bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheological properties of structured fluids
Authors: De Kee D. , Chan Man Fong C. F.
Published: May 2005

The kinetic theory proposed by Soong and Liu for describing the rheological properties of structured fluids has been extended to predict shear‐thinning, shear‐thickening, thixotropy, and antithixotropy in different ranges of shear rates. Viscoelastic properties, as given by the Gordon‐Schowalter Maxwell model, with a non‐constant modulus, have also been considered. The theoretical predictions are compared with the predictions of a model used by Ait‐Kadi, et al. (1988), for a hydrolyzed polyacrylamide solution containing 20 g/1 of NaCl. the predictions and experimental data for the viscosity and primary normal stress coefficient are in reasonably good agreement. The stress growth functions have also been calculated and have been found to be consistent with experimental observations.
Processability and thermal properties of blends of high density polyethylene, poly (ethylene terephthalate), and ethyl vinyl acetate compatibilizer
Authors: Chen C. , Lai F. S.
Published: May 2005

Because of differences in chemical structure and rheological characteristics, high density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) are incompatible when blended during recycling of PET soft drink bottles. To improve the properties of the blends, ethylene vinyl acetate copolymer (EVA) was used as a compatibilizer. Based on torque rheometer tests, the higher the concentration of PET in the blends, the higher the initial loading torque. Blends of 50% HDPE and 50% PET had the lowest equilibrium torque. Equilibrium torque was highest at 5% EVA. The presence of EVA made only a slight difference in the glass transition temperatures of HDPE/PET blends. Higher EVA content in the blend resulted in a lower melting endotherm. Thermogravimetric analysis showed that thermal stability was independent of EVA content; but the more PET in the blend, the lower the final weight loss.
Correlation for volume phase transition of polymeric gel (vinyl alcohol‐sodium acrylate copolymer) in alcohol‐water solutions
Authors: Ishidao Toru , Iwai Yoshio , Hashimoto Yasuhiko , Arai Yasuhiko
Published: May 2005

A thermodynamic model was proposed to correlate the phase behavior of a swelling polymeric gel (vinyl alcohol‐sodium acrylate copolymer) and the volume phase transition in alcohol (methanol, ethanol or propanol)‐water solutions. The model is based on the Flory‐Huggins formula for polymer solution coupled with the osmotic pressure by rubber elasticity proposed by Flory. The volume change behavior and the equilibrium concentrations inside and outside the gel were successfully correlated using the present model.
Heterogeneous suspension polymerization of vinyl chloride: Phase distribution and evolution
Authors: Schmidt M. J. , Farber J. N. , Vallés E. M.
Published: May 2005

A model for the phase distribution and evolution of the heterogeneous (suspension) polymerization of vinyl chloride is presented. Experimental information on pressure, temperature, and conversion has been obtained from a 34 liter bench reactor reproducing reaction conditions and product properties typical of industrial operation. A calculation procedure based on simple plant data is proposed for the description of the phase compositions and their evolution over the entire process. Results based on classical Flory‐Huggins theory of solutions are presented and compared with existing data.
Dielectric properties of blends of polycarbonate and acrylonitrile‐butadiene‐styrene copolymer
Authors: Steeman P. A. M. , Maurer F. H. J. , Van Turnhout J.
Published: May 2005

The low frequency dielectric properties of polymeric blends of polycarbonate (PC) and acrylonitrile‐butadiene‐styrene (ABS) were studied in the temperature interval of 100 to 170°C. Attention was focused on a 60/40 (m/m) PC/ABS blend. The results were compared with dynamic mechanical measurements in torsion and with the results of a morphological investigation using scanning electron microscopy (SEM). Besides the relaxations at the glass transition temperatures of the components an additional strong low frequency dielectric dispersion was observed, which was not found in mechanical measurements. This low frequency polarization process is due to interfacial polarization at the boundaries between conductive ABS and non‐conductive or slightly‐conductive PC. It is shown how this process can be described by the dielectric models for two‐phase heterogeneous materials. The Looyenga model offers the best description of the detected effects, while the Hanai model is less suitable. The shape factor of the ABS phase as used for modeling the dielectric properties agrees well with the observed morphology using SEM. It is shown for the dielectric measurements on the 75/25, 60/40, and 45/55 (m/m) PC/ABS blends how the connectivity of the ABS phase can be sensitively derived from the eletrical conductivity of the blend, whereas mechanical measurements are highly senstive to the connectivity of the PC phase.
In‐situ cure monitoring of diamine cured epoxy by fiberoptic fluorimetry using extrinsic reactive fluorophore
Authors: Dang Wenbin , Sung Nak‐Ho
Published: May 2005

This paper describes the application of a molecular sensor for in‐situ monitoring of epoxy‐diamine cure via remote sensing fiberoptic probes. A custom‐built, fiberoptic fluorimeter allows on‐line recording of fluorescence spectra directly from the cure environment. Cure reactions in epoxy‐diamine network, such as diglycidyl ether of bisphenol A‐diaminodiphenyl sulfone (DGEBA‐DDS) or diglycidyl ether of butanediol‐diaminodiphenyl sulfone (DGEB‐DDS), have been monitored by a reactive molecular sensor, diamino azobenzene (DAA). DAA exhibits sensitive changes in UV‐visible and fluorescence spectra due to the conversion of its primary amine groups to secondary and tertiary amine groups. Fluorescence intensities are correlated with extent of reaction in epoxy network and processing parameters, such as cure temperatures and time. The use of an internal reference dye for normalization of fluorescence intensities is necessary for the quantitative correlation of spectral signals with the network structure. Variables affecting the fluorescence intensity such as excitation volume, probe location, excitation intensity fluctuation, temperature, and background intensities from optical fiber can be calibrated by normalizing the signal intensities against the internal reference. Sulforhodamine 101 was found to be a satisfactory reference dye which provides stable, readable signals over temperatures up to 200°C.
Kinetic parameters estimation for cure reaction of epoxy based vinyl ester resin
Authors: Lee Jhong Ho , Lee Jae Wook
Published: May 2005

A new graphical estimation technique is proposed for the determination of the kinetic parameters describing an autocatalytic reaction. A differential scanning calorimeter was used to monitor the reaction kinetics of an epoxy‐based vinyl ester resin. The method utilizes information from a zero initial reaction rate, conversation at vitrification, the ratio of reaction rate constants under different isothermal conditions, and characteristics of the phenomenological kinetic model with assumptions being made about the overall reaction order. By fitting data to the integrated reaction rate equation with adjustments for the isothermal conditions, the kinetic parameters are estimated without using a linear or nonlinear regression method. Different kinetic parameters can be estimated from data before and after the gel point which was obtained from the relationship between the glass transition temperature and the degree of cure.
Mechanical properties and morphology of liquid crystalline copolyester‐amide and amorphous polyamide blends
Authors: Jang Sang Hee , Kim Bong Shik
Published: May 2005

Blends of an amorphous polyamide (PA) and a liquid crystalline copolyesteramide (LCP), poly(naphthoate‐aminophenoterephthalate) were prepared in a twin‐screw extruder. Specimens for mechanical testing were prepared by injection molding. Morphological, thermal, mechanical, and rheological properties were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X‐ray diffractometry, capillary rheometry, and a tensile tester, respectively. The tensile mechanical behavior of the LCP/PA blends was found to be affected by their compositions and specimen thickness. Tensile testing revealed that the tensile mechanical behavior of the LCP/PA blends was very similar to that of polymeric composite and the tensile strength of the LCP/PA (50/50) blend was approximately two times of the value of PA homopolymer and exceeded that of pure LCP. The morphology of the LCP/PA blends was also found to be affected by their compositions. SEM studies revealed that the liquid crystalline polymer (LCP) formed finely dispersed spherical domains in the PA matrix and the inclusions were deformed into fibrils from the spherical droplets with increasing LCP content. It has been found that droplet and fiber formations lead to low and high strength material, respectively. In particular, at specific LCP content (50 wt%), the tensile strength of the LCP/PA blend exceeded that of pure LCP. The improvement in tensile properties is likely due to the reinforcement of the PA matrix by the fibrous LCP phase as observed by SEM. A distinct shell‐core morphology was found to develop in the injection molded samples of these blends. This is believed to have a synergistic effect on the tensile properties of the LCP/PA blends. The rheological behavior of the LCP/PA blends was found to be very different from that of the parent polymers and significant viscosity reductions were observed for the LCP/PA (50/50) blend. Based upon DSC, these blends have shown to be incompatible in the entire range of concentrations.
Air drag on fine filaments at oblique and normal angles to the air stream
Authors: Ju Y. D. , Shambaugh Robert L.
Published: May 2005

Measurements are reported for air drag on fine filaments whose axes are oriented at oblique and normal angles to the air velocity. In terms of the drag coefficient CDN the data are fit well by the following relation: CDN = 6.96(ReDN)−0.440(d/d0)0.404, where ReDN is the Reynolds number based on flow normal to the fiber axis, and d/d0 is a dimensionless fiber diameter. A wide range of conditions were tested: filament diameters ranged from 13 to 390 microns, gas velocities ranged from 22 to 83 m/s, and fiber Reynolds numbers ranged from 29 to 2120.
Numerical nonisothermal flow analysis of non‐Newtonian fluid in a nonintermeshing counter‐rotating twin screw extruder
Authors: Fukuoka Takamasa , Min Kyonsuku
Published: May 2005

A simulation technique for nonisothermal flow analysis of non‐Newtonian fluid in a nonintermeshing counter‐rotating twin screw extruder was developed by modifying the flow analysis network (FAN) method. The local shear viscosity in the flow field was calculated by an iteration method combing the three types of mean shear rate functions. The modified Cross model and an Arrhenius‐type function for temperature dependence were also introduced. Streamlines in the flow field are represented by computing the movements of fluid particles based on the flux fields. The computed residence time from the streamlines led us to solve the energy equation by replacing the coordinate system. The profiles of pressure, shear rate, shear viscosity, temperature, and residence time were simulated. The influence of operating and geometrical parameters on the screw characteristics are discussed. Further, residence time distribution (RTD), strain distribution function (SDF), and interfacial area growth are predicted from the computation of streamlines to analyze the mixing capabilities of the extruder.
Extrudate roughness of high‐density polyethylene and linear low‐density polyethylene: Determination of key parameters using screening design
Authors: Wang X. , Clément B. , Carreau P. J. , Lafleur P. G.
Published: May 2005

A screening design is used to establish the contribution of various parameters to the roughness of cylindrical extrudates. A dimensionless response variable is proposed to characterize the extrudate roughness, and the effects of ten parameters on this roughness response were examined. Two polyethylenes (one high density and one linear low density) were investigated using a 45 mm single screw extruder. The results show that the main parameters affecting the extrudate roughness are, in order of importance, apparent shear stress at the die wall, die diameter, ratio of die length to diameter, and type of polymer. The other six parameters (the use of an additive, recycling, type of entrance adapter, die material, die temperature, melt temperature) were found to have a non‐significant contribution to roughness.
Rheological properties of blends of lithium‐ or sodium‐sulfonated polystyrene ionomers with polyamide 6
Authors: Yoshikawa K. , Molnár A. , Eisenberg A.
Published: May 2005

Dynamic viscoelastic properties of blends of alkali metal salts of sulfonated polystyrene ionomers with polyamide 6 were investigated in the melt. The blends of lithium‐sulfonated polystyrene (10 mol% sulfonation) with polyamide 6 (LiSPS/PA‐6) behaved as a homogeneous viscoelastic fluid over most of the blend composition range, since blending with PA‐6 disrupted the ionic network of the LiSPS. Specific interactions between the lithium sulfonate group and the amide group are believed to be responsible for the behavior. By contrast, blends of sodium‐sulfonated polystyrene with PA‐6 (NaSPS/PA‐6) showed typical behavior of immiscible systems in that they exhibited large positive deviations from the log‐additivity rule for complex viscosity. This implied that sodium sulfonate groups did not interact strongly with amide groups, in contrast to the behavior of lithium sulfonates. Oldroyd's emulsion model was applied to the results of dynamic viscoelasticity studies of both the immiscible ionomer/PA‐6 blends and the polystyrene/PA‐6 blends. For the latter, the fit was much better than for the former. This difference in behavior might be due to partial miscibility or to the presence of an indistinct phase boundary in the “immiscible” ionomer‐based systems.
Electrical resistivity behavior of mold‐cast metal‐filled polymer composites
Authors: Yang Lei , Schruben Dale L.
Published: May 2005

Mold‐cast, metal‐filled composites made of poly(methyl methacrylate) and aluminum or nickel exhibited electrical resistance qualitative behavior as predicted by the percolation and tunneling mechanisms. A precipitous change in resistivity of about 104 ohm‐cm was found at volume concentrations of filler in the range of 18.5 to 19.8 vol%. Details of the electrode system are given for making these measurements. Using different polymers does not change the resistance behaviour of the composite to any great degree, suggesting that particle features of shape, size, arrangement, and so forth are the more important parameters. Such particle morphological details are indicated in the included photomicrographs.
Extension of effective medium theory to three‐component system—two conductive particle types in the polymer matrix
Authors: Trivedi A. H. , Garcia J. , Burhan A. B. , Schruben D. L.
Published: May 2005

A foundation is presented for the extension of the normal effective medium theory (for a two‐component system (filler and polymer matrix)) to a three‐component system (two filler species and matrix). No experimental test of the improved theory is made here, but some general trends are confirmed by other experiments. The theory is sufficiently general to allow the second filler component to represent a particle of the same composition as the first filler component but of a different size, or of the same size but of a different composition. Important satellite derivations are included.
Shrinkage modeling of polyester shrink film
Authors: Shih Wayne K.
Published: May 2005

A model was developed to quantify the thermal shrinkage behavior of polyester shrink film under isothermal and nonisothermal conditions. This model employs the straightforward first order reaction kinetics to an otherwise microscopically complex relaxation process. It offers three unique parameters for quality control and material specification of shrink film. In the isothermal condition, the induction time, the shrink constant, and the ultimate shrinkage are the three parameters used by the model to quantify the shrinkage of shrink film under an elevated but constant temperature. In the nonisothermal condition, the shrink film is heated using a constant heating rate. Three parameters, which are the onset shrink temperature, the shrink constant, and the ultimate shrinkage, characterize the shrinkage of shrink film. The model fits the experimental data very well. The thermal shrinkage of several polyester homopolymers, copolymers, and polyester blends was investigated and compared to that of poly(vinly chloride) (PVC) shrink film. Two polyester blends containing glycol modified poly(ethylene terephthalate) (PETG) copolyester behave similar to PVC in shrinkage behavior. The effect of stretch temperature, stretch ratio, and stretch rate on the shrinkage characteristics of oriented PETG film was also studied. The stretch temperature has the highest influence on the shrinkage behavior of oriented film.
Polymer blends of polyethersulfone with all aromatic liquid crystalline co‐polyester
Authors: Yazaki Fumihiko , Kohara Atsushi , Yosomiya Ryutoku
Published: May 2005

Polymer blends of polyethersulfone (PES) with an all aromatic liquid crystalline co‐polyester (LCP) were investigated. In addition, PES oligomers with the reactive functions end groups (−ONa) were added as a third component to the above blends in order to improve their properties. Flexural properties, such as modulus and strength, and dynamic viscoelastic properties, such as dynamic storage elasticity (E′) and loss tangent (tan δ), of the blends were measured. The morphology of blends was characterized using a differential scanning calorimeter (DSC) and a scanning electron microscope (SEM). Of the flexural properties, the modulus of PES increased almost linearly with increasing LCP content. However, strength decreased as LCP content increased to 20 wt%. In contrast, the addition of the PES oligomers had little effect on modulus, but strength was clearly improved. Regarding dynamic viscoelastic properties, the oligomer‐containing blends exhibited complex behavior. Regarding morphologies, SEM analysis revealed that the LCP was not fibrous in the core of the blend containing 40 wt% or less, but the addition of the PES oligomers made LCP fibrous even in blends with low LCP content. It was concluded that the PES oligomers with reactive functional groups acted as a compatibilizer in polymer blends of PES/LCP.
Generation of microcellular polymeric foams using supercritical carbon dioxide. II: Cell growth and skin formation
Authors: Goel Satish K. , Beckman Eric J.
Published: May 2005

We have generated microcellular polymeric foam structures using a pressure induced phase separation in concentrated mixtures of supercritical CO2 and poly(methyl methacrylate). The process typically generates a microcellular core structure encased by a nonporous skin, the thickness of which decreases with increasing saturation pressure. This trend can be described by a model for skin formation that is based on the diffusion rate of gas out of the sample. Significant density reductions on the order of 30 to 70% can be achieved by changing the pressure and temperature conditions in the foaming process. There are several ways in which the saturation pressure affects the average cell size, with the net effect that cell size decreases sharply with increasing pressure above 2000 psi, leveling out at higher pressures. Cell size increases with increasing temperature from 40°C to 70°C. A model for cell growth, based on a cell model of Aremanesh and Advani, modified to include the effect of CO2 on model parameters, reproduces these trends.
Experimental study of transcription of minute width grooves in injection molding
Authors: Yoshii Masaki , Kuramoto Hiroki , Kato Kazunori
Published: May 2005

In injection molding of substrates for optical discs, precise transcription of pits and grooves is very important. For high‐density optical discs, molding transcription for minute grooves with widths on the sub‐micron level is required. In this paper, in order to clarify the relationship between molding conditions and transcription quantitatively, transcription of minute rectangular grooves (width 0.55 μm, depth 70 nm) in injection molding of polycarbonate resin was studied. The relationship between molding conditions and the transcription heights was verified. And, by introducing the equivalent thickness of the vitrified layer concept, a transcription model related to the minute groove width is proposed. This equivalent thickness of the vitrified layer is estimated to be 100 to 150 nm at the point of filling completion under a certain molding condition. Also, using the above description of the equivalent thickness of the vitrified layer, it is possible to estimate the extent of transcription under the various molding conditions.
Reaction‐induced phase separation during the formation of a polyurethane‐unsaturated polyester interpenetrating polymer network
Authors: Chou Y. C. , Lee L. J.
Published: May 2005

In this study, an interpenetrating polymer network (IPN) based on a polyurethane (PU) and a partially end‐capped unsaturated polyester (UPE) was prepared. The reaction‐induced phase separation process of the IPN was studied using a phase contrast optical microscope and a transmission electron microscope (TEM), while reaction kinetics and onset of gelation were determined by a differential scanning calorimeter and a rheometer respectively. Except at low temperatures, the phase separation patterns were found to follow the spinodal decomposition mechanism. An interconnected phase developed quickly and was followed by coalescence of the periodic phase to form droplet/matrix type of morphology. A second level of phase separation also occurred within both the droplet and the matrix phases in some cases. The domain sizes resulting from both levels of phase separation gradually increased until the structure was locked by chemical gelation. Reaction temperature, PU reaction rate, and UPE reaction rate all had significant effects on the final morphology of the formed IPNs.
The compatibility of linear low density polyethylene‐polypropylene blends: Viscosity ratio plots
Authors: Bains M. , Balke S. T. , Reck D. , Horn J.
Published: May 2005

Blends of linear low density polyethylene (LLDPE) and polypropylene (PP) show diverse mechanical property behavior in the published literature. The main objectives of this work were: to investigate the effect of viscosity of the component phases on the mechanical properties of such blends and to use the results to obtain a method for compatibilizing diaper manufacturing waste. The significant result of the study was that although LLDPE/PP blends are often termed “incompatible,” when viscosity of the components was more closely matched to each other, increases of as much as 50% in tensile strength and modulus were observed over the “rule of mixtures” line. Also, scanning electron microscopy then showed a more diffuse interface between the component phases. Three dimensional views of plots of viscosity ratio of the blend components as a function of temperature and shear rate were used to demonstrate the closer matching of viscosities for the blend components of the higher performing blends. In processing diaper manufacturing waste, addition of a high molecular weight PP in a manufacturing scale single screw extruder, to provide a closer match of viscosities of the blend components, significantly improved mechanical properties.
Zone drawn NEW‐TPI thermoplastic polyimide and its blends with Xydar liquid crystalline polymer
Authors: Aihara Yoshihiko , Cebe Peggy
Published: May 2005

In this work we report the effects of single stage zone drawing on the properties of NEW‐TPI thermoplastic polyimide homopolymer, and its blends with Amoco's Xydar liquid crystalline polymer. Zone drawing was performed first on homopolymer NEW‐TPI films to determine the effect of load weight, heater speed, and drawing temperature on the attainable draw ratio. Degree of crystallinity and chain orientation increase as the draw ratio increases for NEW‐TPI. Blends of NEW‐TPI/Xydar compositions 90/10 and 70/30 were studied next. In blends, the Xydar component is not molecularly dispersed, and is initially preferentially oriented along the machine direction during the film processing stage. Xydar acts as a nucleation site and lowers the temperature for crystallization of the NEW‐TPI from the rubbery amorphous state. Zone drawing was performed either parallel or perpendicular to Xydar's initial preferred orientation direction. Blends with lower Xydar fraction could be zone‐drawn to higher ratios. Zone drawing perpendicular to Xydar's initial orientation direction also resulted in increased draw ratio. Dynamic mechanical properties of the zone drawn materials were studied. In homopolymer NEW‐TPI, dynamic modulus increased by a factor of two to 4.0 GPa in zone drawn films, largely as a result of the formation of oriented crystallites. In the blends, the modulus parallel to Xydar's initial orientation direction was greater than that in the transverse direction. Depending upon composition and test direction, zone drawing increased the dynamic moduli of the blends from 1.5 up to 2.7 times, in the temperature range from 150°C to 300°C.
Processing/morphology correlations in poly(benzoate‐co‐naphthoate) liquid crystalline polymers
Authors: Hudson Steven D. , Lovinger Andrew J. , Venkataraman Sundar K. , Liu Chester , Manzione Louis T.
Published: May 2005

The molecular orientation and disclination defects in injection molded bulk samples of liquid crystal polymers have been revealed by transmission electron microscopy (TEM). Using a recently optimized lamellar decoration and etch technique for use with poly(benzoate‐co‐naphthoate), we have studied in detail the skin‐core morphology produced by realistic injection molding processing. In the skin, the director is observed to be highly aligned along the flow direction, and the defect density is very low (10 cm−2). In the core, however, the defect density is six orders of magnitude greater, and the director lies predominantly in the plane defined by the flow and neutral directions. The flow during processing is turbulent, giving rise to distinct morphological features and disclination clusters. When the material is filled at 20% volume fraction with long glass fibers, the molecular and filler orientations are nearly parallel. Dimensional precision also correlates with the morphology and improves with increasing core fraction.
Degradation of unstabilized medium‐density polyethylene pipes in hot‐water applications
Authors: Viebke J. , Elble E. , Ifwarson M. , Gedde U. W.
Published: May 2005

Pipes of an unstabilized medium‐density polyethylene have been pressure tested with internal stagnant water and moderately circulating air as the external medium at temperatures ranging from 70 to 105°C and changes in molecular structure and crystallinity have been studied. The stage III (fracture induced by thermal oxidation) life of the unstabilized polyethylene pipes was less than 12% of the life of the corresponding stabilized polyethylene pipes. Infrared spectroscopy and size exclusion chromatography showed an earlier and more extensive increase in the quantities of oxidation end‐products and a more pronounced decrease in molar mass of the outer‐wall‐material than of the inner‐wall‐material of the pipe. Mass crystallinity, measured by differential scanning calorimetry, increased on an average by a quantity corresponding to 45 methylene groups per chain scission event. The life of the unstabilized pipe was divided into an induction period during which no detectable thermal oxidation occurred and a subsequent polymer degradation period. The induction period exhibited an Arrhenius‐temperature‐dependence with an activation energy of 75 kJ mol−1.
Three‐dimensional modeling of reaction injection molding. I
Authors: Lo Yu‐Wen , Reible Danny D. , Collier John R. , Chen Cheng‐Ho
Published: May 2005

In this research a model to simulate both the filling the curing stages of a reaction injection molding (RIM) process in complex three‐dimensional molds is developed. This model can be used to predict not only the temperature and conversion changes with time but also the front position during filling. Using given physical and chemical properties of the RIM system, moldability can be determined in advance. The numerical techniques used in this research include adaptation of the SIMPLE algorithm developed by Patankar for a moving‐front, two‐phase system with non‐negligible inertial effects, and exothermic chemical reaction. The model predictions of temperature and conversion compare favorably with available data on simple two‐dimensional molds. The ability of the model to predict the dynamics of filling in more complicated molds was verified by comparison to mold filling experiments with water and a polyurethane foam.
Investigation of processing‐structure‐properties relationships in polyethylene blown films
Authors: Patel Rajen M. , Butler Thomas I. , Walton Kim L. , Knight G. W.
Published: May 2005

Molecular orientation imparted during film fabrication is known to have a major effect on mechanical and thermal properties of both glassy and semicrystalline polymers. A three‐variable Box‐Behnken designed experiment was used to study the effects of die gap, die land length, and blowup ratio (BUR) on key linear low density polyethylene (LLDPE) blown film properties at constant final film thickness. In addition, differences in molecular orientation in the films were studied using optical birefringence and shrinkage methods. Measured key film properties were correlated to processing conditions and to measured molecular orientation. Die land length had no significant effect on film structure and properties. All LLDPE films exhibited about 70 to 80% shrinkage in the machine direction (MD) but expanded in the cross direction (CD). Most films exhibited negative in‐plane birefringence. MD Elmendorf tear was found to be inversely related to drawdown ratio and MD shrinkage, suggesting that MD tear is dependent primarily on amorphous chain extension and hence, amorphous segments orientation for LLDPE blown films. Dart impact strength of the films was shown to be related to MD shrinkage and to the induced surface roughness due to varying die gap. In a separate study, blown films of three high pressure LDPEs were fabricated under nearly identical conditions. No correlation was found between birefringence and shrinkage data on the LDPE blown films.
On the pressure dependency of the viscosity of molten polymers
Authors: Kadijk S. E. , Van Den Brule B. H. A. A.
Published: May 2005

A slit viscometer to measure the viscosity of polymer melts under processing conditions is described. Along the slit a pressure drop is generated by applying a pressure at both the entrance and the exit. In this way the pressure in the center can be controlled independently of the shear rate. The pressure gradient in the slit is measured by means of three pressure transducers which are mounted in the region of fully developed flow. Results of pressure‐dependent viscosity measurements on polystyrene, polyacrylonitrile‐butadiene‐styrene, and polypropylene are presented in a shear rate range of five decades. The flow curves obtained at different pressures and temperatures can be shifted onto a master curve. The shear thinning behavior of the three materials is adequately described with the generalized Cross‐Carreau equation, while the zero shear viscosity is modeled with a generalized Arrhenius‐W.L.F. relationship, incorporating a pressure dependency. Alternatively, it is possible to describe the zero shear viscosity in terms of the free volume fraction and the temperature.
Laser welding of polymers
Authors: Nonhof C. J.
Published: May 2005

Deep penetration welding and cutting of metals can be carried out at high speed with relatively low laser power. The efficient coupling of the laser radiation to the metal is due to the formation of a “keyhole.” Over the years, an attempt has been made to transfer the results on metals to plastics. It will be shown here that keyhole welding of plastics is limited to the very restricted set of plastics that have a boiling point. Volume heating, a mechanism that is not applicable to metals, is restricted to plastics with a good transparency for the incident radiation and with a high optical quality. Finally, surface heating is shown to be the most common mechanism for heating plastics.
Enhancement of electrical conductivity of uniaxially and biaxially processed poly(p‐phenylene sulfide) films
Authors: Ko Dong‐Hwi , Min Kyonsuku
Published: May 2005

A fundamental study of electrical conductivity of uniaxially and biaxially stretched poly‐p‐phenylene sulfide (PPS) film was conducted. In this paper, we paid special attention to understand the effect of processing conditions on the electrical conductivity as well as the conduction mechanism of tantalum pentafluoride (TaF5) doped PPS. The electrical conductivity of PPS film was measured by a four‐point probe method in the parallel and perpendicular directions to the stretching direction. The infrared spectra of doped and undoped stretched PPS films demonstrate that the TaF5 doping causes distortion (polaron) in PPS chain and conduction. A similar discussion was reported by Tsukamoto, et al. (1, 2). They found the delocalization of π‐electrons in doped PPS by X‐ray spectoscopy (XPS), infrared spectroscopy (IR), and C13‐NMR. The conductivity of doped PPS films increased with increasing stretching ratio. The crystallinity effect on the electrical conductivity was investigated by changing crystallinity of PPS films in terms of annealing and multi‐axially stretching. Orientation development was investigated by wide angle X‐ray scattering and birefringence techniques. The relationship between conductivity and orientation of stretched PPS films was investigated by introducing electrical anisotropy.
Kinetic studies and process analysis of the reactive compatibilization of nylon 6/polypropylene blends
Authors: Dagli S. S. , Xanthos M. , Biesenberger J. A.
Published: May 2005

This article describes a study on the reactive compatibilization of nylon 6 (N6) and polypropylene (PP) blends through a functionalized PP. A graft copolymer was formed in‐situ by reacting an acid modified PP with N6 during blend compounding. The compatibilization reactions are studied in detail. Kinetics were estimated by means of experiments in a batch mixer. Three time constants were estimated, corresponding to (a) reactions, (b) melting of polymers, and (c) melt mixing. The effects of temperature and rotor speed on the reaction kinetics were also measured. There was a substantial increase in initial reaction rate, as the rotor speed was increased. Increasing the temperature did not significantly affect the reaction rate. Process parameters important for such a reactive compatibilization process were identified by statistically designed experiments in a co‐roatating intermeshing twin‐screw extruder. Screw speed, presence of venting, and sequence of feeding were shown to have a noticeable effect on the reactive compatibilization process during continuous compounding.
High modulus polypropylene: Effect of polymer and processing variables on morphology and properties
Authors: Phillips R. , Herbert G. , News J. , Wolkowicz M.
Published: May 2005

The morphology and properties of high modulus polypropylenes (PP) are characterized over a wide range of material variables. These variables include the tacticity, room temperature xylene solubles (XSRT), molecular weight, melt flow rate (MFR), and polydispersity index (PI). Flexural modulus in quench‐cooled compression moldings of propylene homopolymer can be correlated to the volume fraction crystallinity, ϕc, by an empirical logarithmic dependence. The quantitative zero orientation results for the quench‐cooled compression moldings provide an approximate crystallinity normalization for oriented moldings. WAXS analyses of crystalline orientation were determined over a range of melt temperatures and mold locations and correlated to the skin area fraction by optical microscopy. WAXS analysis of the balance of orientations for the crystallographic axes suggest that the orientation balance is primarily determined by the “melt orientability” of the resin type. An empirical description of flexural modulus in injection molded PP is developed for the range of material variables and molding conditions studied. This description is represented as a function of crystallinity‐normalized modulus vs. the frozen‐in crystalline orientation.
Reactive extrusion of acrylic acid grafted polypropylene with hexadecylamine
Authors: Wang X. C. , Tzoganakis C. , Rempel G. L.
Published: May 2005

To study the possibility of the production of branched polypropylene (PP) by a reactive extrusion (REX) route, side chains were introduced on the backbone of a polypropylene material by reacting hexadecylamine with acrylic acid grafted PP. Experiments were carried out both in solution and in the melt, and the products were analyzed by FTIR, elemental analysis, dynamic mechanical, and rheological techniques. Analysis of the FTIR spectra of the samples produced in the solution reactions, at an equal molar ratio of [ –NH2]/[–COOH] without catalyst addition and without removal of the by‐product, revealed that the formation of imide was increased with increasing the reaction time up to 10 h, while a further increase in reaction time resulted in a reversal of the reaction. In the REX experiments, FTIR analysis showed that the imide formation increased with the [–NH2]/[–COOH] molar ratio. At a molar ratio of one, more imide was present in the REX product than the in‐solution one. Elemental analysis suggested that the nitrogen content in the products initially increased with [–NH2]/[–COOH] molar ratio and then reached an almost constant value at molar ratio values of about unity. The glass transition temperature (Tg) was measured by dynamic mechanical analysis (DMA), and it was found that the attachment of the alkyl chains caused a reduction in Tg of the products. Finally, rheological measurements showed that the shear viscosity of the products increased with the amine/carboxyl molar ratio at low shear rates and that their moduli were enhanced as a result of the attachment of the alkyl side chains.
Interfacial tension in polymer melts. Part II: Effects of temperature and molecular weight on interfacial tension
Authors: Kamal M. R. , Lai‐Fook R. , Demarquette N. R.
Published: May 2005

Interfacial tension is one of the most important parameters that govern the morphology of polymer blends and the quality of adhesion between polymers. However, few data are available on interfacial tension due to experimental difficulties. A pendant drop apparatus was used for the determination of the interfacial tension for the polymer pair polypropylene/polystyrene (PP/PS). The effects of temperature and molecular weight were evaluated. The range of temperatures used was from 178° to 250°C, and the range of molecular weights used was from 1590 to 400,000. The interfacial tension decreased linearly with increasing temperature. With only one exception, higher molecular weight systems showed weaker dependence of interfacial tension on temperature than lower molecular weight systems. Also, polydisperse systems showed a stronger dependency on temperature than the monodisperse systems. The value of the interfacial tension, which increases with molecular weight, appears to level off at molecular weights above the entanglement chain length. For the polymer pair PP/PS, the dependency of the interfacial tension on the number average molecular weight appears to follow the well‐known semi‐empirical (−2/3) power rule over most of the range of molecular weights. Comparable correlations were obtained with values of the power between −1/2 and −1.0.
Numerical simulation of the fountain flow problem for viscoelastic fluids
Authors: Sato Toru , Richardson Stephen M.
Published: May 2005

Fountain flow for isothermal viscoelastic fluids is simulated by a numerical method based on a combination of a finite element method and a finite volume method. For the treatment of moving free surfaces, a fringe element generation method is used. Circulating flow and elongation in the transverse direction at the melt front are simulated well. Numerical results also suggest that circulation in fountain flow and viscoelastic retardation may give rise to symmetric V‐shaped patterns of birefringence between the center‐plane and wall. Such information on molecular orientation in fountain flow is important for physical properties of thick molded products.
Thermal studies of blends of poly(phenylene sulfide) (PPS) with poly(phenylene sulfide sulfone) (PPSS) and with poly(phenylene sulfide ether) (PPSE)
Authors: Brostow Witold , Seo Kwan‐Ho , Beak Jong B. , Lim Jeong C. , Seo Kwan‐Ho
Published: May 2005

The miscibilities of poly(phenylene) sulfide/poly(phenylene sulfide sulfone) (PPS/PPSS) and poly(phenylene) sulfide/poly(phenylene sulfide ether) (PPS/PPSE) blends were invesigated in terms of shifts of glass transition temperatures Tg of pure PPS, PPSS, a dn PPSE. The crystallization kinetics of PPS/PPSS blends was also studied as a function of molar composition. The PPS/PPSS and PPS/PPSE blends are respectively partially and fully miscible. PPSE shows a plasticizing effect on PPS as does PPS on PPSS, which necessarily improves te processibility in the respective systems. We can control Tg and melting temperature Tm of PPS by varying amounts of PPSE in blends. The melt crystallization temperature Tmc of PPS/PPSE blends was higher than that of the PPSE homopolymer. Therefore, these blends require shorter cycle times in processing than pure PPSE.

The overall rate of crystallization for PPS/PPSS blends follows the Avrami equation with an exponent ≃2. The maximal rate of crystallization for PPS/PPSS blends occurs at a temperatre higher by 10°C than that for PPS, while the crystallization half time t1/2 is 4 times shorter. In the cold crystallization range, crystal growth rates increase and Avrami exponents decrease significantly as the temperature increases.
Reinforcement of mechanical properties of a poly(ethylene terephthalate) and polycarbonate blend by the addition of thermotropic liquid crystalline polymer
Authors: Kwon Soon Kil , Chung In Jae
Published: May 2005

Mechanical properties of the ternary blends of poly(ethylene terephthalate) (PET), polycarbonate (PC), and thermotropic liquid crystalline (TCLP, Vectra A950) were investigated. The ternary blends were prepared by varying the amount TLCP but fixing the ration of PET and PC. The fiber fallen freely through the capillary die had the highest initial modulus (1.46 GPa)/tensile strength (73 MPa) when 10% of TLCP was added. Above this TLCP content, however initial modulus and tensile strength decreased. The scanning electron microscope (SEM) micrographs of the TLCP phase which was extracted by dissolving PET/PC matrix from the blend showed the fine fibrils formed at 5 and 10% of TLCP, while the aggregated TLCP phases at 20 and 30% of TLCP. It was suggested that the decrease of the mechanical properties of the resulting blend was caused by the aggregation of TLCP phase above 10% of TLCP. A high draw ratio gave a rise to the formation of highly oriented fibrils of TLCP phase in the PET/PC matrix and the improvement of mechanical properties of the ternary blend.
Aging characteristics of oriented ply(ethylene terephthalate)
Authors: Mukherjee Sumit , Jabarin Saleh A.
Published: May 2005

The physical aging characteristics of oriented poly(ethylene terephthalate) (PET), have been studied ad functions of storage time and temperature below the glass transition temperature (Tg) of PET. The free volume relaxation, associated with aging, has been characterized by the enthalpy at Tg, as measured by differential scanning calorimetry. The effects of the free volume relaxation on mechanical properties and the mode of failure have been investigated. It has been determined that a correlation exists between the enthalpy of relaxation and the ductile‐to‐brittle failure transition. Molecular orientation reduces significantly the enthalpy of relaxation, resulting in the disappearance of the ductile‐to‐brittle transition when highly oriented samples are aged over time. It has been established that a minimum amount of orientation is required to reduce or eliminate the effects of PET aging. Molecular orientation has also been found to reduce craze formation when oriented PET is exposed to a stress‐cracking medium at constant stress.
Esterification in reactive extrusion
Authors: Maier C. , Lambla M.
Published: May 2005

A condensation type reaction has been studied for reactive extrusion in a twin‐screw extruder. The esterification reaction is to graft a nonylphenyl‐ethoxylate (NP8) onto a pre‐maleated ethylene‐propylene (EPRMA). The kinetics were initially characterized in the static mixture using a thermally controlled call in a FTIR spectrometer. These were then used to predict the conversion along the length of the extruder screws, having determined the residence time distribution at various sampling locations. A reasonable fit with the data was obtained, although the kinetics seem to be slightly faster in the flowing medium than those predicted. Over short screw distances, the equilibrium rapidly approached equilibrium. Moreover, the NP8 was shown to penetrate the EPRMA within screw distance of less than 1.3 L/D, despite using conveying elements known for their minimal mixing capacity. Within the molten medium, a mixing model showed that obtaining the expected conversion in a product does not imply that the reactants in the product have in fact been well mixed.
Species distribution during the cure of dicyanate ester
Authors: Owusu A. Osei , Martin G. C.
Published: May 2005

The network formation process for bisphenol A‐based cyanate ester resin was examined using size exclusion chromatography (SEC) and differential scanning calorimetry (DSC). A kinetic scheme based on the SEC data was used to predict the species distribution in the reaction medium in the pregel region. After gelation, the molecular species undergo retroversion as the high molecular species are predominantly attached to the growing network structure.
The use of sodium salts as nucleation agents for polyethylene terephthalate with minimal molecular weight reduction
Authors: Gilmer J. W. , Neu R. P. , Liu Y. J. , Jen Alex K.‐Y.
Published: May 2005

The sodium salts of carboxylic acids and other weak acids are routinely used as nucleation agents for injection moldable poly(ethylene terephthalate) (PET) resins. One of the primary drawbacks accompanying their use is the degradation of the PET resulting from the attack of the ester by the sodium carboxylate. Several sodium carboxylates have been found based on pyrrole carboxylic acid that are effective as nucleants but which do not cause a reduction in the molecular weight of PET. In addition, tetraphenyl borate salts, although only marginally effective as nucleants, were observed to be efficient additives to PET for counteracting molecular weight loss caused by chemical nucleants.