bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slit flow of molten polyethylene filled with plastic flakes
Authors: Suto Shinichi , Fujimura Toshikazu 
Published: December 2004

AbstractThe processability of polyethylene in sheet‐extrusion or calendering may be improved by the addition of plastic flakes. The effects of plastic flake parameters and flow conditions on the viscosity and the die swell of the suspension were determined, and the structure in flow (morphology or dispersion state) and applications were discussed. Flakes of biaxially oriented polystyrene, high‐impact polystyrene, polypropylene, polyamide or polypropylene spheres were dry‐blended with polyethylene. The viscosity was determined by means of a slit or a capillary rheometer. The quenched extrudate was annealed and its die swell was measured. Flakes of biaxially oriented polystyrene shrunk into rod‐like form during heating, but other plastics retained the flake‐form. The relative viscosity and the swell ratio of the suspensions depended on the type of plastic and operating conditions. The rheological behavior of suspensions qualitatively suggested that polypropylene flakes deformed or crowded (including stacking), polyamide flakes deformed slightly, and polystyrene flakes were difficult to buckle, but crowded slightly. The thickness of extrudates can be controlled easily by flake addition due to decreased die swell, while the output would be reduced to some extent.
Optimization of fiber drawing processes in terms of the filament state variables
Authors: Butler R. H. , Prevorsek D. C. , Kwon Y. D. 
Published: December 2004

AbstractA new method of optimizing the fiber drawing process involving the feed roll, the heated elements and the take‐up roll is presented. In this method, the process is described in terms of the filament temperature and filament extension in the drawing zone. This is in contrast to the conventional approach in which the machine control variables such as the heated element temperature, fiber feed velocity and the total draw ratio were used to describe the process. It is shown that the drawing process seldom proceeds by a simple yielding mechanism and that a one‐step drawing process usually involves a yield draw followed by a post‐yield stretching. Using the drawing of nylon 6 fibers as an example, it is shown that the most critical factors related to achieving the highest fiber strength in drawing from a given precursor are the yarn temperature and yarn extension at yielding and during the post‐yield drawing.
Thermoset injection molding dynamics and the distribution of cure in thermoset molded parts
Authors: Sidi Shiraz , Kamal Musa R. 
Published: December 2004

AbstractA detailed characterization of a commercial‐filled unsaturated polyester molding compound has been carried out to determine the kinetics of cure and the rheological behavior of the material at various temperatures and shear rates. Molding experiments were conducted in a 2 1/3 oz, 68 ton reciprocating screw injection molding machine, in conjunction with a simple rectangular cavity. The cavity and nozzle were equipped with pressure transducers to determine, the variation of pressure with position throughout the injection molding cycle. The injection speed was determined with the help of a position transducer. Finally, the moldings were analyzed to determine the distribution of cure states and tensile properties in the molding at various cure times. Significant differences have been observed. It is expected that studies of this type should be helpful in obtaining a better understanding of the thermoset injection molding process and the development of mathematical models to simulate this process.
The hydrolytic stability of some commercially available polycarbonates
Authors: Pryde C. A. , Kelleher P. G. , Hellman M. Y. , Wentz R. P. 
Published: December 2004

AbstractA number of commercially available polycarbonates, including formulations made flame retardant by two different modifications, have been exposed to conditions producing moderately rapid hydrolysis. Hydrolysis rates were calculated from molecular weight data determined by gel permeation chromatography and, in some cases, from melt flow rate data. The rates calculated by the two methods are in good agreement. In general, the standard formulations containing minimal additive packages are the most hydrolytically stable. Although one relatively new flame retardant polycarbonate demonstrates generally good resistance to hydrolysis, most of the flame retardant formulations appear to be quite susceptible to hydrolytic degradation. For these materials, hydrolysis under conditions encountered in use could cause significant decreases in impact strength within a few years.
Rheokinetics of polymerization of N‐laurylmethacrylate
Authors: Kale L. T. , O'Driscoll K. F. 
Published: December 2004

AbstractThe free radical polymerization of n‐laurylmethacrylate has been studied using a combination of rheological and kinetic methods. In addition to classical dilatometry, the extent of reaction of a polymerization was followed in a cone and plate rheometer by measuring the change in the diffraction of a laser beam shone through the polymerizing sample parallel to the plate of the rheometer. The change in diffraction was caused by the change in index of refraction of the monomer becoming polymer, which was related to the extent of reaction. Simultaneous measurements of loss and storage moduli and dynamic viscosity at 1 Hz provided the data necessary for correlating changes in the kinetics with changes in the rheology of the polymerizing system.
The effect of bromination and inherent vinyl unsaturation on the drawing behavior of high‐density polyethylene
Authors: Tincer T. , Akay G. 
Published: December 2004

AbstractVarious high‐density polyethylenes were brominated in order to eliminate the inherent vinyl Unsaturation in the polymer. They were then drawn uniaxially at three different temperatures, and the resulting fibrous materials were studied under a scanning electron microscope. It was found that the brominated samples yielded transparent fibrous materials that had more regular fibrillar structure and fewer surface overgrowths, cracks, and voids compared with the unbrominated polymers drawn under identical conditions. Bromination also appeared to improve the mechanical properties of the drawn and the undrawn polymer. High‐density polyethylene that had no inherent vinyl Unsaturation also yielded transparent fibrous material with fibrillar structure similar to that of brominated polymers.
A network flow analysis of extrusion dies and other flow systems
Authors: Booy Max L. 
Published: December 2004

AbstractA method is presented to calculate the slow viscous flow distribution in systems of passages, for which the major velocity components are substantially parallel to the axes of those passages. That condition is generally satisfied in flat extrusion dies, disc filters, in‐line filters, and other now devices. A finite difference matrix method is initially used to determine the flow distribution for an assumed viscosity distribution. That flow distribution is next used to determine a new distribution of resistances, now based on a specified rheological equation. This process is iterated until there is no significant change in the flow distribution. The passages are subdivided in this method and replaced by a network of resistances. A few unknowns are introduced at one end of the network, which are solved at the other end, using a matrix marching routine. The method is described for newtonian flow through a flat die with equalizing channel, for which the analytic solution is known. Results are shown for that die for flow of power law liquids.
Strength and structure of glassy networks formed from dimethacrylates
Authors: Atsuta M. , Turner D. T. 
Published: December 2004

AbstractGlassy networks were formed by copolymerization of methyl methacrylate (MMA) with both ethylene glycol dimethacrylate (EGDM) and triethylene glycol dimethacrylate (TGDM). The polymerization reaction was followed by estimation of vinyl group concentration from measurements of specific volume and infrared absorption. The sheets of polymer were cracked but gave fragments that were large enough to provide specimens suitable for a three‐point bending test. Flexural strength decreased with increasing feed of dimethacrylate but, nevertheless, gave fairly strong products throughout the range of comonomer compositions c.f. PMMA, 144 ± 9 MPa; PTGDM, 132 ± 10 MPa; PEGDM, 66 ± 15 MPa. Examination of fracture surfaces indicated a predominantly brittle mode of fracture modulated by localized plastic deformation. In order to account for localized plastic deformation, it was postulated that the networks consist of highly crosslinked microgel particles in a much less crosslinked matrix.
Rheological analysis of highly loaded polymeric composites filled with non‐agglomerating spherical filler particles
Authors: Bigg D. M. 
Published: December 2004

AbstractA non‐agglomerating 15 μm diameter stainless steel spherical powder was used as a filler in a low‐density polyethylene matrix. The factors investigated included volume loading, the use of surface treatments, and method of applying the surface treatments. The rheological parameters measured to analyze the effect of these factors on the melt behavior of the mixtures were the dynamic viscosity, η*, and the real component of the shear modulus, G′. These parameters showed clear differences in the response of the composites to volume loading, type of surface treatments, and method of surface treatment application.
Modeling of poly(ethylene terephthalate) reactors: 4. A continuous esterification process
Authors: Ravindranath K. , Mashelkar R. A. 
Published: December 2004

AbstractA mathematical model has been developed for the direct, continuous esterification process. Influence of process and operational variables, including temperature distribution, residence time distribution, bis(hydroxyethyl)terephthalate recycle, pressure, and ethylene glycol (EG) to terephthalic acid ratio on the reactor performance have been investigated in a range as close to industrial practice as possible. The variables influencing the amount of EG reflux (which governs the energy economy) and side products (which govern the product quality) have been discussed. This investigation provides an analysis of a continuous, direct esterification process, and the results indicate strategies for optimizing productivity and product quality.
Conversion prediction in high conversion free‐radical polymerizations
Authors: Balke S. , Garcia‐Rubio L. , Patel R. 
Published: December 2004

AbstractThe objective of this article is to introduce anew general approach For conversion prediction in high‐conversion free‐radical polymerizations–“The Method of Kinetic Similarity.” Using a single homopolymer reference curve of methyl meth‐acrylate (MMA) and one to two time‐scaling parameters, the conversion vs. time curves for MM A, ethyl methacrylate (EMA), vinyl chloride (VC), acrylonitrile (AN), styrene methyl methacrylate (SMMA), and styrene acrylonitrile (SAN) could be well‐described. For MMA and VC, these parameters are shown to obey expected Arrhenius relationships over 45 to 90°CC and 30 to 70°C, respectively. The method is simple to apply, continuous over the whole conversion range, utilizes existing knowledge at low and limiting conversions, and avoids application of usual low conversion assumptions into the diffusion‐controlled region.
Determination of the glass transition of polymer by the autovibron
Authors: Murayama Takayuki 
Published: December 2004

AbstractThe automated Rheovibron (Autovibron) has been useful for determining the glass transition behavior of polymers. The standard (manual Rheovibron viscoelastometer has been used sufficiently small intervals, and so, some accuracy on transition location must be sacrificed when the temperature intervals are taken 5 to 10°C apart. However, the Autovibron can be observed over very small temperature intervals (<1.5°C)), which essentially provide a continous monitoring of the changes in storage modulus, loss modulus, and tan δ. An improved accuracy and sensitivity of the Autovibron are provided by a combination of multiprogrammer, programmable calculator, and lock‐in analyzer. The Autovibron are provided by a combination of multiprogrammer, programmable calculator, and lock‐in analyzer. The Autovibron shows a good capability for dynamic thermomechanometry. The glass transition bility for dynamic thermomechnometry. The glass transition of polymers can be determined by analyzing the loss tangent peak. The maximum value in loss tangent, peak temperature, and the newly introduced terms, ΔT1 and ΔT2 which indicate the widths of tan δ peak, are useful indicators of the glass transition. The ΔT1 and ΔT2 show the distribution of the glass transition and are related to order and crystallinity in the structure.
Extended‐chain morphology in ultraoriented polyethylene
Authors: Macchi Edgardo M. , De Micheli Raul 
Published: December 2004

AbstractThe morphology of ultraoriented polyethylene fibers was investigated by means of small‐angle x‐ray scattering and high‐resolution line‐broadening analysis of x‐ray and electron‐diffraction profiles. The comparative consideration of the experimentally‐measured crystal thickness and long period along the c direction allowed the calculation of the fraction of extended‐chain crystals for a simple three‐phase model. The calculations were carried out with the unknown length of the extended‐chain crystals as a variable parameter.
Rheology of reinforced thermoplastics and its application to injection‐molding: IV. Transient injection capillary flow and injection‐molding
Authors: Akay G. 
Published: December 2004

AbstractA two‐stage injection capillary rheometer fitted to an injection‐molding machine was used to study the transient flow behavior of unfilled polypropylene melt and melts filled with short glass fibers, or long glass fibers, or (alternatively) calcium carbonate particles/Apparent shear rate in the capillaries ranged from 103 to just over 106 s−1, while the initial melt temperature ranged from 180° to 270°C in steps of 30°C. Reservoir pressures at the entrance to the capillaries and the plunger position are also recorded. It is found that the presence of short glass fibers results in more stable flow, especially at low melt temperatures. Significant fiber exclusion at the capillary entrance is only present in long glass fiber‐reinforced melts. At low temperatures, calcium carbonate‐filled melts yield large pressure overshoot, and the flow is the “stick‐slip” type. These melts yield extra pressure overshoot when the flow rate is increased suddenly. If the melt elasticity is high (unfilled polymer), there is a recovery in the reservoir pressures during flow decay following sudden reduction in the flow rate. The significance of injection capillary flow in the injection‐molding of filled polymer melts is demonstrated by following the development of the nozzle pressure during injection‐molding. It is shown that, if the injection speed is high, filled polymer melts yield large nozzle pressure overshoots. Estimates of nozzle pressure based on steady‐flow‐viscosity data will, therefore, be misleading. Fiber‐free and particle‐depleted regions in the moldings are examined. A new mechanism of fiber or particle migration based on flow‐induced crystallization is proposed. The observations reported here for polypropylene concerning fiber migration also apply to nylon 6.6., high‐density polyethylene, and polycarbonate.
Prediction of extrusion pressure loss of polymer melts flowing through noncircular dies
Authors: Tiu C. 
Published: December 2004

AbstractThe geometric parameter method proposed earlier by Kozicki and coworkers for prediction of pressure losses of non‐Newtonian fluids flowing in ducts of arbitrary cross‐section is shown to be applicable for polymer melt flow through complex dies. Good agreement is obtained between the predicted and the published theoretical and experimental results for polystyrene and polypropylene melts flowing in rectangular and trapezoidal dies. The method is simple to use and requires only the knowledge of two geometric parameters to characterize the flow geometry.
Degradation of polyurethane containing phosphorus
Authors: Grassie Norman 
Published: December 2004

AbstractThe fire hazard associated with the use of polymeric materials is partly the destruction of property and partly the hazard to life by toxic fumes. Phosphorus compounds are commonly used as fire retardants. They seem to act principally by modifying the mode of thermal decomposition of the polymer. This results in changes in the pattern of volatile inflammable and potentially toxic products and also in the production of a protective layer on the surface of the burning material. Insight into these processes has been sought by comparing the mechanisms of degradation of a simple polyurethane, pure and in presence of the fire‐retardant ammonium polyphosphate, and of a comparable polyurethane with similar phosphorus structures built into the polymer structure.
Siloxane‐poly(Methylmethacrylate) amphoteric blends
Authors: Blahovici T. F. , Brown G. R. , St‐Pierre L. E. 
Published: December 2004

AbstractPoly([4‐(methacryloyloxy) butyl]pentamethyldisiloxane), PMBPD, has been prepared for the first time. At the weight average molecular weight of 55,900, it is a clear, viscous liquid with a glass transition temperature, Tg, of 236K. Copolymers with methylmethacrylate have also been prepared. The homo‐and copolymers, all of which have methacrylate backbones with pendant siloxane groups, were blended with poly(methyl‐methacrylate), PMMA. Using the existence of a single Tg as a definition of miscibility, it was found that blends of either PMMA or PMBPD with random copolymers are miscible. However, in spite of a clear appearance, the blend of the two horriopolymers were found to have two distinct Tgs.
Some solid‐state properties of blends of polyethylene terephthalate and polyamide‐6,6
Authors: Kamal M. R. , Sahto M. A. , Utracki L. A. 
Published: December 2004

AbstractPolymer blends incorporating polyamide‐6,6 (PA) and polyethylene terephthalate (PET) and having the following PA wt,% concentrations were prepared: 0, 5, 10, 25, 30, 35, and 100. Samples were obtained by molding in a reciprocating‐screw injection‐molding machine. The samples were annealed to minimize frozen‐in stresses without increasing the crystallinity level in the material. Melting and heat‐of‐fnsion data, obtained with the differential scanning calorimeter, suggest an overall increased crystallinity in the blends, as indicated by a significant excess heat of fusion. Whereas the neat polymers exhibit ductile failure under both tensile and impact testing conditions, the blends show brittle behavior. Finally, the abrasion resistance of the blends is inferior to that observed for PET but higher than the resistance of PA.
Techniques for the viscometry of suspensions
Authors: Cross M. M. , Kaye A. 
Published: December 2004

AbstractTechniques are presented for the rotational viscometry of suspensions, using modified cone/plate and parallel plate configurations. For displaced cone‐and‐plate geometry an analysis considers the torque developed on the cone as a function of its angular velocity and the displacement at its apex. The two situations of constant angular velocity and of constant displacement present alternative methods for computing viscosity/shear‐rate data from torque/displacement or torque/angular velocity measurements. Neither method involves any assumption regarding the rheological properties of the test fluid and both can be extended to parallel plate geometry. An alternative and simpler approach uses an annular cone/plate configuration, in which conditions of uniform shear rate can be maintained with an operating gap of the order of 1 mm. The validity of the different techniques is tested by comparison with conventional cone‐and‐plate measurements, using a non‐Newtonian solution of polyisobutylene as a test fluid.
The effect of radical desorption on the particle size distribution in vinyl acetate emulsion polymerization
Authors: Lu Ying‐Yuh , Lin Chen‐Chong 
Published: December 2004

AbstractThe effect of free radical desorption is studied by using a mathematical model of particle size distribution in continuous emulsion polymerization. By comparing the theoretical prediction with experimental data, the value of Do for the vinyl acetate (VAc) system is best chosen as 0.19 × 10−7 cm2/h. The effect of radical desorption as well as mean residence time on the absolute particle size distribution, total concentration of polymer particles, conversion, and average number of radicals per polymer particle are analyzed by the model proposed.
Electrically conductive composites prepared from polymer particles coated with metals by electroless deposition
Authors: Narkis M. , Yacubowicz J. , Vaxman A. , Marmur A. 
Published: December 2004

AbstractPolystyrene particles were coated by electroless deposition of copper, nickel or copper and nickel. The metal‐coated polystyrene particles were molded at high temperature and pressure into plaques, in which the metallic shell continuity was preserved and a continuous conducting metal network was formed. Very high conductivities at low metal concentrations (less than 1 percent v/v) are obtained by this procedure. The resistivity, dielectric constant, and dissipation factor of these metal containing composites are presented as functions of the metal concentration, frequency, and temperature. The metal containing composites exhibit reasonable flexural properties.
Ethylamine and ammonia as catalysts in the in‐situ precipitation of silica in silicone networks
Authors: Ning Y. P. , Mark J. E. 
Published: December 2004

AbstractBoth ethylamine and ammonia in aqueous solutions catalyze the hydrolysis of tetraethylorthosilicate to precipitate silica filler within poly(dimethylsiloxane) elastomers. The rate of filler precipitation can vary in a complex manner, possibly due to loss of colloidal silica and, in the case of the ethylamine solutions, deswelling of the networks. Increase in catalyst concentration increases the precipitation rate, and increase in amount of filler precipitated dramatically increases the modulus and ultimate strength of the networks, thus demonstrating the desired reinforcing effects.
Process control of polymer extrusion. Part II: Feedforward control
Authors: Yang Bing , Lee L. James 
Published: December 2004

AbstractA feedforward plus feedback control method (FFC) and an adaptive feedforward plus feedback control method (AFFC) were proposed in this study to control the extrudate thickness of polymer extrusion. They were tested by step changes of screw speed and feedstock, and square wave type of screw speed changes. It is found that these feedforward control methods worked very well for various load disturbances but they required a good process model and accurate on‐line measurements of manipulated variables and load variables. The feedback function was necessary to compensate the over‐ or under‐corrections of the feedforward controllers and to handle other disturbances which were not considered in the feedforward model.