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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Flexible Porous Polyimide Film for Ultra Low-k FPC
Ultralow-k (dielectric constant) films are promising substrates for the next generation of flexible print cables. Recently, we developed a short-cycle process that uses high-pressure CO2 and CO2-tertiary amine zwitterions in a polyimide precursor solution to create 1-3 µm pores with a total porosity greater than 70%. Here, we report a scaled-up process to obtain 10-fold larger ultralow-k porous polyimide films. This process requires a high-intensity UV lamp, a thick quartz window and a hydraulically movable sealing plate to produce 70 × 150 mm2 films, which is the minimum size that is required for the transmission of high-speed data.
Modeling of the Droplet Morphology Evolution in Polymer Blends under Shear by the Pseudo-Potential Lattice Boltzmann Method
In this work, a novel modeling strategy is proposed to simulate the morphology evolution of polymer blends by the inter-particle-potential lattice Boltzmann method. In this model, the binary components of the polymer blends are tracked by two sets of density distribution functions governed by lattice Boltzmann equation. The model is verified by computing the droplet behavior of deformation, breakup and coalescence under shear, and the results are found in good agreement with the theoretical and experimental observations.
Dimension-Dependent Long-Term Properties of Injection Molded Micro Parts
A variety of polymer parts used in microsystems technology is produced by injection molding. For dimensioning and design of these products, both the material properties and their changes during the life cycle have to be taken into account. Due to the smaller dimensions the process and cooling conditions lead to modified material properties, e. g. stiffness. Aging in polymers is affected by process-induced part properties and takes place primarily on the surface layer. Consequently, parts with decreasing dimensions should reveal a modified aging behavior and size-dependent changes in mechanical properties. Within this article the effect of dimension-dependent aging is investigated using differently scaled tensile bars which were aged under varied conditions. The results indicate that a decreasing part size leads to higher physical and chemical aging effects in polymer parts. However, these changes affect the mechanical properties less than expected.
Effects of a Mass Finishing Process on Parts Produced from Ultem*9085 by Fused Deposition Modeling
Parts produced by Fused Deposition Modeling (FDM) tend to have rough and undulating surfaces with staircase effects on rounded and slanting areas of the part. This is due to the characteristics of the process. In many fields of application, high demands are made on the optical quality of the part. An improvement in the surface quality of FDM parts made of Ultem*9085 can be achieved through post-treatment with a mass finishing process. In this paper, FDM specimens are post-treated in a disk finishing unit. Influences of the mass finishing process are analyzed with regard to the dependence of surface quality on the various process parameters and on the finishing medium, grinding time and grinding speed. The finishing efficiency depends on the finishing media and decreases for lower finishing time. For all media a lower disk velocity results a smaller grinding effect, but there are clearly differences between the finishing media. The paper also discusses effects of the grinding process on the mechanical properties of the parts. Especially small part geometries and parts build in z-direction tend to break during the finishing process.
Energy-Saving Based Allocated Generalized Predictive Control (AGPC) in Extrusion Process
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.
A Mesoscale Simulation Method for Underfill Encapsulation
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.
Experimental Analysis of the Material Degradation of PET on a Co-Rotating Twin-Screw Extruder
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.
Morphological Analysis of Natural Fibers and Fiber Orientation Measurements for the Evaluation of Simulation Tools for Injection Molding Materials – NFC-Simulation
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.
Influence of Fiber Sizing and Adhesion Promoter on the Mechanical Properties of Inline-Impregnated Polypropylene Laminates
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.
Concept Development and Topology Optimization of Joint Geometries for 5-Point Double-Toggle Clamping Mechanisms
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.
Compatibilizing Immiscible Blends from Polyethylenes and Polyamide Using Reactive Extrusion
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.
Effects of Surface Treatment on Hard to Bond Plastics
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.
High Melt Strength Polyolfins for Melt Phase Thermoforming and Extrusion Blow Molding via Electron Beam Modification
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.
An Adaptive Filling to Packing Switchover Method for Injection Molding
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 . 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 . 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.
Atom Transfer Radical Polymerization of Ionic Liquids with Comb-Like Initiated by Styrene and P-Chloromethylstyrene Copolymers
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.
Effect of Nanoclay and Compatibilizer Content on Oxygen Permeability of LLDPE Nanocomposite Membranes
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.
Analysis of the Cure Compatibilization Efficiency of Peroxide/Sulphur System on Devulcanized EPDM and Polypropylene Blends with Reference to Devulcanized Tire Rubber and Polypropylene Blends
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  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.
Development of a Custom Material Model for 3D-CFD-Simulation of Melting Processes in Polymer Processing
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.
Novel Development Flame Retardant Additive for Environmentally Friendly Flame Retardant PVC Compounds
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.
A High Speed Extruder with Floating Screw Sleeve for Solid-Melt-Separation
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.
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