bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic mechanical properties of high nitrile resins
Authors: Yanik R. W. , McMaster A. D. 
Published: December 2004

AbstractDynamic mechanical measurements have become increasingly more common as an interpretative tool for identifying structure‐property relationships in polymers, especially in multi‐phase systems. There are many literature references citing the application of this analytical technique to the study of rubber reinforced polymers such as high impact polystyrene and aerylonitrile‐butadiene‐ styrene. This paper illustrates further extensions of the technique to study the effects of composition and processing parameters on the mechanical relaxation behavior of rubber reinforced high nitrile resins. Storage and loss curves vs temperature are compared for three related polymer systems: (1) a high nitrile glassy copolymer, (2) mechanical blends of the glassy copolymer with rubber, and (3) a copolymer grafted onto a rubber backbone. Particular attention is given to the size and shape of the tan δ loss peak for blended and grafted resins having different rubber levels. The importance of dispersing the rubber particles during processing is also shown. Dynamic mechanical studies have shown a pronounced decrease in the size of the rubber loss peak for oriented rubber modified high nitrile resins. This is further evidence that dynamic mechanical results are sensitive to variations in processing conditions as well as resin composition.
Polymer compatibility: Ternary blends of poly(vinylidene chloride‐co‐vinyl chloride), poly(vinyl chloride) and poly(acrylonitrile‐co‐butadiene)
Authors: Wang Yung‐Yun , Chen Show‐An 
Published: December 2004

AbstractMixtures of two compatible polymers, poly(vinyl chloride) and poly(acrylonitrile‐co‐butadiene) containing 40 percent acrylonitrile, can be compatible with poly(vinylidene chloride‐co‐vinyl chloride), which is incompatible and partially compatible respectively with these two polymers. The crystalline melting temperature and relative heat of fusion of poly(vinylidene chloride‐co‐vinyl chloride) in blends are higher than those in the pure component. This is attributed to greater ordering of the polymer chains in the crystalline phases of the blends. Replacing the rubber by poly(acrylonitrile‐cobutadiene) containing 30 percent acrylonitrile, shows that these three polymers, in which each pair is incompatible or at most partially compatible, also form compatible ternary blends. The crystalline melting temperature is higher and relative heat of fusion lower than those in the pure component. This is attributed to dissolving of parts of the polymer chains originally located in the crystalline phases in the amorphous phases of the blends.
Properties and processing characteristics of open‐celled foams produced by leaching NaCl from high density polyethylene
Authors: Bigg D. M. 
Published: December 2004

AbstractThe properties and processing characteristics of open‐celled foams produced by leaching small NaCl particles from high density polyethylene has been investigated. In a random dispersion of salt particles in the polymer matrix a minimum volume loading of 40 percent was required to produce an open‐celled foam. The time required to remove this quantity of salt with 50°C water was 100 min. The maximum porosity of the foam is limited to the maximum packing fraction of the salt. For randomly dispersed isotropic particles the maximum packing fraction is approximately 0.64. Because the composite rapidly loses melt strength as the filler content nears the maximum packing fraction, the practical upper limit of extruded foam porosity is approximately 0.60.
The melting behavior of a low density polyethylene powder in a screw extruder
Authors: Cox A. P. D. , Williams J. G. , Isherwood D. P. 
Published: December 2004

AbstractAn experimental investigation into the performance in general and the melting behavior in particular of a single screw extruder running with a low density polyethylene power has been carried out and the results compared with those for a granular feedstock of low density polyethylene having similar melt properties. It was found that the tendency was for the output rate, pressure generated and specific power consumption to be lower for the powders, and that the removal of barrel heating near the feed hopper increased these parameters. Two melting mechanisms were observed in powder extrusion; one being the classic “Maddock” type, and the other such that the solid bed and melt pool were in reversed positions relative to the Maddock case. There was a trend for this latter mechanism to operate with low screw speeds, shallow channels and full heating. Melt initiation occurred nearer the feed end and melting was completed much more quickly with powders. An explanation of the mechanisms is proposed which is based on the observation of early melt initiation, and the industrial practices of feed zone cooling and increasing feed pressure generation to improve the performance of extruders running with powders are seen to be consistent with this proposition.
Study of the curing of a polyurethane using the Weissenberg Rheogoniometer
Authors: Hartley Mark D. , Williams H. Leverne 
Published: December 2004

AbstractGel Permeation chromatography (GPC) yielded high values for branching frequency. Low polymers persisting long into the reaction and impurities resulted in almost constant number average molecular weights and steeply rising polydispersity. The percent insolubles was low and passed through a maximum attributed to a 1,2,3‐propantriol/isocyanate reaction product which was insoluble and became solubilized by the addition of polybutadiene. The dynamic viscosities of the products rose with conversion. When studied over various shear rates, the curves could be extrapolated to zero shear values. The relationship between zero shear viscosity and molecular weight yielded a slope of 3.5 for linear samples and a lightly branched sample prepared using 1,6‐hexamethylene diisocyanate. The lightly branched samples made using 2,4‐toluene diisocyanate yielded slopes less than 3.5. The highly branched samples yielded slopes well above 3.5. The moduli increased rapidly with reaction time and then levelled off. In the absence of 1,2,3‐propantriol, the loss modulus surpassed the storage modulus. When 1,2,3‐propantriol was added, the moduli increased more rapidly, levelled off at higher values, and the storage modulus exceeded the loss modulus. Studies of the swelling of the final product showed that these measurements yielded abnormally high values for the molecular weight between crosslinks; evidence of poor network formation.
Rheology of polyphosphazene melts and solutions—some surprises
Authors: Ho Perry K. , Williams Michael C. 
Published: December 2004

AbstractRheological tests are reported for two types of polyorganophosphazenes, one being a fluorinated alkoxy terpolymer (PNFT) and the other an aryloxy copolymer (PAP). Non‐Newtonian viscosity η(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) and complex viscosity components η′(ω) and η″(ω) were measured as functions of shear rate\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}and oscillatory frequency ω, using a Weissenberg rheogoniometer, and a limited amount of normal stress data was also obtained. Solutions of both polymers in tetrahydrofuran were tested, over a concentration range 0‐22 percent for PNFT and 0‐35 percent for PAP. Melts of PNFT were examined for temperatures 50‐178°C, and melts of PAP at 210°C even though they were not truly fluid at this temperature. Solution and melt data are shown to obey conventional superposition principles to give master curves. For solutions, superposition is achieved by using the Bueche relaxation time as a concentration reducing factor with no adjustable parameters, and the Spriggs model also proves useful in predicting normal stress and shear stress results. For PNFT melts, master curves are fitted by the new WS2H2model which incorporates detailed molecular weight distribution (MWD) information and extracts the entanglement lengthMefrom the data. Temperature shift factorsaTshow Arrhenius behavior and the corresponding activation energiesEreare reported. Results for PNFT melts were complicated by lack of agreement between two samples of nominally the same composition; η′(ω) shapes and levels andErevalues differed widely. This is interpreted in terms of detailed MWD information and the possibility of mesomorphic phase transitions occurring in these nominally amorphous materials.
Torsion impregnated cloth analysis (TICA): A forced torsion technique to study resins supported by inert substrate
Authors: Lee C. Y‐C. , Goldfarb I. J. 
Published: December 2004

AbstractTorsion Impregnated Cloth Analysis (TICA) uses fiber glass cloth as support for polymeric resins and measures the clothresin composite's in‐phase and out‐of‐phase dynamic mechanical responses with a Rheometrics mechanical spectrometer. The TICA thermoscan results of a thermoplastic were compared with that of the neat material. A similar comparison was made between the isothermal curing results of a thermosetting resin and the corresponding parallel plate and TBA measurements. The peaks associated with the vitrification were verified to correspond to those in the glass transition region. Conventional thermoscans of partially cured specimens with known Tg were shown under certain conditions to give erroneous results about the glass transition temperatures. A reduced parameter (T‐Tg) was introduced to describe the response of a specimen undergoing additional cure while being subjected to a thermoscan. Examples using this parameter to understand seemingly complex experimental results are given.
Dynamic properties of crosslinked epoxy resin at large cyclic and static deformation
Authors: Isayev A. I. , Katz D. , Smooha Y. 
Published: December 2004

AbstractMeasurement of dynamic properties of crosslinked epoxy resin have been performed under torsional cyclic deformation with different amplitudes and frequencies and with extensional creep under different loads. It is found in both cases that the dynamic modulus decreases above a certain critical value of deformation. Truncation of the glassy state region and shifting of the transition zone to lower temperatures and higher frequencies have been observed as effects of large amplitude deformation. The maximum reduction in the modulus value and the minimum in the critical amplitude both occur in the region of Tg Shear fatigue of the material has been observed in the glassy state with a frequency‐ and temperature‐dependent fatigue life. It is found that the loss modulus under extensional creep depends upon the values of the deformation and stress whereas the storage modulus depends solely upon the deformation. The ratio of energy expended during static and cyclic deformations is shown to depend only upon the extensional deformation.
Plasma polymerization of hexamethyldisiloxane in the gas phase. II. Formulation of various selected parameters affecting rate of polymerization and their optimization
Authors: Akovali G. 
Published: December 2004

AbstractFormulation of three selected operational parameters (flow rate of monomer, radio frequency power applied, and reactor tube pressure) affecting rate of polymerization of HMDS by plasma at 13.56 MHz is made by use of rotatable central composite (RCC) statistical design. The flow rate is found to be the most important parameter in determining deposition rate, followed by power and pressure; optimum values of these three to yield maximum deposition rate are also evaluated.
Time‐dependent rheological properties and transient structural states of entangled polymeric liquids—A kinetic network model
Authors: Liu T. Y. , Soong D. S. , Williams M. C. 
Published: December 2004

AbstractA kinetic network model has been developed to describe the nonlinear rheological behavior of entangled polymer solutions and melts in either steady‐state or transient flows. This model is based on the concept of flow‐induced structure variation, controlled by the simultaneous existence of entanglement loss and regeneration. When steady‐state is attained, both processes occur at the same rate and the structural state (entanglement density) of the fluid remains constant with time. Under transient flow conditions, the fluid structure becomes time‐dependent as a result of unequal rates of the two competing processes affecting entanglement density. The viscoelastic response of the fluid is, in turn, influenced by the varying structural state. This is incorporated into the model through the use of structure‐dependent coefficients in the contravariant Maxwell constitutive equation for entanglement stress. Model predictions are generated for a number of transient flow programs, including the stress growth and relaxation, interrupted flow, sudden change in shear rate, and nonlinear creep experiments. Comparison with literature data supports not only the qualitative success but also the quantitative ability of this model.
The determination of residual stresses in plastic pipe and their role in fracture
Authors: Williams J. G. , Hodgkinson J. M. , Gray A. 
Published: December 2004

AbstractA method for the determination of residual stresses in plastic pipe by layer removal and subsequent slitting is described. Results are analyzed from deflections measured on a high density polyethylene pipe. The use of these data in the calculation of KI around a semi‐elliptical flaw at the pipe wall is then discussed.
Computer simulation of steady polymer melt spinning
Authors: Gagon Del Kenneth , Denn Morton M. 
Published: December 2004

AbstractAn interactive computer simulation program has been developed for steady polymer melt spinning. The program includes inertial and air drag effects, and fluid viscoelasticity is described by the Phan‐Thien and Tanner constitutive equation. Simulation results are compared with experiments by George on poly(ethylene terephthalate) (PET) at spinning speeds of 1000 and 3000 m/min, and the effect of elasticity under other spinning conditions is explored with computer experiments.
Effect of tensile strain, time, and temperature on gas transport in biaxially oriented polystyrene
Authors: Levita Giovanni , Smith Thor L. 
Published: December 2004

AbstractThe permeability and diffusion coefficients (P and D) for gases in a biaxially oriented polystyrene film have been found to increase when a specimen is stretched in simple tension and to decrease with time when the strain is held constant. These effects are attributed, respectively, to an increase in free volume with strain and to the continuous volume recovery (densification) at constant strain. The strain dependence, at small strains, of P and D for Ar, Kr, N2, CO2, and Xe at 1 atm pressure and 50°C indicates that the size distribution of free‐volume elements is not distorted when a specimen is stretched. At a constant strain of 1.8 percent at 50°C, P and D for xenon decrease about 13.8 and 11.8 percent, respectively, per decade of time—two to threefold faster than for carbon dioxide. These results and those obtained with argon, whose molecular diameter is significantly smaller than that for xenon, suggest that the larger free‐volume elements decrease in size faster than the smaller ones as volume recovery progresses.
Effect of physical aging on stress relaxation of poly(methyl methacrylate)
Authors: Cizmecioglu M. , Fedors R. F. , Hong S. D. , Moacanin J. 
Published: December 2004

AbstractA study was made on the stress relaxation behavior at 25°C of poly(methyl methacrylate) in uniaxial tension as a function of physical aging at both room temperature and 60°C. Test specimens were compression molded at 165°C, then quenched to room temperature and allowed to age for up to 30 days prior to testing. Stress relaxation curves measured after different aging times could be superposed to a single master curve for each aging temperature. Superposition was achieved by applying vertical and horizontal shifts. Hence, the shape of the response curves was not changed by aging. This is in accordance with observations made by Struik for tensile creep curves. Volume changes as a function of physical aging were also determined. Simple exponential relationships were observed between volume and both horizontal and vertical shifts. The horizontal shift implies a shift in the effective time scale caused by a change in free volume. The vertical shifts could be correlated with changes in Young's modulus caused by a change in density. For the range of aging studied, the response time scale varied over nearly two decades of log‐time. For the same conditions modules varied by 30 percent.
The inhomogeneous structure of glass
Authors: Lindenmeyer P. H. 
Published: December 2004

AbstractApplication of the fundamental variational principle of nonequilibrium thermodynamics has permitted recognition that all polymer solidification including glass formation occurs by a dissipative process which results in an inhomogeneous dissipative structure rather than an equilibrium structure. Although an equilibrium structure must he homogeneous and time independent, the definition of both homogeneity and time independence depends upon the scale and precision of the measurement of time and distance. Thus, whether one considers a glass to be a homogeneous equilibrium structure or an inhomogeneous nonequilibrium structure, depends upon the scale and precision of measurement. However, progress in understanding the molecular arrangement in glass can only come by considering a glass as an inhomogeneous dissipative structure.
Mass transfer and depolymerization of styrene in polystyrene
Authors: Blanks R. F. , Meyer J. A. , Grulke E. A. 
Published: December 2004

AbstractThis work shows how laboratory experiments may provide parameters which are useful in modeling a commercial process of polystyrene devolatilization. Such processes often occur at temperatures where depolymerization of polystyrene to monomer may be significant. Polystyrene devolatilizers function by forming thin films of the polymer, with styrene loss by flashing and diffusion and styrene generation by depolymerization. The modeling parameters of importance are: depolymerization rate constant, monomer diffusivity, and thermodynamic equilibrium polymer‐vapor partition coefficient. Typical levels of styrene in polystyrene in the last stage of devolatilization are 100 to 1000 ppm. Pressures and temperatures in the devolatilizer are often less than 10 torr and greater than 200°C. For styrene‐polystyrene the desired parameters have not been reported, nor apparently measured, at the concentration, pressure and temperature levels of interest.
Adhesive and composite evaluation of acetylene‐terminated phenylquinoxaline resins
Authors: Hergenrother Paul M. 
Published: December 2004

AbstractA series of acetylene‐terminated phenylquinoxaline (ATPQ) oligomers of various molecular weights were prepared and subsequently chain extended by the thermally induced reaction of the ethynyl groups. The processability and thermal properties of these oligomers and their cured resins were compared with that of a relatively high molecular weight linear polyphenylquinoxaline (PPQ) with the same chemical backbone. The ATPQ oligomers exhibited significantly better processability than the linear PPQ but, the PPQ displayed substantially better thermooxidative stability. Adhesive (Ti/Ti) and composite (graphite filament reinforcement) work was performed to evaluate the potential of these materials for structural applications. The PPQ exhibited better retention of adhesive and laminate properties than the ATPQ resins at 260°C after aging for 500 h at 260°C in circulating air.
Mechanical and thermal properties of aromatic copolyesters containing rigid binaphthyl units
Authors: Manusz J. , Lenz R. W. , Macknight W. J. 
Published: December 2004

AbstractMechanical and thermal properties of terephthalic acid copolyesters of 4,4′‐binaphthol‐1,N monomer, and 2,2‐bis(4‐hydroxyphenyl)propane, A monomer (Bisphenol A), have been examined by differential scanning calorimetry (DSC) and dynamic mechanical methods. The copolyesters had different amounts and sequence distributions of diphenolic units. When the content of N units in the copolyesters was increased from 27 to 55 percent a significant increase of the dynamic Young's modulus, from 2485 to 4540 MPa at 110 Hz and room temperature, and an enhancement of the stress at yield, from 53.5 to 66.5 MPa, were observed. In the glass transition region of the copolyesters a smaller decrease in the value of E′ was noted compared with the homopolymers. For the copolyesters containing 55 percent of N units, the E′ decrease was only about 1.6 decades at 110 Hz within a range of temperatures of over 74 Kelvins. The DSC measurements of the copolyesters under consideration showed that the Tg depended only to a slight extent on their composition and structure and all Tg values were within the range of 494 ± 2 Kelvins, corresponding to that for poly [2,2‐bis(4‐ hydroxyphenyl)propane terephthalate], the homopolymer of the A bisphenol monomer.
Pressure development in the melting zone of a single‐screw extruder
Authors: Lindt J. T. 
Published: December 2004

AbstractAn analysis is given of the pressure generation mechanism in the tapered channel of a single‐screw extruder. It is shown that when increasing the throughput the pressure build‐up capacity of the melting zone tends to decrease. As a result, severe pressure drops may occur in the tapered sections. A relationship between the pressure profile and the melting mechanism (solid bed/melt pool configuration) is described in terms of the cross‐channel melt circulation.
Residence time distribution in a real single screw extruder
Authors: Kembłowski Z. , Sȩk J. 
Published: December 2004

AbstractThe residence time distribution in an industrial single screw extruder was investigated experimentally in the case of melt and plasticating extrusion. The investigations performed proved that the extrusion parameters influence strongly the residence time distribution in the extruder. It was found that the resistance to flow through the die‐head of the extruder is very important from this point of view, as well as other parameters like rotational speed of the screw and the screw channel depth. Variation of these parameters can change the residence time distribution over a broad range between the extreme idealized cases of plug flow and flow with perfect mixing. In order to obtain quantitative dependences three moduli were used and a correlation equation was obtained. This equation enables an estimation of residence time distribution on the basis of experimental characteristics of the extruder and the actual extrusion parameters.
Addition polyimide adhesives containing various end groups
Authors: Clair Anne K. St. , Clair Terry L. St. 
Published: December 2004

AbstractAddition polyimide oligomers have been synthesized from 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride and 3,3′‐methylenedianiline using a variety of latent crosslinking groups as end‐caps. The nominal 1300 molecular weight imide prepolymers were isolated and characterized for solubility in amide, chlorinated and ether solvents, melt‐flow and cure properties, glass transition temperature, and thermal stability on heating in an air atmosphere. Adhesive strengths of the polyimides were obtained both at ambient and elevated temperatures before and after aging at 232°C. Properties of the novel addition polyimides were compared to a known nadic end‐capped adhesive, LARC‐13.