bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crazing in polypropylene
Authors: Jang B. Z. , Uhlmann D. R. , Vander Sande J. B. 
Published: May 2005

AbstractThe subject of crazing in crystalline polymers is reviewed and specific consideration given to crazing in polypropylene (PP). Tensile tests conducted over a wide spectrum of temperatures and strain rates indicate that, for a given test temperature, there exists a critical strain rate above which crazing is the dominant deformation mode of PP. Similarly, for a given strain rate, there exists a critical temperature which demarcates crazing from shear yielding as the characteristic process of deformation. High deformation rates and low temperatures favor crazing, while low rates and high temperatures favor shear yielding. Crazes in crystalline PP were found to be morphologically similar to those in glassy polymers: high reflectivity, large area‐to‐thickness ratio, and planarity. They have a higher tendency to bifurcate than those in glassy polymers. Two types of craze fibrils could be identified: those parallel to σ11, and the randomly oriented interconnecting fibrils. It is demonstrated that microtome‐trimming at low temperature followed by suitable chemical treatment is an effective technique of sample preparation for SEM examination of craze morphology in crystalline polymers. Further evidence has been provided that crazes in spherulitic polymers do not in general follow an interspherulitie path, but propagate through spherulites. The length of a craze in PP is not restricted to one spherulite diameter, nor does it grow radially.
Craze initiation, crack growth, and lifetime trends in fatigue of poly(vinylchloride)
Authors: Mandell J. F. , Chevaillier J.‐P. F. 
Published: May 2005

AbstractThe fatigue behavior of pure poly (vinylchloride) (PVC) and a PVC pipe compound has been investigated. Unnotched S‐N lifetime, fatigue‐crack growth, and craze/crack‐initiation data are presented. The data trends, coupled with direct‐microscopic observation, suggest that the unnotched‐specimen lifetime in fatigue is dominated by the craze/crack‐initiation process. This differs from the observed consistency of crack propagation and specimen‐lifetime trends in several other polymers, whose failure can be traced to the initiation and growth to instability of a single dominant craze/crack.
The creep of kevlar‐29 fibers
Authors: Lafitte M. H. , Bunsell A. R. 
Published: May 2005

AbstractSingle Kevlar‐29 fibers have been subjected to creep loading over a temperature range of 23 to 400°C for which the applied load was 50 percent that of tensile strength at each temperature considered and also subjected to a range of loads at 23°C. It has been shown that strain expressed as a logarithmic function of time describes the experimental results obtained. Up to 70 percent of breaking load, a primary creep mechanism dominates and at higher loads a secondary creep process becomes increasingly important.
Capillary extrusion of elastomeric emulsion crosslinked interpenetrating networks
Authors: Silverstein M. S. , Narkis M. 
Published: May 2005

AbstractThe rheological properties of an elastomeric emulsion thermosetting (EMSET) interpenetrating network (IPN) of poly(ethyl acrylate) (70 percent) and polystyrene (30 percent) were studied using a capillary rheometer to test if the submicron thermoset particles, persumably the flow units, could flow as a thermoplastic matrix. The IPN exhibited power law behavior over a wide range of shear rates (0.05 to 500 s−1), with a power law exponent of approximately 0.18 over a large range of temperatures (80 to 200°C), without a yield stress or a Newtonian plateau evident. The flow activation energies were found to be comparable with most processable thermoplastic materials at 4 kcal/mole for constant shear rates, and 20 kcal/ mole for constant shear stresses. The effect of a roll mill shear modification step prior to extrusion indicated stability of the flow units. The pervasive rippling melt fracture and the significant slip velocity at the wall emphasized the importance of slip in the flow mechanism of this elastomeric EMSET IPN.
Errors that result from thermal degradation during shear measurements on some molten polymers
Authors: Gregory D. R. , Wampler F. C. 
Published: May 2005

AbstractShear sensitivities of molten polymers may be determined from measurements made on individual samples subjected in one test to a series of either increasing or decreasing shear rates. Many polymers, including polyesters, degrade when molten. If the effect of degradation is significant, and is ignored during data analysis, a significant error could result. The magnitude of the error depends directly on the magnitude of the reaction rate constant for degradation, which differs from polymer to polymer and which increases as temperature increases. In rheological characterization of molten polymers, one should know or determine the degradation behavior of the polymer being investigated and then account for it in the data analysis. Experimental results for poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) are presented and discussed. Ways to account for degradation in shear sensitivity measurements are also presented.
Effect of the cross‐channel flow on the melting performance of a single‐screw extruder
Authors: Lindt J. T. , Elbirli B. 
Published: May 2005

AbstractA new comprehensive mathematical model has been developed for the melting zone of a single‐screw extruder processing a (semi) crystalline polymer. It has been demonstrated that the cross‐channel flow plays an important role in the melting mechanism. When incorporated into a non‐Newtonian fluid model combined with the rigid solid bed concept, the present analysis leads to significantly improved predictions of the melting rate and axial pressure profile. This conclusion is supported by experimental data and by a quantitative examination of the flow and thermal patterns prevailing in the melting zone.It is suggested that under the constraints of the commonly accepted assumptions concerning the physico‐chemical properties of the polymeric system the transport analysis of the Maddock mechanism is virtually complete.
Continuous reactive processing I: Reactive coating
Authors: Schmidt M. J. , Castro J. M. 
Published: May 2005

AbstractThe big success of the reaction injection molding (RIM) process has brought about a marked interest in reacting polymer processing. In the present work, we study the technical feasibility of a continuous process to coat metallic conductors using reacting polymers. In the envisioned system, RIM type reactants are mixed and then injected into a tubular reactor through the center of which we pass the cable to be coated. The predictions of the mathematical model developed show that a feasible process can be designed by adequate control of the heat transfer phenomena. The process needs in general, a low reactor temperature and a high cable temperature.
Crystallinity as a selection criterion for engineering properties of high density polyethylene
Authors: Hoffman D. Mark , McKinley Barbara M. 
Published: May 2005

AbstractThe Differential Scanning Calorimeter (DSC) was used to discriminate among 25 commercial high density polyethylenes (HDPE) on the basis of their degree of crystallinity and melting temperature. The area under the melting endotherm correlated directly with density and inversely with creep and thermal expansion measurements. Since high crystallinity was related to the design required properties of density, creep, and thermal expansion, DSC studies readily identified eight of the more promising polymers from the group of 25. The overall crystallization kinetics of polyethylenes with 75 percent crystallinity were analyzed by the Avrami and Fischer‐Turnbull equations. Results indicate small disk‐like spherulites (Avrami n = 2) following nucleation‐controlled growth kinetics. These conclusions are in reasonable agreement with polarizing microscope observations. An equilibrium melting temperature between 141 and 142°C was estimated from Hoffman‐Weeks plots. Processing thick parts from highly crystalline polyethylene is difficult because of the 14 percent volume change on crystallization. Higher degrees of crystallinity are associated with moderate molecular weight, so the viscosity range of these polyethylenes is not especially suited for processing by extrusion. These caveates necessitate tradeoffs between optimal design properties and processing requirements for HDPE parts.
Flexible microcellular foam from polymethylpentene/cyclohexane
Authors: Williams Joel M. , Moore Joyce E. 
Published: May 2005

AbstractRapid freezing of a polymethylpentene (PMP)/cyclohexane solution to −80°C gives a tough, flexible foam, in marked contrast to the weak, friable foams obtained by phase‐separation of PMP from other solvents. X‐ray diffraction and differential scanning calorimetry (DSC) data indicate that the isotactic PMP is in an amorphous state. The production of a flexible, robust foam tube from PMP/cyclohexane implies that this material could find applications as replacement parts for arteries and veins or as filter devices. In sheet form, this material seems ideally suited for use as light‐weight insulation for clothing because its open, microcellular structure permits moisture to escape as vapors, but retards air flow. This study demonstrates that process parameters, such as solvent composition, play an important role in determining the various microstructures and physical properties that can be obtained from a single polymer.
Enhancing adhesion by ion beam‐induced atomic mixing at the interface between copper film and polyimide substrate
Authors: Koh S. K. , Pae K. D. , Stoffel N. G. , Hart D. L. 
Published: May 2005

AbstractIon beam mixing was used to improve the adhesion between deposited Cu film (400 Å) and polyimide (PI) substrate. Ar+ ion with the energy levels between 180 and 200 keV, and the dose between 1014 to 4 × 1016 ions/cm2 were used. The surface analyses were carried out by Rutherford Backscattering Spectroscopy (SEM). RBS analysis, using 2 MeV He+ ions, showed mixing of Cu and FI and the mixing depended on the Ar+ energy and dose. The X‐ray study showed a very broad halo for deposited Cu film but the (111) peak appeared after the Ar+ implantation and the peak increased with Ar+ ion dose. Optical micrographs showed that Cu film formed circular bubbles after many thermal cycles when adhesion was poor and fracture cracks when adhesion was good.
Process parameters estimation for structural reaction injection molding and resin transfer molding
Authors: González‐Romero V. M. , Macosko C. W. 
Published: May 2005

AbstractSome design strategies for structural reaction injection molding (S‐RIM) and resin transfer molding (RTM) are presented. Our approach makes use of moldability diagrams to define the parameters necessary to meet the process requirements. Moldability diagrams are presented for the filling and curing steps. The criterion for selecting the amount of fiber reinforcement, injection time, catalyst level, and process temperatures in order to optimize properties and demold time is described.
Mechanical and thermal properties of epoxy resins with reversible crosslinks
Authors: Engelberg P. I. , Tesoro G. C. 
Published: May 2005

AbstractThe tensile properties: Young's modulus, ultimate tensile strength, ultimate elongation, the glass transition temperature, and the dynamic mechanical properties (dynamic shear modulus (G'), loss tangent (Tan δ)), of three epoxy resins (Epon 828, Epon 836, Epon HPT 1071) cured with the disulfide‐containing crosslinking agent—4.4‐dithiodianilme (DTDA) have been characterized. The results show that DTDA is a satisfactory crosslinking agent for the epoxide resins that have been studied as compared to the well‐known curing agent methylene dianiline (MDA). There are no significant differences between the properties of Epon 828 cured with DTDA at stoichiometric ratio (2:1) and Epon 828 cured with DTDA at small amine excess ratio (1.75:1). The glass transition temperature of the cured tetrafunctional epoxy resin Epon HPT 1971 (235°C) is significantly higher than that of difunctional epoxy resins such as Epon 828 (Tg–175°C), but the product is too brittle to be used without plasticizer.
A comparison of torsional and capillary rheometry for polymer melts: The Cox‐Merz rule revisited
Authors: Venkatraman S. , Okano M. 
Published: May 2005

AbstractRheological properties of high and low density polyethylene melts (HOPE and LDPE) were measured under two different deformation modes: sinusoidal strain (“dynamic”) and constant rate‐of‐strain (“steady‐state”). For the sinusoidal measurements, a torsional geometry was used, whereas the “steady‐state” measurements were carried out in both torsional and capillary flow. The complex and “viscous” components of the “dynamic” viscosity were compared with the “steady‐state” viscosities, corrected for both non‐Newtonian and end effects. For the HDPEs, the Cox‐Merz rule was found to be not valid. The corrected viscosity is closer in magnitude to the “viscous” component, and not to the complex viscosity. However, for the LDPEs, the corrected viscosity is equivalent to the complex viscosity. These results are compared to other correlations found by various authors.
Binary blends of nylons with ethylene vinyl alcohol copolymers: Morphological, thermal, rheological, and mechanical behavior
Authors: Ahn Tae Oan , Kim Chang Kee , Kim Byung Kyu , Jeong Han Mo , Huh Jung Do 
Published: May 2005

AbstractBinary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH‐62) and 71 (EVOH‐71) mole percent vinyl alcohols, with nylons (nylon‐6, nylon‐6/12, and nylon‐12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH‐62/nylon‐6 and EVOH‐71/nylon‐6 blends showed homogeneous phase morphologies in the nylon‐6‐rich region, and fine phase separations (c.a. 2 × 10−7 m) in the EVOH‐rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH‐71/nylon‐6/12 and EVOH‐71 /nylon‐12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed.
Crystallization kinetics and nucleating agents for enhancing the crystallization of poly(p‐phenylene sulfide)
Authors: Song Sang S. , White James L. , Cakmak Mukerrem 
Published: May 2005

AbstractAn experimental study of crystallization kinetics and the influence of nucleating agents on the solidification of poly(p‐phenylene sulfide) (PPS) is described. The effect of molecular weight is considered by investigating PPS samples having different viscosity levels. We studied the effect of a range of nucleating agents including aluminum oxide, calcium oxide, silicon dioxide, titanium dioxide, kaolin, and talc. All of these compounds were found to enhance the rate of crystallization; in particular, silicon dioxide, kaolin, and talc were the most effective nucleating agents. An effort to study particle size effects of the silicon dioxide showed that the nucleation was very sensitive to the source of the material. These studies did, however, show that nucleation rates tended to increase with decreasing particle size and increasing loading of silicon dioxide. Comparison of PPS crystallization rates with those of other polymers indicates that it crystallizes much more slowly than polyethylene or isotactic polypropylene and is slower than polyetherether‐ketone, when comparisons are made on an equivalent basis. PPS crystallizes at similar rates to polyethylene terephthalate (PET). However, our nucleated PPS does not crystallize as rapidly as nucleated PET.
The role of repulsive interactions in polyamide blends
Authors: Ellis T. S. 
Published: May 2005

AbstractPhase phenomena in mixtures containing any combination of aliphatic and aromatic polyamides can be formulated by the application of a mean‐field binary interaction model. This has been achieved by the quantitative analysis of the solubility of an aromatic polyamide, denoted as nylon 3Me6T, in a homologous series of aliphatic polyamides. A critical feature of this development required an estimation of the upper and lower bound concentration of methylene units of the latter for which the aromatic polyamide moved from a miscible to immiscible condition. The fabrication of random copolyamides of caprolactam‐laurolactam and 2‐pyrrolidinone‐caprolactam, respectively, has allowed an accurate determination of these critical limits. A survey of the behavior of polyamide blends will be discussed in light of this improved quantitative definition of the model. A principal feature of these analyses is the exclusion of a role for hydrogen bonding interactions. Details concerning the nature of interactions in these systems and how they are influenced by chemical structure are discussed.
Poly(Phenylene oxide)/polyamide blends via reactive extrusion
Authors: Campbell J. R. , Hobbs S. Y. , Shea T. J. , Watkins V. H. 
Published: May 2005

AbstractReactive extrusion of functionalized polymers provides a convenient, commercially attractive route for the preparation of copolymers useful in compatibilization of polymer blends. In the current study, the grafting chemistry of maleic anhydride to poly(phenylene oxide) in the absence of a radical initiator is contrasted to that of efficient quinone‐methide trapping agents such as maleimides. In the case of maleic anhydride, functionalization is shown to occur randomly along the polymer backbone whereas maleimides react to give both main chain and end‐group derivatives. Use of this anhydride‐functionalized polyfphenylene oxide and an end‐group functionalized analog in blends with polyamide‐6,6 affords high levels of graft and diblock copolymers respectively, sufficient for the preparation of highly ductile materials. The properties of these polyamide blends are found to depend on the amount of copolymer formed during extrusion with final copolymer levels being in turn returned to the degree of anhydride functionalization. The properties and morphology of blends containing graft or diblock copolymers derived from main‐chain and end‐group functionality respectively, are rationalized in terms of the relative effectiveness of different copolymer structures in blend compatibilization.
Enhanced spherulite growth rates of isotactic polypropylene in incompatible blends
Authors: St‐Jean G. , Barreto M. C. , Brown G. R. 
Published: May 2005

AbstractIsothermal radial growth rates (G) of isotactic polypropylene (iPP) spherulites in immiscible blends with a polyethylene based ionomer (1) partially neutralized with Zn+2, (2) completely acidified, and (3) completely esterified have been determined at crystallization temperatures between 118 and 124°C by time‐lapse photomicroscopy. In these blends iPP spherulites grow with increased G as compared to that of pure iPP. This behavior is attributed to increases in the rate of transport, due to limited miscibility induced by mechanical mixing. However, subtle differences in the melting behavior suggest that changes in Spherulite morphology may also be a contributing factor.
Experimental analysis of inertial effects in the impact testing of polymers
Authors: Zanichelli C. , Rink M. , Pavan A. , Ricco T. 
Published: May 2005

AbstractInertial effects occurring In the impact testing of polymers were experimentally probed by measuring the force versus time response of various materials with two different instrumented impact testers, both with and without anvil. The analysis focused on the first force peak, which was modeled using a mass‐spring analog to account for machine‐specimen interaction.
Phenolic triazine (PT) resins. II: Cure characterization by dynamic melt rheology and its comparison to DSC
Authors: Khanna Y. P. , Kumar R. , Das S. 
Published: May 2005

AbstractA new approach involving dynamic melt rheology i.e. dynamic mechanical analysis in a molten inert matrix, is presented for studying the cure of thermoset resins. The degree of cure by dynamic melt rheology has been correlated with that from differential scanning calorimetry, DSC (correlation coefficient = 0.87) and the lack of an excellent correlation is attributed to the uncertainties with the DSC method at higher cure levels. A kinetic expression with appropriate constants, “E, A, and n” from our new approach is presented for predicting the time‐temperature dependence of the degree of cure. Advantages of dynamic melt rheology are discussed in relationship to conventional dynamic mechanical and DSC methods.
A double bubble tubular film process to produce biaxially oriented poly(p‐phenylene sulfide) (PPS) film
Authors: Rang Ho Jong , White James L. 
Published: May 2005

AbstractA double bubble tubular film process to produce biaxially oriented poly(p‐phenylene sulfide) (PPS) film is described. Operating windows were developed for stable operation of both the first and second bubbles. Films produced from single bubble tubular film extrusion were largely amorphous having only seven to nine percent crystallinity. Double bubble PPS tubular film had up to 20 percent crystallinity which was increased to 30 percent by further annealing. The first and second bubble films had surface roughness standard deviation heights of 0.01 to 0.04 μm. Orientation was characterized by birefringence and wide angle X‐ray diffraction pole figures of the 110 and 112 reflections. Biaxial orientation factors were computed. The double bubble films had higher Young's modulus and tensile strength but lower elongation to break than the single bubble films. Annealing further increases Young's modulus and tensile strength but decreases elongation to break. Double bubble and annealed films with roughly equal second bubble drawdown ratio and second blow up ratio tend to have balanced properties in the plane of the film.
The elastic properties of woven polymeric fabric
Authors: Warren William E. 
Published: May 2005

AbstractThe in‐plane linear elastic constants of woven fabric are determined in terms of the specific fabric microstructure. The fabric Is assumed to be a spatially periodic interlaced network of orthogonal yarns and the Individual yarns are modeled as extensible elastica. These results indicate that a significant coupling of bending and stretching effects occurs during deformation. Results of this theoretical analysis compare favorably with measured in‐plane elastic constants for Vincel yarn fabrics.
Image reversal in a negative deep UV resist
Authors: Hargreaves John S. 
Published: May 2005

AbstractA negative deep UV resist, XP 8843 (Shipley Co.),Since this paper was written the name of this resist has been changed from XP 8843 to SNR 248‐10.
has been made positive by the addition of 1,2,4‐triazole. This is achieved by exposing the resist in the presence of the additive thereby inhibiting the crosslinking reaction. After exposure the additive is removed by heating under a vacuum. Unexposed areas of the resist may then be exposed and the resist crosslinked under normal processing conditions.