bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction and measurement of the thermal expansion coefficient of crystalline polymers
Authors: Kardos J. L. , Raisoni J. , Piccarolo S. , Halpin J. C. 
Published: December 2004

AbstractAmong the increased structural demands now being made on both unfilled and reinforced plastics is that of dimensional stability under various performance environments. Crystalline polymers are heterogeneous materials consisting of two distinct phases and, as such, can be treated as molecular versions of engineering composites. This paper first outlines the general physical model whereby a crystalline polymer is considered to be a multi‐ply laminate of unidirectionally reinforced plies. The calculational format is then detailed for the prediction of the stiffness and thermal expansion coefficient of an isotropic sheet of crystalline polymer and a sample calculation is given for quenched high density polyethylene. A data base is presented for the stiffness and thermal expansion coefficient of low and high density polyethylene having quenched, slowcooled, and annealed thermal histories. Comparison between experimental and predicted results yields good agreement in all cases to better than 25 percent. Implications and limitations of the predictive technique are discussed.
Interfacial effects on the NMR of composite polymers
Authors: Douglass Dean C. , McBrierty Vincent J. 
Published: December 2004

AbstractSeveral NMR experiments can provide estimates of the scale of spatial inhomogeneity in solid materials in the range of nanometers to microns. The effects underlying these experiments their interpretation, and models used in their interpretation are discussed and illustrated with applications to polymers. Examples chosen from the literature include semicrystalline polymers (polyethylene, polyvinylidene fluoride, polychlorotrifluoroethylene), filled elastomers (carbon‐filled butadiene), copolymers (styrene: butadiene, dimethylsiloxane: bisphenol‐A polycarbonate, polyurethane) and blends (polymethylmethacrylate‐polystyreneacrylonitrile, polyvinylidene fluoride‐polymethylmethacrylate). Comparison of examples directs attention to the similarity in anisotropic motional behavior of highly constrained interfacial material in semicrystalline and filled polymers. While no one experiment is applicable to all dimensions, or all systems, NMR has proven especially useful for dimensions in the range of tens of nanometers, where other techniques are often less revealing.
Capillary viscometry: A complete analysis including pressure and viscous heating effects
Authors: Kamal Musa R. , Nyun Hla 
Published: December 2004

AbstractCapillary viscometers have been used extensively, because of their simplicity and reliability, to measure the viscosity of fluids over a wide range of shear rates. However, in capillary flow, the shear rate is not uniform throughout the capillary, a pressure gradient is established in the direction of flow, and the temperature of the fluid is nonuniform due to viscous dissipation. In the present work, a general, simple and practical method is proposed for correcting for the effects of pressure variation and viscous dissipation in determining the viscosity of polymer melts at high pressures. The method essentially involves the estimation of temperature, pressure, shear rate, and shear stress under a variety of experimental conditions at a predetermined point in the capillary. As such, it may be considered as a generalized extension of the classical Rabinowitsch‐Mooney method for estimating true viscosity in capillary flow.
Experimental and theoretical investigation of extrudate swell of polymer melts from small (length)/(cross‐section) ratio slit and capillary dies
Authors: Huang David , White James L. 
Published: December 2004

AbstractAn experimental and theoretical study is presented of extrudate swell from short capillary and slit dies. The polymer melts studied were polystyrene and polypropylene. The swell from slit dies is greater than the swell from capillaries. Decreasing die entry angle for capillary dies decreases swell. The argument is made that elongational How existing in the die entry region and for short dies determines extrudate swell. Dimensional analysis arguments are used to relate extrudate swell to a Weissenberg number based on elongational flow at the die entrance and the detailed die geometry. Correlations are developed. The theoretical study is based on unconstrained elastic recovery following elongational How through the die entrance region.
Differential scanning calorimetry analysis of morphological changes in segmented elastomers
Authors: Hesketh T. R. , Van Bogart J. W. C. , Cooper S. L. 
Published: December 2004

AbstractInvestigations of morphological changes which are induced in segmented elastomers by annealing and quenching are reported. Four different polymers were studied each based on the same soft segment—1000 or 2000 molecular weight poly(tetramethylene oxide). The hard segments were 4,4′‐diphenylmethane diisocyanate (MDI) chain extended with 1,4‐butane diol (ET series), piperazine coupled with 1,4‐butane diol bischloroformate (BN‐1,4), or dimethyl terephthalate condensed with 1,4‐butane diol (H‐50). Following annealing at various temperatures (120, 150, 170, or 190°C), the polymers were quenched to ambient conditions, and their properties measured by differential scanning calorimetry (DSC) as a function of time following the quench. DSC measurements taken immediately after the quench show that the soft segment Tg is higher than that of the control, suggesting that the applied thermal history promoted increased mixing of hard and soft segments. As time passes after quenching, the Tg values decrease and approach an equilibrium value. This effect is much smaller for those samples having crystalline hard segments. Endotherms attributed to the disruption of long range ordering in the hard segment domains resulted from the annealing process. These endotherms appeared at higher temperatures for higher annealing temperatures. The positions of crystalline melting endotherms were independent of the annealing/quenching conditions investigated.
The carrier dyeing of synthetic fibers
Authors: Ingamells W. , Peters R. H. 
Published: December 2004

AbstractThe mode of action of carriers in augmenting the rate of dyeing of disperse dyes with acrylic and polyester fibers is discussed in terms of the plasticizing action of the carrier. It is shown that the effectiveness of a carrier is determined by its ability to reduce the glass transition temperature of the fiber and not by the fiber swelling. The rate of dyeing as measured by the diffusion coefficient of the dye is shown to be uniquely related to the difference between the dyeing temperature and the glass transition temperature (T – Tg). In the light of these results, some aspects of carrier action in dyeing from perchlorethylene are discussed. Treatment of polyester fibers with carrier also increases crystallinity. Changes in diffusion for a series of copolyesters have been correlated with the long spacing obtained from small angle X‐ray scattering (SAXS).
Residual solvent and its diffusion in acrylic fibers
Authors: Armstrong A. A. , Borie R. D. , Lanier W. W. 
Published: December 2004

AbstractA survey showed that some commercial acrylic fiber products contain small quantities of residual solvent (dimethylacetamide). No diffusion of solvent from these products could be detected on laundering, dry cleaning, or exposure to synthetic perspiration. Acrylic carpets containing residual solvent were enclosed in sealed boxes to simulate a closed room. Air in the boxes was monitored for solvent content over a 14‐day period at 24°C (75°F) and 38°C (100°F) at both low and high humidity conditions. In all cases the solvent content of the air was below the detection limit of the best analytical procedure available (below 0.1 ppm). Diffusion rates of sol vent from 15‐denier carpel fiber into nitrogen were measured over the temperature range of 25–100°C. There was no detectable diffusion below 60°C measured over a 24‐h period. Mass diffusivities ranged from 2.5 × 10−19 cm2/s at 60°C to 6.4 × 10−14 cm2/s at 100°C. Under the conditions of expected use, the rate of diffusion of residual solvent from acrylic fibers is very low. Based on the low concentrations of residual solvent and its very low diffusion rate, there is an extremely low probability of any exposure to solvent from the residual solvent present in commercial acrylic fiber products.
A sorption theory for gas mixtures
Authors: Dent R. W. 
Published: December 2004

AbstractFrom kinetic theory, an equation has been developed for the multilayer sorption of each of two competing gases or vapors onto sites on or within a sorbing material. The thermodynamic characteristics of sorption in the first layer are assumed to differ from those of the second and higher layers, which are all assumed to be identical, as in the Brunauer, Emmett and Teller (B.E.T.) Model. However, in contrast to the B.E.T. Model, these outer layers are not taken to be identical to bulk liquid. The model gives a closed form solution involving seven constants of which five can be obtained from the corresponding pure component sorption. The version of this equation for single gas sorption has three constants and differs from the classical B.E.T. equation, by having the extra constant. The Langmuir and B.E.T. equations are in fact limiting forms of this single gas equation. Examples are given which show excellent fits to experimental, sigmoidal isotherms from the literature up to about 95 percent of the saturation pressure, whereas the B.E.T. generally deviates above 40–50 percent of saturation. The equation can also be partitioned to give important information regarding the distribution of the sorbed molecules, and gives values for the ‘bound’ first layer content and for the ‘mobile’ higher layer sorbed fraction at equilibrium for any relative pressure.
The thermodynamic state of water in cellulose acetate membranes
Authors: Burghoff H.‐G. , Pusch W. 
Published: December 2004

AbstractUsing experimental sorption data and corresponding experimental results from calorimetric investigations, the state of water in cellulose acetate (CA) membranes is discussed by applying a theoretical treatment of sorption reported previously (1–3). The sorption of water can be attributed to a gain in surface energy at the polymer/vapor interface. Using differential thermodynamic potentials of sorbed water together with experimentally determined heat capacities of sorbed water, the thermodynamic potentials G, H, and S of sorbed water are estimated for the temperature interval −40 to + 40°C. At constant temperature, each thermodynamic potential depends on the water content. The resulting distribution function of G indicates that the sorbed water exists in different states. Comparing the Gibbs free energy of sorbed water with that of ice or liquid water at the same temperature leads to the conclusion that none of the sorbed water freezes to ice within the temperature interval used. Based on the Gibbs free energy of water in electrolyte solutions and the distribution function of G for sorbed water, partition coefficients of salts within CA membranes may be estimated. The results are in good agreement with experimentally determined partition coefficients which are available from the literature. As the partition coefficient of a salt is directly related to the salt rejection of the membrane, this provides a method of estimating the desalination performance of a membrane from its water sorption isotherm.
Water vapor transport in an epoxy resin based on TGMDA and DICY
Authors: Illinger Joyce L. , Schneider Nathaniel S. 
Published: December 2004

AbstractWater uptake has been measured in an epoxy resin based on tetraglycidylmethylenedianiline curved with dicyanidamide. The curing behavior of this system as elucidated by differential scanning calorimetry and Fourier transform infrared is complex. Based upon this information we selected curing temperatures and times in addition to the “standard” cure. The kinetics of the sorption of water by the materials which have undergone the standard cure indicate that the two modes of sorption are involved at high humidity and only a single mode at lower humidity (as seen by changes in the slope of the log Mt vs log t plots). The kinetics of the sorption in the resins which have undergone post cure at higher temperatures also indicate two or more modes of sorption at high humidities. However the slopes of the log Mt vs log t plots differ from those for the resin with standard cure. Subsequent sorption/desorption cycles on the standard cure resin showed marked increases in the initial sorption rate as well as changes in mode, suggesting that irreversible changes in the resin had occurred.
Epoxy‐water interactions
Authors: Moy P. , Karasz F. E. 
Published: December 2004

AbstractIt has been shown that sorbed moisture plasticizes epoxy resins with a resultant depression in the glass transition temperature of the polymer. The nature of the epoxy‐water interaction still requires further investigation. The equilibrium sorption and diffusion of water in a high Tg epoxy is examined. Other analytical techniques including differential scanning calorimetry, infrared spectroscopy, electron microscopy and nuclear magnetic resonance are applied to the system. Experimental results suggest that the sorbed water at low concentrations is strongly localized at specific segments or groups in the polymer. Discussion is given relative to the structure‐properties of the epoxy and its possible correlation to the experimental data obtained.
Preparation of an ionomer elastomer by continuous sulfonation in an extruder and neutralization in static mixers
Authors: Siadat B. , Lundberg R. D. , Lenz R. W. 
Published: December 2004

AbstractRapid and efficient sulfonation of ethylene‐propylene terpolymer elastomer (EPDM) was achieved in a continuous melt mixing process. A mixture of sulfuric acid and acetic anhydride was used as the sulfonating agent. The reaction of EPDM polymer and the sulfonating agent was carried out in an extruder. It was shown that the continuous melt sulfonation of EPDM polymer may be used as an alternative to the batch solution methods previously reported for the preparation of sulfonated EPDM polymer. The extruder‐reactor method offers advantages of shorter process time, elimination of solvent handling hazards, and abatement of solvent removal and recovery problems.
Hydrostatic extrusion of linear polyethylene in tubular and non‐circular sections
Authors: Hope P. S. , Gibson A. G. , Parsons B. , Ward I. M. 
Published: December 2004

AbstractTubular and non‐circular section components have been produced by solid‐phase hydrostatic extrusion of linear polyethylene. Although the extrusion pressures were found to increase with the degree of complexity of the product sections, the module of the products were greatly enhanced and increased linearly with deformation ratio in the manner reported previously for circular section extrusions. Factors influencing the mechanics and stability of the process are discussed.
Melting performance in the single screw extrusion of thermoplastics
Authors: Cox A. P. D. , Fenner R. T. 
Published: December 2004

AbstractMelting performance experiments involving three different thermoplastics and three different screw designs have been carried out on a well‐instrumented single screw extruder equipped for cold screw extractions. In the case of the particular polystyrene used it was possible to deduce, from measurements made on the extracted screw, the velocity, and hence acceleration, of the solid bed of compacted polymer at points along the screw channel. The experimental results are successfully compared with the performance predicted by a previously established model, the most important feature of which is the ability to allow the solid bed to deform freely and hence to accelerate. The results show that the bed does indeed suffer significant and non‐uniform acceleration and that the model can predict both this acceleration and the resulting bed break‐up which leads to surging.
Mixing in an intermeshing twin screw extruder chamber: Combined cross and down channel flow
Authors: Maheshri Jagdish C. , Wyman Charles E. 
Published: December 2004

AbstractThe cross and down channel flows are analyzed in the center of an idealized leakproof intermeshing twin screw extruder chamber. The respective velocity components are assumed to vary only with channel depth. Because the screw flights block the cross channel flow, fluid circulates between two complementary channel depths in the cross channel direction just as predicted for single screw extruders. In addition, fluid circulates between an independent set of channel depths in the down channel direction due to the seal provided by the second screw lands. When the two fluid motions are considered simultaneously, a fluid particle is predicted to follow a complex path over a number of channel depths during its residence time in the extruder. This unique flow also causes particles which are initially near one another to eventually move to significantly distant locations. Furthermore, a wide range of velocities and shear rates is experienced by a fluid particle as it moves to the various channel depths. The strain predicted by two approaches is nearly uniform for the twin screw extruder product in striking contrast to the distribution of absolute strains found in single screw devices. The strain uniformity, wide shear history, and fluid separation predicted by this analysis of a limiting case may help explain the good mixing capabilities of these devices.
Conformal mapping analysis of infection mold filling
Authors: Ryan M. E. , Chung T.‐S. 
Published: December 2004

AbstractA conformal mapping analysis of the mold filling behavior in rectangular cavities is developed. The polymer melt is assumed to behave as a purely viscous Generalized Newtonian Fluid. The shape of the advancing flow front, the pressure distribution in the mold cavity, streamlines, constant temperature lines, and the required filling time may be readily determined using the techniques described. The theoretical results are in good agreement with experimental data previously reported in the literature.
Investigations on thermal and hydrolytic degradation of poly(ethylene terephthalate)
Authors: Zimmerman Heinz , Kim Nguyen Thac 
Published: December 2004

AbstractThe thermal properties of poly(ethylene terephthalate) (PET) are sensitively affected by polycondensation catalysts and temperature. The kinetics of thermal degradation were investigated by determining the rates of formation of carboxyl groups on isothermal heating. Carboxyl groups in PET were not only a result of thermal exposure but they were also an influence on hydrolytic stability. The hydrolytic cleavage of polyester chains, i.e., the formation of carboxyl groups, was found to be an autocatalytic reaction.
Photodegradation of polymers in solution as studied by laser flash photolysis
Authors: Schnabel Wolfram 
Published: December 2004

AbstractBy applying the light scattering detection method during flash photolysis experiments, causing main chain degradation of polymers, it is possible to study disentanglement diffusion of coiled macromolecules or the kinetics of the chemistry of main chain breakage. Results of typical experiments are presented. Poly(phenylvinylketone) was degraded at 347 nm in various solvents (disentanglement diffusion). Polystyrene was degraded at 265 nm in CHCl3 containing O2 (chemical reaction).
Direct evidence for the existence of a craze at the crack tip in environmental stress cracking of polyethylene
Authors: Bandyopadhyay S. , Brown H. R. 
Published: December 2004

AbstractLiquid nitrogen fracture tests have been carried out to produce direct evidence of the existence of a voided region, the craze, ahead of the crack in environmental stress cracking of polyethylene. Evidence of crazing is presented for both low and high density polyethylenes.
Calendering poly(vinyl chloride): Theory and experiments
Authors: Vlachopoulos J. , Hrymak A. N. 
Published: December 2004

AbstractAn isothermal model for the calendering of power‐law fluids which exhibit a slip boundary condition is presented. This model is based on lubrication approximation and Gaskell's theorxy. It Predicts sheet thickness, pressure distribution, velocity profiles, torque and power from rheological data for the melt and machine parameters. The predictions (sheet thickness, pressure distribution and torque) are compared with a set of experimental data for rigid poly(vinyl chloride)(PVC) provided to the authors by Solvay & Cie S.A.
An anomaly in the necking behavior of polyethylene, Part 3
Authors: Gedde U. W. , Terselius B. , Jansson J.‐F. 
Published: December 2004

AbstractDifferential scanning calorimetry (DSC) measurements, polarized light microscopy and scanning electron microscopy (SEM) studies are reported on neck fibers formed by constant uniaxial tensile loading of polyethylene specimens at temperatures ranging from 298 to 353 K. The DSC measurements indicate that the temperature of the melting peak (Tpeak) of the neck fibers is closely related to the fibrilinity, i.e., the content of complete fibrillar structure, and that Tpeak and thus fibrillinity of the fractured neck fibers is sensitive to the nominal stress in the region of marked transition. A previously proposed hypothesis concerning the appearance of a marked transition in the necking/fracture behavior of high density and high molecular weight polyethylene is thereby supported. The polarized light microscopy showed a correlation between the zone length of the transformation from spherulitic to fibrillar structure and the previously reported distinctness in neck formation. The crystallinity determinations obtained from the DSC measurements and the SEM observations confirmed the suggestion previously made that the density decrease in the fractured neck fibers of a high density polyethylene with Mn = 21.6 × 103 and Mw = 199 × 103 is a result of void formation.
Rheological characterization of polycaprolactam anionically synthesized in the presence of lithium chloride
Authors: Acierno D. , D'Amico R. , La Mantia F. P. , Russo S. 
Published: December 2004

AbstractMelt viscosity and dynamic‐mechanical data are reported for samples obtained by anionic polymerization of caprolactam, in the presence of LiCl. The full body of results is essentially in line with those previously reported relative to mixtures of inorganic salts and commercial nylon 6, In particular a drastic‐decrease of the melting point and of the rate of crystallization is confirmed as well as an increase of the glass transition temperature and of the melt viscosity. Some quantitative differences exist, which may be attributed to the different molecular weight distribution in the polymers employed in the present work.
A basic experimental study of sandwich injection molding with sequential injection
Authors: Young Sai S. , White James L. , Clark Edward S. , Oyanagi Yasushi 
Published: December 2004

AbstractAn experimental study of sandwich injection molding is reported which involves sequential injection of polymer melts with differing melt viscosity into a mold. In isothermal injection molding the relative viscosity of the two melts is the primary variable determining the phase distribution in the mold. Generally the most uniform skin‐core structure occurs when the second melt entering the mold has a slightly higher viscosity than the first melt injected. Large viscosity inequalities lead to nonuniform skin thicknesses. The influence of blowing agents and non‐uniform temperature fields on the extent of encapsulation is described. Temperature fields are very important especially if the first polymer melt injected has a greater activation energy of viscous flow (or a greater temperature dependence of the viscosity function).