bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of extruder dies using thermoplastics melt properties data
Authors: Powell P. C. 
Published: December 2004

AbstractThe procedures developed in this paper enable the die designer to estimate the dimensions of the die at the exit and to define a flow channel within the body of the die appropriate to the required dimensions and output rate of the extruded product. Design procedures are given for predicting die swell (and hence die exit dimensions) from a knowledge of product dimensions, output rate and the basic shear, elasticity, and viscosity data. Within the body of the die the length and included angle of a convergent tapered section should be such that the critical tensile deformation rate is not exceeded. At the die entry the taper angle is related to the tensile and shear viscosities. Analytical expressions based on flow data are given for predicting pressure drops resulting from flow through circular and slot dies of constant cross‐section and through conical and wedge‐shaped dies. A numerical example shows how the theory may be applied to the design of a die for a thin‐walled tube. For the resultant die design, the likely effects are predicted to changes in output rate and melt temperature for the chosen material, of changes in grade of the same type of polymer, and of changes in polymer type.
The concentration and possible source of unstable sites in PVC
Authors: Berens A. R. 
Published: December 2004

AbstractCopolymers of vinyl chloride with 2‐chloropropene were prepared as models for tertiary‐chlorine branching in PVC. Rates of thermal dehydrochlorination of copolymers containing up to 2 mol percent 2‐chloropropene were found to be a linear function of composition. By comparing the decomposition rates of the copolymers with that of PVC prepared under similar conditions, we estimate the maximum tertiary‐chlorine content of PVC at 0.1 to 0.2 mol percent. This figure is of the same magnitude as estimates of the content of tertiary‐chlorine, random unsaturation, and long‐chain branching obtained in previously published studies of PVC. Possible mechanisms for tertiary‐chlorine branch formation include chain‐transfer to polymer and copolymerization with unsaturated chain‐ends. By applying the conventional copolymerization equation, using the reactivity ratios of the vinyl chloride/2‐chloropropene system, it is shown that the copolymerization mechanism predicts a tertiary‐chlorine branch content close to the estimated value. Both mechanisms also agree qualitatively with reported effects of polymerization temperature and conversion on branching and thermal stability.
Melting of crystallites in polymers with low degree of crystallinity under shear flow conditions I: Poly(vinyl chloride)
Authors: Lyngaae‐Jørgensen J. 
Published: December 2004

AbstractThe aggregates found in dilute solutions of nearly atactic PVC have been shown to consist of 10 to 15 single molecules held together by a crystalline nucleus. Based on the postulate that the last crystallites in a PVC melt have the same structure as found in dilute solution, a relation between the melting temperature in shear (Tdyn), the static melting temperature (Tm) and the shear stress (τ) is found:

where Q is a constant. The model predictions are in accordance with data from a Brabender rheometer and a Rheometrics mechanical spectrometer. Q is found to be a constant for samples with weight average molecular weights in the interval between 70,000 and 160,000 corresponding to polymerization temperatures between 40 and 70°C.
PVC melt rheology III: The effect of order and molecular weight on the shear rate dependence
Authors: Collins Edward A. , Daniels Charles A. 
Published: December 2004

AbstractThe effect of polymerization temperature on the melt flow behavior of PVC of varying molecular weights has been studied over a wide shear rate range. For the same molecular weight, higher melt viscosities are observed for polymers prepared at lower temperatures. The shear rate dependence of the viscosity vs molecular weight plot is shown to be nonlinear over the shear rates examined. The inability to achieve a limiting zero‐shear viscosity is discussed.
Processing‐morphology‐property studies of poly(vinyl chloride)
Authors: Singleton C. , Isner J. , Gezovich D. M. , Tsou P. K. C. , Geil P. H. , Collins E. A. 
Published: December 2004

AbstractRecent morphological studies of plasticized and unplasticified poly(vinyl chloride) (PVC) are reviewed. Suspension polymerized PVC contains particles in a number of different size ranges 100–200Å, 1000–5000Å, 1μ and larger. The larger size particles are broken down during plasticization but both the 100Å and the 1000Å suspension particles retain their identity. The visibility, and presumably, coalescence of these particles is a function of the processing conditions. In particular, the size of the 100Å particle increases with plasticizer content and is most distinct as characterized both by small angle x‐ray scattering and electron microscopy for milling temperatures in the 160–170°C. range. Consideration is given to the effect of these particles, their structure, and interrelationship on the rheological properties of the resins.
A hysteresis in plasticized poly(vinyl chloride)
Authors: Deanin Rudolph D. , Shah Sharad B. , Kapasi Vikram C. , Pfister David H. , Putriment Paul 
Published: December 2004

AbstractPlasticized poly(vinyl chloride) formulations were prepared in solid and foam form, and mechanical hysteresis was measured by low‐speed tension and compression on an Instron tester and by high‐speed rebound on a resiliometer. Hysteresis was greatest in copolymers with vinyl acetate, at low plasticizer concentration, with inefficient plasticizers, at high concentrations of reinforcing fillers, at high expansion to low density, and at high speed of testing. Conversely, resilience was greatest at high plasticizer concentration, with more efficient plasticizers, with non‐reinforcing fillers, and at high density.
Liquid flow through aligned fiber beds
Authors: Williams J. G. , Morris C. E. M. , Ennis B. C. 
Published: December 2004

AbstractThe influence of surface properties on the flow of fluids, including epoxy resin, through aligned glass and other fiber beds has been examined. The observed flow rates were higher than those predicted from the Kozeny‐Carman equation, and were influenced by the surface properties of the fluid used. This is attributed to variations in the distribution of porosities and to the presence of air bubbles trapped during the initial wetting of the bed. The implications of these findings to the preparation of composites are discussed.
Mechanical properties of impregnated asbestos‐cement
Authors: Godard P. , Delvaux P. , Faille M. Della , Mercier J. P. 
Published: December 2004

AbstractThis study is devoted to the mechanical properties of impregnated asbestos‐cements. We studied the influence of the degree of impregnation and of the nature of the resin on the modulus of elasticity and on the strength of the materials. The impregnation of asbestos‐cement by polymeric resins produces composites of outstanding mechanical properties. The relative increase in flexural and tensile strength is much higher for mortar and concrete but the improvement produced by the polymer on asbestos‐cement is especially significant if one takes into consideration the already high absolute strengths of the materials.
Vapor and liquid equilibria in glassy polyblends of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide) Part I
Authors: Jacques C. H. M. , Hopfenberg H. B. 
Published: December 2004

AbstractThe equilibrium sorption of n‐hexane vapor and n‐hexane liquid in solution cast films of polystyrene, poly(phenylene oxide), and blends of these homopolymers was studied over a significant range of penetrant activity and temperature. These equilibrium sorption measurements were supplemented by density determinations, refractive index measurements, differential scanning calorimetry and differential thermal analysis. A seemingly complicated pattern of results emerged when the equilibrium penetrant content was plotted as a function of blend composition. At relatively low activity and temperature the equilibrium concentration of n‐hexane in these films monotonically increased with poly(phenylene oxide) content in the blend. Conversely, at high activities and in unit activity liquid, the equilibrium penetrant concentration exhibited a distinct minimum when plotted as a function of blend composition. At higher activities, solvent induced crazing accompanied the sorption of penetrant. These results were explained consistently by considering the nature of the sorption isotherm over an activity range sufficient to lower the glass transition temperature, of the equilibrated and swollen blend, below the temperature of the sorption experiment. Most importantly, the interpretation and explanation of these data are based upon phenomena common to all glassy polymer‐organic penetrant systems and no special properties of this blend system were included in the analysis. The results, therefore, reflect the apparent homogeneity of polystyrene‐poly (phenylene oxide) blends and are useful in considering the equilibrium of penetrant sorption in glassy polymers as a general class of materials.
Why do polymer molecules fold?
Authors: Lindenmeyer Paul H. 
Published: December 2004

AbstractIn the process of transforming from liquid to crystal, a polymer molecule must assume conformations which cause it to have a higher free energy than either the liquid or the crystal. This free energy barrier to crystallization is minimized if the molecule folds, thus providing both the driving force for folding as well as the assurance that the crystallization behaves as a classical kinetically‐controlled process. This free energy barrier exists equally well for the melting of extended chain crystals accounting for their observed super‐heating. Finally these ideas can be extrapolated to predict some rather unconventional conclusions with regard to polymer conformation in the melt.
Lithography and radiation chemistry of epoxy containing negative electron resists
Authors: Thompson L. F. , Feit E. D. , Heidenreich R. D. 
Published: December 2004

AbstractA class of negative electron‐beam resists is described which have excellent lithographic characteristics. The resists are copolymers of glycidyl methacrylate and ethyl acrylate. Their molecular weights, epoxy contents, and polydispersivities can be controlled to give an adjustable range of electron sensitivity and contrast. The copolymers are compared to other epoxy containing, negative electron‐beam resists.Micrography of resist profiles generated from a single line scan of the electron beam have been used to illustrate the complex interaction of accelerating voltage of the electron beam and resist contrast on resolution. Optical gratings made from single line scans of the beam have feature sizes less than 300 nm in the resist, etched metals, and dielectrics.
Linear polycarboranesiloxanes
Authors: Roller M. B. , Gillham J. K. 
Published: December 2004

AbstractAspects of the present status of structure‐property correlations for linear polycarboranesiloxanes which contain rigid carborane cages and flexible siloxane in‐chain linkages are discussed. Low temperature secondary transitions, glass transitions, crystallization and melting transitions, and high temperature chemical transformations in inert and air atmospheres are emphasized. The linear polymers serve as the basis for new high‐temperature elastomers.
16‐Year creep of polyethylene and PVC
Authors: Findley William Nichols , Tracy Joseph Francis 
Published: December 2004

AbstractCreep tests at constant values of tensile stress, temperature, and relative humidity for two thermoplastics were conducted for approximately 132,000 hr. The strains, ϵ, for the first 2000 hr of time, t, were described by an equation of the form ϵ = ϵo + ϵ+tn where all other symbols are constants. This equation was found to predict the creep of poly(vinyl chloride) for approximately 132,000 hr with reasonable accuracy. The predicted strains for polyethylene (density 0.924) were somewhat low. Strains during unloading and reloading after 90,000 hr of creep were predicted reasonably well by the Boltzmann superposition principle.
Pressure generation mechanisms in the feed section of screw extruders
Authors: Lovegrove J. G. A. , Williams J. G. 
Published: December 2004

AbstractThe generation of pressure in the feed section of an extruder is analyzed. It is concluded that body forces must be considered since they provide the necessary conditions for pressure initiation. Solutions are given which take into account gravity forces in both vertical and horizontal screws together with centrifugal force. Some numerical results are also given which illustrate the practical importance of these effects.
Characterization of mechanical properties of thermoplastic films by creep measurements
Authors: Huntsberger J. R. 
Published: December 2004

AbstractPlasticized poly(methyl methacrylate) and methyl methacrylate/acrylate copolymer films were examined by isothermal creep at low loads measured at several temperatures from ∼Tg to Tg + 15°C. Viscosity calculated using η = σ/3\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document} was plotted vs temperature giving precise values for Tg based on a viscosity criterion of η = 1013 poises. Creep fracture data at various temperatures below Tg were interpreted using the maximum apparent viscosity measured at the minima of strain rate vs strain curves. Plots of ηmax VS stress at several temperatures gave values of ΔTg/Δσ of −1° to 2°C/106 N/m2 in agreement with treatment of ΔTg/Δσ based on free volume. Fracture occurred at low elongations when ηmax was ≥1013 poises, and at higher elongations when ηmax was <1013 poises supporting the concept that fracture is related to the lowering of Tg under stress. Plots of log σ VS log εb (the elongation at fracture) had the same form as that for crosslinked elastomers above Tg reported by T. L. Smith. Plots of log \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}b VS log εb also had the same form supporting proposals on the rate sensitivity of fracture.
Behavior of zirconium compounds in polymers—A review
Authors: Blumenthal Warren B. 
Published: December 2004

AbstractZirconium compounds dispersed in polymers often bond the polymer molecules together, increasing their stability. This can generally be attributed to the formation of covalent bonds between zirconium atoms and small atoms of high electronegativity of the polymer molecule, to overlapping of pi orbitals of unsaturated moieties of the organic compound with sigma orbitals of the zirconium atoms, to fractional bond formation between zirconium and organic hydrogen, and to combinations of these. Bonding and its effects on physical properties have been achieved by molecular dispersions of zirconium compounds in the polymer, by dispersion of insoluble particles of zirconium compounds, and through residues from zirconium catalysts used in polymer preparation. Coatings and plastic components have been improved in strength and in durability by the dispersions. Compounds of other metals often perform similarly. The totality of relevant properties of zirconium compounds often leads to their preferential use.
Polymer‐glass separation in the spiral mold test
Authors: Kubát Josef , Szalánczi Akos 
Published: December 2004

AbstractThe spiral mold method (moldability test) was used in a study of phase separation occurring in glass‐containing polyethylene and polyamide melts. Pronounced separation effects were recorded for low density polyethylene containing 25 percent glass spheres with diameters ranging approximately from 50 to 100 μm, the glass concentration at the tip of the spiral exceeding 40 percent by weight. For melts containing smaller spheres or fibers the effect was of the order of a few percent. There was a decrease in glass concentration near the center of the spiral.
Maximum pressure developed by solid conveying force in screw extruders
Authors: Chung Chan I. 
Published: December 2004

AbstractThere are two distinct solid conveying theories that can be applied to plasticating screw extruders. One is Darnell and Mol's theory based on a solid‐to‐solid friction model and the other is Chung's theory based on a viscous shearing model. The two theories predict very different solid conveying performances for a same set of conditions. In this paper, the maximum pressures that can be developed inside plasticating screw extruders by the solid conveying force are calculated using each of the two theories. Comparison of the results may shed some light on the applicability of each theory for a particular extrusion operation.
Allyl fluoride copolymers
Authors: Waterman J. A. , Shorr L. M. , Shaham I. 
Published: December 2004

AbstractAllyl fluoride can be copolymerized with vinyl chloride, vinyl acetate, ethyl acrylate, or SO2 using free radical types of initiation. The copolymerization of allyl fluorida with vinyl chloride is comparable to the free radical initiated copolymerization of propylene with vinyl chloride. The allyl fluoride‐vinyl acetate couple tends to form completely random copolymers, the reactivity ratios of the monomers being close to unity.
The thermal conductivity of nickel and copper dispersed in poly(vinyl chloride)
Authors: Kusy Robert P. , Corneliussen Roger D. 
Published: December 2004

AbstractThe thermal conductivity of segregated distributions of poly (vinyl chloride)/nickel (PVC/Ni) and poly(vinyl chloride)/copper (PVC/Cu) was measured for volume fractions ranging from 0 to 0.15. The thermal conductivities increased from 0.15 Btu/hr ft °F for unmodified PVC to 2.79 Btu/hr ft °F for PVC/15 percent Cu. While the thermal conductivity increased smoothly with volume loading, the electrical resistivity decreased discontinuously over fifteen orders of magnitude. Using the parallel slab model as a basis, a semi‐empirical model was deduced which described the thermal conductivity as a function of volume loading. With this work, a survey of the thermal, electrical, and mechanical properties of segregated PVC composites is complete.
Mecahnics of composites
Authors: Nicolais L. 
Published: December 2004

AbstractThe fundamental analysis of the mechanical response of composite media involves investigations on two levels of abstructions: the micro and the macro scale. These areas of study are known as micromechanics and lamination theory. This format is employed to treat a series of problems concerning (1) stiffness, creep, or viscoelastic properties; (2) strength and expansion properties for oriented continuous and short fibers; (3) randomly oriented fibers; (4) injection‐molded materials; and (5) particulate reinforcements.
Engineering potential of composite materials
Authors: Crivelli‐Visconti Ignazio 
Published: December 2004

AbstractThis note illustrates how the development rate for the use of composites as engineering materials has recently increased. Reasons for the expected even larger number of applications of composites in industry is explored. The engineering potential of composites is outlined in terms of properties and design aspects and mainly by pointing out how the proper use of a composite requires a clear knowledge of its application as well as the appropriate design technology. Examples of applications in different fields are reported with the aim of showing the high versatility of composites for a variety of engineering applications. The final part is devoted to cost aspects, which are considered in connection with the effects of composite use upon the total structure. The purpose is to show that a large number of interesting applications are already cost effective.
Ultra‐high‐modulus fibers from solution spinning
Authors: Ciferri A. 
Published: December 2004

AbstractUltra‐high‐modulus fibers such as Du Pont PRD‐49 (initial modulus up to ∼1000 g/den) and Monsanto X‐500 (initial modulus up to ∼600 g/den) are spun from solutions. Both polymers are characterized by a high intrinsic rigidity of individual molecular chains and considerable orientation along the fiber axis. The thermodynamics of solution for rigid and semirigid macromolecules is critically reviewed in order to illustrate conditions under which spontaneous formation of highly oriented fibers is expected. In the case of semirigid polymers, the free energy of (random) mixing pure solvent and parallellized polymer may, according to Flory, become positive for some critical value of a “flexibility parameter.” Formation of an ordered phase for semirigid polymers is not, however, observed by lowering temperature or increasing polymer concentration. In the case of rod‐like polymers, still according to Flory, at some critical value of polymer concentration (which decreases with the axial ratio of the macromolecule) the isotropic solution of rods undergoes phase separation with formation of a partly ordered solution. This theoretical prediction is satisfactorily verified by data. While Du Pont fibers are spun from this anisotropic solution, Monsanto's X‐500 only yields an isotropic solution at room temperature up to the limit of polymer concentration at which crystallization occurs. This inability of X‐500 to form anisotropic solutions at the expected critical concentration is attributed to a partial degree of flexibility. Mechanical properties and orientation of fibers spun from the anisotropic solution appear to be superior to those obtained by spinning from isotropic solution, according to Du Pont's results. When a polymer has a partial degree of flexibility, alteration of physico‐chemical variables such as solvent type, solvent composition, temperature, and polymer concentration may still be used in order to increase its rigidity. Theoretical arguments and data supporting this contention are discussed. Moreover, alteration of these variables may also be used to alter the crystallization temperature, allowing formation of the anisotropic solution to occur at a high enough polymer concentration. This expectation was verified in the case of X‐500. Finally, the all important role of mechanical orientation of solutions is emphasized. According to Hermans, under high enough shear stress, the difference between the isotropic and the anisotropic solution vanishes. In line with these consideration, drawing techniques are particularly useful in order to achieve almost‐perfect orientation and theoretical moduli.
Polymer modulus and morphology: The tensile properties of polyethylene
Authors: Porter Roger S. , Southern John H. , Weeks Norman 
Published: December 2004

AbstractThe general properties of a novel process for producing high modulus polyolefins are discussed. The technique is an extrusion drawing involving a crystal‐crystal transformation. The principal tests have been made on polyethylene and the guidelines have been established for extending the technique to other polyolefins. The characterization of such materials is extensively discussed, particularly in the light of the concept of continuous crystals.
Ultra‐high‐modulus linear polyethylene through controlled molecular weight and drawing
Authors: Capaccio G. , Ward I. M. 
Published: December 2004

AbstractRecent work is presented on the plastic deformation of linear polyethylenes. This work demonstrates the importance of molecular weight and initial morphology in determining the drawing behavior, and shows that by appropriate choice of these two factors a substantial increase in draw ratio and hence stiffness can be achieved over conventionally‐oriented polyethylenes. Under optimum conditions a modulus of approximately 700 Kbar was obtained at a draw ratio of ∼30. These very high modulus materials displayed an extensibility to break of at least 3 percent and a strength of about 4 Kbar. In some cases they also exhibited very high melting points (∼139°C) and exceptionally good thermal stability.