bluuebunny/crossref_metadata_2025 huggingface dataset:
Melt rheology and extrudability of polyethylenes
Authors: Utracki L. A. , Catani A. M.
Published: December 2004

Commercial high density polyethylene (HDPE), low density polythylene (LDPE), and linear low density polyethylene (LLDPE) resins were tested at 150, 170, and 190°C in steady state, dynamic, and extensional modes. Within the low rates of deformation \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω ≤ 0.3, the steady state and dynamic functions agreed: η = η′ and N1 = 2G′; at the higher rates, the steady state parameters were larger. The elongational viscosity, ηe, was measured under a constant rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}, or stress, σ, condition. In the first case for LLDPE, the transient η reached an equilibrium plateau value, ηe. For HDPE, η increased up to the break point. For LDPE, stress hardening was recorded. Under constant stress the ηe, could always be determined; its value, within experimental error, agreed with the maximum value of η determined in a constant \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document} experiment. The maximum strain at break was only ε = 1.5 for HDPE and 3, to 4 for LDPE and LLDPE. The rate of deformation dependence of the η (or η′) and ηn may be discussed in terms of the Trouton ratio, RT = ηe/3η at \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω = \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document}: RT ≤ 1.2 for LLDPE, RT ≤ 2.5 for HDPE, and RT ≤ 15 for LDPE. The PE resins were extruded at 190°C through a laboratory extruder equipped with a slit or rod die. The rotational speed of the screw varied from 0 to 90 rpm. Extrusion pressure, output, and energy were measured and correlated with the rheological parameters of the resins.
A thermodynamic prediction of tie chain length distribution in drawn semicrystalline polymers
Authors: Popli Rakesh , Roylance David
Published: December 2004

The mechanism underlying fracture of many oriented semicrystalline polymers is hypothesized to be a thermally activated, stress‐aided rate process in which the tie chains connecting crystalline units suffer thermomechanical dissociation. Some previous numerical models based on this concept have assumed a Gaussian distribution of tie chain contour lengths which are ruptured progressively by successively higher specimen strains, and have used electron spin resonance (ESR) spectroscopy to obtain the numerical parameters of the distribution. The distribution of tie chain lengths in the intererystalline region is calculated theoretically in this paper, based on minimization of free energy. Our results, although in basic agreement with earlier models, suggest a reinterpretation of some of the ESR findings with regard to molecular fracture processes.
Structure‐property relationships in thermoplastic elastomers: I. Segmented polyether‐polyurethanes
Authors: Woo Edward J. , Farber G , Farris Richard J. , Lillya C. Peter , Chien James C. W.
Published: December 2004

Segmented poly(ether‐b‐urethanes) have been synthesized with 2000 MW polypropylene oxide coupled with diisocyanates and diol type chain extenders. The diisocyanates used were symmetric rigid 4, 4′‐diphenylmethane diisocyanate (MDI), linear aliphatic hexamethylene diisocyanate (HDI), and unsymmetric rigid toluene‐2, 4‐diisocyanate (TDI). The chain extenders were symmetric N, N′‐bis(2‐hydroxyethyl) terephthalamide (BT) and N, N′‐bis(2‐hydroxyethyl)‐hydroquinone (BH) unsymmetric N, N′‐bis(2‐hydroxyethyl)isophthalamide, and linear aliphatic 1, 4‐butanediol (B). Hard segment contents ranged from 20 to 40 wt percent. The thermal behavior of these materials is consistent with phase separation into separate hard and soft domains, In order of increasing temperature above the soft segment Tg, there are transitions which occur in the regions −56 to −36°C (Ta), 70 to 90°C (Tb), and 138 to 168°C (Tm). The former is probably associated with soft segment change from a viscoelastic to an elastomeric state. Values of Ta are ∼ −51 C and −56°C for the MDI‐BT and HDI‐BT polymers, respectively, and are independent of hard segment content. Microscopy showed that the former polymers have spherulitic morphology, so these materials have good microphase separation and exhibit crosslinked elastomeric properties. The TDI‐BT or BI and MDI‐B polyurethane have composition‐independent Ta values of −41 and −36°C, respectively. These materials probably have considerable “domain‐bound‐ary‐mixing”. At low hard segment content the MDI‐B polymers behave as non‐crosslinked elastomers. Only the MDI‐BI polymers have Ta values, which are strongly affected by composition, increasing in magnitude with increasing of hard segment content. This is interpreted as significant “mixing‐in‐domains” and is supported by morphology observed by microscopy. The next higher transition, Tb, probably involves dissociation of interdomain hydrogen bonding. In the case of the MDI‐BT polyurethanes, the spherulites associated with the hard domains had disappeared at 141°C and the few small spherulites in the MDI‐BI polymers disappeared at 130°C. The Tb values are 70, 83 to 90, and 100°C for the MDI‐B, HDI‐BT, and HDI‐BI polymers, respectively. The melting transitions occurred between 138 to 168°C for the various polyurethanes except for the MDI‐BT systems which decompose before melting. Thermal decomposition is a two‐stage process. Hard segments decompose between 200 and 300°C. The initial decomposition temperatures are lowered in the presence of strong acid. Soft segments decompose at higher temperatures. The mechanical properties of the MDI‐BI polyurethanes are charateristic of crosslinked elastomer, the results of which will be presented in a subsequent paper.
Some properties of silane‐grafted moisture‐crosslinked polyethylene
Authors: Narkis M. , Tzur A. , Vaxman A. , Fritz H. G.
Published: December 2004

Silane‐grafted polyethylene materials are processed in conventional thermoplastic fabrication machines. The shaped articles are then crosslinked in water by the formation of Si‐O‐Si crosslinks. This paper represents studies on the crosslinking progress in different environments at various temperatures. Molecular orientation is shown to become permanent and mostly irrecoverable even at 150°C, in the silane‐grafted solid state crosslinked specimens (the crosslinking temperature in water is well below the polymer melting temperature). These frozen molecular orientations have a significant effect on the tensile properties of the crosslinked materials causing higher yield stresses and lower elongations at break. The thermal and tensile properties of some silane‐grafted crosslinked polyethylene samples and peroxide‐crosslinked materials are compared and analyzed.
Thermal analysis of photocurable materials
Authors: Appelt B. K. , Abadie M. J. M.
Published: December 2004

Photocurable materials such as photoresists, UV‐curable inks and paints, etc., can be analyzed by a variety of techniques. Commonly, these analyses are performed in a discontinuous mode, i.e., samples are exposed to light for varying times and subsequently they are subjected to analysis. Rates of reaction, conversion, etc., are determined from the residual functionalities; in the case of differential scanning calorimetry, these parameters are derived from the residual heat of reaction. In order to determine “photo speed” or sensitivity, a number of exposures of varying duration are necessary to obtain rates of reaction. By combining an exposure unit with a differential scanning calorimeter, the photoreaction can now he observed in situ. Determination of speed or rate of reaction is reduced to a single experiment. As a consequence, effects of wavelength, intensity, temperature, and environment are quickly examined as is demonstrated here for a photoresist. During the second scan residual exotherms can be used to determine reaction extend or formation of new thermally active products. Conversion may be limited if Tg rises during polymerization to exceed exposure temperatures. In addition, the formation of inaccessable functionalities has to be accounted for during evaluation.
Minimum end time policies for batchwise radical chain polymerization, part V—multicomponent copolymerization with one charge of comonomers
Authors: Chen Show‐An , Lee Song‐Tai
Published: December 2004

For batchwise radical chain solution multicomponent copolymerization, the minimum end time problem for the predetermined monomer conversion and number average molecular weight has been studied by considering the initiator concentration (or feed rate) and temperature as the two control variables. Applying the maximum principle and “unit segment treatment” (by which the co‐polymerization can be treated as homo‐polymerization in the kinetic analysis), it is found that for initiator addition processes the optimal initiator addition policy is to make the rate of initiation constant for the optimal temperature variation case, and the initiator concentration constant for the isothermal case as in homo‐polymerization. For single charge of initiator processes, the optimal initial initiator concentration is such that it should be maintained at the lowest possible value (by which the polymerization is strongly dead‐end) for the optimal temperature variation case without chain transfer steps, and at some optimal value (by which the polymerization is near dead‐end) for the best isothermal case.
Glass fiber‐filled thermoplastics. I. Wall and processing effects on rheological properties
Authors: Chung Bin , Cohen Claude
Published: December 2004

A systematic study of wall effects on the shear viscosity of short glass fiber‐filled polypropylene and polystyrene is presented. The dependence of these effects on capillary radius, shear rate, temperature, and polymer matrix is examined. The “true” viscosity curves of these materials (free from wall effects) can be obtained by an extrapolation procedure. Breakage of glass fibers in the high shear‐rate processes of extrusion and injection molding lead to an appreciable reduction of the viscosity of these materials and is probably the more important effect to take into account in these processes.
Glass fiber‐filled thermoplastics. II. Cavity filling and fiber orientation in injection molding
Authors: Sanou Muneharu , Chung Bin , Cohen Claude
Published: December 2004

Mold filling of a rectangular cavity of three different thick nesses fed from a reservoir is studied for unfilled and glass fiber‐filled polypropylene and polystyrene. The shapes of flow fronts studied by short‐shots are affected predominantly by the thickness of the cavity with other parameters playing a less important role. Pressure drop versus volumetric flow rate inside the thinnest cavity is studied experimentally and predictions are made from a computer simulation of mold filling. The orientation of fibers in the cavity is examined using a reflect‐type microscope and the orientation is found to depend on cavity thickness, melt temperature, fiber content, and to a lesser extent, on volumetric flow rate. In the thinnest cavity, where the flow is quasi‐unidirectional, the fibers remain in the plane of flow oriented either along the flow direction or perpendicular to it, except in the region near the flow front, where they follow a “fountain” flow behavior.
Mechanical properties of polypropylene filled with calcium carbonate
Authors: Mitsuishi Kazuta , Kodama Soji , Kawasaki Hitoshi
Published: December 2004

The tensile behavior of polypropylene (PP) filled with calcium carbonate particles has been studied using a tensile test. In particular, the effect of strain rate, filler content, and filler size upon the elastic modulus, yield stress, and strain of surface‐modified and unmodified particles‐filled PP were investigated. The results indicated that the elastic modulus and yield stress of an unmodified system were increased with an increase of strain rate and filler content, and with a decrease of filler size. The yield strain was decreased with an increase of filler content, and with a decrease of filler size, but did not depend on the strain rate. Although the dependence of elastic modulus on the filler size was maintained even by the surface‐modified fillers, that dependence on the strain rate and filler content was decreased by such fillers. This may be because the modifier is present at the interface of filler and polymer matrix.
Separating polymer solutions using high pressure lower critical solution temperature (LCST) phenomena
Authors: McClellan Alan K. , McHugh Mark A.
Published: December 2004

A lower critical solution temperature (LCST) phase split can be used as an alternative to steam stripping for separating polymer solutions, By adding a supercritical fluid (SCF) additive to the polymer solution, the LCST can be lowered, thus minimizing the possibility of polymer degradation and also reducing the thermal energy requirements for the process. Experimental results for the poly(ethylene‐co‐propylene)‐hexane‐SCF ethylene system are shown as an example of the type of phase behavior observed with polymer‐solvent‐SCF additive solutions. Adding 20 percent (w/w) ethylene to the polymer solution lowers the temperature of the LCST by 109°C. The addition of 30 percent (w/w) ethylene to the polymer solution lowers the temperature of the LCST curve sufficiently to merge this curve with the upper critical solution temperature (UCST) curve. When the lower critical end point (LCEP) is plotted against the critical temperature of the solvent the data for poly(ethylenie‐co‐propylene)‐solvent systems are well represented by a single curve. A more fundamental modeling approach is needed to estimate the pressure of the LCEP and the concentration of SCF additive necessary to merge the LCST and the UCST curves. Patterson's theory of corresponding states can be used for these calculations.
Binary alloys of nylon 6 and ethylene‐methacrylic acid copolymers: Morphological, thermal and mechanical analysis
Authors: Macknight W. J. , Lenz R. W. , Musto P. V. , Somani R. J.
Published: December 2004

The morphology and mechanical properties of binary blends of nylon 6 (N6), as the major component, and ethylene‐methacrylic acid copolymers (E/MAA), as the minor component, have been analyzed. It was found that the methacrylic acid content of the copolymer used as the second component has a profound effect upon the properties of the resulting blends. In particular, with increasing methacrylic acid content, the size of the domains of the E/MAA dispersed phase in the N6 matrix decreased in a regular fashion while the ultimate tensile properties increased regularly. This behavior has been attributed to a series of chemical and physico‐chemical interactions taking place between the two components. The interactions are due to the presence of the acid functionality on the copolymer and do not occur when this functionality is absent. Chemical analysis of the blends was performed to confirm that chemical modification took place during the blending process.
Phase behavior studies of polyarylate/copolyester blends by thermal and dynamic mechanical analysis
Authors: Golovoy A. , Cheung M.‐F.
Published: December 2004

The phase behavior of polyarylate blends with a copolyester based on poly(1,4‐cyclohexanedimethylene/ethylene terephthalate) was studied by differential scanning calorimetry and dynamic mechanical analysis. A single glass‐transition temperature was observed over the entire composition range. Up to 30% weight polyarylate, the copolyester crystallized readily and its melting point did not change with blend composition. This indicates that transesterification, if it occurred, was negligible. The thermal and dynamic results also suggest a weak polymer‐polymer interaction in this system.
Microscopic studies of segmented urethanes with different hard segment content
Authors: Foks Janina , Janik Helena
Published: December 2004

The morphology of a series of segmented polyurethanes (PUs) has been characterized by means of optical and electron microscopies. Use of a two step replica from cryogenically fractured surface appeared to be a very useful technique to characterize the morphology of segmented PUs. The materials contain poly(ethylene adipate) glycol (PEA) as a soft segment and a hard segment derived from 4,4′‐diphenylmethane diisocyanate (MDI) and butane diol (BDO). Changes in morphology have been observed as a result of the increase of the hard segment content in the series of polyurethanes. The greater the proportion of the hard segment content, the greater the number of grain aggregates on the fracture surface in the sample under investigation. PUs with the hard segment content of 22% are not crystalline and have no grain aggregates on the fracture surface. PUs with the hard segment content above 50% are anisotropic in the whole volume under polarized light and their fracture surface is grainy over almost the whole area. Two types of grain aggregates dispersed in spherulite‐like matrix have been observed for PUs of 32–50% of hard segment content. Two types of the anisotropic structure in some PUs have been found. The comparison of microscopic and thermal analysis results shows the inhomogeneous distribution of the soft and hard segments in some PUs similar to that found by Chang, et al., in the PU system based on poly(propylene oxide) endcapped with poly(ethylene oxide) as a soft segment.
Knit lines structure in injection molding of nylon 6: Relation to first solidified sample cross section
Authors: Titomanlio G. , Piccarolo S. , Rallis A.
Published: December 2004

The effect of processing variables on the knit line structure of nylon 6 samples was investigated. Either local sample thickening or grooves were observed at the knit lines for samples injected with mold conditioning temperatures of 130° and 30°C respectively. The results also indicate that shrinkage venting, either to or from the weld zone, is the dominant mechanism for knit line formation, which is thus related to the position where complete cross section solidification first takes place.
Effect of shear modification on the rheological behavior of two low‐density polyethylene (LDPE) grades
Authors: Ritzau G. , Ram A. , Izrailov L.
Published: December 2004

Shear modification treatment represents a special shearing history affecting mainly the elastic behavior of polymer melts. This process has been attributed to reversible physical changes in the entanglement structure of the polymer chain network. Shear modification studies were performed for two well‐characterized low‐density polyethylene (LDPE) grades differing in molecular weight distribution and degree of long chain branching. The shear working of the material was carried out using a specially designed shearing unit producing definable amounts of pure shear in a continuous process. Measurements of the dynamic storage modulus, G′, steady‐state shear compliance; Je, extrudate swell, melt flow index, and the extensional behavior (Rheotens test) indicate that primarily properties associated with the elasticity of the melt are reduced in value. The observed reduction is found to correlate with the mean specific energy dissipated during sample preparation. Comparing the two LDPE grades showed that higher degrees of modification can be obtained at lower energy input levels for the more highly branched grade. Reversibility tests were performed and complete recovery of the initial material behavior was observed. Comparison of measurement results for samples prepared using the shearing unit presented here and a Brabender Plasticorder indicates that the degree of modification depends not only on the molecular structure of the polymer but also on the manner in which the shearing history is imposed upon the material.
Kinetic studies of a composite thermoset cure reaction—application in pultrusion simulations
Authors: Ng Hendra , Manas‐Zloczower Ica
Published: December 2004

A mechanistic kinetic model based on the concept of free radical polymerization and corrected for diffusion controlled reactions was used to describe the curing behavior of an unsaturated polyester resin. Kinetic parameters for the model were obtained from dynamic differential scanning calorimetry (DSC) scans using a multiple regression technique. The presence of kaolinite or fiber glass in the system does not affect the progression of the reaction. The results obtained from the kinetic studies were used to simulate the influence of system composition on temperature and conversion profiles inside a pultrusion die. The results of the simulations show that kaolinite and fiber glass act as heat sinks for the composite system reducing the peak exotherm and delaying curing progression.
Fracture behavior of oriented poly(ether‐ether‐ketone) (PEEK)
Authors: Wu Gwo‐Mei , Schultz J. M.
Published: December 2004

Poly(ether‐ether‐ketone) (PEEK) is a newly developed engineering thermoplastic with potentially vast application in advanced composites due to its exceptional performance. It is thus desired to understand the relationship between physical processing, microstructure and fracture in this semicrystalline polymer. Both oriented and unoriented PEEK were mechanically characterized using static test of three‐point bend specimens. The molecular chain orientation was imposed using a rolltrusion technique. The effects of thickness, strain rate, Initial crack length ratio, and orientation on fracture toughness (Kc) are investigated. The crystallinity is also examined by density measurement. The degree of orientation is determined qualitatively by wide‐angle X‐ray scattering diffraction patterns and quantitatively by further measurement using an image analysis system. Fractographic analysis, using scanning electron microscopy, provides precise information about the mode of fracture, Results indicate that both the modulus and the fracture toughness are remarkedly increased in the direction of drawing (T‐type) as opposed to the transverse direction (L‐type).
Dependence of melt temperature on screw speed and size in extrusion
Authors: Guo Y. , Chung C. I.
Published: December 2004

Melt temperature in an extrusion process can significantly influence production rate, product quality, and yield. However, prediction of melt temperature is extremely difficult because errors in the predictions of output rate, screw power, and heat transfer, which are used to calculate melt temperature, cumulatively cause a very large error in the prediction of melt temperature. This paper analyzed the overall energy balance of an extruder and developed a simple equation to predict the melt temperature of a projected extruder in scale‐up as a function of screw diameter, depth, and speed based on the experimental results of an experimental extruder and the polymeroperties. The predicted melt temperatures agreed reasonably with the measured values reported in a previous scale‐up study.
Alternate derivation of the effective medium conductance above and below the critical fill in a metal‐filled polymer
Authors: Schruben Dale L.
Published: December 2004

Herein is more detail to microscopic aspects of electron transport through a conductor‐filled polymer than has yet been considered in the literature (irrespective of quantum mechanical tunneling and thermal expansion). Some of these details only clarify earlier theories, but others lead to new discoveries such as the cubic conduction path coordination number z = 18 (contrasted with the classical geometric coordination number of z = 6). New also are simplified derivations of the high and low fill asymptotes of the master equation for conductance as a function of fill fraction in the effective medium theory of conductor‐filled polymers.
Orientation and crystalline morphology of blow molded polyethylene bottles
Authors: Choi Kyung‐Ju , Spruiell Joseph E. , White James L.
Published: December 2004

A study was carried out of the development of orientation during processing of conventional blow molded bottles made from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). The level of molecular orientation was found to be relatively low in all of the polyethylene bottles examined; it increased with increasing inflation pressure and decreasing extrusion temperature. Pole figures for the HDPE bottles indicated a slight a‐axis orientation toward the circumferential direction of the bottle. The b‐axes, which correspond to the lamellar growth direction, tend to be parallel to the bottle thickness direction. A comparison was made of the structure developed in blow molded bottles and blown films. The results for both films and bottles indicate that crystallization during processing involves both an increase in level of molecular orientation and an increased tendency toward biaxiality. Based on pole figures and small angle X‐ray scattering patterns, a morphological model for HDPE blow molded bottles is proposed.
Screw design in injection molding
Authors: Verbraak C. P. J. M. , Meijer H. E. H.
Published: December 2004

The performance of screws of advanced design in injection molding has been investigated with respect to four different objectives: (1) improvement of distributive mixing; (2) improvement of dispersive mixing; (3) increase of plasticating capacity; and (4) reduction of inhomogeneity of melt temperature.

The screws used are three zone screws with different compression ratios, screws with pineapple or Maddock/Egan mixing elements, with one or two channel barrier sections, with static mixers mounted in the valve or in the nozzle, or with combinations of these different elements. The best mixing quality is obtained with multi‐channel Maddock sections. The highest plasticating capacity and, consequently, the shortest cycle times are achieved with the barrier screws. Temperature measurements show that these screws improve melt homogeneity considerably with a relatively small loss of plasticating time. In all cases, increasing the back pressure gives inferior results compared with improvement of the screw design.
Acoustic emission behavior of epoxies during tensile loading
Authors: Hollmann K. , Hahn H. T.
Published: December 2004

The acoustic emission behavior during tensile loading of two common epoxy systems of different ductility was investigated at different loading rates. At low threshold voltage, it was possible to register acoustic emissions before the final failure. Only very few emissions were recorded compared with the amount commonly recorded for metals and composite materials. The acoustic emissions detected were of burst‐type, revealing a brittle damage accumulation process. They originated from the initiation and incremental growth of microcracks of stochastic nature. The events occurred before gross yielding and during the final “brittle” failure process. Basically no events were detected between gross yielding and the final failure during which large scale yielding, necking, and stable crack growth took place. The occurrence of events at the different loading rates was strongly influenced by the yielding behavior and fracture toughness, characterized by the yield stress σy and the plane‐strain fracture toughness KIc respectively. KIc was inversely dependent on the total number of events up to gross yielding. The event distribution normalized with respect to the conditions at gross yielding was hardly affected by the loading rate.
Plane‐strain fracture toughness of epoxies at different loading rates
Authors: Hollmann K. , Hahn H. T.
Published: December 2004

The plane‐strain fracture toughness of two common epoxy systems of different ductility were determined at different loading rates, according to ASTM E 399 for metallic materials. The ASTM standard was applicable, but underestimated slightly the specimen thickness required for KIc. KIc decreased with an increasing loading rate and with an increasing yield stress. The fracture surfaces were all very smooth as long as plane‐strain conditions prevailed.
Molecular design of multicomponent polymer systems. XV. Morphology and mechanical behavior of blends of low density polyethylene with acrylonitrile‐butadiene‐styrene (ABS), emulsified by a poly(hydrogenated butadiene‐b‐methyl methacrylate) copolymer
Authors: Fayt R. , Teyssié Ph.
Published: December 2004

The emulsifying activity of a poly(hydrogenated butadiene‐b‐methyl methacrylate) (HPB‐b‐PMMA) copolymer is investigated in incompatible blends of a low density polyethylene and poly(styrene‐co‐acrylonitrile) resins (mainly ABS) prepared in the melt state on a two‐roll mill. Optical and scanning electron microscopy observations clearly demonstrate that a moderate amount of copolymer (5 wt %) very significantly decreases the particle size and enhances interfacial adhesion. The block copolymer is also responsible for a strong improvement in both the ductility and Charpy impact resistance of PE/ABS blends.
Effect of titanate coupling agents on mechanical properties of mica‐filled polypropylene
Authors: Bajaj Pushpa , Jha N. K. , Jha Rajiv K.
Published: December 2004

The application of titanate coupling agents for the surface modification of mica filler and its reinforcement in polypropylene (PP) has been directed towards improvement in mechanical properties. Four titanate coupling agents, namely neoalkoxy tri(dioctylpyrophosphato) titanate (C1), neoalkoxy trineodecanoyl titanate (C2); bis‐(acetylacetonato)distearato titanate (C3), and bis‐(acetylacetonato)dipalmitato titanate (C4) were used in the present investigation. Mica powder (10 μm particle size) was coated with these coupling agents of varying concentration (0.5 to 1 % on the weight of filler) and then blended with polypropylene powder of 10 melt flow index. The mica (10 to 50 wt. %) filled polypropylene samples with and without coupling agents, were injection molded and the mechanical properties of the specimens tested. There is an improvement in the tensile, flexural, and impact strength of PP/mica samples coupled with titanates. The best performance in terms of yield stress and flexural strength was observed in PP/mica samples having 0.7% C1, titanate coupling agent. The fracture behavior of mica filled PP has also been studied using a scanning electron microscope.
Network mechanical properties of amine‐cured epoxies
Authors: Vratsanos Menas S. , Farris Richard J.
Published: December 2004

The technique of Impulse Viscoelasticity was used to characterize the network mechanical properties of amine‐cured epoxies during cure. The effects of amine molecular weight, functionality and stoichiometry were investigated. Among the properties which were obtained were the equilibrium tensile modulus, gelation time, cure and thermal stresses, volumetric changes during cure, glass transition temperature, thermal expansion coefficient, and molecular weight between cress‐links. It was found that these networks cured elastically and agreed closely with the predictions of rubber elasticity theory over a wide range of crosslink densities.
Highly sensitive novolak‐based X‐ray positive resist
Authors: Lingnau J. , Dammel R. , Theis J.
Published: December 2004

The application of X‐Ray lithography in mass production of devices is only economically viable if resist materials of highest sensitivity can be provided. Chemical amplification is the key concept to achieve such performance. It is outlined for a highly sensitive three component positive tone X‐Ray resist, consisting of a Novolak binder matrix, a starter compound, which—on X‐Ray exposure—yields an acid, which catalytically decomposes a dissolution inhibitor. Resist performance is discussed in terms of reaction kinetics and their implications on resist response, simulation, and handling procedures.
Silicon containing photoresists for half micron lithography
Authors: Sezi R. , Sebald M. , Leuschner R.
Published: December 2004

Several silicon containing topresists for bilayer oxygen reactive ion etching systems were developed and examined. Each topresist consists of a silicon containing alkaline soluble copolymer and a 2‐diazo‐1‐naphthalenone‐4‐sulphonic acid ester photoactive compond (PAC). Half micron structures in the topresist were obtained with two different resist systems through deep‐UV (257 nm) or iline exposure. The etch rate ratios (planarizing layer:copolymer) vary between 7:1 and 13:1 under anisotropic etching conditions. Linewidth loss during oxygen RIE (reactive ion etching) pattern transfer is a problem for resists containing about 10% silicon, but equal lines and spaces after etching can be obtained through the use of thick topresists or linewidth bias in the topresist prior to etching.
The chemistry of g‐line photoresist processes
Authors: Vollenbroek F. A. , Nijssen W. P. M. , Mutsaers C. M. J. , Geomini M. J. H. J. , Reuhman M. E. , Visser R. J.
Published: December 2004

The chemistry that underlies positive imaging, Image Reversal (ImRe) and Built In Mask (BIM), has been investigated. For this purpose the photoactive compound 2, 1 ‐diazonaphthoquinone‐5‐(4‐cumylphenyl)‐sulfonate (PAC‐5), the corresponding indenecarboxylic acid (ICA‐5) and the decarboxylated derivative of ICA‐5 (indene), were isolated and characterized. The study revealed that dissolution of ICA‐5 in aqueous base developers gives rise to the formation of an indenyl carboxylate dianion, which decarboxylates in several hours. In the case that ICA‐5 is dissolved in weakly alkaline media or in organic solvents such as methanol, the formation of this ion does not occur, but the rate of decarboxylation is almost the same. It is suggested that the decarboxylation reaction proceeds via the indene carboxylate monoanion, which reacts to indenyl anion. The latter is a strong base and is readily protonated to give indene (two isomers). In the case of aqueous base this leads to precipitation of the indene. In agreement with the finding that the indene derived from ICA‐5 does not dissolve in aqueous base developers, it was found that mixing indenes into novolak has a considerable inhibitive effect on the dissolution rate of a layer of this material in aqueous base. After a bake (in ImRe this would be the reversal bake), the dissolution rate is almost the same as for unexposed photoresist. Similar experiments with mixtures of novolak and indenecarboxylic acid revealed that there is no difference in the dissolution rate of such layers as compared with exposed photoresist. This excludes the putative effect of porosity, caused by nitrogen extrusion. In the case that 1‐phenyl‐3‐morpholinotriazene is added to the photoresist (in order to produce a dye in the BIM concept), azo‐dyes are formed by coupling of diazonium ions on the 1‐ and 3‐position of 3‐indenecarboxylic acid. The paper starts with a brief review of the mechanisms of photolysis of 2, 1 ‐diazonaphthoqui nones, as have been proposed in the literature. Although the formation of ketene as an intermediate is generally accepted, there appears to be no consensus about the existence of carbene.
Characterization of thermal behavior and kinetics of crystallization of a thermotropic rigid‐chain copolymer
Authors: Kamal M. R. , Khennache O. , Goyal S. K.
Published: December 2004

Thermal analysis was employed to estimate the heat of transition, equilibrium melting temperature and surface free energy of a thermotropic liquid crystal copolyester resin (70 mol% p‐hydroxybenzoic acid and 30 mol% 2,6‐hydroxynaphthoic acid). Specific heats and melting and crystallization behavior were evaluated using differential scanning calorimetry (DSC). Experiments over a wide range of cooling rates indicate two different crystallization processes: a rapid crystallization process and a slow crystallization process. The kinetics of the rapid crystallization process were evaluated using a non‐isothermal method. The analysis indicates that the rapid crystallization process can be suitably described by the non‐isothermal Avrami equation. The Avrami exponent is found to be equal to 2, which is in agreement with the nucleation and growth mechanism of the rigid rodlike molecules. The kinetics of the slow crystallization process, which were studied using an isothermal method, indicate that the degree of crystallinity varies linearly with log(time). The equilibrium melting temperature for this process is found to be 372°C. The Arrhenius plot yields a linear relationship in the lower temperature range.
The effects of cure temperature on the thermomechanical properties of UV curable coatings
Authors: Overton B. J. , Taylor C. R. , Muller A. J.
Published: December 2004

A method is presented to study the mechanical behavior of soft, UV curable coating material as a function of temperature of the prepolymer at cure. For such materials, the crosslink density (hence, equilibrium modulus) is found to decrease with increasing cure temperature. The three primary coatings are: a polyurethane acrylate with a nominal equilibrium tensile modulus of 200 psi, a polyurethane acrylate with a nominal equilibrium modulus of 1200 psi, and a non‐urethane acrylate with a nominal equilibrium tensile modulus of 60 psi.
Fire resistant optical cables with special plastic coated fibers
Authors: Suzuki H. , Tsujita T. , Shamoto N. , Inada K.
Published: December 2004

It is important to prevent transmission loss increase of optical fiber cables during a fire and fire fighting. One of the main reasons for the loss increase in a fire is the expansion and shrinkage of polymers used in optical fiber cables. The authors have developed a fire resistant optical fiber cable by studying the behavior of coating materials and coated fibers at high temperature. Polymer types investigated are thermoplastics, engineering plastics, and UV cured plastics. The fire resistant optical fibers are coated with a polymer which rapidly produces a carbonized layer by exposure to heat. The rapid carbonizing has the effect of reducing expansion and shrinkage. Besides the coating, the coated fiber is surrounded by carbon yarn to prevent breakage of the fiber. The fire resistant optical fiber cable passed the fire test at 840°C for 30 minutes and VTFT specified IEEE 383, without any breakage of the fibers. The optical loss of the fibers scarcely changed during the tests and after the tests. This paper presents the studies of coating materials and coated fibers at high temperature, the structure and properties of the coated fiber and characteristics of the fire resistant optical fiber cable.
Polymers for optoelectronics
Authors: Kaino Toshikuni , Katayama Yuzo
Published: December 2004

This paper discusses polymers for optoelectronics, especially plastic optical fibers (POFs) for near‐infrared (near‐IR) use and polymeric nonlinear optical materials expected for use as switching devices. Near‐IR transmissible plastic optical fibers are investigated using fluorination and deuteration for conventional polymers. Among them pentafluoro‐trideutero‐styrene polymer core POF has excellent transparency in the near‐IR region even after water vapor absorption. Nonlinear optical polymeric materials with excellent processibilities are also investigated. The third‐order nonlinear optical susceptibility of poly‐aromatic vinylene thin film was measured and revealed to have a higher susceptibility than previously reported.
Optical fiber chemical sensors utilizing dye‐doped silicone polymer claddings
Authors: Blyler L. L. , Lieberman R. A. , Cohen L. G. , Ferrara J. A. , Macchesney J. B.
Published: December 2004

Transparent dimethyl siloxane network polymers with refractive indices near 1.40 may be applied to fused silica fibers (n = 1.458) as they are drawn to produce plastic‐clad silica (PCS) optical fibers. The evanescent tail of the light energy propagating in the core of such fibers extends into the silicone cladding, where it interacts with chemical species present in the polymer. If the silicone is doped with a dye, the absorption spectrum or fluorescence spectrum of the dye is reflected in the transmission spectrum of the fiber. Further, if the dye changes its absorption spectrum or fluorescence spectrum as a result of diffusion of a chemical species into the silicone, the change is detectable in the fiber output. The polymer material properties which determine the performance of these sensors are described, along with examples of sensors for ammonia and oxygen which utilize either color changing or fluorescent dyes.
Thermal interactions in oriented polymeric materials: Shrinkage, crystallization, and melting
Authors: Sun D. C. , Magill J. H.
Published: December 2004

Thermal analysis of oriented polymers involves several transitional processes which may be coupled in a complex way. The disorientation process that occurs during heating is often accompanied by dimensional shrinkage which may occur in both amorphous and crystalline oriented polymers. From differential scanning calorimetry (DSC) measurements it has been determined that shrinkage is an exothermic process. In amorphous atactic polystyrene (PS), hot drawn uniaxially, the shrinkage occurs just above Tg. In triaxially oriented polyethylene (PE) and isotactic polypropylene (iPP), shrinkage and melting take place concomitantly, producing multiple melting peaks. In rolltruded (and also in biaxially oriented) poly(ethyleneterephthalate) (PET) films, shrinkage and crystallization are found to be coupled and to occur between Tg and Tm upon heating. If the enthalpy contribution due to shrinkage is ignored, it follows that crystallinities determined by DSC are incorrect. In this study, the influence of shrinkage upon transitional changes in oriented polymers is investigated in a systematic manner.
Temperature‐dependent mechanical properties and constitutive equation of cellulose nitrate
Authors: Nishitani T. , Ogura H.
Published: December 2004

The strain‐time response under tensile loading (creep tests) and the stress strain response under constant tensile stress rate (proportional loading tests) have been evaluated at 4 temperatures 20, 45, 55, and 65°C, for samples of cellulose nitrate. A time‐dependent constitutive equation (or stress‐strain relation) for the nonlinear visco‐elastic material is deduced from invariant theory with a hypothesis of a creep potential. The procedure for determining the seven material constants involved in the deduced constitutive equation is described for the creep and proportional loading tests and the variation of these constants with temperature is presented. The deduced constitutive equation gives good agreement with the actual observations for the creep and proportional loading tests, independent of the values of temperature, creep stress, or stress rate.
Curing and constitutive relationships for polyester mortar
Authors: Vipulanandan C.
Published: December 2004

The compressive and tensile properties of polyester mortar were studied under various curing conditions, temperature, and strain rate. The curing temperature was varied from room temperature to 80°C. The behavior of polyester mortar was studied using a uniform sand with strain rate and temperature varied between 0.01 to 6 percent strain per minute and 22°C and 120°C, respectively. The strength, failure strain, modulus and stress‐strain relationships of polyester mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of polyester mortar are quantified. Pretreating the aggregates with a silane coupling agent further enhances the compressive and tensile strength of the mortar. The compressive modulus and splitting tensile strength of polyester mortar are related to the compressive strength. A constitutive model is used to predict the compressive stress‐strain behavior of polyester mortar.
Thickness effects in the vibration welding of polycarbonate
Authors: Stokes Vijay K.
Published: December 2004

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. Past work on welding characterized the effects of weld parameters such as the weld frequency, the weld pressure, and the weld time, on the welding process and weld strength, and showed that the most important parameter affecting weld strength Is the weld penetration—the decrease in the distance between the parts being welded that is caused by lateral outflow of material in the molten film. However, those weld studies were based on specimens of constant nominal thickness (6.35 mm, 0.25 in). This paper is concerned with the effects of specimen thickness on the weld process and weld strength.
Time and temperature dependent sorption in poly‐ether‐ether‐ketone (PEEK)
Authors: Mensitieri G. , Del Nobile M. A. , Apicella A. , Nicolais L.
Published: December 2004

The possible multimodal sorption mechanisms in glassy amorphous poly‐ether‐ether‐ketone (PEEK) are presented. By varying the penetrant‐polymer affinity, experimental temperature, and external solvent activity, a broad range of sorption behaviors from ideal Fickian diffusion to limiting relaxation controlled kinetics is observed. In particular, water, methylene chloride, and n‐heptane sorption kinetics are analyzed and interpreted on the basis of the multiple transport mechanisms. Low uptake liquid n‐heptane sorption follows ordinary Fickian diffusion. Analogously, water vapor at low activity, is sorbed in small amounts in the same limiting mode while, at higher activities, the moderately higher penetrant uptakes induce slow relaxation coupled with ideal Fickian diffusion. The highly interacting methylene chloride leads to ideal Fickian diffusion only at very low activities, while anomalous non‐ideal Fickian diffusion and limiting Case II and diffusion controlled swelling are observed at moderate and at high solvent activities, respectively. Limiting Case II sorption of methylene chloride in PEEK has been observed only at a very low temperature (−32°C). The optical microscopy observations of cryogenically fractured samples contacted with liquid methylene chloride at 5, 20 and 36°C revealed the presence of a sharp front moving linearly with the square root of time. Solvent induced crystallization in methylene chloride swollen samples was detected by means of differential scanning calorimetry (DSC) and wide angle X‐ray scattering (WAXS). Finally, sorption from liquid methylene chloride/n‐heptane solutions with varying compositions are presented. The progressive increase of the more high sorbing methylene chloride concentration in the solutions, leads to the same wide variety of sorption behavior observed in the methylene chloride vapor sorptions. The gas chromatographic (GC) analysis indicated that the presence of methylene chloride enhanced the n‐heptane sorption in the polymer.
The breaking strength of perfect polymer fibers
Authors: Smith K. J.
Published: December 2004

The breaking strength, strain at break, and work to rupture of perfect fibers prepared with polymers of finite molecular weight are calculated by treating the perfect fiber as a stressed crystal undergoing a crystal‐melt phase transition. In this view, a tensile load destabilizes the crystal and depresses its melting point. When the load is sufficient to lower the melting temperature to the ambient condition the fiber melts—i.e., fails. The theoretical equations (extremely simple) are applied to several common polymer fibers. The maximum tensile strength of polyethylene, for example, is calculated to be 7 to 9 GPa, in good agreement with current experimental results.