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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Numerical Prediction of Stiffness and Strength of a Highly Complex Topology Optimized Thermoplastic Part designed for 3D Printing
Additive manufacturing or 3D printing has revolutionized the way companies manufacture products by allowing the manufacturing of shapes considered impossible to manufacture until now. This gives the advantage of designing the parts with materials positioned in exact locations as is required from its performance loading conditions. However, while this technology is beneficial from weight-to-performance perspective, this results in highly complex shapes which are difficult to discretize for finite element analysis and performance predictions. This difficulty is even more pronounced while predicting failure strength of the topology optimized 3D printed part in addition to part stiffness.
Typically, explicit solvers are used to predict highly nonlinear events such as component failures. Traditionally, hexahedral elements are used in explicit solvers due to the higher accuracy and lower cost of simulations compared to tetrahedral elements for similar element dimensions. However, highly complex shapes generated through topology optimization are prohibitively difficult to model using hexahedral elements. This paper deals with prediction of stiffness and failure strength of a part of highly complex geometry arrived through topology optimization using advanced higher order tetrahedral elements in LS-DYNA explicit solver. Use of tetrahedral elements allows the discretization to be almost fully automated. Equivalent analysis without explicit material failure is also performed using Abaqus implicit solver for benchmarking. The predictions are compared with actual physical test results for the 3D printed parts which exhibit good correlation.
Fiber Length Degradation of Glass Fiber Reinforced Polypropylene during Shearing
This paper contains investigations of the influence of the fiber concentration on the degradation of fiber length during shearing. For this examination, compounds of polypropylene and glass fibers have been manufactured which contain 20%, 30%, or 40% glass fibers by weight. At the start of the investigations, the initial fiber lengths are determined in each compound, which in terms of mass average ranges from 446 ?m to 663 ?m. Afterwards, the compounds are exposed to a drag flow in a Couette rheometer; this flow is generated in a shearing gap between a rotating piston and the corresponding cylinder. The investigations are carried out for varying lengths of shear time and varying rotational speeds. At each experimental interval, specimens are taken and optically analyzed to determine fiber length. With this method, the fiber length degradation over time can be determined, as well as its relation to the fiber content and the occurring shear rate.
Development of an Inline Plasma Treatment during Injection Molding Process
In order to fulfill continually increasing requirements in optical and haptic applications, in particular requirements for the functionality of injection molded components, it is frequently necessary to make use of additional processing steps such as coating, bonding, or two-component injection molding. However, due to the low surface energy of many polymers, the necessary adhesive strength cannot be achieved without further modification. One typical surface treatment for increasing the surface polarity of plastics and improved adhesion properties is atmospheric pressure (AP) plasma treatment. Typical applications of this method use CNC-automated machinery, which enables good results to be achieved with a high degree of consistence, but which unfortunately are difficult to implement for inline application.
With that in mind, the goal of the research presented here was to develop a surface treatment process which makes inline plasma surface modification during an injection molding process possible. This contribution describes the development and investigation of surface treatment with a stationary plasma jet, as well as the integration of this technology in the injection molding process.
Degradation Inspection of GFRP Storage Tank with Long-Term Use under Hydrochloric Acid
It is necessary to understand how much life the materials used as structural elements have. Therefore, two types of specimens, GFRP storage tank used under hydrochloric acid for 22 years and blank GFRP materials, were used as specimens in this study. We tried to evaluate the degradation mechanism of these specimens by using Optical microscope, SEM observation, ultrasonic measurement, and electrical resistance measurement. As results, it was found that the glass fibers of facing surface side with hydrochloric acid solution were dissolved by penetrating the hydrochloric acid and these parts had lower surface electrical resistance as compared with non-degradation parts because of losing the electrical resistance of glass fibers. In addition, the ultrasonic measurement revealed the decrease rate of intensity between the blank and GFRP storage tank samples was different. In this paper, the mechanism is discussed on the basis of these results.
Two-Shot Overmolding Cooling Simulation
Two-shot overmolding is a specialized injection molding process in which two polymer materials are molded together to form a single part. Two-shot overmolding has many advantages over conventional molding in that it is more cost effective, has a stronger bonding strength, and enhanced product quality. Despite these advantages, obtaining an optimal mold design is difficult due to the complexities of the process, e.g., the complicated rotational mechanism of the mold platens. Mold cooling simulation can be used for optimizing the design of the cooling system, minimizing cycle time, and eliminating defects in the final part. This paper outlines a tailored mold cooling solution for the transient and steady state simulations of the two-shot sequential overmolding process. The transient state solution and steady state solution are verified with a case study at the end of the paper.
Carbonization of polyacrylonitrile Nano Fiber by Cotton Candy Method
In this study we focused on r Carbon Nano Fiber (CNF) in the carbon-based nanomaterials’s field. CNFis expected to various applications. However, the CNF have a high cost of production. Therefore we are trying to reduce a cost to make a preparation of precursor of the CNF using Cotton Candy Method (CoCaM).
Cotton candy method (CoCaM) is novel method that can create a lot of nano fiber. CoCaM is a method of forming a fiber with only air injection. Therefore it is possible to make a cost saving by CoCaM, because it does not require heating and the electric field. We studied about carbonizing conditions for nanofibers. After carbonizing, the diameter of nano fiber decreased. Carbon nanofiber was maintaining the shape of the fiber. According to the result of raman spectrometry, it is revealed the high crystallinity of NCF.
Ultrasonic Measurement of Particle Concentration in Polystyrene/Glass Beads Composites by a Differential Scheme
The attenuation spectra obtained from ultrasonic measurement is applied to estimate the particle concentration in general purpose polystyrene (GPPS) /GB (glass beads) composites by a differential scheme. Composite samples with particle radium 80 ?m are tested at five volume fractions ranging from 6 % to 40 %. The longitudinal attenuation characteristics of these samples are found to depend markedly on the particle concentration and be consistent with the theoretical curve cased on the differential scheme. Combined with differential scheme, the attenuation spectra tested is used to determine the unknown particle concentration of two new samples. The predicted particle concentrations are found to be in remarkable agreement with the experimental results obtained by the ash content method.
Crystallinity Distribution Analysis by Raman Mapping for Polyethylene of Raised Temperature Resistance after Longterm Hot Water Immerssion Tests
Recently, plastic pipes for hot water supply plumbing such as polyethylene are require the higher performance for durability. Non cross-linked polyethylene of raised temperature resistance (PE-RT) is very promising because of its variety and recyclability. It is important that the degradation mechanism in hot water is understood for developing higher durablity pipes. But the systematic analysis of these aged samples has not been undertaken so far.
In this study, a PE-RT test piece was immersed for long term in hot water condition?60,90 and 110°C? up to 12000h. Tensile and thermal properties (DSC) were measured. The tensile strengths were increased up to 3000h and, after that, it reached an almost constant value at every test temperature. The change in heat of fusion by DSC increased in crystallinity which corresponded with these strength values. Tensile elongations at break did not vary much under 60 and 90°C condition. Also, it was very peculiar that elongations at break under 110°C condition were remarkably reduced up to 12000h.
Raman mapping method was used to examine the distribution of crystallinity. It was found the dispersion degree of crystallinity increased over test time from the analysis of Raman peak intensity ratio (crystal to amorphous) . The dispersion of 110°C test samples was remarkably increased and showed distribution curves with multiple components. The elongation decrease was assumed to be caused by this inhomogeneous crystallization by heat which may yield to deformation or defects in micro region structure of polyethylene.
The Effect of Ozone Ageing on the Chemical, Physical and Barrier Properties of Packaging Films
The effect of ozone (O3) on films of linear low density polyethylene material containing UV additive (LLDPE-UV) and without UV additive (LLDPE-non-UV) have been investigated for the change in chemical, mechanical and barrier properties by exposing in O3 for a long term. The LLDPE-UV material which was exposed up to 312hrs in O3 shows good resistance by causing less formation of oxygen-containing functional group having carbonyl index (CI) of 0.34 vis’ a vis’ LLDPE-non-UV shows drastic changes in the chemical structure resulting in 2.68 of carbonyl index. The ozone resistance of LLDPE-UV film is further substantiated by improvement in tensile strength property retention time over LLDPEnon- UV films by 137%. The barrier property like water vapor transmission rate was decreased by 23% and 18% upon ageing in O3 medium for the LLDPE-non-UV and LLDPE-UV films respectively.
Foaming Behavior of Fluorinated Ethylene Propylene Copolymer using Supercritical Carbon Dioxide
Foaming processes of Fluorinated Ethylene Propylene copolymer (FEP) and its composites using supercritical carbon dioxide (scCO2) as the blowing agent have been investigated. The batch foaming process was employed at temperatures ranging from 250 °C to 265 °C and pressures ranging from 12 MPa to 24 MPa. The optimal foaming temperature and saturation pressure have been obtained for both pure FEP and FEP composites with 1wt% different-sized BaTiO3 as the nucleating agent. Pure FEP Foam cell diameter ranging from 80-140 ?m has been observed while the cell diameter is decreased to 20-40 ?m after adding the given BaTiO3 particles. The cell density of foamed FEPs increased from 106 to 108 cells/cm3. Moreover, an abnormal phenomenon that expansion ratio decreased with the increasing saturation pressure, has been found for the pure FEP foams. It is explained by the relationship between foaming and crystallization processes.
Investigation on Injection Compression Molding (ICM) for Improving Metal Injection Molding (MIM) Molded Part Qualities
Metal injection molding (MIM) is a series of processes for producing small, complex, and precise metal parts. The mixture material is processed through injection molding, de-binding, and sintering. Previous research has largely studied the effect of the feedstock properties, such as density and powder concentration, on the final part quality. This study used Injection Compression Molding (ICM) technology in the MIM process to discuss the part density and hardness. Several conventional MIM parameters and ICM parameters were investigated. Further, experimental results were verified using the commercial simulation software Moldex3D. The results showed that applying ICM technology in the MIM process improves both the uniformity of the entire part density and its hardness. The part density increased via use of the mold-open gap and appropriate compression speed. Moreover, the simulation results were in good agreement with the experimental results.
Melting Phenomena and Sample Preparation Method within a Partly Filled Melting Zone of Co-Rotating Twin Screw Extruders
This paper focuses on the melting process in co-rotating twin screw extruders (TSE). A method is presented to generate experimental quantifiable values for the partial melting of polymer samples from different melting zones. Furthermore an insight into results of melting degree studies with partially full and fully filled melting zones is provided, which allows important insights into the melting behavior of intermeshing co-rotating twin-screw extruders. As a part of the evaluation of these results an alternate concept for the usage of fully filled melting zones is presented and discussed in matters of its ad-vantages.
Simulation of an Industrial High Capacity Blown Film Extrusion Process
One of the most important production processes for manufacturing plastic films is the blown film extrusion. The conventional way to improve the output of a production line can be achieved by a substitution or a modification of the limiting air cooling ring. In order to verify an output intensification, typically the trial and error method is being used. For reducing the experimental costs, a numerical procedure called Process Model has been developed for simulating the formation of the bubble with regard to changing process conditions and rheological behavior. The applicability of the Process Model has been proven for small production lines with a maximum output of approximately 100 kg/h (LDPE).
According to industrial concerns, the Process Model has to be verified for higher mass flow rates (> 750 kg/h). Therefore, the numerical procedure has to be adapted. Besides a modification of the simulation domain and the integration of an internal bubble cooling device (IBC), an adaption of the material model has to be done. For the consideration of the material behavior from each layer of the multilayer film, a specific approach has been developed and used. In this paper, the simulation results of the first application of the Process Model for an industrial blown film line including an internal bubble cooling system will be presented. This device intensifies the heat exchange and enhances the bubble stability with regard to higher air volume flow rates . The resulting heat exchange and the flow phenomena will be discussed.
Influences of Processing Parameters, Material, and Mold Geometry on the Shape of Caverns as a Quality Parameter for Electroplating on Plastics
For automotive application processing technical polymers like acrylonitrile butadiene styrene (ABS) or polycarbonate blends (PC/ABS) with injection molding and refining them by electroplating is state of the art. The surface quality and processing parameters during the injection molding mandatorily influence the resulting part quality. Besides the electroplating parameters, the surface of the injection molded part is responsible for the conjunction of the polymer and the metal layer system. The surface and adhesion of the hybrid material combination is defined by etching butadiene in the part surface to a cavern structure.
An objective evaluation method for quantifying the two-dimensional shape of caverns is developed by using image analysis. The analysis is based on scanning electron microscope (SEM) images of chemical etched polymer part surfaces (ABS, PC/ABS). For quantifying the surface, meaningful key figures (e.g. roundness, degree of orientation, caverns/?m², and area of caverns) are emerged. Finally, different materials, etching times, and processing parameters are compared to results of climate change tests and the analytical valuation of the surface structure.
Microstructure-Property Relationship for Impact Energy Absorption of Functionally Graded Porous Structures of Acrylonitrile Butadiene Styrene (ABS)
Functionally graded (FG) structures are advanced class of composite materials where the microstructure is gradually continuous. This continuity eliminates problems like stress jumps and delamination that are encountered with conventional composite materials. FG porous structures have the added advantage of high strength-toweight ratio compared to the solid FG materials. Strengthto- weight ratio can be tailored with controlled fabrication processes to satisfy certain design requirements. Microstructure-property relations help in selecting the appropriate microstructure for required strength and provide a guide to fabrication procedures. In this work, FG porous structures of ABS are fabricated with thermally activated microspheres and compression moulding with a special mould design. Gradient in the porous structure is created by inducing thermal gradient across the thickness. SEM images of the porous structure were analyzed by locally adaptive thershoulding technique which is based on minimizing an energy functional of the thresholding surface through a variational Minimax algorithm. The purpose of local threshoulding is to extract accurate information about the microstructure like pores’ diameters and porosity. This information is then utilized to run correlation analysis between microstructure to processing and microstructure to impact energy absorption. The results showed the potential to control microstructure and hence tailor impact energy absorption. Impact energy is shown to be more correlated to pores’ average diameter than to porosity.
Evaluation of Liquid Crystal Polymers (LCP) as an Additive for Polybutylene Terephthalate (PBT) to Improve Melt Processing and Properties
Liquid Crystal Polymers (LCP) are partially crystalline aromatic polymers based on p-hydroxybenzoic acid and related monomers. LCP’s offer numerous benefits such as higher melt flow during molding, low warpage, good dimensional stability, better moldability, superior mechanical and thermal properties, excellent chemical resistance, flame resistance, and weatherability and are used in thin walled and optical applications. This paper evaluates the use of LCP as an additive to improve the properties and performance of Polybutylene Terephthalate (PBT). Unfilled PBT formulations with different loadings of LCP (0.25wt% to 5wt%) were compounded and tested. Rheological analysis was performed using a capillary rheometer to quantify the influence of LCP in melt flow of unfilled PBT. Thermal analysis through DSC was performed to measure the influence of LCP on crystallization phenomenon of PBT. Mechanical properties and heat deflection temperature were measured to estimate the differences in performance between the various formulations.
Ultrasonic Sealing Tool Design for Thin Film Plastics
Thin film packaging is used for a wide range of products including packaging of food, medical tools, electronics, and toys. Each of these applications requires a different type of film, from thin and brittle, to composite film including a foil layer, to biodegradable films. These films can be adhesively bonded, heat sealed, impulse welded, and increasingly, ultrasonically welded. Ultrasonic welding offers many benefits to thin film sealing such as faster cycle times, reduction in film usage due to narrower bond widths, elimination of adhesive layers, improved hermeticity for increased shelf life, and less sensitivity to contaminants in the seal area.
However, tool design can have a significant effect on weld strength. Optimum tool design depends not just on the thickness of the material to be welded, but also the type of polymer to be joined, and seal requirements (such as hermeticity and peel strength). In this study, we seek to provide starting guidelines with the goal of lowering the cost and duration of the tooling development process by investigating the achievable peel strength of a wide variety of film types with twenty-five horn and anvil design combinations.
Comparative Analysis of Energy Director Styles on Polybutylene Terephthalate (PBT) with Servo-Driven Ultrasonic Welder
In ultrasonic welding of plastics, the design of the energy director can be crucial to achieving an optimal weld, especially for semi-crystalline plastics like polybutylene terephthalate (PBT). However, it can be difficult and expensive to maintain a sharp energy director on molded parts. Consequently, there is significant interest in determining if an alternative joint design can be used to produce comparable strength to the traditional 60-degree triangular energy director used for semi-crystalline materials. In this study, four different joint styles are compared using the Dukane 30 kHz iQ Servo ultrasonic welder. A shear joint, round, 60- and 90-degree energy directors were analyzed in terms of both tensile strength and weld characterization, which was determined by microscopic inspection of cross sections.
To achieve a baseline for testing, velocity profile calculations were made by finite difference analysis (FDA). During welding, plots were made of force and displacement over time. Several weld setups were used to weld all four joint designs. The primary parameter investigated was weld velocity magnitude and profile. The resulting force profiles were analyzed for trends as well.
Evaluation of Branched Polypropylene Degradation by Using Different Constitutive Equations
In this work, virgin as well as thermally degraded branched polypropylenes were investigated by using rotational and Sentmanat extensional rheometers. Based on the shear and extensional rheology data it was deduced that both chain scission and chain branching takes place during thermal degradation of the tested polypropylene. It was found that simple constitutive equations such as Generalized Newtonian law, modified White-Metzner model and Yao model can be used to describe the measured steady state shear and uniaxial extensional viscosity data. It was revealed that Yao and Generalized Newtonian models have capability to quantify level of extensional strain hardening (i.e. the maximum steady state uniaxial extensional viscosity divided by 3 times Newtonian viscosity) as a function of degradation time via their parameters not only quantitatively but also qualitatively.
Analytical Solutions of Nonlinear Constitutive Equations for Large Amplitude Oscillatory Shear (LAOS) Flow
Nonlinear viscoelastic models have been studies to elucidate the nonlinear behavior of viscoelastic materials. It is axiomatic that the analytical solutions of these constitutive equations are helpful to investigate various viscoelastic flows. For this reason, studies on calculating the analytical solutions of viscoelastic models have been spotlighted. However, various studies rely on power series approximations and it cannot overcome the inherent limitation of convergence radius. In this study, new approach is suggested to calculate analytical solutions of the Giesekus model. This approach provides systematic way to calculate not only shear stress but also normal stress under large amplitude oscillatory shear (LAOS) flow.
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