SPE Library
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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Conference Proceedings
Development of Sealants for Flexible Packaging Using Light Microscopy
Polyolefins used in flexible food packaging play a key role in enhancing our everyday lives. Food packaging extends shelf life, protects products from physical damage and keeps bacteria out. The development and design of food packaging require that scientists and engineers understand material properties, structure and performance. Analytical tools such as optical, scanning and transmission electron microscopies play key roles in material analysis and development at Dow Chemical. This paper provides an overview of how light microscopy (LM) techniques were used to evaluate heat seal performance such as hermeticity and hot tack in vertical form fill and seal (VFFS) packages. Having the ability to correlate heat seal temperature with performance is helping accelerate development of differentiated resins for flexible VFFS packaging.
Effect of Ultrasonic Treatment on Electrical and Rheological Percolation Threshold of Polycarbonate-Carbon Nanotubes Composites
A twin-screw extruder having an ultrasonic treatment zone was used to prepare polycarbonate (PC)/multi-walled carbon nanotubes (CNT) composites. The effect of ultrasonic amplitude and CNT concentration on processing characteristics, rheological properties, electrical conductivity and mechanical properties of both high (HPC) and low (LPC) PC filled with 0.2-1.5 wt% CNT was studied. Ultrasound showed significant effect on improving the dispersion of CNT in both HPC and LPC composites, as indicated by the increase of storage modulus at low frequencies, decrease of the rheological and electrical percolation threshold. Specifically, the rheological percolation of LPC composites decreased from 0.10 vol% for untreated samples to 0.055 vol% for treated samples at an ultrasonic amplitude of 13 æm. Meanwhile, the electrical percolation threshold of LPC composites decreased from 0.176 vol% for untreated samples to 0.088 vol% for treated samples at an amplitude of 13 æm. Additionally, obvious improvement in mechanical properties (including elongation, tensile strength, yield strength and Young?s modulus) of HPC composites after ultrasound treatment at 13 æm was observed. Finally, a possible mechanism of the decrease of both rheological and electrical percolation threshold by ultrasonic treatment was proposed.
Prediction of Failure in Foams Using Finite Element Method
Foams are widely used materials for light-weighting in various applications especially for the transportation industry. The mechanical properties of the foams depend on the cell morphology (i.e., shape and size) and volume fraction. Obtaining an experimental correlation between mechanical properties and morphology can be tedious and challenging. Developing a numerical methodology for predicting the mechanical properties especially the stress-strain curve of foams, can enable optimization of structures/morphologies for the required performance with lower resources.
In this paper, finite element method has been used to determine the stress-strain curve of foam including the ultimate stress and elongation to failure. Two cases, one without failure and the other with failure in the material model for simulation are presented. For both cases, a good correlation between the experimental and simulation was obtained in the initial elastic response and the plastic strain hardening regions of the stress-strain curve. Using the case with failure, the ultimate stress and the elongation at failure was predicted. It is found that the simulation over estimates the failure strain, mainly due to the way the failure model removes elements in Abaqus?. By making suitable changes to the code or to the failure threshold (calibration), prediction of failure in foam can be improved. The latter is illustrated in the paper.
Numerical Investigation and Experimental Validation for Wax Pattern Formation through Injection in Investment Casting
Lost wax process is widely used in metal casting to manufacture high precision products. However it covers lots of procedures, high precision quality is very difficult to obtain via conventional trial-and-error method. In this study, numerical method to simulate the wax pattern formation through injection molding in investment casting was proposed. To get better understanding, one hardware model is used to examine its shrinkage behavior numerically and experimentally. Through natural shrinkage and fixture constraint shrinkage study, the shrunk wax pattern dimensions and shrinkage percentage at various circular edges and location were measured. Simulation and experimental results are in good agreement. Specifically, the shrinkage difference between experiment and simulation is less than 1%. As the good control for the first step of wax pattern formation, it can further assist the shell formation and metal casting.
Numerical Simulation for Screw Geometry Design and Performance Effects on Fiber Breakage Study
Due to the high demand of smart green, the lightweight technologies become the driving force for people in automotives and others development in recent years. Among those technologies, using short and long fiber-reinforced thermoplastics (FRT) to replace some metal components can reduce the weight of an automotive significantly. However, the microstructures of fiber inside plastic matrix are too complicated to manage and control during the injection molding from screw, to runner, to gate, and to cavity. In this study, we have integrated the screw plastification, to injection molding for fiber microstructures investigation. More specifically, paid most of our attention on fiber breakage prediction during screw plastification. Results show that fiber breakage is strongly dependent on screw design and operation. When the screw geometry changed, even the compression ratio is lower, the fiber breakage could be higher.
Post Shrinkage Effect on Thick Optical Lens Development
This study investigates the geometric accuracy of thick fisheyes lens under injection molding. The effects on the geometric accuracy resulting from processing parameters in conventional injection molding (melt temperature, packing pressure, and filling time) and in injection compression molding (compression speed and compression distance) are studied in detail. First through simulations of Moldex3D, the relations between geometric accuracy and processing parameters are predicted. Then, the predicted results are compared with experiments. The comparisons show the trends in simulations and experiments are consistent. Nevertheless, there are discrepancies in quantities. To find the cause of the discrepancies, the re-heat phenomena after demolding are investigated.
Meeting Global Challenges with Micro Solutions: The Role of Plasma Surface Treatment in the Future of Plastics
The industrial landscape is ever changing. Some changes come from new discoveries and improvements; others are responses to problems and failures with existing methods. Still others are triggered by competitive market forces and demands such as lower cost. This paper examines seven global trends in plastic part manufacturing:
1. Greater use of regrind and recycled plastic resins 2. Increased interest in thin walled plastic parts 3. Continuous weight reduction in automotive 4. Growth of plastics with bright metal appearance 5. Further reduction in solvent use 6. More UV coating applications for plastics 7. Continued growth of medical plastics Each of these represents new business opportunities as well as new implementation challenges. In particular we study the role that plastics? surface are expected to play in the success or failure of these new opportunities. We propose that plasma surface treatment provides a workplace safe, environmentally friendly, and cost effective means for meeting these new challenges.
3D Volume Shrinkage Compensation Method in Injection Mold Design Optimization
Injection molding is used widely in plastic production at present. However, how to optimize the manufacturing process will be the key to the product quality. To make the product development more successful and economical, CAE is essential to integrate instead of trial and error. Furthermore, warpage defect will cause more problems on the product accuracy or assembly directly. How to solve the warpage problem effectively is still in great demand. In this study, we have proposed ?3D Volume Shrinkage Compensation Method (3DVSCM)? to optimize the warpage quality. Specifically, we have investigated a mobile phone case systematically through trial-and-error method, industrial global compensation method, and 3DVSCM. Due to assemble purpose, there are twelve specifications needed to be satisfied at the same time. Results showed that using the trial-and error method, it is too difficult to keep all twelve specifications into the target. Meanwhile, using the industrial global compensation method with 0.48% compensation, it is still about 25% of specifications which are still not fit the target. However, using 3DVSCM, all twelve specifications can be fitted into the target easily. It will reduce the time and cost in product manufacturing process effectively.
The Influence of Processing Conditions on the Crystallization Behavior of Polypropylene Modified by Ionomers
The non-isothermal crystallization behavior of polypropylene modified by ionomers based on ethylene copolymers (Surlyn 8610, 8920, 9020 and 9320) were investigated by differential scanning calorimetry (DSC). The crystallization rate of polypropylene was accelerated by the ionomers which initiated heterogeneous nucleation of the polypropylene. The influence of processing conditions on the crystallization of polypropylene modified by the ionomers was investigated. The study showed that the screw configuration of the intermeshing co-rotating twin screw extruder with strong mixing capability increased the crystallization rate of polypropylene modified by the ionomers more efficiently than that with weak mixing capability. Furthermore, the re-compounding of polypropylene/ionomers pellets with the severe screw further improved the crystallization rate of the systems.
Dynamic Behavior of Core-material Penetration in Multi-Cavity Co-Injection Molding
Co-Injection Molding and multi-cavity molding are very common processes for plastic manufacturing. Sometimes, co-injection and multi-cavity molding combined system is applied in some forks structure products. The core penetration and flow balance control problems are very difficult to manage. Also the inside mechanism of co-injection multi-cavity system is not fully figured out. In this study, we have focused on dynamic behavior of core-material penetration in a co-injection multi-cavity molding. The dynamic behavior of core penetration is very sensitive to injection speed and also skin/core ratio. The largest core penetration has been shown to change dramatically from one runner to the other. In addition, the core penetration behavior will display imbalance at the end of filling. The more core ratio, the longer core penetration runs through runner to cavity. However, due to the multi-cavity geometrical structure, the balance of the core penetration for multi-cavity is still very challenging. Finally, the simulation is validated with the literature result [9]. These results show both simulation and experiments are in a good agreement in trend.
Implementation of Post Consumer Recycled Plastic in Electronic Products
The path towards the use of post consumer recycled plastic in electronic products has a long and cyclical history. The use of these materials is ultimately desired not only for the environmental benefit to our world, but also for the potential financial benefit of reclaiming a high value waste stream. To most outside the plastics or recycling industries, recycling plastic seems like a simple and obvious thing to do. The reality of it however is much more complicated. Ever-changing variables such as supply and demand, shifting waste streams, environmental regulations, and the price of oil, keep the sand shifting under the feet of those trying to succeed in this field. Together with recycling industry leaders our team has worked through many of the obstacles to achieve industry leading post consumer recycle content in our electronic products. Here we will present the history and challenges of a project set forth to increase post consumer recycle content, and demonstrate the benefits of the project in the form of successful implementation of its results.
Effect of Process Parameters on Electrical Conductivity of Injection-Molded Polypropylene/MWCNT Foams
The microcellular injection molding of polypropylene-multiwalled carbon nanotube (PP-MWCNT) nanocomposites was conducted and the relationships between process, microstructure and electrical conductivity were determined by investigating the effects of various processing parameters such as void fraction, gas content, melt temperature, and injection flow rate on the microstructure and electrical conductivity. When physical foaming was implemented in the injection molding process, the electrical conductivity increased up to five orders of magnitude while the overall weight decreased by 40%. The results revealed that a high injection flow rate, and optimal values of gas content and melt temperature yield the highest electrical conductivity. It was also concluded that the processing parameters influence the electrical conductivity through changing the solid skin layer thickness and the cellular morphology of the foamed core.
Mechanisms of Foaming-Induced Thermal Conductivity Enhancement in Polymer Matrix Composite Foams
Thermally conductive low density polyethylene (LDPE)-hexagonal boron nitride (hBN) composite foams with different foam morphology and/or filler sizes were fabricated to investigate the underlying mechanisms of foaming-induced enhancement in the effective thermal conductivity (keff) of polymer matrix composite (PMC) foams. It was found that cell size, cell population density, and filler size are key factors that govern the networking of thermally conductive hBN platelets in PMC foams, and thereby their keff. The keff of PMC foams increased by 26% and 23% over their solid counterparts when they were loaded with 9.21 vol.% hBNs with average sizes of 6 æm and 45 ?m, respectively. However, the LDPE-hBN foams contained 27.63 vol.% hBN had their keff decreased monotonically as the volume expansion percentage increased. In this work, the elucidation of the morphology-to-property relationship of thermally conductive PMC foams offers new direction of thoughts to design and fabricate light-weight and/or flexible multifunctional materials for heat management applications.
Numerical Simulation and Experimental Verification in Cell Nucleation and Growth with Core-Back Foam Injection Molding
This study presents the recent development of three-dimensional prediction of microcellular foam injection molding with core-back operation by supercritical fluids (SCFs) nitrogen. In addition to the filling behavior in whole core-back process, the effects of nitrogen gas concentration, core-back distance, and dwell time on cell morphology are also numerically investigated. As a consequence, the final bubble size and bubble number density show good agreement with experimental cellular structure probed by scanning electron microscope.
The validation of simulation results with experimental data proves the capability in 3D simulation of core-back foam injection molding, Moreover, it provides foam morphological insights and design guideline to economically manufacture products.
In-Situ Measurement of Internal Mold Pressure on Chemical Foaming Process
The experimental technique to evaluate the internal chemical foaming process was developed. The internal mold pressure and temperature were measured during chemical foaming process of LLDPE. The experimental result showed that the internal mold pressure was rapidly increased through the induction phase, and then increased gradually. The maximum mold pressure was dependent on the content of the chemical foaming agent. On the other hand, mold temperature was independent of the content of chemical foaming agent.
Investigation on Orientation and Distribution of Metal Fiber in Epoxy Substrate Controlled by Electromagnetic
Following by the advance of technology, application of high polymer composites is more and more wide. In product development, controlling orientation and distribution of fiber composites is one of the key. This study uses induction electromagnetic field controlling fiber orientation and distribution in fluid and investigates effect of fiber orientation and penetrating conductivity. It uses three variables including substrate viscosity, magnetic flux density and fiber length for studying the effect of fiber steering and verifying the relationship between fiber orientation and penetrating conductivity.
In the results, most non-magnetic field controlling fiber angle are mainly in 0~30 and 151~180. The number of dynamic magnetic field controlling fiber angle mainly concentrates in 61~120. The fiber orientation level of static magnetic field controlling is higher than dynamic magnetic field controlling. The penetrating conductivity of static magnetic field controlling and dynamic magnetic field controlling increases 12.2 and 9.6 times than non-magnetic field controlling respectively. On the other hand, for fiber, lower viscosity has less ambient resistance; higher magnetic flux density has higher magnetic torque. Both of them causes that fiber is more easily arranged along magnetic direction by electromagnetic field. Conversely, longer fiber interferes with each other easily. 1mm fiber has the best fiber orientation. Above of all, these can verify that the feasibility of induction electromagnetic field works on fiber orientation.
Through 3D Simulation to Study Resin Transfer Molding (RTM) Process with Sandwich Structure and Gravity Effects
This study presents an integrated and novel analytical system to predict the resin transfer molding (RTM) process. Recently, the multilayer fiber mats, called sandwich structure [1],is used widely in boat and aircraft parts to strengthen the construction. This study focuses on two effects of RTM, one is the flow pattern and filling time of resin in the sandwich structure, and the other is the effect of gravity. Using numerical simulation tools, we can observe the resin flow within the mold. In sandwich structures, due to the different materials between core and skin, the resin flow is slower near the boundary region than the central region of the mold. In addition, three-dimensional simulation is used to predict the filling behavior in the wind turbine blade manufacturing process. The comparison between simulation and experiment result shows the capability of 3D numerical simulation on the filling behavior of the RTM process. It is seen that the simulation results are consistent with the experimental and analytical results. We expect that this study will help to clarify relevant issues and then reduce the trial-and-error time and material.
Influences of Wood Particle Shape and Surface Modification of Wood on Wood/PP Composites
Nature fibers are increasingly being used as reinforcement in commercial thermoplastics due to their low cost, high specific properties and renewable nature. All of nature fiber, wood is the most popular one that researched by many scientists. To understand how wood flour influence the mechanical properties of polypropylene composites, we first investigated the effect of different sizes of wood flour particles on the mechanical properties of wood-flour-filled polypropylene composites by tensile test. And we modified the surface of wood with H-1000P and bondfast (BF-E), researched effect of them to mechanical properties of wood/PP composites based on tensile test. The result shows that the wood/PP composites which reinforced by high aspect ratio wood, the elastic modulus will be improved, which reinforced by low average particle length, the elongation will be better. On the other hand, according to modifying the surface of wood by H-1000P and BF-E, the mechanical properties of wood/PP composites is improved.
The Influence of Rheological Properties of the Material Formulation on the Cell Size and Cell Density of Physically Foamed Polyethylene
In this study physical foaming of low density polyethylene (LDPE), high density polyethylene (HDPE) and different blends of the two polymers was examined. The rheological properties of formulations were characterized using a cone plate rheometer to compare the influence of the used polymers. The foaming behavior was investigated by using a grooved single screw extruder with a screw diameter of 45 mm. For the experiments three different die geometries were used to show the influence of the interaction of the deformations and the rheological properties of the polymer melts. For the study azodicarbonamide, normally used as a chemical blowing agent, was used as nucleating agent and supercritical CO2 as blowing agent. The aim of this study was to determine, how the rheological properties of the material formulations influence the cell size and the cell density of the polymer foams and to find out if there are correlations between the relaxation times of the material formulations and the foam morphology. The different dies were used to show the influence of the dwell time and the flow conditions in the dies. It was shown that there is a correlation between rheological properties and the foam morphology and that it is important to use proper die designs for polymer foaming, especially for formulations with high relaxation times.
Induction Heating Simulation for the Plastic Injection Molding Process
Injection molding technology now relies on in cycle variable mold heating and cooling in order to improve the surface finish and general part quality without increasing cycle time. Induction heating has the potential to be the most efficient method for heating specific areas of the mold quickly. Induction heating results in a non-uniform temperature distribution concentrated in the surface skin of the mold body touching the part. Simulation of induction heating offers the mold designer an insight into the mechanisms of induction heating before investing in this technology. This paper describes the development of a 3D finite element based electromagnetic solver that is used in the Autodesk Simulation Moldflow transient mold cooling solver. The derivations of the relevant equations are explained as well their effects on the mold during heating. Induction heating is then demonstrated on a real world model.
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