bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractVinyl 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

AbstractThree 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractFumed 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

AbstractMagnesium 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

AbstractHighly 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

AbstractUltrasonic 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

AbstractAn 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

AbstractMethodologies 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

AbstractSteady 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

AbstractThis 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

AbstractPoly(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

AbstractA 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

AbstractMany 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

AbstractThis 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.
Mesophase structure of some flexible chain polymers
Authors: Antipov E. M. , Kulichikhin V. G. , Platé N. A. 
Published: December 2004

AbstractThe mesophase structures of some flexible chain polymers, which do not contain mesogenic groups, but are able to form thermodynamically equilibrium mesomorphic states, were studied by means of the X‐ray analysis, the differential scanning calorimetry, and other methods. The mesophase polyethylene in bicomponent polymer blends, mesomorphic ultra‐high molecular weight polyphosphazenes, and membrane polyvinylorganosilanes were investigated. The scheme of polymer phase transitions is discussed. Besides conformational disordering, the step‐by‐step loss of different levels of the positional order (i.e. the multiple‐step character of melting) of flexible, semiflexible, and stiff chain polymers is deduced and illustrated by examples from the authors' experience and from the literature.
Thermophysical characterization of heterocyclic polymer networks
Authors: Privalko Valery P. , Kramarenko Victor Yu. 
Published: December 2004

AbstractHeterocyclic networks obtained by copolymerization of epoxy oligomer (ER) with different amounts of hexamethylene diisocyanate (HMDI) were characterized by IR‐spectra, PVT measurements in the temperature interval 320 to 470 K and pressure range 15 to 90 MPa, and heat capacity in the temperature interval 150 to 470 K. Experimental data are discussed in terms of the variation of characteristic parameters of the Frenkel‐Hirai‐Eyring hole model with relative proportion of three‐arm, six‐membered isocyanourea heterocyles and two‐arm, five‐membered oxamolidone rings which changed with HMDI/ER ratio.
Strain‐induced crystallization of poly(ethylene terephthalate)
Authors: Jabarin Saleh A. 
Published: December 2004

AbstractThe fabrication of poly(ethylene terephthalate), PET, into fibers, films, and containers usually involves molecular orientation caused by molecular strain, which may lead to stress‐ or strain‐induced crystallization (SIC). The SIC of PET was studied by the methods of birefringence, density, thermal analysis, light scattering, and wide‐angle X‐ray. The development of crystallinity is discussed in relation to the rate of crystallization, the residual degree of orientation, and stress relaxation. The experimental procedure involves stretching samples at temperatures above the glass transition temperature, Tg, to a given extension ratio and at a specific strain rate of an Instron machine. At the end of stretching, the sample is annealed in the stretched state and at the stretching temperature for various periods of time, after which the sample is quickly quenched to room temperature for subsequent measurements. During stretching, the stress strain and the stress relaxation curves are recorded. The results indicate that the SIC of annealed, stretched PET can proceed in three different paths depending on the residual degree of orientation. At a low degree of residual orientation, as indicated by the birefringence value, annealing of stretched PET leads only to molecular relaxation, resulting in a decrease of birefringence. At intermediate orientation levels, annealing causes an initial decrease in birefringence followed by a gradual increase and finally a leveling off of birefringence after a fairly long period of time. At higher orientation levels, annealing causes a rapid increase in birefringence before leveling off. The interpretation of the above results is made using the measurements of light scattering, differential scanning calorimetry, and wide‐angle X‐ray. The rate of the SIC of PET is also discussed in terms of specific data analysis.
Assessment of oxidative thermal degradation of crosslinked polyethylene and ethylene propylene rubber cable insulation
Authors: Anandakumaran K. , Stonkus D. J. 
Published: December 2004

AbstractThis paper presents procedures to monitor oxidation degradation of two commonly used cable insulations, crosslinked polyethylene (XLPE) and ethylene propylene rubber (EPR). Since the techniques described require only micro specimens, deterioration of cable insulation can be monitored without destroying the function of the cable. The techniques described are melting point, crystallinity, infrared carbonyl absorbance, gel content, relative hardness, and differential scanning calorimetry (DSC) oxidation induction time. The techniques were applied following accelerated aging over a period in excess of two years. The results from the micro specimens were directly related to embrittlement and the decrease in ultimate elongation. The previous thermal history of XLPE was determined using DSC melting peak analysis.