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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Zhijun Jiang, Shengyong Mo, Yi Yang, Furong Gao, May 2014
Polymer extrusion is an important polymer processing method for turning the raw material into varies of products. Barrel temperature is critical to the end product quality. In this paper, the contradicted property of dual inputs (heating and cooling) has been revealed. For energy-saving, an allocated generalized predictive control (AGPC) is first proposed. The contradicted dual inputs are united as one pseudo manipulated variable, which is obtained and then exclusively allocated to heating or cooling in the framework of GPC. Both the simulation and application to the extrusion temperature process show the effectiveness of the proposed algorithm.
Hui Wang, Huamin Zhou, Lin Hua, Yun Zhang, Dequn Li, May 2014
Underfill process is applied in flip chip encapsulation to prevent interconnection failures caused by the mismatch of CTE between die and substrate. In order to better characterize the capillary flow in underfill process, and otherwise to eliminate the troubles in calculating the capillary force in current underfill simulation methods, i.e., result-based and interface reconstruction, we present a mesoscale underfill simulation method based on three dimensional lattice Boltzmann method. In our method, the improved interparticle-potential model is used to model the fluid-fluid interaction, and Benzi's model is used to model the solid-fluid interaction. A geometric model for underfill simulation is then developed, and allows each surface to have a different wettability by assigning a different mesoscale interaction parameter. For verification purpose, two underfill cases are examined. It has been demonstrated that the proposed method has a good performance in the underfill simulation.
Volker Schöppner, Tobias Herken, Nikolas Fecke, May 2014
Plastics, starting from inexpensive mass-produced articles to technical high-end applications, are being used in ever more areas of life. The main drivers are their flexible product properties and the resultant broad application possibilities. To be able to offer plastic products inexpensively and conserve the environment at the same time, more and more attention is being paid to plastics recycling. Polyethylene terephthalate – in short PET – is of particular significance here because of its frequent application in the film and packaging industry and its special material properties. The recycling of PET, however, can only be carried out a limited number of times because it’s processing necessarily results in both thermal and mechanical stresses on the material. This is the basis for the reactions at molecular level, which result in a shortening of the molecule chains (material degradation) and exert a negative effect on the product properties. The aim of this study is to identify the factors that influence the material degradation of PET in twin-screw extrusion. To do this, various screw configurations and different speed and throughput conditions are examined in a series of experiments. Furthermore, material specimens are removed along the length of the screw in order to evaluate the influence of individual screw sections. By determining the intrinsic viscosity of the specimens, it is possible to measure the mean molecular weight and thus the material damage. Based on the test results, guidelines are drawn up for the compounding of PET so as to ensure as little damage as possible to the material.
Due to environmental and sustainability issues, the request for renewable resources increases. Natural fiber-reinforced injection molded materials are therefore an interesting prospect for the automotive industry. To achieve a broader market launch of this new material in the automotive industry, numerical simulation of this new material is essential. Besides rheological and mechanical properties, the fiber morphology and the fiber orientation are the most important properties for the simulation. To evaluate the simulation results experiments are necessary. The morphology of natural fibers (sisal, hemp and regenerated cellulose fibers) was determined by image analysis of the original fibers and the fibers after the procedures of compounding and injection molding. Therefore the fibers were extracted from the granules and the injection molded components. The size of the fibers was significantly reduced during the compounding process, whereas no further reduction could be observed during the injection molding process. Quantitatively, the same results could be found in simulation based on a mechanistic model. Fiber orientation measurements were done via TeraHertz Spectroscopy to evaluate the simulation of the injection molding process and to be able to predict the mechanical properties of the components.
Batch processes like injection molding are inherently a two-dimensional process with multi-phase dynamics. The transient period from one phase to the next is always difficult to control due to the significant change of process dynamics. In this paper, a new two dimensional method based on mixed integer programming is proposed to improve the performance during the transient period. Switch condition is formulated as constraints of an optimization problem. Simulation results are listed to show the efficiency of the algorithm.
Christian Hopmann, Roman Schoeldgen, Kai Fischer, Markus Hildebrandt, May 2014
Continuous fiber reinforced thermoplastics are increasingly being used for lightweight construction parts due to their relatively short processing times. Yet, a flexible production of high quality thermoplastic composite parts is still limited due to the limited diversity of thermoplastic prepregs available to the market which are essential for most common forming processes. Therefore, a new process technology for the flexible production of lightweight parts has been developed at the Institute of Plastics Processing (IKV) at RWTH Aachen University. The developed Inline-Impregnation technique allows for processing cost-effective semi-finished products and includes the impregnation and forming in a single process. In combination with a cost-saving mold technology, Inline-Impregnation facilitates an economic production of prototypes and modular series as well as larger series production. This paper presents results of the research on the process technology.
This paper presents an approach for a design systematic development of alternative joint geometries used in heavy-duty mechanisms. The focus is on joints with oscillating motion correlated with high loads and small pivoting angle. The development of the design concept is based on the example of a 5-point double toggle clamping unit which is installed in injection molding machines. Based on a systematic analysis of joints, a new concept is developed and optimized load-conformable by numerical methods. It is investigated, which algorithm is adequate to optimize the joint geometry load conformable.
Christoph Burgstaller, Carlo Augusto Puppo Bigarella, Bernhard M. Riedl, Wolfgang Stadlbauer, May 2014
The aim of this work was to investigate the possibilities of compatibilizing immiscible blends of HDPE – PA6 via reactive extrusion. We investigated the influence of the compatibilization on the mechanical and rheological properties, as well as the morphology of the samples was investigated. We found, that it is possible to compatibilize immiscible blends via the in situ production of a compatibilizer from a pre-cursor and a radical generator in the blends. The effectiveness of this method is comparable with the compatibilization via the addition of pre-fabricated, industrially available additives.
Difficult to bond plastics, such as polyolefins and fluoropolymers, are commonly used in various industries for some of the following reasons: the cost of the materials and their inherent chemical and thermal resistance. It can be challenging for manufacturers to find solutions to join these difficult to bond materials together. This paper will provide background information on difficult to bond materials, review techniques for quantifying the surface energy of a plastic, review the latest solutions for surface modification and introduce innovative adhesive solutions to meet the challenges of bonding these specific substrates.
Edward M. Phillips, William Crilley, Dan Yasenchak, May 2014
Product and Applications Development Engineers continually struggle with the task of meeting challenging performance requirements that balance physical properties and processability within even more challenging economic constraints. In this paper, we update the industry with results that will encourage the use of electron beam modification as a means of utilizing materials with desirable physical properties but historically lack melt processability due to their linear structure. It is a continuation of ongoing work with an emphasis on melt phase thermoforming and extrusion blow molding. By inducing long chain branching through high energy electron beam bombardment, dramatic increases in viscosity at low shear are achieved which increase sag time in thermoforming and hang time in blow molding. At higher shear rates, these long chain branched polyolefins exhibit strain hardening which translates into improved material distribution allowing for down gauging. LCB (long chain branched) LLDPE (linear low density polyethylene) is viewed as new polymer altogether as it has not been used as a stand alone polymer in many applications due to its inherently poor melt strength.
Georg P. Holzinger, Reinhard Schiffers, Stefan Moser, Stefan Kruppa, May 2014
The production of technical molded parts requires an extreme high level of efficiency, process- and qualitystability to be competitive in global markets. In manufacturing the isotropy of the internal properties is an important prerequisite for warpage-free moldings. At the same time an accurate impression of the surface and an absolute free orientation of the molecule chains of the polymer are required. Therefore, a cost effective high volume production with consistently high quality requirements can only be guaranteed by a high degree of automation and an optimal process control [1]. It is state of the art to fill the mold cavity velocity-controlled in the injection-phase, and to compensate for shrinkage in a pressure-controlled packing-phase to fill the cavity volumetrically correct to meet quality standards. The properties of the moldings produced depend on the parameters, which are set and modified by the operator of the machine [2]. However, these adjustments are today heavily influenced by the experience of the operator, since an accurate knowledge about the influence of the settings on individual quality features without the knowledge of the details in the process is not possible. Also, the production of plastic moldings is used to process variations which affect the stability of the process and thus the quality of the molded parts. A main problem is under- and overfilling during injection-phase. In this work a method is introduced, which enables an autonomous switch-over, which adjusts the change-over point and adapts the packing pressure based on the condition of the processed resin. Variations in the process and on the material properties are characterized by the flow behavior of the polymer melt, monitored by key ratios and corrected in situ in the same injection-cycle. The result is a significantly increased process- and quality-stability. Frequently interventions by an experienced operator for example, are no longer necessary.
A comb-like copolymer of styrene (St) and ionic liquids monomer (1-vinyl-3-butyl imidazolium tetrafluoroborate) was synthesized by atom transfer radical polymerization (ATRP) with CuCl/HMTETA as a catalyst, using the copolymer of styrene and p-Chloromethylstyrene (p-CMS) as a macroinitiator, structures of these copolymers were characterized by mean of FT-IR, 1HNMR and X-ray photoelectron spectroscopy (XPS). When increasing the mass fraction of p-CMS in the copolymer, it was observed varied performances such as phase morphology, hydrophilicity and electro conductivity, which were analyzed by atomic force microscope (AFM), water contact angle and electrochemical impedance spectroscopy (EIS), respectively.
Zhigao Huang, Binkui Hou, Shubiao Cui, Huamin Zhou, May 2014
For injection molding simulation, the model reconstruction is an obstacle in the application, because the computer-aided design (CAD) systems and computer-aided engineering (CAE) systems are realized as isolated modules. In order to improve the quality and efficiency of simulation, a CAD/CAE integrated wizard design system is developed, which is based on the commercial CAD and CAE systems. In this system, the mold design task can be efficiently completed and the CAE data can be automatically obtained with the support of some certain procedures and the powerful tools.
Patricia I. Dolez, Eric David, Eric Blond, May 2014
Layered-silicate-based nanocomposites offer great potential for improving barrier properties of polymer membranes for applications in packaging, protective clothing, geotechnical and environmental engineering, etc. In this study, organo-modified montmorillonite / linear low density polyethylene (LLDPE) nanocomposite samples with various percentages of nanoclay and maleic anhydride compatibilizer were prepared by twin-screw melt-extrusion followed by compression molding. Barrier properties are characterized through oxygen permeability measured according to ASTM D3985 standard test method. A linear relationship is observed between oxygen transmission rate and nanoclay percentage. Results reveal that both the nanoclay and compatibilizer individually contribute to the LLDPE nanocomposites oxygen permeability.
Prashant Mutyala, Mohammad Meysami, Shuihan Zhu, Costas Tzoganakis, May 2014
The usage of waste tire rubber crumb as a dispersed phase in a thermoplastic matrix has been a topic of study for a long time. Devulcanized rubber (DR) being relatively more similar to virgin rubber is expected to perform better than ground rubber tire crumb (GRT). There have not been many studies carried out on DR like in case of GRT. The present work is an extension of the previous work [1] which evaluated the efficiency of peroxide (PX)/sulphur (S) system to compatibilize devulcanized tire rubber (DRT) and PP. In this work, a similar study has been carried out on devulcanized EPDM (DRE)/PP blends and a comparison has been done with the earlier work. A statistical analysis has been carried out on the key mechanical properties namely tensile strength (TS) and elongation at break (EB). SEM pictures have been taken in an effort to understand the reasons for the mechanical properties obtained. The aim behind this work is to expand the commercial worth of DR in various applications.
This paper presents a custom material model for 3D-CFD-simulations of plastification of polymeric materials in polymer processing, especially in high speed extrusion processes. The new approach enables to differ between solid phase and fluid phase in dependence of temperature. A presupposed melting mechanism is not necessary. Hence it becomes possible to simulate melting in just one single fluid domain. The model and its theoretical background are described in this paper. Trials for a custom extruder - the so-called High Speed S-Truder (HSST) - with solid-melt separation are presented. This alternative extrusion concept uses a special sleeve with hundreds of bores. It surrounds the screw and separates the emerging melt from solid material, which remains in the screw channel. The implementation of the new material model into CFD-simulations is a helpful tool to analyze and improve the complex fluid flow in this process.
Historically phthalates have been used as plasticizers in PVC to provide flexibility over a wide temperature range. In applications where higher flame retardancy is needed along with flexibility, brominated phthalates have been used to meet the requirements. DynaSil™ is a novel flame retardant synergist that has properties of flexibilizing PVC while allowing for the replacement for antimony trioxide (ATO), brominated phthalate plasticizer, and/or ammonium octamolybdate (AOM) in PVC formulations. The results show that by using the DynaSil™, brominated phthalates, ATO and AOM can be replaced without loss of flame retardant properties, sacrificing flexibility, and negatively affecting smoke properties. In addition, DynaSil™ can preserve or improve performance properties such as tensile and elongation while providing a very eco-friendly solution at reduced costs.
The High-Speed-S-Truder with floating screw-sleeve is an alternative extrusion concept with solid-melt-separation. A 35 mm screw conveys the resin into a 60 mm screw sleeve. Inside the sleeve the material is plasticizied and discharged into the outer screw channel of the sleeve through radial bores. Only the solid bed remains inside. The development of a melt pool - and thus a decrease of the plasticizing capacity - is avoided. Due to the lower speed of the screw sleeve molten material is conveyed to a Dynamic Mixing Ring in a gentle manner. Experimental results and theoretical background will be described in this paper.
Jinhai Yang, David Kingsley, Jeffery Wiggins, May 2014
This manuscript studies the reaction extrusion of polyurethanes based on both polytetramethylene ether glycol (C4) and polytrimethylene ether glycol (C3) polyols using a twin screw extruder. Polyurethanes (TPU) with hardness of 70A, 85A and 50D were fabricated. The two polyols showed comparable reaction kinetics with methylene diphenyl 4,4'-diisocyanate (MDI). C3 polyol polyurethanes showed slightly lower tensile stress at the same hardness level. But they showed comparable tear strength. C3 polyol TPUs needed slightly higher hard block to obtain the same hardness.
The fiber orientation distribution in a material sample was analyzed. A micro tomography reconstruction of the sample was used to derive the components of a fabric tensor from an evaluation of the global anisotropy parameter. This parameter proved to be an efficient tool for the analysis of the structure of fiber reinforced composites. The local variations of the degree of anisotropy (ratio of the maximum and minimum eigen values of the fabric tensor) from the shell to the core layers of the sample can be captured and information about the local average fiber orientation angle can be obtained.
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