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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A Three-Layer Foamed Composite Prepared by Rotational Molding
A three-layer composite (polymer-fiber / polymerfoam / polymer-virgin) was made by rotational molding using a laboratory-scale biaxial rotational molding machine. The mold consists of a cylindrical stainless steel of five liters of volume. A linear medium density polyethylene (LMDPE) was used in all layers. In the composite layer a natural fiber (agave) was included and in the foam layer a chemical foaming agent (azodicarbonamide, ACA) was incorporated. The effect of the agave fiber and foaming agent contents was related to the tensile properties. The inner air mold temperature and rotomolding cycle time are reported.
Root Cause Analysis and Fixing of Coextruded Polyolefin Blown Film Defects
A blown film producer experienced a film production and quality defect which prevented it from making quality coextruded films. The problem was analyzed, the root cause was identified, and a solution was implemented. The root cause of the problem was the improper installation of the die assembly onto the rotator of the line which caused molten polymer pumped from the core extruder to leak from the entry of the core spiral mandrel into the entry of the outer skin spiral mandrel. The required fix was simply to adjust the position of the locating collar of the rotator so that the die assembly properly sealed onto the rotator. Following the implementation of the fix, the film producer was able to produce quality product with the desired structure.
A Research Framework for Cooling Rate-Dependent PVT Models
An expanded framework for the use of user-defined routines inside a commercial injection molding simulation package is presented. This functionality allows external academic researchers to directly modify the injection molding simulation and obtain results for any newly proposed PVT, viscosity or core shift (fluid structure interaction) models in complex parts and processes. A demonstration case is presented by implementing a PVT model which depends on cooling rate in addition to temperature and pressure. The effects on shrinkage predictions for an amorphous part are investigated and compared with actual molding data.
Warpage Simulation of Injection over-Molding Plastics on Continuous Fiber Reinforced Composites
Injection overmolding of thermoplastic over a continuous fiber reinforced composite is one of the new manufacturing approaches for automotive lightweighting which is emerging as a potential way to increase vehicle fuel economy. It not only takes advantage of excellent strength and stiffness properties of continuous fiber reinforced composite, but also has the advantage of forming complex and intricate functional shapes with the injection molding process. Warpage simulation of injection molding helps designers optimize the part and mold design, material choice and processing parameters, in order to meet tight dimensional tolerances for assembly purposes. In this paper, we extend our warpage simulations to account for the effects of orthotropic and fully anisotropic mechanical properties of continuous fiber reinforced composite inserts. The feature enhancement includes buckling and large deflection analyses of overmolded plastic components. The numerical results from Autodesk Moldflow simulation for two plastic parts injection over-molded
Verification of Numerical approach and experiment in Using PvT Properties of Polymer to control Injection Molded Products
Warpage is a common concern in injection-molded products. The usual way to find errors when troubleshooting is to adjust parameters repeatedly. This approach depends on the experience of the operator and lacks scientific rigor. This paper establishes another method for determining reductions in shrinkage and warpage caused by the packing phase in injection molding using Computer Aided Engineering (CAE) software.
Based on the PvT curve during injection molding simulation, the optimum packing pressure and packing time can be obtained to minimize the warpage caused by shrinkage. The influence of packing parameters was investigated in Moldex3D R14 and verified by experimental work. The results of the simulation and experiment showed good agreement, which means the warpage may be minimized using the PvT curve.
Optimizing Process Condition of Compression Molding: from Material Properties Characterization to Numerical Simulation
Herein, we present the recent development in viscosity measurement by squeeze flow method. We applied this technique to investigate to fiber reinforced plastic (FRP) systems including, polypropylene-based glass mat thermoplastic (PP-GMT), and thermosetting sheet molding compound (SMC). The effects of compression rate, temperature and curing time are systematically studied. In both cases, the squeeze flow data deviate from simple power law model, and is analyzed by the approach proposed by Laun et al (J. Rheol. 1992, 36, 743) . The results demonstrate the promising potential of viscosity measurement by squeeze flow method, and great relevance to industrially important process such as compression molding. The measured rheological material properties are then used in process simulation to obtain optimal process conditions of compression molding.
Simulation of Fatigue Crack Growth of HDPE Using Crack Layer Theory; Effect of Loading Frequency
The crack layer (CL) theory has the ability to estimate the slow crack growth (SCG) behavior on the basis of the theoretical background. This theory considers the interaction between crack and damages in front of the crack tip. It facilitates the reflecting damage mechanisms which appear different depending on the material. However, the applicability of this theory has not been investigated sufficiently yet, with regard to the various loading conditions. For this purpose, the critical CL parameters with the loading conditions must be specified. In this study, the discontinuous fatigue crack growth (FCG) tests with various loading frequencies are simulated by using CL theory. The two CL parameters are changed to fit the tests, and the relationship between loading frequency and CL parameters are constructed. It would be beneficial for industrial use of CL theory.
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.
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