bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen plasma treatment of sisal fibers and polypropylene: Effects on mechanical properties of composites
Authors: Couto Elisete , Tan Ing Hwie , Demarquette Nicole , Caraschi Jose Claudio , Leão Alcides 
Published: April 2004

AbstractPolypropylene powder and sisal fibers were oxygen plasma treated, and the mechanical properties of their composites were tested. Two main effects were investigated: the incorporation of oxygen polar groups in the polypropylene surface and the surface degradation and chain scission of both polypropylene and sisal fibers. Prior to these treatments, three reactor configurations were tested to investigate the best condition for both effects to occur in PP films. Results showed that polypropylene‐cellulose adhesion forces are about an order of magnitude higher for PP film treatments at 13.56 MHz than at 40 kHz owing to much higher chain scission at lower frequencies, although it probably also occurs at high frequency and high power. Polypropylene powder treated with oxygen plasmas in optimum conditions for polar group incorporation did not result in improvement in any composite mechanical property, probably owing to the polymer melting. Sisal fibers and PP powder treated in conditions of surface degradation did not improve flexural or tensile properties but resulted in higher impact resistance, comparable to the improvement obtained with the addition of compatibilizer.
Recycling of poly(ethylene terephthalate) as polymer‐polymer composites
Authors: Evstatiev M. , Fakirov S. , Krasteva B. , Friedrich K. , Covas J. A. , Cunha A. M. 
Published: April 2004

AbstractMicrofibrillar reinforced composites (MFC) comprising an isotropic matrix from a lower melting polymer reinforced by microfibrils of a higher melting polymer were manufactured under industrially relevant conditions and processed via injection molding. Low density polyethylene (LDPE) (matrix) and recycled poly(ethylene terephthalate) (PET) (reinforcing material) from bottles were melt blended (in 30/70 and 50/50 PET/LDPE wt ratio) and extruded, followed by continuous drawing, pelletizing and injection molding of dogbone samples. Samples of each stage of MFC manufacturing and processing were characterized by means of scanning electron microscopy (SEM), wide‐angle X‐ray scattering (WAXS), dynamic mechanical thermal analysis (DMTA), and mechanical testing. SEM and WAXS showed that the extruded blend is isotropic but becomes highly oriented after drawing, being converted into a polymer‐polymer composite upon injection molding at temperatures below the melting temperature of PET. This MFC is characterized by an isotropic LDPE matrix reinforced by randomly distributed PET microfibrils, as concluded from the WAXS patterns and SEM observations. The MFC dogbone samples show impressive mechanical properties—the elastic modulus is about 10 times higher than that of LDPE and about three times higher than reinforced LDPE with glass spheres, approaching the modulus of LDPE reinforced with 30 wt% short‐glass fibers (GF). The tensile strength is at least two times higher than that of LDPE or of reinforced LDPE with glass spheres, approaching that of reinforced LDPE with 30 wt% GF. The impact strength of LDPE increases by 50% after reinforcement with PET. It is concluded that: (i) the MFC approach can be applied in industrially relevant conditions using various blend partners, and (ii) the MFC concept represents an attractive alternative for recycling of PET as well as other polymers.
Numerical analysis of polymer melt flow in the nipping region
Authors: Takase M. , Katsumoto R. , Kegasawa T. , Kihara S. , Funatsu K. 
Published: April 2004

AbstractIn the extrusion coating process, it has never been revealed how a polymer melt flows near the nipping region and how the cooling process occurs. We created a numerical simulation program for the polymer melt flow near the nipping region using the finite element method. Numerical results showed the effects of many individual factors (e.g. line speed, melt thickness, extrusion temperature, shear‐thinning property, etc.) on the cooling process and polymer melt flow near the nipping region. It was found that a polymer melt buildup that can be observed between two calender rolls in the sheet forming process also formed in the extrusion coating process, and that the amount of polymer melt buildup (bank) depended upon the coating condition. It was found that not only line speed and melt thickness contribute to the extrusion coating process significantly, but also the rheological property has an effect on the process.
Modeling of structural reaction injection molding. Part II: Comparison with experimental data
Authors: Polushkin Evgeny Yu. , Polushkina Olga M. , Malkin Alexander Ya. , Kulichikhin Valery G. , Michaeli Walter , Kleba Ingo , Blaurock Jochen 
Published: April 2004

AbstractA flow channel for experimental modeling of the structural reaction injection molding (SRIM) process, for producing composites with a sandwich‐like structure, has been designed and constructed. It consists of a thin rectangular box, in which the reinforcing glass fabrics with different permeabilities are positioned parallel to each other. The core layer is a thick, porous mat. Location of the other denser and thinner reinforcing materials into the flow channel was symmetrical with respect to the spacer mat. The channel has transparent walls for observing propagation of the impregnation front in the spacer mat and in the reinforcing dense layers. Development of the impregnation front during filling the flow channel and the pressure profile in the gate were measured for non‐foaming reactive polyurethanes. Enough good correspondence between the calculated and experimentally observed flow front position and pressure profiles was obtained.
Chemical modification of polyurethane for two‐component injection molding
Authors: Bräuer M. , Hupfer B. , Nagel J. , Lehmann D. 
Published: April 2004

AbstractA thermoplastic polyurethane (TPU) was modified by reactive processing with 4,4′‐diphenylmethane diisocyanate (MDI). The use of this modified polyurethane was investigated for improved adhesion in composites with polyamide 6 (PA 6). Specimens were prepared by two‐component injection molding. With the modified polyurethane the tensile bond strength could be increased by about 50%. An insoluble and inseparable polyurethane residue on the PA 6 fracture surface found by ATR‐FTIR spectroscopy gave evidence of chemical bonding between PA 6 and TPU. Allophanate bonds were formed by the chemical modification. These groups functioned as an inert source of highly reactive isocyanate groups. Urea groups, the polyurethane chain were formed by the modification, too. These groups may improve the compatibility between the two components. A change in the morphology of the polyurethane was observed, which was caused by the change in molecular structure by the chemical modification. The high level of bond strength may be due to a combination of these phenomena.
Development of orientation and mechanical properties of extrusion cast polyamide 11 films in biaxial stretching process
Authors: Rhee Sangkeun , White James L. 
Published: April 2004

AbstractThe development of orientation of extrusion cast polyamide 11 films in the biaxial stretching process was studied with birefringence and wide angle X‐ray diffraction (WAXD) pole figures. White‐Spruiell biaxial orientation factors of the crystalline phase were calculated with the pole figure data. Both biaxially stretched films were developed. Planarity of hydrogen bonding planes with respect to the film surface was observed from WAXD pole figures. Mechanical properties of the films were studied. Tensile strength and elongation at break were successfully correlated with the out‐of‐plane birefringences.
Numerical investigation of continuous processes for catalytic hydrogenation of nitrile butadiene rubber
Authors: Pan Qinmin , Rempel Garry L. , Ng Flora T. T. 
Published: April 2004

AbstractDynamic behavior of continuous processes was numerically investigated for the catalytic hydrogenation of nitrile butadiene rubber, based on developed models, which took into account the coupling between kinetics and mass transfer. The evolution of hydrogenation reaction trajectories in both cases were analyzed. It is proposed that the coupling behavior between the catalytic hydrogenation and mass transfer was completely determined by the ability of the catalyst in activating hydrogen, carbon‐carbon double bond loading level and the relative capacity of reaction to mass transfer as well as the residence time in the reactor. Four dimensionless parameters were derived to characterize these aspects. The effects of operation conditions on the hydrogenation processes were investigated. The application of the ideal flow models to non‐ideal flows was in addition discussed. It is suggested that the optimal reactor for such a hydrogenation system would be a plug flow reactor with an instantaneous well‐mixing component in the inlet of it, and a reasonable approach to the proposed optimal reactor should be with the flow behavior of at least three continuous stirred tank reactors in series. Further research directions are suggested.
Modification of porous suspension‐PVC particles by stabilizer‐free aqueous dispersion polymerization of absorbed monomers
Authors: Shach‐Caplan M. , Narkis M. , Silverstein M. S. 
Published: April 2004

AbstractThe modification of porous PVC particles by an in‐situ stabilizer‐free polymerization/crosslinking of a monomer/crosslinker/peroxide solution absorbed within the PVC particles is presented. The modifying crosslinked polymers are polystyrene (PS) crosslinked with DVB (divinyl benzene), polymethyl methacrylate (PMMA) crosslinked with ethylene glycol dimethacrylate (EGDMA), and styrene‐MMA copolymer crosslinked with DVB. The modified PVC particles characterization includes polymerization yield, non‐extractables, 13C solid‐state CPMAS NMR, porosity measurements and also morphology and dynamic mechanical behavior (DMTA). The levels of nonextractable fractions found and 13C solid‐state CPMAS NMR results are indicative of low chemical interaction in the semi‐IPN PVC particles. Particle porosity levels and SEM observations indicate that styrene and MMA mainly polymerize within the PVC particles' bulk and just small amounts in the pores. MMA polymerization in the PVC pores is as crusts covering the PVC pore surfaces, whereas styrene polymerization in the PVC pores is by filling the pores. Dynamic mechanical studies show that tanδ and the storage modulus curves are influenced by the incorporation of PS and XPS but not by the incorporation of PMMA and XPMMA.
Flow patterns and mixing mechanisms in the screw mixing element of a co‐rotating twin‐screw extruder
Authors: Ishikawa Takeshi , Amano Tarou , Kihara Shin‐Ichi , Funatsu Kazumori 
Published: April 2004

AbstractNon‐Newtonian and non‐isothermal flow simulations based on 3‐D FEM were applied to a special and conventional elements of a twin‐screw extruder. The screw mixing element (SME), a kind of special element, was a distributive mixing promoter consisting of a standard screw profile with slots cut across the flight tip to increase leakage flow. The full flight screw (FF) and the kneading block (KB) were examined as conventional elements in order to contrast the mixing behavior with the SME. The accuracy of numerical results was verified by experimentally measuring pressure and temperature. Additionally, marker particle tracking analysis was carried out to evaluate the distributive and dispersive mixing. Using the above analyses, the following results were obtained: The pumping capability of the SME was smaller than that of the FF and was the same as for the KB. The SME suppressed heat generation and showed the lowest temperature distribution of the three elements. For distributive mixing, the SME showed the best performance judging from the mixing coefficient G, residence time distribution, and area stretch distribution based on a laminar mixing mechanism. A higher rotational speed achieved better distributive mixing performance. For dispersive mixing defined by stress distribution, the SME showed the second best performance next to the KB. It also showed better dispersive mixing performance with increasing rotational speed. The SME had the advantages of low heat generation and good distributive mixing.
Effect of a compatibilizer on the structural development of a thermotropic liquid crystalline polymer/polystyrene blend
Authors: Seo Yongsok , Kim Hyong‐Jun , Kim Youngjun , Rhee Hee Woo 
Published: April 2004

AbstractA fine fibril structure of a thermotropic liquid crystalline polymer (TLCP, a poly(ester amide)) can be developed in a shear flow field of a thermoplastic matrix (polystyrene, PS). Addition of a third component, a poly(styrene‐co‐maleic anhydride) (SMA), that interacts with the thermotropic liquid crystalline polymer facilitates the structural development of the TLCP phase by acting at the interface. Moreover, it brings about good adhesion at the interface and enables the dispersed liquid crystalline polymer phase to be deformed in shear flow without strong elongation even though the viscosity of the matrix is much lower than that of the liquid crystalline polymer. The mechanical properties were substantially improved because of both the good adhesion at the interface and fibril generation, which were ascribed to the SMA interaction. These results have important implications in that they provide a means to produce strong and tough in‐situ composites when the viscosity of the matrix polymer is lower than that of the dispersed liquid crystalline polymer which is immiscible with the matrix polymer. Morphological observations determined the significance of the third component (SMA) in immiscible polymer blends, and an optimum amount of SMA exists for best mechanical performance.
Miscibility evolution of polycarbonate/polystyrene blends during compounding
Authors: Chuai C. Z. , Almdal K. , Johannsen I. , Lyngaae‐Jørgensen J. 
Published: April 2004

AbstractThe miscibility evolution of polycarbonate/polystyrene (PC/PS) blends during the compounding process in three blending methods of industrial relevance, namely melt blending, remelt blending in a twin‐screw extruder and third melt blending in an injection molding machine, was investigated by measuring their glass transition temperatures (Tg) and their specific heat increment (ΔCp). Differential scanning calorimetry (DSC) was used to examine nine blend compositions. Shifts in glass transition temperature (Tg) of the two phases in melt‐mixed PC/PS blends suggest partial miscibility of one polymer in the other. The observed solubility strongly depends on blend composition and blending method. The Tg measurements showed maximum mutual solubility around 50/50 composition. The miscibility of PC/PS blended after the third stage (melt injection molding) was higher than that after the first stages (melt extrusion) and the second stages (remelt extrusion).
High speed imaging of drop formation from low viscosity liquids and polymer melts in spinning disk atomization
Authors: Senuma Yoshinori , Hilborn Jöuns G. 
Published: April 2004

AbstractAn investigation of drop formation in a recently developed spinning disk atomization (SDA) technique is presented. In‐situ observations of drop formation at the disk rim, using a high speed imaging installation, are made. Atomizations covering two orders of magnitude in flow rate show that ligaments can also form at low flow rates. Sequences of pictures indicate that drops undergo a rotary motion as they detach from a ligament. In the direct drop regime, oscillating motions dominate. The effect of teeth shape at the disk rim on the resulting drops is compared. The effect on drop size and size distribution is found to decrease with increasing rotation rate and corresponding images are studied. Experiments with liquid viscosities ranging from 1 to 120 mPas reveal a fundamental difference in drop breakup, but a negligible change in drop size. Likewise, only a small effect of liquid density is detected. The surface tension's influence on the liquid spreading at the disk rim is described and the subsequent drop formation is qualitatively analyzed.
Tensile modulus of polymer nanocomposites
Authors: Ji Xiang Ling , Jing Jiao Kai , Jiang Wei , Jiang Bing Zheng 
Published: April 2004

AbstractBased on Takayanagi's two‐phase model, a three‐phase model including the matrix, interfacial region, and fillers is proposed to calculate the tensile modulus of polymer nanocomposites (Ec). In this model, fillers (sphere‐, cylinder‐ or plateshape) are randomly distributed in a matrix. If the particulate size is in the range of nanometers, the interfacial region will play an important role in the modulus of the composites. Important system parameters include the dispersed particle size (t), shape, thickness of the interfacial region (τ), particulate‐to‐matrix modulus ratio (Ed/Em), and a parameter (k) describing a linear gradient change in modulus between the matrix and the surface of particle on the modulus of nanocomposites (Ec). The effects of these parameters are discussed using theoretical calculation and nylon 6/montmorillonite nanocomposite experiments. The former three factors exhibit dominant influence on Ec. At a fixed volume fraction of the dispersed phase, smaller particles provide an increasing modulus for the resulting composite, as compared to the larger one because the interfacial region greatly affects Ec. Moreover, since the size of fillers is in the scale of micrometers, the influence of interfacial region is neglected and the deduced equation is reduced to Takayanagi's model. The curves predicted by the three‐phase model are in good agreement with experimental results. The percolation concept and theory are also applied to analyze and interpret the experimental results.
Studies of spinodal decomposition in a ternary polymer‐solvent‐nonsolvent system
Authors: Saxena Rahul , Caneba Gerard T. 
Published: April 2004

AbstractMuch of the work in modeling and computer simulation of spinodal decomposition has been done for binary systems. This work attempts to carry out the analysis of spinodal decomposition in ternary polymer‐solvent‐nonsolvent systems, where the solvent is the monomer used to produce the polymer and the nonsolvent is the major component. Various experimental methods are used to determine values of the parameters of the ternary version of the Cahn‐Hilliard equation of spinodal decomposition, such as cloudpoint experiments, time‐resolved light scattering in the ternary system, and morphological development of polymer membranes formed during the early stages spinodal decomposition. The combination of these experimental methods and computer simulation work shows the validity of the assumptions made in characterizing spinodal decomposition in ternary polymer systems of interest.
Mechanical performance of starch based bioactive composite biomaterials molded with preferred orientation
Authors: Sousa R. A. , Mano J. F. , Reis R. L. , Cunha A. M. , Bevis M. J. 
Published: April 2004

AbstractComposites of blends of starch with ethylene vinyl alcohol copolymer (SEVA‐C) filled with 10, 30 and 50% by weight (wt.) of hydroxyapatite (HA–the major inorganic constituent of human bone) were produced by twin‐screw extrusion (TSE) compounding. These composites were molded into tensile test bars using two molding techniques: (i) conventional injection molding and (ii) shear controlled orientation in injection molding (SCORIM). The bars produced were mechanically characterized by means of tensile testing and dynamical mechanical analysis (DMA). The structure of the moldings was assessed by wide‐angle X‐ray diffraction (WAXD) and the failure surfaces of the moldings analyzed by scanning electron microscopy (SEM). The enhancement of stiffness observed with HA reinforcement results partially from the stiffening effect of the blend associated with the decrease in plasticizer content during the compounding stage. SCORIM was able to further increase the stiffness of SEVA‐C/HA composites, allowing a maximum improvement of 12% for 30% wt. HA as compared to conventional molding. DMA results showed that the reinforcement of SEVA‐C causes the broadening of the relaxation peak of the polymer, suggesting a structural change within the starch fraction that may be related with thermal degradation of the polymer. The addition of HA particles reduces the preferred orientation exhibited by the SEVA‐C matrix, which is believed to limit the maximum mechanical performance that can be attained. Nevertheless, composites based on a biodegradable matrix with modulus above 7 GPa (in the bounds of the lower limit for human cortical bone) could be successfully produced.
Strain‐rate and temperature effects on the deformation of polypropylene and its simulation under monotonic compression and bending
Authors: Ohashi F. , Hiroe T. , Fujiwara K. , Matsuo H. 
Published: April 2004

AbstractMonotonic compressive loading and bending tests are conducted for solid polypropylene (PP) under constant or time‐varying strain‐rates and temperatures of 10, 25, 40°C. The observed compressive stress‐strain responses under constant conditions have revealed that the inelastic deformation behavior is remarkably dependent on loading rates and temperatures of normal use. The examination of such inelastic behavior has indicated that the strain‐rate effects correspond with the temperature effects based on the concept of time‐temperature equivalence. The viscoplastic constitutive theory based on overstress (VBO) has successfully reproduced the experimental responses with stress‐jumping phenomena using the equivalent time. Four‐point bending tests are performed under monotonic loading and holding for PP beams at three different temperatures. The observed deformation behavior has shown that the Bernoulli‐Euler hypothesis is valid. The VBO model and beam bending theory has generated the basic equations for PP beams, showing an analogy with the uniaxial one. In the numerical analysis, the equations are transformed into nonlinear ordinary differential equations with use of Gaussian quadrature for the spatial integrals. The comparison of numerical and experimental results has suggested some modifications for actually loaded moment taking the effect of deflection and friction into consideration. Finally, the numerical calculation has simulated the experimental time‐histories of curvatures fairly well.
Haze of polyethylene films—effects of material parameters and clarifying agents
Authors: Andreassen Erik , Larsen Åge , Nord‐Varhaug Katrin , Skar Merete , Øysæd Harry 
Published: April 2004

AbstractEffects of material parameters on the haze of blown films were analyzed. Four linearlow‐density polyethylenes (two metallocene grades and two Ziegler‐Natta grades) were studied in combination with three additives (two sorbitol‐based clarifying agents and a low‐molecular‐weight long‐chain branched polyethylene). One of the sorbitol‐based additives reduced the haze of both the metallocene materials in this study, but did not have any positive effect on the two Ziegler‐Natta materials. The variation in haze among the four base materials was directly related to the root‐mean‐square surface roughness (σ). When considering all 16 material/additive combinations, the link between haze and surface topography was not a simple σ‐haze relationship, but the haze was correlated with the average distance between adjacent surface profile peaks, the average slope, and the power spectral density at high lateral frequencies. Both of the mechanisms referred to in the literature, extrusion‐induced haze and crystallization‐induced haze, were probably active for the films in this study.