bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman Spectroscopy as an On-line Technique to Monitor Shear Flow Effect on Partially Miscible Polymer Blends
Authors: Adebayo G. , Koombhongse P. , Cakmak M. 
Published: December 2013

Abstract
The phase behavior of two partially miscible polymer blends in simple shear flow was monitored on-line by Raman spectroscopy and subsequently with optical light microscopy on the resulting extrudate. Emphasis was placed on investigating the phase behavior in two polymer blend systems of high and low shear viscosity as they flow through a custom built flow cell with slit conduit. Shear flows initiated from one- and two-phase temperatures were monitored in the higher viscosity blend system of poly(α-methyl styrene–co-acrylonitrile) (PαMSAN) and poly(methyl methacrylate) (PMMA). For the second lower viscosity blend of poly(styrene–co-acrylonitrile) (PSAN) and PMMA90, shear flow was conducted at one-phase temperature and various shear stresses. These blends exhibit a lower critical solution temperature (LCST). The chosen blend composition used for PαMSAN/PMMA had the widest miscibility window in view of the high viscosity of the neat polymers, while for PSAN/PMMA90 blend, a composition very close to the LCST was investigated for the shear flow effects. We observed that for a blend composition of PαMSAN/PMMA system, at small temperature gap from the quiescent cloud point curve, the morphological effects due to shear heating overrides other effects. For a lower melt viscosity blend composition of PSAN/PMMA90, shear induced demixing initially occurs at low shear rates, shear-induced mixing regime follows with increasing shear flow prior to the onset of shear heating effects that brings the material to two phase region resulting in creation of locally optically observable demixed regions where the temperature rise due to shear heating across the extrudate are at maximum.
The Flow Behavior of Core Material and Breakthrough Phenomenon in Sandwich Injection Molding
Authors: Watanabe D. , Ishiaku U. S. , Nagaoka T. , Tomari K. , Hamada H. 
Published: December 2013

Abstract
The processing variables that control the occurrence of breakthrough phenomenon in sandwich injection molding were investigated. Particular attention was paid to the conditions that would yield an optimum sandwich molded part. The effects of variation of core volume ratio that would yield optimum core shot size, injection speed and the skin/core viscosity ratio were examined. The flow morphology at the various stages of flow was also explored. The study was conducted with a bar-flow mold mounted on a twin-barrel injection machine fitted with a common nozzle. It was noted that the core material flow distance depends on the core cylinder screw metering position (core shot size). At the stage at which the core material completely penetrated through the skin material (breakthrough), four distinct regions of flow could be identified. The flow distance of the core material is controlled by the injection speed of the core material while the injection speed of the skin material is of little significance. In order to increase the flow distance of the core material, it is effective to increase the core material injection speed albeit limited by an optimum value of screw metering position. It was found that the flow distance of the core material was longer when the core material viscosity was lower than that of the skin material but breakthrough occurred much earlier so core volume is limited. Breakthrough failed to occur when the viscosity of the core material was higher than that of the skin material. It was found that optimum core volume and core distribution occurred when skin/core viscosities were intermediate. The morphology of the skin material leading to breakthrough was also analyzed.
Flow Analyses in a Spiral Mandrel Die Assuming Wall Slip
Authors: Higuchi H. , Koyama K. 
Published: December 2013

Abstract
It is often observed in industrial practice that the thickness uniformity of blown film obtained with a given die varies with the type of polymer. We have shown in previous works the importance of the wall slip of polymer melt in the film uniformity. Currently available models of polymer melt flow through spiral mandrel dies neglect the wall slip. The present work considers the slip in flow analyses and predicts the effects of rheological properties on the uniformity; the decreases in melt viscosity and wall slip and the increases in shear thinning and the stress dependence of wall slip reduce the uniformity. The predictions agree well with the experimental results obtained in our previous studies.
Optimization of Sweet Bread Dough Processing Conditions by Twin Screw Extrusion
Authors: Wu J.-Y. , Tzeng L.-S. , Wang I.-C. , Chang C.-H. , Huang P.-H. 
Published: December 2013

Abstract
Effects of material feed rate, water addition amount, screw speed and sets of kneading elements on sweet bread dough handling properties and bread qualities were studied by Response Surface Methodology in twin screw extrusion. Results showed that dough stickiness was significantly affected by water addition amount and screw speed (p < 0.001, R2 = 0.9227). Firmness of bread crumb and spread ratio, which is an index for bread appearance, were both significantly affected by water addition amount, screw speed, and sets of kneading elements (p < 0.001, R2 = 0.8940; p < 0.001, R2 = 0.8884). The optimal conditions for sweet bread dough processing are water addition amount ranging from 45 to 50 %, screw speed ranging from 180 to 280 min−1, with material feed rate and kneading element set fixed at 40 min−1 and ten, respectively.
The Flow Behavior of Core Material and Breakthrough Phenomenon in Sandwich Injection Molding
Authors: Watanabe D. , Ishiaku U. S. , Nagaoka T. , Tomari K. , Hamada H. 
Published: December 2013

Abstract
The processing conditions that exert influence on the occurrence of breakthrough during sandwich injection molding were investigated. A spiral flow mold mounted on a twin-barrel injection machine fitted with a single nozzle was used. The effect of mold cavity thickness and the effects of skin material cylinder temperature on skin material viscosity, melt strength, and drawing ratio were considered. Scanning electron microscopy was used to study the morphology of the skin material at the flow front. It was found that the flow length at core expansion region increased and breakthrough phenomenon was delayed as the thickness of the mold cavity increased. When cylinder temperature is increased, the viscosity is lowered and the flow front of the skin material extends with greater ease when pushed by the core material, thus, a greater core volume can be accommodated. As the flow front progresses, the tendency is that the skin material becomes thinner. Polishing and etching followed by SEM examination of the skin material at the flow front revealed that the skin material is oriented perpendicular to the flow direction and the extent of orientation increases with increasing cylinder temperature. This further supported the observation that the deformation ratio and drawing ratio increased with increasing cylinder temperature.
Bowing Phenomenon in Double Bubble Tubular Film Processing for PA 6
Authors: Takashige M. , Kanai T. , Yamada T. 
Published: December 2013

Abstract
This report is to discuss the bowing phenomenon and the sag elimination tension for biaxial oriented PA 6 film process, which consists of double bubble tubular film process and the thermosetting tentering.
The bowing phenomenon does not occur in the heat set of the triple bubble tubular process. However, there is a serious problem of the bubble stability when the sufficient thermosetting by the tubular process is carried out, so the heat set by the tenter process is required. The bowing phenomenon arises when the annealing is carried out by the tenter method. The bowing distortion becomes large when the annealing temperature is high and film relaxation ratio is large.
It is possible to reduce the bowing distortion when thermosetting is carried out in a two-step tenter process. The shrinkage stress of the stretched film was relaxed in the heat treatment during the second step whose temperature is higher than the first one. A two-step heat treatment was able to decrease the bowing distortion compared with the one-step heat treatment.
When the bowing phenomenon occurred, shrinkage percentage in hot water changes along the cross-direction of a film. The humidity expansion coefficient in the film which increases as the increasing shrinkage percentage in hot water is related to the molecular orientation. The sag also increased with increasing the bowing distortion. The bowing distortion and the sag elimination of tension have proportional connection.
Three Dimensional Analysis of Shape Deformation in Injection Molded Optical Lens
Authors: Young W.-B. 
Published: December 2013

Abstract
The shape deformation of optical pickup lens in injection molding was investigated in this study. It was realized that residual stresses and warpage deformation in injection molding parts were affected by different process conditions such as melt temperature, mold temperature, packing pressure and time. A two dimensional analysis in injection molding only provides information on the thickness shrinkage for optical lens. In order to simulate the surface contour variations, a three-dimensional warpage analysis was conducted in this study using the finite element method. Moldings under different packing pressures and mold temperatures were numerically investigated to study the effects on the residual stresses and deformation of a molded pickup lens. The packing pressure and mold temperature were found to be the dominant factors that affect the shrinkage of lens in the thickness direction, resulting in surface contour deviation.
Thickness Uniformity of Double Bubble Tubular Film Process for Producing Biaxially Oriented PA 6 Film
Authors: Takashige M. , Kanai T. , Yamada T. 
Published: December 2013

Abstract
It is known that while the double bubble tubular film process gives better impact strength and more uniform shrinkage balance than the tenter process, yet it is relatively poor in film thickness uniformity. The film thickness uniformity of the PA 6 produced by the double bubble tubular film process was investigated.
The optimum stretching stress during the double bubble tubular film process exists. The bubble breaks over stress 130 MPa and bubble is unstable below stress 60 MPa. In the optimum condition, which is process temperature 310 °C and stretching ratio 3.2, stretched film uniformity was twice worse than non-stretched film one. The thickness uniformity of the film stretched in the optimum condition was better than that of the film stretched at higher process temperature and at lower stretching ratio. In the observations of the bubble sample through the polarizing plates, deformation pattern showed the equality of deformation. Thickness uniformity of non-stretched film significantly affects the thickness uniformity of biaxially oriented film.
Local stretching ratio, which varies along the film width, influences tensile modulus and tensile strength at break. In order to obtain the uniform physical properties of film, it is important to produce the film with uniform thickness. Film thickness uniformity can be improved when stretching stress is high and bubble stability is good. These factors are influenced by stretching temperature, stretching ratio and air velocity from air ring.
Effects of Sparse Long Chain Branching on the Spinning Stability of LLDPEs
Authors: Bortner M. J. , Doerpinghaus P. J. , Baird D. G. 
Published: December 2013

Abstract
The influence of sparse long chain branching on the onset and propagation of isothermal draw resonance in fiber spinning of polyethylene melts was investigated. Six polyethylene melts were used in this study: three sparsely branched metallocene polyethylenes, a linear low-density metallocene polyethylene, a conventional linear low-density polyethylene, and a conventional low-density polyethylene (LDPE). The sparsely branched metallocene polyethylenes have almost identical shear rheology and molecular weight distributions, but strain harden to different extents under extensional deformation because of slight differences in the amount of sparse long chain branching. Critical draw ratios and the ratios of minimum to maximum diameter were found to be different for each of these polyethylenes. The two linear low-density polyethylenes, which have no long chain branching, had critical draw ratios similar to those of the sparsely branched polyethylenes, but failed (necked to the point of filament breakage) during monofilament extrusion at draw ratios significantly lower than those measured for the sparsely branched polyethylenes. In contrast, the LDPE, which has the highest degree of branching and largest molecular weight distribution, had a much higher critical draw ratio than that obtained for the other five polyethylenes. These results suggest that the degree of extensional strain hardening, arising from differences in long chain branching, has a significant effect on the onset and propagation of draw resonance in isothermal fiber spinning. In the case of LLDPE, broadening the MWD seemed to affect the drawability of LLDPE, but had no effect on the critical draw ratio.
Predicting the Long-term Creep Behavior of Plastics Using the Short-term Creep Test
Authors: Lim S. D. , Rhee J. M. , Nah C. , Lee S.-H. , Lyu M.-Y. 
Published: December 2013

Abstract
The creep performance of plastics is one of the main criteria for a variety of applications which requires a strict dimensional stability, including electrical/electronic parts and various automotive applications. However, obtaining or generating accurate creep data is very difficult for both resin suppliers and product designers because the creep property is time dependent, which means it takes over several weeks or even a year of time span. Hence a faster and more reliable method predicting creep behavior of plastics is needed when designing plastic products that will encounter long-term loading. This work presents an easy method for predicting the long-term creep behavior of plastics using the short-term creep experimental data. The flexural creep experiments of three plastics, ABS (Acrylonitrile butadiene styrene), PC/ABS (PC and ABS alloy) and LFT (Long fiber reinforced thermoplastics), are performed. For a quick and reliable prediction of long-term creep behavior of plastics, time regional power-law model and time-stress modulus are introduced. To analyze the reliability and validity of the proposed method, the creep analyses based on the proposed method are performed. The comparison between the FEA results and the creep tests has shown that the new method can track both primary and secondary creep behavior over a long time. The creep analyses have been carried out by commercial FE Code.
On-line Visualization of PS/PP Melting Mechanisms in a Co-rotating Twin Screw Extruder
Authors: Chen H. , Sundararaj U. , Nandakumar K. , Wetzel M. D. 
Published: December 2013

Abstract
The melting and deformation mechanisms of polystyrene (PS) and polypropylene (PP) blends were investigated through on-line visualization of the co-rotating twin-screw extrusion process. Two compositions, PP/PS (80:20) and PS/PP (80: 20) were chosen as the model systems for this study. A sliding barrel technique was used to realize the on-line visualization using a glass window in the barrel. The axial temperature and pressure profiles along the screw channel were measured using the same sliding technique. It was found that in the PP/PS (80:20) blend, in which PP was the major phase, there was a combined melting of PS and PP, whereas in the PS/PP (80:20) blend, in which PS was the major phase, there was initial melting of PS alone and then combined melting of PS and PP. In the partially filled region, heat conduction from the hot barrel was the major source for heating polymer pellets under the conditions studied here; while in the fully filled region, viscous energy dissipation (VED) generated most of the heat for melting of polymer pellets. The pressure profiles along the extrusion channel gave us insight into the melting process for the two blends. It was found that if there was some molten polymer in the fully filled region, the overall melting process was accelerated due to heating from viscous dissipation.
Influence of Filler Particle Geometry on Die Swell
Authors: Stabik J. 
Published: December 2013

Abstract
Die swell reduction is observed as a result of filler incorporation into polymer matrix. The degree of die swell decrease depends among others on filler particles geometry. In the paper results of experimental investigations concerning relations between particle geometry and die swell are presented for polyethylene and polystyrene filled with a number of commercial fillers. Approximation functions describing these relations were developed. This enabled simultaneous analysis of the influence of different particle geometry properties on die swell. Good fitting of approximation models to experimental results was achieved. Similar behavior of polyethylene and polystyrene compounds was observed. Shape ratio exhibited the most pronounced influence on die swell. The higher is the shape ratio of filler particles the smaller is die swell. Much less significant influence showed specific surface and mean particle diameter.
Determination of the Residence Time Distribution in Twin Screw Extruders via Free Radical Modification of PE
Authors: RazaviAghjeh M. K. , Nazockdast H. , Assempour H. 
Published: December 2013

Abstract
The main objective of the present work was to introduce an inline method for measuring the residence time distribution (RTD) of twin screw extruders on the basis of information obtained from the melt free radical modification of polyethylene in a modular intermeshing co-rotating twin screw extruder. The trend of increasing rate of the extruder total torque resulted from replacing the neat polyethylene feed by a mixture of polyethylene and reactants which are chemically capable of creating chainbranching and/or crosslinking reactions was considered as the main information source for evaluating the RTD of the extruder. The RTD results were compared with those obtained from the tracer pulse input method, and good agreement was found. It was also demonstrated that, the present in-line RTD measuring technique has reliability of following the effect of feeding rate, screw speed and reactant concentration on the RTD of the twin screw extruders. It was found that, increasing the feeding rate results in decreasing the minimum residence time, and results in a narrower RTD. At constant feeding rate increasing the screw speed decreased the minimum residence time and broadened the RTD. The results also showed that, reactant concentration and variation of the viscosity along the screw have not appreciable effect on the twin screw extruders RTD.
Reactive Batch Mixing for Improved Silica-Silane Coupling
Authors: Kim K.-J. , Vanderkooi J. 
Published: December 2013

Abstract
Moisture (55 wt%) treated silica compounds, bis(triethoxysilylpropyl)disulfide(TESPD)/silica/carbon black/S-SBR was processed in a batch mixer and they were investigated with respect to the alcohol residue level in silane, the processability, the vulcanization characteristics, and the mechanical properties.
Treatment of moisture on the TESPD/silica/carbon black/S-SBR compound showed a lower alcohol level than untreated material. The alcohol level was low at high drop temperatures. The probe temperatures of the moisture treated compound were lower than the drop temperature, while that of the untreated compound was higher than the drop one. The vulcanization properties of the compounds were changed by treatment of moisture and this improved the mechanical properties of the compounds.
The treatment of moisture on silica surface increased the hydrolysis reaction of the alkoxy silane and the hydrolyzed silane improved the coupling reaction with the hydroxyl group on silica surface during reactive batch processing. It also reduced the rate of temperature rise during batch processing due to the latent heat of the moisture and the endothermic reaction between silica and silane. At the vulcanization stage, it seemed to further increase the coupling reaction between silica and silane.
The steric hindrance theory of an alkoxy silane has to be reconsidered with a large amount of moisture treated silica/TESPD/CB/S-SBR compound system.
Laser Sintering of High Temperature Resistant Polymers with Carbon Black Additives
Authors: Wagner T. , Höfer T. , Knies S. , Eyerer P. 
Published: December 2013

Abstract
Selective laser sintering (SLS) experiments with polyetherketone (PEK) and polyetheretherketone (PEEK) powders are described. The absorption behaviour of the polymer powders has been investigated with respect to the content of carbon black as an IR-absorber in the range from 0.03 to 0.1 wt.%. Laser sintering process studies have been carried out at room temperature using a Q-switched Nd:YAG laser system. The sintering depths of single layer substrates have been determined according to the process parameters, such as laser power, scanning speed and hatch distance. These process parameters have been optimised with the goal of achieving good structural integrity of the substrate. The influence of melt viscosity has been determined by comparing PEEK powders of low and standard melt viscosity. Scanning electron micrographs show the morphology of the original polymer powders and the laser sintered specimens. On the basis of the experimental results a qualitative SLS mechanism is proposed to describe the energy transfer from the carbon black particles to the surrounding polymer powder.
Non-linear Viscoelastic Behavior of PVC Plastisol
Authors: Nakajima N. , Harrell E. R. 
Published: December 2013

Abstract
Rheology of PVC plastisol is usually conducted with steady state flow. It is inadequate, because plastisol is viscoelastic, so that deformational experiment is also required. In the viscoelastic measurements, when either frequency or amplitude is increased, dynamic viscosity decreases first (pseudo-plastic), reaching a minimum and then, increases (dilatant). It is because the shear rate during the oscillation is a product of frequency and amplitude. The pseudo-plastic behavior is explained with stress-induced phase separation into an immobilized layer of packed particles and mobile phase of reduced particle concentration. The viscosity minimum corresponds to the yield point of the immobilized layer. The yielding obeys Coulomb's criterion. After yielding the immobilized layer dilates with the further increase of shear rate. Two different modes of fracture are observed; one without yielding occurs at rather low shear stress, slightly higher than the cohesive strength of the immobilized layer. After yielding and dilation, the fracture occurs when shear stress becomes higher than normal stress. Before yielding the deformation of the immobilized layer is very small and accompanied with small fraction of particles moving over the neighboring particles. After yielding, deformation involves entire particles of the immobilized layer.
Simultaneous Biaxial Stretching of PP Resins of Varying Tacticity
Authors: Capt L. , Rettenberger S. , Münstedt H. , Kamal M. R. 
Published: December 2013

Abstract
The melting and simultaneous biaxial stretching behavior of three Ziegler-Natta isotactic polypropylene resins of varying isotacticity was studied. DSC melting experiments showed that the crystallinity and melt stability of the crystalline phase depend strongly on tacticity and on the degree of undermelting, ΔT = Tm – T, where Tm is the melting temperature. The level of biaxial yield stress depends on the fraction of residual “unmolten” crystallinity and the crystallite size. For specimens with same thermal history, the post-yield deformation shows strong dependence on the degree of undermelting, ΔT. The deformation homogeneity and the resulting film thickness may be related to the thermal mobility of the chains and the tie chain and entanglement densities.