bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer‐polymer interdiffusion during coextrusion
Authors: Kim Jin Kon , Han Chang Dae 
Published: May 2005

AbstractPolymer‐polymer interdiffusion during coextrusion is considered theoretically from the point of view of interdiffusion between two melt streams flowing side by side in a film or sheet coextrusion die. It has been found that three factors, namely, molecular weight, the interaction parameter, and polydispersity have a profound influence on the interfacial layer thickness and adhesive bond strength of coextruded films and sheets. It is pointed out that when interdiffusion between two chemically dissimilar polymers takes place In stratified two‐phase flow, the chain orientation in the flow channel greatly influences the rate of interdiffusion, and consequently the interfacial layer thickness and adhesive bond strength. Orientation factors for macromolecular chains in a steady shear flow field are expressed in terms of shear stress at the interface and the plateau modulus of each of the respective polymers being coextruded. As an illustration, we have used information on the self‐diffusion coefficients for poly(vinylidene fluoride) and poly(methyl methacrylate) in the molten state, to estimate the interfacial layer thickness and adhesive bond strength of coextruded two‐layer sheets, as affected by processing variables.
Ultrasonic velocity and attenuation of polymeric solids under oscillatory deformation. II: High density and linear low density polyethylene and their blends
Authors: Tanaka Akira , Nitta Koh‐Hei 
Published: May 2005

AbstractIn order to understand the viscoelastic non‐linearities in polyethylene, dynamic ultrasonic properties of high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and their blends were studied. In the case of HDPE and HDPE‐rich films, for which the nonlinearity is high, the dynamic attenuation coefficient increased with the dynamic strain amplitude. The increase in the attenuation coefficient can be ascribed to plastic deformations such as defect‐ and/or void‐formation in the spherulites. On the other hand, in LLDPE and LLDPE‐rich blends for which the nonlinearity is low, the attenuation coefficient decreased with strain. The decrease in the attenuation coefficient can be ascribed to the orientation of lamellae. Thus, it was concluded that the viscoelastic nonlinearity of polyethylene is caused by plastic deformation. This conclusion was also deduced from other dynamic ultrasonic quantities such as the dynamic viscosity and dynamic density.
Effect of annealing on the properties of poly(ether ether ketone)
Authors: Arzak A. , Eguiazábal J. I. , Nazábal J. 
Published: May 2005

AbstractThe effect of annealing on the properties of poly(ether ether ketone) has been studied by changing annealing temperature and time. Crystallinity increases with annealing temperature, but is little affected by annealing time. Annealing time results suggest an improved crystalline perfection as annealing time increases. Higher crystallinity levels cause an increase in stress‐related properties and a decrease in strain‐related properties. Crystalline perfection, however, seems to produce an increase in stress‐related properties, but it does not affect strain‐related properties. Consideration has also been given to the effect of other possible parameters different from crystalline structure, such as crosslinking, on the variation of properties.
Anisotropic thermal expansion of densely cross‐linked oriented polymer networks
Authors: Broer Dirk J. , Mol Grietje N. 
Published: May 2005

AbstractDensely cross‐linked oriented polymer networks are made by in‐situ photopolymerization of oriented liquid‐crystalline diacrylates. Freestanding films that exhibited highly, anisotropic thermal expansion were prepared. The influence of the molecular structure and type and degree of orientation on the anisotrpic thermal expansion is described. The expansion coefficient of uniaxially oriented networks in the direction of the molecular orientation is slightly positive at temperatures below the glass transition of the networks and becomes negative as soon as this transition sets in the result is an effectively zero expansion over a wide temperature range. By introducing a molecular helix in, the network perpendicular to the film surface, a low thermal expansion is established in two directions in the plane of the film or coating.
Solvent penetration in cured epoxy networks
Authors: Kaplan Martin L. 
Published: May 2005

AbstractThe kinetics of the sorption characteristics of seven different solvents has been measured at 22°, 40°, and 50°C in several cured epoxies. In addition to water, the organic solvents methanol, acetone, isopropanol, ethyl acetate, 1,2‐dichloroethane, and toluene were examined. The resin, diglycidyl ether of bisphenol A, was cured with four hardeners, each one resulting in a different epoxy material. The curing agents include triethylenetetramine, nadic methylanhydride, dicyandiamide and m‐phenylenediamine, all commonly used substances. Data were analyzed using Fick's diffusion equation. In general, three types of behavior were observed, Fickian diffusion, Case II diffusion, and anomalous diffusion. Fickian or anomalous behavior dominated at all temperatures. Diffusion was both material and solvent dependent. The anomalous nature of isopropanol was noted. Although chemically similar to methanol and about the same size, as acetone, isopropanol is sorbed at a much lower rate. A combination of physical and chemical effects appeared to be responsible for the observations in the epoxies. Diffusion coefficients were estimated for all penetrants and were mostly in the range of 10−9 to 10−11 cm2/s. Where appropriate, apparent activation energies for diffusion were calculated from the kinetic curves.
A fatigue test for controlling the quality of polyethylene copolymers
Authors: Zhou Y. , Lu X. , Brown Norman 
Published: May 2005

AbstractThe lifetimes of 17 commercial ethylene‐hexene copolymers were measured under fatigue and constant load. These LLDPE resins all had about the same melt flow index and density, but their lifetimes under fatigue and constant load varied by factors of 17 to 104, respectively. The lifetimes in fatigue were 1/25 to 1/2000 times the lifetime under constant load, but the ranking of the resins in fatigue with respect to their resistance to slow crack growth correlated with the ranking under a constant load. It is recommended that a tensile fatigue test on a notched specimen is a useful short time test for the quality control of ethylenehexene copolymers that may be used for gas pipes or other critical applications.
Compatibilization of polymer blends by reactive processing
Authors: Xanthos M. , Dagli S. S. 
Published: May 2005

AbstractThis review examines some recent developments in the field of reactive compatibilization of polymer blends by melt processing in extruders and intensive batch mixers. Three routes to reactive compatibilization are considered, namely, the use of suitably functionalized blend constituents, the incorporation of polymeric compatibilizers, and the addition of low molecular weight compounds. Representative systems from the recent patent and open literature are classified according to method and assumed mechanism of compatibilization, and the types of chemical reactions involved. A variety of polymer blends are discussed, including impact modified thermoplastics, polymer modified engineering thermoplastics, dynamically vulcanized thermoplastic elastomers, and co‐crosslinked rubber/rubber blends. Examples of potential opportunities in reactive compatibilization are also presented.
Modeling of mold filling process for powder injection molding
Authors: Najmi Liaquat Ali , Lee Daeyong 
Published: May 2005

AbstractThe mold filling process has been modeled for the injection molding of different polymer‐based binders and powder‐polymer mixtures. It is essentially a two dimensional non‐Newtonian fluid flow analysis in a non‐isothermal environment. A complete analysis is accomplished by combining a finite element method and control volume technique to describe an increment of flow front movement, whereas a finite difference method is used to solve the energy equation to characterize the temperature distribution. Numerical results are compared to exact solutions for a circular ring cavity using a power law fluid model under an isothermal condition. Comparison of computed results against published data for a simple circular disk shows good agreement between the two analysis methods. After making selected comparison studies, it is demonstrated that the filling process in Powder Injection Modeling with different combination of powder‐polymer mixtures is markedly dependent on specific combinations of powder; and polymer based binders. Computed flow front results for a rectangular cavity also compared favorably against the data for a power law fluid model under non‐isothermal conditions.
Nylon/Kevlar composites. I: Mechanical properties
Authors: Yu Z. , Ait‐Kadi A. , Brisson J. 
Published: May 2005

AbstractThis paper deals with the characterization of the mechanical properties of Kevlar/nylon composites. It has been shown that addition of up to 5 % Kevlar to nylon matrices (nylon‐6, nylon‐ 11, and nylon‐6,6) is possible by melt blending, and results in improved mechanical properties as compared to the pure matrix. In order to increase the interfacial adhesion of the fibers and the matrix, various chemical treatments were performed on the fibers: surface hydrolysis, succinyl chloride reactions and suberoyl chloride reactions. These were shown to affect significantly the mechanical properties, and depending on the treatment Of the fiber, improvement or deterioration of the mechanical properties could be observed. The effect of humidity has also been investigated, and it was shown that the addition of Kevlar greatly reduced the susceptibility of the tensile modulus to humidity.
On the mode I delamination test and the importance of laminate lay‐ups
Authors: Benzeggagh M. L. , Gong X. J. , Laksimi A. , Roelandt J. M. 
Published: May 2005

AbstractThe aim of this work has been the study of mode I delamination of multiply double cantilever beam specimens of glass fiber/epoxy. The results show an important influence of laminate lay‐ups on delamination resistance. The value ofGIcat the initiation of delamination varies with laminate curvature couplingKy/KxandKxy/Kx. An empirical model describing this variation has been proposed. In addition, it is seen that the values ofGIcat the initiation of delamination and at stable crack growth will be very different. The delamination resistance can be characterized by two constants:GIccorresponds to the initiation of delamination, andGSIpcorresponds to the plateau of stable crack propagation. The correlation between experimental measurement and analysis of compliance and energy release rate results reveals significant three‐dimensional effects.
Impact and compression response of composite materials containing fortifiers
Authors: Scott R. F. , Lee S. , Poon C. , Gaudert P. C. 
Published: May 2005

AbstractThe effect of adding fortifiers to an epoxy matrix on the response to impact and compression‐after‐impact properties of carbon fabric/epoxy laminates was investigated. The experimental work included determining laminate compression strength, absorbed energy from impact, damage area and compression‐after‐impact strength for an impact energy level of 21 joules per centimeter of thickness. This paper presents the results from this investigation and discusses the relationship between neat resin properties (with and without fortifiers) and the laminate properties.
Weldline strength in injection molded glass fiber‐reinforced polypropylene
Authors: Fisa B. , Rahmani M. 
Published: May 2005

AbstractWeldlines are inescapable byproducts of the injection molding process. They represent potentially fatal flaws particularly in multiphase materials. In this work weldlines in injection molded glass fiber‐reinforced polypropylene (0 to 40wt%) were studied as a function of the cavity shapes and depths. It was found that the weldline is a zone between 2 and 8 mm wide extending throughout the thickness in which the fibers are oriented almost perfectly in a plane parallel to the weldline. While the strength of moldings without weldlines depends on the mold shape and on the fiber concentration, the weldline strength is a function of fiber content only. A simple model based on the assumption of complete debonding of the fiber‐matrix interface when failure occurs can be used to predict the strength loss in the weldline.
Crystallization of polymer melts under fast cooling. I: Nucleated polyamide 6
Authors: Brucato V. , Crippa G. , Piccarolo S. , Titomanlio G. 
Published: May 2005

AbstractSamples of nucleated polyamide 6 were quenched from the melt so as to monitor cooling histories. Their morphology and crystal structures were discussed in relation to sample thermal history; cooling history relevant to quenched sample morphology was recognized as being confined in the interval 110 to 160°C. In particular, samples were essentially amorphous for cooling rates larger than 200°C/s. The γ‐crystalline form was observed for cooling rates in the interval 70 to 200°C/s, whereas α crystalline structure was found dominant for yet lower cooling rates. Crystallinities evaluated from densities of quenched samples were compared with predictions of an isokinetic form of the Avrami model for polymer crystallization kinetics.
Property modifications in poly(p‐phenylene benzobisthiazole) fibers with high‐tension and high‐temperature drying versus postprocessing heat treatment
Authors: Pottick L. A. , Farris R. J. 
Published: May 2005

AbstractModifications in the structure and mechanics of poly(p‐phenylene benzobisthiazole) (PBT) fibers have been attempted through high‐tension and hightemperature drying and subsequent postprocessing heat treatment experiments. High‐tension drying results in an enhancement in tensile properties by offsetting compressive shrinkage stresses during the drying process and improving the molecular alignment within the fiber. Elevated temperature drying under tension further improves the extent and perfection of the lateral molecular order. The increased molecular ordering and improved tensile properties are believed to result from the removal of water and residual acid at elevated temperatures. The final fiber properties after subsequent postprocessing heat treatment are independent of the drying conditions. These results suggest that the ultimate fiber properties are a function of the total strain imposed in all the processing operations (dry jet stretch region, coagulation and drying process, postprocessing heat treatment). The attainment of the fiber's theoretical highmodulus/high‐strength properties appears limited by defects such as voids and internal stresses which, in turn, restrict the amount of strain imposed during the fiber process.
Polycarbonate‐polystyrene block copolymers and their application as compatibilzing agents in polymer blends
Authors: Jiang Rishan , Quirk Roderic P. , White James L. , Min Kyonsuku 
Published: May 2005

AbstractThe synthesis of a block copolymer with polystyrene (PS) and polycarbonate (PC) segments is described. It is produced by anionic polymerization of the styrene and endcapping with a hydroxyl group followed by subsequent reaction with phosgene and bisphenol‐A. The polystyrene/polycarbonate block copolymer was used as a compatibilizing agent for blends of poly(ethylene terephthalate) (PET) and poly(p‐ phenylene oxide) (PPO). The block copolymer reduced the dimensions of the dispersed phase. The uniaxial mechanical properties of the compatibilized blends were improved by 5 to 10 wt% loadings of the copolymer.
Flow curve–molecular weight distribution: Is the solution of the inverse problem possible?
Authors: Malkin Alexander Ya. , Teishev Albert E. 
Published: May 2005

AbstractSeveral different theoretical models have been developed relating the flow curve of a polymer melt to its molecular weight distribution (MWD). These models allow calculation of the flow curve if MWD is known beforehand. According to one model the non‐Newtonian behavior of a polymer melt is considered as a consequence of the gradual transition of high molecular weight (MW) fractions to the rubbery (non‐fluid) state. This model, which gives realistic predictions of the flow curve, can be transformed into the equation for MWD, which appears to be directly related to the flow curve. The derived equation seems to present the exact solution of this inverse problem. Nevertheless, calculation tests show the instability of such a solution. This means that any inevitable experimental error in the flow curve measurements can lead to an unexpected and arbitrary wide divergence of the calculated MWD from the true one. However, if definite preset forms of MWD are used, the MWD width can be determined from the flow curve. This has been confirmed by experiments on different polymers, such as low‐density polyethylene (LDPE), polyisoprene (PI), butyl rubber (BR), and polystyrene (PS).
Analysis of polymer membrane formation through spinodal decomposition. II: Effect of Flory‐Huggins enthalpic and entropic contributions
Authors: Laxminarayan Anand , Caneba Gerard T. 
Published: May 2005

AbstractThe phenomenological analysis of the thermal inversion membrane formation through spinodal decomposition was further developed to include enthalpic and entropic contributions to the Flory‐Huggins interaction parameter. We found that material and processing conditions can be lumped into two parameters. One is the Deborah Number, De, which takes into account the thermal quenching relative to the phase separation induction time. The other one, designated as an ε‐parameter, takes into account the quenching temperature relative to the spinodal temperature and the ratio of the enthalpic to the entropic contributions to the Flory‐Huggins interaction parameter. From the model system, we found that the dimensionless interdomain distance, δ, as a function of 1/De (which is proportional to the cooling rate) falls in a relatively narrow banded region for all practical values of ε. As 1/De approaches infinity, δ is asymptotic up to maximum value of 3.5. This means that membranes made under applicable conditions will have a ratio of pore sizes of no more than 3.5. Other assumptions of the model are: (1) the mobility is temperature‐independent; (2) the mutual diffusivity is a linear function of temperature; and (3) the thermal history (Temperature vs. Time), can be represented as two successive linear functions.
Migration and blooming of stabilizing antioxidants in polypropylene
Authors: Spatafore Rinamarie , Pearson L. Timothy 
Published: May 2005

AbstractWe have studied the migration of the hindered phenol, octadecyl‐3,5‐bis (1,1‐dimethylethyl)‐4‐hydroxybenzenepropanoate, and the phosphite co‐stabilizer tris 2,4‐bis(1,1‐dimethylethyl)phenylphosphite, out of films of polypropylene (nominal melt flow 3.5 g/10 min). Loss of additive from an initial 10% weight‐% level in the polymer was followed by FTIR bands in the appropriate regions. Temperatures of 298 K, 313 K and 333 K were used. An attempt was made to analyze migration data using Fick's law for diffusion by means of a least squares fit. Octadecyl‐3,5‐bis (1.1‐dim ethylethyl)‐4‐hydroxybenzenepropanoate diffused according to Fick's law with a temperature independent diffusion constant (D = 1.27 × 10−15 m2 S−1) to a steady state concentration of 7.2 % + −0.56 weight‐%. The phosphite did not diffuse at all at 298 K and 313 K, but diffused with D = 8.1 × 10−16 m2 S−1 to a steady level at 333 K. Our interpretation of the phosphite migration data assumes that most of the phosphite in the sample is immobilized. A subset of the total phosphite level is free to diffuse to the surface of the polymer.
Compatibilized and dynamically vulcanized thermoplastic elastomer blends of poly(butylene terephthalate) and ethylene propylene diene rubber
Authors: Moffett A. J. , Dekkerrs M. E. J. 
Published: May 2005

AbstractCompatibilized and dynamically vulcanized thermoplastic elastomer blends of poly(butylene terephthalate) (PBT) and ethylene propylene diene terpolymer (EPDM) can be prepared by using an EPDM rubber that contains reactive epoxy groups. During melt mixing the epoxy groups react with PBT endgroups to form graft copolymer. The compatibilized blends can be dynamically vulcanized by conventional vulcanization agents for EPDM such as peroxides or by vulcanization agents that react with residual epoxy groups on the EPDM such as diamines. This paper describes the effects of compatibilization and dynamic vulcanization on microstructure and mechanical properties.
Dielectric characterization of water sorption in epoxy resin matrices
Authors: Maffezzoli A. M. , Peterson L. , Seferis J. C. , Kenny J. , Nicolais L. 
Published: May 2005

AbstractWater sorption in epoxy based materials was analyzed by dielectric spectroscopy using remote sensors. A method to determine diffusion coefficients from the changes in permittivity during water absorption is proposed and was verified experimentally by comparison with standard water gain measurements. Although the technique is limited by electrode polarization phenomena, it is sensitive to the presence of water molecules and is capable of detecting different levels of water concentration as a function of frequency. The utilization of remote sensors demonstrated the capability of dielectric analysis to be applied both in the laboratory environment, and on a larger scale, as a nondestructive technique for monitoring environmental changes in actual polymer matrix composite parts.
The use of cryogenically ground rubber tires as a filler in polyolefin blends
Authors: Oliphant K. , Baker W. E. 
Published: May 2005

AbstractThe effects of cryogenically ground rubber tires (CGT) on some of the mechanical properties of blends with linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) are presented. Precoating the CGT particles with an ethylene‐acrylic acid copolymer is shown to overcome most of the deleterious effects of adding CGT to LLDPE, while still retaining composite processability. A blend of 40 wt% EAA coated CGT particles with LLDPE is shown to have impact and tensile strengths that are 90% of those for the pure LLDPE, representing increases of 60 and 20%, respectively, over blends with uncoated particles. Blends of LLDPE with ground tire bladders demonstrate that even better mechanical properties can be obtained with similar large rubber particle size but somewhat better adhesion. For HDPE, however, it is shown that with large rubber particles, moderate adhesion is not sufficient to produce useful composites.
Buildup and relaxation of molecular orientation in injection molding. Part I: Formulation
Authors: Flaman A. A. M. 
Published: May 2005

AbstractA numerical simulation model for the analysis of the buildup and, the relaxation of molecular orientation in injection‐molded products has been developed. The constitutive equations of the material are described using an extended version of the viscoelastic material model developed by Leonov. The volumetric responses are described using two different equations of state, the Tait equation and an equation developed by Spencer and Gilmore. A WLF‐type of equation is used for the temperature and pressure dependence. Stresses calculated with the model are coupled to birefringence by means of the stress‐optical rule. Birefringence, in turn, is used to characterize the molecular orientation. The model is used to investigate the influence of the processing conditions, the mold elasticity, and the pressure dependence of the material functions on the pressure and birefringence profiles. The material data used are for polystyrene, PS 678E, and are determined experimentally.