bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low pressure rheology of granular powders using a drawing plate technique
Authors: Lee Biing‐Lin 
Published: December 2004

AbstractAn analysis of a drawing plate test for easily monitoring the low‐pressure frictional characteristics of powders is presented. The test is performed by measuring the force required to withdraw a plate from a cylindrical bed of dry powder. The characteristics of the drawing force profile are analyzed using Janssen's classical differential element approach to relate the product μK of powders as a function of packing of powder medium, where μ is the coefficient of friction of the powders against the solid drawing plate, and K is Janssen's constant, an anisotropic pressure distribution factor of a powder bed. The packing arrangement, expressed as the external void fraction, due to tapping, significantly alters the μK value and the effective sustaining strength of a powder bed. Experimental results on spherical glass beads having mono‐ and bimodal size distributions, and on three different poly (vinyl chloride) (PVC) powders are discussed. A spherical, high bulk density PVC powder has the combination of low μK and high, bulk density desirable for rigid powder compounding applications.
Characterization of linear copolymers by methods sensitive to the refractive index increment
Authors: Rodríguez Rogelio 
Published: December 2004

AbstractFor linear copolymer molecules, the refractive index increment depends on the chemical composition of the molecules. However, the polydispersity in chemical composition of the sample introduces a great complexity in the data analysis in order to obtain a true molecular weight distribution. Even when the mean chemical composition does not depend on the molecular weight, a correction has to be applied when the output of an instrument depends quadratically on the refractive index Increment of the sample, such as in a light‐scattering measurement. For that purpose, the light‐scattering expressions are written in terms of polydispersity in chemical composition, which in turn is modeled using linear copolymerization equations. The microstructure effects, which are related to the order in which two different kinds of monomers appear along the chain, are not as yet taken into account in this approach.
Characterization of polymer molecular weight distribution by transient viscoelasticity: Polytetrafluoroethylenes
Authors: Wu Souheng 
Published: December 2004

AbstractThe relationship between the relaxation time spectrum H(τ) in the terminal zone and the volume‐fraction differential molecular‐weight‐distribution function P(M) is derived by considering binary chain contacts for stress transmission,

equation image

where β and λ are constants for a given chemical type. This is used to determine the molecular‐weight‐distribution curves from the stress relaxation modulus spectrum (above the crystal melting point) at 370°C for a number of commercial and experimental poly(tetrafluoroethylenes) (PTFEs). It is found that PTFEs typically have bimodal molecular‐weight distributions. The lower‐molecular‐weight peak conforms essentially to the “most‐probable” distribution, and the higher‐molecular‐weight peak to the binary coupling distribution. The entanglement molecular weight Me is 5490, and the number of main‐chain atoms between entanglement points is 110, consistent with a flexible chain. The zero‐shear melt viscosity at 370°C is η0 = 1.79 × 10−13 Mw2.94±0.13, where η0 is in Pa.s and Mw/Me = 2,000 to 12,000. The monomeric friction coefficient is also determined.
The effect of thermal history on the deformation mechanism of 2,6‐dimethylpoly(phenylene oxide)
Authors: Dalal V. F. , Moet A. 
Published: December 2004

AbstractStress‐strain relationship of 2,6 dimethyl poly(phenylene oxide)(2,6 MPPO) was established simultaneously with optical micrographic examination as a function of thermal history. Films (5–7 μm) were solvent cast and annealed below their glass transition and melting point. As‐cast film showed ductile behavior associated with shearband formation, whereas thermally treated material exhibited marked embrittlement; the slower it cooled the more brittle it became. Thermally treated material showed mixed mode deformation: crazing and shearbanding. The correlation between the deformation mechanism and its solid state structure was studied using differential scanning calorimetry, wide angle x‐ray diffraction, and density measurement.
Properties of segmented block copolyurethane II. Adhesion between PET cord and rubber by poly(styrene‐b‐butadiene) polyethylene terephthalate block copolyurethane
Authors: Yamashiro Seiichi , Kuratsuji Takatoshi 
Published: December 2004

AbstractHydroxy‐terminated copoly(fstyrene‐b‐1,2‐butadiene) (HPSB) containing rubber‐affinitive vinyl side chains and having a molecular weight of 2000 to 4000 were prepared, and block copolyurethanes were synthesized by using a low molecular weight hydroxy‐terminated poly (ethyl en e terephthalate) as a PET‐affinitive component and 4,4′‐diphenylmethane diisocyanate as a chain extender. The relationships between the molecular weight of HPSB, copolymerization ratio of styrene to butadiene and the adhesive strength of PKT/rubber in high temperature atmospheres were examined. A peak of adhesive strength was observed at styrene copolymerization ratio of 20 wt percent and a HPSB molecular weight of 3000. The adhesion mechanism was estimated from the behavior of the characteristic infrared absorption of block Copolyurethane in heating.
Process control of profile extrusion using thermal method. Part II: Closed loop control
Authors: Yang B. , Lee L. J. 
Published: December 2004

AbstractThe analytical flow model developed in Part I was applied to the online control of profile extrusion. A rubberized polystyrene was extruded through a simple L‐shaped profile die with one thin section and one thick section. Take‐up speed was used to control the size of the extrudate, and die temperature was used to control the shape of the extrudate. Two different control algorithms, a dual single‐loop feedback PI controller and a multivariable feedforward plus feedback control method (FFC), were carried out for set point changes of the extrudate shape and size, and load disturbances of screw speed. Results showed that the PI feedback controller was satisfactory for long‐term set point changes but not for load changes. The FFC worked well for load disturbances lower than 10 cycles/min. Owing to the slow dynamic response of die temperature, the shape loop can only be controlled for long‐term disturbances.
Vibration welding of thermoplastics. Part II: Analysis of the welding process
Authors: Stokes V. K. 
Published: December 2004

AbstractThe vibration welding process for thermoplastics is known to consist of four phases: (1) initial heating of the interface to the melting temperature by Coulomb friction; (2) unsteady melting and flow in the lateral direction; (3) steady‐state flow; and (4) unsteady flow and solidification of the film after the vibratory motion is stopped. Simple analytical models are developed for the first three phases. These models are used for estimating the molten film thickness, the size of the heat affected zone, and the weld time as functions of the weld parameters: the amplitude and frequency of the weld motion, and the weld pressure. The steady‐state film thickness and the heat‐affected zone are shown to be very small.
Practical characterization of the structure of crystalline polymer moldings
Authors: Samuels Robert J. 
Published: December 2004

AbstractThe thermal and flow gradients present during thick polymer molding processes can produce layered structures through the thickness which vary in crystallinity, orientation, and axiality. Such structural complexity is difficult, expensive, and time consuming to characterize and presently impossible to predict. In order to overcome these problems emphasis in our laboratory has been directed toward the development of rapid, nondestructive techniques for the quantitative characterization of the structure of thick polymer samples. This includes the characterization of the average structure, the surface structure, and the internal layer structure. The present paper discusses some of these techniques and illustrates their application.
Orientation technology and commercial products from a unique roll orientation process
Authors: Gould Russell J. 
Published: December 2004

AbstractIt is well known that orientation can produce, at a minimum, an order of magnitude improvement in physical properties of low cost plastic resins. A unique, large‐scale, commercial rolling mill process for continuous orientation of plastic sheet has been developed, A number of oriented materials have been commercially produced by this rolling mill process with a wide variety of physical properties attained. This has resulted in large volume sales of many interesting commercial products. Over the last thirty years, numerous researchers have conducted studies to evaluate the theoretical aspects of the rolling process, and the resultant properties. Most commercial oriented products are of relatively small cross sectional size such as fibers and film. The process reported herein produces heavy cross section oriented sheet. A new class of high strength thermoplastic materials is now available for design engineers to use. Long‐term strength properties are often 10 to 100 times better than with unoriented thermoplastics.
Dynamic mechanical behavior of polymers containing carbon black
Authors: Gandhi Khushroo , Salovey R. 
Published: December 2004

AbstractThe dynamic mechanical behavior of carbon black filled polymers of styrene and butyl methacrylate was examined at low strain amplitude and frequency in order to minimize destruction of the composite structure and elucidate the basis of yield and plasticization observed in steady shear. For specific filled systems, both G′ and G″ became independent of frequency and temperature at low frequencies, consistent with a yield phenomenon and the formation of a carbon black network. On the other hand, although the high molecular weight polystyrene showed plasticization effects at higher shear rates in steady shear rheology, such, plasticization effects were never observed in dynamic mechanical analysts. Yield behavior was observed most readily for the low molecular weight polystyrene. Limiting moduli for filled polystyrenes were independent of temperature, whereas, for polybutyl methacrylate, were sensitive to temperature. It is suggested that an independent network of carbon black is strongest in the low molecular weight polystyrene and weakest in poly (butyl methacrylate).
A polymer complex as a new type of electron beam resist for dry development
Authors: Yoneyama Sachiko , Oguchi Kiyoshi , Watanabe Masayoshi , Sanui Kohei , Ogata Naoya , Takahashi Yoichi , Nakada Tomihiro 
Published: December 2004

AbstractPolymer complex of poly (4‐vinylpyrldine) and malonic acid was investigated as a new type of electron beam (EB) resist for dry development, as malonic acid was decomposed by EB irradiation. It was found that the polymer complex could be developed with O2 plasma etching and that the positive resist patterns with high resolution could be obtained. The mechanism for this lithography process was studied by means of IR and ESCA spectra.
Vibration welding of thermoplastics. Part III: Strength of polycarbonate butt welds
Authors: Stokes V. K. 
Published: December 2004

AbstractIn 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. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration; The effects of these parameters on weld quality were systematically studied by first butt‐welding polycarbonate specimens under controlled conditions over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests, A significant result is the apparent existence of a weld‐penetration threshold above which high weld strengths are attained, but below which the strength drops off. Under the right conditions, the strengths of polycarbonate butt welds are shown to equal the strength of the virgin polymer.
Foaming characteristics of filled solutions of nitrile butadiene rubber
Authors: Hoontrakul P. , Szamosi Janos , Toeing S. D. 
Published: December 2004

AbstractDuring the development of nitrile‐butadiene‐rubber‐based coatings, persistent foaming—a grave obstacle in such applications—was encountered, An investigation was undertaken to study the behavior of foams in order to prevent their formation. Both the apparent viscosity and the foam stability were found to attain their minimum values at the same filler level. It is plausible that the observed phenomenon is due to the binding of polymer chains to filler particles, which takes place most effectively at a certain proportion of filler and polymer.
Moldability diagrams for the reaction injection molding of a polyurethane crosslinking system
Authors: Manas‐Zloczower I. , Macosko C. W. 
Published: December 2004

AbstractA trial and error approach reflects the state of the art in reaction injection molding. Material and process parameters determine the “moldability” of a specific system in a particular application. The concept of “molding areas” on the critical parameters plane can be extended form thermoplastic injection molding (TIM) to reaction injection molding (RIM).In this work moldability diagrams for the filling and curing stages of a RIM process are obtained based on a simplified engineering approach. The key process parameters chosen for the filling stage are initial material temperature and filling time. In the curing stage, the critical parameters are considered to be mold wall temperature and demold time. Experimental results obtained on a laboratory‐scale RIM machine on a Crosslinking polyurethane system are used to check the validity of the predicted molding areas. The agreement obtained is satisfactory considering the broad range of processing parameters used.
An efficient algorithm of computation of molecular weight distributions and its moments for reversible step growth polymerization in homogeneous continuous flow stirred tank reactors
Authors: Kumar Anil 
Published: December 2004

AbstractThe reversible step growth polymerization in homogeneous continuous flow stirred tank reactors (HCSTRs), in which the condensation product (W) leaves the reactor through flashing, has been analyzed. The molecular weight distribution (MWD) of the polymer formed is governed by nonlinear coupled algebraic relations to be solved simultaneously. To find the MWD numerically a large number of these are normally solved simultaneously using a suitable iterative procedure. In this paper, these have been decoupled using the technique proposed in our earlier works (1, 2) and the MWD can now be obtained sequentially without any trial and error. This leads to considerable saving in computation time compared to methods currently used. To demonstrate the efficacy of the algorithm, the polycondensation step of the poly(ethylene terephthal‐ate) (PET) formed in HCSTRs has been analyzed. The MWD, the average chain length and the polydispersity index of the polymer have been computed and it takes 0.1 CPU seconds on a DEC 1090 as opposed to the earlier method which would take seventy minutes for similar computations. The simple model of the HCSTR for the PET formation gives the effect of reactor temperature and pressure and the quantitative results have been presented in this paper.
Shrinkage forces and birefringences of an amorphous stretched copolyterephthalate
Authors: Pereña J. M. , Benavente R. 
Published: December 2004

AbstractMeasurements of shrinkage stress and birefringence have been undertaken on drawn samples of a copolyterephthalate based on ethylene glycol and 1,4 cyclohexane‐dimethanol. The temperature location and the peak value of the maximum shrinkage stress have been related to the drawing conditions (temperature, strain rate and draw ratio), comparing the results with those reported for poly (ethylene terephthalate). Moreover, a value of the stress optical coefficient of the copolymer equal to 14.5 × 10−9 m2 N−l has been obtained.
Molecular structure, crystallization behavior, and morphology of fractions obtained from an extrusion grade high‐density polyethylene
Authors: Gedde U. W. , Jansson J‐F. , Liljenström G. , Eklund S. , Holding S. R. , Wang P‐L. , Werner P‐E. 
Published: December 2004

AbstractAn extrusion‐grade of high density polyethylene (HOPE) (3 ethyl groups per 1000 carbons) has been divided into 16 fractions by preparative GPC and selective p‐xylene extraction. The fractions, with molecular weights ranging from 900 to 1,000,000, have been studied by IR spectros‐copy, DSC, WAXS, polarized microscopy, and small‐angle light scattering (SALS), The average degree of chain branching (percent C2H5) is 0.5 percent for the part of the sample having a molecular weight lower than 10,000 and it decreases monotonically with increasing molecular weight, finally approaching 0.1 percent C2H5. A crystallinity depression with respect to linear PE equivalent to 20 percent/(percent C2H5) is recorded for all samples except for the very low molecular weight samples for which the crystallinity depression is much larger (30 to 35 percent/ (percent C2H5)). The unit cell volume increases with increasing percent C2H5, presumably due to the inclusion of ethyl groups in the crystals as interstitlals at 2gl kinks. The concentration of ethyl groups in the crystals (ϵc) unanimously follows the relationship: ϵc(percent) = 0.32 + 0.25 log(percent C2H5) except for the low molecular weight fractions which have significantly lower values for ϵc. Our admittedly speculative explanation for this major discrepancy between high and low molecular weight samples is based on the idea that segments with ethyl groups close to chain ends have a greater difficulty in crystallizing than segments containing ethyl groups located at positions far from the chain ends. The fractions obtained from the extrusion‐grade HDPE show a solidification temperature depression with respect to linear PE which can only be explained by the presence of chain branches in these samples. The depression is particularly pronounced for the low molecular weight samples as is expected from the data on molecular structure. Well‐developed non‐banded spherulites are observed in rapidly cooled (crystallized at about 35 K supercooling), low molecular weight samples (6,000 < Mw < 8,000)from the extrusion‐grade HDPE in contrast to the axialites observed in linear PE of the same molecular weight and thermal treatment. This discrepancy in morphology has been related to the presence of ethyl groups in the extrusion grade HDPE fractions. Higher molecular weight samples (20,000 < Mw < 1,000,000)from the extrusion‐grade HDPE and linear PE both display well‐developed banded spherulites of similar nature as is expected due to the similarity in molecular structure of the two sets of sample.
Blends of thermoplastic polyesters with amorphous polyamide. I. Thermal and crystallization behavior
Authors: Nadkarni V. M. , Shingankuli V. L. , Jog J. P. 
Published: December 2004

AbstractThe thermal and crystallization behavior of blends of three thermoplastic polyesters with different degrees of crystallizability, with an amorphous aromatic polyamide is reported. The thermoplastic polyesters used in the investigation were poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET) and a co‐polyester of 1,4 cyclohexane‐dimethanol, ethylene glydol and terephthalic acid (PETG). The blends exhibited a single glass transition temperature indicating mlseibility in the amorphous phase. The results of thermal analysis indicated that the crystallization of all the three polyesters is facilitated in the molten phase as a result of blending. The blending significantly Increased the degree of crystallinity of PET, but there was no change in the crystallinity of PBT. It is thus observed that the extent of change in both the crystallization rate and the degree of crystallinity of polyesters depend on the inherent crystallizability of the individual polyester.
Liquid‐liquid phase behavior of mixtures according to the Simha‐Somcynsky theory
Authors: Stroeks Alexander , Nies Erik 
Published: December 2004

AbstractIt is well known that equilibrium, thermodynamic properties are governed by different functional derivatives of the thermodynamic functions of state. For example, the phase behavior of mixtures of low and/or high molar mass components is determined by the compositional derivatives of the free energy. In this contribution, the merits of the Simha‐Somcynsky theory in describing and predicting the phase behavior of mixtures are considered. The influence of temperature and composition on the miscibility behavior for practically binary polymer solutions are studied. Furthermore, the important aspect of polydispersity, inherent to synthetic polymer systems will be addressed.
Characterization of blends of naphthalene‐containing polymers with poly(alkyl methacrylates) by combined steady‐state fluorescence spectroscopy and fluorescence decay measurements
Authors: Holden David A. , Strauss John 
Published: December 2004

AbstractThe extent of mixing in two‐component solution‐cast films of poly(2‐vinyl naphthalene) (P2VN) and poly(2‐iso‐propenyl naphthalene) (P2IPN) with poly(methyl methacrylate) and poly(n‐butyl methacrylate) was studied by steady‐state and time‐resolved fluorescence spectroscopy. The steady‐state fluorescence spectrum of 1% P2IPN in the two poly(alkyl methacrylates) evolves from 100% monomer emission (λmax = 340 nm) to >70% excimer emission (λmax = 390 nm) as its molecular weight increases from 1900 to 278000. Despite such clear‐cut changes in the steady‐state spectra on phase separation, the fluorescence decays were nonexponential for all mixed films. Triple‐exponential decay functions were necessary to describe excimer decays at 430 nm and monomer decays at 340 nm. Moreover, the fluorescence decays varied slightly across the excimer emission band, and changed significantly when the polymer films were annealed. Studies on blends containing from 1 to 100% of P2VN and P2IPN established that this multicomppnent fluorescence decay behavior is intrinsicto the naphthalene‐containing polymer phase, it is proposed that excimers formed between chromophores in meso and racemic dyads have different mean decay times and that imperfectly aligned chromophore pairs lead to an additional short‐lived excimer decay component.
Compositional variations in cast films of blends of copolymers of siloxanes and poly(methyl methacrylate) determined by energy dispersive spectroscopy and X‐ray image analysis
Authors: Blahovici T. F. , Brown G. R. 
Published: December 2004

AbstractFilms cast on gold surfaces from 3% methylene chloride solutions of syndiotactic poly(methyl methacrylate) (PMMA) (Mn = 23,000) and random copolymers of PMMA and 4‐(methacryloyloxybutyl) pentamethyldisiloxane (MBPD) (Mn = 40,000) are all heterogeneous with visible phase separation occurring over most of the compositional range. Energy dispersive spectroscopy (EDS) shows that for PMMA blended with the copolymers there is an excess of silicon, ranging from 1.9 wt% to 9.7 wt%, in the surface exposed to air during casting, while the lower surface exposed to the gold is depleted in silicon. X‐Ray mapping and image analysis show that for blends containing 50% or less of siloxane copolymer the upper surface is composed of large siloxane rich domains in a PMMA matrix while the lower surface is composed of much smaller and less abundant siloxane domains in a PMMA matrix. In addition, the siloxane domains of the upper surface contain small PMMA domains. For blends with a greater siloxane content, the upper surface is composed of a siloxane matrix while the lower surface remains PMMA rich.