bluuebunny/crossref_metadata_2025 huggingface dataset:
New horizons in advanced oriented fiber
Authors: Tam T. Y. , Boone M. B. , Weedon G. C.
Published: December 2004

Achievement of exceptional properties in films/fibers generally requires very high to ultra high molecular weights and very high degrees of orientation. A brief description of the fiber related technologies‐used to maximize orientation in high performance fibers, e.g., solid state extrusion, special drawing methods gel spinning, and liquid crystal spinning are reviewed. A detailed comparison of the fiber properties resulting from these technologies is also shown. Particular emphasis is.placed on describing the upgrading of polyethylene to a high performance fiber product through several of these technologies. Gel/solution spinning of ultra high molecular weight polyethylene (UHMWPE) is especially highlighted. The latest worldwide efforts to commercialize gel spun fibers are discussed as well as the applicability of the process to other thermoplastics. Applications illustrating the use of high performance fibers in various end use areas are summarized. The primary properties critical to each are also outlined.
Vibration welding of thermoplastics. Part IV: Strengths of poly(butylene terephthalate), polyetherimide, and modified polyphenylene oxide butt welds
Authors: Stokes V. K.
Published: December 2004

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration.; The effects of these parameters on weld quality were systematically studied by first butt welding thermoplastic specimens under controlled conditions, over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests. The three thermoplastics investigated are poly (butylene terephthalate), polyetherimide, and modified polyphenylene oxide. Changes in the weld pressure are shown to have opposite effects on the strengths of polyetherimide and modified polyphenylene oxide welds; Also, the weld frequency is shown to have a significant effect on the weldability of polyetherimide. The weldability data for these three thermoplastics are compared with data for polycarbonate. Under the right conditions, the strengths of butt welds in these materials are shown to equal the strength of the virgin polymer.
Comments and recommendations on the use of the Avrami equation for physico‐chemical kinetics
Authors: Khanna Y. P. , Taylor T. J.
Published: December 2004

Over the last four decades, numerous reports have appeared on the physico‐chemical kinetics, especially crystallization kinetics, based on the Avrami equation, ϕ = exp [−Ktn] where ϕ is the fraction of material unchanged at time t, K is an overall rate constant and “n” is the Avrami exponent indicative of process mechanism. The usage of the Avrami equation has been limited to the determination of “n” and its temperature dependence. It is shown that the evaluation of K and the activation energy (E) using this equation is erroneous since K and E are both influenced by “n” although such would be unexpected from the Avrami equation. On the other hand, if one uses a modified expression, ϕ = exp[−Kt]n, then in addition to the value of “n”, correct values of K and E are obtained. This retains the original correspondence of the Avrami equation to nuclea‐tion and crystal growth processes but extends its applicability to (i) correctly evaluate K and E parameters, and (ii) correctly compare transformation rates when the systems differ in their n values. Experimental data are presented to support these conclusions.
Chemorheological characterization of thermoset cure
Authors: Tungare A. V. , Martin G. C. , Gotro J. T.
Published: December 2004

Thermosetting resin/glass cloth composites find extensive use in the packaging of electrical circuits into multi‐layered circuit boards. To determine optimum processing conditions, it is necessary to understand the rheology of the resin as it cures. In this study, a squeezing flow geometry was used to determine the shear viscosity of a high performance epoxy resin during cure; Viscosity profiles were obtained during rising temperature cure. The results were compared with the complex viscosities obtained using the dynamic oscillatory parallel plate geometry. A numerical optimization algorithm was used to obtain the dual Arrhenius viscosity model parameters from the experimental viscosity data. The sensitivities of the model parameters and their effects on the predicted viscosity profiles were also determined.
Thermal degradation of high nitrile barrier polymers
Authors: Jabarin S. A. , Lofgren E. A.
Published: December 2004

Effects of absorbed moisture on degradation behavior of high nitrile barrier polymers were monitored using thermogravimetric analysis techniques. Non‐modified and 10 percent rubber modified samples were heated isothermally at nitrile processing temperatures (200°C to 240°C) in air and nitrogen environments. Degradation was evaluated in terms of weight loss as a function of heating time and sample coloration. It was determined that complete removal of moisture, as well as high moisture concentration, contribute to increased degradation at the temperatures evaluated. Moisture levels in the range of 0.15 to 0.5 percent were found to minimize degradation. Heating environment, time, temperature, and rubber modification were also found to influence thermal stability.
Adhesive processing by electromagnetic irradiation
Authors: Malaczynski Gerard W.
Published: December 2004

A mathematical model is presented which describes the degree of cure in a thermosetting adhesive used to bond sheet molding compound (SMC) components. The model allows computer aided optimization of the thermosetting process for any type of electromagnetic heating of the various layers of the structure (e.g. dielectric, microwave or induction), arbitrary material properties and arbitrary layer thickness. Computer simulated results are given for the particular case when the cure of the thermosetting material is initiated by its exposure to a high‐power radio‐frequency electric field (dielectric heating). These results indicate a strong sensitivity of the process to the thickness of the adhesive layer and the degree of coupling with the electromagnetic field. The analysis demonstrates that substantial heat losses from the relatively thin adhesive layer to the structural members of the joint by diffusive heat flow can be counterbalanced by additional electric power dissipated either in the adhesive or the structural members of the joint. Although derived for dielectric heating, those results are general, being independent of the type of electromagnetic heating employed.
Flat die geometry—A note
Authors: Matsubara Yutaka
Published: December 2004

Linearly tapered coat hanger dies or T‐dies are widely accepted. Nevertheless a newly proposed curvilinearly tapered coat hanger die has been shown to perform much better. It costs about the same as the other types of dies. This contribution is considered in terms of the recent literature.
Effects of cellulosic fibers on the polymerization of a polyurethane
Authors: De J. Aguilar‐Vega M. , Cruz‐Ramos C. A.
Published: December 2004

The effects that the inclusion of low concentrations (0 to 0.6 percent by Volume) of cellulosic fibers have on the polymerization of a polyurethane was tested by monitoring the viscosity of a reacting diol‐diisocyanate system under isothermal conditions. An increase in viscosity due to the presence of the cellulosic fibers is observed, in addition to the expected rise related to polymer formation. However, a slackening effect appears as more cellulosic fibers are added to the polymerizing medium, in contrast to a system with comparable concentrations of glass fibers. On the basis of reaction kinetics arguments, it is suggested that the hollow nature of the cellulosic fibers and their sorbency play important roles in the effect observed, by reducing the effective concentrations of one of the monomers in the reacting phase, thereby diminishing the overall reaction rate. If similar portions of both monomers are extracted from the bulk of the reacting mass, the reaction is not affected as markedly as when only part of one of the monomers is abstracted. The results found illustrate the type of constraints that arise when certain types of polymerizations are carried out in situ to obtain cellulosic fiber composites.
Interfacial agents for multiphase polymer systems: Recent advances
Authors: Xanthos M.
Published: December 2004

The rapid growth in the use of multiphase polymer systems (blends and composites) is undoubtedly related to the availability of methods of controlling the physical and chemical interactions at the interface. Compounds acting as interfacial agents are commonly known as “compatibilizers” in blends, or “coupling agents” in composites; their function is to promote adhesion and enhance overall properties. This paper is a review of recent advances in the use of these compounds in immiscible polymer blends and thermoplastic composites. Polymeric compatibilizers are classified according to their method of addition (in situformation vs. separate addition) and reactivity. Reactive low molecular weight compounds are also listed and their various coupling mechanisms are discussed. It is demonstrated that common routes to enhanced adhesion exist for some types of blends and composites. For example, reactive graft copolymers and certain crosslinklng agents are equally effective as adhesion promoters in blends and composites containing a polyolefin phase.
Unstable fracture of rubber‐toughened polymers
Authors: Narisawa Ikuo , Takemori Michael T.
Published: December 2004

The goal of this investigation has been to obtain a useful criterion for the onset of ductile instability. Notched 3‐point bend samples of 4 impact‐modified plastics were tested under load‐controlled conditions to enhance the instability. Neither plastic collapse of the remaining ligament nor large scale yielding at the crack tip was observed, although significant damage zone development and sub‐critical crack growth were observed prior to crack instability. The stress intensity factor at instability (Kc) was found to be independent of crack length for the plastics tested. More surprisingly, whenKcwas normalized by the corresponding yield stress, this normalized value was found to be experimentally the same for these four impact modified polymers. Calculations based on ductile tearing instability theory were ambiguous and inconclusive. These results suggest that linear fracture mechanics criteria in load controlled tests may still be applicable for engineering purposes under what has normally been considered ductile conditions.
Crosslinking of polycaprolactone in the pre‐gelation region
Authors: Gandhi K. , Kriz D. , Salovey R. , Narkis M. , Wallerstein R.
Published: December 2004

Polycaprolactone (PCL) crosslinked below the gel point either with peroxide or by exposure to ionizing radiation was compared by Theological studies. As a result of peroxide crosslinking, PCL increases in viscosity and shear rate dependence and exhibits increased dynamic moduli that converge at higher frequencies. The analysis of gases evolved from γ‐irradiated PCL shows that the yield of hydrogen (G = 0.39) approximates the sum of the yields of carbon monoxide (G = 0.19) and carbon dioxide (G = 0.21). It is inferred that equal amounts of crosslinking and scission result from ionizing irradiation. As a result, PCL is converted by irradiation to a densely branched system. Steady shear viscosities do not depend strongly on dose and overlap at higher shear rates. Similarly, dynamic moduli, especially G″, become less sensitive to dose.
An explanation of the discrepancy in gapwise‐density variation of injection‐molded parts between Kamal's and Greener's data
Authors: Chung T.‐S.
Published: December 2004

The purpose of this short note is to attempt to explain the density variation across the thickness of injection‐molded articles. The effects of a gate frozen process on the fluid motion and density buildup during the packing stage were schematically described, determined, and mathematically simulated. The calculated results are qualitatively consistent with the previous data.
Multiplicities and instabilities in film blowing
Authors: Cain John J. , Denn Morton M.
Published: December 2004

The mechanics of the blown film process are studied for Newtonian and viscoelastic models of the polymer melt. Multiple solutions of the governing equations are possible even for the Newtonian fluid, with the existence of more than one steady‐state bubble profile for a given set of operating parameters; steady axisymmetric solutions vanish suddenly at critical combinations of operating variables. Several types of instabilities exist, including one that is analogous to “draw resonance.” The stability of the bubble to infinitesimal disturbances depends on the set of operating parameters that is controlled; control of the bubble inflation pressure is much less stable than control of the amount of inflating air, for example. Heat transfer is stabilizing.
Memory effects in polymers. III. Processing history vs. crystallization rate of nylon 6—comments on the origin of memory effect
Authors: Khanna Y. P. , Kumar R. , Reimschuessel A. C.
Published: December 2004

Our previous publication on this subject has dealt with the processing history effects on the crystallization rate of nylon 6 from the molten state. In this manuscript we present some insights into the molecular origin of the observed effects. Based on the available experimental data, we hypothesize that melt‐extrusion, solution precipitation, or freeze grinding of virgin nylon 6 lead to a more ordered molecular arrangement. This enhanced order persists in the molten state due to H‐bonding and causes a faster crystallization. The virgin material, however, due to its process history, e.g. polycondensation in a viscous melt, is disordered and stays disordered even in the molten state due to H‐bonding. Processing treatments such as melt‐extrusion or freeze‐grinding (high shear stresses) or solution precipitation are required to overcome the H‐bond stabilized disordered environment in virgin nylon 6 and introduce locally ordered regions (nucleation sites), thus accounting for an increase in the crystallization rate.
Recent advances in molecular weight determination
Authors: Cooper Anthony R.
Published: December 2004

The aging and lifetimes of polymeric materials depend on the reaction of these materials to the particular stresses which are applied. In many cases the molecular weight of the polymer is changed and this affords a way to follow aging phenomena. In the simplest case a homopolymer is subjected to a stress which increases or decreases its molecular weight without any chemical changes. As the situation becomes more complicated, changes in chemical composition occur and different sized molecular species are generated. These new species may be of extremely low molecular weight or they may be in the form of crosslinked gel. This paper reviews methods which are available for the determination of molecular weight and molecular weight distribution of polymeric materials. Recently developed or modified techniques are treated in more detail. Techniques which may be used to characterize the oligomer region or analyze for the presence of crosslinked gel are included.
Polymer aging insights available from modulus profiling data
Authors: Gillen Kenneth T. , Clough Roger L.
Published: December 2004

A recently developed analytical technique, modulus profiling, conveniently allows the mechanical properties of elastomers to be mapped with spatial resclutions approaching 0.05 mm. Thus, spatial heterogeneities in modulus caused by processing and aging phenomena can be easily monitored. This paper describes some typical results from polymer aging studies, which Indicate the insights available from this technique. These include application of modulus profiling to understanding (1) mechanical property deterioration of Viton in an elevated temperature, gamma‐radiation environment, (2) recent continuous stress‐relaxation results, and (3) the role of ozone for non mechanically‐stressed materials in high energy radiation environments.
Shear, tack, and peel of polyisobutylene: Effect of molecular weight and molecular weight distribution
Authors: Krenceski Mary A. , Johnson Julian F.
Published: December 2004

The effect of polymeric molecular weight and molecular weight distribution on pressure‐sensitive adhesive performance was studied in a model system of commercial polyisobutylenes. Molecular weight was characterized by size exclusion chromatography and membrane osmometry. Pressure sensitive adhesive performance was assessed by shear, peel, and probe tack testing based on standardized test methods. Lower molecular weight polyisobutylenes (Mw < 600,000) are successful in peel and probe tack testing due to their ability to flow quickly and wet the substrate test surface. They do not function as well in shear, however, where the polymer must resist flow under a load. High molecular weight species, by contrast, perform well in shear resistance tests and less successfully in peel and probe tack testing. Where high and low molecular weight polyisobutylenes are blended to broaden the molecular weight distribution while maintaining constant weight average molecular weight, adhesive performance in shear, peel, and probe tack are improved. All of the adhesive properties tested were found to have their foundation in some fundamental rheological properties of the polymers (e.g., shear viscosity and tensile creep compliance). This suggests the use of fundamental rheological characterization for screening of adhesive formulations over more empirical adhesive testing methods.
Substituted propyne polymers—part II. Effects of aging on the gas permeability properties of poly[1‐(trimethylsilyl)propyne] for gas separation membranes
Authors: Langsam Michael , Robeson Lloyd M.
Published: December 2004

Poly[1‐(trimethylsilyl)propyne] (PTMSP) is an unusual polyyne material which is optically clear, exhibits high solubility in nonpolar organic solvents, and good oxygen compatibility. By contrast, polyacetylene is black, insoluble, and is unstable in oxygen. The long term stability of PTMSP has been determined by a combination of thermal gravimetric analysis (TGA) and permeability test procedures under a number of different isothermal aging conditions. The use of commercial antioxidants at up to 2 weight percent improves the long term stability of PTMSP. The presence of the antioxidant has no effect on the surface fluorination of PTMSP. Testing of PTMSP films for over eight months shows no change in either permeability or selectivity in contrast to previously reported data.
Hydrodynamic analysis of a Banbury mixer
Authors: Cheng Jing‐Jy , Manas‐Zloczower Ica
Published: December 2004

A fluid dynamics analysis package—FIDAP—using a finite element method was employed to simulate the flow patterns in a Banbury mixer. The flow simulations were carried out only for the intensive mixing region, and they were limited to a two‐dimensional analysis. A Lagrangean point of view was adopted and 18 different geometries were selected to represent one revolution of the rotor. A power‐law model with time and temperature dependent parameters was used to characterize the rheological behavior of the mixture. Steady‐state, isothermal flow simulations as well as a transient, non‐isothermal flow analysis were performed for a Banbury B mixer. The results of the analysis show good agreement with experimental observations regarding the development of vortices, the pressure, and the temperature profiles.
Finite element modeling of a counter‐rotating, non‐intermeshing twin screw extruder
Authors: Nguyen K. T. , Lindt J. T.
Published: December 2004

This paper is concerned with Newtonian flow in a counter‐rotating non‐intermeshing twin‐screw extruder. Both the matched and the mismatched screw flight configurations are considered. A three‐dimensional analysis of the pressure flow through the complete extruder cross‐section is included. The model predictions agree well with the experimental data. Computed examples are given to illustrate the utility of this work.
Yield behavior of PP/CaC03 and PP/Mg(OH)2 composites. II: Enhanced interfacial adhesion
Authors: Jančář J. , Kučera J.
Published: December 2004

Effects of the variation of adhesion strength σA on the tensile yield behavior of particulate filled polypropylene (PP) were investigated. To enhance adhesion of PP toward calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2), maleated PP (MPP) was added to PP in various ratios. σA varied from 10‐46 MPa. σA calculated from the Leidner‐Woodhams model are in good agreement with SEM micrographs of the composite fracture surfaces. Dependences σyc vs. σA, at constant Vf = 0.18, were investigated and analyzed in terms of existing models. Using the Turczanyi, Pukanszky, Tüdös model (TPT) for the PP/CaCO3 composite, an effective interlayer “thickness” (teff) and the yield stress of the immobilized PP (σyi) were calculated. Both teff and σyi increased with enhancing of the adhesion.
Processing characteristics, structure development, and properties of uni and biaxially stretched poly(ethylene 2,6 naphthalate) (PEN) films
Authors: Cakmak M. , Wang Y. D. , Simhambhatla M.
Published: December 2004

Poly(ethylene 2,6, naphthalene dicarboxilate), PEN, is very similar to poly(ethylene terephthalate), PET, in its chemical structure and was, therefore, expected to exhibit similar processing characteristics. We, however, observed a few problems during stretching of PEN, the most important of which was necking behavior at 145°C, which is between Tg (117°C) and Tcc (195°C). This is usually observed in PET only when it is stretched close to or below Tg. At temperatures between Tg and Tcc (cold crystallization temperature) PET stretches rather uniformly. The temperature window for film stretching appears to be rather wide, but our results indicate that this is not the case. Films stretched to high stretch ratios become uniform due to propagation and final disappearance of necks as a result of stress hardening. Our attempts at stretching these films at higher temperatures indicated that necking is eliminated, but so is stress induced crystallization, which causes stress hardening (unless high stretching rates are employed). The presence of stress hardening is essential for obtaining high quality, uniform films of these polymers. In addition, at high temperatures thermally activated crystallization which starts dominating the structure development, detrimentally affects the general appearance of the films. In brief, the PEN films we investigated have a narrower processing window than was anticipated based on their thermal behavior alone. At elevated temperatures the films are sensitive to the rate of stretching even more than typical PET processed at comparable conditions. The uniformity of the films depends on the stretch ratio, stretching mode, ratio(s) and rates and temperature. WAXS studies on the films indicate that the macromolecules packed into the low temperature crystal modification. In addition, WAXS pole figure studies suggest that naphthalene planes preferentially orient parallel to the film surface during biaxial stretching. The biaxially stretched films were observed to exhibit a bimodal chain orientation as evidenced by pole figure analysis of the (010) planes.
Phase separation behavior of the epoxy‐CTBN mixture during the curing process
Authors: Kim Do Hyun , Kim Sung Chul
Published: December 2004

To improve the impact resistance of cured epoxy resin, a carboxyl‐terminated butadiene‐acrylonitrile rubber (CTBN) was added. The phase separation behavior during the curing reaction was analyzed by a light scattering experiment. The measurement of transmitted light intensity showed the onset and ending of the phase separation. The change of the scattered light intensity at different angles showed the process of the phase separation, such as the formation and growth of the dispersed domain. The morphology of the blend was also observed by scanning electron micrography (SEM) and was compared with the domains measured by the light scattering method. The impact strength and dynamic mechanical properties of epoxy resin of different rubber concentrations and cured at different temperature were compared, and the effect of the domain size on these properties was analyzed.
Curing of unsaturated polyester resins: Viscosity studies and simulations in pre‐gel state
Authors: Yang Yeong‐Show , Suspene Laurent
Published: December 2004

The curing of styrene‐unsaturated polyester (UP) resins was studied until gelation. The viscosity and gel points were measured during curing and were correlated with curing temperature, initiator concentration, and accelerator concentration. A gelation model concerning the formation of intra‐crosslinked polymer coils, called microgels, was proposed. The model describes the gelation mechanism in four stages: induction, microgel formation, transition, and macro‐gelation. The kinetic and gelation parameters of the model were experimentally obtained. The gel points and viscosities in the pre‐gel state were simulated by the gelation model for isothermal and nonisothermal curings. Comparisons of the simulation results with experimental data showed good agreement.
Stereological measurement and error estimates for three‐dimensional fiber orientation
Authors: Bay Randy S. , Tucker Charles L.
Published: December 2004

A method is presented for measuring three‐dimensional fiber orientation in fiber‐reinforced polymers and placing confidence limits on the results. The orientations of individual fibers are determined from the elliptical intersections between the cylindrical fibers and a polished section. This can be done using either manual digitization or automated image analysis. Volume averages for the sample are computed using an orientation‐dependent weighting function that corrects for the bias of an area‐based sample. Equations are developed for nonuniform fiber lengths, using both number‐average and weight‐average measures of orientation. Sources of systematic, measurement, and sampling error are discussed and equations for sampling error and the propagation of measurement error are derived. The results use a second‐rank tensor to characterize fiber orientation, but the error analysis can be applied to any type of orientation parameter. We implement the technique using manual digitization of optical micrographs. Our implementation accurately measures samples with known orientation, and produces identical results from two perpendicular sections of a glass fiber/nylon injection‐molded sample.
The volume fraction and temperature dependence of the resistivity in carbon black and graphite polymer composites: An effective media—percolation approach
Authors: Blaszkiewicz Michael , McLachlan David S. , Newnham Robert E.
Published: December 2004

A quantitative general effective media (GEM) equation is used to describe a broad range of experimental resistivity‐volume fraction results for graphite‐polymer and carbon black‐polymer composites. The parameters used are the resistivities of each component and the two percolation morphology parameters, a critical volume fraction, ϕc, and an exponent, t. A preliminary model, also based on the GEM equation, is used to describe the temperature variation of the resistivity of the diphasic material near the critical volume fraction.
Mechanical and rheological properties of poly(butadiene‐acrylonitrile) rubber compounds reinforced with cellulosic material
Authors: Jasso‐Gastinel C. F. , Lopez‐Carrillo P. , Mendizabal‐Mijares E.
Published: December 2004

The usefulness of waste (mainly cellulosic) materials as a reinforcement for acrylonitrile‐butadiene rubber (NBR) compounds is shown in this work. The materials tested are: henequen, pine, coconut, sugarcane husks, lignin, and wood sawdust. Their performance is compared with that of commercial reinforcement materials (santocel and solka), using the same copolymer composition without reinforcement as a reference compound. Uniform particle size is achieved by milling and screening. For some of the materials, 6 mm fibers and polymerfiber coupling agent are also tested. Reinforced copolymer formulations are prepared by milling. Optimum curing times are determined with a torsion rheometer. Mechanical and rheological tests (stress‐strain behavior, tear resistance, hardness, interfacial strength, storage modulus, and loss tangent), show promising results for some materials, especially when looking for a reinforced product with low dissipation energy.
Isothermal crystallization of isotactic polypropylene in dotriacontane. I: Effect of nucleating agent addition on overall crystallization kinetics
Authors: Lim Gordon B. A. , Lloyd Douglas R.
Published: December 2004

The overall isothermal crystallization kinetics for nucleated and non‐nucleated isotactic polypropylene (iPP)‐dotriacontane systems was investigated. Adipic acid was used as the nucleating agent. Half‐time was determined via differential scanning calorimetry as a function of the experimentally controlled variables dilution, crystallization temperature, and the addition of nucleating agent. The influence of these variables on crystallization mechanism and spherulitic structure, as implied by the Avrami analysis, was determined. The influence of these variables on fold surface energy was examined by the Lauritzen and Hoffman analysis.
Effect of adhesion on the fracture toughness of calcium carbonate–filled polypropylene
Authors: Jancar J. , Dibenedetto A. T. , Dianselmo A.
Published: December 2004

The effect of adhesion on the strain energy release rate (Gc) and Charpy notched impact strength (NIS) of calcium carbonate (CaCO3)‐filled polypropylene (PP) at room temperature is investigated over a wide interval of particulate filler volume fractions. The concentration dependence of Gc and NIS are discussed in terms of competition between the effects of increasing stiffness, decreasing effective matrix cross section, and the transition from a plane strain to a plane stress mode of failure. In all cases the plane stress and plane strain limits of the critical strain energy release rate for initiation of cracks were not affected by the presence of the filler and are the same as those for neat matrix. In the case of no adhesion between components, the size of the crack tip plastic zone increases with increasing filler volume fraction (vf) because of the reduction of the material yield strength. In the region 0 < vf < 0.12, there is a mixed mode of failure, and the measured value of Gc for crack initiation increases steadily as the sample cross section approaches a fully plane stress state. The reduction in yield strength also results in the increase in Gc for crack propagation as reflected by an increase in NIS. Above vf= 0.12, the specimen cross section is in a fully plane stress state, and further increase in filler volume fraction (decrease in matrix effective cross section) has the net effect of reducing both Gc and NIS. In the case of “perfect” adhesion, the yield strength increases only slightly with vf. In the region 0 < yr < 0.05 there is also a mixed mode of failure, but the increase in Gc is much less than that for the no‐adhesion case since the size of the plastic zone in front of the crack is much smaller. Above vf= 0.05, the combined effects of increasing stiffness, reduction of the size of the plastic zone, and decreasing matrix cross section dominate the behavior, causing a steady reduction in both Gc and NIS. Good agreement was found between experimental data and calculations based on fracture mechanics principles.
Properties of the interphase in ternary polymer composites
Authors: Schaefer K. U. , Theisen A. , Hess M. , Kosfeld R.
Published: December 2004

Ternary systems consisting of polypropylene (PP), ethylene‐propylene‐dieneterpolymer (EPDM) and different types of inorganic fillers (kaolin, BaSO4) have been investigated with respect to their mechanical behavior. On the basis of an Interphase model, it was possible using the modified van der Poel equation to describe the temperature dependence of the storage modulus G′(T) and the loss modulus G″(T). The interphase properties G′(T) and G″(T) could be calculated.
A personal computer software program for coathanger die simulation
Authors: Arpin B. , Lafleur P. G. , Sanschagrin B.
Published: December 2004

A good extrusion die must distribute the polymer melt in the flow channel such that the material exits from the die with a uniform velocity and temperature. Coathanger dies are commonly used for the extrusion of plastic sheets and films. The die is usually provided with a straining bar allowing a regulation of the flowrate in the case of a poor design. But this, in turn, can affect temperature uniformity. Therefore, the design of coathanger die is a complex task which is mainly accomplished by trial and error in industry. Analyses of the flow in coathanger dies have been reported in the literature. Analytical and numerical approaches are used to solve this problem. The first one involves many simplifying assumptions: the most important ones being the unidirectional and isothermal flow of the polymer. Most numerical methods deal with a 2‐D geometry, but only a few of them have considered the non‐isothermal flow. A new model has been developed using a modified FAN method (Flow Analysis Network introduced by Tadmor) for the calculation of the 2‐D flow, coupled with a finite‐difference scheme for the calculation of temperature. The overall model can run on a PC with only a few minutes of calculation. Good agreement was obtained between experimental data and simulations.
In‐line optical monitoring of polymer injection molding
Authors: Bur Anthony J. , Wang Francis W. , Thomas Charles L. , Rose Joseph L.
Published: December 2004

An optical sensor, consisting of optical fibers to transmit light to and from the mold cavity, was constructed for the purpose of measuring the onset of polymer solidification during injection molding. The sensor was used to detect characteristic fluorescence radiation from a dye which had been doped into the resin at very low concentration. By measuring changes in fluorescence intensity it was possible to detect whether the state of the resin was liquid or solid. We observed that, as the resin cooled in the mold, the onset of solidification was indicated by highly characteristic and distinct changes in the fluorescence intensity/time profile. Application of the method involved the use of a calibration relationship between the fluorescence intensity and temperature of the doped polymer in order to determine the distict features which characterize the onset of solidification. Injection molding of a glass forming polymer (polystyrene) and a crystallizable polymer (polyethylene) was monitored by this technique.
Compatibilized linear low‐density polyethylene/isotactic polypropylene blends studied by positron annihilation lifetime spectroscopy
Authors: Flaris V. , Zipper M. D. , Simon G. P. , Hill A. J.
Published: December 2004

Positron annihilation lifetime spectroscopy (PALS), capable of probing free volume, is used to study the effect of compatibilizer concentration, compatibilizer type, and the effect of blend processing on the morphology and properties of an immiscible linear low‐density polyethylene/polypropylene system. It is proposed that improvement of fracture toughness due to compatibilization can be attributed to the packing (and bonding) at interfaces. Improved interfacial packing and bonding result in lower free volume concentration than expected from component additivity, with a concomitant increase in plastic deformation on impact.
Chemically oxidized polypyrrole: Influence of the experimental conditions on its electrical conductivity and morphology
Authors: Chen X. , Issi J‐P. , Devaux J. , Billaud D.
Published: December 2004

The effect of synthesis conditions on the electrical conductivity and the morphology of a chemically oxidized polypyrrole was investigated. It was found that the electrical conductivity of polypyrrole was strongly dependent on the pyrrole/FeCl3 ratio, which controls the redox potential of the reaction medium. The reaction temperature and the reaction duration also influence the electrical conductivity of the polypyrrole. A considerable influence of the nature of the solvent used on the aggregation state of polypyrrole particles was demonstrated. Optimal experimental conditions are proposed.
In situ composite: Phenolphthalein polyethersulfone—thermotropic liquid crystalline polymer blends
Authors: Li Gang , Yin Jinghua , Li Binyao , Zhuang Guoqing , Yang Yuming , Nicolais L.
Published: December 2004

Phase behavior, thermal, rheological and mechanical properties plus morphology have been studied for a binary polymer blend. The blend is phenolphthalein polyethersulfone (PES‐C) with a thermotropic liquid crystalline polymer (LCP), a condensation copolymer of p‐hydroxybenzoic acid with ethylene terephthalate (PHB‐PET). It was found that these two polymers from optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separation during heat treatment. However, melt mixed PES‐C/PHB‐PET blends were heterogeneous based upon DSC and DMA analysis and SEM examination. Addition of LCP in PES‐C resulted in a marked reduction of melt viscosity and thus improved processability. Compared to pure PES‐C, the charpy impact strength of the blend containing 2.5% LCP increased 2.5 times. Synergistic effects were also observed for the mechanical properties of blends containing < 10% LCP. Particulates, ribbons, and fibrils were found to be the typical morphological units of PHB‐PET in the PES‐C matrix, which depended upon the concentration of LCP and the processing conditions.
A study on interfacial adhesion of poly(vinylidene fluoride) with substrates in a multilayer structure
Authors: Whang Wha‐Tzong , Cheng Wen‐Hua
Published: December 2004

The peel force of a PVDF/3‐APS/Si joint and a PVDF/3‐APS/Al joint can reach the same level by treating the Si substrate with ⩾ 0.3% 3‐aminopropyltriethoxy silane (3‐APS) solution and treating the aluminum substrate with NH3 solution (pH 10.5) first and then with ⩾ 3% 3‐APS solution. Scanning electron micrographs show that the interfacial adhesion mechanisms of PVDF/3‐APS/Si joints and PVDF/3‐APS/Al joints are different. In the peel test, the PVDF [poly(vinylidene fluoride)] break surfaces from PVDF/3‐APS/Si joints reveal striations on the surface and less plastic deformation. The significant plastic deformation of the PVDF at the break surface may result from the deeper interpenetration of 3‐APS with PVDF in the PVDF/3‐APS/Al joint than in the PVDF/3‐APS/Si joint. The peel force of PVDF film/substrate joint depends on many factors: film thickness, peel rate, concentration of coupling agent, the treatment time of the coupling agent on the substrate, and the substrate pretreatment.
Image Analysis Procedures for Characterizing the Fractal Dimension of Fineparticles
Authors: Kaye Brian H. , Clark Garry G. , Leblanc John E. , Trottier Remi A.
Published: December 2004

Fractal geometry developed by Mandelbrot is finding many applications in the description of rugged fineparticles and fineparticle systems such as packed powder beds. In the earlier publications dealing with the fractal structure of fineparticle boundaries a great deal of the experimental work was carried out manually. This was time consuming and limited the amount of investigative work which could be undertaken in a given context. In this communication several algorithms for automating the evaluation of the fractal dimensions of rugged fineparticle boundaries by automated image analysis are explored. Comparative data generated by the various procedures are presented.
Analysis of the Inorganic Constituents of Particles on a Particle‐by‐Particle Basis using a Computerized SEM‐EDS System
Authors: Gomez Cesar O. , Austin Leonard G.
Published: December 2004

This paper is based on the development of the Moza‐Austin technique for characterizing thousands of coal particles by approximate analysis of the major inorganic constituents Ca, Al, Si, K, Na, Fe and S in each particle. The technique has sufficient sensitivity to work on small volumes, is fast enough to handle large number of particles within a reasonable period of time, and consists of scanning electron microscopy combined with energy dispersive x‐ray spectrometry (SEM‐EDS). A computerized SEM‐EDS system that allows the automated analysis of hundreds of particles per hour is described. The analysis is based on the location and tracing of exposed areas of particles embedded in a polished specimen, the selection of sampling points on the traced sections, the collection of an x‐ray spectrum from each sampled point for a defined period of time, and the processing of the x‐ray intensity to calculate point composition using ZAF corrections. Procedures for correcting for dead time, spectrum background, x‐ray detector efficiency and spectrum overlap are described. Problems and future work are discussed.
Size Separation of Particles from Aerosol Samples using Impactors and Cyclones
Authors: Büttner Helmut
Published: December 2004

Investigations are presented on particle separation in impactors, sampling cyclones and other precollectors. These devices are increasingly used for the characterization of particulate matter. Size selective samplers must be characterized by their grade efficiency curves. A new measuring procedure is presented, which permits the determination of the grade efficiency curves of various sampling devices. An optical particle counter and a vibrating orifice generator are used in these measurements. This calibration technique is fast and has a high resolution. Investigations were carried out on the influence of various parameters on the classification efficiency of impactors and sampling cyclones. Using the extensive data measured a better understanding and quantification of impactor and cyclone behaviour is developed which may improve their applications in particle sampling.
Application of the Straining Capture Mechanism in gaps to the measurement of particle concentration and size distribution
Authors: Cieślicki Krzystof
Published: December 2004

This paper attempts to answer the question of whether a measurement of the relative flow rate of a suspension of spheres, flowing under constant pressure drop through gaps of precisely determined geometry, may be utilised to measure the concentration and size distribution of the particles. A positive answer is possible only if several restrictions are imposed on the character of the flow, a maximum ratio of sphere diameter to gap height and a maximum number of captured particles. This answer is based on a model of the filtration process taking place in the gap and the consequent relationship between the flow characteristics of the gap and the number and diameter of the captured particles.
Determination of the Adhesivity on Acrylics of Fresh Coal Fly Ash Particles
Authors: Rafailidis Stilianos V. , Reizes John A.
Published: December 2004

The adhesivity of fresh coal fly ashes from two Australian power stations on Dralon‐T monofilaments has been experimentally analysed. It was found that one of the dusts was more adhesive to the fiber and its particles were also more strongly electrostatically charged. These obervations explain the reported large differences in the pressure loss across the fabric filters at the two stations. By precharging the particles, the technique can also be utilized in determining the adhesivity of fly ashes which carry relatively small natural electrostatic charging.
A Laser Multi‐focus System for the Measurement of Particle Size, velocity and refractive index
Authors: Nakatani Noboru , Kohri Shigetoshi , Yamada Tomoharu , Sakabe Toshiya
Published: December 2004

A laser multi‐focus velocimeter (LMFV) for measuring particle diameter, velocity and refractive index simultaneously is described. A phase diffraction grating with pulse width modulation is used to obtain several focal points with almost equal intensity and to construct the optical system. The fringes of the LMFV using multi‐beam interference have a sharper intensity distribution and wider period than those of a laser Doppler velocimeter using two‐beam interference. Therefore, the LMFV makes it possible to measure high velocities and large particle diameters with high accuracy. The validity of the method was confirmed theoretically and experimentally.
Light Scattering at a Small Angle with the Use of Lorenz‐Mie Theory in Particle Sizing
Authors: Mroczka Janusz
Published: December 2004

Problems connected with particle sizing with the use of radiation power measurement at a small angle (θ = 0.5° – 10°) where the Lorenz‐Mie theory is a mathematical model of the phenomenon are discussed. As an example, a computer program LICZ, allowing for the shortest calculation time, yet preserving satisfactory accuracy of calculations, is considered.
Size Characterization of Liquid‐Borne Particles by light scattering counters
Authors: Lee Haeok Skarda , Chae Seung Ki , Liu Benjamin Y. H.
Published: December 2004

The sizing accuracy of a commercially available laser optical liquid‐borne particle counter is investigated. A calibration study, using aqueous suspensions of non‐absorbing, monodisperse, spherical polymer particles, and a study using suspensions of non‐spherical polydisperse, alumina particles are conducted. The experimental results from the spherical polymer study show an excellent agreement with the theoretical Mie light scattering calculations. The accuracy of the spherical polymer sizing is shown to be within 20% of the actual size. The alumina particle readings are compared to the readings of four different particle sizing instruments and to scanning electron microscope pictures. Although quantitative comparisons are difficult to make between the instruments, the results show a good agreement for the batch of particles with a narrower size distribution.
The Characterization of Water‐Droplet Aerosols by polytec optical particle analysers
Authors: Mitchell Jolyon P. , Nichols Alan L. , van Santen Anton
Published: December 2004

A single‐stage impactor has been used to calibrate a Polytec HC‐15/1 optical aerosol analyser so that this instrument can be used to study water droplets from approximately 1 to 20 μm aerodynamic diameter. The resulting calibration data were in good agreement with calculations based on Mie light scattering theory, and gave a conversion factor of 2.0 ± 0.2 between polystyrene latex microspheres and water droplets of the same aerodynamic diameter.

Monodisperse water droplets were sampled by a Polytec HC‐70/2 analyser, calibrated using the conversion factor of 2.0. The measured count median diameter agreed closely with that predicted from the well‐defined operating conditions of the vibrating orifice aerosol generator. Size measurements of a polydisperse water‐droplet spray were also undertaken with both a Malvern laser diffractometer and a Polytec HC‐15 analyser; good agreement was achieved between the two techniques.