bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas permeation and viscoelastic deformation of prepregs in composite manufacturing processes
Authors: Nam J.‐D. , Seferis J. C. , Kim S.‐W. , Lee K.‐J. 
Published: December 2004

AbstractGas permeation and creep deformation of a commercial prepreg, which exhibits viscoelastic characteristics, were investigated as a function of time, temperature, and consolidation pressure. Experiments using a prepreg stack demonstrated that the material exhibited a linear viscoelastic bulk deformation under vacuum/autoclave pressure and furthermore, the in‐plane gas flow exhibited non‐Darcian flow behavior with a permeation hysteresis. This behavior was viewed and analyzed by two viscoelastic relaxation processes: (1) bulk dimensional relaxation, and (2) microscopic pore structure rearrangement. A modified standard linear solid (SLS) viscoelastic model was used to interpret the creep compliance and dynamic gas permeability utilizing two independent relaxation parameters. By visual investigation of pore sizes and their distribution, air permeation was found to take place mostly through the interlaminar porosity network for the prepreg system examined.
Development of an electrically conductive fiber reinforced plastic pipe
Authors: Pang Su‐Seng , Van Beek Gerald A. , Lea Richard H. 
Published: December 2004

AbstractFiber‐reinforced plastic (FRP) pipe has much lower density and better corrosion resistance characteristics than currently used alloy pipe, but it generally does not conduct electricity as well as steel pipe. In this study, an FRP pipe was made conductive by doping the inner liner vinyl ester resin with milled carbon fibers. The joints were also made conductive using the same resin, thus allowing the pipe to be electrically grounded. The result was a pipe having a surface resistivity of less than 125 Ω/□ using current manufacturing processes.
Microhardness of carbon fiber reinforced epoxy and thermoplastic polyimide composites
Authors: Paplham W. P. , Seferis J. C. , BaltáCalleja F. J. , Zachmann H. G. 
Published: December 2004

AbstractWe have examined the micro indentation hardness of a series of carbon fiber reinforced epoxy and thermoplastic polyimide (TPI) composites. In the epoxy systems, the influence of Nylon particles was studied. The effect of crystallization of the thermoplastic polyimide upon the microhardness values of the resin was also investigated. The microstructure of the TPI‐composites was characterized by X‐ray diffraction. The results show that the addition of carbon fibers to the neat resins greatly increases the microhardness and thus the yield stress of the composite. The value of the microhardness technique is highlighted in emphasizing the heterogeneity of the CFRC.
Estimation of molecular weight distribution of poly(vinylpyrrolidone) from diaphragm‐cell diffusion measurements
Authors: Comelli Fabio , Francesconi Romolo , Lanzi Eugenio 
Published: December 2004

AbstractViscometry, gel permeation chromatography (GPC) and diffusion measurements on three samples of poly(vinylpyrrolidone) (PVP) were made. The diffusion measurements were carried out by means of a Stokes cell. An equation with five parameters was derived, linking the difference in PVP amount between the two compartments of the cell to the time of the experiment: three parameters are related to the diffusional behavior of the macromolecules and the other two define the molecular weight distribution (the Tung expression has been chosen). A least‐squares procedure allowed us to obtain the five parameters and the calculated weight average molecular weights agree with the ones evaluated by viscometry and GPC. The ratio Mw/Mn (heterogeneity of the polymer) calculated from the parameter z of the Tung expression is very different from the one obtained from GPC.
Dielectric behavior of polystyrene foam at microwave frequency
Authors: Bandyopadhyay Pranab C. , Chaki Tapan K. , Srivastava Srinath , Sanyal Gitindra S. 
Published: December 2004

AbstractPolystyrene foams have been generated and fabricated into differently shaped structures', by change of steaming period under constant impregnation time and solvent‐nonsolvent composition. Optical photomicrographs of samples both plain and wax‐copper‐coated reveal uniform appearance, distinct grain‐boundaries, and random cell size distribution. Dielectric measurements have been made on test specimens cut according to wave‐guide size at 9.375 GHz X‐band microwave frequency by short‐circuited wave‐guide method of Smith and Hippel modified by Dakin and Works. Dielectric constants are linear, on direct and semi‐log scales in bulk‐density and volume‐fraction, obeying Weiner's inequalities. Formulae of Landau‐Lifshitz, Beer, Maxwell‐Wagner, Odelevsky, etc. have been tried. Data fit best with the logarithmic law of Lichtenecker and Rother. Specific polarization is also a true function of density. Dielectric constant vs bulk‐density plots of foams resemble dielectric‐constant vs fractional‐density plots based on the theoretical derivation by Smith for polystyrene compacts, signifying that compacts containing closely‐spaced oblong‐spherical particles arc physically similar to foams having spherical gas inclusions in plastic structures. Tan δ lying in the range 0.002–0.0038 results from conformational polarization (β‐relaxation at room‐temperature for wide‐angle torsional oscillations of side‐groups with co‐operative motion from wriggling chains). It is therefore possible for low‐loss foam dielectrics suitable for micro‐wave applications to be made by this method.
Lithographic technique using radiation‐induced grafting of acrylic acid into poly(methyl methacrylate) films
Authors: Gazard M. , Duchesne C. , Dubois J. C. , Chapiro A. 
Published: December 2004

AbstractA lithographic process is described which increases the sensitivity of polymers to electron beam irradiation. The free radicals and peroxides produced in a film of polymer by irradiation are used to initiate the grafting of a monomer to form a graft copolymer, the solubility of which may be higher or lower than that of the initial polymer. Acrylic acid has been grafted into poly(methyl methacrylate) films to produce a copolymer which is insoluble in the solvents of PMMA. The sensitivity of this negative system depends on the conditions of grafting and on the conditions of development. A sensitivity of 2.8 10−8 C.cm−2 at 20 keV has been obtained.
Limiting regimes of deformation of polymers
Authors: Vinogradov G. V. 
Published: December 2004

AbstractThe relaxation transition of polymers under the influence of deformation from the fluid to the forced high‐elastic (rubbery) and leathery states has been studied. It has been shown that the investigation of the polymers in question under the conditions of uniaxial extension allows one to estimate the properties of polymers at deformation rates exceeding by 4‐5 decades the rates of deformation at which simple shear can be realized. A set of critical parameters has been found for the polymers investigated which determines the regimes of their transition from the fluid to the forced rubbery and leathery states and also their fracture properties. These parameters are subdivided into two groups. The parameters of the first group refer to critical values of stress and deformation. They are invariant to temperature and molecular mass. For different polymer‐homologous series the critical stresses vary by more than 10‐20 times; as regards the values of strains, they vary by more than several times. The parameters of the second group define the rates of strain which bear a simple relation to the initial viscosity and can be changed within many decades. This determines the success of the procedure of reduction of fracture properties to temperature and molecular mass.
Competitive equilibria in miscible polymer blends and low molecular weight analogues: A fourier transform infrared study
Authors: Garton Andrew 
Published: December 2004

AbstractThe relative magnitudes of specific interactions are compared by setting up competitive equilibria in mixed solvent systems. The positions of the equilibria are determined spectroscopically by resolving the overlapping absorptions of the two solvation states. This technique is applied to the study of interactions between polyesters (or model compounds) and a variety of solvents which mimic possible interacting centers in halogenated polymers. Using the same technique of resolving overlapping bands, it is also demonstrated that in a miscible blend of polycaprolactone and Phenox (a polyhydroxyether of bisphenol A) only a relatively small proportion of the carbonyl groups of polycaprolactone are involved in specific interactions with the Phenoxy.
Fourier transform infrared studies of poly(vinyl chloride) blends with ethylene Co‐ and terpolymers
Authors: Iskandar M. , Tran C. , Robeson L. M. , McGrath J. E. 
Published: December 2004

AbstractThe miscibility of poly(vinyl chloride) (PVC) with various ethylene copolymers and terpolymers were investigated using FT‐IR spectroscopy. All blends reported were 50/50 by weight. In blends of PVC with ethylene/dimethyl acrylamide copolymer (E/DMA), frequency shifts were observed in the amide carbonyl (proton acceptor) and the α‐hydrogen of PVC (proton donor) characteristic bands. In blends of PVC with ethylene/ethyl acrylate/carbon monoxide terpolymer (E/EA/CO), both the ester carbonyl and the ketone carbonyl characteristic frequencies showed mutual shifts and appeared as if they merged together. Small frequency shifts were also observed in the α‐hydrogen of PVC characteristic bands. In blends of PVC with ethylene/vinyl acetate/carbon monoxide terpolymer (E/VA/CO), the ester carbonyl frequency showed a shift while that of the ketone carbonyl was essentially unchanged. On the other hand, in PVC blends with ethylene/vinyl acetate copolymer (E/VA), the ester CO frequency did not show any shift, which is consistent with their observed immiscibility. Thus, it is clear that incorporating a ketone CO in ethylene/ester copolymers to form the corresponding terpolymers enhances their miscibility with PVC as earlier proposed on the basis of dynamic mechanical studies. Similar results were shown for blends of PVC with ethylene/2 ethyl hexyl acrylate/carbon monoxide terpolymer (E/2EHA/CO). Frequency shifts imply specific interactions which suggest polymer‐polyer miscibility on a molecular scale.
Characterization of fast‐cure resins for reaction injection molding
Authors: Osinski J. S. 
Published: December 2004

AbstractThe interest in reaction injection molding of urethane and non‐urethane resins has generated a need for a greater understanding of the molding behavior of these reactive systems. The kinetics and rheology of a given resin must therefore be well characterized in order to understand and model the molding process. This often requires semi‐empirical correlations rather than strict theoretical considerations. A method of fully characterizing such systems by combining adiabatic reactor and IR studies with viscometer data is therefore described. This results in time‐temperature‐conversion‐viscosity correlations which can be directly utilized in molding studies. Such methods are applied to polyurethane and epoxy systems in the work presented here. It was found that very different activation energies are obtained for the same epoxy‐amine system using different kinetic characterization techniques.
The effect of pressure and temperature on time‐dependent changes in graphite/epoxy composites below the glass transition
Authors: Mijović Jovan , Liang R. C. 
Published: December 2004

AbstractEffects of pressure and temperature on time‐dependent changes in physical/mechanical properties of graphite/epoxy composites were investigated. Samples were cut from the eight‐ply‐thick laminates of commercially used composites, post‐cured, and then quenched to environments of various temperature and pressure. Time‐dependent changes in their properties were analyzed by thermal and thermomechanical (dynamic mechanical) measurements. An increase in the glass‐transition temperature was found to occur as a function of time. The rate of this process was enhanced by an increase in temperature and/or a decrease in pressure. An explanation was offered in terms of types and mechanisms of molecular events that occur in the glassy state. Time dependent decrease in free volume (and enthalpy) takes place but is not the sole mechanism responsible for the observed increase in Tg. After a certain period of time (which depends on T and P of the environment), additional crosslinking appears to take place.
Dynamic X‐ray diffraction studies of spherulitic poly‐alpha‐olefins in relation to the assignments of alpha and beta mechanical dispersions
Authors: Kawai Hiromichi , Hashimoto Takeji , Suehiro Shoji , Fujita Ken‐Ich 
Published: December 2004

AbstractThe dynamic tensile deformation mechanism of spherulitic poly‐alpha‐olefins, high‐density polyethylene, isotactic polypropylene, and isotactic polybutene‐1, was investigated by dynamic X‐ray diffraction at various temperatures and frequencies in order to assign the α and β mechanical dispersions explicitly. The uniaxial orientation distribution function qj(ζj, 0) of thej‐th crystal plane and its dynamic response Δqj′(ζj, 0) in‐phase with dynamic strain were observed for several crystal planes, and then the orientation distribution function ω(§, 0, η) of crystallites (crystal grains) and its dynamic response Δω′(§, 0, η), also in‐phase with the dynamic strain, were determined by a mathematical transformation procedure proposed by Roe and Krigbaum on the basis of the Legendre addition theorem. The temperature and frequency dependences of Δω′(§, 0, η) were analyzed in terms of a spherulite deformation model combining affine orientation of crystal lamellae with several types of preferential reorientation of the crystal grains within the orienting lamellae. The following assignments are made: (1) the a mechanical dispersion must be assigned to the dynamic orientation dispersions of crystal grains within lamellae involving two types of preferential rotations of the grains associated with lamellar detwisting mostly in the equatorial zone of uniaxially deformed spherulites and with lamellar tilting mostly in the polar zone of the spherulites. Both processes are intralamellar grain‐boundary phenomena, and the former process of lamellar detwisting is hardly activated for polypropylene and polybutene‐1 spherulites in contrast to polyethylene spherulites. (2) The β mechanical dispersion must be assigned to the dynamic orientation dispersion of the crystal lamellae behaving as rigid bodies unaccompanied by reorientation of crystal grains within the orienting lamellae. This process is an interlamellar grain‐boundary phenomenon.
Orientation studies of poly(ethylene terephthalate)
Authors: Jabarin Saleh A. 
Published: December 2004

AbstractThis paper discusses the results of a detailed study of the relationships between molecular orientation, physical properties, and molecular weight of polyethylene terephthalate (PET), and their dependence on orientation variables. The molecular weight range of the samples used in this study included weight average molecular weights,Mw, between 29,000 and 65,000 which correspond to inherent viscosities, I.V., from 0.5 to 0.9. The orientation temperatures investigated were between 80 and 120°C. The extent of molecular ordering imparted by the orientation process was studied by birefringence, density, light scattering, and depolarized light intensity techniques. The results show that the degree of molecular orientation and the physical properties are strongly dependent on strain rate, extension ratio, molecular weight, and orientation temperature. The mechanical and transport properties, of PET are directly related to the degree of orientation as measured by birefringence. It is found that at a comparable level of orientation, the mechanical properties are also dependent on molecular weight, whereas the transport properties are independent of molecular weight. The degree of orientation varies according to the molecular weight of PET and stretch temperature. It is shown that for the same stretch ratio and stretch speed, the birefringence decreases with increasing stretch temperature. The light scattering results indicate that biaxial orientation of PET can lead to strain‐induced crystallization. The amount and form of the crystalline structures are dependent on strain rate and orientation temperature.
Rheological and mechanical properties of ternary blends of linear‐low‐density polyethylene/polypropylene/ethylene‐propylene block polymers
Authors: Dumoulin M. M. , Farha C. , Utracki L. A. 
Published: December 2004

AbstractThe effect of addition of an ethylene‐propylene block polymer on rheological and mechanical properties of a linear‐low‐density polyethylene/polypropylene blend was examined. The samples were prepared by melt blending in a twin‐screw extruder followed by injection molding. The single‐, two‐ and three‐component systems were treated the same way. The mechanical behavior of the blends was evaluated by means of tensile, and flexural, tests at 23 and −40°C. The capillary, elongational, and dynamic‐flow measurements were performed at 190°C.
Polymer structure: The key to process‐property control
Authors: Samuels Robert J. 
Published: December 2004

AbstractThe key to process‐property control is a knowledge of the structural state of the product desired and the availability of methods to economically characterize the structural states produced. The present paper demonstrates that these goals are attainable. Examples illustrate both that the equivalent state concept leads directly to the use of structural state functions as the pivotal criteria around which property and process data can be organized, and that this approach is appropriate to many fabrication processes, including films, fibers, and moldings. Further, the development of process‐structure‐property correlations is seen to lead to new processes and the development of structures having unique properties.
The effects of degree of mixing and concentration of carbon black on the tensile properties of filled elastomers
Authors: Lee Michael C. H. 
Published: December 2004

AbstractBased on the concept of entropy of mixing, a new method for determining the degree of mixing of the filler in a polymer matrix has been established. The measurement used in this method is based on a new variable, the effective volume fraction of the filler, ϕ′, which is a function of the mixing index, A, and the volume fraction of the filler, ϕ. The mixing index can be determined from the tensile modulus data of filled elastomers. Excellent agreement is obtained between the mixing index and the dispersion of the filler as determined by a morphological study of cryogenically fractured surfaces of filled elastomers. Using the new variable, the effective volume fraction of the filler, useful relationships for the tensile modulus and the ultimate stretch ratio of filled elastomer have been established. Experimental data confirm that these relationships can well describe the effects of concentration and degree of mixing on the two tensile properties of filled elastomers.
A new semicrystalline reinforced polyamide engineering thermoplastic
Authors: Onder Kemal , Chen Augustin T. 
Published: December 2004

AbstractA new rapidly crystallizing aromatic‐aliphatic polyamide has been developed by reacting 4,4′‐methylene bis(phenylisocyanate) (MDI) with aliphatic dicarboxylic acids. The polymer has a Tg of 130°C and Tm, of 290°C. Glass reinforced resin shows better flexural creep resistance at high stress levels (3000 psi) at elevated temperatures (75°C) than most reinforced semicrystalline commercial polymers i.e., nylons, thermoplastic polyesters and acetal because of its high Tg. Glass reinforced polyamide can be injection molded on conventional equipment to afford flexural moduli in excess of 1,000,000 psi and HDT's as high as 250°C at 264 psi. Because of the high level of crystallinity these parts will not dissolve or swell in most organic solvents and this aromatic aliphatic polyamide is also far less sensitive to moisture than commercial nylons.
Temperature measurements of polymer melts in the heating barrel during injection molding. Part 2: Three‐dimensional temperature distribution in the reservoir
Authors: Amano O. , Utsugi S. 
Published: December 2004

AbstractA new method has been developed to measure the three‐dimensional temperature distribution of polymer melts in the reservoir of the heating barrel in the dynamic state. The procedure involves the use of a small‐sheathed thermocouple in the nozzle of the machine. The tip of the thermocouple can be varied in depth from the surface to the center of the nozzle. The polymer melt of a shot is found to have a three‐dimensional temperature distribution dependent on the geometry of the screw and the order of shot. These results reflect clearly the thermal histories of the polymer melt in the channel of the screw during plastication and conveyance, and indicate part of the dynamics of injection molding. Further, these measurements contribute to optimization of the design for the screw and the process conditions.
Monitoring cure in sheet molding compound processing
Authors: Castro J. M. , Straus E. J. 
Published: December 2004

AbstractDuring the sheet molding compound (SMC) compression molding process, a premeasured polymer charge is placed between the heated halves of a mold which are then brought together to squeeze the polymer and fill the mold, after which pressure is maintained while the part cures. The cure stage constitutes the larger part of the molding cycle and thus affords the largest potential for cycle time reduction. In general, cure times in SMC processing are set longer than necessary, since the inherent material and process variation make it difficult to predict cure times with more than 10 to 20% accuracy. Accurate methods to detect the end of cure would be very beneficial and would permit opening the mold as soon as the material has cured, avoiding unnecessary waste of time. In this paper, several techniques that show promise for monitoring the state of cure are reviewed and experimental results given. Their relative advantages and accuracies are compared. In particular, the use of linear variable displacement transducers, pressure transducers, and thermocouples is discussed. We also show how the measurements compare to theoretical predictions of the state of cure.
Polyketone and complex formation of some halatopolymers
Authors: Ibidapo T. Adesanya 
Published: December 2004

AbstractThe possibility of a number of halatopolymers forming complexes with pyridine and their ability to produce ketones by pyrolytic decarboxylation have been investigated. Of all the halatopolymer‐forming divalent metal (i.e., Mg2+, Ca2+, Ba2+, Zn2+, Cd2+, Mn2+, and Pb2+) dicarboxylates (i.e., suberate, sebacate, dodecanedioate, and terephthalate) investigated only Cd2+ yielded polyalkylene ketone on pyrolysis and formed complexes with pyridine. The polyalkylene ketones were infusible, and no solvents were found for them which suggests a cross‐linked molecular structure. Complexes formed by the cadmium aliphatic dicarboxylates were unstable but highly viscous in solution. Cadmium‐pyridine terephthalate complexes were on the contrary very stable.