bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recycling of thermoplastic waste: Phase equilibrium in polystyrene‐PVC‐polyolefin solvent systems
Authors: Sperber R. J. , Rosen S. L. 
Published: December 2004

AbstractThe 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

AbstractThe 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

AbstractTensile 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

AbstractConstitutive 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

AbstractExperimental 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

AbstractPolyphenylene 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

AbstractThe 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

AbstractThe 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

AbstractIncompatible 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

AbstractStringent 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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractMultilayer 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

AbstractAlmost 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

AbstractThe 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

AbstractPolyphenylene 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

AbstractA 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.