bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of pressure sensitivity and notch geometry on notch‐tip fields
Authors: Al‐Abduljabbar A. , Pan J. 
Published: April 2004

AbstractPlane‐strain stress and slip‐line fields near the sharp and round tips of wedge‐shaped notches in perfectly plastic pressure‐sensitive materials are investigated to illustrate the effects of pressure sensitivity and notch geometry on notch‐tip fields. The Drucker‐Prager yield criterion is adopted to describe the material yielding behavior. Notch‐tip stress and slip‐line fields are first established for a sharp notch. Then the notch‐tip stress and slip‐line fields for a round notch tip are obtained. The results indicate that for sharp wedge‐shaped notches, as the pressure sensitivity increases, the opening stress and hydrostatic tension ahead of the tip decrease. As the wedge angle increases, the opening stress and hydrostatic tension ahead of the tip decrease. For round wedge‐shaped notches, as the pressure sensitivity increases, the extent of the exponential spiral zone ahead of the tip increases. As the wedge angle increases, the extent of the exponential spiral zone ahead of the tip decreases and the maximum opening stress and hydrostatic tension ahead of the tip decrease. The closed‐form notch‐tip stress solutions are useful for design of plastic structural components.
Investigation of gas‐assisted injection molding. Part III: Effect of gas channel design on part bending strength
Authors: Chen Shia‐Chung , Hu Sheng‐Yan , Huang Jeng‐Sheng , Chien Rean Der 
Published: April 2004

AbstractNumerical simulation and experimental measurements were carried out to investigate the effect of gas channel design on the bending performance of gas‐assisted injection molded parts. Plate parts designed with various channel geometries were gas‐assisted injection molded. Part flexible strength were measured via bending tests. It was found that part stiffness basically increases linearly with the inertia moment of the plate. The gas channel introduces an additional moment of inertia, the amount of which is determined by the shape and the dimension of the channel section as well as the hollowed core geometry. An analysis algorithm based on DKT/VRT elements superimposed with beam elements representing gas channels of various section geometries was developed to evaluate part bending behavior. An equivalent diameter was assigned to the beam element so that both the original gas channel and the circular beam have the same moment of inertia. The analyzed results from this model of 2 1/2‐D characteristics were also verified with both 3‐D and 2 1/2‐D analyses using ANSYS. The present simulations show reasonable accuracy as compared with experimental measurements and predictions from ANSYS. This investigation also indicates that it may be feasible to use the same CAE finite element model implemented for process simulation of gas‐assisted injection when performing part structural analysis as well as warpage calculation, resulting in great computational efficiency for industrial application.
Hot plate welding of polypropylene. Part II: Process simulation
Authors: Nieh Jenn‐Yeu , Ni Jun , James L. 
Published: April 2004

AbstractA volume of fluid finite difference method based computer code was developed to simulate the heat transfer and squeezing flow in the hot‐plate welding process. The simulation results include melt displacement, temperature distribution, and stress build‐up and relaxation. By implementing the crystallization kinetic model developed in Part I, the formation of stress‐induced crystal structure in the heat affected zone can be revealed.
Effects of surface modification by Ar+ irradiation on wettability of surfaces of poly(ethylene terephthalate) films
Authors: Park Sung‐Chul , Koh Seok‐Keun , Pae Kook D. 
Published: April 2004

AbstractSurfaces of poly(ethylene terephthalate); PET, films were irradiated with Ar+ at 1 keV using various ion doses (ID) from 1014 to 1017 ions/cm2 (isc) with and without an O2 environment. The wettability of the modified surfaces of PET was determined by measuring the contact angle between water droplets and the modified surfaces. The modified surfaces were also characterized by AFM (atomic force microscopy) and XPS (X‐ray photoelectron spectroscopy) for changes in the surface morphology, and the chemical composition and molecular structure, respectively. The contact angle decreased from 70° for unmodified surfaces to 45° for modified surface with ID = 1014 isc without O2 and remained relatively constant with higher ID. The contact angle, however, reached a minimum value of 8° for modified surfaces with ID = 1016 isc with O2. The improved wettability may be due to a combination of the formation of hydrophilic groups, chemical and molecular structural changes, physical structural or morphological changes, and increased roughness of the surface. The wettability of the modified surfaces also depended on the time of exposure to air. The wettability worsened with exposure time to air, but was revived by immersing the films into water. Possible mechanisms for the change of the wettability of the modified surfaces are given.
Determination of the degree of fill in a counter‐rotating twin screw extruder
Authors: Van Der Goot A. J. , Poorter O. , Janssen L. P. B. M. 
Published: April 2004

AbstractCurrent residence time distribution models for counter‐rotating extruders are mainly developed for fully filled machines. However, in practical situations, these extruders operate under starved conditions. To overcome this missing link in the current models, this paper describes the average degree of fill in the situation of starvation. This degree of fill is determined by the length over which the extruder is fully filled and the degree of fill in the partially filled zone. The comparison of the experiments with the theory shows that the existing theory underestimates the length of the fully filled zone by about 30%. The degree of fill in the partially filled zone is well predicted by taking into account all non‐pressure driven leakage flows.
Grooved feed single screw extruders—improving productivity and reducing viscous heating effects
Authors: Davis Bruce A. , Gramann Paul J. , Noriega E. Maria Del P. , Osswald Tim A. 
Published: April 2004

AbstractOwing to their high productivity, pressure invariance, and controlled throughput and melt temperature, groove feed systems are becoming widely accepted for the extrusion of pipes, blown films, and blow molded articles. Within the research presented in this paper, a fully instrumented 45 mm extruder equipped with a grooved fed bushing was used to measure pressure distributions, screw and die characteristics, and melt temperature profiles. The screw geometry included decompression and compression zones, and Saxton distributive and Maillefer dispersive mxing heads. The screw and die characteristic curves show the high system productivity where throughputs comparable to 60 and 90 mm conventional extruders were measured. The high throughput induced a dramatic reduction in melt temperature measured at the tip. To better understand and confirm our experimental findings, analytical models were used.
The Sephadex story
Authors: Flodin Per 
Published: April 2004

AbstractThe environment and the circumstances leading to the Sephadex group of products for gel filtration (SEC, size exclusion chromatography) are described. The importance of Porath's and the author's experience from zone electrophoresis is stressed. To be able to get high resolution the technique for packing columns was of decisive importance for electrophoresis. It paved the way for the observation of the separation properties of dextran gels. The synthesis of dextran‐based gels at AB Pharmacia and the development of varieties of them for varying applications are described together with the project leading to their marketing in 1959. The work of the author on gel filtration is summarized. The story is based on publication and memory. Aids to the latter have been laboratory notebooks and other documents still in the possession of the author.
Biodegradable polymers and environmental interaction
Authors: Karlsson Sigbritt , Albertsson Ann‐christine 
Published: April 2004

AbstractBiodegradable polymers are by definition those that degrade as a result of the action of microorganisms and/or enzymes. The rate of this biodegradation may vary from hours to years depending on the molecular architecture of the polymer in question. Biopolymers like lignin take years to degrade while many proteins and polysaccharides degrade within hours to days. The same is true for the synthetic biodegradable polymers where polyethylene is sometimes regarded as inert to biodegradation while polyanhydrides are rapidly biodegradable. The influence of structure, morphology, and surface area on the biodegradability are discussed, with polyesters and degradable polyethylene (with pro‐oxidant and/or biodegradable additives) as examples. The rate of biodegradation is controllable by choosing the appropriate molecular architecture. In addition to this the environmental interaction of these polymers should be determined. The degradation product pattern of biodegradable polymers should be compatible with the natural degradation mechanisms (i.e., catabolisms).
Selective froth flotation of PVC from PVC/PET mixtures for the plastics recycling industry
Authors: Drelich J. , Payne T. , Kim J. H. , Miller J. D. , Kobler R. , Christiansen S. 
Published: April 2004

AbstractIt was found that strongly alkaline solutions of sodium hydroxide are able to destroy the hydrophobicity of polyethylene terephthalate (PET) whereas the hydrophobicity of polyvinyl chloride (PVC) remains only slightly affected by these solutions. On this basis, a technology involving treatment of PET and PVC particles with alkaline solutions followed by froth flotation of PVC with nonionic surfactants has been developed and tested at a laboratory scale. In both steps of this technology, appropriate experimental conditions, such as concentration of reagents, temperature and residence time, have been optimized through a detailed examination of all these variables on the efficiency and selectivity of PVC separation from PVC/PET mixtures of varying composition. It is demonstrated that using this technology 95–100% recovery of PET and PVC can be achieved in separate products from a variety of PVC/PET mixtures.
Steady shear and dynamic properties of biodegradable polyesters
Authors: Ramkumar D. H. S. , Bhattacharya M. 
Published: April 2004

AbstractThe rheological properties of three biodegradable partially crystalline alipathic polyesters—poly ε carolactone (PCL), polylactic acid (PLA), and polyhydroxybutyrate‐co‐hydroxyvalerate (PHBV)—were investigated. Low shear viscosity (η), first normal stress difference (N1), and dynamic properties (G′ and G″), were measured for each polymer using rotational instruments. High shear viscosity data was obtained using a capillary rheometer. Gel permeation chromatography indicates that both PLA and PHBV undergo degradation during processing. Thermal degradation rate constants for PLA and PHBV were determined from the time‐sweep data. Data indicates that material functions are proportional to the molecular weight for PCL and PLA samples, and directly related to the HV content in the PHBV samples. The relaxation spectra were calculated from the G′ and G″ data using the regularization method and the applicability of the nonlinear Wagner equation was checked on these materials. Results are discussed in terms of variations in the molecular characteristics on rheological properties and their possible influence on the processability.
Optimal cooling system design for the injection molding process
Authors: Park S. J. , Kwon T. H. 
Published: April 2004

AbstractA computer‐aided optimal design system was developed to improve the performance of a cooling system for injection molding. This was done by minimizing a weighted combination of the uniformity of the part temperature and the cooling time. The CONMIN algorithm was adopted to obtain the optimal design using the special boundary integral formulation and a corresponding design sensitivity analysis formulation. Design variables related to the processing conditions (i.e., inlet coolant temperature and volumetric flow rate of each cooling channel) and mold cooling system design (radius and location of each cooling channel) were considered. Three different optimization strategies are suggested, and three sample problems were solved to demonstrate the efficiency and the usefulness of this optimization procedure.
Characterizations for blends of phosphorus‐containing copolyester with poly(ethylene terephthalate)
Authors: Chang Shinn‐Jen , Chang Feng‐Chih 
Published: April 2004

AbstractHigh molecular weight phosphorus‐containing copolyesters, poly(ethylene terephthalate)‐co‐poly(ethylene DDP) (PET‐co‐PEDDP)s, were prepared and characterized with the objective of producing a non‐halogen flame retardant system for practical applications. The phosphorus‐containing copolyester with 30 wt% phosphorus (P30 copolyester) was blended with PET to evaluate their characteristics and flame retardancy. Higher phosphorus content results in lower crystallinity and higher char formation after thermal degradation. The rheological behavior remains similar to that of PET. The P30/PET blend possesses higher crystallization rate than the corresponding phosphorus‐containing copolyester containing equal phosphorus content. Thermal and rheological behaviors of P30/PET blends are similar to PET or the phosphorus‐containing copolyesters. The P30/PET blends are miscible or compatible base on single Tgs detected by DSC or DMA. The SEM/EDX phosphorus mapping image of the P30/PET blend shows uniform distribution of the phosphorus moieties within the P30/PET matrix, another indication of a compatible or miscible blend between the phosphorus‐containing copolyester P30 and PET. Flame retardancy of the P30/PET blend is identical to that of the phosphorus‐containing copolyester with identical phosphorus content. Blending of high phosphorus content copolyester with virgin PET provides a feasible method to obtain a flame resistant PET with LOI greater than 28.
Indentation measurements using a dynamic mechanical analyzer
Authors: Payne Jason A. , Strojny Angela , Francis Lorraine F. , Gerberich William W. 
Published: April 2004

AbstractA dynamic mechanical analyzer equipped with a diamond indenter tip was used to measure the elastic modulus of polymeric coatings as well as various bulk materials. A fabricated indenter probe was used to indent bulk samples of aluminum and fused quartz, as well as gelatin and polystyrene films in order to compare the micron‐level indentation measurements with sub‐micron (nanoindentation) techniques. The measured moduli were in agreement for ductile materials and thick films (>20 μm), but limited displacement resolution, material cracking, and hydrostatic pressure effects led to diverging values for thinner coatings and more brittle materials.
Measurement of three‐dimensional velocity field in the translational region of a co‐rotating twin‐screw extruder
Authors: Bakalis Serafim , Karwe Mukund V. 
Published: April 2004

AbstractThe velocity field in the screw channels of a co‐rotating twin‐screw extruder was measured using laser Doppler anemometry. Velocity distributions were measured for two screw elements having pitches of 14 and 28 mm, respectively. The magnitude of radial velocity component for both elements was no more than 10% of the magnitude of total velocity. The radial and the axial velocity components were similar for both screw elements. Wider range of tangential velocity values and steeper gradients near the flights were observed for smaller pitch screw element.
Experimental study of the transcription of minute width grooves by injection molding (II)
Authors: Yoshii Masaki , Kuramoto Hiroki , Ochiai Yuuji 
Published: April 2004

AbstractIn the injection molding of substrates for optical discs, precise transcription of the pits and grooves is imperative. In particular, for high density optical discs, molding transcription of minute grooves with widths on the sub‐micron level is required. In this study, in order to quantitatively clarify the relationship between the molding conditions, molding resins, and the transcription, the transcription of minute rectangular grooves (width 0.55 μm, depth 70 nm) by injection molding was studied. Polycarbonate, amorphous polyolefin, and Polymethylmethacryrate resins were employed. A transcription model for the minute groove utilizing the concept of the equivalent thickness of the vitrified layer was introduced, and the relationships between the molding conditions, resin properties, and the transcription heights were verified. Among these resins, amorphous polyolefin, which has the lowest elastic modulus, indicated the highest transcribability.
Carbon black–filled immiscible blends of poly(vinylidene fluoride) and high density polyethylene: Electrical properties and morphology
Authors: Feng Jiyun , Chan Chi‐Ming 
Published: April 2004

AbstractThe electrical conductivity, current‐voltage characteristics and morphology of carbon black–filled immiscible blends of poly(vinylidene fluoride)(PVDF) and high density polyethylene (HDPF) were investigated. Carbon black (CB) had stronger affinity to HDPE than to PVDF, resulting in its selective localization in the HDPE phase. The CB content and PVDF/HDPE volume ratio were the two main factors influencing the electrical conductivity, current‐voltage characteristics, and morphology. At a fixed PVDF/HDPE volume ratio of 1/1, a percolation threshold of 0.037 volume fraction of CB was observed, and that value was much lower than that for conventional CB‐filled polymer composites. At a fixed CB content (10 wt% CB), a maximum electrical conductivity was observed at a PVDF/HDPE volume ratio of 2.75. An increase in CB content in the composites with a fixed PVDF/HDPE volume ratio (1/1) and an increase in PVDF content in composites with a fixed CB content (10 wt%) greatly decreased the domain size of the PVDF phase. A positive‐temperature‐coefficient effect was used to determine the location of CB in the blends.
Diffuse reflectance and transmittance of IR absorbing polymer film
Authors: Ho Wen‐Dar , Ma Chen‐Chi M. , Wu Lieh‐Chun 
Published: April 2004

AbstractThis study employs the ray tracing method to analyze and develop mathematical formulae for the internal reflectance of a free standing thick polymer film. The proposed formulae are then used to simulate the diffuse reflectance and diffuse transmittance. Analysis results indicate that internal reflectance is not a constant and varies with film thickness and absorption property. Internal reflectance of the front surface (irradiated surface) surpasses that of the back surface. In addition, all the internal reflectances decrease with the film thickness and the absorption property. In light of the measured thickness and experimentally determined diffuse transmittance of a polymer film, the extinction coefficient to diffuse IR irradiation can be obtained by interpolating in the graphs provided in this study.
Functionalization of ethylene‐propylene‐diene terpolymer via the alder ene reaction
Authors: Thompson M. R. , Tzoganakis C. , Rempel G. L. 
Published: April 2004

AbstractAn ethylene‐propylene‐diene rubber (EPDM), containing 5 wt% 5‐ethylidene‐2‐norbornene, was functionalized with maleic anhydride through the Alder Ene reaction at temperatures above 200°C in a co‐rotating twin screw extruder. Characterization of the maleated product included FT‐IR, 1H and 13C NMR, and GPC. The degree of functionalization was determined by infrared analysis and by the mechanical properties of an ionic network formed by neutralizing the maleated rubber with zinc oxide. Increased temperature and maleic anhydride reactant concentration were found to improve the extent of reaction. Several Lewis acid species (SnCl2•2H2O, RuCln•xH2O and AlCl3) were tested as catalysts, and they were found to have a small effect on the degree of functionalization. This effect improved with reduced acid concentration. Among the Lewis acids examined, AlCl3 gave rise to the greatest improvement of succinyl anhydride incorporation into the rubber.
A quantitative analysis of low density polyethylene and linear low density polyethylene blends by differential scanning calorimetery and fourier transform infrared spectroscopy methods
Authors: Prasad A. 
Published: April 2004

AbstractBlends of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) are widely used for blown film applications. An accurate and rapid test scheme to identify the type and composition of α‐olefin in LDPE/LLDPE blends has been developed that utilizes differential scanning calorimetery (DSC) and Fourier transform infrared (FTIR) spectroscopy techniques. The melting point of LDPE varies with density and usually is in the range of 106°C to 112°C for film grade resins. The DSC thermogram of LLDPE is characterized by a broad range of melting peaks with a lower melting peak around 106°C to 110°C and a higher one in the range of 120°C to 124°C. In a blend with LDPE, the ratio of the two endothermic peak heights changes. At a given weight percent of LDPE, this ratio depends on the type of LLDPE (i.e., the comonomer used). Separate calibrations for butene‐1, hexene‐1, and octene‐1 LLDPEs have been developed to quantify the blend composition from DSC thermograms where the α‐olefin type is successfully identified by FTIR over the entire blend composition range. The calibration curves are applicable to narrow melt index (MI) and density range conventional film grade LDPE and LLDPE resins and are not intended to be used for the metallocene type LLDPEs.
Profile control of plastic sheet in an industrial polymer processing process
Authors: Liang Yue , Kurihara Kazurou , Saito Kunio , Murakami Hiroyasu , Kumagai Kunio , Ohshima Masahiro , Tanigaki Masataka 
Published: April 2004

AbstractA control system was developed using a two‐degree of freedom control structure with four input variables in the feedforward, and two inputs, the screw rotation speed and the gap of the forming roller, in the feedback loop. The feedforward signals were predetermined from first principles and the operators' heuristic rules for each changeover operation and prepared in a database. At the end of each changeover operation, the values in the database were rewritten by evaluating control performance. The magnitude of the true dead time changed as the production rate was changed. The rate of sampling and control action in the feedback control was adapted in each changeover operation so that the changing time delay was always expressed by a one‐sampling‐step time delay in the discrete models and dealt with by the controller robustness against parameter uncertainty. The developed control system was applied to an actual industrial plastic sheet production line and allowed one to easily perform the changeover operation and reduce material consumption.