bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting the effect of screw wear on the performance of plasticating extruders
Authors: Klein Imrich
Published: December 2004

The effect of screw wear on the performance of a 2.5 in. diameter extruder is studied with the aid of computer simulations. The effect of progressively increasing flight clearance on the extrusion of low density polyethylene, polypropylene and nylon 6/6 is presented. The remedial effect of increased screw speed and its side effects on melting behavior, solids content, extrudate temperature and power consumption are also described.
The determination of the fracture parameters for polymers in impact
Authors: Plati E. , Williams J. G.
Published: December 2004

A method of analysis is given by which the critical strain energy release rate Gc for impact tests may be deduced for both Charpy and Izod tests from normal energy measurements. Suitable calibration factors are determined and the method is applied to a range of polymers. Very close agreement is achieved between the Charpy and Izod results except for highly ductile materials for which it was necessary to use a fully plastic analysis. The method is extended to blunt notches and it is shown that the use of a strain energy per unit volume to yielding, together with a blunt notch stress analysis, gives a good description of the results.
Environmental effects on deformation, strength, and degradation of unidirectional glass‐fiber reinforced plastics. II. Experimental study
Authors: Ishai Ori
Published: December 2004

Glass‐fiber reinforced epoxy (GRP) and unfilled epoxy specimens were exposed to different environmental conditions consisting of hot‐ and cold‐water absorption and subsequent drying. Effects of the environmental history on deformational and strength characteristics of the composite material were investigated.

GRP specimens exposed to hot water undergo pronounced degradation, which sets in shortly after exposure and is associated with a significant irrecoverable weight loss. Degraded specimens are characterized by higher void content and lower strength compared with their cold‐water and reference counterparts. The degradation process is attributed to penetration of water into the matrix‐fiber interfaces and is followed by an attack, at high temperatures, on the glass‐fibers surface and coupling agent. As a result, glass constituents are leached out and then removed from the system by diffusion.

The degradation effect was also confirmed by micro‐observation of the fractured surfaces and by infra‐red spectroscopy. A simple and effective testing method is recommended, permitting detection of degradation onset and its progress by simultaneous measurement of weight and dimensional changes with time.
Development of computer control strategies for plastic extruders
Authors: Parnaby John , Kochhar Ashok K. , Wood Brian
Published: December 2004

The basic idea of automatic control of extrusion machinery is considered. Dynamic interaction among process variables is discussed and it is suggested that a practical form of control might involve steady‐state control of screw and barrel temperature coupled with dynamic control of screw speed. Several alternative forms of control strategy are examined and it is suggested that for higher forms of control, a computer is required together with an accurate process model relating control and controlled variables. With such a strategy, polymer temperature and pressure at the die would be controlled by continuous variations in screw speed coupled with infrequent control of die resistance to counter long term drift and to facilitate pressure and temperature change matching. Methods for developing process models are considered including those for adaptive/predictive control strategies using time‐series techniques and some experimental results are given. The basic form of a computer control system is outlined and the areas where further research is required are indicated.
Inferences concerning the amorphous regions in polyethylene of different morphologies
Authors: Dole Malcolm
Published: December 2004

Using a liquid nitrogen quenching method for the measurement of the ppm of hydrogen dissolved in polythylene (PE) at atmospheric pressure, solubility data were obtained for the following types of samples of linear PE: bulk, single crystalline and extended chain. For samples of equal amorphous volume fraction, the hydrogen is about 10‐fold more soluble in single crystalline PE than in bulk. The solubility in extended chain samples becomes more abnormal, the higher the crystallinity. No hydrogen dissolves in a perfect C20 H42 crystal. The excessive solubility in the single crystalline samples is interpreted in terms of more sorption sites in the folded part of the chains in the amorphous surface layers than in bulk PE. As the heat of sorption changes from endothermic to slightly exothermic in passing from the bulk to the single crystalline or extended chain samples, the sorption sites must pre‐exist in the latter two types.
The flow of non‐Newtonian solutions through packed beds
Authors: Park H. C. , Hawley M. C. , Blanks R. F.
Published: December 2004

The rheological behavior of aqueous solutions of Separan AP‐30®, polymethylcellulose, and polyvinylpyrrolidone was studied experimentally. These solutions exhibit non‐Newtonian flow behavior in simple shear, and are characterized by one of several 2, 3, or 4 parameter rheological equations. The equations used included the power law, the Ellis model, Spriggs equation, the Herschel‐Bulkley equation, and Meter's model. The power law model fits the data for each of the solutions over a limited range of shear rates, whereas the other models, which include either a lower shear rate limiting Newtonian viscosity, and/or an upper shear rate limiting Newtonian viscosity, or a yield stress, fit the data well over a wide range of shear rates from 0.00675 to 1076 sec−1. The pressure drop‐flow rate data for the same aqueous solutions flowing through packed beds were correlated well by the Ergun equation using the various rheological models applied in this work to evaluate a modified fluid viscosity. In each case it was found that the rheological model which best fit the viscometric data also gave the best packed bed friction factor correlation, and that no one model, such as the powerlaw, or the Ellis model, is the best one to use in all cases for all solutions. For polyvinylpyrrolidone solutions large deviations between experimental values of friction factor and those from the Ergun equation occurred for modified Reynolds numbers greater than one. A pseudo viscoelastic parameter was used to improve the friction factor correlation empirically at high Reynolds numbers.
Strength of polymethylmethacrylate in air and in n‐propanol
Authors: McCammond D. , Ward C. A.
Published: December 2004

A series of tests was conducted to measure the failure strengths of notched polymethylmethacrylate tensile specimens in air and n‐propanol. Tests were conducted on specimens which had been subjected to creep stresses of various magnitudes and for different times. The resulting data indicate that two opposing factors contribute to the fracture strength in n‐propanol. The presence of fluid during crack propagation increases the nominal fracture failure stress. Diffusion of the fluid into the polymer produces crazing resulting in the provision of a preferential crack path and consequent lowering of the fracture strength. The former mechanism dominates at small pre‐stresses or at short creep times, resulting in an increase in strength in n‐propanol over that in air. However, the latter mechanism is dominant at higher creep stresses and longer creep times with a resulting decrease in strength in n‐propanol compared to that in air.
The migration of plasticizers from poly(vinyl chloride) into edible oils
Authors: Kampouris Emmanuel M.
Published: December 2004

The migration of phthalate plasticizers from poly (vinyl chloride) into edible oils has been analyzed. The principal method used involved 14C‐labeled dibutyl and dioctyl phthalates with detection by liquid scintillation spectrophotometry. In most cases, the migration of the main plasticizer was accompanied by the migration of the secondary plasticizer, when present, and by diffusion of the oil into the polymer. Comparison of the scintillation results with those obtained by weight loss measurements can give quantitative information on the amount of the liquid medium that diffuses during the migration process. The effect of the following factors on the migration process was examined; (a) the nature and acidity of the edible oil, (b) the composition and amount of phthalate plasticizer, (c) the amount of epoxy plasticizer, and (d) the temperature and time of contact.
Uni‐ and biaxial stretching of chlorinated pvc sheets. A fundamental study of thermoformability
Authors: De Vries A. J. , Bonnebat C.
Published: December 2004

Chlorinated PVC is superior to unmodified PVC as a thermoplastic for use in thermoforming, especially if improved heat resistance and dimensional stability are required. In the present report, results tire given of a fundamental experimental study on the thermoformability of CPVC sheets obtained by calendering various formulations based on CPVC resins with at least 65 percent chlorine content. Extensibility as well as the relationship between stress and strain in uni‐ and biaxial stretching have been determined as a function of temperature and rate of stretching by means of specially devised, highly instrumented laboratory equipment. Stress‐strain relations under isothermal conditions and at constant strain rate are compared for the two modes of stretching, and the difference in behavior between PVC and CPVC, particularly with regard to the effect of temperature, is emphasized. Internal stresses frozen in during cooling, following rapid stretching at appropriate thermoforming temperatures, have been determined by means of a detailed analysis of retractive force measurements. The relationship between internal stress and molecular orientation is discussed as well as the effect of the latter parameters on various properties of technological interest: dimensional stability, impact resistance, and gas permeability.
A study of chain addition polymerizations with temperature variations: III. Thermal runaway and instability in styrene polymerization—an experimental study
Authors: Sebastian D. H. , Biesenberger J. A.
Published: December 2004

Thermal runaway arid parametric sensitivity were experimentally demonstrated in styrene polymerizations. Ignition boundaries were established for several initiator concentrations and a dimensionless boundary plotted. Runaway sensitivity was shown to disappear under specific conditions.
Crystallization from a strained melt or solution
Authors: Peterlin A.
Published: December 2004

The elongation and orientation of randomly coiled macromolecules in a strained melt or solution reduces their entropy and thus increases the crystallization or melting temperature of the ideal lattice. At any given temperature of experiment this enhances nucleation and crystal growth rate. As a rule, linear primary nuclei are formed. They contain more or less extended chains. The existence of row nuclei reduces the local gradient in the liquid to such an extent that further crystallization proceeds by epitaxial overgrowth of folded chain lamellae. Densely packed cylindrites are formed with the ribbon‐like lamellae radiating from the central row nucleus. The irregular shish‐kebab structure observed in stirred or sonicated solutions seems to be formed by subsequent exial deformation of cylindrites in the flow field. It displaces the lamellae irregularly and thus produces a great many microfibrillar elements parallel to the original row nuclei. The almost completely extended chains in the shish yield a high elastic modulus and tensile strength for exial loading. The shish‐kebab morphology in fibers as spun does not affect to a great extent the mechanical properties obtainable by subsequent drawing. The lamellae are transformed into microfibrils in very much the same manner as in spherulitic samples. But the highly regular orientation of lamellae seems to result in a more uniform drawing and hence a stronger fiber. In an extremely high temperature and pressure gradient, the melt extrusion produces hard elastomers where the lamellae of the cylindrites seem to be locally stapled. Upon application of tensile load in the extrusion direction, the intervening sections bend like beams, thus forming thin holes extending in the direction perpendicular to the load. The holes enormously enhance the permeability for gases and liquids. The elastic bending of lamellae yields the high recoverable strain and low tensile modulus.
Morphological changes during oriented polymer crystallization
Authors: Gaylord R. J. , Lohse D. J.
Published: December 2004

A theory of the stress‐induced crystallization of polymeric networks is presented which takes into account 1) the free energy of fusion, 2) crystal surface energies and 3) entropic changes in the amorphous sections of crystallizing chains. It is assumed that the vector running from one end to the other of the crystallite is oriented in the direction of network extension, irrespective of crystal morphology, thus minimizing the free energy of crystallization. Assuming that the network assumes the crystal morphology which minimizes the free energy of the network at a given degree of crystallinity and that the crystallization proceeds along this lowest free energy path, it is predicted for simple network extension that growth of a perfectly oriented extended‐chain crystal occurs initially, changing to a one‐fold crystal oriented perpendicular to extension at low extension and to a two‐fold crystal having nearly perfect orientation at High extension. The stress is predicted to decay initially and then to rise as the network chains switch from an extended‐to a folded‐chain morphology. Spatial factors which may trap chains in the ex tended‐chain morphology or prematurely stopping the crystallization process can result in a mixed crystal morphology. At high extension, the structure is similar to that of the shish kebab.
Crystallization of networks under stress
Authors: Smith K. J.
Published: December 2004

A theory of crystallization under stress is developed about the premise that the direction a chain takes through a crystallite, relative to its end‐to‐end vector, is determined by the first few links of a chain that initially deposit onto the crystallite surface. Since these few links are quickly trapped by subsequently crystallizing chains, their orientational probability prior to deposition governs the chain direction through the crystallite, and the properties of the system depend upon a statistical distribution of all vector orientations. Such a model leads to a relationship between the melting temperature and the degree of network orientation, and relates the retractive force to temperature in the crystallization region. The theory appears to adequately describe some of the published data on rubber and polychloroprene networks.
Unlimited flex life in the molded‐in hinge in polypropylene: A structural hypothesis
Authors: Clark E. S. , Spruiell J. E.
Published: December 2004

Injection molded hinges of polypropylene possess uniquely unlimited flex life. Polypropylene when crystallized from the melt under extensional flow (as in injection, molded hinges), shows a unique morphology characterized by a planar row structure of lamellae accompanied by a bimodal distribution of the unit cells having the alpha crystal phase. This bimodal orientation consists of two apparently independent orientations of the unit cells with respect to the flow direction: one with the c‐(chain) axis parallel to and one with the a′‐axis parallel to the flow direction. (The a′‐axis is a vector normal to (100) and thus parallel to a* in reciprocal space.) Experimental data on the morphology of polypropylene crystallized under extensional flow are interpreted in terms of two components. The c‐axis component corresponds to those molecules in the planar row structure. The a′‐component is attributed to secondary crystallization in which small crystallites are finely dispersed between the lamellae of the row structure. These small crystallites act as a “morphological plasticizer” protecting the load‐bearing row structure from destructive stress during flexure.
The effect of molecular weight on the physical and mechanical properties of ultra‐drawn high density polyethylene
Authors: Perkins William G. , Capiati Numa J. , Porter Roger S.
Published: December 2004

A study has been made on the effects of molecular weight on the physical and mechanical properties of cold‐extruded high density polyethylene. Prior data indicate that such ultra‐drawn strands contain a significant fraction of extended‐chain crystals. Four samples, spanning the molecular weight range of 59,000 to 147,000, were cold‐extruded under the same conditions and were examined with respect to their melting point, degree of crystallinity, linear expansion coefficient, Young' modulus, strain to break, and tensile strength. The degree of crystallinity, linear expansion coefficient, and modulus did not change significantly with molecular weight. The melting point, strain to break, and tensile strength do increase with increasing molecular weight. This leads to the conclusion that the amount of extended‐chain crystals is invariant with molecular weight. Higher molecular weight polymers are seen as providing a greater number of the chains, thus giving the fiber a higher tensile strength.
Recycling of thermoplastic waste: Phase equilibrium in polystyrene‐PVC‐polyolefin solvent systems
Authors: Sperber R. J. , Rosen S. L.
Published: December 2004

The contribution of plastics to the total amount of waste produced is increasing significantly. Not only do plastics present disposal difficulties, but traditional disposal techniques constitute a waste of valuable resources. A process to recycle plastic waste economically would provide an attractive solution to both problems. Approximately 70 percent of the U.S. plastics production is comprised of only three families of plastics; polyethylene, PVC and polystyrene. Mixtures of these three polymers invariably have poor properties because of their thermodynamic incompatibility, so a recycle scheme will have to achieve separation into nearly pure components. A process is proposed which takes advantage of the thermodynamic incompatibility of polymers in solution to effect such a separation. The equilibration of a simulated waste mix containing 4 parts polyolefin (polyethylene and polypropylene), 1 part polystyrene and I part PVC was investigated in a variety of solvents at total polymer concentrations of up to 15 percent, in the temperature range 115 to 125°C, using differential refractometry. In an 85 percent xylene, 15 percent cyclohexanone solvent, the polyolefins (polypropylene and the various densities of polyethylene) coexisted in a single phase, but the three phases obtained—polyolefin, polystyrene and PVC—routinely contained 99 + percent pure polymer, indicating that excellent separations of the major thermoplastic components of a waste mix can indeed be obtained.
Effect of reinforcement type on the mechanical properties of polypropylene composites
Authors: Richardson George C. , Sauer John A.
Published: December 2004

The possible reinforcing effects of six different types of filler particles on composites based on the thermoplastic polypropylene have been examined. It is found that significant increases in elastic modulus and tensile strength can be obtained by addition of ≥ 10 percent by volume of glass fibers. Ceramic whiskers, based on alumina and silicon carbide, also lead to increases in modulus but to decreases in strength and ductility. Additional measurements were made with composites prepared from two sizes of spherical glass beads and from carbon spheres. For the glass beads, an increase in modulus was obtained but strength and elongation to fracture decreased. Carbon spheres were ineffective as a reinforcing agent. The possible effects of nonuniform mixing, of size and shape of filler particles, and of surface coatings are discussed.
Effects of oven aging on ABS, poly(acrylonitrile‐butadiene‐styrene)
Authors: Wyzgoski Michael G.
Published: December 2004

Tensile properties of injection and compression molded ABS, terpolymer of acrylonitrile, butadiene, and styrene, were measured as a function of aging time at 40 to 90°C. Both air and nitrogen atmospheres were employed to separate the oxidative and thermal effects. Results demonstrate that tensile elongation is drastically reduced by oven aging at 50 to 90°C, even when a nitrogen atmosphere is employed. Aging in air causes changes in the infrared spectra of ABS and these changes can he monitored in thick samples using the frustrated multiple internal reflection (FMIR) technique. The FMIR technique also provides information on the changes in polybutadiene distribution near the surface of molded parts. The loss of tensile elongation after oven aging is attributed to annealing of the glassy styrene‐acrylonitrile matrix. This is supported by differential scanning calorimetry. The tensile elongation is found to he recoverable by reheating to processing temperatures.
Constitutive relationships for the mechanical properties of anisotropic, partially crystalline polymers
Authors: Seferis J. C. , McCullough R. L. , Samuels Robert Joel
Published: December 2004

Constitutive relationships are presented to relate the directional dependence of the mechanical properties of anisotropic, partially crystalline polymers to (a) the percent crystallinity, (b) characteristics of the crystalline and amorphous orientation distribution, and (c) the mechanical properties of the crystalline and amorphous components. These relationships were tested with structural and dynamic mechanical data obtained for isotactic polypropylene films in various states of crystalline and amorphous orientation. The dynamic mechanical properties of the crystalline and amorphous components were treated as parameters and evaluated from dynamic mechanical measurements along the longitudinal and transverse direction of three different film samples. These mechanical parameters, and the associated structural parameters, were in turn used to predict the dynamic mechanical spectra for a fourth, independent, film sample. The predicted values for the storage and loss modulus, along various directions of loading, were within 10 percent of the measured values over the temperature range of −80°C to 80°C.
Characterization of thermosetting materials by torsional braid analysis
Authors: Gillham J. K.
Published: December 2004

Experimental examination by torsional braid analysis (TEA) of the phenomena of gelation and vitrification which occur in the formation of thermosets leads to a general way of regarding both thermoplastics and thermosets. In particular,‐ it is demonstrated that the thermosetting process is characterized by two transition temperatures, Tff and Tg∞. Implications of this finding are discussed for cross‐linking systems in general.
Antistatic polyphenylene oxide by surface sulfonation
Authors: Lee Sheng Yen , Corbino S. , Wood G. B.
Published: December 2004

Polyphenylene oxide was surface‐sulfonated with chlorosulfonic acid to provide antistatic properties. Optimal treatment time was shown to be 2–3 mins with a saturated solution of the acid in hexane or 25–30 mins using acid vapor‐saturated air under the given experimental conditions at room temperature. Being sensitive to humidity, the resistivity of the treated surface was lowered to the magnitude of 107 to 108 ohm/square at 43 percent relative humidity and to 1011 at 10 percent relative humidity. The vapor phase method was found to be superior to the solution method with respect to the durability of the treated surface against water washing. Microscopic examination revealed extensive surface erosion by the solution treatment.
Temperature and rate dependent fracture in glass‐filled polystyrene
Authors: Mai Y. W.
Published: December 2004

The rate and temperature dependent fracture behavior of glass‐filled polystyrene has been investigated over the crack speed range of 1013 to 1 mm/sec and in the temperature range 283 to 396°K for three environmental conditions: (i) air; (ii) water; and (iii) hot water exposure at 363°K and subsequent drying. Relationships between fracture toughness (Kc), crack speed and temperature have been obtained experimentally and analysed according to the concepts of fracture mechanics and reaction rate theories. Crack propagation in air is shown to be controlled by a β‐relaxation process associated with crazing. Activation energies of 200 ∼ 210 kj/mole in air and 80 ∼ 120 kj/mole in water are reported. At a given temperature and crack speed, the glass‐filled polystyrene is shown to display smaller crack propagation resistances in a water environment when compared with the air results. Specimens subjected to hot water exposure and then tested after drying also possess less cracking resistance. This toughness degradation phenomenon is a result of the damaging effects of the water which penetrates into the glass‐filled composite.
Annealing effect on the microstructure of poly(vinyl chloride)
Authors: Ohta S. , Kajiyama T. , Takayanagi M.
Published: December 2004

The effect of annealing on the microstructure of commercial grade poly(vinyl chloride) was investigated by calorimetric, X‐ray and viscoelastic measurements. The degree of crystallinity increases with increasing annealing temperature from above the glass transition temperature up to 130°C, at which point the degree of crystallinity takes on a maximum value. Also, the crystal melting temperature increases with increasing annealing temperature. Thermal analysis and X‐ray study suggest that the crystallite of poly (vinyl chloride) decomposes by thermal degradation when annealed, above 170°C. The isothermal crystallization process is analyzed using Avrami's equation employing the degree of crystallinity as a function of annealing time at various annealing temperatures. The crystallization rate has a maximum value at around 140°C. It is expected that the crystalline texture grows in the shape of a lineal‐like habit, judging from the magnitude of Avrami's constant and from a study of the X‐ray intensity distribution. The αf‐transition was observed to occur at temperatures 5 to 10°C lower than the crystalline melting temperatures for annealed specimens of poly(vinyl chloride) using a dynamic spring analysis. The αf‐transition may be attributed to thermal molecular motions with a long time scale, resulting from the cross‐link points introduced by the small crystallites.
Mechanical properties of oriented polyethylene/polystyrene blends
Authors: Stell J. R. , Paul D. R. , Barlow J. W.
Published: December 2004

Incompatible blends comprised of polystyrene and various high density polyethylenes were processed into tapes, in which both the phase and molecular orientations were parallel to the machine direction, by a combination of extrusion and mechanical stretching of the melt prior to quenching. Machine direction tensile yield strengths and ultimate elongations were found to be considerably higher than those obtained for comparable compression molded samples throughout the range of blend compositions and processing conditions investigated. Transverse tape properties were consistently poor due to poor interfacial adhesion. An optimum in machine direction properties was observed as the stretch ratio was increased at various melt temperatures. This optimum is likely due to a competition between morphological and molecular orientation rates during the stretching process and is a complex function of stretching rate and melt temperature as well as blend composition, relative phase viscosities, polyethylene crystallinity, and interfacial adhesion. Tapes stretched at high melt temperatures tended to show decreasing ductility and increasing tensile strength as room temperature storage time increased. This is believed to be due to secondary crystallization of the polyethylene phase. Oriented tapes were found to be easily fibrillated by mechanical heating to form a pulp. This material may prove suitable as a high grade replacement for cellulose pulp in paper making and could be formed at low cost from waste plastic feed stock.
Decorative coating of plastics by vapor deposition of various alloys
Authors: Richman Jay
Published: December 2004

Stringent government environmental regulations applied to the electroplating industry have spurred a search for alternative means of providing chromium coatings on plastics. Vapor deposition, an established and extensively utilized process for applying aluminum coatings on plastics, is quite naturally being investigated as an alternative process. Vapor deposited chrome has a darker cast than electrochrome, and a great‐number of materials are being investigated to find a color matching substitute that will stand up under severe environmental conditions. Among these are the 300 and 400 series stainless steels, nichrome, and other alloys. It has been found, with proper surface preparation, that highly adherent and specular stainless steel coatings/can be obtained oh plastics using filament and boat evaporation techniques. The coatings resemble a highly polished version of the parent metal and bear a striking resemblance to chrome. However, some type of clear topcoat is required to provide abrasion resistance.
Methods for predicting the thermal conductivity of composite systems: A review
Authors: Progelhof R. C. , Throne J. L. , Ruetsch R. R.
Published: December 2004

The thermal conductivity of a solid or gas filled polymer is used in processing or end use application calculations. Numerous theoretical and empirical correlations are found in the literature. A careful review of these models indictes that no one correlation or technique accurately predicts the thermal conductivity of all types of composites. The investigation indicated that for solid filled composites the Lewis and Nielsen equation fitted the experimental data best for the range of fillers tested. However, for a gas filled polymer, none of the theoretical models proved adequate. The semi‐empirical approach of Harding showed considerable merit.
The mechanical behavior of polyarylsulfone
Authors: Wann R. J. , Martin G. C. , Gerberich W. W.
Published: December 2004

A detailed study of the fracture behavior of polyarylsulfone was conducted over a temperature range of −175 to 120°C. Both fatigue crack propagation and fracture toughness tests were run as well as forced torsion pendulum tests to characterize the dynamic properties. The polymer exhibited a broad secondary loss peak and a high glass transition temperature at −110 and 295°C, respectively. Fracture toughness,KIC, and fatigue crack growth resistance were found to vary similarly with temperature, minima being observed near −50°C. Below that temperature, both a rise in toughness and in fatigue resistance is associated with the broad secondary loss peak. The slopes of the log fatigue crack velocity (da/dN) vs log stress intensity range (ΔK) curves varied from 2.6 to 13.2. Since the equation da/dN= α(ΔK)ndescribed all of the data, the log‐log slope or exponent,n= ∂ln(da/dN)∂ln ΔK, was considered as a stress intensity sensitivity index with respect to fatigue behavior. This index was at a maximum near −50°C, where the minimum in toughness occurred. A kinetic model was utilized to correlate the stress intensity sensitivity index and suggested that a single thermally activated mechanism controls the low temperature mechanical behavior of polyarylsulfone.
Electrostatic powder mixing
Authors: Tucker Charles L. , Suh Nam P.
Published: December 2004

A device has been developed which uses electrostatic forces to mix powders. This mixer has no moving parts, and the mixture it produces approaches a perfect mixture whereas mechanical devices can at best produce a random mixture. The device is described, as are experiments which exhibit its operation. Also included are a mathematical model describing the behavior of the device, suggestions for scale‐up procedures, and h discussion of some closely related concepts of mixing.
Parametric concepts in liquid rotational molding
Authors: Progelhof R. C. , Throne James L.
Published: December 2004

A description of the fluid mechanics and the energy transfer mechanisms present in a liquid rotational molding system is discussed. A simplified model assuming the liquid can be drawn off in a continuous layer over the mold surface was assumed. For the case of a negligible energy of reaction, a closed form analytical solution has been developed. The effects of mold composition and polymer thickness on the heating and cooling cycles have been analytically determined. The more complex problem, which includes the energy of reaction, has been solved for a representative case.
A generalized melt viscosity‐temperature dependence for styrene and styrene‐acrylonitrile based polymers
Authors: Mendelson Robert A.
Published: December 2004

The dependence of the melt flow of polymers on temperature is of both theoretical and commercial importance. A useful representation of the temperature dependence of the shear‐dependent viscosity, based on superposition of flow curves at various temperatures, has previously been presented by the author for several olefin polymers. This method is extended in the current work to styrene and styrene‐acrylonitrile based polymers. The melt viscosity‐temperature dependence of a broad range of styrenic polymers and copolymers, ranging from polystyrene to 82 percent AN styrene‐acrylonitrile copolymer, with and without rubber inclusions, was investigated. Flow curves at the various temperatures were found to be superimposable, as had earlier been found to be the case for olefin polymers, and a unique quantitative relationship between the superposition shift factors and temperature was found applicable to the entire family of polymers. The resultant energy of activation for viscous flow is in excellent agreement with previously published results for polystyrene Newtonian viscosities, and the magnitude of the shift factors is consistent with a limited set reported for ABS polymers. Independent tests of the derived relationships provided excellent prediction of measured viscosities. Thus, it is considered that a general viscosity‐temperature relationship has been defined for this family of polymers, independent of molecular structural detail.
Studies on multilayer film coextrusion I. The rheology of flat film coextrusion
Authors: Han Chang Dae , Shetty R.
Published: December 2004

Multilayer flat film coextrusion was studied, both experimentally and theoretically. For the experimental study, a sheet‐forming die with a feedblock was designed, and plastic films of three and five layers were coextruded. The die was provided with three pressure transducers in the axial direction in order to determine the pressure gradient in the die, allowing the determination of the reduction in pressure drop when different combinations of two polymer melts were coextruded. Polymers used for coextrusion were: (1) low density polyethylene and ethylene‐vinyl acetate; (2) low density‐polyethylene and high density polyethylene; (3) low density polyethylene and polystyrene. For the theoretical study, the z‐component of the equations of motion for steady fully‐developed flow were solved using a power law non‐Newtonian model, Comparisons were made between the experimental and the theoretically predicted volumetric flow rates. Predictions of the velocity distributions, shear rate profiles, and shear stress distributions were made as functions of the processing conditions and the rheological properties of the individual polymers concerned.
Non‐isothermal rheological response in melt spinning and idealized elongational flow
Authors: Matsui M. , Bogue D. C.
Published: December 2004

Almost all polymer processing operations involve moving and shaping the polymer as a melt and then cooling it, usually quite rapidly, to a solid state. In order to develop models for such processes we have begun systematic studies in non‐isothermal rheology; here we interpret the results in the context of melt spinning. Theoretical predictions of stress vs distance from the spinneret were calculated from generalized (non‐isothermal) viscoelastic theory and compared with Dees' melt spinning data on high density polyethylene. Despite certain experimental and theoretical difficulties, the agreement is good. Surprisingly, an additional theoretical curve, based on a simple Trouton viscosity, also gave a reasonable approximation over much of the distance, despite the transient nature of the flow. To understand this phenomenon further, a more tractable theoretical problem was studied in detail; the problem, of constant elongational flow (Ė= constant) in the presence of a constant rate of temperature change (dT/dt= constant). The results depend on two dimensionless groupings; the first is the usual product of a relaxation time andĖ; the second involves the ratio of normalized dT/dttoĖ. When the second group is large, a quasi‐viscous state exists. The melt spinning data for the HDPE may be near this state.
Reduction of internal stresses in injection molded parts by metallic fillers
Authors: Kubat Josef , Rigdahl Mikael
Published: December 2004

The build‐up of internal stresses in injection molded parts is due to the combined effect: of a low thermal conductivity (diffusivity) of normal polymer melts and their rapid cooling in the mold cavity. The present paper shows that increasing the thermal diffusivity of the polymer by the addition of relatively small amounts of metallic fillers resulted in a substantial reduction in the internal stress level. The filler content was of the order of a few percent by volume. The average internal stress (σi) was determined by a stress relaxation method. The modulus, tensile strength, and other mechanical properties of the samples were not influenced by the filler addition. The impact strength, however, decreased sharply, as no adhesion pro‐motors were used. The observed improvements in mold shrinkage, thermal shrinkage, hardness, and stress‐cracking tendency could be related to a decreased σi level. In comparative experiments with other fillers (MgO, glass powder), a good correlation was found between the σi level and the thermal diffusivity of the filler.
Properties, environmental stability, and molding characteristics of polyphenylene sulfide
Authors: Hill H. Wayne , Brady D. G.
Published: December 2004

Polyphenylene sulfide is a new engineering plastic characterized by a unique combination of useful environmental, mechanical, and flame resistant properties. This paper presents a variety of new developments in molding methods and long term properties of polyphenylene sulfide. Optimum conditions for fabrication by injection molding, compression molding, and free sintering techniques are described along with a comprehensive tabulation of mechanical, factional, and electrical properties of various filled and unfilled compositions. The effect of injection molding conditions and post‐treatments, such as annealing, on mechanical behavior is discussed. Long term stability of molded specimens of the polymer to a variety of chemical environments as well as oven aging studies are reported. The significance of these properties is illustrated by a discussion emphasizing new applications for various compositions based on polyphenylene sulfide.
A method for the rapid processing of thermoplastic articles
Authors: Erwin Lewis , Suh Nam P.
Published: December 2004

A new method for increasing the productivity of molded polymeric articles and a new kind of molding material are described. This process eliminates the heating and cooling time associated with the conventional injection molding process. Polymeric granules with heterogeneous dielectric loss characteristics are used so that during dielectric heating the surfaces of the granules melt and fuse. During cooling, the heat flows from the shell of each granule to the core, rendering the article rigid almost immediately. An analysis is done which shows that this process is feasible. Based on the analytical results, the material requirements are specified. Experimental results confirm the theoretical predictions and the viability of the basic concept. Heating and cooling are accomplished in a time period of the order of 1 sec.
Frictional behavior of solid polymers on a metal surface at processing conditions
Authors: Chung C. I. , Hennessey W. J. , Tusim M. H.
Published: December 2004

The frictional coefficients of three glassy polymers (polystyrene, polycarbonate, and polymethylmethacrylate) and three crystalline polymers (high density polyethylene, low density polyethylene and polypropylene) on a highly polished steel surface were measured at high temperatures, high pressures, and high speeds, all comparable to actual processing conditions. The frictional behavior of these polymers was found to depend on temperature, pressure‐and speed in a very complicated manner. There appears to exist inter‐relationships among the temperature, pressure and speed dependences of the frictional coefficients. The frictional coefficients of ductile, crystalline polymers as a function of temperature appear to undergo two distinct transitions: one associated with yielding and the other associated with melting. The frictional coefficients of glassy polymers go through only one transition, associated with the glass transition. The friction‐generated heat at high pressures and high speeds can increase the sliding interface temperature of a polymer to values much greater than the metal surface temperature, and thus the polymer can start to melt (or plasticate) at metal surface temperatures appreciably below its thermodynamic melting (or glass transition) temperature.
Polymeric adsorbents for treatment of waste effluents
Authors: Kunin Robert
Published: December 2004

A significant advance in ion exchange resin and adsorbent technology has been the development of the macroreticular pore structure. Synthetic rotes have been developed for preparing both ion exchange resins and polymeric adsorbents of high surface area and pore volume. Syntheses have been developed to the degree that the surface area and pore.parameters can be widely varied. Several of these macroreticular polymers based upon the crosslinked styrene and acrylate systems are now available commercially. These polymeric adsorbents are hard, durable, insoluble spheres of high surface area and porosity. They are available in a variety of polarities. The nonpolar adsorbents are particularly effective for adsorbing nonpolar solutes from polar solvents. Conversely, the polar adsorbents are very effective for adsorbing polar solutes from nonpolar solvents. Of particular interest is the use of these polymeric adsorbents for the treatment of effluent wastes. In some cases it has been demonstrated that one can recover significant quantities of re‐usable chemicals that more than pay for the waste, treatment. The use of the polymeric adsorbents for the treatment of phenolicwastes is an example. Other related applications include the removal of chlorinated pesticides, TNT residues, and other noxious compounds from waste effluents and water supplies.
Solubility of supercritical gases in polymers—a review
Authors: Bonner David C.
Published: December 2004

Processing of polymers is greatly affected by the presence of dissolved gases. Analysis of the effect of dissolved gases requires two types of information: equilibrium thermodynamic data and predictive correlations as well as diffusion rate data and analyses. We review here the state‐of‐the‐art knowledge of the equilibrium thermodynamics of gases dissolved in polymers. The published data are presented and analyzed. Also, we review the latcst theories and predictive correlations for gas solubility in polymers.
Transition behavior and phase segregation in TDI polyurethanes
Authors: Schneider N. S. , Sung C. S. Paik
Published: December 2004

Prior studies of two series of segmented polyurethanes based on 2, 4 toluene cliisocyanate (2, 4 TDI) or 2, 8 TDI, butanediol, and a 1000 molecular weight polytetramethyleneoxide (PTMO‐1000) soft segment revealed a rapid increase in soft segment glass transition temperature (Tg) with increasing urethane content in the 2, 4 TDI series. The change in Tg couldbe correlated with estimates of hard segment‐soft segment phase mixing obtained by infrared analysis of the urethane NH and carbonyl bands. In the present paper, the infrared data have been reevaluated using improved procedures for resolving the carbonyl band into H‐bonded and nonbonded components, and the relation between the estimated extent of phase mixing and Tg has been reexamined. The transition behavior in an extensive series of related polymers has also been determined, including 2, 4 TDI arid 2, 6 TDI samples with PTMO2000 as well as polybutyleneadipate (PBA‐1000 and PBA‐2000) soft segments. The results indicate the effectiveness, of increased soft segment molecular weight in promoting phase segregation, imply that much greater phase mixing occurs in polyester than polyether samples, suggest that anchoring the ends of the soft segments has only a small effect on Tg, and provide some evidence that H‐bonding not only increases Tg but can also impede soft segment crystallization.
A water‐soluble, reciprocity‐law‐failing photoresist
Authors: Akagi Motoo , Nonogaki Saburo , Kohashi Takahiro , Oba Yoichi , Oikawa Mitsuru , Tomita Yoshifumi
Published: December 2004

For the purpose of obtaining a water‐soluble, reciprocity‐law‐failing photoresist, a study was made on the photo‐crosslinking properties of various systems composed of water‐soluble polymers and bisazides. Reciprocity‐law‐failing photoresists are suitable for use in the fabrication of black matrix color picture tubes without any alteration in the shadow mask. As a result, a system containing polyvinylpyrrolidone, polyacrylamide, and 4, 4′‐diazidostilbene‐2, 2′‐disulfonic acid disodium salt was found to show a significant reciprocity‐law‐failing property in the range of light intensity used practically in black matrix fabrication. The mechanism of the photo‐cresslinking reaction of this photoresist was investigated. It is suggested that the bisazide decomposes to liberate a reactive dinitrene intermediate. This photodecomposition was found to proceed reciprocally. The nitrene reacts with polymer molecules to form a water‐insoluble three dimensional network. If, however, oxygen is present, this crosslinking reaction is inhibited by a preferential reaction between dinitrene and oxygen. By this oxygen effect, this photoresist reveals significant reciprocity‐law‐failing characteristics.
Three dimensional behavior of negative electron resists
Authors: Heidenreich R. D. , Kammlott G. W.
Published: December 2004

It is illustrated experimentally that swelling and deformation of narrow lines (width < 1 μm) is an important limitation on the fidelity and transverse resolution of negative electron resists. The thickness response curve developed for negative resists is discussed and the effect of feature size is introduced through the experimental parameter D, the rigid gel dose, or the dose required to initiate a free standing line of width < 0.2 μm. The transition from line to area exposure is discussed and the effect of substrate backscatter or transverse resolution in gratings is calculated. The observed resolution is 3‐5 times the calculated value from swelling and deformation during development.