ENG

Distribution by Scientific Domains

Kinds of ENG

  • methods eng


  • Selected Abstracts


    Clinical history and new prognostic indicators in metachromatic leukodystrophy

    JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2004
    U Del Carro
    Objective: To study clinical phenotypes and to increase knowledge of natural history of different variants of metachromatic leukodystrophy (MLD). Background: Little is known about factors influencing age of onset, progression rate and peripheral nerve involvement in MLD due to its rarity, heterogeneity and paucity of serial clinical and instrumental reports. Methods: 15 biochemically and molecularly characterized MLD patients were evaluated along a two-year follow-up period with clinical, electroneurographic (ENG) and brain MRI recordings. Results: Late infantile patients had a progressive and rapid course, whereas juvenile form showed marked variability. Different clinical presentations were associated with similar levels of ARSA activity; mutation screening indicated a high prevalence of rare or private mutations. In all late infantile and in the adult patient, ENG revealed a severe polyneuropathy. In juvenile patients a milder polyneuropathy or even normal tests were found. The earliest MRI change was periventricular white matter signal alterations, with initial involvement of posterior regions in a majority of late infantile patients, while in juvenile forms white matter lesions were mainly anterior. Conclusions: MLD course is highly variable and only partially influenced by age of onset, especially among juvenile patients. No clear-cut correlations exist between clinical phenotype and biochemical or molecular characterization. The presence of peripheral neuropathy at onset seems a strong indicator of a poorer clinical outcome. [source]


    ELECTRONEUROGRAPHY IN GUILLAIN-BARRE, SYNDROME (GBS): SENSITIVITY AND SPECIFICITY

    JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2000
    G. Iuliano
    We assessed clinical sensitivity and specificity of different electroneurographic (ENG) parameters versus clinical diagnosis of GBS. Clinical data of 24 patients affected by upper and lower limb neuropathy were revised. In all the patients the neurophysiologic examination was performed according to the AAEM guidelines for GBS diagnosis. Fourteen patients (10 males, mean age 47.9, range 13-70, and 4 females 71.5, 69,76) received a diagnosis of GBS. The non-GBS group included nine males (59.11, 35,78) and one female (41 years) with different neuropathies (3 diabetic, 2 alcoholic, 5 unknown ethiology). Sensitivity and specificity of various neurophysiologic parameters were calculated. The single classical neurophysiological paremeters gave variable values of sensitivity and specificity. The new variables we introduced, Polineuropathy (diffusion of abnormal findings and F - Wave latency) and Demyelination (distal motor evoked potential amplitude and/or motor conduction blocks) gave the highest value of sensitivity and specificity, when associated. [source]


    Hereditary hemorrhagic telangiectasia: from molecular biology to patient care

    JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 7 2010
    S. DUPUIS-GIROD
    Summary., Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by severe and recurrent nosebleeds, mucocutaneous telangiectases, and, in some cases, life-threatening visceral arteriovenous malformations of various types, including pulmonary, hepatic, cerebral, and spinal. Gastrointestinal telangiectases are frequent and may cause severe bleeding. HHT type 1 results from mutations in ENG on chromosome 9 (coding for endoglin), and HHT type 2 results from mutations in ACVRL1 on chromosome 12 (coding for activin receptor-like kinase 1). Mutations of either of these two genes account for most clinical cases. In addition, mutations in MADH4 (encoding SMAD4), which cause a juvenile polyposis/HHT overlap syndrome, have been described, and recently, an HHT3 locus on chromosome 5 (5q31.3,5q32) has been reported. The mutated genes in HHT encode proteins that modulate transforming growth factor-, superfamily signaling in vascular endothelial cells. Management of patients has changed considerably in the last 20 years, in terms of both treatment and the prevention of complications. The goal of this review was to describe the underlying molecular and cellular physiopathology, explore clinical and genetic diagnostic strategies for HHT, and present clinical management recommendations in order to treat symptomatic disease and to screen for vascular malformations. [source]


    Feasibility of Using Peroneal Nerve Recordings for Deriving Stimulation Timing in a Foot Drop Correction System

    NEUROMODULATION, Issue 1 2003
    Morten Hansen
    Abstract The objective of this research was to demonstrate the potential of using peroneal nerve activity to derive timing control for stimulation in foot drop correction and to attempt recording and stimulation through the same electrode. Two subjects were implanted with cuff electrodes on the peroneal nerve. An input domain was derived from the recorded electroneurogram (ENG) and fed to a detection algorithm based on an Adaptive Logic Network (ALN) for predicting stimulation timing. A switching circuit was furthermore built for switching between stimulator and recorder for combined use of the cuff electrode. The detection was successful, but the accuracy depended on the signal to noise ratio of the recorded ENG. The switching circuit successfully allowed for simultaneous recording and stimulation through the same cuff electrode. We conclude that the peroneal nerve can potentially be used to record sensory information for derivation of a stimulator control signal in a foot drop application, while at the same time being stimulated to activate foot dorsiflexors. [source]


    Real Time Foot Drop Correction using Machine Learning and Natural Sensors

    NEUROMODULATION, Issue 1 2002
    Morten Hansen MScEE
    Abstract The objective of this study was to investigate and test a real time system implemented for Functional Electrical Stimulation (FES) assisted foot drop correction, deriving control timing from signals recorded from a peripheral sensory nerve. A hemiplegic participant was attached with a cuff electrode on the sural nerve connected to a telemetry controlled implanted neural amplifier, and a stimulation cuff electrode on the peroneal nerve connected to an implanted stimulator. An input domain was derived from the recorded electroneurogram (ENG) and fed to a detection algorithm based on an Adaptive Logic Network (ALN) for controlling the timing of the peroneal stimulation. The detection system was tested in real time over a period of 392 days, covering a variety of walking tasks. The detection system's ability to detect heel strike and foot lift without errors and to detect the difference between walking and standing proved to be stable for the duration of the study. We conclude that using ALNs and natural sensors provide a stable and accurate control signal for FES foot drop correction. [source]


    Thermomechanical properties of virgin and recycled polypropylene impact copolymer/CaCO3 nanocomposites

    POLYMER ENGINEERING & SCIENCE, Issue 10 2010
    A. Elloumi
    The effect of successive injection moldings on the thermal, rheological, and mechanical properties of a polypropylene impact copolymer (PP) was investigated. The crystal content decreased as the molecular weight decreased due to chain scission with repeated injection molding. The Young modulus and the yield stress remained constant, despite a drop in the strain to break. Virgin and recycled PP matrix were filled with nanosized calcium carbonate (CaCO3) particles. The effect of morphology on the thermal and mechanical properties of nanocomposites of virgin and recycled PP filled with nanosized CaCO3 particles was also studied. The mechanical properties of the nanocomposites were strongly influenced by the intrinsic toughness of the matrix and the concentration and dispersion of the filler. The yield strength and strain of virgin PP decreased gradually, while its Young's modulus increased slightly with increasing CaCO3 loading. These phenomena were less pronounced for the recycled matrix. Incorporation of nanoparticles to virgin matrix produced an increase in tensile stiffness and ductility, when good dispersion of the filler was achieved. However, the impact strength dropped dramatically for high filler contents. A significant increase in impact strength was observed for the recycled PP. POLYM. ENG. SCI., 50:1904,1913, 2010. 2010 Society of Plastics Engineers [source]


    Effectual dispersion of carbon nanofibers in polyetherimide composites and their mechanical and tribological properties

    POLYMER ENGINEERING & SCIENCE, Issue 10 2010
    Bin Li
    The use of proliferation of nanotechnology in commercial applications is driving requirements for minimal chemical processing and simple processes in industry. Carbon nanofiber (CNF) products possess very high purity levels without the need of purification processing before use and are in growing demand for this quality. Polyetherimide (PEI) has excellent mechanical and thermal performance, but its high viscosity makes its nanocomposites processing very challenging. In this study, a facile melt-mixing method was used to fabricate PEI nanocomposites with as received and physically treated CNFs. The dispersion of CNFs was characterized by scanning electron microscopy, transmitted optical microscopy, and electrometer with large-area electrodes. The results showed that the facile and powerful melt-mixing method is effective in homogeneously dispersing CNFs in the PEI matrix. The flexural and tribological characteristics were investigated and the formation of spatial networks of CNFs and weak interfacial bonding were considered as competitive factors to enhanced flexural properties. The composites with 1.0 wt% CNFs showed flexural strength and toughness increased by more than 50 and 550%, respectively, but showed very high wear rate comparable with that of pure PEI. The length of the CNFs also exerted great influences on both mechanical and tribological behaviors. POLYM. ENG. SCI., 50:1914,1922, 2010. 2010 Society of Plastics Engineers [source]


    A comparison of seven filling to packing switchover methods for injection molding

    POLYMER ENGINEERING & SCIENCE, Issue 10 2010
    David O. Kazmer
    The effectiveness of seven methods for controlling switchover from the filling to packing stage were investigated, including: (1) screw position, (2) injection time, (3) machine pressure, (4) nozzle pressure, (5) runner pressure near the sprue, (6) cavity pressure near the gate, and (7) cavity temperature at the end of flow. The activation threshold for each of the seven switchover methods was iteratively determined so as to produce similar part weights relative to a standard process. A design of experiments was implemented for each of the seven switchover methods that perturbs the process settings by an amount equal to six standard deviations of the standard process so as to replicate the expected long-term process variation. The results suggest that conventional switchover methods (e.g., screw position) had lower short-term variation, but other methods were more robust with respect to rejecting long-term process variation. The merits of different dimensional measurements for quality control are also discussed relative to the society of the plastics industry (SPI) standard tolerances. POLYM. ENG. SCI., 50:2031,2043, 2010. 2010 Society of Plastics Engineers [source]


    Numerical modeling of nonisothermal polymer crystallization kinetics: Flow and thermal effects

    POLYMER ENGINEERING & SCIENCE, Issue 10 2010
    Matthieu Zinet
    A numerical model able to simulate polymer crystallization under nonisothermal flows is developed. It is based on the assumption that the trace of the extra-stress tensor, calculated according to a viscoelastic multimode Upper Convected Maxwell (UCM) model, is the driving force of the flow-induced extra nucleation. Two distinct sets of Schneider equations are used to describe the growth of thermally and flow induced nuclei. The model is then coupled with the momentum equations and the energy equation. As an application, a shear flow configuration between two plates (Couette flow) is simulated. The relative influence of the mechanical and thermal phenomena on the crystallization development as well as the final morphology distribution is then analyzed as a function of the shearing intensity and the cooling kinetics, in terms of nucleation density and crystallite mean sizes. POLYM. ENG. SCI., 50:2044,2059, 2010. 2010 Society of Plastics Engineers [source]


    Process of grafting styrene onto LLDPE by swelling and suspension copolymerization

    POLYMER ENGINEERING & SCIENCE, Issue 9 2010
    Jing Yan
    A technology of swelling and suspension copolymerization was conducted to graft styrene onto linear low-density polyethylene (LLDPE). The graft mechanism of styrene with LLDPE had been described by 1H NMR and IR. The mean particle diameter and size distribution of the products with different proportions of LLDPE to styrene monomer were calculated. The morphology and thermal behavior of copolymers were characterized by scanning electron microscopy and differential scanning calorimetry. The glass transition temperature of copolymers increased with the addition of LLDPE, which proved the existence of the polyethylene- g -polystyrene copolymer. The grafting efficiency and granulation rate of suspension copolymerization were investigated. It was found that the grafting efficiency increased and the granulation rate decreased with the addition of LLDPE. POLYM. ENG. SCI., 50:1713,1720, 2010. 2010 Society of Plastics Engineers [source]


    Crystallization and biodegradation of polylactide/carbon nanotube composites

    POLYMER ENGINEERING & SCIENCE, Issue 9 2010
    Defeng Wu
    The crystallization behavior of polylactide/carbon nanotube composites was studied using differential scanning calorimeter and polarized optical microscope. The nucleation mechanisms and the crystallization kinetics were explored. The results show that the presence of nanotubes has nucleating effect on both the melt crystallization and the cold crystallization of PLA. However, the nanotubes also play the role of physical barrier, impeding the crystal growth dynamically. In the experimental range of temperatures, the presence of nanotubes accelerates the melt crystallization, while retards the overall kinetics of the cold crystallization. The biodegradability of the samples with various crystallization histories was then further examined. The results show that the presence of nanotubes reduces the biodegradation rate of PLA, and the amorphous sample shows the highest degradation levels. Moreover, a lower degradation level is observed both on the surface and inside the sample with melt crystallization history in contrast to the one with cold crystallization history. POLYM. ENG. SCI., 50:1721,1733, 2010. 2010 Society of Plastics Engineers [source]


    Dynamic mechanical properties and morphology of poly(benzyl methacrylate)/epoxy thermoset blends

    POLYMER ENGINEERING & SCIENCE, Issue 9 2010
    Margarita G. Prolongo
    Poly(benzyl methacrylate) (PBzMA)/epoxy thermoset blends of composition 5 to 25 wt% of PBzMA were prepared curing with 4,4,diaminodiphenylmethane (DDM), to study the influence of composition on the morphology and dynamic-mechanical properties of the blends. The cured blends are phase separated in PBzMA-rich phase and epoxy rich-phase. As the PBzMA content increases, the morphology evolves from nodular, to combined and to totally inverted. The analysis of the ,-mechanical relaxations indicates that the glass transition temperatures (Tg) of PBzMA and of epoxy in the blends are different from the neat polymers, this is related to a noncomplete phase separation on curing. The profiles of the loss modulus-temperature curves are correlated with the change in morphology that appears increasing the PBzMA content. The storage modulus-temperature curves are highly dependent on the morphology of the samples. The storage modulus-composition dependence is predicted using several models for two phase composites. POLYM. ENG. SCI., 50:1820,1830, 2010. 2010 Society of Plastics Engineers [source]


    Influence of initial mixing methods on melt-extruded single-walled carbon nanotube,polypropylene nanocomposites

    POLYMER ENGINEERING & SCIENCE, Issue 9 2010
    Vinod K. Radhakrishnan
    We report the first direct comparison of melt-extruded polypropylene,single-walled carbon nanotube (PP/SWNT) nanocomposites prepared by three different initial mixing methods. The standard deviation of the G-band intensity obtained using Raman mapping was found to be the best measure of dispersion uniformity in the extruded composites, and dispersion uniformity was found to generally correlate with rheological and thermal properties. For all three initial mixing methods, both unmodified and sidewall-functionalized purified SWNTs were evaluated. Surprisingly, in all cases, dodecylated SWNTs prepared using the reductive alkylation method were less uniformly dispersed in the final composite than the unmodified SWNTs. The simplest process, dry blending, resulted in poor nanotube dispersion and only polymer crystallization was significantly affected by the presence of the nanotubes. A slightly more complex rotary evaporation process resulted in significantly more uniform dispersion and significant changes in rheological properties, polymer crystallization, and thermal stability. The most elaborate process tested, hot coagulation, enabled the most uniform dispersion and the greatest change in properties but also resulted in some polymer degradation. POLYM. ENG. SCI., 50:1831,1842, 2010. 2010 Society of Plastics Engineers [source]


    Effect of plasma treatment and electron beam radiations on the strength of nanofilled adhesive-bonded joints

    POLYMER ENGINEERING & SCIENCE, Issue 8 2010
    H.M.S. Iqbal
    This investigation highlights the adhesion performance of carbon fiber- and glass fiber-reinforced polyphenylene sulfide when joined by high-performance neat epoxy adhesive and nanofilled epoxy adhesive. A significant increase in the surface energy of these materials is observed after the surface modification with atmospheric plasma treatment. An increase in surface roughness is observed after exposing the surface to plasma. Lap shear testing of untreated and plasma-treated joints is carried out to correlate the improvement in adhesion properties with the joint strength. A considerable increase in joint strength is observed when the surfaces of these materials are modified by atmospheric pressure plasma. There is a further increase in joint strength when the composites are joined by nanofilled epoxy adhesive, and subsequent exposure to electron beam radiations results in minor increase in the joint strength. Finally, the fractured surfaces of the joints are examined and the analysis is performed. POLYM. ENG. SCI., 50:1505,1511, 2010. 2010 Society of Plastics Engineers [source]


    Compatibilization of PP/PAE blends by means of the addition of an ionomer

    POLYMER ENGINEERING & SCIENCE, Issue 8 2010
    A. Granado
    Minor amounts of poly(ethylene- co -methacrylic acid) ionomer neutralized with Zn (PEMA-Zn) were added in the melt state to blends of polypropylene (PP) with up to 40% of poly(amino ether) (PAE) resin. Given the good barrier characteristics of PAE, it is a good candidate to improve the poor barrier properties of PP. However, PP/PAE blends were found to be almost fully immiscible, with a large dispersed phase size and a brittle mechanical behavior. Upon PEMA-Zn addition, the dispersed particle size clearly decreased from diameters of several microns to diameters mostly below 0.5 ,m, indicating that compatibilization occurred. This compatibilization was due to the presence of PEMA-Zn in the two phases of the blends and was additionally proven by the large decrease observed in the interfacial tension. Further, the fine morphology led to an enhancement in the unnotched impact strength of the ternary blends and of their ductile behavior (elongation at break 30- to 40-fold that of the corresponding binary blends). POLYM. ENG. SCI., 50:1512,1519, 2010. 2010 Society of Plastics Engineers [source]


    Dielectric properties of polyethylene terephthalate/polyphenylene sulfide/barium titanate nanocomposite for application in electronic industry

    POLYMER ENGINEERING & SCIENCE, Issue 8 2010
    Monika Konieczna
    Polymer/ceramic nanocomposites designed for application as electronic packaging were prepared using corotating twin-screw extruder. The dielectric properties of the composites made from polyethylene terephthalate (PET), polyphenylene sulfide, and barium titanate were studied as a function of BaTiO3 fraction in the range between 0.75 and 1.5 wt%. Processing parameters were optimized in order to obtain the nanocomposites with appropriate dielectric properties like dielectric permittivity ,,, dielectric losses ,,, and their temperature stability in a wide frequency range. The measurements showed the increase of the dielectric permittivity value ,, in the composites in comparison to both pure polymers. The dielectric loss factor tg, of the composites was found to be much smaller than that of the pure PET. The weak influence of the ceramics on the temperature stability of the dielectric properties of the composites was stated. POLYM. ENG. SCI., 50:1613,1619, 2010. 2010 Society of Plastics Engineers [source]


    Maleated amorphous ethylene propylene compatibilized polyethylene nanocomposites: Room temperature nonlinear creep response

    POLYMER ENGINEERING & SCIENCE, Issue 8 2010
    Ali Shaito
    Nonlinear creep of polyethylene and its nanocomposites remains an area of significant interest. Maleated polyethylene is often used as a compatibilizer to ensure enhanced dispersion. This article investigates blown films of linear low-density polyethylene and its nanocomposites with montmorillonite-layered silicate (MLS). An amorphous ethylene propylene copolymer grafted maleic anhydride (amEP) was added to enhance the interaction between the PE and the MLS. Tensile results indicate that the addition of amEP and MLS separately and together produces a synergistic effect on the mechanical properties of the neat PE. Nonlinear creep was analyzed by examining creep and recovery of the films with a Burger model and the Kohlrausch-Williams-Watts relation. A consistent decrease in unrecoverable plastic strain was obtained in the nanocomposite samples. A decreased retardation time associated with MLS presence was determined. POLYM. ENG. SCI., 50:1620,1632, 2010. 2010 Society of Plastics Engineers [source]


    Gel-spun polyacrylonitrile fiber from pregelled spinning solution

    POLYMER ENGINEERING & SCIENCE, Issue 7 2010
    Lianjiang Tan
    Polyacrylonitrile (PAN) fibers have been gel spun from pregelled PAN spinning solution. The pregelled solution had network structure with elevated spinnability, the as-spun fiber from which had more circular cross-section and reduced skin-core difference. Drawing was more effective in inducing the segmental orientation and crystallization in gel-spun fiber than in dry,wet spun fiber. The mechanical properties of the gel-spun fiber were better than those of the dry,wet spun fiber after multi-stage drawing. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]


    Changes in lamellar arrangement of crystalline and flexible fluorinated transparent films with drawing

    POLYMER ENGINEERING & SCIENCE, Issue 7 2010
    Atsuhiro Fujimori
    In recent times, a "crystalline" and flexible optical waveguide candidate with excellent heat-resistance and dimensional stability are developed. For the practical use of this crystalline optical film in the near future, an accurate control of the solid-state structure is indispensable because of the necessity of reducing light refraction at the crystalline/amorphous interface. In this study, changes in the fine structure and lamella arrangement upon drawing poly[tetrafluoroethylene- co -(perfluoroethylvinylether)] (EFA) transparent crystalline films were investigated by using wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) methods. The EFA was crystallized as a lamella crystal in the films and formed a thicker lamella. Upon the drawing of the EFA films, four-point SAXS diagrams developed in the photograph at through direction to the film, which implied that a particular type of layer structure, an alternately tilted lamella arrangement known as the herringbone, was formed. From the result of WAXD and SAXS measurements at edge direction to the film, it is found that formation of isotropic disordered lamella arrangement. Therefore, it is indicated that three-dimensional lamella arrangement in this fluorinated transparent film forms uniaxially cylindrical symmetry. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]


    Reinforcement of liquid ethylene,propylene,dicyclopentadiene copolymer based elastomer with vinyl functionalized multiwalled carbon nanotubes

    POLYMER ENGINEERING & SCIENCE, Issue 7 2010
    Hongfu Zhou
    A methodology for reinforcement of liquid ethylene,propylene,dicyclopentadiene copolymer (liquid-EPDM) based elastomer with multiwalled carbon nanotubes (MWCNTs) was proposed. Acid-treated MWCNTs were first reacted with poly(acryloyl chloride) (PACl) leading to a grafted encapsulation, which were subsequently reacted with hydroxy ethyl acrylate (HEA) to generate vinyl groups. Thus obtained vinyl groups functionalized MWCNTs (vinyl-MWCNTs) were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The vinyl-MWCNTs were blended with liquid-EPDM and subjected to co-curing; an intercrosslinked structure was obtained via the free radical polymerization among the vinyl groups on vinyl-MWCNTs and the double bonds on liquid-EPDM. As a result, the vinyl-MWCNTs and the cured EPDM matrix were covalently linked. The chemical interfacial interaction between vinyl-MWCNTs and the cured matrix were observed by scanning electron microscope, which provided obvious reinforcement of elastomer. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]


    Simulations of instability in fiber spinning of polymers

    POLYMER ENGINEERING & SCIENCE, Issue 7 2010
    Atanas Gagov
    This work determines the critical regimes beyond which the melt fiber spinning for noncrystallizable polymeric liquids becomes unstable. The critical draw ratio of the process is established using linear stability analysis for both isothermal and nonisothermal fiber spinning regimes. In addition, nonlinear isothermal analysis describes the complete range of the stable and unstable conditions for fiber spinning. Unlike previous studies, this research uses quite realistic viscoelastic constitutive equations extensively tested for five polymer liquids, which provides a good comparison of our calculations with available experimental data. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]


    Effect of sparse long-chain branching on the step-strain behavior of a series of well-defined polyethylenes

    POLYMER ENGINEERING & SCIENCE, Issue 7 2010
    Christopher D. McGrady
    The effect of sparse long chain branching, LCB, on the shear step-strain relaxation modulus is analyzed using a series of eight high-density polyethylene (HDPE) resins. Strains of 1 to 1250% are imposed on materials with LCB content ranging from zero to 3.33 LCB per 10,000 carbon atoms. All materials are observed to obey time,strain separation beyond some characteristic time, ,k. The presence of LCB is observed to increase the value of ,k relative to the linear resin. The behavior of the relaxation modulus at times shorter than ,k is investigated by an analysis of the enhancement seen in the linear relaxation modulus, G0(t), as a function of strain and LCB content. This enhancement is seen to (1) increase with increasing strain in all resins, (2) be significantly larger in the sparsely branched HDPE resins relative to the linear HDPE resin, and (3) increase in magnitude with increasing LCB content. The shape and smoothness of the damping function is also investigated. The finite rise time to impose the desired strain is compared to the Rouse relaxation time of linear HDPE resins studied. Sparse LCB is found to increase the magnitude of the relaxation modulus at short times relative to the linear resin. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]


    Structural estimation of particle arrays at air,water interface based on silica particles with well-defined and highly grafted poly(methyl methacrylate)

    POLYMER ENGINEERING & SCIENCE, Issue 6 2010
    Jung-Min Moon
    Silica nanoparticles with well-defined, highly grafted dense poly(methyl methacrylate) (MMA) were prepared by surface-initiated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) of methyl methacrylate with an initiator-fixed silica particle in the presence of air. Two different polymerizations of MMA were carried out under the same conditions using tris[2-(dimethylamino)ethyl]amine (Me6TREN) and N,N,N,,N,,N,-pentamethyldiethylene-triamine (PMDETA) as the ligand, respectively. In the CuCl2/PMDETA system, polymerization appeared to be more controlled with a lower polydisperisty compared with the CuCl2/Me6TREN system. The monolayer of these particles was formed at the air,water interface using Langmuir-Blodgett (LB) technique. Multilayers of the particles were fabricated by repetition of LB depositing. A surface pressure,area (,,A) measurement and SEM observation were used to characterize the particle arrays. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]


    The effects of alumina and silica nanoparticles on the cure kinetics of bisphenol E cyanate ester

    POLYMER ENGINEERING & SCIENCE, Issue 6 2010
    Xia Sheng
    Nanoparticles can be used as fillers to reinforce polymers, forming nanocomposites with better thermomechanical properties than composites with macrosized fillers. Furthermore, the addition of nanoparticles may influence the curing behavior of the polymer matrix during processing. In this study, the effect of various loadings of alumina or silica nanoparticles on the cure kinetics of bisphenol E cyanate ester (BECy) is investigated by differential scanning calorimetry (DSC). Alumina nanoparticles are shown to have a catalytic effect on the cure of BECy. The greater catalytic effect of alumina nanoparticles, compared with silica, is attributed to the increased number of hydroxyl groups on the surface and the Lewis acidity of ,-phase alumina. Kinetic parameters were obtained from dynamic DSC experiments. For an autocatalytic model of the cure process, the kinetic parameters obtained from the model suggest that the addition of alumina nanoparticles changed the cure reaction mechanism of BECy. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]


    Synthesis and characterization of poly(butyl acrylate- co -ethylhexyl acrylate)/ poly(vinyl chloride)[P(BA-EHA)/PVC] novel core-shell modifier and its impact modification for a poly(vinyl chloride)-based blend

    POLYMER ENGINEERING & SCIENCE, Issue 6 2010
    Mingwang Pan
    Synthesis of poly(butyl acrylate-co-ethylhexyl acrylate)-core/poly(vinyl chloride)-shell [P(BA-EHA)/PVC] used as a modifying agent of PVC via semicontinuous seeded emulsion copolymerization is reported here. Diameter distributions and morphology of the composite latex particles were characterized with the aid of particle size analyzer and transmission electron microscopy (TEM). The grafting efficiency (GE) and grafting ratio (GR) of vinyl chloride (VC) grafted onto the P(BA-EHA) with varying content of crosslinking agent and core-shell ratios were investigated. TEM studies indicated that the P(BA-EHA)/PVC latex particles have core-shell structure, and the P(BA-EHA) rubbery particles in blending materials were uniformly dispersed in PVC matrix. Dynamic mechanical analysis (DMA) results revealed that the compatibility between the P(BA-EHA) and the PVC matrix was significantly improved due to the presence of the P(BA-EHA)-grafted-VC copolymer. The notched impact strength of the blending material with 3 wt% of rubber content was seven times that of the PVC. Linear regressions of mechanical properties as loading of the modifier were made. The resulting data of notched impact strength and elongation at break for the blending materials deviated significantly from regression lines within 3,4.5 wt% of the P(BA-EHA) content. The PVC blends modified by the modifier exhibited good toughness and easy processability. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]


    Effect of polyethylene oxide,polyethylene glycol content and humidity on performance of electro-active paper actuators based on cellulose/polyethylene oxide,polyethylene glycol microcomposite

    POLYMER ENGINEERING & SCIENCE, Issue 6 2010
    Suresha K. Mahadeva
    The effect of humidity and polyethylene oxide (PEO),polyethylene glycol (PEG) content on the actuator performance of cellulose/PEO,PEG microcomposites was studied. Upon blending 5% PEO,PEG, the maximum bending displacement of the actuator increased nearly twice compared to that of cellulose EAPap actuator. However, further increase of PEO,PEG content resulted in decreased actuator performance. This might be due to the increased intermolecular interaction by hydrogen bonding that reduces the mobility of the molecules. The actuator performance test showed that the increase in humidity level rather reduced the maximum displacement of the actuators. X-ray diffractogram and Fourier transform infrared spectrum analysis suggested a structural change of the microcomposites as well as disruption of cellulose/PEO,PEG association attributed to the actuator performance degradation at high humidity level. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]


    Effects of film and substrate dimensions on warpage of film insert molded parts

    POLYMER ENGINEERING & SCIENCE, Issue 6 2010
    Seong Yun Kim
    Three-dimensional flow and structural analyses were carried out for film insert injection molding to investigate warpage of film insert molded (FIM) parts with respect to variation of film and substrate thickness. Asymmetry of temperature distribution in the thickness direction was increased with increasing film thickness but decreased with increasing substrate thickness. Asymmetry of the in-mold residual stress distribution in the FIM specimen was generated by the nonuniform temperature distribution, and it was increased with increasing film thickness but reduced with increasing substrate thickness. Warpage of the ejected FIM specimen was determined by relaxation of the asymmetric in-mold residual stress distribution, and it was increased with increasing film thickness but reduced with increasing substrate thickness. Warpage of FIM specimens annealed at 80C for 30 min showed complex behavior, and the behavior was understood by using factors such as degree of warpage of the ejected part, thermal shrinkage of the inserted film, and retardation of heat transfer. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]


    Dissolution of waste plastics in biodiesel

    POLYMER ENGINEERING & SCIENCE, Issue 5 2010
    Ying Zhang
    The dissolution behavior of polystyrene (PS) and low-density polyethylene (LDPE) in biodiesel was investigated with an eye towards developing methods to dispose waste plastics by burning them with fuel. To complement and guide the experimental investigations, molecular dynamics simulations were performed to calculate solubility parameters, cohesive energy densities, Flory-Huggins , parameters and phase diagrams of the target systems. Dissolution kinetics of PS and LDPE in methyl esters was monitored by gravimetry, from which parameters such as dissolution rates, activation energies, and scaling indices were estimated. The shear viscosity of the polymer solutions was measured to ascertain their suitability as fuel mixtures. The dissolution of PS in biodiesel appears to be controlled by the diffusion of polymer chains through a boundary layer adjacent to the polymer/solvent interface. Taken together, the experimental and modeling studies provide a predictive toolbox to design biodiesels of different compositions that will dissolve commodity polymers such as PS and LDPE to be used as fuels in engines. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]


    Hysteresis measurements and dynamic mechanical characterization of functionally graded natural rubber,carbon black composites

    POLYMER ENGINEERING & SCIENCE, Issue 5 2010
    S.S. Ahankari
    Functionally graded polymer composites (FGPCs) were prepared by construction based layering method employing natural rubber (NR) as a matrix and carbon black (CB) in graded form. CB particles were graded along the rectangular geometry polymer matrix comprising the variation of particle volume fraction along thickness direction. These FGPCs were characterized through hysteresis measurements and compared with uniformly dispersed polymeric composites (UDPCs) maintaining the same average amount of filler. Dynamic mechanical properties of these FGPCs and UDPCs were also compared. Dynamic mechanical characterization revealed that FGPCs show much higher storage modulus than the corresponding UDPCs for any given combination of stacking sequence. Loss tangent of FGPCs was also observed to be lesser when compared to UDPCs leading to less hysteretic losses followed by lesser heat buildup in the composite. Hysteresis measurements accorded with the results of dynamic mechanical characterization. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]


    Structure, electrical and optical properties of (PVA/LiAsF6) polymer composite electrolyte films

    POLYMER ENGINEERING & SCIENCE, Issue 5 2010
    Madhu Mohan Varishetty
    In this work, Li+ ion conducting polymer composite electrolyte films (PECs) were prepared based on poly (vinyl alcohol) (PVA), lithium hexafluoro arsenate (LiAsF6), and ceramic filler TiO2 using solution cast technique. The XRD and FTIR spectra were used to determine the complexation of the PVA polymer with LiAsF6 salt. The ionic conductivities of the (PVA + LiAsF6) and (PVA + LiAsF6 + TiO2) films have been determined by the A.C. impedance measurements in the temperature range 320,440 K. The maximum conductivity was found to be 5.10 10,4 S cm,1 for PVA:LiAsF6 (75:25) + 5 wt% TiO2 polymer composite film at 320 K. The calculation of Li+ ion transference number was carried out by the combination of A.C. impedance and D.C. polarization methods and is found to be 0.52 for PVA:LiAsF6 (75:25) + 5 wt% TiO2 film. Optical properties such as direct energy gap, indirect energy gap, and optical absorption edge values were investigated in pure PVA and salt complexed PVA films from their optical absorption spectra in the wavelength range of 200,600 nm. The absorption edge was found at 5.76 eV for undoped film, while it is observed at 4.87 and 4.70 eV for 20 and 25 wt% LiAsF6 doped films, respectively. The direct band gaps for these undoped and salt doped PVA films were found to be 5.40, 5.12, and 4.87 eV, respectively, whereas the indirect band gaps were determined as 4.75, 4.45, and 4.30 eV. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]