bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear temperature control of a batch suspension polymerization reactor
Authors: Shahrokhi Mohammad , Fanaei Mohammad Ali
Published: April 2004

This paper concerns nonlinear temperature control of a batch polymerization reactor where suspension polymerization of methyl methacrylate (MMA) takes place. For this purpose, four control algorithms, namely, a fix proportional‐integral (PI) controller, an adaptive proportional‐integral‐derivative (PID) controller and two globally linearizing control (GLC) schemes, one for known kinetic model (GLC‐I) and the other for unknown kinetic model (GLC‐II), are selected. The performances of these controllers are compared through simulation and real‐time studies in the presence of different levels of parameter uncertainty. The results indicate that GLCI and GLC‐II have better performances than fix PI and adaptive PID, especially in case of strong gel effect. The worst performance belongs to adaptive PID because of rapid model changes in gel effect region. GLC‐II has a simpler structure than GLC‐I and can be used without requiring the kinetic model. In implementation of GLC‐I the closed loop observer should be used because of model uncertainties.
Morphology development during blending of immiscible polymers in screw extruders
Authors: Tyagi Sandeep , Ghosh Anup K.
Published: April 2004

The present work reports evolution of morphology from initial (presence of striation) to final (droplet formation) stages in a single‐screw extruder. Morphology development during the blending process controls the final size of the dispersed phase, which in turn significantly affects the properties of the blends. The experiments were carried out using a 70/30 wt% polypropylene/ethylene vinyl acetate (PP/EVA) blend; samples were collected along the length of the screw, by screw pullout experiment, to analyze the size and size distribution of the dispersed phase present both as striated layers and subsequently as droplets. Average size of the dispersed phase and standard deviation were taken into account to monitor the morphology evolution along the length of the screw. Pre‐breakup morphology development was studied by analyzing the sample collected from the feed zone of the extruder in terms of upper and lower layers along the cross section of screw channel. Examination of micrographs revealed the existence of pattern of ordered striations along the length of the melting zone containing striations from average size of 1000 μm down to 50 μm decreasing rapidly along the length of the screw. The breakup process was captured at the start of compression zone where step‐up in the shear as well as elongational flow was applied due to decrease in the channel depth along the compression zone. The observed droplet size formed by the breakup of filaments is found to be in accordance with theory. The final droplet size is found to be governed by the emulsification process occurring as a result of stretching, breakup and coalescence in the metering section of the screw and is in the order of 2 μm.
Free radical bulk polymerization in cylindrical molds
Authors: Fontes C. E. , Lage P. L. C. , Pinto J. C.
Published: April 2004

Bulk styrene homopolymerization in cylindrical molds was studied in order to simulate the reactive injection process when the reaction kinetics was much slower than the filling process. Mathematical models were built and implemented, allowing the analysis of certain kinetic phenomena, such as the gel‐effect, and the relevance of natural convection. Based on a detailed kinetic mechanism, the polymer properties (average molecular weight and polydispersity) and monomer conversion were calculated as functions of spatial coordinates and time. The results obtained show that polymer properties and monomer conversion may be very heterogeneous inside the cylindrical mold, although insensitive to variations of the diffusion coefficient, so that defects are expected to appear as a consequence of the heterogeneity of polymer properties inside the mold. Experiments confirmed the simulation results. Simulations indicate that heterogeneities may be expected to increase when the reaction rates are one order of magnitude higher, as in acrylic acid polymerizations.
Modeling/simulating the injection molding of isotactic polypropylene
Authors: Hieber C. A.
Published: April 2004

A unified formulation is presented for modeling the injection molding of isotactic polypropylene (i‐PP). The crystallization kinetics are based upon the differential Nakamura equation in which the characteristic time is dependent upon temperature, pressure and flow‐induced shear stress, without any explicit need for an induction time. A Cross/WLF model is used to represent the shear viscosity in which ηO is dependent upon temperature, pressure and crystallinity. Use is made of a recent correlation for the PVT behavior of i‐PP with an explicit dependence upon crystallinity. A finite‐difference implementation of the modeling is applied to two independent molding experiments available from the literature, with notable results concerning the late‐time cavity pressure traces and time‐dependent gapwise shrinkage prior to ejection.
Techniques for reducing residual monomer content in polymers: A review
Authors: Araújo P. H. H. , Sayer C. , Giudici R. , Poço J. G. R.
Published: April 2004

Reducing the residual monomer content is a desire of every polymer producer, as a product with no or very low levels of residual monomer would have a different commercial appeal. The presence of residual monomer may create hazards to workers as a result of long‐term exposure during polymer processing and sometimes even to customers. There are several techniques for reducing residual monomer content and the industrial importance that has been given to the presence of residual monomers in polymeric products is reflected in the number of patents involving residual monomer reduction techniques. Nevertheless, choosing the best, or the most adequate, technique is not always an easy task, and one still observes a relative lack of scientific literature on this subject. The technique to be employed will depend upon polymer application, which determines the grade of purity, and also on polymer quality, as some monomer reducing techniques might change polymer properties. The main objective of this review is to summarize and discuss the principal methods employed for reducing residual monomer content.
Ultradrawing behavior of gel films of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends at varying drawing conditions
Authors: Yeh Jen‐taut , Chang Sheng‐shan
Published: April 2004

A systematic study of the influence of the drawing temperature and rate on the ultradrawing properties of film samples prepared from gel solutions of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends is reported. At a fixed drawing rate, the achievable draw ratios reached a maximum value when each film specimen was drawn at a temperature near its optimum temperature (Top). It is interesting to note that the Top values of each film sample increased consistently with the drawing rate. The achievable draw ratio of each film sample drawn at a constant rate and a temperature near Top is referred to as the Draop, which reached another maximum value as the drawing rates approached an optimum value. Dynamic mechanical analysis of the film sample exhibited an extraordinary high transition peaked at temperature near 95°C, which is again very close to the Top value found for the film sample drawn at a relatively low rate. On the other hand, the birefringence values and tensile strengths of the film specimen were found to improve significantly with the draw ratios, although the improvement of these properties reduced significantly at high draw ratios. Moreover, both the drawing temperature and rate showed beneficial influence on the birefringence, and tensile strengths of the drawn film specimens. Possible mechanisms accounting for these interesting deformation properties are suggested.
Energy absorption capability of recycled plastic bottles
Authors: Muller Mark K. , Majerus John N.
Published: April 2004

The main objective of this study was to explore the potential effectiveness of using recycled plastic bottles as a material for roadside crash‐barriers. A test program was conducted to compile data on the energy‐absorbing potential of commonly available plastic bottles. The main and secondary factors in plastic bottle energy‐absorption were identified and orthogonal arrays were used to define the test matrix, thereby avoiding the full factorial number of experiments. The results of the study were energy‐absorption data for a range of commercially available plastic bottles. The data are for various filler materials and two loading directions on the bottles. Analysis‐of‐variance was used to identify the most significant factors in energy absorption. The main conclusion of the study was that commercially available plastic bottles, when filled with the appropriate filler materials, are capable of absorbing significant amounts of crush energy. The main recommendation was that the economic feasibility of recycled plastic bottles in various types of crash barriers be explored, including more efficient or more practical filler materials.
Replication of sub‐micron features using amorphous thermoplastics
Authors: mönkkönen Kari , Pakkanen Tuula T. , Hietala Joni , Pääkkönen Esko J. , Pääkkönen Pertti , Jääskeläinen Timo , Kaikuranta Terho
Published: April 2004

A comprehensive experimental study was carried out to replicate sub‐micron features using the injection molding technique. For the experiments, five different plastic materials were selected according to their flow properties. The materials were polycarbonate (PC), styrene‐butadiene block copolymer (SBS), impact modified poly(methyl methacrylate), methyl methacrylate‐acrylonitrile‐butadiene‐styrene polymer (MABS), and cyclic olefin copolymer (COC). Nanofeatures down to 200‐nm line width and with aspect ratios (aspect ratio = depth/width) of 1:1 could be replicated. In all selected materials, the greatest differences between the materials emerged when the aspect ratio increased to 2:1. The most favorable results were obtained with the use of high flow polycarbonate as the molding material. The best replication results were achieved when melt and mold temperatures were higher than normal values.
Electrical properties of composites as affected by the degree of mixedness of the conductive filler in the polymer matrix
Authors: Kalyon Dilhan M. , Birinci Elvan , Yazici Rahmi , Karuv Bahadir , Walsh Shawn
Published: April 2004

The development of the electrical properties of composites as a function of the degree of mixedness of a conductive filler distributed into an insulating polymer is investigated. A wide‐angle X‐ray diffraction (WAXD)‐based quantitative phase analysis method was used to characterize the variations of the concentrations of the insulating binder and the conductive particles around their mean values as a function of mixing time in an intensive batch mixer. Increasing the time and hence, the specific energy input, during the mixing process results in a more homogeneous spatial distribution of the conductive filler in the polymeric matrix, which in turn results in a decrease of the volume conductivity of the composite. The decreasing conductivity of the composite is attributed to the better coating and hence the isolation of the conductive particles from each other, thus hindering the formation of a conductive network “percolation”. Overall, these results suggest that the control of the electrical properties of conductive composites could benefit from a good understanding and adequate control of the dynamics of the mixing process and the resulting degree of mixedness of the conductive particles in the polymer matrix.
Evolution of phase behavior and orientation in uniaxially deformed polylactic acid films
Authors: Kokturk G. , Piskin E. , Serhatkulu T. F. , Cakmak M.
Published: April 2004

The development of crystalline structure and orientation during uniaxial stretching of cast amorphous linear and branched lactic acid films were investigated in the rubbery temperature ranges that spans between glass transition temperature and cold crystallization temperature. This material exhibited almost ideal stress‐strain behavior in the temperature range 65–80°C. Because of its strain crystallizability, films with uniform thickness can be obtained at high deformation levels as a result of self‐leveling. Branching was found to retard this self‐leveling through its slightly detrimental effect on the strain hardening. Upon stretching the material undergoes rapid orientation in the amorphous state and beyond a critical level very sharp and highly oriented β crystalline form chains with −3/1 helix. If the temperature is at or below Tg, with additional stretching, the films were found to revert to a highly oriented amorphous state through the destruction of the crystalline domains. At higher temperatures, further stretching results in continuation of improvement in crystalline order.
Accelerated ultraviolet weathering of PVC/wood‐flour composites
Authors: Matuana Laurent M. , Kamdem Donatien P.
Published: April 2004

Ultraviolet weathering performance of polyvinyl chloride (PVC) filled with different concentrations of wood flour was studied. Extruded PVC/wood‐flour composite samples were subjected to cyclic ultraviolet lamps/condensation exposures and assessed over a total of 400 and 2600 hours. Each assessment consisted of DRIFTFTIR and XPS collections, contact angle measurement, color measurement, and tensile property testing. The experimental results indicated that wood flours are effective chromophore materials since their incorporation into a rigid PVC matrix accelerated the degradation of the polymeric matrix. Photodegradation converted unfilled PVC samples to a colored material of lower extensibility. Although composite samples exhibited greater discoloration than unfilled PVC samples, they retained all their original strength and stiffness properties even after 2600 hours of cyclic UV irradiation/condensation exposures.
Spatially homogeneous gelation in liquid composite molding
Authors: Comas‐cardona Sebastien , Ziaee Saeed , Advani Suresh G.
Published: April 2004

On‐line mixing of the resin with its curing agents prior to injection into a mold is a common industrial technique for fabricating composite parts. For vinyl‐ester resins that cure via free radical polymerization, the concentrations of retarder, accelerator, and initiator are pre‐selected and cannot be changed during the injection. Hence, the resin that enters the mold the earliest has cured longer than the resin that enters the mold later, since the gel time for the resin is the same, owing to the fixed ratio of the curing agents. This approach leads to inhomogeneous cure of the resin and consequently to longer residence time of the resin in the mold. It requires an additional 50 to 75 percent of the filling time before a part can be de‐molded. In this study, it is shown that by adjusting the concentration of curing agents during the injection, a more homogeneous gel time throughout the mold can be achieved. The time to de‐mold is reduced to 18‐24 percent of the filling time. Sensors that measure the conductivity of the resin were used to detect the location and monitor the cure of vinyl‐ester. This approach could be extended to other resin systems to control the spatial curing of the resin in the mold.
Interpenetrating polymer networks based on carboxylated nitrile rubber and poly(alkyl methacrylate)s
Authors: Manoj N. R. , Ratna D. , Dalvi V. , Chandrasekhar L. , Patri M. , Chakraborty B. C. , Deb P. C.
Published: April 2004

A series of interpenetrating polymer networks (IPNs) based on carboxylated nitrile rubber (XNBR) and poly(alkyl methacrylate)s such as poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) (PBuMA) were synthesized. The compositions of the IPNs were also varied by changing the swelling time of the rubber in the methacrylate monomer. The tensile and dynamic mechanical properties of the IPNs were studied. The dynamic mechanical properties in the range of 1–105 Hz were obtained by the time‐temperature superposition of the data under multifrequency mode, which indicated high tanδ with good storage modulus in the entire frequency range. This indicates the suitability of these IPNs as vibration and acoustic dampers.
Accelerated aging of polyimide/titanium adhesive bonds using the notched coating adhesion test
Authors: Giunta Rachel Knudsen , Kander Ronald G.
Published: April 2004

The effect of elevated temperature aging on the interphase of a polyimide adhesive and a titanium substrate has been investigated. An interfacially debonding adhesive test was applied, and the adhesive/substrate interphase was characterized through an analysis of the failure surfaces. To facilitate the aging study, an “openfaced” adhesive geometry, the notched coating adhesion (NCA) test, was used. Use of this adhesive geometry allows an acceleration of diffusion‐related aging phenomena by up to two orders of magnitude, as compared to a traditional “sandwiched” bond. The failure surfaces were characterized using X‐ray photoelectron spectroscopy and optical microscopy. Bulk adhesive properties were investigated using differential scanning calorimetry and solvent uptake. Although there was evidence of polyimide degradation within the interphase, only minor changes in the bulk polyimide properties were detected. This indicates that the adhesive may be degrading preferentially in the interphase region.
Crown ether‐modified clays and their polystyrene nanocomposites
Authors: Yao Hongyang , Zhu Jin , Wilkie Charles A. , Morgan Alexander B.
Published: April 2004

Crown ether‐modified clays were obtained by the combination of sodium and potassium clays with crown ethers and cryptands. Polystyrene nanocomposites were prepared by bulk polymerization in the presence of these clays. The structures of nanocomposites were characterized by X‐ray diffraction and transmission electron microscopy. Their thermal stability and flame retardancy were measured by thermogravimetric analysis and cone calorimetry, respectively. Nanocomposites can be formed only from the potassium clays; apparently the sodium clays are not sufficiently organophilic to enable nanocomposite formation. The onset temperature of the degradation is higher for the nanocomposites compared to virgin polystyrene, and the peak heat release rate is decreased by 25% to 30%.
The effect of crystallization on the structure and morphology of polypropylene/clay nanocomposites
Authors: Maiti Pralay , Nam Pham Hoai , Okamoto Masami , Kotaka Tadao , Hasegawa Naoki , Usuki Arimitsu
Published: April 2004

The effect of crystallization on the structure and morphology of maleic anhydride grafted polypropylene (PP‐MA)/clay (montmorillonite) nanocomposites (PPCNs) is presented. Wide‐angle X‐ray diffraction (WAXD) measurements of PPCNs crystallized at different temperatures show that the extent of intercalation increases with the crystallization temperature. The enhancement of intercalation occurs with lower clay content PPCNs, and maximum intercalation takes place for 4 wt% clay content. The mechanism of intercalation has been proposed through crystallization. Excess γ‐form of the crystallite of PP‐MA appears in presence of clay, possibly because of the confinement of the polymer chain between the clay particles. WAXD data also reveals that d‐spacing increases gradually with clay content. The decrease of spherulitic size is observed with increasing clay content, which indicates that clay particles act as nucleating agents. Lamellar textures have been explored by using small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM), which exhibit that both the lamellar thickness and long period of the PPCNs are higher than those of PP‐MA.
Foam processing and cellular structure of polypropylene/clay nanocomposites
Authors: Nam Pham Hoai , Maiti Pralay , Okamoto Masami , Kotaka Tadao , Nakayama Takashi , Takada Mitsuko , Ohshima Masahiro , Usuki Arimitsu , Hasegawa Naoki , Okamoto Hirotaka
Published: April 2004

Polypropylene (PP)/clay nanocomposites (PPCNs) were autoclave‐foamed in a batch process. Foaming was performed using supercritical CO2 at 10 MPa, within the temperature range from 130.6°C to 143.4°C, i.e., below the melting temperature of either PPCNs or maleic anhydride‐modified PP (PP‐MA) matrix without clay. The foamed PP‐MA and PPCN2 (prepared at 130.6°C and containing 2 wt% clay) show closed cell structures with pentagonal and/or hexagonal faces, while foams of PPCN4 and PPCN7.5 (prepared at 143.4°C, 4 and 7.5 wt% clay) had spherical cells. Scanning electron microscopy confirmed that foamed PPCNs had high cell density of 107–108 cells/mL, cell sizes in the range of 30–120 μm, cell wall thicknesses of 5–15 μm, and low densities of 0.05–0.3 g/mL. Interestingly, transmission electron microscopic observations of the PPCNs' cell structure showed biaxial flow‐induced alignment of clay particles along the cell boundary. In this paper, the correlation between foam structure and rheological properties of the PPCNs is also discussed.
Morphology and rheological properties of polypropylene/reactive elastomer blends
Authors: Marguerat Frédérique , Carreau Pierre J. , Michel Alain
Published: April 2004

The relation of morphology to the linear viscoelastic properties for polymer blends consisting of an inert polypropylene and an elastomeric dispersed phase, made of two miscible copolymers, EVA and EMA, was investigated. The rheological properties of the elastomeric phase were modified by crosslinking in presence of an organometallic catalyst. The activation energy for the transesterification reaction taking place between EVA and EMA has been determined by following the increases of the complex viscosity with time and temperature. The Palierne model has been used to describe the linear viscoelastic behavior of the blends, and to estimate the interfacial tension between the immiscible components. The model was shown to describe relatively well the linear viscoelastic properties of reactive and nonreactive blends containing 30% or less elastomer. In parallel, the morphology of reactive and nonreactive blends (i.e. without catalyst in the elastomeric phase), before and after rheological experiments, has been determined using scanning electron microscopy. The size of the dispersed elastomeric particles for reactive blends prepared using an internal mixer was found to be, in most cases, much smaller than that for nonreactive blends.
Effect of dynamic vulcanization on the microstructure and performance of polyethylene terephthalate/elastomer blends
Authors: Ma Pei Lian , Favis Basil D. , Champagne Michel F. , Huneault Michel A. , Tofan Florin
Published: April 2004

Blends of polyethylene terephthalate (PET) and ethylene‐ethyl acrylate‐maleic anhydride terpolymer (E‐EA‐MAH) were dynamically crosslinked in a one‐step extrusion process. An amine‐terminated glycol reacting with MAH moieties was used as the crosslinking agent. The effect of blend composition and dynamic crosslinking on the microstructure and mechanical properties were investigated. Blend ratios ranging from 80:20 to 20:80 PET/E‐EA‐MAH were studied. The region of phase inversion was located for uncrosslinked and dynamically crosslinked blends. The rheological characterization was also carried out for these blends in comparison with the neat materials. After dynamic crosslinking, the phase inversion is shifted from the 30–40% range to the 70–80% range of elastomer content. This shift is induced by the increase of viscosity and elasticity of the network formed. Dynamically crosslinked blends show significant improvements in impact strength but also exhibit a decrease in elongation at break.
Effect of the dispersed phase fraction on particle size in blends with high viscosity ratio
Authors: Cho Y. G. , Kamal M. R.
Published: April 2004

It has been reported that for polymer blends with high viscosity ratio (>1), the size of the dispersed particles decreases with increasing volume fraction of the dispersed phase. In order to explain this effect, an equation was derived for the affine deformation of an imaginary plane of the dispersed phase in stratified two‐phase steady, simple, shear flow. The model predicts that for viscosity ratio >1, the deformation rate increases with volume fraction of the dispersed phase, and the shear stress also increases, leading to an increase of the breakup time. Therefore, the total deformation of the dispersed phase, before breakup, increases with increase of volume fraction, resulting in a decrease of the size of the dispersed phase particles. Accordingly, one can expect that in industrial mixers, the particle size of the blends should decrease as the volume fraction increases, if coalescence is suppressed. Experiments were carried out in a Haake batch mixer, using polyethylene/polyamide‐6 blends compatibilized by adding maleic anhydride grafted polyethylene. Particle size decreased up to 20 wt% polyamide‐6, at 100, 150, and 200 RPM, and increased between 20 and 30 wt%. The decrease of the particle size is mainly due to increased deformation of the dispersed phase. The increase of the particle size above 20 wt% is due to coalescence at high fractions.
Transient compositional effects from feeders in a starved flow modular co‐rotating twin‐screw extruder
Authors: Kim Eung Kyu , White James L.
Published: April 2004

A process dynamics model of transient output composition variations in a moduar self‐wiping twin‐screw extruder caused by input disturbances from feeders is developed. The changes of output mass flow rate and weight fraction of additives in the output stream were predicted for various time dependent input modes into a second feeder and other ports part way along the length of the machine.
Continuous microcellular polystyrene foam extrusion with supercritical CO2
Authors: Han Xiangmin , Koelling Kurt W. , Tomasko David L. , Lee L. James
Published: April 2004

The continuous production of polystyrene microcellular foams with supercritical CO2was achieved on a two‐stage single‐screw extruder. Simulations related to the foaming process were accomplished by modeling the phase equilibria with the Sanchez‐Lacombe equation of state and combining the equations of motion, the energy balance, and the Carreau viscosity model to characterize the flow field and pressure distribution in the die. The position of nucleation in the die was determined from the simulation results via a computational fluid dynamics code (FLUENT). Experimental parameters were selected according to the Tgand phase equilibria. The effects of CO2concentration and die pressure are explored. Below the solubility limit, higher CO2concentrations lead to smaller cell size and greater cell density. With an increase of die pressure, the cell size decreases and the cell density increases.
Toughening mechanisms in annealed high density polyethylene under impact
Authors: Ravi S. , Takahashi K.
Published: April 2004

Impact fracture behavior of annealed high density polyethylene (HDPE) has been studied. Charpy impact test results show that annealing increases the total fracture energy of HDPE and also that the increase in fracture energy is mainly due to the increase in the propagation energy with annealing time. Microscopic studies have been carried out to elucidate the origin of the rise in the propagation energy of the annealed HDPE. It is found that as annealing time increases, microscopically, the failure is more ductile with the formation of fibrillar structure. Based on the morphological study, it is proposed that the increased toughness observed in annealed HDPE is due to the occurrence of micro‐voids (or cavities) as the material yields under mode I dynamic tension. The void generation promotes the formation of fibrous structure, which absorbs greater energy than as‐received HDPE.
Effect of blending sequence on the microstructure and properties of PBT/EVA‐g‐MAH/organoclay ternary nanocomposites
Authors: Li Xiucuo , Park Hwan‐Man , Lee Jang‐Oo , Ha Chang‐Sik
Published: April 2004

Ternary nanocomposites based on poly(butylene terephthalate) (PBT), maleic anhydride grafted poly(ethylene‐co‐vinyl acetate) (EVA‐g‐MAH), and organically modified montmorllonite (organoclays) were prepared through four different blending sequences in a Haake rheocord mixer: (1) To blend PBT, EVA‐g‐MAH and organoclays in one step; (2) First to prepare EVA‐g‐MAH/organoclay nanocomposite, then mix it with PBT to get the final nanocomposite; (3) To mix PBT with organoclays first, then the PBT/organoclay nanocomposite with EVA‐g‐MAH. (4) To mix organoclays with the PBT/EVA‐g‐MAH blend. The microstructure of the PBT/EVA‐g‐MAH/organoclay ternary hybrids was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the blending sequence significantly influences the microstructure of PBT/EVA‐g‐MAH/organoclay ternary hybrids and the dispersion behavior of the organoclays in the polymer matrix. Tensile and impact properties of the hybrids were also studied. The results showed that the mixing sequence (2) gives the best tensile and impact strength due to its fine “sea‐island” morphology of PBT/EVA‐g‐MAH blend and good dispersion of the organoclays in the continuous PBT matrix.
Microwave absorbing properties of carbon black/silicone rubber blend
Authors: Kwon Soon Kil , Ahn Joon Mo , Kim Geun Hong , Chun Chang Hwan , Hwang Jun Sik , Lee Jeong Hwan
Published: April 2004

In the frequency range of 2–18 GHz, the microwave absorbing properties of a carbon black/silicone rubber blend were investigated by changing the carbon black content and the thickness. The real part (ε′) and the imaginary part (ε″) of permittivity of the blends were calculated from the S‐parameters measured by a network analyzer. The reflection loss was simulated by using ε′ and ε″. The reflection loss less than −10 dB could be obtained in the frequency range of 9.6ε13.5 GHz from the sample with 10 wt% of carbon black at 1.9 mm of thickness.
Tear strength of ductile polyolefin films
Authors: Chang A. C. , Inge T. , Tau L. , Hiltner A. , Baer E.
Published: April 2004

A reinforced trouser tear test was developed to evaluate the tear resistance of thin ductile films. Tests with blown film of linear low‐density polyethylene blended with up to 30 wt% of a high melt strength polypropylene (hmsPP) demonstrated that the test differentiated among films based on composition and thickness. Increasing the amount of hmsPP in the film decreased the tear resistance. Also, thinner films were less tear‐resistant than thicker films. Stable crack growth occurred with transformation of a crack tip damage zone into a continuous yielded zone at the fractured edge. The tear energy was directly proportional to the width of the yielded zone. Correspondence between the energy to deform the material in the yielded zone and the measured tear energy demonstrated that yielding in the vicinity of the propagating crack provided the resistance to tearing in these films.
Measurement and prediction of LDPE/CO2solution viscosity
Authors: Areerat Surat , Nagata Takefumi , Ohshima Masahiro
Published: April 2004

When CO2is dissolved into a polymer, the viscosity of the polymer is drastically reduced. In this paper, the melt viscosities of low‐density polyethylene (LDPE)/supercritical CO2solutions were measured with a capillary rheometer equipped at a foaming extruder, where CO2was injected into a middle of its barrel and dissolved into the molten LDPE. The viscosity measurements were performed by varying the content of CO2in the range of 0 to 5.0 wt% and temperature in the range of 150°C to 175°C, while monitoring the dissolved CO2concentration on‐line by Near Infrared spectroscopy. Pressures in the capillary tube were maintained higher than an equilibrium saturation pressure so as to prevent foaming in the tube and to realize single‐phase polymer/CO2solutions. By measuring the pressure drop and flow rate of polymer running through the tube, the melt viscosities were calculated. The experimental results indicated that the viscosity of LDPE/CO2solution was reduced to 30% of the neat polymer by dissolving CO2up to 5.0 wt% at temperature 150°C. A mathematical model was proposed to predict viscosity reduction owing to CO2dissolution. The model was developed by combining the Cross‐Carreau model with Doolittle's equation in terms of the free volume concept. With the Sanchez‐Lacombe equation of state and the solubility data measured by a magnetic suspension balance, the free volume fractions of LDPE/CO2solutions were calculated to accommodate the effects of temperature, pressure and CO2content. The developed model can successfully predict the viscosity of LDPE/CO2solutions fromPVTdata of the neat polymer and CO2solubility data.
Wood‐flour‐reinforced polyethylene: Viscoelastic behavior and threaded fasteners
Authors: Farid S. I. , Kortschot M. T. , Spelt J. K.
Published: April 2004

The tensile stress relaxation and flexural creep properties of wood‐fiber‐reinforced low‐density polyethylene (WFRP) were measured at various temperatures and stress levels. Power law relations were used to correlate the data, and time‐temperature superposition was applied to tensile stress relaxation results. Stress relaxation in WFRP was similar to that of LDPE and greater than that in spruce. The clamping force and torque characteristics of self‐threading screws and internally threaded inserts were measured in WFRP, and the viscoelastic model was extended to predict the relaxation in screw clamping force as a function of time. Both screw pullout force and the amount of clamping force relaxation were greater in WFRP than in spruce.
Transparent multiphasic polystyrene/epoxy blends
Authors: Hoppe C. E. , Galante M. J. , Oyanguren P. A. , Williams R. J. J. , Girard‐Reydet E. , Pascault J. P.
Published: April 2004

Blends of polystyrene (PS) with an epoxy monomer (DGEBA) and a tertiary amine (BDMA), were initially miscible at 120°C but phase‐separated at very low conversions in the course of polymerization. Although there was a significant difference between the refractive indices of polystyrene and the DGEBA/BDMA solution, the refractive index of the epoxy network increased in the course of polymerization, attaining a value close to that of PS at complete conversion. A sharp decrease of the light transmittance was observed at the cloud‐point, observed at very low conversions. However, the continuous increase of the refractive index of the epoxy phase with conversion produced an approximate matching of both refractive indices, leading to transparent materials at complete conversion. Morphologies generated by reaction‐induced phase separation depended on the molar mass distribution of polystyrene and its mass fraction in the blend. For a PS with a high value of the mass‐average molar mass (Mw), it was possible to generate a dispersion of PS particles in the epoxy matrix (blends containing 5 wt% PS), phase‐inverted morphologies (blends containing 15 wt% PS) and double‐phase morphologies (blends with 10 wt% PS). Therefore, PS/DGEBA/BDMA blends could be used to obtain transparent epoxy coatings toughened by polystyrene particles or transparent polystyrene parts reinforced by a dispersion of epoxy particles.
A new concept of active temperature control for an injection molding process using infrared radiation heating
Authors: Saito Takushi , Satoh Isao , Kurosaki Yasuo
Published: April 2004

This paper deals with an innovative injection molding process that uses infrared radiation heating for active temperature control of the molded polymer. The feasibility of the proposed technique was investigated through numerical simulation and experimental study. By directly heating the molded polymer with radiation energy, precise and rapid temperature control and a small effect on the cooling duration were expected. Zinc‐selenide and a CO2 laser were used as a transparent mold window and radiation energy source, respectively. In the numerical simulation, temperature distribution both in the molded polymer and the mold wall was evaluated for various molding conditions. The results showed that the heating extent of the molded polymer varied with radiation intensity, radiation absorption coefficient, and melt flow rate. It was also estimated that extension of the cooling duration with the present technique was much shorter than that of a conventional conductive heating technique. In the experimental study, the present technique was applied to actively control the melt temperature and to improve the quality of molded products. As a result, apparent reduction of the residual molecular orientation and considerable improvement of the surface transcription were successfully realized.
Thermoplastic polyurethane–carbon black compounds: Structure, electrical conductivity and sensing of liquids
Authors: Segal E. , Tchoudakov R. , Narkis M. , Siegmann A.
Published: April 2004

Thermoplastic polyurethane (TPU) copolymers are interesting host matrices for the incorporation of conductive carbon black (CB) particles. The two‐phase character of the TPU systems provides an opportunity for the CB particles to distribute nonuniformly within the phases, owing to their different characteristics. Thus, in spite of its highly polar nature, the TPU/CB system percolates at a relatively low CB content. The CB presence affects the TPU two‐phase structure, resulting in a large change of its low temperature loss modulus. CB‐containing extruded filaments produced by a capillary rheometer at various shear rates were studied as sensing materials for different alcohols. All filaments displayed an increase in resistance upon exposure to various alcohols. Filaments exposed to methanol exhibited the highest sensitivity. This behavior was related to the sorption kinetics by the TPU/CB compound, which is affected by the different characteristics of the solvents. The resistance of filaments exposed to ethanol or methanol tended to reversibility during the drying cycle, returning to the initial values. The relatively rapid recovery to the filaments' initial resistance values (for methanol and ethanol) suggests that the structural changes due to solvent sorption mainly occur in the outer skin regions of the extruded filaments, whereas the core region remains essentially intact.
Copolymerization of ethylene with 1‐hexene over metallocene catalyst supported on complex of magnesium chloride with tetrahydrofuran
Authors: Czaja Krystyna , Białek Marzena , Utrata Alicja
Published: April 2004

The study of ethylene/1‐hexene copolymerization with the zirconocene catalyst, bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2)/methylaluminoxane (MAO), anchored on a MgCl2(THF)2 support was carried out. The influence of 1‐hexene concentration in the feed on catalyst productivity and comonomer reactivity as well as other properties was investigated. Additionally, the effect of support modification by the organoaluminum compounds [(MAO, trimethlaluminum (AlMe3), or diethylaluminum chloride (Et2AlCl)] on the behavior of the MgCl2(THF)2/Cp2ZrCl2/MAO catalyst in the copolymerization process and on the properties of the copolymers was explored. Immobilization of the Cp2ZrCl2 compound on the complex magnesium support MgCl2(THF)2 resulted in an effective system for the copolymerization of ethylene with 1‐hexene. The modification of the support as well as the kind of organoaluminum compound used as a modifier influenced the activity of the examined catalyst system. Additionally, the profitable influence of immobilization of the homogeneous catalyst as well as modification of the support applied on the molecular weight and molecular weight distribution of the copolymers was established. Finally, with the successive self‐nucleation/annealing procedure, the copolymers obtained over both homogeneous and heterogeneous metallocene catalysts were heterogeneous with respect to their chemical composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2512–2519, 2004
Ethylene polymerization by bis(salicylaldiminate)nickel(II)/aluminoxane catalysts
Authors: Carlini Carlo , Macinai Alessandro , Masi Francesco , Raspolli Galletti Anna Maria , Santi Roberto , Sbrana Glauco , Sommazzi Anna
Published: April 2004

The homopolymerization of ethylene by using different catalytic systems based on dinitro‐substituted bis(salicylaldiminate)nickel(II) precursors such as bis[3,5‐dinitro‐N(2,6‐diisopropylphenyl)]nickel(II) and bis[3,5‐dinitro‐N(phenyl)]nickel(II) in combination with organoaluminum compounds was investigated. In particular, the catalytic performances were studied as a function of the main reaction parameters, such as temperature, pressure, Al/Ni molar ratio, and duration. Methylaluminoxane resulted in the best co‐catalyst. Activities up to 200 kg polyethylene/(mol Ni × h) to give a linear high‐molecular‐weight polymer were achieved. The influence of the bulkiness of the substituents on the N‐aryl group of the aldimine ligand was also checked; it resulted in a determinant for catalytic activity rather than for polymer characteristics. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2534–2542, 2004
Grzegorz Lapienis and Stanislaw Penczek, "Reaction of oligoalcohols with diepoxides: An easy, one‐pot way to star‐shaped, multibranched polymers. II. poly(ethylene oxide) stars—synthesis and analysis by size exclusion chromatography triple‐detection method," J Polym Sci Part A: Polym Chem (2004) 42(7) 1576–1598
Authors: Lapienis Grzegorz , Penczek Stanislaw
Published: April 2004

The original article to which this Erratum refers was published in
Journal of Polymer Science Part A: Polymer Chemistry (2004) 42(7) 1576–1598

No abstract.
Responses of the olfactory receptor neurons of the corn stalk borer Sesamia nonagrioides to components of the pheromone blend and their inhibition by a trifluoromethyl ketone analogue of the main component
Authors: Quero Carmen , Bau Josep , Guerrero Angel , Renou Michel
Published: April 2004

Two types of olfactory hairs and three types of olfactory receptor neurons (ORN) have been characterized on the antennae of male Sesamia nonagrioides Lef for the first time. Type A sensilla housed a cell which fired large spikes in response to (Z)‐11‐hexadecenyl acetate (Z11‐16:Ac), the major component of the sex pheromone, and a second cell firing smaller spikes in response to (Z)‐11‐hexadecenal (Z11‐16:Ald), a minor component of the pheromone blend. Type B sensilla housed one cell firing large spikes to Z11‐16:Ac and a cell firing smaller spikes to another minor component of the pheromone blend, (Z)‐11‐hexadecenyl alcohol (Z11‐16:OH). No cell responding to dodecyl acetate, another minor component of the natural extract, was found. Fluorinated ketones were tested as inhibitors of the cell responses to pheromone compounds. The fluorinated derivatives tested, (Z)‐11‐hexadecenyl trifluoromethyl ketone (Z11‐16:TFMK), n‐hexadecyl trifluoromethyl ketone (16:TFMK), (Z,E)‐9,11‐tetradecadienyl trifluoromethyl ketone (Z9,E11‐14:TFMK), 3‐octylthio‐1,1,1‐trifluoropropan‐2‐one (OTFP), (Z)‐11‐tetradecenyl trifluoromethyl ketone (Z11‐14:TFMK) and 1,1‐difluoro‐(Z)‐11‐hexadecenyl methyl ketone (Z11‐16:DFMK), had no or only weak excitatory effects. However, the neuron responses to the pheromone compounds were significantly decreased in the presence of a constant stimulation with Z11‐16:TFMK and the effect was reversible. The latencies of the responses to the acetate and aldehyde cells were significantly increased. The effects were not specific, since Z11‐16:TFMK also inhibited the responses of the ORNs of Spodoptera littoralis Boisd. Correspondingly, Z9,E11‐14:TFMK, an analogue of the main component of the pheromone of this latter insect, inhibited responses of S nonagrioides ORNs. Implications of these results on the utilization of Z11‐16:TFMK as a communication disruptant are discussed. Copyright © 2004 Society of Chemical Industry
Decision making in controlling virus yellows of sugar beet in the UK
Authors: Qi Aiming , Dewar Alan M , Harrington Richard
Published: April 2004

Virus yellows is an important disease affecting yield in sugar beet in the UK. Myzus persicae (Sulzer) is the most effective and efficient aphid vector of the three viruses causing the disease: beet yellows virus, beet mild yellowing virus and beet chlorosis virus. Control of virus yellows disease is thus focused on the study and control of this aphid species. UK national surveys of virus yellows began in 1946 and these data helped to formulate disease forecasting schemes to optimise control. Over the years, in addition to improvements in farm hygiene, periodic changes and developments in control of the disease have occurred. To accommodate these important developments, virus yellows forecasting schemes have evolved accordingly. The most recent version has been adapted to take account of the current widespread use of imidacloprid seed treatment. Its application offers potential to optimise the rational use of aphicides such as imidacloprid so as to benefit beet growers and the environment by reducing prophylactic use of seed treatment. Copyright © 2004 Society of Chemical Industry
The interaction of endosulfan with the Collembolan,Proisotoma minuta(Tullberg): toxicity, the effects of sub‐lethal concentrations and metabolism
Authors: Park Eun‐Kee , Lees Edith M
Published: April 2004

An increased level of the Collembolan,Proisotoma minutaTullberg was found in the cotton‐growing areas of New South Wales, Australia. They were regularly exposed to endosulfan, a highly insecticidal compound. Toxicity, sub‐lethal effects and metabolism of endosulfan were studied inP minutathat had been successfully maintained in a plaster of Paris and charcoal mixture substrate with freeze‐dried yeast as a food. The 168‐h LD50values were 0.011, 0.049 and 0.055 mg liter−1for α‐ and β‐endosulfan and endosulfan sulfate, respectively. WhenP minutawere exposed to non‐lethal concentrations of the endosulfans, egg production was inhibited. On recovery from the toxic effects of the endosulfans they resumed production of viable eggs. Conversion of α‐ and β‐endosulfan to endosulfan sulfate was found and the endosulfan sulfate could be further metabolized. The rate of metabolism of α‐endosulfan was greater than that of β‐endosulfan and the product of endosulfan sulfate metabolism was not identified. Copyright © 2004 Society of Chemical Industry