bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of light and heat on the rubber content and impact strength of acrylonitrile‐butadiene‐styrene
Authors: Bair H. E. , Boyle D. J. , Kelleher P. G. 
Published: December 2004

AbstractDSC analysis of acrylonitrile‐butadiene‐styrene (ABS) samples either weathered outdoors for up to 10 years or aged at 71°C has shown that these plastics deteriorate most readily through the polybutadiene (BD) component. Oxidation of the BD in ABS leads to an increasing and broadening Tgas well as a decrease in ΔCp at Tg. The latter quantity can be used to quantitatively assay the amount of unoxidized rubber in a photo‐ or thermal‐oxidized sample. The loss of impact strength of these resins with chemical aging can be correlated with the oxidation of the polybutadiene phase. Studies of rubber content as a function of sample thickness have revealed that an embrittled layer containing oxidized BD develops at the surface of an aged, 100 mil. ABS plaque (natural) and grows to a thickness of about 10 mils after 3 years exposure to sunlight. ABS containing carbon black is effectively screened from this photo induced degradation and consequently has much better retention of its initial impact strength values. In addition, carbon black was observed to retard thermal oxidation in some ABS samples. Lastly, it appears possible to do accelerated aging studies at elevated temperatures to evaluate the relative stabilities of various ABS formulations.
Co‐extrusion of polymers with one single screw having a specially devised double channel
Authors: Iwakura Kenji , Fujimura Toshikazu 
Published: December 2004

AbstractCo‐extrusion by means of only one single screw with a double channel was studied. The effects of the operating conditions, the material properties and the screw geometries on the inter‐channel flow and the output rate were determined. The flow mechanism and the application to the composites with stratified structures were discussed. The inter‐channel flow rate decreased with decrease in the back pressure, the stock temperature, the screw rotational speed and the viscosity difference between polymer melts in both channels. The decrease in the compression ratios of channels, the barrier flight in the compression zone and the sealing at the flight clearance with the polyamide‐packing reduced the inter‐channel flow significantly without a decrease in the output rate. With this method, co‐extrudates with distinctly stratified cross‐sections were prepared. The single screw with double‐channel could be applied effectively to the co‐extrusion of composites with stratified structures such as sheath‐and‐core structures, and it is particularly suitable to distribute the additives heterogeneously or to enclose the waste polymer.
Rheology of molten blends of polyoxymethylene and ethylene‐vinyl acetate copolymer and the microstructure of extrudates as a function of their melt viscosities
Authors: Tsebrenko M. V. , Rezanova N. M. , Vinogradov G. V. 
Published: December 2004

AbstractBlends of polyoxymethylene (POM) with a copolymer of ethylene and vinyl acetate (CEVAc) have been studied. The effect of viscosity ratio for melts of the components on the processes of fiber formation in extrudates and on the rheological properties of the molten blend has been tested. The viscosity ratio of the fiber‐forming POM and the matrix varied in the range 0.35‐27.7. POM ultrathin fibers of unlimited length can be formed in the CEVAc only at a viscosity ratio close to unity. For ratios much greater than unity, the extrudate is found to contain short fibers and a finely dispersed powder or no fibers at all. If the viscosity of the POM melt is lower than that of the matrix, films are formed in addition to fibers. The second factor that governs fiber formation is the extrusion shear stress. An optimum shear stress exists at which the amount of ultrathin fibers is a maximum.
Shear‐rate‐dependent viscosity of non‐Newtonian suspensions and entangled polymer systems
Authors: Soong David , Shen M. 
Published: December 2004

AbstractA simple equation is proposed to calculate the shear‐rate‐dependent viscosities of entangled polymers and particle suspensions. The rate‐dependence of the viscosities is attributed to changes in certain structural parameters associated with the fluids, such as entanglement density or degree of particle agglomeration. The state of these structural parameters for fluids subjected to a given shear flow is determined by two competing process, i.e., structural breakdown and reformation, which in steady How arc in a state of dynamic equilibrium. For the polymer systems structural degradation and reformation are tantamount to entanglement loss and creation, whereas for the suspensions they are correlated with the particle breakup and flocculation. The regeneration process is driven by thermal diffusion and is assumed to be independent of shear rate. The degradation process is caused primarily by the imposed shear and is assumed to be proportional to the shear rate to a power m (0<m<1). Based on these assumptions, structural variation for fluids undergoing not only steady‐state but a I so transient flows can be calculated. Model predictions and their implications are discussed. The derived equation can be applied to many non‐Newtonian pseudo‐plastic fluids.
Analysis of plasticizer activity in cellulose esters
Authors: Seymour R. W. , Minter J. R. 
Published: December 2004

Abstractβ′‐relaxation temperatures (Tβ′) provide a sensitive measure of the relative efficiencies of plasticizers in altering such properties of cellulose ester plastics as their impact strength, melt‐How, and modulus. Anomalies may occur, however, if the plasticizer‐compatibility limit in the polymer is surpassed. In addition, different correlations of Tβ′ and polymer properties are observed for liquid and solid plasticizers.
Influence of initiation mode on stability and control of a chain reaction
Authors: Chen H. T. , Chartier P. A. , Setthachayanon S. 
Published: December 2004

AbstractInitiation of chemical reactions by ultra‐violet light is characterized by essentially complete lack of temperature dependence and by physical separation of the source or initiating agent from the reaction medium. The advantage of these features for reactor stability and control are discussed in a theoretical study of the photo‐sensitized polymerization of styrene in a continuous stirred tank reactor and a comparison is made with the behavior of the thermally initiated reaction.
The influence of residual stresses and orientation on the properties of amorphous polymers
Authors: Thakkar B. S. , Broutman L. J. 
Published: December 2004

AbstractThe effect of cold rolling on impact strength of poly(vinyl chloride) (PVC) acrylonitrile‐butadiene‐styrene (ABS), and an alloy of ABS and polycarbonate (Cycoloy) was studied. The results were presented in terms of Izod impact strength and present oil thickness reduction. The residual stresses molecule orientation and modification of mechanical properties due cold rolling were measured. It was shown that the mechanism of toughness enhancement in PVC, ABS, and Cycoloy different than the one observed in rolled polycarbonates. In the case of a highly localized failure initiation event (a single eraxe), which appears to be present in polycarbonate, the influence of residual stresses, is great, whereas in rubber modified polymers having multiple erasing over a large volume, orientation is more important than residual stress. Hot rolling of poly(methyl methaerylate) holds promise for a continuous process to achieve orientation and toughness enhancement.
High stiffness polymers by die‐drawing
Authors: Gibson A. G. , Ward I. M. 
Published: December 2004

AbstractThe application of die‐drawing to the production of highly oriented polymers is considered, ft is shown that a variety of useful products can be obtained including not only rod and multifilament, but also tube and filled polymer. The investigations under discussion include the processing of several grades of linear polyethylene, polypropylene homopolymer and co‐polymer. In favorable cases, products of very high stiffness were obtained, reaching modulus values of 50 GPa for linear polyethylene and 20 GPa for polypropylene.
Molten poly(methyl methacrylate) under electron irradiation: Studies of depropagation and chain scission
Authors: Ficke H. H. , Merrill E. W. , Vasa N. K. 
Published: December 2004

AbstractThe degradation rates of free radical polymerized and syn‐diotactic poly(methyl methacrylate) (PMMA) under electron radiation were explored at temperatures ranging from 225 to 325°C and at electron dose rates from 10,000 rads/min to 100,000 rads/min. Scission of bonds between main‐chain atoms resulted in pairs of radical chain ends, of which some disportionated, thereby reducing polymer molecular weight without loss of volatile, while others proceeded to depropagate via the usual radical transfer, causing complete volatilization of the chain without significant change of molecular weight of the residual polymer. Electron irradiation at a dose rate of 100,000 rads/min produced a significant enhancement in the reaction, rate, and reduced the overall activation energy from 140 KJ/g‐mole observed for thermally induced depropagation to a value of 75 KJ/g‐mole observed during simultaneous irradiation and/thermal depropagation.
The effect of orientation on radiation‐induced degradation in high density polyethylene
Authors: Akay G. , Tincer T. 
Published: December 2004

AbstractThe oxidative degradation of cold drawn highly oriented high density polyethylene is studied by IR spectroscopy. Both gamma and ultraviolet radiation sources are used. It is found that under gamma radiation the oxidative degradation, as determined from carbonyl formation, is reduced very significantly but that the trans‐vinylene unsaturation in the polymer increases with draw ratio. Similar results are obtained for samples irradiated in vacuum or when the polymer is stabilized with a radical quencher. Annealing (with free‐ends) of the samples restores the rate of carbonyl formation over and above that of the undrawn polymer although restoration after annealing with fixed‐ends is not complete. There, is further increase in trans‐vinylene development after annealing. In stabilized samples, the effect of annealing on carbonyl and trans‐vinylene development appears to depend on draw ratio.Under ultra‐violet radiation, the oxidative degradation of drawn and unannealed samples is also reduced with increasing draw ratio. The same effect is observed in stabilized samples. Annealing, once again, restores the rate of oxidative degradation to that of the undrawn polymer. The main unsaturation product during ultraviolet irradiation is the vinyl end group and its development is suppressed with drawing. During ultraviolet irradiation of unannealed drawn samples, cracks, generally perpendicular to the draw direction (intrafibrillar cracks) appear on the sample and with further irradiation they penetrate into the sample. In the case of stabilized and unannealed drawn samples, cracks parallel to the draw direction (interfibrillar cracks) appear first and continued irradiation results in the appearance of intrafibrillar cracks. These observations may have significance in modelling the fibrous structures obtained by drawing semicrystalline polymers.
Polyurethane and polyblend sealants
Authors: Feldman D. 
Published: December 2004

AbstractA study has been carried out on the properties of a fast‐curing two‐part polyurethane sealant, and on its blends with other polymers, such as poly(vinyl acetate), poly(vinyl chloride) and poly(vinyl alcohol). Different substrates, such as Portland cement mortar, wood, and aluminum in three different thermal conditions were used. Tension tests by Universal Testing machine Model 1175 have been made, and stress‐strain curves have been devised and discussed. A two‐component fastcuring polyurethane sealant demonstrates good adhesivity for the supports mentioned. The elasticity of polyurethane sealants may improve even at low temperatures if mixing with other polymers.
Gel permeation chromatography: Automatic data acquisition and reduction in real‐time with a process computer
Authors: Meira G. R. , Johnson A. F. 
Published: December 2004

AbstractA real‐time computer system is described which minimizes the total analysis time in gel permeation chromatography by automatically acquiring the data, performing the necessary calculations and displaying the molecular weight distribution and molecular weight averages as soon as the polymer peak has eluted. The calculation method described here is valid for linear homopolymers only, and does not include corrections for instrumental peak broadening. The experimental results show good reproducibility and precision. On‐line changes of the constants and other parameters may be implemented by means of an auxiliary program which runs in parallel with the data analysis program. A system such as that described here is suitable for utilization as a measurement technique in process control applications. The programs are written in CORAL 66 for a Ferranti Argus 700 E computer.
The influence of non‐Newtonian flow on effective viscosity and channel efficiency in screw pumps
Authors: Booy M. L. 
Published: December 2004

AbstractA method is given for selecting the “effective viscosity” for isothermal flow of non‐Newtonian liquids in screw pumps or melt extruders. Effective viscosity is the Newtonian viscosity that would give the same screw‐pump performance with non‐Newtonian liquids at the same flow rate and speed. When effective viscosity is known, it can be inserted in performance equations for simple Newtonian flow. The analysis is restricted to shallow screw‐pump channels with large aspect ratios and to shear stress/shear rate curves with modest curvatures when shown in a double logarithmic plot. The shear stress/shear rate curve is replaced by a power‐law tangent to that curve in the domain of prevailing shear rates, but the analysis could be extended to more complex behavior. Curves are also included for calculating the efficiency of the screw‐pump channel, which can be used to estimate the energy dissipated in screw‐pumps. It is shown that efficiency decreases with decreasing power‐law exponent.
Deep channel operating characteristics of a single screw extruder: Finite element predictions and experimental results for isothermal non‐Newtonian flow
Authors: Choo K. P. , Hami M. L. , Pittman J. F. T. 
Published: December 2004

AbstractFinite element solutions are presented for developed, isothermal, power‐law flow in an extruder channel, based on a variational formulation in helical co‐ordinates. The success of the method in handling non‐Newtonian flow in a deep, highly‐curved channel is tested by comparison with experimental results. Operating characteristics were determired under virtually isothermal conditions for a screw with depth to diameter ratio 0.25 pumping an aqueous glucose solution containing high molecular weight hydroxyethyl cellulose. Shear stress and first normal stress differences of this solution were determined in a rheogoniometer. It was both highly shear‐thinning and elastic. Computed and experimental screw operating characteristics agree well, except near closed discharge, where effects due to viscous heating and elasticity are tentatively suggested.
Estimation of thermal conductivity of polyethylene resins
Authors: Kraybill Richard R. 
Published: December 2004

AbstractMethods of predicting and correlating thermal conductivity of polyethylene resins in solid and melt states are discussed herein. Dependence on crystallinity or density is estimated for the solid state by a form of Maxwell's equation for electrical conductivity. An equation is presented for predicting melt thermal conductivity based upon Bridgman's theory of energy transport and pressure‐volume‐temperature (PVT) data. The effect of pressure on melt thermal conductivity is calculated from the theory. The effect of pigmentation for near spherical particles up to approximately 2.5 volume percent is also correlated by a form of Maxwell's equation. Experimental thermal conductivities of unpigmented and pigmented polyethylene resins from 50 to 300°C are in good agreement with theoretical predictions and with literature data.
Filler effect on the recoil kinetics of drawn polystyrene
Authors: Nicolais L. , Apicella A. , Nicodemo L. 
Published: December 2004

AbstractRecovery experiments above Tg have been performed on glass bead and short glass fiber polystyrene composite sheets obtained from extrusion and subsequent hot drawing. A shift procedure has been applied to recoil data using the Williams‐Landel‐Ferry (WLF) equation with the same values of C1 and C2 used for unfilled polystyrene. The data reported show that an improvement of the dimensional stability of a drawn thermoplastic material can be obtained by adding very low volume percentage of fibers. Moreover, all the recoil data have been reduced to a unique generalized master curve which takes into account the draw ratio, the filler content, and geometry, using a fractional distance from equilibrium as a measure of the recovery. These results indicate that the presence of the filler does not affect the recoil kinetics of the polymeric matrix.
An anomaly in the necking behavior of polyethylene, part 4
Authors: Gedde U. W. , Terselius B. , Jansson J.‐F. 
Published: December 2004

AbstractIt is shown that the annealing of a high molecular weight, high density polyethylene at different temperatures ranging from 393.2 to 405.2 K influences the density of the material, the lamellar structure as studied by differential scanning calorimetry and transmission electron microscopy, and the necking and fracture behavior at constant uniaxial tensile loading in air at 313 K. In previous reports, a marked transition in the necking and fracture behavior of high density, high molecular weight polyethylene under constant uniaxial tensile loading has been reported. The nominal stress and the maximum strain rate of this transition show minima for polyethylenes annealed at temperatures of about 401 K. By combining these data with data for the lamellar structure a hypothesis that explains the necking/fracture behavior is set up. The heat treatment at temperatures from 393.2 to 403.2 K of the original non‐equilibrium lamellar structure causes a molecular fractionation preferentially of low molecular weight and branched material. These segregated parts may then act as fracture initiators and thus lower the resistance towards fracture. Other structural effects such as those proposed by McCready and co‐workers may also be of importance. The fracture curves at nominal stresses below transition of the materials annealed at 396.7 and 401.2 K for 24 h are shifted to shorter times in comparison with that of the non‐annealed material and this can also be explained by molecular fractionation. The time to necking at 14 MPa nominal stress seems to be related to the lamellar thickness of the samples.
Compatibility and physical properties of a new polyester blend
Authors: Slagowski E. L. , Chang E. P. , Tkacik J. J. 
Published: December 2004

AbstractThe compatible nature of a new polyester blend, polybutylene‐terephthalate (PBT) and a copolyester of bisphenol‐A‐neopentyl glycol‐terephthalate (CP‐350), has been inferred from the single Tg by DSC and dynamic mechanical studies. Compatibility is further confirmed from the progressive melting point depression of PBT, and the increasingly coarse and open spherulitic morphology of the blends as the weight percent of CP‐350 increases. At and above 40 weight percent of CP‐350, crystallization of PBT is impeded by the presence of high concentrations of CP‐350 which results in a low degree of PBT crystallinity (0‐8 percent) in such blends. The melt viscosity as a function of blend composition shows a good fit to the Hayashida model.
Sorption and diffusion of alcohols in amorphous polymers
Authors: Sfirakis Alexander , Rogers Charles E. 
Published: December 2004

AbstractThe effects of polymer composition and penetrant molecular size on the solubility and diffusivity of alcohol vapors in a series of well characterized isoprene‐methyl methacrylate copolymers and their corresponding homopolymers has been investigated at room temperature. The rate of sorption behavior changes progressively from Fickian to non‐Fickian, to Case II to “Super Case II” transport with increasing methyl methacrylate (MMA) content in the polymers. The equilibrium solubility of the alcohols increases linearly with increasing penetrant molecular size for polymers which are above their glass transition temperature and decreases for polymers which are below their Tg. The solubility also initially increases as an approximately linear function of MMA content in the copolymers. At about 55 mole percent MMA, the sorbed concentration either levels off or passes through a maximum depending on the size of the penetrant. The apparent “diffusion coefficients” (D) decrease with increasing molecular volume of the penetrants. An exponential dependence was found between these two variables for PMMA. These “diffusion coefficients” also decrease exponentially with increasing MMA content in these polymers. However, at 55 mole percent MMA the copolymer undergoes a rubber to glass transition at the temperature of the experiments. On this basis, it is suggested that the hindered chain segmental motion contributes to the sorption process in addition to strictly thermodynamic considerations. Free volume theory can be used to explain the mechanism of diffusion through the rubbery polymers while the “hole” theory can be applied to explain the transport of the penetrants through the glassy polymers.
Structural changes in the surface layer of plastic as a result of sliding friction in a metal‐thermoplastic system
Authors: Krzemiński Jerzy L. , Wiechowicz‐Kowalska Ewa 
Published: December 2004

AbstractStudies on structural changes in the surface layer of plastics during internal sliding friction (friction upon seizing) of metalthermoplastic systems have been carried out. These structural changes were carried out by means of polarized light microscopy, density measurements, X‐ray diffraction and IR absorption spectroscopy (ATR). They were carried out for high density polyethylene (HDPE), polypropylene (PP) and nylon 6 (PA6). As a result it was found that the formation of completely different structures was caused by internal sliding friction.
Viscoelastic behavior of suspensions of particles in polymer solutions
Authors: Umeya Kaoru , Otsubo Yasufumi 
Published: December 2004

AbstractSuspensions, consisting of glass beads about 1 μm in diameter and a 20 wt percent polystyrene solution in diethyl phthalate, were prepared at concentrations up to 13 vol percent. The viscoelastic properties were measured by means of a conventional dynamic method and by the raised cosine pulse method. The relaxation intensity and relaxation times of suspensions increased with increasing particle concentration. However, at concentrations > 13 vol percent, the stress against the raised cosine pulse strain did not approach zero. It was found that concentrated suspensions were complicated by a combination of viscous, elastic, and plastic effects. The experimental results have been qualitatively explained on the base of the network structure of particles.