bluuebunny/crossref_metadata_2025 huggingface dataset:
Victrex® poly(ethersulfone) (PES) and Victrex® poly(etheretherketone) (PEEK)
Authors: Searle O. B. , Pfeiffer R. H.
Published: December 2004

Properties of two high performance engineering thermoplastics, amorphous polyethersulfone (PES) and semicrystalline polyetheretherketone (PEEK), are discussed. Both resins can be processed by conventional techniques, compounded with high performance fibers, and have high service temperature (up to 300°C). Due to the amorphous character PES can be dissolved and spray coated into metals.
Conductive composites past, present, and future
Authors: Crossman R. A.
Published: December 2004

Conductivity of plastics and polymeric composites is reviewed. The use of various conductivity‐enhancing fillers, such as graphite, metallized glass, or stainless steel fibers are discussed. Properties of composites containing rapid‐solidified aluminum flakes are of particular interest.
Optimal thermal design of injection molds for filled thermosets
Authors: Barone M. R. , Caulk D. A.
Published: December 2004

Since the cure rate of injection molded thermosets is usually very sensitive to cavity surface temperature, spatial variations in these temperatures can lengthen the necessary cure time for the entire part and cause distortion and residual stress in the molded article. This problem is addressed in the present paper by combining an optimization algorithm with a quasi‐steady heat conduction analysis in the mold to determine the heating line positions and operating temperatures that minimize the spatial variation in cavity surface temperature. The method is applied to an example mold for a flat panel of uniform thickness, using two different gate locations. At a one‐minute cycle, the optimal designs for each gate location dramatically reduce the variation in cavity surface temperature compared with corresponding results using a conventional heating system. These results are made more significant by the fact that the optimal designs use considerably fewer heating lines. In spite of their simplicity, the optimal designs still have enough flexibility to adjust to a changing cycle without sacrificing uniformity in cavity surface temperature.
Binders for jute‐reinforced unsaturated polyester resin
Authors: Semsarzadeh Mohammad A. , Amiri Davod
Published: December 2004

Reinforcement of polyester resin with jute cloth under constant load is studied, The pretreatment of jute cloth with tetrahydrofuran and the effect of binding properties of poly(vinyl acetate) and acrylic acid and their effect on the impact, tensile, and water absorptions of jute cloth polyester composites are reported and their chemical reactions are discussed.
Exit pressure effects in capillary die data
Authors: Carreau Pierre J. , Choplin Lionel , Clermont Jean‐Robert
Published: December 2004

The exit flow from a capillary is analyzed with the help of macroscopic mechanical energy and momentum balances. The analysis shows that primary normal stress differences cannot be determined from the exit pressures under the assumption that the flow is viscometric down to the exit. This assumption and the second one (made by Han [9]) that both slit and capillary exit pressures are the same would lead to unacceptable results. Published exit pressure data for polyethylene melts are shown to be unreliable because of large hole‐pressure errors in the pressure measurements. Pressure profiles obtained with a thin tube technique for the flow of a poly(isobutylene) solution indicate that the flow does not remain fully developed near the exit. Moreover, it is shown that for this polymer solution the excess viscous dissipation at the exit contributes to approximately 90 percent of the exit pressure.
The effect of powder particle fusion on the mechanical properties of ultra‐high molecular weight polyethylene
Authors: Zachariades Anagnostis E.
Published: December 2004

Rheo‐optical and mechanical property studies with compression molded ultra‐high molecular weight polyethylene specimens at different temperatures indicate that their mechanical performance is dependent on the degree of fusion of the powder particles during compression and can be enhanced by heating the polymer powder at temperatures above 220°C. Although the mechanical performance of the compression molded specimens can be improved further by solid‐state drawing at a draw ratio 5, the anisotropic morphologies from molded specimen above 220°C have higher initial slope of stress to elongation, strength to break, and an outstanding elastic recovery in compreision to the compression molded specimens at 180°C.
Effect of surface treatments on rheological, mechanical and magnetic properties of ferrite‐filled polymeric systems
Authors: Saini D. R. , Shenoy A. V. , Nadkarni V. M.
Published: December 2004

Experimental data on the effect of the type and amount of surface treating agents on the rheological and mechanical properties of the ferrite‐filled styrene‐isoprene‐styrene systems at high levels of loading has been presented. The viscosities of the treated ferrite systems are found to be lower than the untreated systems, with the extent in reduction depending upon the type and amount of surface treatment. It is also found that surface treatment decreases the tensile strength and percentage elongation in the present filler‐matrix system, and the extent of the decrease in viscosity as well as mechanical properties is more in the presence of titanates than with silanes.
Prediction of axial and off‐axis yield behavior of lsotactic polypropylene film from structural state parameters
Authors: Linder Barbara E. , Samuels Robert J.
Published: December 2004

Since only minor structural rearrangements occur prior to yielding, the axial and off‐axis yield stress of a polymer sample is expected to relate to the initial structural state of the material. Samples of uniaxially oriented isotactic polypropylene films with known structural state parameters have been deformed under a uniaxial tensile stress at deformation rates of 20 percent and 100 percent per minute over an angular range from 0 to 90 degrees to the fabrication direction. The axial yield stress data was found to correlate with the initial noncrystalline orientation state of the undeformed sample. The axial and offaxis yield stress data was fit to the Hill equation derived for the application of a uniaxial tensile stress. The experimentally determined coefficients from the best fit of the yield stress data to the Hill equation were related to the measured structural state parameters. These correlations allow prediction of the yield stress of an anisotropic film at any angle to the film symmetry axis from knowledge of the measured structural state parameters alone.
Shear and extensional flow of reinforced plastics in injection molding. I. Effects of temperature and shear rate with bulk molding compound
Authors: Gibson A. G. , Williamson G. A.
Published: December 2004

Capillary flow studies on bulk molding compound (BMC) using an instrumented injection‐molding machine are reported. The significance of extensional flow effects with fiber‐reinforced materials is emphasized. The extensional flow behavior in converging dies is modeled, and a means of evaluating both extensional and shear viscosity from capillary flow data is proposed. Methods of correcting results for the effect of deformation heating are discussed. The shear and extensional flow behavior of BMC in the temperature region 18 to 58°C can be fitted to a simplified Arrhenius Law.
Temperature dependence of the thermal expansivity in polymer
Authors: Cho Bongkee
Published: December 2004

The effects of temperature on the specific volumes and thermal expansivities for a range of amorphous polymers, above and below the glass transition temperature, are treated on the basis of the physical properties of polymers. The results are found to be in good agreement with observed data. The analysis of the results shows that the temperature derivative of the zeropressure thermal expansivity of the liquid polymer increases with increasing temperature. The change in the thermal expansivity, Δα = αOL − αOG, decreases with increasing temperature.
Polyvinyl alcohol‐copper II complex: Characterization and practical applications
Authors: Godard P. , Wertz J. L. , Biebuyck J. J. , Mercier J. P.
Published: December 2004

A method to obtain microscopic and macroscopic coatings with improved resistance to debonding is described. The procedure, based on polymer‐metal complexes, involved the adsorption on inorganic substrates of a poly(vinyl alcohol)‐copper II chelate that is also able to catalyze the polymerization of monomers or prepolymers with grafting. The molecular structure of the complex, its adsorption on inorganic surfaces, and the mechanism of the polymerization induced by the supported catalyst are summarized. Much emphasis is placed on application of this technology to the realization of encapsulated filler and pigment and of coatings with improved adherence and solvent resistance. In the field of composite materials, it is demonstrated from several examples that the encapsulation of the filler can be a way to block chemical interactions between filler and matrix, to promote filler dispersion, and to improve mechanical properties.
Analysis of molecular orientation and internal stresses in extruded plastic sheets
Authors: Chan T. W. D. , Lee L. J.
Published: December 2004

The development of molecular orientation and internal stresses in extruded sheet made of polypropylene was analyzed, and their correlations to operating conditions such as draw ratio, cooling rate, die temperature, melt temperature, and die gap opening were studied. Measurements of attenuated‐total‐reflectance infrared dichroic ratio for the surface molecular orientation, birefringence for the orientation stress distribution in the thickness direction, and free shrinkage ratio for the overall frozen‐in stresses were carried out to determine the amount of orientation stresses in the extruded samples. As expected, the overall orientation stress depends strongly on draw ratio, while higher melt temperature reduces the overall orientation. It was found that faster cooling rates and lower die temperatures cause surface orientation stresses to increase as the core orientation stresses remain almost unchanged.
Use of the frequency dependence of the impedance to monitor viscosity during cure
Authors: Kranbuehl D. , Delos S. , Hoff M. , Haverty P. , Freeman W. , Hoffman R. , Godfrey J.
Published: December 2004

The ability to conveniently and continuously measure the processing properties of polymer resins is important both to the resin supplier and to the fabricator. Frequency dependent electromagnetic sensors (FDEMS) provide an in‐situ technique for continuous measurement of the resin's rheological changes both in a laboratory press and in manufacturing tools in an autoclave. In this paper the frequency dependence of ϵ*(w) is used to quantitatively monitor the viscosity for a tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) amine epoxy, to quantitatively monitor the viscosity during processing In a styrene‐polyester resin, and to monitor the cure process in an autoclave during cure of a high temperature polyimide‐graphite prepreg. In addition, the technique is used to measure the viscosity at various ply positions in a thick TGDDM graphite epoxy laminate during processing in an autoclave.
Isothermal and temperature programmed kinetic studies of thermosets
Authors: González‐Romero V. M. , Casillas N.
Published: December 2004

Differential Scanning Calorimetry (DSC) is a popular method for the characterization of the cure kinetics of thermosetting materials. The experiments may be carried out under isothermal or temperature program modes. Several authors have pointed out the fact that the kinetic rate expressions for non‐isothermal experiments must be different from the isothermal ones; however, this fact has been neglected in practice. In this work, we present a kinetic characterization of a thermosetting system using a phenomenological model for the reaction rate expression and DSC data from isothermal and non‐isothermal experiments. In general, thermosetting materials exhibit the vitrification phenomenon which stops the reaction before complete conversion is achieved. Vitrification is taken into account in both Isothermal and temperature programmed experiments.
Evaluation of dielectric cure models for an epoxy‐amine resin system
Authors: Lane John W. , Khattak Rangin K. , Dusi Mark R.
Published: December 2004

The parallel‐plate test fixture on a Rheometrics viscometer was electrically isolated so that the rheological and dielectric properties of a thermoset polymer system could be simultaneously measured. This enabled the relationship between the dielectric properties and the rheological properties to be directly examined. A close relationship was established between the dielectric properties (dipole relaxation time and specific conductivity) and the pre‐gelation bulk viscosity. This relationship suggested that models similar in form to those used to describe the change in viscosity might be used to describe the changing dielectric properties. The limitations and advantages of two such models, which attempt to describe the time‐temperature behavior of the dielectric properties, were then tested for use with a typical aerospace epoxy resin system.
Curing of polyimides
Authors: Feger Claudius
Published: December 2004

The imidization of films of the polyamic acid obtained from reaction of pyromellitic dianhydride (PMDA) with oxydianiline (ODA) was studied by dynamic mechanical thermal analysis (with the Polymer Labs DMTA), Two process regions are observed. The first process is characterized by decomplexation of the NMP/polyamic acid complex, plasticization, and imidization. The heating rate determines the character of the first process. At high temperatures (above 300°C) the second process becomes apparent. It is connected to the increase in chain mobility at these temperatures which allow molecular packing processes (densification, ordering) to occur. The ordering leads to an increase of the storage modulus. The particular transition temperature increases with annealing time.
Reducing residual stresses in molded parts
Authors: Liou Ming J. , Suh Nam P.
Published: December 2004

Means of reducing the flow‐induced residual stresses in injection molded parts through optimization of the thermal history of the process are presented. An approach through the use of a passive insulation layer with low thermal inertia on the cavity surface was investigated. The passive insulation layer prevents the polymer melt from freezing during mold filling and allows the flow‐induced stresses to relax after the filling. The criteria for the optimal thermal properties and the required thickness of the layer are presented. A numerical simulation model of non‐isothermal filling and cooling of viscoelastic materials was also used to understand the molding process and to evaluate this approach. This model predicts the stress development and relaxation in the molding cycle. Both simulation and experimental results show that the final stresses in the molded parts can be reduced significantly with the use of an insulation layer. This technique can also be applied to other molding or forming processes in order to decouple the material flow and cooling process for minimum residual stresses in the molded parts.
Flow of a temperature dependent power‐law model fluid between parallel plates: An approximation for flow in a screw extruder
Authors: Lindt J. Thomas
Published: December 2004

This paper formulates concisely the problem of fully developed flow of a temperature dependent power‐law fluid between parallel plates. An exact solution, in the absence of pressure gradients, is developed. The method has been validated by a comparison with an independent numerical solution. This work is applicable to melt transport in shallow partly filled screw channels, drag flow regimes in the metering zone of a screw extruder and, generally, to flows in hydrodynamically thin layers associated with negligible pressure gradients. A numerical example is included dealing with the extrusion of polypropylene. A general discussion is given concerning the utility of the new theory. Effects of pressure gradients are included in the discussion.
Impact fracture energy of mineral‐filled polypropylene
Authors: Chen Le‐Shang , Mai Yiu‐Wing , Cotterell Brian
Published: December 2004

The impact fracture energy (Gc) for a polypropylene homopolymer and a copolymer with and without calcium carbonate fillers was measured over a range of temperatures between −40°C and 40°C using fracture mechanics principles. The fillers studied were Omyacarb (∼2.7 μm) and Winnofil (∼75 nm) and 10% by weight was added to the matrix material. These fillers did not have any appreciable effect on Gc of the copolymer‐based composites. However, the Omyacarb fillers improved Gc of the homopolymer at low temperatures (⩽20°C) due to enhanced microplastic flow as observed on the fracture surfaces. The fillers increased the stiffness of both the homopolymer and copolymer. It would appear that up to 10% of cheap calcium carbonate fillers could be added to the more expensive polypropylene to reduce the production cost without any significant loss of impact fracture energy.
Characterization of liquid crystalline polyester polycarbonate blends
Authors: Malik Tariq M. , Carreau Pierre J. , Chapleau Nathalie
Published: December 2004

Mechanical and rheological properties of blends of a thermotropic liquid crystalline polyester with a polycarbonate have been investigated. The blends are fibrillar in character and exhibit great hardness and toughness due to high degree of molecular orientation which develops during the melt blending and processing steps. Increases of the Young modulus by 100 percent are observed for blends containing only 10 percent of liquid crystalline polymer, LCP. Time‐dependent behavior of the blends was investigated by performing solid state relaxation measurements and the relaxation modulus was also found to increase by the addition of LCP. The effect is relatively small in the glassy zone of viscoelastic response, but increases through the transition and viscous flow regions. The melt viscosity of the polycarbonate is slightly shear thinning whereas that of the unblended LCP increases rapidly with decreasing shear rate at low shear rate. This suggests the presence of yield stresses as confirmed by measurements on the Rheometics RSR in the stress sweep mode. The melt viscosity of the blends was found to be similar to that of the unblended polycarbonate, but more shear‐thinning and less viscous. Preliminary results of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) are also presented.
Novel positive deep UV resist for KrF excimer laser lithography
Authors: Endo Masayuki , Tani Yoshiyuki , Sasago Masaru , Ogawa Kazufumi , Nomura Noboru
Published: December 2004

A novel positive deep UV resist for KrF excimer laser lithography has been developed. The resist is composed of 1,7‐bis(4‐chlorosulfonyl phenyl)‐4‐diazo‐3,5‐heptanedione as the alkaline dissolution inhibitor and an alkali‐soluble sytrene polymer as the main‐polymer. 1,7‐bis(4‐chlorosulfonyl phenyl)‐4‐diazo‐3,5‐heptanedione has great capability of alkaline dissolution inhibition. High thermal stability and excellent photobleachability at 248 nm of the compound are also characterized. The alkali‐soluble styrene polymer has a high transmittance of 70% in 1.0 μm thickness at 248 nm. The novel positive resist had an excellent property for dissolution kinetics and photobleaching. We achieved high aspect ratio half‐micron pattern fabrication in 1.0 μm thickness using the new resist.
Application of silicon polymer as positive photosensitive material
Authors: Aoai Toshiaki , Umehara Akira , Kamiya Akihiko , Matsuda Nobuaki , Aotani Yoshimasa
Published: December 2004

A new positive‐working photosensitive system of silicon polymer, containing silylether groups in the main chain and a photo‐induced acid precursor was investigated. The silicon polymer is hydrolized by a photogenerated acid and degraded to low molecular weight compounds. Thus the effect of solubility inhibition of the polymer is diminished. The higher photosensitivity of this system as compared with 1,2‐quinone diazide compounds is due to the catalytic reaction of the acid on the hydrolysis of the silicon polymer. The chemical structure around silylether groups in the polymer, in particular more hydrophilic and less steric structures, affects the rate of hydrolysis and thus the photosensitivity. Among various types of photo‐induced acid precursors examined, e.g., s‐triazine and 1,3,4‐oxadiazole compounds substituted by trihalomethyl groups were effective.
A sub‐0.5 μm bilevel lithographic process using the deep‐UV electron‐beam resist p(si‐cms)
Authors: Novembre A. E. , Jurek M. J. , Kornblit A. , Reichmanis E.
Published: December 2004

Optimization of the deep‐UV and electron‐beam lithographic properties of a copolymer of trimethylsilylmethyl methacrylate (SI) and chloromethylstyrene (CMS), P(SI‐CMS), within a weight average molecular weight range of 1.4 to 4.1 × 105 and 90 to 93 mole percent SI composition has been achieved. The solubility behavior of P(SI‐CMS) resist was examined using the Hansen 3‐dimensional solubility parameter model and dissolution rate measurements. Swelling of the resist has been minimized through the identification of a single component developer (2‐propanol) and rinse (water) system. For the material containing 90 mole percent SI (14.9 weight percent Si) and M̄ω = 1.4 × 105, the sensitivity to 248 nm radiation is 65 mJ/cm2 and to electron‐beam exposure is 3.4 μC/cm2 at 20 kV. This material Is applicable to bilevel lithographic processes, and the O2 reactive ion etching (RIE) rate is 16 times slower than standard hard‐baked photoresist. Using a He/O2(60/40) RIE pattern transfer process, 0.4 μm line/space patterns have been resolved in a 1.3 μm bilayer structure for deep‐UV exposures, and 0.25 μm imaging has been demonstrated in a 0.7 μm thick planarizing layer using electron beam irradiation. The loss in linewidth associated with the 0.25 μm process is ∼0.04 μm.
Soluble and optically transparent fluorine‐containing photoreactive polyimide precursors: Spectral sensitization by organic peroxide and organic dye combination
Authors: Omote T. , Koseki K. , Yamaoka T.
Published: December 2004

Photoreactive polyimide precursors involving the hexafluoropropyl group with chain structure have been developed. These polyimide precursors are readily soluble in common organic solvents and optically transparent for light of 365nm wave length (i‐line) similar to aliphatic polyimide precursors. These precursors offer high resolution patterns with aspect ratio of more than 2.0. In these polyimide precursors, the polymers which have a benzophenone segment in the polymer backbone are self‐sensitized, and show interesting photochemical reactions. The authors have been also tried to extend the range of spectral sensitivity of BPDA‐AMHFP toward longer wavelengths (> 436 nm) by the addition of an organic peroxide (BTTB) and a sensitizing dye selected from coumarine, ketocoumarine, xanthen, etc.
High‐Speed fracture mechanics by photography of polypropylene copolymers
Authors: Bramuzzo M.
Published: December 2004

The use of photography applied to stroboscopy in analyzing the processes inherent to the starting and propagation of cracks in materials is a technique which has proved to be of great interest, especially since it enables one to check and “directly” study the evolution of such phenomena. Using fracture mechanics criteria this technique has been applied to the study of the impact behavior of some polypropylene copolymers at different rubber contents obtained either by blending or by synthesis. This technique makes it possible to determine numerous parameters of fracture mechanics, including C.O.D. (crack opening displacement), C.O.A. (crack opening angle), JIc, the plastic work parameter, determined from the resistance curveR, tearing modulus, and crack propagation velocity. Furthermore, under high strain rate conditions, the value taken on by the coefficient “λ” relating theJ‐integral to C.O.D. (1, 2) were checked for those materials using the equationJ= λ. σy · C.O.D., Hayes and Turner (3) and Boyle (4). From analysis of the materials it was possible to note that the synergetic effect of the EP (ethylenepropylene) rubber increased, especially when present at percentages of more than 10 percent. Annealing the materials, on the other hand, produced an increase in fracture toughness for those products having a low rubber content; however it did not have any effect on those with an elevated rubber content (26 percent).
Ultrasonic velocity and attenuation of polymeric solids under oscillatory deformation: Apparatus and preliminary results
Authors: Tanaka A. , Nitta K. , Onogi S.
Published: December 2004

A new apparatus has been constructed in which ultrasonic velocity and attenuation coefficients can be measured under oscillatory deformation. Using this apparatus, dynamic ultrasonic parameters were obtained with sufficient accuracy to investigate plastic deformation directly. It is found that this method has potential as a new tool for the study of solid polymers during deformation.
Evaluation of dynamic density by simultaneous measurement of ultrasonic velocity and elastic modulus under oscillatory deformation
Authors: Nitta K. , Tanaka A.
Published: December 2004

It is proposed that dynamic density can be estimated from simultaneous measurements of ultrasonic velocity and modulus under an oscillatory deformation. An experimental investigation was carried out and a theoretical model applied. Preliminary experiments show that measurement of the dynamic density is a major aid to the study of plastic deformation.
Thermo‐Oxidative aging of a primary lightguide coating in films and dual‐coated fibers
Authors: Simoff D. A. , Chan M. G. , Chapin J. T. , Overton B. J.
Published: December 2004

The thermo‐oxidative aging of a polyether urethane lightguide primary coating has been studied in films and dual‐coated fibers, In films, oxygen absorption is correlated with changes in modulus, yellowness, glass transition temperature, and sample weight. Thermal aging of fibers shows similar trends with regards to coating weight loss and discoloration as those observed with films. In addition, the force to mechanically strip the fiber follows the same patterns of change as the modulus of aged films. For both films and fibers, the time for onset of property changes varies inversely with temperature and can be delayed by the incorporation of an antioxidant.
The dependence of butt fusion bond strength on joining conditions for polyethylene pipe
Authors: Pimputkar S. M.
Published: December 2004

The integrity of a pipeline system is determined by its weakest links. Joints may be such places. Heat fusion is the most common joining method for distribution gas piping. There are procedural, thermal, and mechanical aspects of making fusion joints. Procedural aspects, such as heater calibration and cleanliness, can be assured only by rigorous training and certification of the operators. Thermal and mechanical aspects consist of specifying joining conditions such as the heater temperature, heating time, and joining pressure. In the absence of procedural errors, the strength of a fusion joint should depend on the pipe material, pipe dimensions, and the thermal and mechanical joining conditions.

The measured parameters that are measures of strength are impact energy and location of failure in the tensile impact test. A parameter, termed the joining parameter, was found to characterize the joining conditions. This parameter is a function of bead volume, melt volume at the end of the heating phase, and pipe wall thickness. Of the mechanical test parameters, the impact energy was found to correlate best with the joining parameter.
Properties of post‐cured siloxane networks
Authors: Quan X.
Published: December 2004

Post‐curing of vinyl‐addition cured siloxane networks can take place due to the presence of excess silicon hydride. The reaction of these groups, which leads to increased crosslink density especially at elevated temperatures, can be retarded by treatment with ammonia gas or eliminated by exposure to ethylene gas. There is an interesting correspondence between post‐curing behavior and the gelation process. In both cases, two curing regimes are observed. For low extents of reaction, the mobility of chains is high, even though the post‐curing experiment is performed on samples which have already gelled, and the cure is controlled by reaction kinetics, not by the diffusion of the reactants. At high degrees of cure or post‐cure, both cases behave as crosslinked networks to reduce the probability of interaction between reactants, and the cure is diffusion‐controlled. However, the post‐cured gels do not exhibit ideal network behavior since the last crosslinks formed during post‐curing have a much greater effect on the physical properties than those formed initially. This may be due to the bimodal distribution of chain lengths between crosslinks that is formed during post‐curing.
Computer vision methods for the study of spinodal decomposition in polymer blends
Authors: Gur Y. S. , Malone M. F. , Bhatia Q. S. , Reynolds G. , Karasz F. E. , Hanson A. R. , Riseman E. M.
Published: December 2004

We demonstrate the use of computer vision techniques and optical microscopy to follow the kinetics and microstructure during spinodal decomposition of a polymer blend. Among other features, the mean of the population of the local maxima of the gradients in each image is computed; this global feature is shown to co‐develop with the phase separation of the blend. An algorithm is presented which employs the gradient magnitude technique to analyze optical images of spinodally decomposing polymer blends. This algorithm has been used to extract the Cahn‐Hilliard spinodal growth rates for a binary blend of polystyrene with poly(vinyl methyl ether). We show that the spinodal temperature can be found from the temperature dependence of this growth rate. We also show how additional shape features such as compactness might be used to study, the same binary blend.
Phase morphology of as‐molded and annealed blends of polyarylate/copolyester
Authors: Plummer H. K. , Peters C. R. , Golovoy A.
Published: December 2004

The phase morphology of injection molded blends of polyarylate (PAR) and a copolyester (PCTG‐5445) was studied by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The use of ultramicrotomy to prepare ⋍ 50 nm thin section TEM specimens and solvent etching to dissolve the PAR phase revealed PCTG as the matrix phase in the as‐molded state which crystallized into PCTG spherulites upon annealing. The most consistent morphological information vs. concentration of PCTG and the highest structural integrity of the PCTG spherulites was obtained from thin sections treated with a mixture of 75% methylene chloride as the solvent for the PAR and 25% 2‐propanol as the nonreactive diluent. XRD results from the annealed PCTG/PAR blends show crystalline reflections of 0.59, 0.53, 0.46, 0.38, and 0.35 nm, which disappear into the amorphous background below 50% PCTG.
Structure development in biaxially stretched polystyrene film: Part II. Theoretical analysis of orientation development
Authors: Choi Kyung‐Ju , Spruiell Joseph E. , White James L.
Published: December 2004

The present paper describes an analysis of the orientation developed in biaxially stretched polystyrene films in terms of the kinematics of the process and a viscoelastic constitutive equation. It was possible to achieve reasonable agreement of predicted and experimental birefringences through use of a convected Maxwell model and the Rheo‐Optical Law.
The influence of microstructure on the dynamic mechanical behavior of polycarbonate/poly(styrene‐co‐acrylonitrile) blends
Authors: McLaughlin K. W.
Published: December 2004

The influence of microstructure on dynamic mechanical behavior in the two phase blend of polycarbonate, (PC), with poly(styrene‐co‐acrylonitrile), (SAN), was studied by comparing the torsional response for injection and compression molded samples. A matrix component's glass transition (Tg) damping was only moderately altered by the presence of a dispersed phase although shifts in Tg, assigned to the local maxima in tan delta, indicated partial miscibility. In compression molded samples the onset of a co‐continuous PC phase suppressed the damping characteristics of the SAN Tg on the high temperature side shifting the assignment of this Tg to lower temperatures. This suppression results from PC dominating the composite's response at temperatures above the SAN Tg. In injection molded samples the onset of PC co‐continuity only partially suppressed the damping of the SAN Tg such that a doublet results. Co‐continuity within the injection molded microstructure could be idealized as alternating sheets which, subsequently, in the dynamic mechanical measurement are arranged In series to a shearing stress during torsion. Above the Tg of SAN the presence of such a series phase arrangement allows the composite to strain approximately to that extent which would be exhibited by pure SAN alone. The response of the composite is thereby approximately the response of SAN with the almost full extent of its Tg damping process realized.
An energy balance approach to solvent removal in polyamic acid coatings
Authors: Bauer C. L. , Farris R. J.
Published: December 2004

Using an energy balance approach incorporating a Flory‐Huggins expression for free energy and the strain energy of the material, the solvent removal process in liquid‐based coatings was shown to depend on stress and temperature. An equilibrium is obtained between residual solvent content and stress in the coating at a given temperature. Such stress‐dependent solvent removal behavior was observed with a polyamic acid coating solution‐cast using N‐methylpyrrolidinone.
New results on the spin welding of plastics
Authors: Tappe P. , Potente H.
Published: December 2004

Short welding times make spin welding particularly suitable for mass production. This paper presents an analysis of the friction phase, which makes it possible to estimate the influence of the welding parameters and the material being welded on the temperature in the welded zone, the melt rate, and the torque in the spin welding of semicrystalline thermoplastics. A comparison of experimental and calculated results shows an acceptable correlation. In addition, the influence of speed, axial pressure, and braking on the weld seam quality of different amorphous and semicrystalline thermoplastics is discussed.
Water sorption and hydrolytic stability of polycarbonates
Authors: Golovoy A. , Zinbo M.
Published: December 2004

The hydrolytic stability of a new commercial polycarbonate (Calibre 300, Dow Chemical USA) was investigated and compared with that of other commercial polycarbonates. The tests were conducted between 56% and 95% relative humidity (R. H.) at 100°C. Also performed were water immersion tests at 80 and 100°C. The water diffusivity was found to be 8.7 × 10−7 cm2/s at 100°C with an activation energy of 7.9 kcal/mole. These values are similar to other glassy polymers. The equilibrium water sorption, C∞, was found to increase with temperature and R.H. The isotherm at 100°C was determined to be: C∞ = 0.005945 [R.H.]. When samples immersed in a water bath at 100°C were transferred into room‐temperature water, visible aqueous microcavities were formed due to the condition of super‐saturation, and under stress may become crack initiation sites. For the polycarbonate investigated here, it was found that the decrease in weight‐average molecular weight (M̄)w was a first‐order process under a constant R.H. and temperature, and that hydrolytic embrittlement, i. e., (M̄)w <34,000, was reached after ca. 188, 143, 99, and 66 days under 56%, 73%, 87%, and 95% R.H., respectively, at 100°C. A comparison with reported hydrolytic stability data for other polycarbonates showed large differences in their stability which are believed to be due to the extent of end‐group capping (over 95% in Calibre 300) and resin purity: both phenolic end‐groups and some additives (i.e., fire retardants, thermal stabilizers) are known to accelerate hydrolytic degradation.
Solution of mass transfer in step growth polymerization in films with bulk in equilibrium
Authors: Khanna Ashok , Kumar Anil
Published: December 2004

We have analyzed step growth polymerization in a flat film with finite mass transfer resistance. We have shown rigorously that the molecular weight distribution (MWD) at equilibrium is given by the Flory distribution, and under reaction the form of the MWD does not change if the feed is either pure monomer or in equilibrium initially. Extensive computations have shown that it is possible to split the film into growing interfacial and shrinking bulk regions. It is possible to obtain similarity transformations of concentrations of condensation product, and polymer as time invariant profiles. Based on this finding, we have determined a solution for step growth polymerization with finite mass transfer in films. The results lie within 5% of the “exact” numerical computations, for all possible variations of parameters.
Heat capacity of polypropylene composite at high pressure and temperature
Authors: Hsieh K. H. , Wang Y. Z.
Published: December 2004

The heat capacities of isotactic polypropylene and its composite with glass fiber have been measured at high pressure, up to 7 MPa, in the melt state by high pressure differential scanning calorimetry (HPDSC). The values also have been calculated from the data of specific volume (V) measured by dilatometry and thermal conductivity (κ) and thermal diffusivity (α) measured by a compensating hot wire method. The values of the heat capacity measured from HPDSC are consistent with those from the calculation method. The heat capacities of molten polypropylene and its composite increase linearly with temperature at a constant pressure and decrease with pressure at a constant temperature. It was found that the heat capacity of polypropylene is insensitive to molecular weight. The heat capacities of molten polypropylene composites are found to be predicted by an additive rule from the weight fractions of heat capacities of polypropylene and glass fiber.
Bulk density of solid polymer resins as a function of temperature and pressure
Authors: Hyun Kun S. , Spalding Mark A.
Published: December 2004

In a plasticating extruder, solid polymers are heated and are subjected to high pressures before they are melted and delivered to a die. In both the solids conveying and melting sections, these temperature and pressure increases will compact the unmelted polymer bed as it moves down the screw channel. Performance of the extruder depends in part on how well the screw design matches the compaction behavior of the resin for a given set of process conditions. The design of these screw sections, however, is often done based on past experience and with little knowledge of the resin compaction behavior. A much improved design would include screw performance prediction using variable bulk density and computer simulations. Computer simulations, however, are often performed using constant solid bulk density because of the lack of reliable density data as a function of both pressure and temperature. An instrument was developed for studying the compaction behavior of pellet and powder resins. Bulk densities and storage friction coefficients are reported for several important thermoplastic resins as a function of temperature and pressure. The bulk density data were fitted to a semi‐empirical model.
A modified power law model for the steady shear viscosity of polystyrene melts
Authors: Campbell Gregory A. , Adams Mary Elizabeth
Published: December 2004

An engineering equation that describes the steady shear viscosity of polystyrene melts is developed as an extension of the well known power law model for non‐Newtonian viscosity. The parameters in the equation have been related to weight and number averaged molecular weights and temperature. The model is tested on data for both narrow and broad molecular weight polystyrenes whose properties span most materials of commercial importance. This equation predicts the melt viscosity‐shear rate behavior for both narrow and broad distribution polystyrenes from knowledge of weight and number averaged molecular weights and temperature. Our analysis directly yields shift factors for the shear rate and viscosity axes. Therefore, no secondary calculations are necessary to generate master curves for polystyrenes. The shift factors are related to weight and number averaged molecular weights of the polystyrenes and temperature of the melt.
Reaction injection molding of polyureas. II: Rheo‐kinetic changes and model simulation
Authors: Wang K. J. , Huang Y. J. , Lee L. James
Published: December 2004

An experimental and theoretical study of reaction injection molding (RIM) of polyurea was conducted in this work. A lab‐scale RIM machine was used to carry out the polyurea bulk polymerizations. A “free‐table” viscometer was designed to measure the fast rheological changes and liquid‐solid transition. A mathematical model was proposed to simulate the fast reaction and rheological changes in the polyurea RIM process. The parameters of this model were determined based on the solution polymerization data from FTIR and Haake rheometer measurements. Combined with an appropriate heat transfer equation, this model predicts fairly well the adiabatic temperature and viscosity rises of bulk polyurea reactions in RIM.
Analysis of the performance of plasticating single‐screw extruders with a new concept of solid‐bed deformation
Authors: Lee Kee Yoon , Han Chang Dae
Published: December 2004

The performance of plasticating single‐screw extruders is analyzed by combining three functional sections: (a) solids‐conveying section, (b) melting section, and (c) melt‐conveying section. In the analysis of the melting section, we have incorporated a new concept of solid‐bed deformation (i.e., the rheology of the solid bed) into Lindt‐Elbirli's analysis and included convective heat transfer in the energy equation. Specifically, we have computed stresses on the surfaces of the solid bed, which is surrounded by thin melt films and a melt pool, and, also, computed the apparent modulus of the solid bed in the bulk state as a function of temperature and position within the solid bed, along the extruder axis. From this information, we were able to compute the extent of solid‐bed deformation, by assuming a linear stress‐strain relationship as the constitutive equation of the solid bed. In this approach, we do not assume a priori whether the solid bed is rigid or freely deformable. The solution of the system equations gives us the following information: (a) whether or not the solid bed deforms and if it does, then, how much; (b) the solid‐bed velocity along the extruder axis; (c) pressure profiles along the extruder axis; (d) solid‐bed profiles in the melting zone along the extruder axis; (e) temperature profiles along the extruder axis; (f) velocity and temperature distributions in the melt pool along the extruder axis; and (g) thicknesses of thin melt films surrounding the solid bed. Theoretically predicted solid bed and pressure profiles along the extruder axis are compared with experimental results reported in the literature. We have pointed out an urgent need for measurements of the apparent modulus of the solid bed in the bulk state as a function of temperature and pressure, under a combined shear/drag flow field.
Chain structure, phase morphology, and toughness relationships in polymers and blends
Authors: Wu Souheng
Published: December 2004

We present chain structure, phase morphology, and toughness relationships in thermoplastic polymers and polymer/rubber blends. In neat polymers, molecular aspects of craze/yield behavior are controlled by two chain parameters: entanglement density νe and characteristic ratio C∞. The crazing stress is proportional to ν, and the yield stress is proportional to C∞. The dispersed rubber toughens a polymer/rubber blend mainly by promoting energy dissipation of the matrix. The toughening efficiency correlates with the rubber phase morphology and the chain structure of the matrix.
Low density foams produced from sheared ultra‐high‐molecular‐weight polyethylene gels
Authors: Matthews Flori'da M. , Hoffman D. Mark
Published: December 2004

Low‐density foam (0.02–0.09 g/cc) was produced from gels of ultrahigh molecular weight (UHMW) polyethylenes in solvents with melting points above ambient. The hot PE solutions were stirred at high speed to induce extended chain crystalline gels. These gels were subsequently cooled to allow the solvent to solidify and then the solvent was extracted with alcohol or sublimed. This resulted in a tough, low density foam or a collapsed mass depending mainly on the concentration of the polymer. Shrinkage was significant until polymer concentrations reached 4–5%. Foam cell size varied between 5–30 μm, or 25–75 μm depending on the method of preparation. Polarizing microscopy revealed both spherulitic and row‐nucleated structures depending on the thermal history followed during the sample preparation. We were also interested in whether or not small particles could be used to influence the nucleation and growth of the solution crystallization process. These particles could be suspended in the gel and stabilized in something like a colloidal necklace as has been proposed recently. We successfully incorporated small (0.5 μm) tungsten particles in UHMWPE gels which remained in the foam on extraction of the solvent. Polyethylene containing carbon black particles produced less successful results. These effects may be related to absorption associated with gelation of UHMWPE.
Thermorheological analysis of glass beads‐filled polymer melts
Authors: Lepez Olivier , Choplin Lionel , Tanguy Philippe A.
Published: December 2004

The complex viscosity of two thermoplastic polymer melts (high density polyethylene and polystyrene) filled with polydisperse glass beads (10–53 μm) has been studied in the domain of linear viscoelasticity as a function of frequency, temperature, and filler concentration. In the experimental windows examined, the complex viscosity can be well described by a new empirical model, which contains a Cross‐type viscosity model for the frequency dependence, a Quemada‐type model for the filler concentration dependence, and a compensation effect for the temperature dependence. This model allows the prediction of the complex viscosity of a glass bead‐filled thermoplastic melt provided only four parameters are known, namely: the average maximum packing volume fraction characteristic of the filler geometry and size distribution, the flow activation energy of the thermoplastic, the shear‐thinning parameter, and an adjustable parameter, also characteristic of the thermoplastic.
Effect of dispersion of particles on viscoelasticity of CaCo3‐filled polypropylene melts
Authors: Li Lin , Masuda Toshiro
Published: December 2004

Viscoelastic properties of polypropylene melts filled with small (0.15 μm) and large (4.0 μm) CaCO3 particles have been measured. The effects of particle size, loading, and rheological history on the dispersion of particles have been investigated. The dispersion of particles was found to decisively influence the viscoelastic properties of these filled polymers. The systems filled with large particles exhibit a relatively stable viscoelastic behavior. The small particle‐filled polymers with low loading are stable similarly to the large particle‐filled system. For the system filled with 30 wt% small particles, there appears a “second plateau” in the storage modulus G′ curve in low frequency region and the height of the second plateau depends strongly on the rheological history. The results are interpreted in terms of the formation of an internal structure of particles. It was found that the internal structure of particles is broken up by a steady shear flow and the dispersion of particles is changed.