bluuebunny/crossref_metadata_2025_split huggingface dataset:
Essential work of fracture (EWF) analysis for short glass fiber reinforced and rubber toughened nylon‐6
Authors: Ching Emma C. Y. , Li Robert K. Y. , Tjong Sie Chin , Mai Yiu‐Wing 
Published: April 2004

AbstractThe effect of fiber content on the fracture toughness of short glass fiber reinforced and rubber toughened nylon‐6 has been investigated using the essential work of fracture (EWF) analysis under both quasi‐static and impact rates of loading. Under quasi‐static loading rate, matrix plastic deformation played a major role. Addition of 10 wt% of short glass fibers into a rubber toughened nylon‐6 matrix improved the fracture toughness substantially. This is due to the synergistic effect that comes from matrix yielding and fiber related energy absorption such as fiber debonding, fiber pull‐out and fiber fracture. With further increasing the glass fiber content, up to 20 and 30 wt%, even though plastic deformation could still take place on the fracture surfaces, the depth of the fracture process zones was much smaller when compared with the system with 10 wt% of glass fibers. The reduction in fracture process zone caused the reduction in fracture toughness. Under impact loading rate, the unreinforced blend still fractured in a ductile manner with gross yielding in the inner fracture process zone and the outer plastic zone. The unrein‐forced blend therefore possesseed higher fracture toughness. For the fiber reinforced blends, the matrix fractured in brittle manner and so fracture toughness of the reinforced blends decreased dramatically. The impact fracture toughness increased slightly after incorporation of a higher weight percentage of glass fibers.
A study on the use of phenoxy resins as compatibilizers of polyamide 6 (PA6) and polybutylene terephthalate (PBT)
Authors: Dharaiya Dhawal , Jana Sadhan C. , Shafi Asjad 
Published: April 2004

AbstractIn this study we investigated the potential of phenoxy resins as compatibilizers in the blending of two high‐volume engineering thermoplastics—polyamide 6 (PA6) and polybutylene terephthalate (PBT), in an effort to establish the usefulness of blending as a method of recycling of mixed plastic wastes. It was found that phenoxy resins formed miscible blends with PBT, formed grafted copolymers with PBT through ester exchange reactions, and—though formed immiscible blends with PA6—produced energetic interactions in the form of hydrogen bonding with PA6. The ternary blend systems of 70 parts PA6, 30 parts PBT, and respectively 5, 10, and 30 parts phenoxy resins, all by weight, revealed at two‐phase nature—PA6 as the continuous phase and miscible blends of PBT and phenoxy resins as the dispersed phase—and were found to be stable to phase coarsening by annealing with mechanical properties at least as good as those of the component polymers.
Simulation of injection‐compression molding for optical media
Authors: Fan Bingfeng , Kazmer David O. , Theriault Richard P. , Poslinski Andrew J. 
Published: April 2004

AbstractA numerical simulation of a coining type of injection‐compression molding is developed. A hybrid finite element/finite difference method is employed to model the temperature and pressure fields of the process using a non‐isothermal compressible flow model. Simulation results for CD‐R molding with respect to injection pressure and mold displacement are compared with experimental observations using an optical grade of polycarbonate. The simulation shows similar trends as experimental observations on the dependence of various processing parameters such as melt temperature, mold temperature, and packing pressure. However, the mold displacement measurement does not show the effect of punch delay time as does the simulation, and needs further investigation.
Influence of intermolecular entanglements on crystallization behavior of ultra‐high molar mass polyethylene
Authors: Fan Zhongyong , Wang Yiren , Bu Haishan 
Published: April 2004

AbstractUltra high molar mass polyethylene (UHPE) was melted at 160°C for various times or at various temperatures for 5 min and then the crystallization of the UHPE was carried out on cooling. It was found that the crystallization temperature decreased as the heating time or heating temperature increased. During the melting process, thermal motion of the chains leads to a change of chain conformation from parallel‐extended chains to interpenetrated random coils, accompanied by the occurrence of entanglements. As a result, the crystallization temperature shifts to lower temperature. On the other hand, samples of UHPE with less entanglement were prepared from a dilute solution by a freeze‐drying procedure. It was observed that the crystallization temperature of the freeze‐dried samples from the melt depressed with dereasing solution concentration. UHPE would produce small crystals in the freezing process, thus leading to a reduction in melting point, and a sifting of crystallization temperature to lower temperature. Based on the melting point, the average volume of small crystals was estimated; it is even smaller than that of one single chain of the UHPE.
In‐situ microfiber reinforced composite based on PET and PE via slit die extrusion and hot stretching: Influences of hot stretching ratio on morphology and tensile properties at a fixed composition
Authors: Li Zhong‐Ming , Yang Ming‐Bo , Xie Bang‐Hu , Feng Jian‐Min , Huang Rui 
Published: April 2004

AbstractAn in‐situ microfiber‐reinforced composite (MRC) based on polyethylene (terephthalate) (PET) and polyethylene (PE) was prepared by slit die extrusion followed by hot stretching. Test specimens were prepared by injection molding at the processing temperature of the PE matrix. At this temperature, far below the melting temperature of PET, the PET phase is solid and able to keep its shape during processing. The morphological characteristics of the dispersed PET phase in the blend, at a fixed weight composition (15:85) of PET and HDPE, were dependent upon the hot stretching ratio. When the hot stretching ratio was increased from 1 (no stretching) to 47.62, the PET particles changed from spheres and ellipsoids to rodlike particles and finally to microfibers. The maximum and average diameters of the PET particles decreased steadily, while the minimum fiber diameter remained constant. The tensile modulus and strength of PET/PE blends were significantly enhanced with increasing hot stretching ratio, indicating that the microfibers have good reinforcement. Ultimate elongation decreased with increasing hot stretching ratio and there was a critical hot stretching ratio above which a ductile‐brittle transition occurred.
Multiple melting behavior of syndiotactic 1,2‐polybutadiene
Authors: Sasaki Takashi , Sunago Hayato , Hoshikawa Takuya 
Published: April 2004

AbstractA differential scanning calorimetry study on a typical thermoplastic elastomer, syndiotactic 1,2‐polybutadiene, crystallized from the melt is presented. Endotherms observed upon heating for samples isothermally crystallized from the melt exhibited a double melting profile. The peak temperature of the endotherm that appeared at a lower temperature (low endotherm) showed stronger dependence on the heating rate than that appearing at a higher temperature (high endotherm). The results of partial melting experiments demonstrated that the high endotherm is not affected at all by melting of only the crystals responsible for the low endotherm, indicating that the double melting behavior is due to the existence of two crystalline species with different stabilities. Structures and melting mechanisms of these two different crystalline species are discussed on the basis of the observed difference in superheating behaviors upon melting. The results on overall rate of isothermal crystallization are also presented.
Prediction of water solubility in nylon melts based on flory‐huggins theory
Authors: Schaffer M. A. , Mcauley K. B. , Cunningham M. F. , Marchildon E. K. 
Published: April 2004

AbstractThe solubility of water in molten aliphatic polyamides (nylons) of high degrees of polymerization at conditions of subatmospheric water partial pressure and high temperature (225 to 300°C) has been modeled. A simple, semi‐empirical model based on Flory‐Huggins theory was fit to the available literature data for nylons 6, 66, 610 and 11 and to new experimental data for nylon 612. The model contains only two fitted parameters, and is able to adequately describe the available data for the effects of temperature and nylon type on the water concentration in the melt at various water partial pressures.
Comparison between five experimental methods to evaluate interfacial tension between molten polymers
Authors: Demarquette Nicole R. , De Souza Adriana Martinelli Catelli , Palmer Guillermo , Macaubas Paulo Henrique Pierin 
Published: April 2004

AbstractIn this work, an experimental comparison between five different techniques to measure interfacial tension between molten polymers is presented. The five techniques include two equilibrium methods: the pendant drop (PD) and the sessile drop (SD); two dynamic methods: the breaking thread (BT) and imbedded fiber retraction (IF); and a rheological method based on linear viscoelastic measurements of the blend (RM). The polymer pairs studied were polystyrene/polypropylene (PS/PP); and PP/high density polyethylene (PP/HDPE). It was possible to determine the interfacial tension between PP/PS with all the methods tested and the results corroborated within 20%. However, the interfacial tension between PP and HDPE could be evaluated only using rheological methods because of a too‐small difference of index of refraction between both polymers. The experimental precision increased in the following order: RM < SD < BT < IF < PD. The rheological method had the advantage of being simpler and faster than dynamic and equilibrium methods. However, when using the rheological method, care should be taken because the results obtained may depend upon the concentration of the blend used for the measurements. It was observed that the pendant drop and breaking thread methods cannot be used for polymers with high viscosity (above 5 × 105 Pa.s).
Microstructure analysis of high performance fibers in compression
Authors: Huh Wansoo , Kumar Satish , Wade Adams W. 
Published: April 2004

AbstractIn order to understand the nature of kink band formation in high performance fibers, the compression behavior of pitch and PAN‐based carbon fibers (P75S, T‐50, T‐300, and GY‐70), and of polymeric fibers (DuPont Kevlar; PBZT; and PBO) was measured using a micro‐scale compression apparatus in an optical microscope. With increasing compressive strain, kink band formation was observed and the number of kink bands per unit length (referred to as kink band density) was determined. By extrapolating to zero kink band density, the critical compressive strain for rigid‐rod polymeric fibers was obtained and compared to that of the carbon fiber. Using the Euler buckling equation, a fundamental dimension of the buckling element for the compression of PBO and PBZT fibers was calculated to be a 0.42–0.57 µm diameter fibril, and not the smaller diameter microfibrils.
The influence of power‐law rheology on flow distribution in coathanger manifolds
Authors: Reid J. D. , Campanella O. H. , Corvalan C. M. , Okos M. R. 
Published: April 2004

AbstractCoathanger dies are effective in delivering uniform flow if a polymer melt; however, when the fluid flow index varies from the design values, the flow is not uniform. Although mechanisms such as die lip adjustments have been effective tools for adjusting flow profiles, the issue of a variable flow index has not been fully addressed at the design stage. An analytical solution, based on the assumptions present in the 1‐D design equation, has been developed for the flow distribution in a coathanger manifold. This solution determines the flow distribution for a power‐law fluid with a flow index n* in a manifold designed for a separate flow index n*. From this solution, a uniformity index and a critical design angle are defined. The critical design angle is the angle at which the local derivative of the uniformity index with respect to n* approaches a maximum (for n* < n) or a minimum (for n* > n) as a function of the design angle. The critical design angle is independent of n and is presented as a function of the manifold aspect ratio.
All‐optical switching modulation in poly(vinyl carbazole)—based azobenzene blends
Authors: Wu Shuizhu , Yao Shenglan , She Weilong , Yan Kun , Zhao Jianqing 
Published: April 2004

AbstractWe report on the all‐optical switching polymer blends based on photoconductive poly(vinyl carbazole) (PVK) and azobenzene dyes. The optical switching effects of the blends were measured by using a 514 nm pump beam and a 632.8 nm probe beam. The blends' photoinduced reversible and repeatable change in the transmittance of the probe beam is attributed to the photoinduced anisotropy of the azobenzene dyes. The influencing factors of the optical switching effect, such as the modulation frequency and pump beam intensity, were studied experimentally.
Deformation behavior of an epoxy resin subject to multiaxial loadings. Part II: Constitutive modeling and predictions
Authors: Xia Zihui , Hu Yafei , Ellyin Fernand 
Published: April 2004

AbstractBased on the experimental data presented in Part I, a nonlinear viscoelastic constitutive model, in differential form, is presented here. A distinctive feature of this model is the inclusion of a criterion to delineate loading and unloading in multiaxial stress states, and different moduli for loading and unloading behaviors. In addition, the model contains only five material constants and one modulus function, which can be calibrated in accordance with a well‐defined procedure. A comparison with the experimental data shows that the current differential model is capable of predicting the nonlinear viscoelastic behavior of the epoxy polymer qualitatively and quantitatively, including both the loading and unloading behavior. The predictions of an integral form of constitutive model are also included for comparative purposes.
Scratch visibility of polymers measured using optical imaging
Authors: Rangarajan P. , Sinha M. , Watkins V. , Harding K. , Sparks J. 
Published: April 2004

AbstractAs plastics replace metal in automotive and other applications, aesthetic concerns due to scratch or mar damage replace rust and corrosion issues. This paper presents a novel method to quantify the visibility of a scratch on a polymer surface. It is shown that the most important factor is the optical contrast between the damaged area and its surroundings. The critical optical parameters that affect a viewer's perception of scratch severity are identified as the size and roughness of the scratch, and the color and gloss of the surroundings. An optical imaging system and method for measuring the optical parameters that result in this contrast is described.
Functionalization of high density polyethylene with maleic anhydride in the melt state through ultrasonic initiation
Authors: Zhang Yuncan , Li Huilin 
Published: April 2004

AbstractGrafting of maleic anhydride (MAH) onto high density polyethylene (HDPE) performed in the melt state through ultrasonic initiation by a laboratory‐scale ultrasonic extrusion reactor was studied in this paper. The effect of sonic intesity on the amount of grafted MAH, viscosity‐average molecular weight and melt flow index of the grafted product was investigated. The results show that the ultrasonic waves can obviously decrease the molecular weight of the grafted product and cause the increase of the amount of grated MAH, implying that the grafting reaction consists of the chain scission and the grafting reaction of the produced macroradicals with MAH. The percentage of grafting of the product amounts to 0.6%; its melt‐flow index is between 0.5 and 2.0 g/10 min, depending upon ultrasonic intensity, MAH content and grafting temperature. Compared with the method of peroxide initiation, in this method the crosslinking reaction can be prevented easily through the allocation of ultrasonic intensity. The mechanical properties of the improved HDPE/GF composite produced by ultrasonic initiatives are higher than in those produced by peroxide initiatives.
Chaotic volumetric transports in a single‐screw extrusion process
Authors: Hwang W. R. , Kwon T. H. 
Published: April 2004

AbstractVolumetric material transports across distinct regions in the Chaos Screw (CS) system were described in terms of the volume‐preserving lobe dynamics. Kinematic properties of a spatially periodic Poincaré map were studied first with the volume‐ and orientation‐preserving two‐dimensional map, in order to provide mathematical frame works for analyses of manifold structures. The perturbed hyperbolic fixed point and the associated stable and unstable manifolds were obtained numerically. These manifolds form homoclinic tangles, and they divide the cross‐sectional area into three distinct regions: left, right, and outer. Six volumetric flow rates between the three regions were described in terms of the associated lobe dynamics. As the perturbation strength increases, representative flow rates between these regions were found to increase linearly as long as the fraction of no‐barrier zone is small.
Influence of the relative humidity on film formation by vapor induced phase separation
Authors: Caquineau H. , Menut P. , Deratani A. , Dupuy C. 
Published: April 2004

AbstractThe formation of polymer films produced by the phase separation process occurring when a cast poly(etherimide)/N‐Methyl‐2‐Pyrrolidone solution was exposed to humid air was studied. It was found that above a relative humidity value of 27%, the films presented a cell‐like structure. The size of the cells was shown to decrease when the relative humidity increased. This effect was more pronounced at the film/substrate interface than near the surface. A cell‐size gradient from one face of the film to the other was also clearly observed. A phenomenological model has been proposed to explain the morphology obtained by a phase separation induced by the water vapor in the studied system, takin into account thermodynamics and kinetics considerations. In this model, the cell‐like structure setting up is shown to result from a nucleation and growth process accompanied by a coalescence coarsening. It was illustrated by a composition path on the ternary phase diagram. It was shown how the relative humidity influenced the film composition leading to the preferential nucleation compared to the growth and coalescence of the cells. Finally, it was found that the cell‐size anisotropy resulted in the solvent and non‐solvent mass transfers in the film, bringing to the fore the determining role of kinetics.
Structure and properties of oriented polyethylene films
Authors: Srinivas Srivatsan , Brant Patrick , Huang Yu , Paul Donald R. 
Published: April 2004

AbstractCast films of a metallocene Linear Low Density Polyethylene (mLLDPE) have been cold‐drawn in the machine direction in two sequential steps to form ultra‐oriented films. The initial films were cast under low shear conditions to form essentially isotropic films, as shown by very low orientation birefringence. The first draw yields moderately oriented films, which display block‐shear type chevron morphology. Under controlled conditions, void formation occurs during the second draw and the ultradrawn films whiten (become opaque), and display a fine crystalline morphology. Surprisingly, the films do not become more permeable; rather, they become high barrier films. In their ultra‐oriented state, the water vapor transmission of the films is equivalent to that of poly(vinylidene chloride) (PVDC). The transport behavior of the films to various gases was studied using transient permeation methods. The decrease in permeability with orientation is attributed to an increase in the degree of crystallinity and increase in tortuosity due to the blocky crystalline morphology. A decrease in the permeability of the amorphous phase due to an increase in the amorphous phase density is also suggested by the data.
Cure kinetics, gelation, and glass transition of a bisphenol F epoxide
Authors: O'Brien Daniel J. , White Scott R. 
Published: April 2004

AbstractPhenomenological cure kinetic relations for a commercially available amine‐cured epoxy were developed independently using differential scanning calorimetry (DSC) in isothermal and dynamic (constant heating rate) modes and using numerical optimization techniques. The resulting model was found to be independent of the method used to collect reaction rate data. The model was modified at high temperature to account for an observed deviation from Arrhenius behavior. The cure dependence of the glass transition of the material was also investigated with DSC. The gel point as measured by parallel plate rheometry was found to occur at a degree of cure of 0.71, a value significantly advanced from a simple Flory prediction based on the functionality of the cross‐linking agent.
Mixing dynamics in the SMX static mixer as a function of injection location and flow ratio
Authors: Zalc J. M. , Szalai E. S. , Muzzio F. J. 
Published: April 2004

AbstractA detailed Lagrangian analysis of partially mixed structures in an SMX static mixer is presented, with emphasis on laminar flows with Reynolds numbers between 1 and 100. The distribution of a small amount of equal‐viscosity additive is examined based on computing the trajectories of passive tracer particles through the mixer. Three radial positions (one centerline and two off‐center) are chosen for injection and the mixing patterns are compared in order to investigate the effect of injection location on mixing. Mixing measures, such as the decrease in the variation coefficient with axial distance, and the increase in the average rate of stretching, are discussed in order to quantify mixing performance. It is found that mixing rates for the centerline injections are larger than for the off‐center injection positions investigated. The presence of self‐similarity in the stretching field and the mixing patterns, and the exponential decrease in variation coefficient with increasing axial distance provides evidence for chaotic mixing behavior in this device.
An investigation into the relationship between the impact performance of rotationally molded polyethylene products and their dynamic mechanical properties
Authors: Pick Louise Therese , Harkin‐Jones Eileen 
Published: April 2004

AbstractIn this paper, a study of the relationship between the impact performance of rotationally molded polyethylenes and their dynamic mechanical properties is carried out. A wide range of conventional linear low density polyethylene powders and met‐allocene catalyzed linear low density polyethylene powders were rotationally molded and tested. Instrumented falling weight impact tests were carried out over a temperature range of −60°C to 20°C. Dynamic Mechanical Thermal Analysis (DMTA) tests were also carried out between −100°C and 90°C, at a frequency of 100 Hz. Comparisons between the impact performance of metallocene catalyzed LLDPEs and Ziegler‐Natta LLDPEs are made. The transitions evident in the DMTA results are related to changes in impact performance with temperature. The beta transition is found to fall in the transition region between high impact performance at low temperatures and lower impact performance at ambient temperatures.
Electrochemically synthesized polythiophene films with self‐organized microstructure
Authors: Wang Xi‐Shu , Feng Xi‐Qiao 
Published: April 2004

AbstractThe microstructure of electronically conducting polythiophene (Pth) films synthesized electrochemically was studied using a scanning electron microscope. A self‐organization phenomenon was observed in the films, which grew on a substrate with periodically arrayed holes of diameter less than 100 nm. Owing to the low bending stiffness and the high cohesive energy of nanowires, they combined in a self‐assembling manner into an interesting array of bundle shapes, each bundle having about 20–100 bonded nanowires. The physical mechanism of this phenomenon is elucidated using the theory of elastic buckling.