bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction kinetics of polyurethane‐polyester interpenetrating polymer network in the bulk polymerization
Authors: Hsu T. Jeffrey , Lee L. James
Published: December 2004

Kinetics of simultaneous interpenetrating networks (SIN) composed of a polyurethane resin (PU) and an unsaturated polyester resin was studied. A differential scanning calorimeter (DSC) was used to monitor the polymerization course. It was found that increasing the polyester content in a PU‐polyester SIN enhanced the polymerization of PU due to the “solvent effect” of polyester. On the other hand, increasing the PU content in the SIN retarded the polymerization of polyester due to the “cage effect” of PU. Polymerization sequence of the SIN could be controlled by employing different initiators for polyester reaction. The degree of crosslinking in each SIN component had a significant effect on the dynamics of the SIN formation and on the limiting conversion of the polyester reartion.
Shear and extensional flow of reinforced plastics in injection molding. II. Effects of die angle and bore diameter on entry pressure with bulk molding compound
Authors: Gibson A. G. , Williamson G. A.
Published: December 2004

Orifice flow measurements have been performed at high strain rates on bulk molding compound (BMC) using convergent dies. A range of die angles and bore diameters was examined. Two models for flow behavior have been compared. It appears that, with BMC, there is a transition from constrained convergence to convergence with recirculation at a die semiangle of approximately 56 degrees.
Phase diagrams as a formulation guide in aqueous polymer/surfactant systems
Authors: Lochhead R. Y. , Warfield D. S. , Gasiewski C.
Published: December 2004

Polymers are often formulated into detergent products in order to confer properties which facilitate processing and/or storage of the product, or to yield desirable attributes for the end‐user. Carbopol resin which consists essentially of polyacrylic acid, is one such polymer. Carbopol resin systems exhibit Bingham‐Body‐type rheology with measurable yield‐value and pronounced shear‐thinning at shear stresses above the yield value. These properties render Carbopol resins useful as a thickener and a suspending agent. Interaction with other components in a formulation, however, can radically alter the thickening and suspending properties of Carbopol resins. Phase diagrams of Carbopol resins with other major components of the system can guide the formulator away from areas where undesirable interactions, such as coacervate formation, can occur, and when presented in the form of contour diagrams they quantitatively map the physical properties of interest, enabling the formulator to be guided directly into the composition region which will best satisfy his requirements. The phase diagrams can also predict when different desirable properties cannot be simultaneously achieved and they can define the extent of compromise which may be necessary in formulation of the final product.
Equations of state of polymer
Authors: Cho Bongkee
Published: December 2004

Equations of state for polymers above and below the glass transition temperature are derived. Comparisons of the predicted P‐V‐T relations with the experiment are quite favorable. From the obtained equations, both the Anderson‐Grüneisen constant and the Grüneisen constant can be determined, and the Tait equation is derived.
A kinetic study of the activated anionic polymerization of ε‐caprolactam
Authors: Lin D. J. , Ottino J. M. , Thomas E. L.
Published: December 2004

The diversities existing among published kinetic studies on activated anionic polymerization of ε‐caprolactam are closely examined. A kinetic model derived from a regular, linear reversible reaction mechanism is employed to explain the experimentally observed autocatalytic character of the polymerization system and to examine the dependence of the apparent activation energy on the experimental method. Several existing kinetic models tested with our experimental data show that the autocatalytic type rate equation best describes the polymerization process.
Three‐dimensional solidification and flow of polymers in curved square ducts
Authors: Ahmadian M. T. , Burmeister L. C. , Johnson R. W.
Published: December 2004

Steady three‐dimensional laminar flow with and without partial solidification of an initially molten polymer in square ducts, both straight and with a 90‐degree curve, was numerically studied with a version of the SIMPLE algorithm. The non‐Newtonian characteristics of the fluid polymer were represented by a power‐law model. The temperature variation of fluid properties was taken into account. Viscous dissipation, being significant for all flow regimes studied, provided thermal energy input which was balanced by heat transfer outward across duct boundaries. For the non‐Newtonian fluid with solidification and variable viscosity, it was found that the effective heat transfer coefficient in the curved section of the square duct is larger than in a straight section; in the curved section, this coefficient is larger at the outside of the bend than at the inside. These findings are in agreement with measurements reported in the literature for similar situations. The combined mechanisms of solidification on the wall and viscous dissipation result in the possibility of two different flow rates for a specified pressure gradient. The flow channel that remains unfrozen in a curved square duct meanders within the confines of the duct much as a river meanders in its valley; the wave length of the meander is sensitive to the fluid flow rate and radius of curvature.
Bubble growth controlled devolatilization in twin‐screw extruders
Authors: Foster R. W. , Lindt J. T.
Published: December 2004

An experimental study of polymer soluticn devolatilization in a counterrotating twin‐screw extruder has been undertaken. In an effort to ultimately predict mass transfer rates in such a process, this work analyzes the experimental results to determine the controlling mechanisms in the separation of volatile components from the polymer. The devolatilization process at hand encompasses the heavily foaming and nonfoaming regimes. Historically, the literature has centered primarily around the highly concentrated, bubble‐free diffusion‐controlled devolatilization regime. The analysis presented in this paper centers on the performance of the heavily foaming stages of the process. Recent and previously reported (1) data on the polystyrene/ethylbenzene (PS/EB) system, as well as newly collected data on the poly(methyl methacrylate)/methyl methacrylate (PMMA/MMA) system, are analyzed. In the foaming stages of the process, two regimes have been found. These regimes are differentiated by the availability of volume into which the foam can grow. Deformation and mixing effects appear to be secondary. Furthermore, temperature changes across the range of realistic operating conditions appear to affect mainly the thermodynamic driving force. It is only at extremely high temperatures that these effects are truly controlling.
Properties of elongational flow injection‐molded polyethylene part 2: Influence of processing parameters
Authors: Cabarcos E. López , Bayer R. K. , Zachmann H. G. , Calleja F. J. Baltá , Meins W.
Published: December 2004

In the first part of this series, the influence of mold geometry was examined with reference to the improvement of the mechanical properties of elongational flow injection‐molded polyethylene. In the present study (Part 2), processing parameters have been investigated and the physical properties of the moldings examined. It is confirmed that mainly two parameters, the temperature of the melt and the pressure on the solidifying mold, govern the injection process. Results are discussed in terms of the molecular orientation that is developed during the filling process and depends on the temperature of the melt. The application of high pressures leads to a pressure‐induced crystallization effect that freezes in the molecular orientation within the mold.
Microstructural diagnosis of block copolymer nonlinear mechanical properties. II: Free recovery from large tensile deformations
Authors: Diamant Joram , Williams Michael C.
Published: December 2004

Three styrene‐butadiene‐styrene (SBS) block copolymers were cast into sheet form, and the resulting microphase‐separated specimens were tested in tensile free recovery. After an initial strain of 300%, specimens were released and their lengths measured for about a week. For one polymer, the recovery curves are presented for seven temperatures in the range −40 to +80°C; other data are given at 22°C. Analysis of the recovery curves, using as the model a series assembly of Kelvin elements, obtains time constants for microstructural repair and explains the temperature dependence in terms of the microstructural interphase and its partial vitrification. Differences among the three polymers can be interpreted by recognition of styrene‐block molecular weights, as well as by the volume fractions of the domain styrene cores and interphases. Additional structural information arises from torsion pendulum experiments over −120 to 100°C for unstretched, stretched (300%), and partially recovered samples.
Physical properties of blends of polycarbonate and a liquid crystalline copolyester
Authors: Nobile M. R. , Amendola E. , Nicolais L. , Acierno D. , Carfagna C.
Published: December 2004

Blends of polycarbonate (PC) and poly(ethylene terephthalate‐co‐p‐oxybenzoate) (PET/PHB60) were prepared by melt‐blending. Physical and/or chemical interactions between the two phases of the system were studied by thermal analysis and infrared spectroscopy. Rheological measurements in shear flow were carried out both in the low and high shear rate regions in the temperature range of the existence of the mesophase. At low liquid crystalline polymer (LCP) content, the blends showed flow curves similar to those of the unfilled PC, while at higher LCP percentages the rheological behavior of the pure LCP was resembled. Moreover, in the whole shear range, the viscosity values of such blends were in between those of the pure polymers. The influence of the addition of 10% LCP on the mechanical properties of the PC was investigated. Fiber‐spinning was performed under different experimental conditions, and it was found that opportune drawing conditions are necessary to improve the modulus of the matrix. Morphological analyses of the pure LCP and of the blends were related to the rheological and mechanical behavior of these systems. While the LCP exhibited an elevated dimensional stability, the inclusion of the LCP in PC matrix did not improve the dimensional stability of the blends.
Cold compaction and sintering of ultrahigh‐molecular‐weight polyethylene containing a segregated iron network
Authors: Krishnamurthy V. , Kamel I. L.
Published: December 2004

To improve the powder processing behavior of ultrahigh‐molecular‐weight polyethylene, a conductive iron filler was distributed within the polymer in a segregated network. The filler level was kept at a minimum of 10 volume percent, which was sufficient to coat completely all the polymer particle surfaces. This filler level was low enough to avoid modifying the resin properties to a significant extent. Compaction of these filled samples showed a slower densification, under pressure, similar level of final densification at 80% densification parameter, and a doubling of plateau pressure value to 200 MPa in comparison with the unfilled polymer. The filler was found to reduce drastically the postcompaction relaxation time from 24 h to 6 h. The magnitude of the axial (compaction direction) relaxation was unchanged, but the radial relaxation was one quarter of that for the unfilled polymer. Sintering behavior showed improved densification because of lower dimensional changes during sintering resulting in 80% relative sintered density, higher than the 75% percent value for the unfilled polymer, but yielded a 20% lower sintered strength, An alternative process of rapid sintering by induction heating was explored, its feasibility demonstrated, and a recommendation is made to make powder processing of this polymer commercially attractive.
Intermolecular interactions and phase transition behavior of miscible polymer blends
Authors: Chee K. K.
Published: December 2004

A linear equation is proposed to quantify the glass transition behavior of miscible polymer blends in terms of the polymer‐polymer interaction density parameter whose values are obtainable from the melting point depression method. This practical model is successfully applied to four series of binary polyblends containing poly(hydroxy ether) of biphenol A, poly(vinyl chloride), poly(vinylidene fluoride), and poly(2,4‐dimethyl‐1,4‐phenylene oxide) as the common components. Each of these groups of polymer systems exhibits a distinct type of intermolecular interaction that can be characterized by the two coefficients of the model equation. In connection with the present analysis, three novel expressions are introduced for describing the glass transition temperature—composition relations of the polymer systems of interest.
Structure of PPTA fibers derived directly from a liquid crystalline prepolymer dope in an organic solvent
Authors: Jin Jung‐Il , Park Ho‐Jin , Rhim Moo‐San , Kim Si‐Min
Published: December 2004

The structure and properties of the pulp‐like aromatic polyamide PPTA fibers prepared directly from a polymerization medium were studied by scanning electron microscopy (SEM), X‐ray diffractometry, and polarizing light microscopy. The morphology of the fiber appears significantly different from that of Kevlar and does not reveal a skin‐core structure. Regular defect bands and, thus, the regular clustering of the chain ends also could not be observed.
Novolac‐Based photoresists combining chemical amplification and dissolution inhibition
Authors: O'brien Michael J.
Published: December 2004

This paper concerns a more in‐depth examination of the different components which make up positive photoresists based on the combined principles of chemical amplification and dissolution inhibition. Included is a discussion of the requirements for materials to be used as dissolution inhibitors in this scheme as well as an example of an optimum compound‐t‐butyl‐cholate. Also considered are the effects of onium salt counteranions on resist performance including gel permeation chromatographic (GPC) analyses of the changes in novolac molecular weight distribution which can occur during irradiation and postbake.
A negative resist for KrF excimer laser lithography
Authors: Toriumi M. , Hayashi N. , Hashimoto M. , Nonogaki S. , Ueno T. , Iwayanagi T.
Published: December 2004

The design and preparation of a series of negative resists for KrF excimer laser lithography are described. Each resist is composed of poly(hydroxystyrene) and an aromatic azide. The base resin shows high transmittance of 62%/μm at 248 nm, when p‐ethylphenyl p‐azidophenylsulfonate. 4‐azido‐4α‐methoxy‐chalcone, 1‐(4 azidobenzylidene)‐3‐(α‐hydroxy‐4‐azidobenzyl)‐indene, 4,4α‐diazido‐3,3α‐dimethoxybiphenyl, or 1‐(4‐azidostyryl)‐5, 5‐dimethyl‐2‐cyclohexen‐1‐one is employed as a sensitizer. These azides are obtained by red‐shifting the absorption maxima to lower energy regions than the exposing wavelength of 248 nm. Transmittance of resists can be controlled from 10 to 30%. The resist is exposed with a KrF excimer laser stepper and developed in an alkaline solution. Sensitivities of about 15 mJ/cm2 are observed. A good, subhalf‐micron resist profile is achieved.

The photochemical reaction mechanisms of poly(hydroxystyrene) and 4,4α‐diazido‐3,3α‐dimethoxybiphenyl were studied at 248 nm and 313 nm exposure. Quantum yield for photodecomposition at 248 nm is seven times larger than that at 313 nm, but dissolution‐inhibition effects are larger at 313 nm exposure. Consequently, the resist shows higher sensitivity at 313 nm than at 248 nm.
Epoxy resins for deep UV lithography
Authors: Stewart K. J. , Hatzakis M. , Shaw J. M.
Published: December 2004

A negative resist based upon photo‐acid initiated cationic polymerization of an epoxy resin (1, 2) was reported in the early eighties with the advent of onium salts (3–5). An efficient acid generating onium salt, triphenylsulfonium hexafluoroantimonate (6), absorbs light in the deep UV producing acid upon direct photolysis in this region of the spectrum. The resin component of such a negative resist system must be optically transparent over the exposure wavelengths to obtain vertical image profiles. Another difficulty often encountered with crosslinking negative resists is swelling of the crosslinked matrix during development with organic solvents. This swelling manifests itself in distorted images and/or complete adhesion loss, especially when submicron features are involved. Our goal has been to address these problems and develop an organic developable deep UV resist capable of providing submicron images. Optically transparent commercial resins, styrene‐allyl alcohol copolymers, have been converted to glycidyl ethers, thereby providing cationically polymerizable functionalities. Careful choice of the resin was made to obtain reactive ion etch resistance, thermal stability, good adhesion, and coating properties. The synthetic procedure and characterization of the epoxy resin will be presented. The effect of the molecular weight distribution upon swelling during development and general solubility properties also will be discussed. Resist formulations exhibited sensitivities of 19 to 30 mJ/cm2 on a Perkin Elmer 500 in the deep UV (UV2) mode. The electron beam sensitivity is 3 to 5 μC/cm2 at 20 KeV. Submicron images have been generated in both optical and electron beam lithography.
Poly(Aryline imides) as E‐beam resist: Sensitivity and resolution
Authors: Chien James C. W. , Gong B. M.
Published: December 2004

Polyamic acids synthesized from di‐trifluoromethyl methane bis(phthalic anhydride) and 4,4'‐diaminophyenyl sulfone (F‐1) and 4,4'‐diaminophenyl ether (F‐4) were found to have excellent negative E‐beam resist properties. The best materials contain about 90 percent imidized structural units having sensitivities of 1.5 to 2.5 μC cm−2 and contrast of 1.0 to 1.3. Polyamic acid of pyromellitic dianhydride and 4,4'‐diaminophenyl sulfone (P‐1) imidized to 97 percent exhibits useful positive E‐beam resist properties. Radiation induces imidization and chain scission to alter the solubility of the resist polymers resulting in the formation of latent images.
New high temperature stable positive photoresists based on hydroxy polyimides and polyamides containing the hexafluoroisopropylidene (6‐f) linking group
Authors: Khanna D. N. , Mueller W. H.
Published: December 2004

In this paper we describe the synthesis, characterization, and lithographic evaluations of novel positive photoresists based on hydroxy polyimides and polyamides containing 6‐F linking groups. The polymers were synthesized using solution condensation techniques and characterized using solution viscosity, GPC, FTIR, NMR, UV, TGA, and DSC. Tg's of these polymers range from 250 to 300°C. Both polyimides and polyamides are soluble in a variety of solvents commonly utilized for photoresist applications. When formulated with diazonaphthoquinone sensitizers, these polymers provide an improved high‐temperature resistant, aqueous base developable positive photoresist system with good photospeed, contrast, and resolution characteristics. High resolution relief images were obtained which are comparable to 1300 Series AZ type photoresists. No thermal deformation, loss in resolution or defects were noticed when relief patterns were annealed to 250°C. Additionally, the hydroxy polyamide based resists, when thermally annealed to 300°C, provide a photoresist system with even higher thermal stability (400 to 450°C) and excellent resistance to solvents. Also, the photoresist formulations have excellent storage stability at room temperature and can be processed like conventional positive photoresists using broad band UV radiation sources.
Design and analysis of a dual‐cavity coat‐hanger die
Authors: Lee Kwong‐Yang , Liu Ta‐Jo
Published: December 2004

A method for the design and analysis of a dual‐cavity coat‐hanger die is presented in this paper. A macroscopic material balance and a microscopic flow analysis using the finite element method are combined to simulate polymeric fluid flow inside the die. Leonard's macroscopic procedure was adopted to include inertial, gravitational, and viscous effects, and the finite element method was then applied to estimate the contributions of inertial and viscous terms. In addition, the flow patterns in the outer cavity were computed by the finite element method so that the appearance of an undesirable vortex could be predicted. The residence time distributions for flow in the die were approximated by a simple, statistical approach. It was found through a case study that a dual‐cavity coathanger die can effectively reduce the flow non‐uniformities caused by fluid inertia and viscosity variations.
Time temperature dependence of dual coated lightguide pullout measurements
Authors: Overton B. J. , Taylor C. R.
Published: December 2004

The strength of the bond between primary coating and glass for a dual coated lightguide may be judged by fixing the coating to a substrate and pulling the glass out. The values obtained from such measurements are shown to exhibit a temperature and rate dependence similar to the mechanical properties of the primary coating for a given coating system. Here we combined temperature and rate data for a universal description of the coating to glass adhesion for a dual coating system.
Microstructure and ultimate properties of injection molded amorphous engineering plastics: Poly(ether imide) and poly(2,6‐dimethyl‐1,4‐phenylene ether)
Authors: Wagner Alan H. , Yu Jeong S. , Kalyon Dilhan M.
Published: December 2004

Specimens of two engineerig plastics i.e., poly(ether imide), PEI, and poly(2,6‐dimethyl‐ 1,4‐phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The mold and melt temperatures and the injection speed were varied in a limited range which furnished acceptable samples. The density, birefringence, residual stress distributions, flexure and tensile properties, and crack development of the injection molded specimens were studied. Vacuum compression molded samples were also prepared to investigate the role played by the cooling rate in shaping microstructural distributions. The results revealed significant differences in the development of microstructure of the molded specimens of the two resins, which was related to rheology and molding conditions on one hand and to development of cracks and ultimate properties on the other hand.
Joining methods for plastics and plastic composites: An overview
Authors: Stokes Vijay K.
Published: December 2004

Joining of plastics and plastic composites is becoming important because of the emerging structural applications of these materials. While providing an overview of all joining methods, this paper emphasizes the welding of thermoplastic materials. Different welding techniques, together with their main advantages and disadvantages, are briefly described. A selective bibliography, in which the 259 references have been arranged chronologically for each technology type, provides a guide to the literature.
Morphological and mechanical property studies of polymer extrudates obtained by the rotational extrusion process
Authors: Chung B. , Zachariades A. E.
Published: December 2004

The orientation of the reinforcing fibers in glass fiber filled polypropylene tubular extrudates has been controlled effectively by the superposition of the linear flow in a melt extruder with torsional flow generated by rotating the capillary portion of the extrusion die of the extruder. The so produced extrudates have mechanical properties which can be balanced along the hoop and extrusion direction by adjusting the extrusion rate and the rotational speed of the die for example, the breaking load of 75N along the hoop direction increases by ∼40% when the capillary of the die was rotated at 80 rpm. At the same time the Young's modulus in the extrusion direction decreased from 1100 MPa under conventional extrusion conditions to 800 MPa.
Orientation and mechanical properties of polycarbonate‐ linear low density polyethylene blends
Authors: Ajji Abdellah
Published: December 2004

Five blends of polycarbonate (PC) with linear low density polyethylene (LLDPE) were studied. Characterization of the blends was made by means of rheological measurements and domain morphology determined by SEM microscopy. A fine dispersion was obtained for the 25/75 PC/LLDPE. The blends were then oriented, LLDPE and 25/75 PC/LLDPE at room temperature, and the others at 165°C. For the hot drawn blends (50/50 and 75/25 PC/LLDPE), a significant increase in tensile strength and elongation at break is observed. For the room temperature drawn samples, modulus and tensile strength values increase whereas elongation at break decreases. This is explained in terms of morphological and molecular orientation effects. Comparison of the experiments to the predictions of different models for the modulus shows a good agreement for unoriented blends. However, for oriented samples, important discrepancies are observed, suggesting that the morphology and orientation are important factors in predicting the modulus of these blends. A model which takes into account these factors is proposed and a good fit of the modulus is obtained.
Scale‐up laws in heated tool butt welding of HDPE and PP
Authors: Potente H. , Tappe P.
Published: December 2004

In order to achieve high fatigue strengths in heated‐tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated‐tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small‐pipe to large‐pipe welds are then based on the values of these nondimensional numbers.
Process data acquisition in vibration welding of thermoplastics
Authors: Potente Helmut , Kaiser Harald
Published: December 2004

A measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time‐dependent signals that describe the process—such as the frequency‐dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane—and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.
Ultrasonic welding of thermoplastics in the near‐field
Authors: Benatar Avraham , Eswaran Raman V. , Nayar Satinder K.
Published: December 2004

Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near‐field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near‐field ultrasonic welding of amorphous (acrylonitrile‐butadiene‐styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.
Interrelationships between selected mechanical properties of individually‐tested polymeric fibers
Authors: Ellison M. S. , Zeronian S. H. , Alger K. W. , Aboul‐Fadl S. M. , Soler T. M.
Published: December 2004

Although fibers are subject to complex deformations during processing and end use, most research has concentrated on tensile properties. We have extended our studies to include the ultimate torsional properties, i.e., the breaking twist angle (BTA), and the flexural fatigue life of single fibers. We now have sufficient data on diverse fiber types that we may compare their mechanical properties. Thus, in this paper we report the mechanical properties of the different starting, untreated, fibers, tested under fiducial conditions. We then develop and consider some interrelationships between these selected single fiber physical properties.
Relationship between electron sensitivity and chemical structures of polymers as electron beam resist. VII: Electron sensitivity of vinyl polymers containing pendant 1,3‐dioxolan groups
Authors: Oguchi Kiyoshi , Sanui Kohei , Ogata Naoya , Takahashi Yoichi , Nakada Tomihiro
Published: December 2004

Vinyl polymers containing pendant acetal groups were synthesized using (2,2‐dimethyl‐l,3‐dioxolan‐4‐yl)methyl acrylate (DMA) and (2,2‐dimethyl‐l,3‐dioxo‐lan‐4‐yl)methyl methacrylate (DMM), and were evaluated as negative electron beam (EB) resists. It was found that the EB sensitivity of polymers containing acetal groups in the side chain was higher than that of polymers containing acetal groups in the main chain. A high sensitivity of 3.6 × 10−8 C/cm2 was observed. Copolymers of DMA or DMM with styrene were also synthesized in order to improve the durability for dry etching process. It was found that the copolymers had an excellent dry etching durability and were adaptable to EB lithography.
Physical properties of perfluoropolyethers: Dependence on composition and molecular weight
Authors: Marchionni G. , Ajroldi G. , Cinquina P. , Tampellini E. , Pezzin G.
Published: December 2004

Three copolymeric perfluoroethers with the structure CF3[(OCF2CF2)p(OCF2)q] OCF3, having different p/q ratios, have been fractionated. The fractions obtained have been characterized by Gel Permeation Chromatography and 19F‐NMR. The viscosity η the specific volume v and the glass transition temperature, Tg have been measured by standard techniques for all the above samples as well as for some other perfluorinated polyethers.

The temperature dependence of viscosity of the unfractionated samples is described by the W.L.F. equation. The values of fg (fractional free‐volume at Tg) and of af (free‐volume expansion coefficient) are independent of composition, for p/q ratios from 0.53 to 1.15. The critical molecular weight, Mc, is of the order of 8–9,000. From the molecular weight dependence of specific volume, the contribution to the molar volume of the in‐chain CF2 group and the excess molar free volume of the chain ends have been determined. The limiting value of Tg for an infinite molecular weight polymer was found to depend linearly on the compositional ratio O/C and the extrapolated values for polytetrafluoroethylene and for the homopolymer (CF2O)n were found to be respectively 200 K and 120 K.
Microspheres and microcapsules, a survey of manufacturing techniques: Part III: Solvent evaporation
Authors: Arshady Reza
Published: December 2004

A methodological survey of microsphere formation and microencapsulation techniques based on solvent extraction/evaporation techniques is presented. Thus, basic features of solvent extraction and solvent evaporation processes, including droplet formation, droplet/particle stabilization, and solvent removal, are outlined. Preparation of a wide range of microspherical and microcapsular products based on biodegradable polyesters, polysaccharides, and nonbiodegradable polymers are discussed. Dependence of microcapsule characteristics on manufacturing parameters, as well as performance evaluation of microspherical and microcapsular products, are also briefly covered.
Differential scanning calorimetry analysis of thermoset cure kinetics: Phenolic resole resin
Authors: Focke W. W. , Smit M. S. , Tolmay A. T. , Van Der Walt L. S. , Van Wyk W. L.
Published: December 2004

The Differential Scanning Calorimetry (DSC) trace for a commercial phenolic resole resin shows two distinct peaks. Assuming that these represent two independent cure reactions results in a kinetic model of the form:

with κi = κio exp(‐Bi/T).

The Arrhenius parameters were estimated from a plot of ln(β/T) versus 1/Tp. The parameters, p, n1, and n2 were obtained by writing the DSC response predicted by the equation above in terms of a function which contains temperature as the only variable.

with \documentclass{article}\pagestyle{empty}\begin{document}$ \theta _i = \left({1/\beta} \right)\int_{T_0}^T {\kappa _i dT \le r_i} $\end{document} dT ⩽ ri and ri = 1/(1‐ni).

Fitting this equation to the DSC response measured at a scan rate of 4°C/min obtains p ≈ 0.66; n1 ≈ 0.55; n2 ≈ 2.2; B1 ≈ 8285; B2 ≈ 7480; κ1 ≈ 1. 12 × 108 s−1; κ2 ≈ 0.99 × 106 S−1.
Modeling and control of batch‐to‐batch polymer processes
Authors: Stoll Kenneth E. , Ralston Patricia A. S. , Wright Andrew L. , Harper Dean O.
Published: December 2004

The modeling and control of a typical cyclic polymer process, such as injection molding or thermoforming, are considered. The purpose of control is to achieve a specified product quality for a sequence of parts. First, conventional feedback controllers are compared to statistically based controllers with respect to random noise disturbances. It is shown that conventional controllers may not react quickly to load disturbances without magnifying background noise and reducing product yield. It is demonstrated that statistically based controllers are able to differentiate between noise and load disturbances, proving them superior when part quality tolerance is tight and noise level relatively large. Next, the responsiveness of conventional controllers (proportional, integral, and proportionalintegral) is compared with several statistically based controllers (CUSUM, Western Electric runs rules, and simple Shewhart) when subjected to load disturbances. Three load disturbances were modeled; steps, ramps, and sinusoids. Again, statistically based methods generally prove superior to and, at worst, comparable to conventional controllers.
Rheology of fumed silica dispersions for fiber‐optic cables
Authors: Khan Saad A. , Maruca Maria A. , Plitz Irene M.
Published: December 2004

Fumed silica dispersions in mineral or silicone oil are used to fill fiber‐optic cables to prevent macro‐bending of the fibers and to provide environmental protection. Adequate control of the rheology is essential for the effectiveness of the filling compounds; the materials must be sufficiently viscous to minimize stresses on the fibers but have considerable elasticity so as not to drip with time or temperature. The effects of shear history, aging, temperature, and water contamination on the rheological properties of two commercially available systems are studied using steady and dynamic measurements. The results are interpreted in terms of the microstructure resulting from the aggregation of submicron silica particles and their interactions with different solvents.
Basic magnesium carbonate flame retardants for polypropylene
Authors: Rigolo M. , Woodhams R. T.
Published: December 2004

Magnesium hydroxide and magnesium carbonates have attracted attention as endothermic flame retardants that are sufficiently stable to be incorporated into thermoplastics without decomposition. In this survey, a basic form of magnesium carbonate, magnesium carbonate hydroxide pentahydrate [(MgCO3)4 · Mg(OH)2 · 5H2O] was evaluated as a flame retardant for polypropylene. This filler (MCHP) has a thermal stability intermediate between that of alumina trihydrate (ATH) and magnesium hydroxide, which is sufficient to allow incorporation into polypropylene without decomposition. The MCHP is most effective at high filler concentrations near 60% where it was found to impart a Limiting Oxygen Index of 28.2 with a V‐O rating (no dripping). This is slightly more effective than the flammability ratings for ATH and Mg(OH)2 under the same conditions. The effectiveness of MCHP was attributed to the large endothermic loss of water of hydration, which also dilutes the combustion gases. This action was further aided by the formation of an intumescent char on the burning surface, which eventually extinguished the flame. Various combinations of magnesium oxide, magnesium hydroxide, magnesium carbonate, and MCHP were evaluated in order to clarify the mechanism of the flame retardant and improve the efficiency of the protective action. However, no synergism was evident, and the flame retardant results were found to be additive. The mechanical properties and processabilities of these highly filled compounds are very sensitive to the type of surface treatment. The method of Savides was employed to compare the burning temperature of the test specimens and to measure the rates of combustion.
Optical and mechanical properties of optically transparent poly(methyl methacrylate) composites
Authors: Lin Hongy , Day Delbert E. , Stoffer James O.
Published: December 2004

Highly transparent poly(methyl methacrylate) (PMMA) composites have been made by carefully matching the refractive index of the glass fiber reinforcement with the PMMA matrix. Composites containing 10.4 vol% glass fibers and 0.68 mm in thickness had an overall optical transmission of 92%. The transparency of the composites is temperature dependent because of the different temperature coefficients of refractive index for the glass fiber and PMMA. The tensile strength of the composites at room temperature was twice that of pure PMMA and decreased with increasing temperature, as predicted by the rule of mixtures.
Ultrasonic welding using tie‐layer materials. part I: Analysis of process operation
Authors: Tateishi N. , North T. H. , Woodhams R. T.
Published: December 2004

Ultrasonic welding of oriented polypropylene (OPP) using tie‐layer materials has been examined. The thermal cycle at the joint interface was evaluated using a high speed data acquisition system, and concurrent changes in horn displacement (penetration) and the output power were monitored. The model explaining process operation involves four phases, i.e., I–where heating occurs because of the stresses generated in asperities on the contacting surfaces; II–where the whole tie‐layer reaches the melting point; III–where the polymer melt is subjected to intense heating from viscous dissipation and is squeezed out; and IV–where the joint cools after welding. In the early stages of ultrasonic welding the heat generated at asperities on the contacting surfaces leads to melting of the tie‐layer/oriented polypropylene interface within 50 ms. The tie‐layer heats up because of a combination of viscoelastic dissipation and heat conduction from the oriented polypropylene/tie‐layer interface, and the rate of temperature rise at the midline of the tie‐layer is in the range 200°/s to 400°/s. The reduction in thickness of the test specimens (penetration) is negligible up to the time when the tie‐layer melts completely, and then changes rapidly when the melted polymer at the joint interface is squeezed out. The influence of machine parameters (amplitude and contact pressure) and of tie‐layer Melt Flow Index is also examined. The total time required for completion of the welding process decreases when the amplitude and applied pressure are increased. The use of low Melt Flow Index tie‐layers produces peak temperature as high as 600° at the bondline, and little material is ejected during the ultrasonic welding operation.
Phase morphology and mechanical properties of blends of poly(p‐phenylene sulfide) and polyamides
Authors: Akhtar Sania , White James L.
Published: December 2004

An experimental study of the blending, thermal transitions, phase morphology, and mechanical properties of poly(p‐phenylene sulfide) (PPS)/polyamide blends is presented. Nylon‐6, rubber modified nylon‐6, nylon‐66, nylon‐11, nylon‐12, and two partially aromatic amorphous polyamides were included in the study. Generally, blends of PPS with aromatic amorphous polyamides exhibit better mechanical properties than those with aliphatic polyamides. The blends with nylon‐12 exhibit the best characteristics among the aliphatic polyamides.
Steady state simulation of continuous‐flow stirred‐tank slurry propylene polymerization reactors
Authors: Sarkar Priyabrata , Gupta Santosh K.
Published: December 2004

Methodologies are developed for studying the steady‐state operation of propylene polymerization in continuous‐flow stirred tank reactors (CFSTRs). The effect of several reactor operating variables and reaction variables (e.g., mean residence time, catalyst deactivation rate, multisite catalyst activity, etc.) on polymer properties is obtained. It is found that a compromise has to be made between the yield of the polymer and its polydispersity index, since they usually show opposing trends with the mean residence time.
Model filled polymers. VII: Flow behavior of polymers containing monodisperse crosslinked polymeric beads
Authors: Sun Liqing , Park Moonsoo , Salovey R. , Aklonis J. J.
Published: December 2004

Steady shear viscosities and dynamic moduli of polymer composites, consisting of combinations of crosslinked beads and matrices of polystyrene (PS) and polymethacrylates (PMA), are measured in a cone and plate rheometer. Viscosities and moduli were very sensitive to chemical composition. Crosslinked beads of identical composition to the matrix exhibited the lowest viscosity enhancements at low shear rates and the lowest moduli in dynamic mechanical analysis. The effects of bead concentration on rheological behavior were compared for PS and PMMA beads in a PMMA matrix. PMMA beads produce small effects, whereas PS beads yield highly non‐Newtonian systems in PMMA, showing a yield stress of 1100 Pa at 30 wt% filler loading and dynamic moduli independent of frequency. We suggest that rheological behavior reflects the state of dispersion of beads in the matrix. Beads identical in composition to the matrix yield uniform dispersions. We propose that uniform and stable bead dispersions exhibit the lowest viscosity and moduli. Beads that cluster in the matrix, such as PS beads in PMMA, exhibit highly non‐Newtonian behavior.
Processing aids for mixing and extrusion of silica–natural rubber compounds
Authors: Nakajima N. , Shieh W. J. , Wang Z. G.
Published: December 2004

This paper explores the use of silica as a major component, 67% and 100%, of total filler content in natural rubber, carbon black being the minor component. In order to overcome the mixing difficulty, a coupling agent was used. A previous study dealt with the causes of difficulty in extruding high‐silica and all‐silica compounds. A premature reaction of the coupling agent with natural rubber resulted in wavy extrudates. In the case of a 100% silica compound, the filler dispersion and distribution were not satisfactory in spite of the presence of the coupling agent. The compound was too stiff to be extrudable. In the present work, metal carbonates were added to the formulation. They included calcium, zinc, magnesium, and lead carbonates. These additives significantly facilitated the incorporation, distribution, and dispersion of the filler. The resulting compounds were soft enough to be extruded. The extrudate surfaces were smooth to slightly wavy. Decreasing the amount of the coupling agent to 75% of the original recipe still allowed the compounds to be extruded, although the waviness of the extrudates increased somewhat.
Blending of poly(benzimidazole) (PBI) with a low molecular weight ether imide model compound
Authors: De Jong B. , Waddon A. J. , Karasz F. E. , Macknight W. J.
Published: December 2004

Poly(benzimidazole) (PBI) was solution‐blended with a low molecular weight ether‐imide analog to Ultem 1000. The as‐cast blends were found to form one‐phase structures over the whole of the composition range. By the use of optical microscopy and differential scanning calorimetry, the blends were found to phase separate on heating above the blend glass transition temperature (Tg) but did not remix on cooling. It was concluded that the blends formed on room temperature casting were nonequilibrium and remained one‐phase simply because they were well below Tg.
Finite element modeling of the time‐dependent behavior of nonlinear ductile polymers
Authors: Krishnaswamy P. , Tuttle M. E. , Emery A. F. , Ahmad J.
Published: December 2004

A finite element algorithm developed previously has been successfully extended to the study of nonlinear time‐dependent problems. Nonlinear viscoelastic and viscoplastic models have been used to study the time‐dependent deformation and failure of high density polyethylene (HDPE). Two classes of nonlinear models have been identified; those that allow stress redistribution with time under specified traction boundary conditions, and those that do not. The implications of using viscoelastic vs. viscoplastic models, as well as the specific mathematical form of the constitutive equations selected for use, have been studied. Strains predicted using the FE algorithm have been compared with experimental measurements for (i) a HDPE plate with a hole and (ii) a double edge notch HDPE specimen, both under remote tension. Excellent agreement was obtained between numerical predictions and the experimental values.
Constitutive equations of crack layer growth
Authors: Kadota K. , Chudnovsky A.
Published: December 2004

Many engineering polymers such as polyethylene undergo cold drawing. Consequently, a slowly growing crack in polyethylene is preceeded by a process zone consisting of drawn material. The crack and the process zone are considered to be a single entity called the Crack Layer (CL). The equilibrium size and shape of the process zone can be determined by minimizing the Gibbs potential of the material. The result is a system of integro‐differential equations which does not have analytic solutions. To simplify the problem, the analysis is limited to the “thin” process zones which have been observed frequently in many polymers. Using thermodynamics, the driving forces for the crack and process zone growths are expressed in terms of the partial derivatives of the Gibbs potential with respect to corresponding variables (the crack length and the process zone size). Kinetic equations for the CL growth are proposed. These equations take the form of Onsager‐type linear relations between the rates of crack and process zone growth and the driving forces. The equations are good descriptions of the experimentally observed nonmonotonic CL growth in polyethylene. CL stability analysis is used to obtain estimates of lifetimes.
Experimental and numerical investigations of the vacuum‐forming process
Authors: Taylor C. A. , Delorenzi H. G. , Kazmer D. O.
Published: December 2004

This paper exmines the influence of process variables on final thickness distributions for vacuum‐formed thermoplastic parts. The process variables investigated include evacuation rate, sheet surface temperature, mold temperature, and material slip over the mold surface. The experimental data presented include, in addition to thicknesses, sheet surface temperature obtained via infrared thermography. A finite element program to model the vacuum‐forming process is discussed, and the wall thickness distribution predicted by this program for a vacuum‐formed part is compared with the results of the experiments.