bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization and cure of dielectric and conducting polymer thick films
Authors: Prime R. Bruce 
Published: December 2004

AbstractPolymer thick films are screenable polymer pastes which vary from electrically non‐conducting to electrically conducting. These materials typically contain significant amounts of high boiling solvents, and cure therefore involves removal of solvent in addition to crosslinking of the polymer matrix. In this study thermogravimetric analysis and dynamic mechanical analysis were utilized to characterize the residual solvent and glass transition behavior, respectively, with cure of the polymer thick films. Thickness was maintained constant at approximately 25μ and 100μ by using stainless steel mesh substrates. Results showed that IR curing, although able to heat more rapidly, did not accelerate the cure beyond that expected from time at temperature. Time‐temperature superposition kinetics were employed to measure activation energy of cure, generate master cure curves, and to quantify IR cure time‐temperature profiles. Cure models describing Tg and residual cure as a function of time, temperature, and film thickness were developed.
The effect of cyclic stress on the physical properties of a poly(dimethylsiloxane) elastomer
Authors: Fitzgerald John J. , Martellock Arthur C. , Nielsen Paul L. , Schillace Robynn V. 
Published: December 2004

AbstractThe dynamic creep behavior of a filled poly(dimethylsiloxane) elastomer was studied under cyclic stress. The stress level was chosen such that the increase in the internal temperature was small and that microcracks were not observed. This work has demonstrated that cyclic stress in combination with high temperature accelerates the degradation of the elastomer. The results suggest that because of the applied force, breaks in the load‐bearing chains of the network occur. These breaks, while relieving the mechanical stress, create highly reactive ionic fragments. It is believed that because of the subsequent reactions of the ionic fragments, changes in the specific gravity, storage modulus, effective crosslink density, and length of the sample (creep) are observed. The observed decrease in the storage modulus is thought to occur because of the reaction of the ionic fragments with moisture, which results in the formation of silanol chain ends that reduce the effective crosslink density. The results also show that contrary to the prediction of the Boltzmann's Superposition Principle, the rate of creep is greatly enhanced when the sample is subjected to a sinusoidally varying dynamic load as compared to a comparable static load. The polymer weight loss was found to be linear with time and strongly dependent on the level of applied dynamic and static force. In addition, the weight loss and rate of creep were also found to be strongly dependent upon temperature.
Optical characterization of three‐dimensional surface and bulk anisotropy in high refractive index polymers
Authors: Cha Cheol Y. , Moghazy Samir , Samuels Robert J. 
Published: December 2004

AbstractInterest in the development of polymeric materials for high temperature, electronic and microelectronic applications has led to an increasing number of new polymers. Many of these polymers have complex organic ring structures and semirigid backbones, characteristics that have posed some difficulties for structural analysis. The purpose of this paper is to test and compare two practical nondestructive optical techniques, polarized optical microscopy and polarized refractometry, for the determination of three‐dimensional surface and bulk anisotropy in these advanced materials. The optical techniques are first tested on a series of optically homogeneous uniaxially oriented isotactic polypropylene films and then applied to the analysis of high refractive index Kapton (PMDA‐ODA) polyimide films. The study includes a test of the validity of the compensator method, including the effect of fringe jumping, the use of polymer retarders, and the tilting technique of Stein.
Noncontact measurement of parison thickness profiles affected by swell and sag in continuous extrusion blow molding
Authors: Diraddo R. W. , Garcia‐Rejon A. 
Published: December 2004

AbstractOptimization of final part thickness distributions is crucial in the extrusion blow molding process in order to minimize resin usage. Prediction of part thickness distributions from basic process and material parameters would be ideal. However, attempts to do so have been unsuccessful, largely because of the inability to predict parison thickness profiles. One must therefore resort to measurement of the parison thickness profile and estimation of the final part thickness distribution by computational methods. This paper describes a new technique for the noncontact estimation of parison thickness profiles in continuous extrusion blow molding. The method accounts for sag and requires no previous knowledge of rheological data. It can be employed on‐line for the purposes of process monitoring and control. The approach is based on the measurement of the parison length evolution with time during extrusion, the parison diameter profile, the flow rate, and the melt temperature gradient along the length of the parison. These parameters are utilized in conjunction with a theoretical approach that describes the extrusion of a parison under the effects of swell, sag, and extrusion into ambient conditions. Results are presented for three resins of various molecular weight distributions. The degree of sag is minimal at the top and bottom of the parison, and reaches a maximum near the center of the parison. Results are also presented to demonstrate the versatility of the method under other process conditions, such as varying flow rate, die temperature, and die gap.
The melt rheology of poly‐ε‐caprolactam/polypropylene alloy: A VAMAS round‐robin study
Authors: Samurkas T. , Rogers M. G. 
Published: December 2004

AbstractThe melt rheology of commercial poly‐ε‐caprolactam/polypropylene blend, Orgalloy R‐6000 was studied by a number of university, industrial, and government laboratories as part of the Versailles Project on Advanced Materials and Standards (VAMAS), Technical Working Party on polymer blends round‐robin research program. The objective of the organization is to facilitate the development of standard test methods for the characterization of such complex materials. The program was established to evaluate proposed test methods for characterization of the melt rheology of commercial blends. Orgalloy R‐6000 was studied in both shear and extensional flows. A number of the laboratories also compared its rheology to that of a polypropylene and a polyamide that are similar to those that were used to produce it. This material showed all the viscoelastic properties expected of molten thermoplastics but was found to be significantly more elastic than its constituent materials. The poor quantitative agreement of the interlaboratory results indicate that improvements in the standardization of test methodologies and sample conditioning for such hydroscopic materials is necessary.
Orientation of miscible and immiscible polymer blends
Authors: Abtal Essaid , Prud'Homme Robert E. 
Published: December 2004

AbstractPolystyrene (PS) and poly(vinylmethylether) (PVME) were used to study the orientation of miscible and immiscible polymer blends. A miscible blend containing 60 wt% PS was prepared by casting the sample from a benzene solution. The immiscible blend was made by annealing the initially miscible mixture above its lower critical solution temperature for different times and temperatures. Fourier transform infrared spectroscopy and birefringence were used to measure the orientation of PS and PVME, before and after phase separation. Stress‐strain curves were also measured for the two types of systems. It was found that the two polymers orient differently and that phase separation induces an increase in the overall orientation of the mixture, in the modulus and in PS orientation. The differences observed between pure PS and PS in the blend were attributed to changes in specific interactions and density of entanglements. The variations with phase separation were attributed to a change in the morphology of the system.
Morphology‐Properties relationship of a ternary polymer alloy
Authors: Kojima Takayuki , Kikuchi Yutaka , Inoue Takashi 
Published: December 2004

AbstractA ternary alloy of polyamide‐6 (PA), poly(phenyleneether) (PPE), and rubber has a three‐phase structure, in which PPE particles with rubber inclusions are dispersed in a PA matrix. This is an excellent thermoplastic with high impact strength and high heat resistance. To understand the morphology‐properties relationship, we undertook a two‐dimensional finite element method (FEM) analysis on the deformation mechanism of the ternary alloy. A three‐phase model was constructed so that five hybrid particles of PPE‐shell and rubber‐core were embedded in the PA matrix. When the model was deformed at room temperature, the rubber domain induced yielding of the PPE‐shell and the PA‐matrix and at large strains the yielded zone expanded to pervade the whole space. This suggests that the toughening mechanism is essentially the same as in the binary alloy of PA and rubber (rubber‐toughened PA). At higher temperatures (e.g., at 100°C) the stress concentration occurred not only in the PA matrix but also in the PPE‐shell. It implies that the PPE‐shell is highly responsible for bulk deformation, even though it is part of the dispersed phase. At high temperatures, the rigidity of PPE affects the alloy bulk rigidity so that the ternary system exhibits high heat resistance.
Morphological characterization of simulated polymer blends by light scattering
Authors: Bélanger C. , Cielo P. , Utracki L. A. , Favis B. D. , Patterson W. I. 
Published: December 2004

AbstractThe morphology and the properties of polymer blends are closely related to processing conditions. A skin/core morphology, with a minor phase undergoing variations in orientation and aspect ratio from the surface to the core of the material is observed in processes such as the injection molding of blends. The use of optical inspection to control the stability and the quality of the product on‐line is an interesting tool. In this paper, polymer composites made from glass fibers and glass microspheres embedded in a matrix of PS are used to simulate two‐phase polymer blend morphology with a skin/core configuration. The relationships between the morphology of two‐phase systems and the diffuse pattern scattered from an incident light beam are investigated through an analysis of the iso‐intensity plots. Information can be obtained from the ratio of the axes of the ellipsoidal iso‐intensity domains for depth‐invariant blend morphology, and from the variation of this ratio as a function of the distance from the center of the pattern for depth‐varying morphology samples. It is shown that one can differentiate the skin morphology and thickness effects.
Curing of unsaturated polyester resins—effects of pressure
Authors: Huang Yan‐Jyi , Lu Tian‐Jyh , Hwu Wei 
Published: December 2004

AbstractThe effects of pressure ranging from 0.1 to 6.21 MPa (0–900 psig) on the curing of unsaturated polyester resins at 110°c were investigated by an approach of integrated reaction kinetics‐rheology‐morphology measurements using a pressure differential scanning calorimeter (DSC), an infrared spectrophotometer (IR), a Haake rheometer, and by using scanning electron microscopy (SEM). Increasing pressure was found to delay the gel effect, and a previously unknown plateau of kinetic‐controlled region in the initial portion of the DSC rate profile was observed. The plateau region was mainly attributed to the crosslinking of C  C double bonds inside the microgel particles, as revealed by the conversions of styrene and polyester C  C bonds measured by IR, gel conversion data and SEM micrographs. The mechanisms of reaction kinetics both at atmospheric pressure and under pressures have also been elucidated by the progress of buildup of microgel structures.
Rheological and physical properties of polyarylate/LCP blend systems
Authors: Hong Soon Man , Kim Byoung Chul , Hwang Seung Sang , Kim Kwang Ung 
Published: December 2004

AbstractA polyarylate Unitika U‐Polymer 100 (PAR) was melt blended with a thermotropic liquid crystalline polymer (LCP) Vectra A950, and the processingmorphology‐properties relations were investigated. Inclusion of LCP slightly reduced Tg of PAR. The PAR/LCP blend with the LCP content higher than 50 wt% exhibited a noticeable yield stress, particularly in the vicinity of crystal‐to‐nematic transition temperature (Tcn). LCP lowered the blend viscosity above Tcn and seemed to play a role as processing aid. The tensile strength of the blends was increased with increasing spin draw ratio and level of LCP, and the spinning temperature influenced tensile strength. The relaxation behavior under dynamic shear and resultant blend morphology based on WAXD and SEM analyses are discussed as well.
Mechanical properties of in‐situ composites based on partially miscible blends of glass‐filled polyetherimide and liquid crystalline polymers
Authors: Bafna S. S. , de Souza J. P. , Sun T. , Baird D. G. 
Published: December 2004

AbstractThe use of inorganic (glass) fiber reinforcement to enhance the mechanical properties and reduce the anisotropy of in situ composites based on blends of liquid crystalline polymers (LCPs) with polyetherimide (PEI) is discussed. It was found that the tensile and flexural moduli are increased and the anisotropy is reduced with increasing grass content (when compared at equivalent LCP weight fractions). The creep compliance of the PEI/LCP composites is reduced upon the addition of glass fibers. However, the disadvantage is that the processability worsens upon addition of glass fibers to the PEI/LCP in situ composites. The effect of adding glass reinforcement on the ultimate tensile strength is less clear, because the data do not show any consistent trend. Similarly, the elongation at break and toughness do not show any consistent improvement upon addition of glass reinforcement. Morphological studies show that there is considerable difference between the size and texture of the reinforcing glass fibers and LCP microfibrils.
Factors influencing the formation of elongated morphologies in immiscible polymer blends during melt processing
Authors: Gonzalez‐Nunez R. , Favis B. D. , Carreau P. J. , Lavallée C. 
Published: December 2004

AbstractThe morphology of the dispersed phase in immiscible polymer blends plays an important role in the determination of the final physical properties. This paper considers factors that influence the final state of deformation of the dispersed phase, and in particular, the formation of fibers and lamellae. Blends of polyethylene and nylon‐6 were extruded by ribbon extrusion at different draw ratios. Prior to single‐screw extrusion the materials were blended in a co‐rotating twin‐screw extruder, and the size of the dispersed phase was studied as a function of the viscosity ratio. As the blends are extruded into ribbons and drawn through the calender rolls, the morphology of the dispersed phase undergoes drastic transformations. The fiber formation is enhanced by increasing the draw ratio. At high draw ratios, long thin fibers are observed. Some biaxial deformation is obtained for the noncompatibilized systems when the extruded materials enter the calender with the maximum closing pressure applied to the rolls. The same effect is observed for the compatibilized systems with lower values of the viscosity ratio. As a general rule, it has been observed that the final dispersed phase deformation is diminished in interfacially compatibilized systems.
Fracture toughness of weldlines in thermoplastic injection molding
Authors: Tomari K. , Harada T. , Maekawa Z. , Hamada H. , Iwamoto M. , Ukai A. 
Published: December 2004

AbstractWeldlines are fatal defects in many injection moldings of thermosetting resins and thermoplastics. Significant strength reduction by weldlines in thermoplastics is caused by poor adhesion, molecular orientation, and a V‐notch effect. These factors have been little investigated in detail, in spite of being well known. In the present article, the V‐notch effect on strength is discussed for two types of thermoplastics, polystyrene and polycarbonate. The depth of weldlines was obtained by milling on the weldline surface, and the fracture toughness was measured with a double edge notched specimen. Polystryrene, which was drastically weakened by weldlines, had relatively deeper V‐notch regions and the fracture toughness was also reduced by weldlines. Although polycarbonate had the same fracture toughness as polystyrene, it had strong weldlines since the depth of weldlines was negligibly small.
Comparison of microwave and thermal cure of epoxy resins
Authors: Wei Jianghua , Hawley Martin C. , Delong John D. , Demeuse Mark 
Published: December 2004

AbstractStoichiometric mixtures of DGEBA (diglycidyl ether of bisphenol A)/DDS (diaminodiphenyl sulfone) and DGEBA/mPDA (meta phenylene diamine) have been isothermally cured by electromagnetic radiation and conventional heating using thin film sample configurations. Fourier transform infrared spectroscopy (FTIR) was used to measure the extent of cure. Thermal mechanical analysis (TMA) was used to determine the glass transition temperatures directly from the cured thin film samples. Well‐defined glass transitions were observed in the TMA thermograph for both thermal and microwave cured samples. Significant increases in the reaction rates have been observed in the microwave cured DGEBA/DDS samples. Only slight increases in the reaction rates have been observed in the microwave cured DGEBA/mPDA samples. Higher glass transition temperatures were obtained in microwave cured samples compared to those of thermally cured ones after gelation. The magnitude of increases of glass transition temperature is much larger for the DGEBA/DDS system than DGEBA/mPDA system. The microwave radiation effect was much more significant in DGEBA/DDS system than in DGEBA/mPDA system. DiBenedetto's model was used to fit the experimental Tg data of both thermal and microwave cured epoxy resins.
Phase structure related to the mechanical properties of poly (styrene‐co‐acrylonitrile)/polycarbonate blends
Authors: Kodama Minekazu 
Published: December 2004

AbstractDynamic mechanical and tensile properties were investigated for blends of poly(styrene‐co‐acrylonitrile) and bisphenol‐A polycarbonate prepared by the solution process. It is apparent from the dynamic mechanical properties that the as‐blended sample has a phase separated structure and the structure changes further with heat treatment. The phase structures of as‐blended and heat‐treated samples were estimated using the theories of Kerner and Davies for the modulus of two‐phase materials and the dynamic mechanical data. The tensile properties obtained at room temperature are not inconsistent with the phase structure estimated for the as‐blended and heat‐treated samples.
Estimation of kinetic parameters associated with the curing of thermoset resins. Part I: Theoretical investigation
Authors: Scott Elaine P. , Saad Zoubeir 
Published: December 2004

AbstractThis is a two‐part theoretical and experimental study on the estimation of kinetic parameters associated with the curing of a thermoset epoxy resin. In Part I, the estimation procedure is presented. This estimation procedure is based on a method referred to as the Box‐Kanemasu method, which involves the minimization of a least squares function, and it represents a new application of this method. The kinetic parameters under consideration were the Arrhenius constants associated with two rate constants in a kinetic model used to describe the curing rate of an amine epoxy resin. The use of differential scanning calorimetry (DSC) and dielectric data assuming isothermal and dynamic experimental conditions was first investigated in a sensitivity study. It was determined that the degree of cure should be treated as the dependent variable and that data from isothermal experiments should be used. The estimation procedure was then used to estimate the Arrhenius constants from simulated degree of cure data with added errors. These results compared favorably with those found using a linear regression method.
Mechanical hysteresis of a polyether polyurethane thermoplastic elastomer
Authors: Gorce Jean‐Noël , Hellgeth J. W. , Ward Thomas C. 
Published: December 2004

AbstractThe mechanical hysteresis of a polyether polyurethane thermoplastic elastomer was studied as a function of temperature, percent strain, and deformation energy. Hysteresis values remained small at low temperatures when the extent of the sample deformation did not disrupt the glassy matrix. This was readily evident at temperatures below the glass transition temperature, Tg of the polymer where the material did not formally yield. At temperatures above the Tg of the polymer, hysteresis remained small even at substantial strains levels and demonstrated the capabilities of the hard segment domains to act as physical crosslinks. At elevated temperatures, percent hysteresis increased as the hydrogen‐bonded hard segment domains weakened. When mechanical hysteresis was considered on the basis of constant deformation energies, hysteresis values reached a maximum in the vicinity of the Tg of the polymer. These maxima existed as a consequence of two opposing trends: the decreasing resiliency of the polymer as it becomes a glass and the increase in the resistance of that glass to undergo deformations sufficient to cause plastic flow. Finally, a hysteresis response surface constructed as a function of deformation energy and temperature was found to be sensitive to both the strain‐induced crystallization of the rubbery soft segment matrix and to the strain‐induced yielding of the glassy soft segment matrix.
Experimental study of transcription of smooth surfaces in injection molding
Authors: Yoshii Masaki , Kuramoto Hiroki , Kato Kazunori 
Published: December 2004

AbstractSignal deterioration of optical discs depends strongly on the substrate surface roughness. Characteristics of surface roughness of the molded substrate have been studied in order to clarify the transcription mechanism of smooth surfaces in injection molding of polycarbonate resin. When the melt temperature, mold temperature, and injecting rate are low, microscopic flow marks more than 5 nm deep are observed on the surface. These flow marks are formed when the melted resin near the mold wall is cooled to the no‐flow temperature of resin before it comes into contact with the mold wall. Molding transcription improves by optimizing the molding conditions for preventing these flow marks. As a result, the surface roughness of the molded substrate obtained is 3.2 nm in maximum height Rmax, which is nearly equal to that of the mold stamper at 2.7 nm in Rmax.
Experimental study and finite element analysis of the injection blow molding process
Authors: Haessly W. P. , Ryan M. E. 
Published: December 2004

AbstractA finite element numerical analysis of preform inflation associated with the injection blow molding process has been developed using a neo‐Hookean constitutive model. The analysis is capable of predicting final wall thickness distributions for axisymmetric mold geometries. Experimental studies were conducted on a Uniloy injection blow molding machine (Model 189‐3 and Model 122). A twelve ounce (355 mL) cylindrical bottle mold was instrumented with contact sensors, thermocouples, and pressure transducers. Visualization studies of the inflation process were performed using specialized tooling and high‐speed video cameras. The experimental studies provide justification for analyzing the deformation by means of a static elastic approach. The predicted wall thickness distribution is in reasonable agreement with the experimental data. Nonuniformities in the temperature distribution in the preform were found to have the most significant impact on the inflation behavior and the resulting wall thickness.