The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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The co-rotating fully intermeshing twin-screw extruder is the primary production unit for compounding of polymer based materials. It also has had a long term presence in processing material in the chemical and food industry and more recently in pharmaceuticals. While this equipment celebrated its 50th anniversary several years ago and might be considered a “mature” technology, it has not experienced a decline in new developments as might be expected, but rather a significant number of advancements continue to evolve. This paper will highlight several significant developments of the past 10 to 15 years. These are the implementation of high torque (power) designs, the use of increased rpm in conjunction with high torque for improved operating flexibility and productivity, and finally a technology breakthrough for feeding difficult to handle low bulk density materials.
This study investigated the effect of surface modification of nanoclays on the compatibility of Maleic Anhydride-grafted polypropylene (PP-g-MA)/poly (ethylene oxide) (PEO) blends. Rheological testing confirmed the network formation of nanaoclays of all types. SEM confirmed the emulsifying role of nanoclays by reducing the PEO domain size. For the case of using dialkyl (C18)-modified nanoclays, mechanical testing showed that the elastic modulus and the toughness were respectively improved by 20% and 55% compared to unfilled samples.
To obtain information on the temperature dependence of the interfacial strength (IFSS) in glass – polypropylene composites a thermomechanical analyser was adapted to enable microbond testing to be carried out in a well controlled temperature environment. Test results obtained by TMA-microbond testing showed excellent comparability with those obtained by normal microbond testing. The of IFSS of glass – polypropylene was measured from -40°C up to 100°C. The IFSS showed a highly significant inverse dependence on testing temperature.
Christelle F. Poquette, Niles G. Stenmark, May 2012
Environmental stress cracking (ESC) resistance has become an essential industrial criterion for engineering thermoplastics, as ESC causes unexpected brittle fracture of ductile amorphous plastics. In the automotive industry, a variety of amorphous plastics are used, which need to be ESC resistant, as they come in contact with various fluids while subjected to mechanical stresses. PC-ABS materials offer a good compromise between processibility, cost and mechanical properties. However, this material is prone to ESC failure.
Daniel Berkowitz Zamora, Shyam Sathyanarayana, Patrick Weiss, Christof Hübner, Jan Diemert, Frank Henning, Peter Elsner, May 2012
Compounding extrusion of Polypropylene-Carbon nanotube composite is presented as a case study with Design of Experiments approach to identify best processing parameters for optimum dispersions and conductivity. Influence of Specific Mechanical Energy input on resulting morphology and volume resistivity of extruded strands are analyzed with statistical viewpoints. Resistances of the melt are measured with an online process monitoring approach and correlated with measurements on extruded strands. This aids process planning, and economization.
The causes of a drastic reduction in the service life of plastic enclosures molded from an acrylonitrilebutadiene- styrene (ABS) resin have been investigated. The mechanism and type of failure have been deduced from a detailed morphological examination of the fracture surface. Various factors responsible for a rapid failure of the enclosure have been identified. Analytical testing such as infrared spectroscopy and differential scanning calorimetry were performed to identify a specific material characteristic responsible for the failure. The results obtained during the evaluation indicated that the failure was due to environmental stress cracking, which occurred as a consequence of the presence of an incompatible chemical and assembly stress. The nature of the chemical agent was found and its effect on the properties of the ABS is discussed.
Evan Mitsoulis, Thanasis Zisis, Mahmoud Ansari, Savvas G. Hatzikiriakos, May 2012
Three major polyethylene (PE) engineering plastics, linear-low-density (LLDPE), low-density (LDPE) and high- density (HDPE) are studied in capillary flow. The purpose is to find experimentally and predict numerically their flow behaviour, namely the pressure drop in flow through tapered dies. This behavior is related to their individual rheological and flow properties. Using a series of capillary dies having different diameters D and length-to-diameter L/D ratios, a full rheological characterization has been carried out, and the experimental data have been fitted with the viscoelastic K-BKZ/PSM model. The branched LDPE has a strong pressure-dependence of viscosity, with a pressure-dependent coefficient ?p. For the linear LLDPE and HDPE melts, the pressure-dependence of viscosity is weak, but slip at the wall is strong and affects their flow behaviour. Thermal effects due to viscous dissipation are included but are rather mild. It is found that the viscoelastic simulations are capable of reproducing the experimental data well, in the whole range of apparent shear rates and L/D ratios.
Calendering is a process for producing plastic sheets of a desired final thickness and appearance. The thickness of the exiting sheet during a calendering operation is uniquely found by the Lubrication Approximation Theory (LAT) and the application of the Swift boundary conditions, which dictate that both the pressure and its axial derivative are zero at detachment. This cannot be used in a 2-D analysis of the process, where the detachment point is the anchor of a free surface, and hence a singular point where both the pressure and the stresses go through numerical oscillations. This difficulty can be circumvented by using the Boundary Element Method (BEM), which uses as primary variables velocities and tractions, and thus avoids pressures and stresses. Then the detachment point is found as the point where the tangential traction becomes zero. Numerical tests undertaken here with the Finite Element Method (FEM) show that the LAT results can be used as a good approximation for the detachment point, which is then fixed. Comparisons with 2-D BEM results show a good agreement for all flow field variables. However, the exact position of the detachment point in a 2-D FEM analysis is still elusive, since for viscous polymer melts the contact angle is not known and should be part of the solution. Some thoughts are given about how to tackle this still unresolved issue, based on double nodes with discontinuous velocities and pressures.
Huiju Liu, Herman Suwardie, Xueyan Zhang, Peng Wang, Costas G. Gogos, May 2012
The miscibility between drug indomethacin and excipient Eudragit® E PO were extensively characterized by rheological and thermal analysis. The evolution of glass transition temperature and activation energy with indomethacin concentration indicates the existence of overall positive deviation which represents anti-plasticization effect. The rheological analysis is in agreement with the thermal analysis, and both methods indicate that the miscibility between them is very good for indomethacin concentrations up to 60~70%.
Johannes Wortberg, Marco Lenzen, Georg Lenze, May 2012
Topic of this article is the result of some investigations which are representing the foundations for quality optimization of highly filled injection-molded parts, represented by the electrical conductivity. In this context the influence of the process conditions on the electric conductivity of high temperature bipolar plates is subject of research. Especially the cavity pressure, the melt temperature and the time dependence of these values became essential.
The injection molding process is widely known as one of the most advanced processes for manufacturing of parts that range from simple commodities to accurate technical parts. Due to the cyclical process the power consumption is highly discontinuous causing distinct peak power. This article describes an alternative local drive concept, which is able to realize a continuous power consumption during the injection molding process. This concept is designed for tasks with a high power demand, for example clamping forces about 13.000 kN.
Pitchaya Naneraksa, Ratanawan Magaraphan, May 2012
Polypropylene blown film containing 1 wt% nanoparticles was fabricated which organoclay and copper nanoparticles were incorporated for barrier and antimicrobial purpose. Effect of copper nanoparticle content (5, 10, 15 and 20 wt% of total nano-fillers) on clarity and mechanical properties of polypropylene nanocomposite film was investigated. Nanocomposite PP films were fabricated via water-quenched blown film extrusion. A sodium neutralized ethylene-methacrylic acid ionomer of 2 phr was used to modify compatibility between polypropylene and nano-fillers.
Lizhi Liu, Teresa P. Karjala, Xuming Chen, Jian Wang, Mehmet Demirors, Selim Bensason, May 2012
The morphological basis of improvements in film haze achieved by blending LDPE into LLDPE was explored with light scattering. Two-dimensional light scattering patterns were analyzed by a novel approach to define a “Morphology Index”. Besides its utility as a numeric descriptor of the superstructure in the continuum from spherulitic to fibrillar morphologies, the Morphology Index was also found to correlate well with the internal haze of films.
The dielectric lifetime and breakdown mechanism of PC/PVDF-HFP systems were studied under constant DC field. The 32 L and 256 L PC/PVDF-HFP systems show two orders of magnitude longer dielectric lifetime compared with blend system of PC/PVDF-HFP. It is attributed that the layered structure can impede the breakdown process by deflecting the fracture propagation pathway. The DC resistivity of PC/PVDF-HFP systems was measured and correlates well with the dielectric lifetime in PC/PVDF-HFP system, which implied that the DC resistivity is also an important factor contributing to the enhancement of dielectric lifetime of the layered films.
Matyam Fereydoon, Seyed H. Tabatabaei, Abdellah Ajji, May 2012
In this study, thermal and rheological properties of polyamide 6 (PA6), poly (m-xylene adipamide) (MXD6) and their commercial nanocomposites (4 wt.% clay) were studied. Dynamic rheological experiments were carried out for both neat resins and corresponding nanocomposites at different temperatures. Rheological measurements were conducted using a strain-controlled rheometer. Crystallinity and thermal transitions of the materials are established via both DSC and XRD techniques. Oxygen transmission rates were also measured and normalized by the films thickness.
Julia Botos, Martin Bastian, Peter Heidemeyer, Karsten Kretschmer, Thomas Hochrein, May 2012
Gas permeation measurements performed on films according to the standard take a long time. We present a method with helium for a quick measurement with measuring times of only a few minutes. This allows an accelerated iterative development of new formulations for films directly at the production line and the monitoring of the barrier properties for quality control. The investigations show a good correlation between the results of the accelerated and standardized tests.
Patrick C. Lee, Laura Dietsche, Joseph Dooley, Sumeet Parashar, May 2012
This study shows how the flow uniformity from a film die can be improved by modifying the geometry of the die using a three dimensional finite element optimization technique. In this study, various optimization strategies were used to optimize the geometry to meet the desired objectives of uniform flow at the die exit and minimal pressure drop. Finite element simulations using the numerically optimized geometry predict a more uniform flow than simulations using the baseline geometry. However, some of the numerically optimized die geometries obtained in this study would be impractical to fabricate. Thus we see the power of CFD-based optimization methods to lead towards potentially better performing options; but we also see the necessity of understanding both the die design technology and fabrication techniques in order to analyze the practicality of the proposed optimized solutions. This knowledge can be used to redirect the optimization towards more practical solutions through the use of geometric constraints.
The advent of new base raw materials composed of recycled post consumer/post industrial plastics combined with organic bio fibers that up to now had no value added/sustainable use, has created a global market for a new classification of materials, Bio Fiber Composites. Fundamentally, these composites reduce the hydrocarbon content, (oil) replaced with natural fillers in the form of organic “renewable.” This family of materials is best suited to replace pure polymers, and drives the green, sustainable shift of achieving a balance of physical and mechanical properties to produce the goods and components needed across the complete product landscape. Any product that is injection molded, extruded, thermoformed, or rotationally molded today, can be replaced with a natural organic filled BioComposites Materials. MCG BioComposites, LLC has been formed to supply this place in the industry. This paper will demonstrate the uses and commercial applications for various biomasses, i.e., corn cob fiber, flax fiber and wheat starch.
The simulation of thermally and flow induced crystallization behavior of semi-crystalline polymers is of great engineering significance in polymer processing like injection, blow molding and extrusion. However, its key technology for practical application remains to be difficult. In the study, the mathematical model of three- dimensional thermally and flow induced crystallization of polymer melts obeying Phan-Thien and Tanner (PTT) constitutive model is established. A penalty finite element/finite difference method is introduced to solve the nonlinear governing equations. The computation stability is improved by using the discrete elastic-viscous split stress (DEVSS) algorithm incorporating the streamline upwind scheme. A modified Schneider’s approach is employed to discriminate the relative roles of the thermal and the flow state on the crystallization phenomenon. Two driving causes for the crystallization of polypropylene in extrusion process including the thermal and the flow state are investigated. Both the crystalline distribution and crystalline size of polypropylene are obtained based on the proposed mathematical model and numerical scheme.
Sheng-Ju Liao, Shihn-Juh Liou, Chih-Jen Chang, May 2012
Mold flow analysis of mobile phone case was used in this study to evaluate the intrinsic characteristics of biomass materials how to influence the parameters of injection mold process and the outward appearance of product. Two materials were selected, one is TPS/(PC/ABS) biomass-based material developed by ITRI, and the other is commercial petrochemical plastic PC/ABS. In addition to evaluate the difference between these two materials in the injection mold process and dimensional stability, carbon emissions during this injection mold process were also calculated. Above results will show advantages and shortcomings of this newly developed TPS/(PC/ABS) biomass-based material.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
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"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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