bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wide-Angle X-Ray, Densitometric and Microscopical Studies on Injection Molded Polypropylene Disks
Authors: Zipper P. , Jánosi A. , Wrentschur E. , Geymayer W. , Ingolic E. , Friesenbichler W. , Eigl F. 
Published: December 2013

Abstract
Circular disks (280 mm diameter, 2 mm thickness) were injection molded from two grades of isotactic polypropylene under systematic variation of processing parameters (melt temperature, mold temperature, flow rate, packing pressure, and packing time) according to a two-level fractional factorial design. The disks showed ring-shaped zones (“halos”) of enhanced turbidity. The wide-angle X-ray scattering of the disks was measured as a function of the distance from the gate at 13 positions along the radius, using a diffractometer and reflection geometry. These measurements yielded radial profiles of the orientation of α-PP and of the distribution of β-PP crystallites. Both kinds of profiles revealed clear correlations with the polymer grade and with the melt and/or mold temperature. Radial profiles of optical turbidity of the disks were obtained by means of a microdensitometer. Pronounced maxima of turbidity were found to coincide with the maxima observed in the radial distribution of β-PP. An analysis of variance (ANOVA) of the experiments showed that the mass temperature has the greatest influence on the radial distances of the maxima of turbidity. Increasing mass temperature led to decreasing radial distances of the turbidity maxima, whereas the mold temperature as well as the flow rate only had a small influence on the radial positions of the turbidity maxima. The investigation of cross-sections, which were taken from some disks at selected distances from gate, by means of optical microscopy using polarized light revealed significant changes in the morphology with increasing distance from gate, e.g., changes in the size and distribution of β-PP spherulites.
Shrinkage Prediction for Slowly-Crystallizing Thermoplastic Polymers in Injection Molding
Authors: Han S. , Wang K. K. 
Published: December 2013

Abstract
The prediction of shrinkage and warpage of crystalline polymers is quite difficult. This is because of the complications of the crystallization process and associated material property changes. In typical injection molding of semi-crystalline polymers, it is difficult to calculate crystallinity accurately because of its complicated dependence on temperature, time and stress. In the case of slowly-crystallizing polymers, typically the crystallinity of the polymer remains small during the process. In this case, therefore, the importance of accurate calculation of crystallinity is decreased. The difficulty in this case is the measurement of material properties under variable crystallinity because of the possible crystallization during measurement. In the present study, methods have been developed to obtain material properties which include the effect of crystallinity. The material properties measured include viscosity, thermal conductivity, heat capacity, PvT relation and crystallization kinetics.
Injection-molding experiments have been conducted to measure the shrinkage of a part using a slowly-crystallizing polymer. Shrinkage has been measured by comparing the mold cavity dimension and the dimension of the molded sample. The polymer used in this study is PET (polyethylene terephthalate).
A simulation program has been developed to analyze the injection-molding process. This program is based on quiescent crystallization kinetics. The predicted shrinkage and measured shrinkage are found to agree reasonably well.
The Optimized Quasi-Planar Approximation for Predicting Fiber Orientation in Injection-Molded Composites1
Authors: Ver Weyst B. E. , Tucker C. L. , Foss P. H. 
Published: December 2013

Abstract
Fiber filled injection-molded plastic parts contain complex fiber orientation patterns. This fiber orientation state affects material properties, including both elastic modulus and strength, and the calculation of shrinkage and warpage. Several models are available for predicting fiber orientation, which are based on the theory of Folgar and Tucker [1]. A particular simplification of these models, here called the quasi-planar (QP) approximation, was introduced by Gupta and Wang [2]. Here we develop a substantially improved version of that model, which we call the optimized quasi-planar (OQP) approximation. The OQP approximation is formed by optimizing the QP approximation against a more general fiber orientation model. Details of the current and improved models are discussed, and the typical behavior of the old and new models is explored. In addition, simulations are performed using C-MOLD, a commercial software package that implements the QP approximation, to determine the final fiber orientation state in an end-gated strip. The resulting fiber orientation data is then used to predict the elastic modulus as a function of position, and both predictions are compared to available experimental data for fiber orientation and elastic modulus. The results show that the OQP approximation improves the fiber orientation prediction and the subsequent elastic modulus prediction compared to the QP model, though the OQP approximation is still less accurate than the full three-dimensional model.
Physically-Based Adaptive Control of Cavity Pressure in Injection Molding: Filling Phase
Authors: Rafizadeh M. , Patterson W. I. , Kamal M. R. 
Published: December 2013

Abstract
Cavity pressure plays an important role in determining the quality of injection molded articles. The non-linear and time-varying nature of the process causes difficulties in implementing efficient control systems, which usually employ linear, time-invariant design strategies. Conversely, advanced control methods, such as self-tuning control, do not provide physical information about the process. A physically-based adaptive controller has been developed for cavity pressure control during the filling phase. Different control algorithms, employing different tuning criteria, were implemented on a microcomputer to control the cavity pressure. Experimental results indicate that this control yields accurate results for the injection molding of polyethylene. The results also show that this method, using the IMC algorithm, is superior to the classical optimal controller tuning approach.
In-Mould Shrinkage Measurements of PS Samples with Strain Gages
Authors: Pantani R. , Jansen K. M. B. , Titomanlio G. 
Published: December 2013

Abstract
The problem of shrinkage in injection moulding has been studied by means of a new technique based on strain gages placed on mould surface before injection. The local shrinkage development from the moment it starts inside the mould to soon after ejection can be followed by means of this method.
With reference to a simple rectangular cavity, the effects of different holding pressures, of geometrical constraints placed inside the mould, of position in the cavity and of total cavity length on local shrinkage of injected PS samples are analysed. Shrinkage inside the mould is, indeed, registered: it starts later if higher holding pressures are applied; furthermore, any factor which produces an enhancement of shrinkage evolution before complete solidification gives rise to a corresponding increase of final shrinkage.
Melt Flow Properties of LDPE/HDPE Blends in Capillary Extrusion
Authors: Liang J. Z. , Li R. K. Y. , Tjong S. C. 
Published: December 2013

Abstract
The melt flow properties of LDPE/HDPE blends in capillary extrusion have been investigated. It is found that the End pressure losses (ΔPend) increase as a form of non-linear function with increasing the wall shear stress (τw) and the ΔPend value of the sample is the minimum at the weight percentage content of HDPE (ΦHD) being 50% when the τw is fixed. The blend melt flow basically obeys the power law and the sensitivity of the melt viscosity (ηw) on the wall shear rate (γw) is weakened with increasing the ϕHD. Synergistic effect is obvious for the blend melts under experimental conditions. When the τw is 42.5KPa, the ηw value achieves the maximum at the ϕHD = 20%. In addition, the relationship between the ηw and the test temperature approximately accords with the Arrhenius equation as the τw is fixed.
Rheological Behaviour of LLDPE/LDPE Blends under Elongational Deformation
Authors: Micic P. , Bhattacharya S. N. , Field G. 
Published: December 2013

Abstract
The effect of temperature on the rheological response under elongation of two low density polyethylenes (LDPE 1 and LDPE 2), linear low density polyethylene (LLDPE) and their blends of different compositions was observed by using a constant strain rate elongational rheometer.
In addition, blends were tested in the oscillatory shear test, and the data measured at 160, 190, and 230°C indicate the larger level of intermolecular interactions in a blend than in the pure polymers.
Elongational viscosity measured at temperatures of 140, 150, 170 and 180°C revealed a much greater sensitivity for LLDPE (greater strain hardening with increasing temperature) to changing tenperature than is observed for LDPE.
This observatuion, coupled with the effect of melt morphology on elongational rheology, has been used to explain the synergism in elongational viscosity exhibited by LDP-E-rich blends.
Temperature Measuring in Plastics Processing with Infrared Radiation Thermometers
Authors: Obendrauf W. , Langecker G. R. , Friesenbichler W. 
Published: December 2013

Abstract
In many areas of plastics processing the temperature is a decisive process control parameter. Infrared sensors that detect the heat radiation from molten plastic have a response time in the range of milliseconds. Thus in many processes they offer the only possibility to measure time dependent temperatures with high accuracy.
Melt Grafting of Glycidyl Methacrylate onto Polyethylene
Authors: Hojabr S. , Baker W. E. , Russell K. E. , McLellan P. J. , Huneault M. A. 
Published: December 2013

Abstract
The melt grafting of Glycidyl Methacrylate (GMA) onto Polyethylene in the presence of free radical initiators was conducted in a co-rotating twin screw extruder. Reaction kinetic parameters for the overall grafting and homopolymerization reactions were estimated in a batch melt mixer. Residence time distribution (RTD) in the extruder was determined and mean residence time and Peclet number (Pe) were estimated for different sets of reaction conditions.
A twin screw simulation program was used to predict the flow characteristics along the length of the extruder. A modular reactor model consisting of plug flow and “axial dispersion” reactor cells was constructed and with the kinetic and transport information and the actual melt temperatures, the overall GMA conversion was predicted. In most cases the predicted conversion agreed well with experimentally determined values.
Sensitivity of In-line Rheometry for Extrusion of Mg(OH)2 filled LDPE Compounds
Authors: Coates P. D. , Rose R. M. , Woodhead M. , Kelly A. L. 
Published: December 2013

Abstract
In-process and off-line rheometry studies are reported for compounds based on Mg(OH)2 filled low density polyethylene, some of which were first subjected to a range of strain histories in typical compounding operations. In the study reported here, the compounds were processed using an instrumented, computer monitored single screw extruder in the IRC laboratories, fitted with in line rheometers (ILR). In initial experiments a four sensor ILR slit die was used for the in-process shear rheometry, and a Rosand RH7 twin bore capillary rheometer for off-line shear and entry pressure measurements. Off line and in-line results are compared, showing good agreement for shear. Estimates have been obtained for the sensitivity to filler loading of the off line rheometer (shear flow and entry pressure measurements), and the 4 sensor ILR (shear flow measurements), which indicate that the ILR offers similar resolution of filler level to the off line rheometer at the higher loadings, although the ILR appears to have much lower sensitivity at higher shear rates at lower loadings, an effect which appears to be related to processing effects on the rheology of the compound rather than the measurement ability of the ILR. The ILR was also able to discriminate between samples with differing processing histories. Results from a six-sensor ILR die have shown good agreement in shear flow measurements, and have added the ability to measure entry pressures, which are compared with off-line measurements.
Finite Element Analysis of Mixing in Partially Filled Twin Blade Internal Mixers
Authors: Nassehi V. , Ghoreishy M. H. R. 
Published: December 2013

Abstract
Twin blade internal mixers are the main devices used in rubber processing industry to mix natural and synthetic rubbers with carbon black and other compounding ingredients. To facilitate mixing, these internal mixers are always partially filled. Consequently, the flow regime that becomes established inside the mixer is a multiple random free surface flow with moving external boundaries. The stress field associated with this flow regime is usually very uneven. In addition, the flow stream is continuously divided and rejoined by the action of the counter rotating blades. The combination of these complex effects results in the break down, dispersion and distribution of carbon black agglomerates within the rubber matrix. The efficiency of the entire process mainly depends on the geometry of the mixer blades and the operating conditions. Predictive computer modelling offers a very convenient method for the quantitative analysis of mixing process and can be used to design more efficient internal mixers. However, the successful modelling of a complex process such as rubber mixing requires the development and use of sophisticated mathematical algorithms that can take into account its main characteristics. In this respect, a major difficulty is the imposition of the transient boundary conditions in a continuously varying flow domain. In the present paper we describe a robust method which can very effectively resolve this problem. This method is based on the combination of Lagrangian and Eulerian approaches for the modelling of moving boundary flows. We have used this scheme to simulate flow and mixing in the cross-sectional plane of the blades of a tangential rotor internal mixer.
Use of Dye Containing Polymeric Microcapsules for Determining Shear Stresses
Authors: Clark D. C. , Baker W. E. , Condo A. C. , Kosowski B. M. 
Published: December 2013

Abstract
This paper evaluates a method of measuring shear stress, in-situ, in polymer flows. The rupture response of two different dye containing polymeric microcapsules, CM511 and CM567, is examined in both an internal batch mixer and a lab scale single screw extruder (SSE), using ultraviolet/visible spectrophotometry (UV/VIS), colorimetric analysis (CA) and optical microscopy (OM). It is observed that both particles rupture over a wide range of shear stresses and times. In particular, both CM511 and CM567 begin to rupture at ∼ 100 kPa, while complete rupture is only detected for the CM567 at average stress levels greater than or equal to ∼ 230 kPa. Complete rupture for the CM511 is not observed over the average shear stress range investigated. The microcapsules further indicate the change in the melting mechanism in a SSE when the processing conditions are changed.
Impregnating Flow of a Rheokinetic Liquid
Authors: Malkin A. Ya. , Kuznetsov V. V. 
Published: December 2013

Abstract
A problem of penetration of a viscous liquid into a porous medium with simultaneous squeezing along the surface of this medium is formulated and discussed. The movement of a liquid is initiated by compressing a viscous drop positioned between the upper plate and the porous medium. The system of equations determining the changing of pressure and evolution of an impregnation front was formulated and discussed in dimensionless variables. Typical solutions were obtained for different sets of characteristic parameters including the case of an anisotropic porous medium. Varying the determining parameters leads to different relationships between impregnation and surface squeezing.
It was proven that the formulation of the problem under discussion and solutions obtained in dimensionless form are valid for a “rheokinetic” liquid (viscosity changing due to chemical reactions during flow), if an isothermal situation is considered. However flow of a rheokinetic liquid ceases due to unlimited growth of its viscosity and necessity to increase pressure if we want to maintain the preset velocity of the upper pressing plate.
Utilization of Recycled Crumb Rubber as a Compounding Tool
Authors: Kim J. K. 
Published: December 2013

Abstract
The disposal of used automobile tires has become a major environmental problem, and although there are obvious environmental reasons for recycling waste tires, to date it has not taken place because it is not cost-effective.
The aim of this study was to find a more effective method of recycling used automobile tires. This was done by comparing the methods of using vulcanized crumb rubber as a filler, and investigation of the effect of surface treatment with microscopic examination of the fracture morphology of the filled crumb rubber elastomers.
The experimental results indicate that crumb rubber filler end-product properties were enhanced by the chlorination of crumb rubber, and by developing a crumb rubber incorporation method. We found that much improvement of the mechanical performance of the crumb rubber filled elastomer compounds could be achieved by developing a better crumb rubber incorporation technique.
Modeling of Segmented Polyurethane Drying Process
Authors: Abraham G. A. , Cuadrado T. R. 
Published: December 2013

Abstract
Biomedical segmented polyurethanes (SPU) are frequently processed by solution-casting techniques in order to obtain multilayerfilms. For processing parameters setup empirical criteria is currently applied. However, the selected conditions can strongly affect the physico-chemical properties of the finished articles and they must be accurately established. In order to describe the SPU coating formation, balances of heat, mass and momentum transfer must be considered.
To study the drying process, two new medical-grade SPU solutions commercially available, BiospanTM and Chronoflex ARTM, were dried at different temperatures. Desorption curves and drying rate, both as a function of temperature, were obtained from experimental data. The mathematical model to describe this process take into account the heat and mass transfer and film shrinkage along the whole drying step. The diffusion coefficients and the control mechanism were determined from the best experimental data fitting.
To obtain the solvent concentration profile, residual solvent and film, thickness at any time, heat and mass transfer balances were numerically solved using an explicit finite-difference method. The formulations showed different behavior. For Biospan drying, performed in the range from 5°C to 8°C, a two-stage process was observed. The first one controlled by mass transfer in the gas phase and the second one with mix control. When 4°C drying temperature was applied, a mix control was found along the whole process. This change could be attributed to the acrylic additive present in the SPU matrix, which has a glass transition temperature value in the range of the process temperature. Chronoflex samples showed a two-stage process in all cases and lower diffusion coefficients than Biospan samples.
Simulation of Reactive Liquid Composite Molding
Authors: Wu C.-H. , Chiu H.-T. , Lee L. J. , Nakamura S. 
Published: December 2013

Abstract
The control-volume finite element method (CVFEM) has been used widely to simulate the mold filling process in polymer processing because it is more user friendly and more robust than the conventional finite element or finite difference methods. However, using lower order interpolation functions in CVFEM may result in significant numerical errors. This is especially true for convection–diffusion problems with a changeable source term as in reactive liquid composite molding (LCM). In this study, an Eulerian–Lagrangian approach is proposed where an Eulerian coordinate system is used to solve the velocity field, while the chemical species balance and the energy balance are based on a Lagrangian coordinate system. This approach is used to simulate the non-isothermal LCM process.
Structure and Properties of Injection Moldings of β-Crystal Nucleator-added PP
Authors: Fujiyama M. 
Published: December 2013

Abstract
Aiming at a synergism of improvements of impact strength of polypropylene by the addition of β-crystal nucleator and of its rigidity by the filling of particulate, the addition of the nucleator to particulate-filled polypropylenes has been studied. 0 to 3000 ppm of γ-quinacridone (GQ) which is a β-crystal nucleator was added to homo isotactic polypropylenes (PP) filled with 0 to 30 wt-% of talc (TC) which shows an α-crystal nucleating effect, of mica (MC), or of glass flake (GF), last two of which show β-crystal nucleating effects. Flexural and Izod impact test specimens were injection-molded from the PPs under constant molding conditions and the structure and properties have been investigated. The β-crystal content is reduced by the filling of particulates. The degree of the reduction is in the order of TC >MC >GF, which agrees with that of the crystallization temperature. The flexural modulus decreases slightly with increasing GQ content and increases with increases in particulate contents. The increase is in the order of MC > TC > GF, which agrees with that of the aspect ratio. The enhancing effect of the Izod impact strength by the addition of GQ decreases with increasing particulate contents and diminishes at contents above 10 wt-%. Particulates deteriorate the enhanced impact strength of β-PP. Thus the expected synergism could not be obtained enough.
A method for extracting high‐quality RNA from diverse plants for next‐generation sequencing and gene expression analyses
Authors: Yockteng Roxana , Almeida Ana M. R. , Yee Stephen , Andre Thiago , Hill Colin , Specht Chelsea D. 
Published: December 2013

• Premise of the study: To study gene expression in plants, high‐quality RNA must be extracted in quantities sufficient for subsequent cDNA library construction. Field‐based collections are often limited in quantity and quality of tissue and are typically preserved in RNAlater. Obtaining sufficient and high‐quality yield from variously preserved samples is essential to studies of comparative biology. We present a protocol for the extraction of high‐quality RNA from even the most recalcitrant plant tissues.• Methods and Results: Tissues from mosses, cycads, and angiosperm floral organs and leaves were preserved in RNAlater or frozen fresh at −80°C. Extractions were performed and quality was measured for yield and purity.• Conclusions: This protocol results in the extraction of high‐quality RNA from a variety of plant tissues representing vascular and nonvascular plants. RNA was used for cDNA synthesis to generate libraries for next‐generation sequencing and for expression studies using quantitative PCR (qPCR) and semiquantitative reverse transcription PCR (RT‐PCR).
On the Theorem of the Primitive Element with Applications to the Representation Theory of Associative and Lie Algebras
Authors: Cagliero Leandro , Szechtman Fernando 
Published: December 2013

AbstractWe describe all finite dimensional uniserial representations of a commutative associative (resp. abelian Lie) algebra over a perfect (resp. sufficiently large perfect) field. In the Lie case the size of the field depends on the answer to following question, considered and solved in this paper. LetK/Fbe a finite separable field extension and letx, y∊K. When isF[x,y] =F[αx + βy] for some nonzero elementsα, β∊F?