bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of dissolved gas on the viscosity of HIPS in the manufacture of microcellular plastics
Authors: Chong Tae‐Hyong , Ha Young‐Wook , Jeong Dae‐Jin 
Published: April 2004

AbstractThe microcellular plastics (MCPs) process is a foaming process that has been developed to reduce the weight of a product without significant changes to the mechanical properties. To apply microcellular plastics to mass production systems such as extrusion, injection molding, and blow molding, research must be done on material properties, such as viscosity, glass transition temperature, and melt index of polymer resin. Among the properties, it is critical to predict the change in viscosity with the amount of inert gas, which can be an index of the injection molding working condition of polymer resin. The purpose of this paper is to study the relationship between the amount of dissolved gas and the viscosity of high impact polystyrene (HIPS) resin in extrusion. The experiment was carried out with newly designed gas supply equipment and with a screw and die modified for MCPs. In addition, a pressure gauge was set up on the end of a barrel for measuring the pressure change. The experiment has shown that the viscosity of polymer decreases with increasing amounts of inert gas. A new model was applied to estimate the viscosity change as a function of the amount of dissolved gas.
Mechanical properties and structural characteristics of dynamically photocrosslinked PP/EPDM blends
Authors: Wang Weizhi , Wu Qianghua , Qu Baojun 
Published: April 2004

AbstractThe mechanical properties and crystal morphological structures of dynamically photocrosslinked polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) blends have been studied by mechanical tests, wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Dynamically photocrosslinking of PP/EPDM blends can improve the mechanical propertiess considerably, especially the notched Izod impact strength at low temperature. Data obtained from mechanical tests show that the notched Izod impact strength of a dynamically photocrosslinked sample with 30% EPDM at −20°C is about six times that of an uncrosslinked sample with the same EPDM component. The results from the WAXD, SEM, and DSC measurements reveal the enhanced mechanism of impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (i) the β‐type crystal structure of PP is formed and the interplanar distance of β‐type crystal increases slightly with an increase in the EPDM component; (ii) the droplet size of the EPDM phase in the photocrosslinked PP/EPDM blends is obviously reduced and the droplet number is increased with an increase in the EPDM component during the dynamical photocrosslinking process; (iii) the graft copolymer of PP‐g‐EPDM is formed at the interface between PP and EPDM components. All the above changes from the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of PP/EPDM blends at low temperatures.
A study of residence time distribution in co‐rotating twin‐screw extruders. Part II: Experimental validation
Authors: Poulesquen A. , Vergnes B. , Cassagnau P. , Michel A. , Carneiro O. S. , Covas J. A. 
Published: April 2004

AbstractIn the first part of this paper, a new approach to model the residence time distribution (RTD) in a co‐rotating twin‐screw extruder was proposed. It consists of coupling a continuum mechanics approach with a chemical engineering one, yielding an RTD curve without any fitting parameter. However, the choice of ideal reactors that depict the behavior of each particular profile is not evident. In this second part, we present an experimental study based on two types of extruder (Leistritz 30–34 and Clextral BC45), different screw profiles and two measurement techniques (off‐line and in‐line). Global, partial and local RTD curves were obtained, both experimentally and by means of a deconvolution technique. This series of experiments permitted the definition of the best association between ideal reactors and screw elements. Using this association, a comparison has been made between experimental results and theoretical calculations. A good agreement was generally obtained in terms of the RTD shape, delay time, mean residence time and variance.
Formation and properties of spontaneously polymerized fluorocoatings on aluminum
Authors: Zheng Haipeng , Davis Guy D. , Bell James P. 
Published: April 2004

AbstractSpontaneous polymerization (S‐Poly) is a novel process to form protective polymer coatings on aluminum and other metals. Here we discuss polymerization and coating properties when two fluorinated monomers are introduced into the S‐Poly system. The resulting coatings were characterized using attenuated total reflectance fourier transform infrared (ATR‐FTIR), differential scanning calorimetry (DSC), optical microscope and other measurements. Fluorinated coatings showed excellent dielectric properties and strong hydrophobicity. Their dry adhesion strength was a little lower than the coatings in previous systems, but changed very little after immersion in hot water for several days. Some of the fluorinated coatings exhibited significantly improved corrosion resistance in most corrosion tests.
Optimization of a batch reactor to produce the elastomeric copolyester prepolymer copoly(ethylene‐polyoxyethylene terephthalate)(CEPT)
Authors: De La Cruz‐Guerra Cornelio , Hernández‐Rivera Miguel A. , Cruz‐Gómez M. Javier 
Published: April 2004

AbstractA mathematical algorithm that optimizes the reactor to produce the elastomeric copolyester copoly(ethylene‐polyoxyethylene terephthalate), CEPT, is shown in this work. The optimization was carried out this way: First, an initial isothermal guess of temperature profile is made and the differential equtions system, which describes the CEPT production process, is solved, Second, the reaction time is fixed and the objective function is calculated. Third, the adjoint variable equations system is solved and the Hamiltonian's function is calculated. Fourth, a new temperature profile is found by using the control vector iteraction procedure. Finally, steps one to three are repeated until the objective function reaches a minimum value. The results of the optimization establish that the copolytransesterification reactor should be operated initially to high temperature (about 285°C), which should be reduced quickly to near 250°C to purposely diminish the production of by‐products.
Effect of interdiffusion regions on penetrant flux through multilayer films
Authors: Sankhe Shilpa Y. , Hirt Douglas E. , Zumbrunnen David A. 
Published: April 2004

AbstractBarrier properties of polymer films can be improved in various ways, such as formation of multilayer structures by coextrusion, surface treatment, and coatings. This work explores the use of thousands of alternating layers of polymer (xyxy…) to modify the resistance to permeation. A model is presented to predict the number of layers needed in a laminate to change the flux of a permeant by a given amount. An important feature of the model is the species transport across the interdiffusion regions at the polymer‐polymer interfaces where diffusivity of the penetrant, Di, is assumed to be a constant or a function of the volume fractions (ϕ) of the interdiffusing polymers. For constant Di, the modeling results show that increasing the number of interfacial regions decreases the flux for a given condition, and a large number of layers are required to achieve appreciable flux reduction. For ϕ‐dependent Di a balanced interdiffusion region was modeled in which the interdiffusing polymers were assumed to interpenetrate one another equally. In this particular case, the flux was predicted to always increase with the number of layers.
The effect of flame retardants on the hot‐plate welding of talc‐filled polypropylene
Authors: Oliveira M. J. , Bernardo C. A. , Hemsley D. A. 
Published: April 2004

AbstractThe effect of a flame retardant on the weldability of polypropylene with two different talc loadings was studied by microscopy and mechanical tests on hot‐plate welded injection molded tensile test bars. Welding changes the orientation of the talc particles, which align parallel to the weld interface, and can cause voiding of the material with a consequent decrease of weld strength. Welds of the material containing a flame retardant, which melts and volatizes at the temperatures used in welding, exhibited higher voiding and lower relative weld strengths on welding than the grade without a flame retardant. Voiding may be reduced using lower hot plate temperatures and higher welding displacements, but that results in an increase in the transverse orientation of the talc particles in the weld zone. The relative weld strength, which is affected by the composition of the material, was about 50% for the 20% talc‐filled polypropylene and about 45% for the 30% talc‐filled grade containing a flame retardant.
Plasma surface treatments of melt‐extruded sheets of poly(L‐lactic acid)
Authors: Hirotsu Toshihiro , Nakayama Kazuo , Tsujisaka Toshiyuki , Mas Andre , Schue Francois 
Published: April 2004

AbstractPoly(L‐lactic acid) sheets, prepared by melt extrusion, were treated with O2−, He−, and N2−plasmas generated in radio frequency (RF) at 13.56 MHz. Atmospheric pressure discharge at 20 kHz in helium was also applied to the modification of the sheets. The surface of the PLLA sheets was etched to form the characteristic morphology, and the patterns were different depending on the type of plasma. Polar groups composed of –COOH and –OH were incorporated by plasma treatment, and the surface became wettable. Surface modification became effective after a short treatment period, e.g., 30 seconds. Receding contact angles (θr) changed remarkably, and the surface properties were closely related to the increase in the surface energy of the polar contribution (γsp). Biodegradation of the poly(L‐lactic acid) sheets was not enhanced practically, even though the surface became hydrophilic after plasma treatment.
Verification of extensional viscosity effects in injection mold filling simulation
Authors: Moller James C. , Lee Daeyong 
Published: April 2004

AbstractThe effect of extensional viscosity upon wall pressure and front progression in injection molding is presented through experiments and simulations. In order to compare materials having distinctly different responses to extensional flow, unfilled and glass‐filled polypropylenes were examined. Wall pressure agreement was best with an extensional viscosity included in the simulation, particularly for the filled material. Pressure gradients were large enough to indicate significant density variations in the part at the end of filling, Examination of the test materials' viscoelastic properties indicates that extensional, rather than viscoelastic, effects predominate in the behaviors shown. Flow front progression was recorded by strobe photography. Results indicate that, when cavity thickness gradient is not aligned with the the direction of flow, there is disagreement among predictions and measurements. This is principally due to the violation of the Hele‐Shaw assumption that forms the basis for the simulation.
Development of a curvilinear viscoelastic constitutive relationship for time dependent materials. Part B: Example problems
Authors: Stephenson M. J. , Dargush G. F. 
Published: April 2004

AbstractThe boundary value problem of a two‐dimensional viscoelastic beam clamped at two ends and subjected to both a dead load and normal surface traction is solved using a finite element method here in Part B. The constitutive relationship between stress and strain developed in Part A uses a convected coordinate system and body tensor mathematics. Maxwell elements (springs and dashpots) describe the material for both fluid and solid characterizations. The overall finite element results calculated were physically reasonable. However, the assumed boundary conditions produce a stress singularity at the boundary, a singularity that is also seen in small deformation elastic theory.
Effect of curing temperature on the morphology of unsaturated polyester resin blended with poly(vinyl acetate)
Authors: Liu Chun‐Hsiu , Yu T. Leon , Chen Chih‐Cheng 
Published: April 2004

AbstractPhase separation of unsaturated polyester/styrene (UPE/styrene) resin blended with 5 and 10 wt% of poly(vinyl acetate) (PVAc) cured at various temperatures ranging from 75°C to 150°C was studied using low angle laser light scattering (LALS) and scanning electron microscopy (SEM). For UPE/styrene resin blended with 5 wt% PVAc cured at a temperature below 90°C, a discrete phase‐separated structure was observed. As curing temperature was raised above 90°C, SEM micrographs revealed that more and more cured UPE globules fused together with increasing curing temperature. The LALS intensity profile became broader with increasing curing temperature, indicating a less discrete phase‐separated structure at a higher curing temperature. As PVAc content was increased to 10 wt%, SEM micrographs revealed a co‐continuous phase‐separated structure. The LALS intensity decayed slowly from the center of the scattering pattern to a high scattering angle without the appearance of maximum scattering peak intensity. The morphology of the cured sample did not change too much with curing temperature for UPE/styrene resin blended with 10 wt% of PVAc.
Gas transport properties in chlorosulfonated polyethylene‐acrylate based adhesives
Authors: Tiemblo P. , Guzmán J. , Riande E. , Fernández A. , Bosch P. 
Published: April 2004

AbstractThe permeability and diffusivity properties of four gases—oxygen, nitrogen, carbon dioxide and methane—have been obtained for membranes prepared by the photocrosslinking of a mixture of chlorosulfonated polyethylene, acting as a binder, and a series of acrylic and methacrylic monomers. These measurements have been performed in the range 20°C to 50°C, and the activation energies have also been determined. These data are presented in comparison with those previously obtained in a crosslinked system in which the binder was not chlorosulfonated polyethylene but an aliphatic polyurethane. Both polymeric systems show similar permselectivities for the gas pairs O2/N2 (near 5) and CO2/CH4 (near 12), though overall permeability is about three times lower in the chlorosulfonated polyethylene—based polymer because of the smaller diffusion coefficients. The permeation and diffusion results are discussed in terms of the final structure of the photocrosslinked polymeric system, and it is concluded that it is the binder which is mostly responsible for the gas transport properties of these crosslinked materials.
Viscoelastic stress calculation in multi‐layer coextrusion dies: Die design and extensional viscosity effects on the onset of ‘wave’ interfacial instabilities
Authors: Zatloukal M. , Sáha P. , Vlček J. , Tzoganakis C. 
Published: April 2004

AbstractNon‐isothermal calculation of flow history‐dependent viscoelastic stresses in an annular coextrusion die is performed using the 8‐mode modified Leonov constitutive equation and the deformation rate field from finite element simulations. The study shows how the recently proposed total normal stress difference (TNSD) sign criterion, which quantifies the relative stretching of coextruded layers across an interface, can be used to investigate the role of the die design and elongational viscosities of coextruded materials from the point of view of interfacial instability. It is shown that both the die geometry and the elongational strain hardening have a crucial effect on the interfacial wave instability.
Toughness of nanoscale and multiscale polyamide‐6,6 composites
Authors: Nair Shanti V. , Goettler Lloyd A. , Lysek Bruce A. 
Published: April 2004

AbstractFracture initiation and fracture propagation toughening (R‐curve behavior) of polyamide 6,6 (PA‐66) polymers with different types of layered silicate clay having nanoscale (fully dispersed) or multiscale (mixed nanoscale/microscale) structure were studied. These results were compared to fracture data for conventional kaolin clay particulate reinforcements and a PA‐66 polyblend containing rubber and rigid poly(styrene‐co‐acrylonitrile) particulates. The stiffness increase due to the intercalated clay was the same as would be predicted by classical models for conventional elongated reinforcements at the same volume fraction level. The special benefit of the nanoscale reinforcement derived from their high surface area of contact with the matrix. Toughness in layered silicate clay composites was enhanced by better dispersion of the clay, by exfoliation of the clay layers, and by a stronger clay/matrix interface. A multiscale microstructure was found to be the more desirable microstructure, combining toughness from the nanodispersed clay with resistance curve behavior from the micrometer‐sized particulates. Fracture toughness was proportional to the crack‐tip plastic zone size at fracture, indicating that the clay reinforcements, by influencing shear deformation in the crack tip region, played an important role in promoting toughness. There was indirect evidence for the formation of a zone of damage within the crack‐tip plastic zone that could explain why toughness was not optimal.
The role of crystallinity and reinforcement in the mechanical behavior of polyamide‐6/clay nanocomposites
Authors: Bureau M. N. , Denault J. , Cole K. C. , Enright G. D. 
Published: April 2004

AbstractThe mechanical behavior of compression‐molded polyamide‐6 (PA6) reinforced with 2 wt% of organo‐nanoclay (montmorillonite intercalated with ω‐amino dodecanoic acid) has been studied and compared to that of PA6. The tensile strength and the Young's modulus of the PA6/clay were 15% higher than those of PA6. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and X‐ray diffraction showed that the crystalline structures of PA6 and PA6/clay differed considerably. A crystallinity of 25% with a dual structure composed of the γ and α forms was obtained in PA6/clay, while a crystallinity of 31% with the α form as the dominant crystalline structure was obtained in PA6. To understand the role of the crystalline structure of PA6, the molding process was modified to obtain PA6 specimens with different levels of crystallinity and different crystalline forms. Quenching molten PA6 at a cooling rate sufficiently high to prevent crystallization gave a material that was predominantly amorphous (crystallinity of 7%) with traces of the mesomorphic β or γ* form. Annealing this material at 80°C considerably increased crystallinity to 21%, which was also of the mesomorphic β or γ* form. PA6 with a predominant crystalline γ form could not be generated. Comparisons with PA6/clay in terms of crystallinity and mechanical behavior lead to the conclusion that the improvements in rigidity and strength observed when montmorillonite is added to PA6 are related to the reinforcing filler and not to a modification of the crystalline structure.
From polymer blends to in situ polymer/polymer composites: Morphology control and mechanical properties
Authors: Pesneau I. , Kadi A. Aït , Bousmina M. , Cassagnau Ph. , Michel A. 
Published: April 2004

AbstractIn situ polymer/polymer short fiber composites were generated by a two‐step process. In the first step, a polyamide (PA) dispersed phase is blended with a polypropylene (PP) matrix in a twin‐screw extruder at a temperature at which both polymers are in molten state. The extrudate was then stretched at the die exit to generate long and thin fibers of PA in the PP matrix well oriented in the direction of flow. Adhesion between the phases was promoted by addition of PP grafted with maleic anhydride (PP‐g‐MA). During the second step, the chopped extrudates were molded by injection or compression molding at a temperature at which PA in the form of fibers is in the solid state and the PP matrix is molten. The control of the formation of such ultrafine fibers was obtained by quantitative analyses for the deformation of the minor PA‐phase during twin‐screw extrusion and stretching at the exit of the die that involve both shear and extensional flows. Morphology and mechanical properties of such polymer/polymer composites were compared to equivalent blends with dispersed spherical particles‐type morphology prepared in a batch mixer device.
PP/EMA TPV: Dynamic cross‐linking through an alcoholysis reaction
Authors: Pesneau Isabelle , Champagne Michel F. , Huneault Michel A. 
Published: April 2004

AbstractDynamically cross‐linked polypropylene/ethylene‐methyl acrylate copolymer (PP/EMA) blends were prepared by reactive extrusion in a twin‐screw extruder. A transesterification reaction catalyzed by an organotin compound and involving the acrylic moieties of EMA with the hydroxyl functions of pentanediol was used to cross‐link the elastomeric EMA. The extent of cross‐linking was estimated through the insoluble content of the blend. The alcohol‐to‐acrylic ratio and the dibutyltin oxide content were both found to increase the extent of EMA cross‐linking. Processing conditions such as screw rotation rate and extrusion temperature profile also had large effects on the reaction extent. Conditions leading to improved pentanediol dispersion were found to generate larger insoluble fraction. Gel contents of EMA phase as high as 75% to 85% were obtained. Interestingly, the stress‐strain curves of the cross‐linked PP/EMA TPV are very well represented by a single master curve. Dynamically cross‐linked blends show systematically better tensile properties than the non‐reactive system. Blends with higher insoluble content show strain at break in the 650%–750% range. Material processability was maintained, even for the systems with high insoluble content.
Rheology of concentrated solutions of hyperbranched polyesters
Authors: Andrady Anthony L. , Nunez Carlos M. , Chiou Bor‐Sen , Khan Saad A. 
Published: April 2004

AbstractThe solution rheology of different generations of hyperbranched polyesters in N‐methyl‐2‐pyrrolidinone (NMP) solvent was examined in this study. The solutions exhibited Newtonian behavior over a wide range of polyester concentrations. Also, the relative viscosities of poly(amidoamine) (PAMAM) dendrimers in ethylenediamine were compared with those of the hyperbranched polyesters in NMP. Both types of dendritic polymers have relative viscosities that are exponential functions of their molar fraction in solution. The slopes of these relative viscosity curves show a linear relationship with respect to the generation number. PAMAM dendrimers have the greater slopes for each generation, reflecting their relatively larger intrinsic viscosity values.
Influence of side‐chain structures on the viscoelasticity and elongation viscosity of polyethylene melts
Authors: Lin Gwo‐Geng , Shih Hsi‐Hsin , Chai Ping‐Chang , Hsu Shio‐Jin 
Published: April 2004

AbstractMetallocene‐catalyzed, low‐density and linear low‐density polyethylenes with similar melt indexes were used to investigate how side‐chain structures influence the elongation viscosity and viscoelastic properties. The viscoelastic properties were determined with a rotation rheometer, while the elongation viscosities were acquired by using isothermal fiber spinning. The Phan‐Thien‐Tanner (PTT) model was also used to understand how the side‐chain structure affects the elongation behavior. Experimental results demonstrate that the log G′ vs. log G″ plot can qualitatively describe the effects of the side chain branch on the rheological properties of polyethylene melts. According to the results determined by the PTT model, low‐density polyethylene (LDPE) has low elongation viscosities at high strain rates. This low elongation viscosity can be attributed to the fact that LDPE has high shear thinning behavior. The long‐chain branching tends to increase entanglements, thereby enhancing the storage modulus, elongation viscosity and shear‐thinning behaviors. Uniform side‐chain distribution lowers the entanglements, which results in a low storage modulus, elongation viscosity and shear‐thinning behavior.