bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fiber‐forming properties of polymer mixture melts and properties of fibers on their basis
Authors: Tsebrenko M. V. , Rezanova N. M. , Tsebrenko I. A. 
Published: April 2004

AbstractThe fiber‐forming properties of the following polymer mixture melts have been investigated: polypropylene‐copolyamide (PP/CPA), polyoxymethylene‐copolyamide (POM/CPA), POM‐copolymer of ethylene and vinyl acetate (POM/EVAC), PP/EVAC, EVAC/CPA, and polypropylene‐polyvinylalcohol (PP/PVA). The capability of the polymer mixture melts to fiber‐form was estimated by degree of the polymer melt longitudinal deformation. It has been determined that the fiber‐forming properties of polymer mixture melts can be regulated by changing the chemical nature of the mixture components, structure‐formation processes and by introducing various additives of polymer and non‐polymer nature into binary mixture. The mechanism of action of additives is connected with changing microrheology processes during mixture melt flowing under the influence of the specific interaction between polymer macromolecules and additives at the interphase. The complex threads from PP, POM or EVAC microfibers have been produced and the features of their structure and properties have been investigated. There are the following distinctive properties of the complex threads consisting of microfibers: high strength and initial modulus, high elasticity, exclusive softness, pleasant feel, coupling, capaciousness, and wool‐likeness without special textural procedures, high sorption of moisture, dyes and other substances.
Physical and microstructural effects of heat setting in polyester films
Authors: Greener J. , Tsou A. H. , Blanton T. N. 
Published: April 2004

AbstractThe effects of a controlled heat‐setting treatment on the properties and microstructure of biaxially stretched poly(ethylene terephthalate) (PET) and poly(ethylene‐2,6‐naphthalene dicarboxylate) (PEN) films are described. Substantial changes in crystalline fraction, crystallite size, glass transition temperature and significant enhancement in dimensional stability are observed for both film types upon increase in heat‐set temperature. A distinct melting peak in the vicinity of the heatset temperature, observed in differential scanning calorimetry thermograms for both materials, is shown to be an effective marker of the heat‐setting process underlying the dual nature of the morphology of the heat‐treated films. We also observe that the PET films undergo significant molecular realignment on heat setting, while the orientation of the PEN films is only weakly modified by the heat‐set conditions. A morphological transition is detected for both films at high heat‐set temperature (THS*) near the onset of the primary melting range, marking a qualitative change in the physical response of the biaxially oriented films; Measurable drop in planar orientation and glass transition temperature, and a sharp rise in crystallite size are noted for films heat‐treated above THS*. The morphological models of previous workers (Schultz et al. and Fischer and Fakirov), invoking the idea of fibrillar‐to‐lamellar transformation, are used to explain some of our observations.
Orientation and crystallization in poly(ethylene terephthalate) during drawing at high temperatures and strain rates
Authors: Salem D. R. 
Published: April 2004

AbstractWe review some recent research developments on structure development during drawing of poly(ethylene terephthalate) film, and we report a study of constant‐load drawing of amorphous PET film at temperatures of 120°C and 132°C, including the effects of redrawing high‐temperature drawn film at lower temperature. To permit constant‐load drawing at high temperature without inducing crystallization in the undrawn specimen, a drawing instrument was built that permits very rapid heating of the sample, and its operation is described. The initial stage of drawing at high temperatures is characterized by polymer flow where, owing to high rates of molecular relaxation, neither molecular orientation nor crystallization occurs. Strain‐rate increases sharply in the course of the deformation, reducing the time available for relaxation, and the chains start to orient at a draw ratio that depends on temperature. Orientation rapidly reaches a saturation level, which is lower at the higher draw temperature. Crystallization onset seems to lag only slightly behind orientation onset because the critical orientation for inducing crystallization is very low at these temperatures. It appears that there is time for crystallization to proceed to pseudo‐equilibrium values corresponding to a particular orientation level, which differs from previous results obtained from constant‐force drawing at lower temperatures, and possible reasons for this are discussed. In two‐stage drawing, where film drawn at 132°C was redrawn along the same axis at 100°C, high draw ratios were obtained despite the high strain rates, and the levels of noncrystalline orientation and crystallinity were similar to the levels expected from single stage drawing at 100°C.
Influence of interchange reactions on the crystallization and melting behavior of nylon 6,6 blended with other nylons
Authors: Walia P. S. , Gupta R. K. , Kiang C. T. 
Published: April 2004

AbstractThe thermal behavior of blends of nylon 6,6, with an amorphous polyamide, Trogamid‐T, and a semicrystalline polyamide, nylon 6,12, was studied. The blends were prepared both by solution blending and by melt blending, using a Maxwell extruder and a twin screw extruder. The concentration of the blends ranged from 75% to 95% by weight of nylon 6,6. Annealing the blend samples in the molten state in a differential scanning calorimeter (DSC) produced changes in the melting and crystallization behavior. This was attributed to transamidation reactions occurring between the blend components, leading to the formation of in‐situ block copolymers. The length of the blocks decreased with annealing time, as suggested by reduced melting (Tm) and crystallization temperatures (Tc) and heat of fusion values. The changes in thermal behavior were dependent on the blending method, additive concentration, presence or absence of a catalyst, melt annealing time, and the extent of melt mixing. The extent of reaction, measured by the depression in equilibrium melting temperature, was linear with respect to the annealing time. The Trogamid‐T containing blends appeared to be “nearly miscible” while those with nylon 6,12 were initially immiscible. The glass transition temperature (Tg) vs. the composition curve of the nylon 6,6/Trogamid‐T blends showed a positive deviation from linear additivity, with the single Tg decreasing as a function of annealing time in the melt.
Polymer toughness and impact resistance
Authors: Perkins William G. 
Published: April 2004

AbstractThis report is a review of the factors that influence the impact resistance of high polymers, with an emphasis on crystalline polymers. The phenomenology of polymeric fracture is examined, including brittle and ductile failure, and the ductile‐brittle transition temperature (DBTT). An in‐depth discussion of the effects of crystalline morphology follows, with special attention given to the influence of spherulite size, fillers, processing conditions, transitions/relaxations, and multilayer coextrusion. Next, rubber phase addition is considered, including mechanisms, morphology, rubber type and particle size, and test conditions. Finally, common impact test methods are surveyed, including pendulum, falling weight, tensile impact, and tensile elongation tests.
An investigation of shear‐induced mixing in the PSAN/PMMA blend
Authors: Papathanasiou T. D. , Higgins J. S. , Soontaranun W. 
Published: April 2004

AbstractWe investigate experimentally the effect of steady‐state simple shear flow on the miscibility of a 60–40 poly(styrene‐co‐acrylonitrile) with poly(methyl‐methacrylate) (PSAN/PMMA) blend. Thin disks, containing 60% w/w PSAN, are thermoformed from blend pellets made by mixing PSAN and PMMA granules in a co‐rotating, fully‐intermeshing twin‐screw extruder. These disks are sheared at constant shear rate in a cone‐and‐plate mechanical spectrometer at fixed temperatures within the quiescent two‐phase region. At the end of each shearing experiment the sample is quenched and its morphology investigated first visually for optical transparency (cloudiness being an indicator of a phase‐separated blend) and then using transmission electron microscopy (TEM). Results indicate that upon imposition of a shear rate as low as 0.1s−1 the 60–40 blend remains miscible even at temperatures up to 7K within the (quiescent) two‐phase region. These observations are in agreement with theoretical predictions of the phase diagram under shear, based on the concept of a modified Gibbs free energy of mixing. The TEM results concerning the morphology of the phase‐separated blends are also discussed.
Properties of poly(ethylene terephthalate)/poly(ethylene naphthalate) blends
Authors: Rwei Syang‐Peng 
Published: April 2004

AbstractBlends composed of poly(ethylene terephthalate) (PET) as the majority component and poly(ethylene naphthalate)(PEN) as the minority component were melt‐mixed in a single screw extruder at various PET/PEN compound ratios. Tensile and flexural test results reveal a good PET/PEN composition dependence, indicating that the compatibility of the blends is effective in a macrodomain. In thermal tests, single transitions for Tg, Tm and Tc (crystallization temperature), respectively, are observed from DSC as well as single Tg from DMA except for 50/50 blends. These results suggests that the compatibility is sufficient down to the submicron level. Moreover, isothermal DSC tests along with Avrami analysis indicate that PET's crystallization is significantly retarded when blended with PEN. Results in this study demonstrate that PEN is a highly promising additive to improve PET's spinnability at high speeds.
Polypyrrole conductive polymer characteristics as an optical display device
Authors: Al‐Attar H. A. , Al‐Kabbi A. S. , Faris F. A. 
Published: April 2004

AbstractThe redox dynamic of electrochemically prepared thin films of polypyrrole is studied. A semi‐empirical formula to explain the redox behavior is formulated and it seems applicable to the reduction dynamic. The redox dynamic is dominated by a diffusion process, depending on the relation between the film thickness and the rise time (t1/2) of the reduction process. The diffusion coefficient, D, was measured to be 2 × 10−9 cm2/sec for perchloride (ClO4−) anion dopant and 1.1 × 10−9 cm2/sec for para‐toluenesulfonate (PTS−) anion dopant. The polypyrrole films exhibited a color change during the oxidation and reduction processes. The electrooptical properties of these films are studied.
Convective and radiant (IR) curing of bulk and waterborne epoxy coatings as thin layers. Part II: Infrared curing
Authors: Blanc D. , Laurent P. , Andrieu J. , Gerard J. F. 
Published: April 2004

AbstractIn the first part of this paper, a method for studying the curing of 100‐μm‐thick epoxy‐based layers on steel substrates was described. In this second part, we extend our study to radiative (infrared) heating conditions. A simple waterborne epoxy reactive system based on a diglycidylether of bisphenol‐A prepolymer and a polyether triamine was used. The chemical kinetics during infrared heating were studied with the reaction kinetics recorded during convective heating. A second order autocatalytic model described the data. The curing mode had no significant influence on the heating kinetics but the heating rate had a significant influence on the curing kinetics. Higher heating rates can be achieved by infrared heating conditions compared with convective heating. The gelation phenomenon was changed for infrared conditions. Microdielectrometry can be used to record in situ the extent of reaction of the epoxy reactive system for thin layers during radiant heating.
Simple shear plastic deformation behavior of polycarbonate plate due to the equal channel angular extrusion process. I: Finite element methods modeling
Authors: Sue Hung‐Jue , Dilan Hector , Li Chris K.‐Y. 
Published: April 2004

AbstractSimple shear plastic deformation behavior of polycarbonate (PC) plates due to the novel equal channel angular extrusion (ECAE) process is modeled using a commercial finite element methods (FEM) package. The true stress and true strain contour plots as well as the strain rate variation across the PC plate during the ECAE process are analyzed. The FEM results correlate well with the experimental findings. The present study indicates that the novel ECAE process is effective in producing a high degree of simple shear plastic deformation across the extruded polycarbonate plate. The high degree of plastic deformation due to ECAE induces a high level of nearly uniform molecular orientation across the extruded PC plate. As a result, significantly improved physical and mechanical properties in PC are expected. The simple shear plastic deformation behavior of PC plate, as a function of extrusion rate and temperature, is investigated. The significance of the ECAE process for fabricating polymer parts is also discussed.
Critical assessment of methods for evaluatingJICfor a medical grade ultra high molecular weight polyethylene
Authors: Pascaud R. S. , Evans W. T. , McCullagh P. J. J. , Fitzpatrick D. 
Published: April 2004

AbstractVarious methods for the evaluation of the critical J‐integralJICbased on the standard ASTM E813–89 are analyzed by conducting investigations on a ductile medical grade ultra high molecular weight polyethylene (UHMW‐PE) at room temperature. Differences inJICreaching almost 50% were recorded between the methods investigated. The controversy surrounding the construction of the crack blunting line is discussed in terms of the stretch zone width together with the size requirements of ASTM E813–89. The findings of this investigation suggest that an R‐curve construction based on mid‐thickness crack growth and ultimate tensile strength (UTS) combined with a blunting line of slope m = 2 and modified exclusion lines provides consistent and conservativeJICvalues. Using this technique, a near plane strain value, smaller than previously published data, of 66.5 kJ/m2was obtained at 23°C.
Measurement of internal stresses in coatings using time resolved fluorescence
Authors: Shiga Tohru , Narita Takeshi , Tachi Kazuyuki , Okada Akane , Takahashi Hideroh , Kurauchi Toshio 
Published: April 2004

AbstractThis paper describes a new nondestructive technique for detecting internal stresses in coatings using time resolved fluorescence. The measurement principle is based upon an experimental result that the decay time of fluorescence from poly(3‐octylthiophene), P3OT, dispersed in uniaxially‐stretched polymer films decreases with increasing tensile stress acting on the films. Internal stresses in the clear coat and in the base coat of a multilayer structure, which was composed of electrodeposited coat, surface coat, base coat, and clear coat, were estimated from the decay time of fluorescence from P3OT in both coats. The order of internal stresses in the clear coat and base coat of the multilayer system was 1 MPa. When the coatings were piled up, the internal stress decreased as the distance from a metal substrate was increased. It was found that moisture and temperature influenced internal stresses in the clear coat rather than in the base coat. Internal stress in the clear coat, which was one layer coated on a metal substrate, was measured by the traditional bimetallic method or by the time resolved fluorescence technique. Comparing both methods, it was concluded that the time resolved fluorescence technique gave reliable values for internal stresses in coatings.
Physical aging in polymers and polymer composites: An analysis and method for time‐aging time superposition
Authors: Bradshaw R. D. , Brinson L. C. 
Published: April 2004

AbstractThe ability to include the effects of physical aging is critical to the design of engineering structures involving advanced polymers and polymer composites. Physical aging, a phenomenon caused by material evolution towards thermodynamic equilibrium, is typically described by reducing short‐term momentary compliance curves, via time‐aging time superposition, into a predictive reference curve and shift factor function. This paper presents an analytic method based on error minimization for this data reduction task, and introduces the concept of a total reference curve as an alternative to choosing a single momentary curve for the reference. Four different predictive approaches are considered to determine the efficacy of the total reference concept, and whether vertical shifting is beneficial. For most of the materials studied, the total reference using horizontal shifting alone is the recommended method; in the few remaining cases, the total reference procedure with both horizontal and vertical shifting resulted in the best outcome.
Effect of processing history on the morphology and properties of polypropylene/thermotropic liquid crystalline polymer blends
Authors: Machiels A. G. C. , Denys K. F. J. , Van Dam J. , De Boer A. Posthuma 
Published: April 2004

AbstractPreparation, morphology, and mechanical properties were studied of blends of a thermotropic liquid crystalline polymer (TLCP) with two different grades of polypropylene, one with and one without overlap in processing temperatures, using two different blending methods. The highly viscous grade (PP‐1) was of sufficient thermal stability to be blended with the TLCP (Vectra A950) in a single‐screw extruder with an Egan mixing section on the screw. The low viscous grade (PP‐2) could not be processed at the same temperature as the TLCP because of degradation. Its blends were, therefore, prepared by a special coextrusion technique, i.e. feeding the two components from two separate extruders to a Ross static mixer. In both methods drawing of the extrudate is necessary to obtain satisfactory mechanical properties. The PP‐1/TLCP blends had to be extruded twice in order to obtain proper mixing. The morphology of these blends ranges from a pronounced skin‐core morphology at low extrudate draw ratio (DR = 3) to a high‐aspect ratio fiber/matrix morphology at high draw ratio (DR = 15). The morphology of the PP‐2/TLCP blends was always a high‐aspect ratio fiber/matrix morphology even at low draw ratios. The TLCP fibers were generated in this coextrusion process under conditions where the viscosity of the dispersed phase was higher than the viscosity of the matrix. Breakup experiments demonstrate that fibers of a thickness of approximately 1 μm disintegrate into droplets within a few seconds at temperatures above the melting point of the TLCP. This is probably the cause of the skin‐core morphology obtained with single‐screw extrusion. Tensile modulus and strength of all blends increase with extrudate draw ratio. The deformation of the TLCP phase in the drawn blends is less than affine, probably because of slip between the phases. The moduli of the PP‐1/TLCP blends as a function of the draw ratio can be described well by a modified Halpin‐Tsai equation taking into account both changes in aspect ratio and molecular orientation of the TLCP fibers. The level of reinforcement in the PP‐2/TLCP blends is lower than expected, probably because of the low temperature of drawing. This demonstrates a limitation of the coextrusion process: blending at temperatures that are too low reduces mechanical properties.
Tensile properties and stress relaxation of polypropylene at elevated temperatures
Authors: Ariyama Takashi , Mori Yasunari , Kaneko Kenji 
Published: April 2004

AbstractSamples of isotactic polypropylene(PP) were subjected to stress‐relaxation experiments after simple tensile tests at four strain rates and at different levels of temperature. The relaxation moduli were determined in the range of temperature between 20 and 80°C with a relaxation period of 1200s duration. The activation energy value of the shift factor was determined using the time‐temperature superposition principle. The calculated stress‐strain curves and stress‐relaxation curves were obtained from constitutive equations based on an overstress theory in which the temperature dependence of viscosity and the activation energy were considered. The temperature dependence of viscosity was amenable to an Arrhenius type equation. The quasi‐equilibrium stress depends on both the current strain and the temperature. The calculated results were obtained by the proposed constitutive equation and compared with the data. The proposed constitutive equations based on the overstress model explain well the viscoelastic‐plastic behavior of PP samples.
Crystallization in blends of poly(ethylene terephthalate) and poly(butylene terephthalate)
Authors: Yu Yishan , Choi Kyung‐Ju 
Published: April 2004

AbstractBlends composed of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) were melt‐mixed in a Brabender cam mixer at different mixing speeds. The glass transition (Tg) and the crystallization behavior of the blends from glassy state were studied using DSC. It was found that although the blends had the same composition and exhibited the similar Tg, their properties of crystallization could be different; some exhibited a single crystallization peak and some exhibited multiple crystallization peaks depending upon experimental conditions. Results indicated that the behavior of crystallization from glassy state were influenced by entanglement and transesterification of chains. The crystallization time values were obtained over a wide range of crystallization temperature. From curve fitting, the crystallization time values and the temperature, at which the crystallization rate reaches the maximum, were found.
Electrical conductivity of poly(vinyl chloride) plastisol–short carbon fiber composite
Authors: Guoquan Wang , Peng Zeng 
Published: April 2004

AbstractIn this work, short carbon fibers were blended with poly(vinyl chloride) (PVC) plastisol forming a conductive network of the fibers in the composite. The effects of concentration and initial length of the carbon fibers on the conductivity of the network were studied. For an initial fiber length of 3 mm (L/D = 428), the volume resistivity of the network decreased rapidly from 4.3 × 105 to 5.1 × 100 Ω‐m for a change in the fiber concentration of 0.5 to 1.0 phr. The samples prepared by the plastisol method also showed excellent antistatic properties at very low fiber concentration (e.g. 1.0 phr), better than the samples that were prepared by mill mixing. Observation of the morphology showed that the short carbon fibers maintained their initial length in the PVC plastisol‐carbon fiber composite, without obvious breakage. This is why a conductive network in the plastisol‐carbon fiber composite can be formed at very low fiber concentrations.
Viscosity measurement of polycarbonate by using a penetration viscometer
Authors: Yang Fuqian 
Published: April 2004

AbstractUsing a penetration viscometer, the viscosity of polycarbonate was measured in a temperature range of 419 to 443 K and under punching stresses between 0.25 to 20 MPa. The flow behavior under these conditions is Newtonian and the activation enthalpy is 413 kJ/mole.