric studies of the polymerization of diethylene glycol bis(allyl carbonate)
Authors: de Meuse M. 
Published: December 2004

AbstractResults of dielectric studies are presented for the polymerization of diethylene glycol bis (allyl carbonate). Two transitions are observed in the dielectric spectra, one that can be related to motion of the carbonate unit and another that has been identified as the glass transition. A relation between the glass transition temperature and the level of conversion of double bonds has been established for this system in the 70 to 100% conversion range. While there appears to be a one‐to‐one relationship between these two parameters, such is not the case for the position of the low‐temperature, secondary transition and the level of conversion. This latter result is interpreted in terms of the local free volume available in the crosslinked system.
Modeling of the dynamics of R‐11 blown polyurethane foam formation
Authors: Baser S. A. , Khakhar D. V. 
Published: December 2004

AbstractThe dynamics of R‐11 blown polyurethane foam formation depend on the rates of viscosity increase of the reacting mixture and R‐11 evaporation, and both are controlled by the polymerization process. Detailed experiments were carried out to study the dynamics of foaming and the measurements made included the cream and rise times, the density change of the expanding foam with time, and the temperature rise during reaction. Dynamic temperature measurements at different points in the foaming mixture were also made to study the spatial variation of the temperature in the foam. The experimental results showed the rate of foaming, the final density, and the maximum temperature decreased with increasing R‐11 concentration. The heat losses from the foam were also found to be significant towards the later stages of foaming when density was low. Theoretical models were developed to predict the temperature and density change with time and spatial variation of temperature in the foam due to heat losses, by considering the foaming dynamics to be either heat generation controlled or heat and mass transfer controlled. In the former, the foam was assumed to be a pseudohomogeneous phase and the approach was similar to that of Rojas,et al.(5). New features accounted for in the model were dilution of the reactant concentration due to the presence of liquid blowing agent and heat loss from the foam due to radiation. While excellent agreement between theoretical predictions and experimental results was obtained for temperature variation with time at different locations in the foam, the model gave a much sharper reduction in density with time as compared to the experimental data. In the second model, the rate of foaming was assumed to be controlled by the rate of heat and mass transfer to a single bubble in the foam. Assuming a film model for heat and mass transfer, the theoretical predictions for both temperature and density were found to be in very good agreement with experimental data.
Influence of processing history on the properties of a thermotropic copolyester/polycarbonate blend
Authors: Turek Douglas E. , Simon George P. , Tiu Carlos 
Published: December 2004

AbstractRelationships between the rheological, morphological, and tensile properties of an immiscible blend of 25 wt% of a thermotropic liquid crystalline polymer (LCP) with polycarbonate are presented. The shear viscosity of the blend is intermediate between the two constituent materials, and indicates immiscibility in the melt. Extrudate swell behavior is examined and found to be closely related to that of polycarbonate. The morphology of the dispersed LCP phase varies between droplets and oriented fibrils, and is highly correlated with changes in tensile properties. Fibrils are associated with increased tensile modulus, and their development is favored in the elongation flow fields present in the spinline and in the die convergence section. In all cases, blend stiffness is less than that predicted for a continuous fiber‐reinforced composite. Enhanced tensile modulus is associated with both extrusion from shorter length dies and increases in spinline draw ratio, with the latter proving the most important in fibril formation.
The effect of a partly hydrolyzed styrene‐tert‐butyl acrylate diblock copolymer on the properties of poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) and polyamide‐6 (PA) blends
Authors: Kim Ho Cheol , Jo Won Ho 
Published: December 2004

AbstractThe compatibilizing effect of a polystyrene‐hydrolyzed poly(t‐butyl acrylate) diblock copolymer (SBAH) on the phase structure, rheological properties, and mechanical properties of immiscible poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) and polyamide‐6 (PA) blends was investigated. The SBAH was prepared by sequential anionic polymerization of styrene and t‐butyl acrylate, followed by acid‐catalyzed hydrolysis of t‐butyl acrylate block. Scanning electron micrographs show that the blends exhibit a more regular and finer dispersion when the SBAH of 47% hydrolyzed t‐butyl acrylate block is added. By addition of small amount of the block copolymer, the blends show non‐Newtonian power‐law behavior, and the contribution of storage modulus (G′) to the total response increases. Solubility tests support the formation of graft copolymer by chemical reaction between amine groups of the PA and carboxyl groups of the SBAH. Both modulus and strength are improved about 20% with addition of the 3 wt% SBAH, while the elongation at break decreases notably; thus, the blends fail in a brittle manner.
Time dependent response of polycarbonate and microcellular polycarbonate
Authors: Wing Gregory , Pasricha Arun , Tuttle Mark , Kumar Vipin 
Published: December 2004

AbstractMicrocellular polycarbonate is a novel cellular material with cells on the order of 10 μm in diameter and a cell density on the order of 109 cells per cm3. In this study the room temperature creep response of microcellular polycarbonate is experimentally determined and compared with the creep behavior of polycarbonate. The viscoelastic response of polycarbonate and microcellular polycarbonate is characterized using Schapery's theory of nonlinear viscoelasticity. Polycarbonate exhibited a nonlinear creep response at stress levels above 24.13 MPa, while the nonlinear behavior in microcellular polycarbonate was initiated at lower stress levels. Creep strains of microcellular polycarbonate contain a significantly higher viscoplastic component compared with the unfoamed material.
Morphology and barrier properties of oriented blends of poly(ethylene terephthalate) and poly(ethylene 2,6‐naphthalate) with poly(ethylene‐co‐vinyl alcohol)
Authors: Kit Kevin M. , Schultz Jerold M. , Gohil Ramesh M. 
Published: December 2004

AbstractMorphology and oxygen permeability studies were carried out for blends of poly(ethylene terephthalate), PET, and poly(ethylene 2,6‐naphthalate), PEN, with poly(ethylene‐co‐vinyl alcohol), EVOH. PET/EVOH blends are seen as a possible substitute for poly(vinylidene chloride)‐coated PET packaging films. The effects of several processing parameters such as draw temperature and draw ratio on blend morphology and barrier properties suggest that the morphology of the EVOH phase dictates to a large extent the oxygen permeabilities of these blends. The relationships between morphology and oxygen permeability and explained are explained by consideration of two‐phase conduction models. The model of Fricke is found to be a good predictor of the barrier properties of the PET/EVOH system. The oxygen permeability of PET was reduced by a factor of 4.2 with the addition of 20 wt% EVOH and that of PEN by a factor of 2.7 with the addition of 15 wt% EVOH. Water vapor permeabilities and mechanical properties of PET and PEN were only slightly affected by the addition of 15 wt% EVOH.
Property Function for Product Development
Authors: Polke Reinhard 
Published: December 2004

AbstractA knowledge of the effects of the physical parameters of solids on the product quality – the property function – is necessary for selective optimisation, to determine the cause of discrepancies and to permit corrections to be made as early as possible in a process. Property functions apply not only to the end products but to every stage of the process. The particle properties of the end product affect the quality, for example the colour strength, while those of the intermediates influence processing properties, for example the filtration resistance and subsequent process stages such as washing and granulation.In order that the property functions can be determined, the properties, performance characteristics as well as physical characteristics, must be quantifiable. Particle measuring technology was initially restricted to the measurement of physical characteristics but is increasingly becoming concerned also with performance characteristics such as the flow behavior of bulk solids and their abrasion resistance. The remaining performance characteristics can either be estimated, quantified or merely treated qualitatively.
Detection of Water Droplet Size and Anion Species by Nonlinear Optical Scattering
Authors: Eickmans Johannes H. , Qian Shi‐Xiong , Chang Richard K. 
Published: December 2004

AbstractThe liquid‐air interface causes the droplet to act as an optical cavity which provides large internal fields and feedback. The stimulated Raman scattering (SRS) spectra of micrometer‐size water droplets containing different anions (e.g., NO, SO, and PO) can be generated by a single laser pulse and detected by an optical multichannel analyzer. When the spontaneous Raman intensity of the ν1 mode of the anions is larger than that of the O‐H stretching mode of water, the SRS spectra consist of the peak at ν1 and multiple peaks of nearly equal wavelength separation within the O‐H stretching mode of water. These multiple peaks are associated with the morphology‐dependent resonances of a sphere and the refractive index of water. Thus, the wavelength spacing of these SRS peaks provides information on the droplet radius. At higher anion concentrations, sequentially pumped SRS involving the ν1 anion mode can also be detected at Raman shifts equal to 2ν1 and equal to the O‐H stretching mode plus ν1. The Raman shift of the ν1 mode in wavenumbers provides molecular specific information.