bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measuring the surface energies of spherical cellulose beads by inverse gas chromatography
Authors: Garnier Gil , Glasser Wolfgang G. 
Published: April 2004

AbstractThe effect of the chemical composition of regenerated cellulose solids on surface energy was studied by inverse gas chromatography (IGC). This was to probe a possible relationship between the ability of the cellulose surface to interact with other phases through van der Waals forces and its bonding potential. A model consisting of amorphous cellulose spheres (“beads”) was used to eliminate all effects of morphology and geometry. The surface of the beads was modified by chemical reaction of the hydroxyl groups of cellulose. A thin layer of cellulose derivative, such as cellulose trifluoroethoxyacetate (CW‐TFEA), cellulose laurate (CW‐LA), or directly fluorinated cellulose (CW‐F), was produced on the bead surface. The surface properties of the cellulose beads were fully characterized by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and nitrogen adsorption. IGC was performed using the adsorption of two kinds of probes: alkanes to measure the dispersive component of the surface energy (γ), and acid/base probes to quantify the specific adsorption enthalpy (ΔHSp). The dispersive component of the surface energy of cellulose was found to depend mostly on the presence and concentration of free hydroxyl groups on the surface. At low degrees of substitution (DS < 1), how these OH groups were replaced by modification, whether by fatty acid type substituents or by fluorine‐containing groups, was essentially irrelevant for surface energies. The dispersive component of the surface energy (γ) declined with DS almost irrespective of substituent type. The surface of cellulose was found to be highly acidic, and this was attributed mainly to the presence of hydroxyl groups.
Three‐dimensional flow modeling of a self‐wiping corotating twin‐screw extruder. Part II: The kneading section
Authors: Van Der Wal D. J. , Goffart D. , Klomp E. M. , Hoogstraten H. W. , Janssen L. P. B. M. 
Published: April 2004

AbstractThree‐dimensional flow simulations of kneading elements in an intermeshing corotating twin‐screw extruder are performed by solving the Navier Stokes equations with a finite element package, Sepran. Instead of using the whole geometry of the 8‐shaped barrel a simplified geometry is used, representing a large part of the geometry during the rotating action of the kneading paddle. The goal of these calculations is to study the dependence of several factors that influence mixing, such as shear rate, elongation rate, pressure, and the flow profile in the extruder on various extruder parameters, such as fluid viscosity, rotation speed, and throughput.The shear and elongation rate and the pressure drop are calculated for varying viscosities. The various stagger angles possible for disc configurations in the corotating twin‐screw extruder are modeled. The axial backflow volume is calculated for varying values of rotation speed and throughput.
Rheotens‐mastercurves and drawability of polymer melts
Authors: Wagner M. H. , Schulze V. , Göttfert A. 
Published: April 2004

AbstractIn a Rheotens experiment, the tensile force needed for elongation of an extruded filament is measured as a function of the draw ratio. For thermo‐rheologically simple polymer melts, the existence of Rheotens‐mastercurves is proven. Rheotens‐mastercurves are invariant with respect to changes in melt temperature. Also, for polymer melts with different average molar masses, but similar molar mass distribution and branching structure, Rheotens‐mastercurves are invariant to changes in the average molar mass. It is shown, by testing several polyethylenes with different molar mass distribution and different long‐chain branching, that Rheotens‐mastercurves allow a direct and quantitative assessment of the drawability of polymer melts under actual processing conditions, i.e. under the action of a constant tensile force and including the effects of the rheological prehistory in the extrusion die.
The effect of injection molding conditions on the mechanical properties of an in situ Composite. I: Polypropylene and a liquid crystalline copolyester based on hydroxynaphthoic acid
Authors: O'Donnell Hugh J. , Baird D. G. 
Published: April 2004

AbstractIn this study, the effect of injection molding conditions on the mechanical properties of polypropylene/liquid crystalline copolyester in situ composites was investigated. Molding conditions such as fill time, mold temperature, and mold thickness were varied to determine the most significant variables that influence mechanical properties. The mechanical property variations were correlated to the shear or extensional stress, which deforms a dispersed phase, and to the Graetz number, which indicates the influence of heat transfer. It was found that higher flexural moduli were obtained in thinner molds and that the maximum mechanical properties for a given mold thickness were obtained near a Graetz number of ten. This indicated that heat transfer was a controlling factor in the formation of in situ composites.
Predicting the effect of viscosity ratios on the mixing of polymer blends using the boundary element method
Authors: Stradins Linards , Osswald Tim A. 
Published: April 2004

AbstractMixing or blending two or more fluids of different viscosities is an important and complex issue in the polymer industry. Simulating these types of processes leads to a better understanding of the flow phenomena that take place during mixing. The boundary element method is ideal to simulate mixing flows, because of the large deformations and moving boundary nature of internal batch mixers and extruders. This paper presents a boundary element simulation of the flow of multi‐viscous polymer blends inside extruders and internal mixers. In addition, the governing equations, boundary integrals, and their numerical implementation for creeping flows are presented. The simulation is used to predict the mixing quality of polymer blends in realistic mixing processes. A model describing the relationship of drop strain to matrix strain as a function of viscosity ratio is also presented. The flow simulation results are in good agreement with analytical and experimental results.
Optical on‐line measurement of the thickness distribution of blow molding parisons
Authors: Swan P. L. , Kamal M. R. , Garcia‐Rejon A. , Cielo P. 
Published: April 2004

AbstractAn optical sensor has been developed which can measure the thickness profile of the parison on line just prior to its enclosure in the mold. The device determines thickness by striking the parison at an angle with a laser beam and measuring the separation between the beams that are reflected from the outer and inner surfaces of the parison wall. A prototype was built and tested. The prototype uses three lasers at different angles and can make up to 250 point measurements during a one second scan. A personal computer uses specially developed software to reconstruct the profile of the parison wall from the raw data with an accuracy of ±5%.
The effect of colorants on the properties of rotomolded polyethylene parts
Authors: Nagy Tibor , White James L. 
Published: April 2004

AbstractAn experimental study is reported on the effect of colorants on the warpage, shrinkage, and mechanical properties of rotomolded polyethylene (PE) parts. Five pigments were investigated (titanium dioxide white, cadmium oxide yellow, iron oxide red, carbon black, and phthalocyanine blue). Their concentration was in the range of 0.11 to 0.36 wt%. The pigments were added to the linear low‐density polyethylene (LLDPE) by various techniques, dry blended in low intensity or high intensity mixer or compounded with a single‐screw extruder. Some blends also contained 0.077 wt% zinc stearate as surfactant. It was found that zinc stearate surfactant in the dry blend increases warpage by about a factor of 2 and shrinkage by ˜ 30%, but color quality and powder handling properties are improved. The dry‐blended pigments concentrate along the fusion lines of the PE particles in rotomolded parts, which results in >50% decrease of impact strength with some pigment‐surfactant combinations. Mold pressurization minimizes warpage and shrinkage, but causes no significant improvement in impact resistance. Impact resistance can be improved by using compounded pigments or making two‐layer parts with a pigmented outer and unpigmented inner layer.
Measurement and modeling of solvent removal for spin coating
Authors: Gu J. , Bullwinkel M. D. , Campbell G. A. 
Published: April 2004

AbstractSolvent concentration is an important factor for spin‐coated film planarization. Two techniques, one an on‐line optical method and the other an off‐line gel permeation chromatography method, have been used to investigate the coating concentration change during spinning. The experimental observations are compared with the spin‐coating model predictions. The modeled concentration and thickness are in close agreement with experiment. Under certain conditions, the spin‐coating model can be significantly simplified. These conditions are discussed.
Process optimization of ultrasonic welding
Authors: Van Wijk H. , Luiten G. A. , Van Engen P. G. , Nonhof C. J. 
Published: April 2004

AbstractAn experimental design is presented for optimizing the ultrasonic welding process in series and mass production, which requires a quantitative test method for measuring product quality. In addition to measurements of an average value, the standard deviation is also important. Small standard deviations lead to reduced scrap in production. For the optimization study, a simple welding process was chosen. Welding machines usually have adequate accuracy for a repeatable machine setting with respect to weld quality. In the cases investigated, they were not sufficiently accurate to allow for a simple quality control using the microprocessor in the machine control as a measuring device. Apart from the insufficient accuracy of the welding machines for quality control, there proved to be no correlation between weld quality and weld‐time measurement under energy control.
A rheo‐optical analysis of converging wedge flow for estimation of stress‐optical coefficient
Authors: Subramanian R. , Picot J. J. C. 
Published: April 2004

AbstractResults are presented from a rheo‐optical study of a poly(dimethyl siloxane) (PDMS) fluid in a converging wedge flow cell at room temperature for estimation of the linear stress‐optical coefficient. The linearity of the stress and polarizability or refractive index tensors were checked by flow birefringence measurements in pure extensional flow along the centerline of the converging flow cell that extended well into the non‐Newtonian region. The stresses were evaluated using (a) shear and extension rates from laser Doppler anemometry (LDA) velocity measurements and (b) information obtained from orientation angle as a test of constitutive equations. All measurements were optical (i.e., non‐intrusive), and a linear stress‐optical coefficient of 1.475 × 10−10 Pa−1 was obtained using a two‐term Goddard‐Miller model for room temperature flow of a PDMS fluid in combined shear and extension in a converging wedge flow cell.
Comparison of fast fracture properties of thermoplastics
Authors: Dear John P. 
Published: April 2004

AbstractThe fast fracture behavior of polyethylene, polycarbonate and poly(methyl methacrylate) are compared for two different thicknesses of material. The aim was to make fracture measurements under precisely defined steady load conditions after the material has reached a stress relaxed state. It was essential that the experimental technique provided good isolation between crack initiation and crack propagation. This was achieved in small rectangular shaped specimens by adding a tongue to one side extending the intended crack path. A fast crack was initiated in the tongue to propagate into the main section after it had been loaded and allowed to stress relax. When necessary the tongue was embrittled by cooling so a crack can be initiated with minimum force. This new method obtains the threshold load to just maintain crack propagation and also the increase of crack velocity with load above this threshold up to the limiting condition.
Moisture effects on isobutylene‐isoprene copolymer‐based composite barrier. I: Moisture diffusion and detection
Authors: Lee B. L. , Yang T. W. , Wilusz E. 
Published: April 2004

AbstractExperiments have assessed how moisture and heat influence the functional and structural integrity of butyl rubber matrix composites used as protective barriers. This paper, which is first of a series, reports the findings on the subjects of moisture diffusion and its effect on ultrasonic wave propagation of composite barriers. On exposure to high humidity at elevated temperatures, carbon black‐reinforced butyl rubber composite barriers were found to absorb substantial moisture, with the hygroscopic reinforcement phase making a more significant contribution than the matrix. The moisture diffusion coefficients for both composite and unreinforced vulcanizate were close to each other at each exposure temperature, and had the same temperature dependence. The calculated activation energies of moisture diffusion indicate that the moisture absorption rate of the carbon black phase is governed by the moisture diffusion rate of the matrix. Ultrasonic wave speed appeared to be a viable means of monitoring the moisture absorption of composite barriers. On exposure to moist heat, relative ultrasonic wave speeds for both composite and unreinforced vulcanizate decreased continuously.
Real‐time analysis of ethylene vinyl acetate random copolymers using near infrared spectroscopy during extrusion
Authors: Khettry Atul , Hansen Marion G. 
Published: April 2004

AbstractPoly(ethylene vinyl acetate) (EVA) is a very common polymer used in hot melt adhesives. The rheological and thermal‐mechanical properties of these adhesives are strongly related to the content of vinyl acetate (VA) incorporated into this random copolymer during polymerization. Results of in‐line monitoring of VA content in flowing molten EVA polymers, using fiberoptic near infrared spectroscopy, shall be discussed in detail. In‐line monitoring is not only desired for its numerous advantages (such as high quality products, lower waste, lower developmental cycle time, and lower costs) but also because it eliminates the sample handling concerns associated with molten polymers.
Elastic moduli of a liquid crystalline polymer and its in‐situ composites
Authors: Choy C. L. , Lau K. W. E. , Wong Y. W. , Yee A. F. 
Published: April 2004

AbstractThe elastic moduli of a liquid crystalline polyesteramide (LCP) and polycarbonate/LCP in‐situ composites with 10 to 80 wt% of LCP have been measured as functions of draw ratio λ from 1 to 15 by an ultrasonic method. For the LCP, the sharp rise of the axial Young's modulus E3 and the slight decreases of the transverse Young's modulus E1 and the axial (C44) and transverse (C66) shear modulus with increasing λ result from the alignment of chains along the draw direction. E1, C44, and C66 follow the lower bounds calculated using the series coupling scheme of the aggregate model. Although E3 lies close to the lower bound at low λ, it follows the upper bound calculated according to the parallel coupling scheme at λ > 3. The elastic moduli of the composites have similar draw ratio dependences as those of the LCP. The strong increase in E3 with increasing λ arises from the higher aspect ratio of the LCP domains in the composites and the improved molecular orientation within the domains. The reinforcement effect on the other moduli is much weaker, with E1 and C44 of the composites only 5 to 30% higher than those of polycarbonate at λ = 15. Since C66 of the LCP decreases to a value below that of polycarbonate at λ > 2, there is a positive reinforcement effect at low λ but a negative effect at high λ.
The effect of processing variables on the environmental stress crack resistance of blow‐molded polyethylene bottles
Authors: Strebel J. J. , Benson M. 
Published: April 2004

AbstractThe effects of blow‐molding process variables on the environmental stress crack resistance (ESCR) of high‐density polyethylene (HDPE) bottles were studied. Experimental design was employed to test the effect of die temperature, mold temperature, molding time, and drop time. Bottles blown at each condition were tested using the internal pressure ESCR test. Through the use of regression analysis, the effect of each variable was quantified. Increasing die temperature, mold temperature, or molding time decreased ESCR. However, increasing drop time increased ESCR.
Evaluation of collisional damage in polystyrene foam constructions using a dual hammer impact test
Authors: Medding J. A. , Love B. J. 
Published: April 2004

AbstractLow intensity impacts can reduce the structural integrity of an expanded polystyrene safety helmet by the formation of damage in the foam. This reduces the ability of the foam to protect the user under impact conditions. In these experiments, the introduction of a rubber inter‐layer that acts as a cushioning layer to protect the polystyrene shell during light and intermediate impacts was evaluated. The evaluation was conducted with a dual hammer impact tester, which was constructed for this purpose. Safety helmet cross sections were simulated by two inch square test specimens. The dual hammer impact testing identified a damage threshold energy above which damage was evident. The introduction of the soft rubber inter‐layer between the foam and outer hard shell of these specimens increased the impact loading required to damage the foam by 30%, while the amount of energy transmitted actually increased. Further work is being done on perforated rubber systems that will look at damage and energy transmission in these alternative constructions.
The effect of specimen thickness and stress ratio on the fatigue behavior of polycarbonate
Authors: Pruitt L. , Rondinone D. 
Published: April 2004

AbstractThe cyclic residual stresses ahead of fatigue cracks are known to play an important role in the fatigue fracture response of engineering materials. The size of these residual stresses are directly affected by the stress state of the component. In this paper, we examine the effect of stress state for fully compressive and fully tensile cyclic loading of polycarbonate. The role of stress state is studied using two different specimen thicknesses, one thickness will represent a near‐plane stress condition and the other will represent a near‐plane strain condition. In cyclic compressive loading, it will be shown that the near‐plane stress specimen with its larger zone of residual tension will exhibit enhanced crack saturation lengths. While for cyclic tensile loading, the larger zone of residual compression upon unloading will result in crack retardation for the same unloading stress intensity. A series of systematic experiments on the effects of mean stress on fatigue fracture is reported, and the results of the experiments are rationalized with the aid of scanning electron microscopy of the fracture surfaces. The results of this study have strong implications for both constant amplitude fatigue loading and variable amplitude fatigue loading as well as applicability to other engineering materials.
Generalized warpage parameter
Authors: Kikuchi Hiroyuki , Koyama Kiyohito 
Published: April 2004

AbstractA warpage index (Δψm) was introduced for studying warpage characteristics of a plastic part injection molded from PA66 compounded with 30 wt% glass fiber. Δψm is defined as Δψm = (Δψm)max – (Δψm)min, where ψm = ψ(θ)max, where ψ(θ) = (ε(θ) – α(θ)ΔT)/| α(θ)ΔT|, where ε is the total strain, α is the linear thermal expansion coefficient, ΔT is temperature difference, and θ is the angle along which ε and α are calculated. Finite element analysis was used for calculating flow field in injection, fiber orientation, material anisotropy and warpage. ψm is calculated in each finite element, and Δψm is calculated in a whole finite element model. Δψm is a measure of the ratio of actual shrinkage to the amount of shrinkage that would occur if an element freely shrank. The characteristics of Δψm were studied. It has been found that warpage is null if Δψm = 0, but that null warpage generally does not indicate Δψm = 0. It is shown that Δψm quantitatively represents the warped and unwarped state. Δψm distinguishes the null warpage state with possible buckling from the null warpage state without possible buckling. It has been shown that material anisotropy is possibly described with Δψm, and that the cause of warpage is self‐restrictive deformation in an injection molded part. It has been deduced that it is generally not possible to eliminate warpage only by controlling material properties. Δψm is obtainable for a plastic part with complex geometry and complex fiber orientation state, and for arbitrary materials. Applications of Δψm are left for future study.
Warpage, anisotropy, and part thickness
Authors: Kikuchi Hiroyuki , Koyama Kiyohito 
Published: April 2004

AbstractRelations among warpage, material anisotropy, and part thickness were numerically investigated for disks injection molded from PA66 compounded with 33 wt% glass fiber. Finite element analysis was used for calculating flow fields in injection, fiber orientation, material anisotropy, and warpage. Volume averaged anisotropy has been introduced, which is a ratio of the volume averaged linear thermal expansion coefficient in the flow direction to the coefficient in the direction transverse to flow (〈Rα〉 = 〈α11〉/〈α22〉). Good agreement has been obtained between calculation and experiment with respect to 〈Rα〉. A mechanical quantity, (ΔT)b/h2, which is the buckling temperature divided by the square of disk thickness, is also introduced. Differences in mechanical behavior between an injection molded disk and a composite laminate disk have been shown. A linear correlation between the mechanical quantity and the material anisotropy is also found. Parameters that determine the disk warpage are deduced from the correlation. The correlation for the injection molded disk is found to be a subset of the correlation for the composite laminate disk. The correlation between 〈Rα〉 and (ΔT)b/h2 has been extended so that the relation is applicable not only to anisotropic materials but also to isotropic materials.
Synthesis, characterization, and mechanical properties of an injection moldable polyimide based on 1,4‐diaminobutane
Authors: Koning Cor , Teuwen Liliane , Bulters Markus 
Published: April 2004

AbstractA partially aliphatic polyimide was synthesized in a two‐step process in N‐methylpyrrolidone (NMP) from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and 1,4‐diaminobutane (DAB). Weight average molecular weights ranging from 35,000 to over 160,000 were obtained by adding different amounts of the chain stopper phthalic anhydride, or by using a slight excess of BTDA. Rheological measurements, supported by a size exclusion chromatography (SEC) analysis before and after injection molding, point to branching or even partial crosslinking during molding of poly(BTDA‐DAB) if reactive amine endgroups are present. By reacting these amine endgroups with benzoyl chloride, branching is limited and a more Newtonian flow is observed. Both non‐endcapped and endcapped reactor powders are ∼60% crystalline (Tg = 170 to 175°C, Tm = 290 to 300°C), but according to wide and small angle X‐ray scattering (WAXS and SAXS) studies on test bars, both the more linear polyimides and their branched counterparts are fully amorphous after injection molding. Nevertheless, poly(BTDA‐DAB) shows interesting mechanical properties like a bending modulus of ∼3.9 GPa, a tensile strength of ∼130 MPa, a tensile elongation at break of ∼13%, and a notched Izod impact of ∼4 kJ/m2.