bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of the three‐dimensional orientation distribution of glass fibers in injected isotactic polypropylene
Authors: Avérous Luc , Quantin Jean Christophe , Crespy Alain , Lafon Dominique 
Published: April 2004

AbstractThe mechanical properties of fiber reinforced thermoplastics depend on the characteristics of the fibers, such as their three‐dimensional orientation distribution, which is the result of the processing conditions and of the initial products before mixing. Different composites were obtained by injection of reinforced isotactic polypropylene containing 30 wt% fibers. Different size distributions of fibers were investigated. Their average lengths range from 60 to 470 μm. Specific new tools were developed by combining microscopy and image analysis to determine the microtextural characteristics of the fibers, such as their size distribution or their orientation in the matrix. Our technique allows the following of the size distribution evolution of the fibers as the composite is processed. The three‐dimensional orientation of the fiber is established using the in‐plane angle and the angle of inclination. The evolution of the three‐dimensional orientation distribution is studied in the sample, by differentiating central and border behavior and also as a function of fiber size. It is concluded that the coupling of scanning electronic microscopy with image analysis is an interesting technique that allows the 3‐D orientation of the fibers to be determined. This technique is validated by showing that the results obtained agree with those that other authors obtained on comparable materials.
Novel structures by microlayer coextrusion—talc‐filled PP, PC/SAN, and HDPE/LLDPE
Authors: Mueller Chad D. , Nazarenko Sergei , Ebeling Thomas , Schuman Thomas L. , Hiltner Anne , Baer Eric 
Published: April 2004

AbstractNumerous examples in the literature illustrate how the coextrusion of film with three or more polymeric layers is economically used to achieve a desirable mix of end‐use characteristics. More recently, layer‐multiplying devices permit two polymers of widely dissimilar solid‐state properties to be combined into unique microlayer and nanolayer structures with hundreds or thousands of alternating layers. If the layers are thin enough, the key properties of the constituents can combine synergistically. The microlayer structure is also an effective research tool. Because the microlayer and nanolayer structures contain large specific interfacial areas, they are ideal for fundamental studies of phenomena such as interdiffusion and adhesion. Three examples of microlayered materials with up to 1024 layers illustrate the versatility of this coextrusion process: talc‐filled PP, PC/SAN, and HDPE/LLDPE.
Structures and tensile properties of a magnetically and mechanically oriented liquid crystalline copolyester, Xydar
Authors: Kossikhina S. , Kimura T. , Ito E. , Kawahara M. 
Published: April 2004

AbstractA wholly aromatic thermotropic liquid crystalline copolyester consisting of p‐hydroxybenzoic acid, terephthalic acid, and p,p′‐biphenol, one from the Xydar series, was aligned by means of magnetic fields and mechanical methods. The tensile properties of these samples were different depending on the orientation degree and the means used for the orientation. Magnetically oriented films exhibited lower elastic modulus and ultimate tensile strength than mechanically oriented films of the same orientation degree, but the elastic modulus of magnetically oriented films was comparable to that of the mechanically stretched films of lower orientation degrees. This suggests that magnetic fields could be used as an additional means of controlling the orientation of thermotropic liquid crystalline copolyesters during molding or film fabrication. The difference in tensile properties was discussed in relation to the oriented structures examined by scanning electron microscopy, polarizing microscopy, and wide angle X‐ray measurement.
Nonlinear mechanical response of high density polyethylene. Part I: Experimental investigation and model evaluation
Authors: Zhang Chuntao , Moore Ian D. 
Published: April 2004

AbstractThe nonlinear behavior of high density polyethylene (HDPE) is investigated for samples cut from thick‐walled HDPE pipe. Extensive experimental work has been performed to characterize the non‐linear time‐dependent response of the material tested under uniaxial compression. Tests were conducted under conditions of constant strain rate, creep, stress relaxation, constant loading rate, abrupt change of strain rate, creep‐recovery, cyclic strain rate, and various combinations of these loading conditions. Creep and stress relaxation response after strain reversal and the effect of the transient response on the following stress‐strain behavior is examined. Permanent strains for the test specimens and their dependence on loading histories are investigated. Specimens cut at various orientations from the pipe are used to quantify the small amounts of local anisotropy in the pipe specimen. The experimental work has been used to develop both nonlinear viscoelastic (NVE) and viscoplastic (VP) constitutive models in a companion paper. Both the test results and the corresponding model predictions are reported in this paper. It is found that the VP model reproduces the nonlinear viscoelastic‐viscoplastic behavior of HDPE very well provided that the current strain is not below the maximum strain imposed (there is no strain reversal). The NVE model predicts the material behavior reasonably well for some loading conditions, but inadequately for others.
Effects of diffusional water removal and heat transfer in nylon 6 reactors
Authors: Ahn Young‐Cheol 
Published: April 2004

AbstractThe effects of diffusional water removal and heat transfer on the polymerization of ε‐caprolactam were investigated by solving the systems of differential mass and energy balance equations using a finite difference method. Two types of contacting scheme between inert gas and reaction mass have been chosen for study. One is a hollow sphere system and the other is a wetted‐wall type hollow cylinder system. The reaction system was designed to be in equilibrium with respect to monomer conversion. The interfacial area per unit volume and the diffusional depth have profound effects on the water content and the temperature of the reaction mass, and consequently on the molecular weight of the polymer produced. Larger interfacial area per unit volume and smaller diffusional depth lead to a higher rate of water removal and heat transfer. In case of larger interfacial area per unit volume, the higher interfacial temperature gives rise to higher molecular weight polymer. For the interfacial area per unit volume of 26.67 m2/m3, the number average chain length reaches as high as 277 and the polydispersity as high as 2.06 when the interfacial temperature is 270°C. The heat transfer greatly affects the content of cyclic dimer in the product so that the hollow cylinder type reactor is preferred, because it is easier to control the temperature of the later portion of the reactor.
The working domain in reactive extrusion. Part I: The effect of the polymer melt viscosity
Authors: van der Goot A. J. , Hettema R. , Janssen L. P. B. M. 
Published: April 2004

AbstractThis article describes the radical copolymerization of styrene (St) and n‐butyl‐methacrylate (BMA) in a counter‐rotating twin‐screw extruder. In order to investigate the effect of the polymer melt viscosity on the working domain in reactive extrusion, the copolymer was crosslinked with different amounts of divinylbenzene (DVB). Crosslinking of the polymer resulted in a higher polymer melt viscosity. It was demonstrated that not only the product properties but also the process characteristics were strongly influenced by the addition of divinylbenzene to the reaction mixture. The product properties changed as expected: more crosslink agent led to a higher molecular weight or an increase in gel fraction, and a much higher melt viscosity of the polymer. Besides these effects on the product properties, the addition of DVB resulted in a more stable process, leading to an enlarged working domain.
The working domain in reactive extrusion. Part II: The effect of the polymerization rate
Authors: van der Goot A. J. , Klaassens S. A. , Janssen L. P. B. M. 
Published: April 2004

AbstractThis article describes the influence of the polymerization rate on the working domain of a counter‐rotating twin‐screw extruder used as a polymerization reactor. The rate of polymerization was varied by changing the maleic anhydride (Mah) content in the feed, which consisted of styrene, n‐butylmethacrylate, and maleic anhydride. It appeared that the Mah content influenced the operating window of the extruder. Higher Mah percentages resulted in higher throughputs and a decreased dependence on the extruder parameters. On the basis of these results, a new theory concerning reactive extrusion was developed, which resulted in a diagram that is useful in optimizing the extruder, when it is used as polymerization reactor. In addition to the effect of Mah on the process, its effect on product properties was studied.
Aliphatic/aromatic copolyester thermoset adhesives: Synthesis and characterization
Authors: Shi Frank F. , Economy James 
Published: April 2004

AbstractIn this paper, the synthesis and characterization of a new family of aliphatic / aromatic copolyester resins is described. This new resin is derived from a two component oligomeric system consisting of a mixture of Novolac acetates and several specially designed oligomers with carboxylic acid end groups. In this new material, aliphatic units have been incorporated into the oligomers in order to reduce the processing temperature. When used as an adhesive, the new resin offers good lap shear strength of about 14 MPa (2000 psi) at room temperature and retains useful properties to 80°C–100°C. This new system provides good thermal stability, environmental resistance and char yield of 25–40%.
Experimental study on distributive mixing characteristics of a new type of pin mixing section
Authors: Yao W. G. , Takahashi K. , Koyama K. , Dai G. C. 
Published: April 2004

AbstractTo eliminate two shortcomings of normal pin mixing sections, namely, the lack of efficient mixing mechanisms and the formation of dead spots, a new type of pin (pins channeled from top‐front to bottom‐rear) was previously proposed. As an experimental verification of the effectiveness of this type of pin, a dye decoloration experiment with a visual single screw extruder was carried out. The comparative experiments show that a “//” type pin mixing section (the orientation of holes in the pins is parallel) has the best mixing ability; a 45° angle between the projected line of orientation of holes in the pins and the screw axial line provides maximum mixing; however, a 45° angle between the orientation of the pin array and the screw axial direction results in poor mixing. The effect of density of the pins along the screw circumferential and axial direction on distribution mixing was also investigated experimentally.
Reactive extrusion of in‐situ composite based on PET and LCP blends
Authors: Hong Soon Man , Hwang Seung Sang , Seo Yongsok , Chung In Jae , Kim Kwang Ung 
Published: April 2004

AbstractThe “in‐situ” compatibilization for a PET/LCP blend via transesterification reactions in a twin‐screw extruder having a very short residence time is investigated through thermal, rheological, and mechanical studies. Inclusion of a small amount of liquid crystalline polymer (LCP) enhanced the crystallization rate of the poly(ethylene terephthalate) (PET) matrix. It acted as a nucleating agent. LCP lowered the blend viscosity above Tcn (crystalline‐nematic transition temperature), working as a processing aid. However, the addition of dibutyltindilaurate (DBTDL) as a reaction catalyst was found to increase the viscosity of the blends, diminish the size of the dispersed phase, enhance its adhesion with the matrix, and lead to an increase of mechanical properties of two immiscible phases. Hence DBTDL is helpful in producing a reactive compatibilizer by reactive extrusion at the interface of this polyester blend system. The optimum catalyst amount turned out to be about 500 ppm when the reaction proceeds in 90/10 PET/LCP polyester blend systems. Its effect on the mechanical properties is discussed in detail. The structural change of reactive blend was identified by H1 NMR and wide angle X‐ray diffraction patterns.
Investigation of composite materials selection and joint layout design to enhance EMI shielding of electronic equipment
Authors: Mottahed Behzad D. , Manoochehri Souran 
Published: April 2004

AbstractElectromagnetic shielding is a critical issue in the design of electronic equipment. This is mostly due to the high receptivity of electronic components to unwanted electromagnetic emission and interference. To reduce this interference, a study is initiated to determine the effect of material and joint types on the shielding effectiveness of an electronic enclosure. Eight different but progressively more complex joints are designed and investigated in this study. Filled polymers and metallized filled polymers are selected and compared with the all metallic structures. An analytical approach utilizing conformal mapping to calculate the shielding effectiveness of joints is attempted. An experimental apparatus is designed and manufactured to aid in finding the best possible joint configurations. Economic factors in selecting optimum joint layout are also studied. A cost index relating the effective length, design factors, and the total length of the part is developed. Results are presented for the best joint configuration and material with the highest shielding effectiveness.
The hot‐tool and vibration welding of acrylonitrile‐butadiene‐styrene
Authors: Stokes Vijay K. 
Published: April 2004

AbstractThermoplastic window frames are made by hot‐tool welding mitered, extruded profiles. The effects of weld process conditions on the strengths of hot‐tool butt joints are investigated for a grade of acrylonitrile‐butadiene‐styrene that was specially developed for window‐frame applications. Vibration‐weld strength data, obtained on a research machine in which all the process variables can be independently controlled, are used to benchmark strengths of hot‐tool welds made on a commercial welding machine. Process differences between hot‐tool butt welding and the hot‐tool welding of mitered, extruded profiles are discussed.
Welding of thermoplastics reinforced with random glass mat
Authors: Gehde Michael , Giese Michael , Ehrenstein Gottfried W. 
Published: April 2004

AbstractThermoplastics reinforced with random glass mat have high strength and stiffness; the fibers dominate the mechanical behavior of these composites. The results of this investigation have shown that fibers are ineffective for reinforcing hot‐tool and vibration welded butt welds. The maximum weld strengths attained with GMT are comparable to the strengths of good welds of the unfilled material. The optimum hot‐tool welding parameters for the reinforced materials are different from those for the unfilled material. Unfilled polypropylene is easier to weld than unfilled polyamide. This characteristic is also true of the reinforced materials. In vibration welding, high welding pressures and high amplitudes result in lower mechanical properties. The optimum penetration depends on the fiber content of the bulk material. This penetration dependence is different from that for unfilled thermoplastic, for which the mechanical properties are independent of the penetration once a steady state has been attained.
Friction welding of polyamides
Authors: Potente H. , Uebbing M. 
Published: April 2004

AbstractResults from different experiments on friction welding are used to characterize the behavior of polyamide over a wide range of welding conditions. Several types and grades of polyamide were joined using the vibration and spin welding processes. The quality of the welds was evaluated by short time tensile tests and microscopy. In addition to the geometry of the parts being joined, the process parameters and the material were found to affect the quality of the weld, so that associated with each application is a different set of optimum welding parameters.
Evaluation of thermodynamic theories to predict interfacial tension between polystyrene and polypropylene melts
Authors: Kamal M. R. , Demarquette N. R. , Lai‐Fook R. A. , Price T. A. 
Published: April 2004

AbstractThe commonly used thermodynamic theories (mean field theory and the square gradient theory) to predict interfacial tension between polymers have been modified. The results of these theoretical developments have not yet been fully tested and compared to experimental data. In this paper, experimental data for the effects of temperature, molecular weight, and molecular weight dispersity on interfacial tension for polypropylene/polystyrene polymer pairs are compared with the predictions of the new versions of the above theories. To evaluate these theories, it is necessary to know the Flory‐Huggins interaction parameter for the polymer pairs studied. The relation correlating the Flory‐Huggins interaction parameter to the Hildebrand solubility parameter was not suitable for evaluating the theoretical predictions of interfacial tension. Instead, the Flory Huggins interaction parameter was expressed as the sum of an enthalpic contribution, χH, and entropic contribution, χs. In the absence of reliable experimental values, a method was developed to evaluate the two contributions, based on interfacial tension data. The procedure provided an interaction parameter that is allowed to depend on molecular weight. When this approach was used, the predictions of only the new version of the square gradient theory were in good agreement with the experimental data for the influence of temperature and molecular weight on interfacial tension. However, the theory predicted the effect of polydispersity on interfacial tension only at high temperatures.
Effects of flow induced orientation of ferromagnetic particles on relative magnetic permeability of injection molded composites
Authors: Fiske Thomas , Gokturk Halit S. , Yazici Rahmi , Kalyon Dilhan M. 
Published: April 2004

AbstractComposite samples consisting of ferromagnetic asymmetric particles incorporated into a polyolefin binder were injection molded using custom designed molds which produced preferential fiber orientations. The relative magnetic permeability values of the composites were measured as a function of the filler volume fraction, injection rate, gate diameter, temperature, aspect ratio of the fibers, and fiber orientation. Fiber orientation was affected by the molding conditions and controlled the relative magnetic permeability of the composites. The degree of fiber orientation was significantly affected by the size of the opening (gate) to the mold, or by the mold geometry going from an edge‐gated cylindrical to a center‐gated disk cavity. Relative permeability values of the composites were observed to increase when the fiber orientation and the applied field were parallel to one another. For instance, highly aligned composite samples exhibited up to 30% greater relative permeability values compared to those samples which exhibit fiber orientation distributions approaching a random distribution. To our knowledge this is the first study that provides data linking the fiber orientation distribution functions of ferromagnetic asymmetric particles to the relative magnetic permeability values of injection molded composites.
Transesterification reaction of polyarylate and copolyester (PETG) blends
Authors: Oh Taeg Su , Ryou Jin Ho , Chun Yong Sung , Kim Woo Nyon 
Published: April 2004

AbstractTransesterification reactions between polyarylate (PAr) and a copolyester (PETG) have been investigated by proton nuclear magnetic resonance (NMR), Fourier‐transform infrared spectroscopy (FTIR), and differential scanning calorimetry. Blends of PAr and PETG were prepared by melt mixing and solution‐casting with weight fractions of PAr in the blends varying from 0.90 to 0.10. The PETG is a copolyester containing ethylene‐1,4‐cyclohexylene dimethylene terephthalate. From the thermal analysis of the PAr/PETG melt blends, a single glass transition temperature is observed, which indicates a miscibility between the PAr and PETG. The benzene insoluble fraction of the PAr/PETG (50/50) melt blends and solution‐cast blends were characterized using NMR and FTIR. The results of NMR and FTIR support the conclusion that transesterification reactions between the PAr and PETG occurred under the melt blending conditions applied.
Impact grinding of thermoplastics: A size distribution function model
Authors: Green Janet L. , Petty Charles A. , Grulke Eric A. 
Published: April 2004

AbstractSeparation of poly(ethylene terephthalate) (PET) from poly(vinyl chloride) (PVC) is an important problem when recycling bottles and other consumer products. Previous work has identified a processing window for the selective grinding of a mixture of PET and PVC. Impact grinding for conditions within the processing window will ensure that one polymer fails in the ductile mode and the other fails in the brittle mode, giving differences in sizes and shapes between the ground polymers. The ground mixture can be separated by physical means such as screening. This study develops size distribution models for the impact grinding of PET and PVC chips, an important tool for the operation and control of a selective grinding process. The distribution coefficients can be related to grinding conditions, and to the failure mechanism of the polymer.
Antioxidant diffusion in polyethylene hot‐water pipes
Authors: Viebke J. , Gedde U. W. 
Published: April 2004

AbstractThis paper presents oxidation induction time (OIT) data for samples taken from a range of polyethylene hot‐water pipes before and after hydrostatic pressure testing with internal stagnant water and external air. Linear relationships between OIT and antioxidant concentration were established for the antioxidants/polymers used. A model assuming Fickian diffusion of the antioxidant to the surrounding media and chemical consumption of the antioxidant (Regime B model) was applied to the OIT‐profile data. The Regime B model was successfully applied to OIT‐profile data except for in the case of a pipe with a substantial scatter in the OIT data, indicative of compositional heterogeneity. The choice of initial conditions for the modeling was critical. The use of initial conditions based on insufficiently exposed pipes led to an overestimate of the diffusivities caused by the combined action of Regimes A (internal precipitation) and B loss mechanisms. The time period associated with Regime A constituted up to 25% of the lifetime for the pipes studied. Antioxidants with sterically accessible polar groups showed a higher melting point and greater interaction with dissolved water and carbon black. Obtained radial dependences of the antioxidant diffusivities (D) indicate that the water concentration in the polymer influenced D primarily through cluster formation involving water and antioxidant molecules and by competition between water and antioxidant molecules about adsorption sites on carbon black particles and to a much lesser extent by plasticization. Antioxidant concentration profiles calculated for the failure time interval in pressure testing appeared in the same concentration range, and fracture initiation occurs in the regions in the pipe wall first reaching depletion of the antioxidant system.