bluuebunny/crossref_metadata_2025 huggingface dataset:
A mathematical model for computer simulation of a direct continuous esterification process between terephthalic acid and ethylene glycol
Authors: Yamada T. , Imamura Y.
Published: December 2004

To study the effect of potassium titanium oxyoxalate on the esterification reaction of terephthalic acid (TPA) and ethylene glycol (EG) in the first tank reactor of TPA/EG continuous esterification, experiments at various addition rates of potassium titanium oxyoxalate were made in the pilot plant. Potassium titanium oxyoxalate accelerated the esterification reaction of TPA and EG. Also, reaction rate constants of the reaction scheme reported in a previous report were fitted with the experimental results, and the calculated values of physical properties of oligomers obtained from these reaction rate constants showed relatively good agreement with experimentally obtained physical properties of the oligomers. The effect of potassium titanium oxyoxalate on the reaction rate constants was expressed by a set of seven equations:

equation image

Using the resultant reaction rate constants, the esterification reaction at various addition rates of potassium titanium oxyoxalate were stimulated and the following conclusions drawn:

Under low pressure close to atmospheric, when the amount of water in the reaction mixture is very low, the decomposition of potassium titanium oxyoxalate proceeds slowly and decomposition can be practically neglected.

Potassium titanium oxyoxalate accelerates the esterification reaction.

Potassium titanium oxyoxalate mainly accelerates the main reactions and its effects on side reactions are rather weak. As a result, the higher the addition rate of potassium titanium oxyoxalate, the lower the values of AV and DEG, as is preferable.
Fully developed multilayer polymer flows in slits and annuli
Authors: Nordberg M. E. , Winter H. H.
Published: December 2004

A numerical method has been developed for simulating fully developed multilayer shear flows of non‐Newtonian fluids with arbitrary viscosity functions. Poiseuille and combined Poiseuille/Couette flows in both slits arid annuli may be modeled. The method employs a finite difference system where grid points lie on streamlines and move to their correct positions as the solution procedure converges. Interfaces are easily handled as particular stream lines with the equation of motion replaced by a boundary condition. The method is stable for high interface viscosity ratios and readily handles a large number of layers. Many authors have employed power law models to model multi‐layer non‐Newtonian flows. We find that the power law is sufficient to predict pressure gradients and interface positions in most cases, but gives unrealistically flat velocity profiles, even when truncated at finite viscosity. Results are presented for the Carreau fluid and for the rubber‐like liquid with shear thinning via Wagner's strain functional.
Shrinkage of low‐density polyethylene film
Authors: Liu Tuomin , Harrison I. R.
Published: December 2004

When blown films of low‐density polyethylene are heated above their melting point (Tm) they shrink to an unoriented state at a conveniently measurable, rate. Curves of contraction as a function of time have been measured at different temperatures ranging from 120°C to 200°C. The contraction curves for shrinkage in the machine direction obtained at different temperatures are superimposable by a lateral shift along the log‐time axis. A master contraction curve, a portion of the retardation spectrum, and the activation energy are obtained. Shrinkage data for low‐density polyethylene films with different thicknesses were analyzed and a correlation was found between contraction and dichroic ratio. This correlation indicates that thermal contraction data can be used as a qualitative measurement of orientation in low‐density polyethylene film.
Compensation effects in viscosity‐temperature dependence of polymer melts
Authors: Tanguy P. A. , Choplin L. , Hurez P.
Published: December 2004

The thermal dependence of the parameters of the Carreau A model of viscosity has been investigated for 13 polymeric resins. It was shown that the zero‐shear viscosity and the time constant obey an Arrhenius‐type law and that, for these parameters, compensation effects are exhibited. The shear‐thinning index was found to be fairly independent of temperature. An important consequence of a compensation effect is that only one determination of a parameter at a given temperature gives the complete temperature‐dependence of this parameter.
Photographed impact of continuous fiber composites
Authors: Moore D. R. , Prediger R. S.
Published: December 2004

Instrumented falling weight impact is conducted on eight different continuous carbon fiber composites. During impact, photography of the tension surface of the specimens enables crack propagation to be monitored. One photograph per specimen is taken. Measurements of integral crack length is related to corresponding absorbed energies during impact. These results enable an apparent value of Gc to be determined. These are tabulated for the eight advanced composite samples.
Effect of fillers on the rheological behavior of thermoplastic 1,2 polybutadiene rubber
Authors: Bhagawan S. S. , Tripathy D. K. , De S. K. , Sharma S. K. , Ramamurthy K.
Published: December 2004

The influence of fillers like clay, silica, and carbon black on the rheological properties of 1,2 polybutadiene has been studied using a capillary rheometer. Silica filled compound exhibited the highest viscosity and clay filled compound the lowest viscosity at all shear rates. The effect of filler loading and temperature on the Theological behavior has also been studied. Smooth extrudates were obtained in most of the cases and die swell was lower for silica and carbon black filled compounds than for clay filled compounds. Rheograms of different 1,2 polybutadiene systems have been found to merge into a master curve using modified viscosity and shear rate functions that contain melt flow index as a parameter.
Fracture toughness of filled polypropylene copolymer systems
Authors: Fernando P. L.
Published: December 2004

The impact strength to stiffness balance of a toughened polypropylene copolymer was modified through the addition of mineral fillers. The stiffness was improved over the base resin value for all formulations. However, the impact strength exhibited complex behavior. The fracture toughness Gc calculated using the linear elastic fracture mechanics theory was indicative of the materials resistance to crack propagation. The Gc values were modified significantly with the addition of fillers and for some formulations was greater than the base resin value. The LEFM analysis indicates that this is due to an increase in the damage zone size rp where the energy absorbing mechanisms are concentrated. However, the specific energy absorbed per unit volume decreased with the addition of fillers. The total energy to fracture measured using unnotched samples was indicative of crack initiation and crack propagation energies. This upper bound value decreased for all formulations indicating a reduction in the crack initiation resistance, in the presence of stress concentrating heterogeneities in the filled systems.
A deformation induced order‐disorder transition in isotactic polypropylene
Authors: Saraf Ravi F. , Porter Roger S.
Published: December 2004

In this study, isotactic polypropylene (i‐PP) has been deformed by uniaxial compression to draw ratios up to 16×, and at draw temperatures from 30°C to 140°C. An order‐disorder transition in the crystals is observed at draw temperatures well above the stability limit, 70°C, reported for the disordered phase; Furthermore, this disordered phase (called smectic) is found to induce ductility and improve the efficiency of draw. The deformation induced smectic phase has been characterized using WAXS, DSC, and on‐line compression load versus draw ratio measurements. In consequence, a set of process conditions are offered to optimize draw. A mechanism for plastic deformation of i‐PP is also suggested, using the smectic phase as a probe.
Properties and phase separation of reaction injection molded and solution polymerized polyureas as a function of hard block content
Authors: Willkomm Wayne R. , Chen Z. S. , Macosko C. W. , Gobran David A. , Thomas Edwin L.
Published: December 2004

A series of amine terminated polypropylene oxide based thermoplastic polyureas with hard segment contents of 30%, 50%, and 70 percent were synthesized via solution polymerization and reaction injection molding (RIM). Amine terminated polypropylene oxide (PPO‐NH2) of Mn = 2000 was used as the soft segment and 4,4′‐diphenylme‐thanediisocyanate (MDI) extended with diethyltoluenediamine (DETDA) as the hard segment. These polyureas are linear, amorphous, and phase separated. Polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical spectroscopy (DMS), small angle X‐ray scattering (SAXS), and tensile testing. RIM polyureas had significantly lower molecular weights than solution polymerized polyureas, but their mechanical properties did not suffer, RIM polyureas have poorer phase separation than solution polyureas as evidenced by DSC, DMS, and SAXS, especially at high hard segment levels. SAXS shows phase separation levels of up to 100 percent for low hard segment polyureas and down to 10 percent for high hard segment RIM polyurea. DSC found no evidence of a hard segment glass transition, and the evidence from DMS was inconclusive. In addition to polymer characterization, demolding behavior was studied. The 30 percent hard segment was always tough and elastomeric, while the 70 percent hard segment was always very brittle. The 50 percent hard segment showed the greatest variation in properties, ranging from very brittle to very though as mold temperature and in‐mold time were increased. Demold brittleness is explained by the presence of low molecular weight DETDA/MDI oligomers on demolding, which continue to react on aging.
Wire bond behavior during molding operations of electronic packages
Authors: Nguyen L. T.
Published: December 2004

This paper presents some modeling work on the behavior of wire bonds during a typical transfer molding operation. In order to fill up the small recesses in a production size mold, transfer pressures as high as 1.000 psi are commonly required. The large driving pressure is potentially harmful to the fragile wire bonds. Lit the worst case scenario, the highly viscous melt front may cause enough shearing action to lift off the wire bonds completely. More often, however, wire sweeping is reported as one of the major causes of shorts in devices where long interconnect wires are looped between bond pads. Several interdependent factors govern the extent of wire sweep in a mold cavity of arbitrary geometry. The dimensions of the cavity, for instance, dictate the velocity of the melt front profile with the corresponding flow stresses and shear rates. The location of the chip to be encapsulated similarly influences the plastic filing pattern. So does the configuration of the particular chip design (e.g. planar vs recessed lead frames). Naturally, the severity of the problem is also controlled by the nature of the wires used during the bonding. For example, wire sweep may be controlled to a certain degree by tailoring the wire modulus to offer resiliency and spring‐ back after the melt front has swept across, but prior to curing. Furthermore, a low drag coefficient would also be obtained if some measure of control on the shape of the wire (e.g. circular vs rectangular cross‐section) or the pro‐ file exposed (e.g. angle of orientation of the wires with respect to the flow) is exerted.
Application of thermogravimetric‐mass spectroscopy analysis for polymer characterization
Authors: Jones E. G. , Pedrick D. L. , Goldfarb I. J.
Published: December 2004

A general description of the thermpgravimetric‐mass spectroscopy (TG‐MS) technique is presented. Advantages and limitations are discussed with respect to other mass‐spectral techniques, and a few examples of applications of TG‐MS to the study of the thermal degradation of polymers are given.
Experimental and mathematical treatment of transfer pot temperature for thermosets
Authors: Manzione L. T. , Poelzing G. W. , Progelhof R. C.
Published: December 2004

The heating and flow behavior of thermoset molding compound within the pot of a transfer molding process were studied with flow visualization experiments and a mathematical model. The flow pattern within the pot was found to be a stagnation point flow. The extrudate temperature was only 10°C–15°C above the preheat temperature, and it was relatively constant except for start‐up and termination transients. The chemical conversion of the extrudate was well below the conversion to gel for typical process conditions. Variations in pot diameter, preheat temperature, and pot temperature were also examined.
Chlorinated high density polyethylene. I. Chain characterization
Authors: Chang B. H. , Zeigler R. , Hiltner A.
Published: December 2004

High density polyethylene has been chlorinated by three different methods: in suspension and in solutions of two different solvents. Carbon‐13 NMR and infrared analysis show that chlorination in chlorobenzene solution leads to statistically random distribution while chlorination in suspension gives highly blocky substitution. An intermediate distribution was obtained by chlorination in tetrachloroethane solution.
Critical stress intensity factor of epoxy mortar
Authors: Dharmarajan N. , Vipulanandan C.
Published: December 2004

Fracture behavior of epoxy mortar was investigated in Mode I fracture using single edge notched beams with varying notch depth and beam thickness. The beams were loaded in both 3‐point and 4‐point bending. Influence of polymer content and temperature on the fracture behavior of epoxy mortar was studied using uniform Ottawa 20–30 sand. The polymer content was varied between 10 percent and 18 percent of the total weight of the composite. The temperature was varied between 22°C and 120°C. The flexural strength of the polymer mortar increases with increase in polymer content while the flexural modulus goes through a maximum. The critical stress intensity factor (KIC) was determined by several methods including compliance method (based on crack mouth opening displacement) and finite element analysis. TheKICfor epoxy mortar increases with increase in polymer content and epoxy mortar strength but decreases with increase in temperature. The critical stress intensity factor of epoxy mortar is represented in terms of polymer content and polymer strength or stiffness. Numerical tests based on random sampling and stratified sampling procedures were performed to substantiate the experimentally observed fracture toughness values of epoxy mortar.
Stored energy of cold work in polystyrene
Authors: Chang Benjamin Tai‐An , Li J. C. M.
Published: December 2004

The energy stored in polystyrene after plastic deformation is measured by the differential scanning calorimetry (DSC) technique. Similar to metals, the stored energy increases with plastic straining, first rapidly, and then more slowly, and finally the stored energy seems to approach a saturation value (about 1 cal/gram). By comparing to the plastic work done, the fraction stored ranges from 30 percent after 10 percent compression to 10 percent after 60 percent compression. The fraction is about twice as large as that of copper. The release of stored energy has two distinct parts, one below Tg and the other above Tg. Most of the strain recovery seems to accompany the second part. By using the Kissinger plot, the second part has an activation energy, of 142 kcal/mole which is about 10 percent larger than that of compressive strain recovery.
Physical aging of amorphous poly(etheretherketone) (PEEK)
Authors: Carfagna C. , Amendola E. , D'Amore A. , Nicolais L.
Published: December 2004

Thermal treatment of amorphous poly(aryl‐ether‐ether ketone) below the glass transition temperature has been studied. The extent of aging was measured by differential scanning calorimetry. X‐ray and Fourier transform infrared spectra were used to study both melt‐cast and annealed samples. The effect of the thermal treatment of viscoelastic response was evaluated using creep tests. Aging has been shown to be accompanied by a marked change in the transport properties of the material.
Analysis of the performance of cooling extruders in thermoplastic foam extrusion
Authors: Han Chang Dae
Published: December 2004

The performance of cooling extruders widely used in thermoplastic foam extrusion was analyzed, by numerically solving the equations of motion and heat transfer. Analysis of cooling extruders does not require a consideration of the melting behavior of polymers, thus simplifying the system equations considerably. The flow geometry analyzed was an unwound screw channel of a single‐screw extruder, i.e., a rectangular channel of uniform height followed by diverging and converging sections. Due to the cooling of both the extruder barrel and the screw, the heat transfer equation considered includes the terms describing the convective heat transfer in the down‐channel direction and the conductive heat transfer in the cross‐channel direction, in addition to the terms describing the viscous shear heating. For the analysis, a power‐law model was used as the constitutive rheologlcal equation, describing the viscosities of a mixture of a fluorocarbon blowing agent and a low‐density polyethylene melt (or polystyrene melt). The parameters in the Theological model were determined using the data of Han and Ma (13). In obtaining numerical solutions of the equations of motion, an integration method was employed to overcome the problem of numerical instabilities. The present analysis predicts the profiles of developing temperature and velocity in the down‐channel direction, and the profiles of temperature, velocity, shear rate, and viscosity in the cross‐channel direction. In presenting the results of computer simulation, emphasis is placed on the effects of cooling the extruder barrel and screw on the performance of cooling extruders, in terms of the pressure drops along the extruder axis and the mechanical power consumption. This study provides a rational basis for the design of cooling extruders widely used in thermoplastic foam extrusion and for the selection of optimum extrusion conditions in producing thermoplastic foams.
Time‐temperature superposition and physical aging in amorphous polymers
Authors: Matsumoto D. S.
Published: December 2004

In the past, time‐temperature superposition has been used to extend the time scale of creep tests in polymers from the short times easily obtained in the laboratory to long times seen in actual use. A fundamental assumption of time‐temperature superposition is, however, that the polymer does not change in structure as a function of time. Because ductile amorphous thermoplastics physically age below Tg, the structure of the polymer changes on a time scale comparable to the time duration of the creep test. Thus, the time‐temperature superposition prediction greatly exaggerates the amount of creep in amorphous thermoplastics. For samples aged at the test temperature for one hour before testing, the difference between the time‐temperature superposition prediction and the actual creep data after 10 days is greater than a factor of ten in time.
The effect of annealing at 135° on the mechanical properties of injection molded high density polyethylene‐polypropylene blends
Authors: Varin R. A. , Djokovic D.
Published: December 2004

The effect of annealing at 135°C for 5 hours on the tensile properties of mechanically mixed and then injection molded high density polyethylene (HDPE) and polypropylene (PP) blends has been investigated. Both the tangent elastic modulus and the tensile strength at yield exhibit a non‐linear behavior versus blend composition with a minimum of properties typical for incompatible blends. Annealing substantially improves mechanical properties of pure components and blends (20 percent increase in the yield strength of pure components and blends and the modulus of pure components, and ∼40 percent increase in the modulus of 50/50 blends) but the property behavior versus composition is still nonlinear. Scanning electron microscopy studies of fracture surfaces of blends seems to indicate some improvement in bonding between phases as a result of annealing, Both the elastic modulus and yield strength fit extremely well to the modified “rule of mixtures” equation in the general form: Mb = MPEφPE + MPPφPP + ΔMPE/PPφPEφPP where Mb is the blend property, MPE and MPP are properties of pure PE and PP components, φPE and φPP are weight fractions of PE and PP, and ΔMPE/PP is the interaction term being a measure of the deviation from simple additivity.
Mechanical properties of rigid thermoplastic foams—Part I: Experimental considerations
Authors: Stokes V. K. , Nimmer R. P. , Ysseldyke D. A.
Published: December 2004

The through‐thickness variation in the porosity of structural foam material is known to result in different “material properties” when mechanics based on homogeneous materials is used to interpret data from standard tensile and bend tests. Unresolved issues relating to structural design include the specification of the most useful test specimen, the identification of useful material properties, and the application of these properties to part design and analysis. This paper develops procedures for determining the mechanical properties of rigid thermoplastic structural foams, and for the application of these properties to the design of load‐bearing components. Rather than molded specimens, it is suggested that specimens cut from large, edge‐gated plates be used for determining mechanical properties of structural foams. By modeling foams as continuous but nonhomogeneous materials, it is shown that data from simple tensile and flexural tests can be used in structural analysis to systematically account for the through‐thickness variation of material properties.
Mechanical properties of rigid thermoplastic foams—Part II: Stiffness and strength data for modified polyphenylene oxide foams
Authors: Nimmer R. P. , Stokes V. K. , Ysseldyke D. A.
Published: December 2004

The through‐thickness variation in the porosity of structural foam material is known to result in different “material properties” when mechanics based on homogeneous materials is used to interpret data from standard tensile and bend tests. Procedures for determining the mechanical properties of rigid thermoplastic structural foams and for the application of these properties to the design of load‐bearing components were developed in a companion paper. This paper reports the mechanical properties of modified polyphenylene oxide foams, such as elastic moduli, ultimate stress and strain, as determined by tests on specimens cut from large, edge‐gated foam plates. Tests were conducted to study plate‐to‐plate variations in properties and to evaluate the effect of specimen thickness. Correlations of tensile and flexural data with the average specimen density are also discussed.
Dielectric properties of medium thermal black‐polyethylene systems
Authors: Yacubowicz J. , Narkis M. , Benguigui L.
Published: December 2004

The dielectric properties of thermoplastic and cross‐linked polyethylene compounds with a low structure medium thermal carbon black are described in the frequency range between 30 and 8000 kHz as a function of frequency, temperature, and carbon black loading. Very high values of the dielectric constant were obtained for the conductive samples. The systems investigated are shown to follow percolative type models with experimental critical exponents in good agreement with the predicted values. The dielectric constant increases slowly with the carbon black concentration up to roughly the percolation concentration, then increases rapidly, and subsequently decreases at the higher black loadings. The dissipation factor‐concentration curves show maximum values in the vicinity of the percolation concentration. The dielectric properties of these systems are discussed in terms of interfacial Maxwell‐Wagner polarization effects.
Dynamic mechanical behavior of copolymers containing carbon black
Authors: Gandhi K. , Salovey R.
Published: December 2004

The storage and loss moduli of random copolymers of styrene and butyl methacrylate containing carbon black of varied surface area were determined by dynamic mechanical analysis at several temperatures about 100°C above the glass‐transition temperature, Tg. At low frequencies, the pure polymers exhibit linear double log plots of moduli against frequency, with slopes of unity and approaching two for G″ and G′, respectively. With the addition of carbon black filler, both G′ and G″ become independent of frequency and temperature at low frequencies, consistent with yield behavior arid the formation of a carbon black network. The limiting dynamic complex modulus exceeds the yield stress from steady shear rheology, perhaps indicating the extent of the carbon black network, which was highest for low‐molecular‐weight copolymer and polystyrene. The filled random copolymers behaved Theologically like similarly filled polystyrenes of comparable molecular weights. Plasticization effects observed in the steady shear rheology of filled copolymers containing small concentrations of carbon black were not observed in dynamic mechanical analysis, although dynamic moduli converge at high frequency.
Service life of crosslinked polyethylene as high voltage cable insulation
Authors: Bernstein Bruce S.
Published: December 2004

This paper provides a summary of four EPRI‐sponsored contracts that studied the physico‐chemical characteristics and thermal and electrical behavior of unaged and service‐aged crosslinked polyethylene (XLPE)—insulated cables, and sections of the insulation obtained from this extruded cable. It has been demonstrated that volatile components generated primarily from the peroxideinduced crosslinking process can be defined and quantitatively measured. The morphology of the aged and unaged XLPE extruded insulation can be defined, and the thermal behavior on a micro (morphology changes) and macro (cable aging) level compared. Changes in microvoid level due to melting and recrystallization during cable operation appear to correlate with the limited amount of ac breakdown strength data obtained, and thermal overload of the cable conductor causes complete melting (and recrystallization on cooling) reducing the microvoid level. A single thermal overload alters the morphology but many thermal overloads are required to drive off the volatiles.
Influence of rubber content on static and dynamic properties of polystyrene
Authors: Sauer J. A. , Trent J. , Chen C. C.
Published: December 2004

Mechanical properties, deformation modes under both uniaxial tension and compression, low temperature mechanical relaxation behavior, and resistance to fracture under dynamic loading have been investigated for a medium impact grade of polystyrene, Shear yielding is the dominant mode of plastic deformation in compression while matrix crazing, together with some tearing and cavitation of the rubber phase, occurs in tension. The craze microstructure, as determined by transmission electron microscopy (TEM), is typical of that noted in polystyrene, with sharp craze‐bulk interfaces and a characteristic midrib section. The presence of a third phase, possibly a processing aid, is evident in the TEM scans and in the dynamic mechanical data. The present data, together with the data obtained on polystyrene and on high impact polystyrene, are used to show the strong influence of rubber content on various mechanical properties, such as the tensile craze yielding stress, ductility, compression yield strength, degree of strain softening, and fatigue durability.
A comparative study of structure‐property relationships in low‐profile polyester matrices
Authors: Lam Patrick W. K.
Published: December 2004

Structure‐property relationships of polyester matrices containing various low profile additives such as poly(vinylacetate), polyurethane, poly(methyl methacrylate), polystyrene, and polycaprolactone were studied. The morphology and particle size of the dispersed phases in the polyester matrices are very dependent upon the type of low profile additives incorporated in the cured resins. Microvoids which are responsible for the degradation of physical properties of resin matrices are usually observed in the polyester phase and/or the dispersed phase of the low‐profile resin matrices. Low profile additives, in general, lower the glass transition temperatures of polyester matrices, slightly increase the loss moduli and the loss factors, and slightly decrease the storage moduli. These polymeric additives also degrade tensile properties and improve the fracture toughness of polyester matrices, but do not have significant effects on the thermal stability.
Polymer blend containing a thermotropic polyester with long flexible spacer in the main chain
Authors: Shin Boo Young , Chung In Jae
Published: December 2004

Polymer blends of nylon 66 and thermotropic polyester with long flexible spacers in the main chains were prepared by melt mixing. The samples were made as single filaments by passing the polymer blend through a small and round die of a capillary rheometer. Mechanical properties of blends showed that the modulus and strength of nylon 66 could be improved without reduction of extensibility. The morphology of fractured surfaces was observed by a scanning electron microscope (SEM). It showed that the microfibrillar structure of a thermotropic polyester was formed by extensional flow while the spherical and ellipsoidal particles in the nylon 66 (matrix polymer) were produced by shear flow. The polyester particles were occasionally covered with adhering matrix polymer because of good adhesion between these two polymers. They were highly elongated by tensile stress without loss of elongational characteristics of blends. This fact was explained by very good adhesion between the two phases.
Polyester‐polystyrene block copolymers and their influence on phase morphology and mechanical properties in polymer blends
Authors: Yoshida M. , Ma J. J. , Min K. , White J. L. , Quirk R. P.
Published: December 2004

New block copolymers of polystyrene with polyesters have been synthesized and investigated as compatibilizing agents. The addition of block copolymers in immiscible blends of polybutylene terephthalate and (i) polystyrene, (ii) polystyrene/poly(2,6‐dimethyl 1,4‐phenylene oxide) as well as (iii) high impact polystyrene drastically reduced the dimensions of the dispersed phase and stabilized the phase growth with annealing time. Stress‐strain curves for the binary blends indicate brittle behavior. The addition of more than 10 wt% of block copolymers transforms their brittle characteristics to ductile behavior.
Observation of carbon black agglomerate dispersion in simple shear flows
Authors: Rwei S. P. , Manas‐Zloczower I. , Feke D. L.
Published: December 2004

Experiments aimed at studying the mechanisms of agglomerate breakup due to the application of a simple shear flow field were performed in a cone and plate transparent device. Spherical compacts of carbon black (diameters 1‐2 mm) in a range of different porosites were used in the experiments. Two distinct breakup mechanisms, denoted as “rupture” and “erosion”, were observed. The critical stress for erosion was found to be smaller than that for rupture. Once erosion starts, it continues for very long times. Rupture occurs shortly after reaching a critical stress and concludes abruptly. For this analysis of rupture, the dimen‐sionless group \documentclass{article}\pagestyle{empty}\begin{document}$\alpha {\rm = \{ }\eta {\rm .}\mathop \gamma \limits^{\rm .} {\rm /K'}\phi ^{\rm 4} {\rm \} }$\end{document}, which is the ratio of applied stress to cohesive strength, was found to be a significant parameter for determining the final particle size distribution. The size analysis of fragments produced by shearing pellets for 1 minute showed a lognormal distribution function.
Yield behavior of polypropylene filled with CaC03 and Mg(OH)2. I: “Zero” interfacial adhesion
Authors: Jančář Josef , Kučera Jaroslav
Published: December 2004

The composition dependence of tensile yield stress (σyc), and the effects of filler particle shape and surface treatment were investigated for polypropylene (PP) filled with CaCO3 or with Mg(OH)2. Poor adhesion between PP and CaCO3 accounted for a decrease of σyc with increasing σf. In spite of the poor adhesion between PP and Mg(OH)2, σyc either slowly decreased with increasing Vf or remained constant up to Vf = 0.25. Surface treatment of the fillers facilitated better dispersion in PP. On the other hand, σyc was reduced due to the lower thermodynamic work of adhesion (WA). The semiempirical one‐parameter equation proposed by Turczanyi, Pukanszky, and Tüdüs (TPT) was considered plausible and was employed in the study of the effects of matrix‐filler interaction.
Effect of strain rate and temperature on the performance of epoxy mortar
Authors: Vipulanandan C. , Mebarkia S.
Published: December 2004

The behavior of epoxy mortar was studied under various curing conditions, temperature and strain rate. The effect of aggregate size and distribution on the mechanical properties of epoxy mortar was also studied. Epoxy mortar with a uniform fine sand was cured at various temperatures to determine the optimum curing condition. The strain rate was varied between 0.01 to 6 percent strain per minute and the testing temperature between 22°C and 80°C. The strength, modulus, and compressive strain‐strain relationship of polymer mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of epoxy mortar are quantified. Compared to the uniformly graded fine aggregate fillers the gap‐graded aggregates produced polymer mortar with better mechanical properties. The compressive modulus and splitting tensile strength of epoxy mortar are related to their compressive strength. A new nonlinear constitutive model is proposed to predict the complete compressive stress‐strain behavior of epoxy mortar. The constitutive relationship parameters are also related to the testing temperature and logarithmic strain rate.
Relationships in a bismaleimide resin system. Part II: Thermomechanical properties
Authors: Donnellan Thomas M. , Roylance David
Published: December 2004

A range of bismaleimide resins of differing network structure was produced both by varying the ratios of N,N′‐bismaleimido‐4,4′‐diphenylmethane (BMI) and methylene dianiline (MDA), and also by the use of different thermal processing cycles. Characterization of the resins by a variety of mechanical, physical, and micrographic techniques showed that properties such as modulus and yield strength varied directly with crosslink density and its associated free volume. Fracture toughness was found to increase as the crosslink density decreased, and microscopic investigation of the resin fracture surfaces identified characteristics which correlated with the resin fracture toughness.
Study of suspension polymerization of styrene with a circular loop reactor
Authors: Hosogai Kazuhiko , Tanaka Masato
Published: December 2004

A circular loop reactor was devised and used to study the suspension polymerization of styrene. The transient droplet diameter distributions and the final particle size distributions were measured by changing the impeller diameter and the impeller speed. The effects of the impeller diameter on the size distributions and mean sizes of the final polymer particles were investigated. In the case of lower mixing power, the mean polymer droplet diameters depend upon impeller diameter in the early stage of polymerization, but become almost identical irrespective of the impeller diameter after the middle stage. In the case of higher mixing power, the mean polymer droplet diameters are almost identical irrespective of the impeller diameter throughout polymerization. The final mean particle sizes are correlated only with mixing power.
Non‐Isothermal crystallization of isotactic polypropylene in dotriacontane. I: Effects of dilution, cooling rate, and nucleating agent addition on overall crystallization kinetics
Authors: Lim Gordon B. A. , Lloyd Douglas R.
Published: December 2004

The overall non‐isothermal crystallization kinetics for nucleated and non‐nucleated isotactic polypropylene (iPP) in dotriacontane systems was investigated. Adipic acid was used as the nucleating agent. Crystallization peak temperature was determined via differential scanning calorimetry as a function of the experimentally controlled variables iPP concentration, cooling rate, and nucleating agent concentration. The influence of these variables on crystallization mechanism and spherulitic structure as implied by the Ozawa and Ziabicki analyses was determined. The non‐isothermal crystallization kinetics presented here are the first for iPP‐diluent systems with and without nucleating agent.
Polybenzimidazole and polysulfone blends
Authors: Chung Tai‐Shung , Glick Morton , Powers Edward J.
Published: December 2004

Polybenzimidazole (PBI) and polysulfone (PS) do not form miscible blends; however, the tensile modulus and strength of their blend fibers are comparable to, or better than, that of PBI fibers, depending on process conditions. Fibers spun from an 80/20 PBI/PS solution blend have PBI‐like LOI (limiting oxygen indices) and flame shrinkage behavior. Sulfonation and stabilization of this fiber improve its thermal properties. The process window for these blend fibers has been determined. There was no aging phenomenon on as‐spun PBI/PS blend fibers, while as‐spun fibers made from PBI/polyarylate (PA) and PBI/high modulus aramides (HMA) exhibited remarkable aging effects on fiber properties. This difference probably arises from the fact that (1) the former is not a miscible blend, while the latter are; and (2) the former does not have hydrolysis groups, such as ester and amide groups, as that in the PA and HMA systems.
Modeling of the Dynamics of Water and R‐11 blown polyurethane foam formation
Authors: Baser S. A. , Khakhar D. V.
Published: December 2004

Polyurethane foam formation involves both polymerization and expansion processes. The dynamics of the water and R‐11 blown foams depend on the rates of chemical and physical blowing processes, along with the rate of viscosity increase of the reacting mixture. Experiments were carried out to study the dynamics of free rising, water and R‐11 blown rigid polyurethane foams. The density and temperature change during the foam formation were monitored. A theoretical model was developed to predict the density and temperature variation with time. In the model, the physical blowing agent (R‐11) evaporation process is assumed to be heat generation–controlled and the carbon dioxide generation process to be controlled by the rate of the water‐isocyanate reaction. The kinetic parameters of the reactions of isocyanate with polyol and water were obtained separately and were asssumed to be independent of each other. The water‐isocyanate reaction appears to follow first‐order kinetics with respect to concentration of water. The theoretical predictions of the model show good agreement with the experimental data for density variation with time. The model predictions for temperature rise also match experimental data, except at the later stages of foaming when it is found to be slower than the experimental measurements. However, this deviation does not affect the dynamics of density change since it occurs after the completion of the expansion process.
A finite element model for complex profile calibration
Authors: Sheehy P. , Tanguy P. A. , Blouin D.
Published: December 2004

A new finite element model named Corrected Slice Method (CSM) has been developed to cope with three‐dimensional vacuum cooling calibrator problems. Such problems appear whenever the cooling channel lay‐out comprises transverse channels in the calibrator. The CSM is an extension of the 2D approach (8), which takes into account the axial heat fluxes within the calibrator. The proposed model was validated by comparing the numerical results obtained on a test problem with a rigorous finite element approach. Moreover, a real complex profile‐calibrator system was simulated in order to illustrate the full performance of the porposed method.
Measurement of crosslinking degree for electron beam irradiated block copolymers
Authors: Kanbara Hisashige , Huang Samuel J. , Johnson Julian F.
Published: December 2004

The molecular weight between crosslinking junctions (Mc) of styrene‐butadiene‐styrene (SBS) and that of styrene‐isoprene‐styrene (SIS) irradiated by electron beams (5 Mrad to 100 Mrad) was measured by dynamic modulus, glass transition temperature, static modulus, and swelling. The change in dynamic modulus at low temperature was smaller than that at high temperature in both SBS and SIS. The shift of Tg to higher temperature was observed in both SBS, and SIS systems except for 100 Mrad of SIS. Both dynamic and static moduli increased with irradiation doses, however, the change of static modulus was smaller than that of dynamic one. Those mechanical measurements were compared with the swelling measurements and discussed.
Time‐resolved small‐angle light scattering for the study of phase separation kinetics in bisphenol‐a polycarbonate/poly(methy methacrylate) blends
Authors: Perreault François , Prud'Homme Robert E.
Published: December 2004

An automated, solid‐state small‐angle light scattering apparatus has been constructed for the investigation of polymers; the main features of this system are a bidimensional CCD (charge coupled device) detector with 12‐bit resolution and custom‐made, user‐friendly software for the acquisition and treatment of the scattering data. The miscibility and phase separation kinetics of several bisphenol‐A polycarbonate/poly(methyl methacrylate) blends have been investigated using this apparatus. It was found that the rate of phase separation can be altered significantly by replacing part of the polydisperse poly(methyl methacrylate) (PMMA) in the blends by monodisperse PMMA.
Rheo‐Optical behavior of binary polymer blends: The effect of simple shear flow on phase behavior
Authors: Chen Z. J. , Wu R.‐J. , Shaw M. T. , Weiss R. A. , Fernandez M. L. , Higgins J. S.
Published: December 2004

The phase behavior of polymer blends under simple shear flow has been studied using a custom‐designed rheo‐optical system consisting of a two‐dimensional small‐angle light scattering (SALS) device incorporated into a conventional rheometer. Two‐dimensional SALS images were gathered for model polymer blend systems with different quiescent phase behavior: polystyrene/polyisobutylene (PS/PIB) that exhibits upper critical solution temperature phase behavior and polystyrene/poly(vinyl methyl ether) (PS/PVME) that shows lower critical solution temperature phase behavior. For the PS/PIB blend, shear‐induced phase mixing occurred at a critical shear rate. Below that critical shear rate, the dispersed phase was highly elongated parallel to the flow direction. For PS/PVME blends, a streak scattering pattern was observed even though the sample became optically clear after shearing. We observed, apparently for the first time, the development of a bright‐streak pattern from a transient dark‐streak pattern for a polymer blend system under shear. Rheo‐microscopy studies revealed an intriguing wave pattern that developed coincident with the observation of a streak pattern by SALS. The relationship between the two phenomena has not yet been established.
Milligrams to kilograms: An evaluation of mixers for reactive polymer blending
Authors: Sundararaj Uttandaraman , Macosko Christopher W. , Nakayama Akinari , Inoue Takashi
Published: December 2004

The dispersions of both reactive and nonreactive polymer‐polymer blend systems achieved in three different mixers are compared. The dispersions are prepared using an industrial scale twin‐screw extruder, a laboratory internal mixer, and a miniature cup and rotor mixer. The morphology development in the three mixers is remarkably similar: The dispersed phase is stretched into sheets and ribbons; these sheets and ribbons then break into cylinders, which subsequently break into droplets via Rayleigh‐type instabilities. Drop size distributions can be accurately predicted if we know the size of cylinders formed in the high shear fields of the mixer. There is a significant effect of quenching time on blend morphology—i.e, to properly evaluate mixing, blends must be quenched extremely quickly (well within a minute). Otherwise, we need to consider the morphology development during the quenching time, which may not be relevant to the mixing. There is a uniform shear stress in the miniature mixer, unlike the other mixers, which have varying stress levels. It is shown that a high stress level followed by a lower stress level is required in polymer blending to achieve efficient mixing. In the high stress level, the dispersed phase is stretched into extended shapes, which undergo instabilities and break up upon entering the low stress level. In the miniature mixer, the dispersed phase sees only one stress level, and thus very extended shapes persist at the end of mixing. The final dispersions in the twinscrew extruder and internal mixer at matched maximum shear rates are almost identical. For similar shear rates in the miniature mixer, the final dispersion of reactive blends is comparable to the other mixers. However, the miniature mixer does a poor job in dispersing high viscosity uncompatibilized blends, and the mixing conditions must be altered to obtain efficient mixing.
Morphologies of mechanically mixed amorphous blends before and after annealing
Authors: Andradi L. N. , Hellmann G. P.
Published: December 2004

The morphologies of amorphous polymer blends produced by extrusion were investigated by transmission electron microscopy. Polymers with similar viscosities, i.e. poly(methyl methacrylate) (PMMA), polystyrene (PS), and random copolymers P(SxMMA1 − x) were mixed pairwise, in different compositions. Finely dispersed phase structures were produced in the blends, with domains in the submicron range. The structure patterns were considerably perturbed by the stress fields in the extruder. Domain‐matrix and co‐continuous morphologies were obtained, in a distribution controlled mainly by the viscosity ratio. Annealing after extrusion led to structure coarsening, whereby the patterns were changed until a steady state was established. Sometimes, matrix inversion was observed.
Electrosteric stability of styrene/acrylic acid copolymer latices under emulsion polymerization reaction conditions
Authors: Reynhout Xaviera E. E. , Beckers Mark , Meuldijk Jan , Drinkenburg Bart A. H.
Published: December 2004

Acrylic acid (AA) is used in many emulsion polymerization formulations to improve the colloidal stability during and after the production of latex products. Theoretically, the improved stability originates from electrostatic repulsion complemented with steric repulsion. The objective of this work was to study the contribution of AA to the colloidal stability of polystyrene and styrene/AA copolymer latices under simulated reaction conditions. The strength of electrostatic and steric repulsion forces as a function of the electrolyte concentration, pH, and temperature was investigated via coagulation experiments with monomer‐swollen latices in stirred tank reactors. Transmission electron microscopy pictures and dynamic light scattering measurements provided an understanding of the conditions and mechanisms leading to coagulation. The experiments demonstrated that the presence of surface‐bound carboxylic groups only improved the colloidal stability if the carboxylic groups were charged, that is, at a high pH. At a low pH, the copolymer latices were even less stable than the homopolymer latex, and this indicated that the addition of AA did not improve the colloidal stability of a growing polystyrene latex. With respect to emulsion polymerization process operations, insufficient mixing and a highly concentrated electrolyte feed were found to be sources of fouling and enhanced macroscopic coagulation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 726–732, 2005