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

Simulation Of Polymer Imprinting And Embossing Using Smoothed Dissipative Particle Dynamics
James St Julien, Donggang Yao, June 2022

A simulation of an imprinting process using Smoothed Dissipative Particle Dynamics is shown. Cavity filling modes and their dependence on die parameters is demonstrated for single and multicavity die, showing results consistent with FEM simulations and experimental data. Particle-based simulation methods can allow for modeling of more complex fluid behaviors.

Development Of A Gas-Based Temperature Control System For Injection Molds - Gasmold
Alexander Paskowski, Ruben Schlutter, June 2022

The paper describes the development of a variothermal process, which increases the mold surface temperature during the injection molding process without significantly extending the cycle time and minimizes unintentionally heated mold areas. To this end, the possibility of achieving the desired effects by direct introduction of heated gases into the mold cavity is being investigated. By addressing central issues such as gas distribution geometry, injection possibilities, required gas temperatures or the possibility of process implementation in a demonstrator mold, it was possible to develop a process with which it is possible to achieve temperature optimization for visually appealing parts within seconds. This means that weld lines, streaks or uneven mold impressions can be concealed even on flat parts.

Discover The Physical Mechanism Of The Interface Formation In Co-Injection Molding Using Rheological Behavior
You-Ti Rao, Kuan-Yu Ko, Chao-Tsai Huang, Chih-Chung Hsu, You-Sheng Zhou, David Hsu, Rong-Yue Chang, Shi-Chang Tseng, June 2022

Co-injection molding has been introduced into industrial application for several decades. However, due to the formation of the interface between skin and core materials is very difficult to be observed, and controlled, a good quality of co-injection product can not be obtained effectively. The reason is that the formation of that interface in co-injection molding is very sensitive to various factors. In this study, the formation of the interfacial morphology and its physical mechanism in coinjection molding have been studied based on the ASTM D638 TYPE V system by using both numerical simulation and experimental observation. Results showed that the critical skin/core material ratio to generate the skin breakthrough is identified. The reason to cause the breakthrough is due to the flow front of core material catches up with the melt front of skin, and the skin is stop at a fixed distance. This mechanism is similar with that of literature. However, when the higher core material ratio is selected, the mechanism of the interfacial morphology is different. Specifically, after core melt front catches the skin melt front, the broken skin material can move forward with the inner core material to generate special core-skin-core structure. It could be due to different forces balance inside the skin and core melts, but needs to do more study in the future.

Quality Prediction In Injection Molding Based On Thermal Images With Convolutional Neural Networks
Dimitri Kvaktun, Yannick Elsinghorst, Reinhard Schiffers, June 2022

Precise predictive models are required for the use of machine learning methods for quality control in injection molding. Thermal images offer the advantage of containing information in the data that is not available in machine and process data. Currently, convolutional neural networks (CNN) have numerous applications in image recognition. Therefore, the objective of this work was to investigate the application of convolutional neural networks to thermal images of injection molded parts. For this purpose, 751 injection molding cycles from a central composite design were used. The goal was to predict the weight, height, and width of the injection molded part. The results were also compared with classical machine learning methods. Depending on the quality parameters, the networks were able to achieve an R² of up to 0.91 and were thus among the three best methods.

Changes In Polyamide 11 Microstructure And Chemistry During Selective Laser Sintering
Gabrielle Esposito, Raymond A. Pearson,, June 2022

A polyamide 11/carbon black (PA11/CB) SLS nanocomposite printing powder was characterized throughout a laser area energy density range (express by using Andrew’s numbers, AN) to elucidate significant changes to the PA11 microstructure and chemistry during the SLS printing process. We will show that there are specific microstructural changes that occur in PA11, some gradual and others more striking, between the as received PA11/CB powder and printed parts. The melting temperature (Tm), percent crystallinity (Xc), lamellae thickness (lc) and dhkl spacing of PA11 were all shown to change significantly upon printing, whereas the molecular weight was shown to have a rather gradual increase as a function of AN. These results imply that the printing conditions used result in an irreversible change in PA11 polymer microstructure and chemistry, and correlate well to the measured mechanical behavior of parts print with corresponding AN. The use of DSC, XRD, and molecular weight analysis provides a more complete picture of the changes due to the SLS printing process and can help optimize the printing parameters to create high-quality printed parts.

Twin Screw Melting Model Prediction Of Experimental Study Of LDPE Melting In A Twin Screw Extruder
Gregory A. Campbell, Mark D. Wetzel, Paul Andersen, Joseph Golba, June 2022

The melting of polymers in a twin-screw (T/S) extruder is an important operation in many industrial processes. Research by Shih, Gogos, Geng and others has identified the physical phenomena that take place during the melting phase transition. This paper describes a new approach for modeling the melting in a twin-screw extruder and the model predictions are compared with an experimental study of Low-Density Polyethylene (LDPE) melting in a co-rotating, intermeshing T/S extruder using on-line visualization and axial scanning of pressure and temperature techniques. This paper focuses on the physics and engineering concepts that are inherent in the melting mechanism in the extruder, and viscous energy dissipation in the melt with un-melted solids. The effects of throughput, Q, and at a constant rotation speed, N, is examined. Low and high Q/N ratios have significantly different axial pressure profiles.

ABS/Carbon Fiber Composite Foams With Bimodal Fine-Cell Structure Prepared Using Supercritical CO2
Han-Xiong Huang, Chang-Zhi Guo, June 2022

Via two-step solid-state foaming using subcritical CO2 as blowing agent, the foamed acrylonitrile-butadiene-styrene/carbon fibers (ABS/CFs) composites are prepared. The results demonstrate that a bimodal cell structure (BMCS) is developed in the foamed ABS/CFs composites. Small and denser cells are developed in the ABS matrix, whereas large cells are formed around the CFs due to concentrated CO2 at the ABS-CFs interfaces. The mean cell diameters are 0.39–0.92 μm for the small cells and 12.5–25.6 μm for the large cells, being dependent on the CFs content. The CFs especially at 10 wt% or higher can refine the small cells via both increasing the strength and elasticity of the ABS matrix and restricting their growth under large cell growth. Interestingly, slow depressurization for the saturated composites followed by foaming is also favorable to refine the small cells, which is mainly attributed to no cells to be preformed in the saturated composite via the slow depressurization. Relatively higher saturation pressure or modest foaming temperature can further refine the BMCS in the foamed ABS/CFs composites.

An Integrated Three Dimensional Numerical Simulation Of Nonlinear Warpage Analysis For Injection-Molding Process
Hsiang-Liang Lin, Li-Hsuan Shen, Chih-Chung Hsu, Rong-Yeu Chang, June 2022

Nonlinear warpage analysis which considers different kinds of nonlinearity effects has attracted more and more attention recently, especially in the automotive industry. This study is mainly aimed at using the new functions in Moldex3D, “Nonlinear warp analysis” and “Buckling analysis”, to predict the warpage of the products. These new solvers cooperate with the temperature distribution and the residual stress caused by the phase change from the manufacturing process and predict the deformation of the product considering the geometric characteristic and process conditions.

Multilayer Extrusion Of Higher And Lower Modulus Alternating Polymer System
Joel Thambi, Vamsy Godthi, Marco Nefs, Nadia Grossiord, Jongwoo Lee, June 2022

Multi-Layer extrusion (MLE) is an advanced co-extrusion processing technology, which enables two polymer systems to be melt extruded, combined in an alternating format to very small total thickness <100μm and arranged in higher number of layer typically ranging from 8 to 1024. The focus of this paper is to investigate polymeric materials which are high modulus (e.g. LNP™ EXL PC copolymer or polymethyl methacrylate PMMA) and relatively low modulus (e.g. TPU) in nature as an alternating material combination for MLE. By combining different modulus of polymeric materials in MLE films, it is possible to achieve desired balance of different properties like mechanical, thermal, optical, dielectric etc., by synergistically combining the properties of the individual resins. In this paper flexural test is shown as an example to discuss the mechanical performance of MLE films. One of the major challenges of the MLE process is the down-selection of materials that are thermoplastics and have “matching” viscoelasticity at the processing temperature, as assessed by viscosity measurement at lower shear rates. Additionally, in order to ensure inter-layer adhesion, solubility parameters and processing windows of the two resins must be considered. In this study differences in adhesion were noted between PC/PU and PMMA/TPU MLE system. In PMMA/TPU MLE modification of processing temperature resulted in an improved interfacial stability and interlayer adhesion.

Part 1: Ultraviolet-C (UVC) Exposure And Its Effect On Color Change For Polystyrene
Kristen Chang, June 2022

Due to the recent and ongoing pandemic – COVID-19 – there was an urgency to determine a method to delay the continuously rapid development of the new virus. As a result, Ultraviolet-C (UVC) light, also known as Ultraviolet Germicidal Irradiation (UVGI), has been in higher demand because of its known ability to disinfect quickly and effectively. However, because of its short wavelength/higher energy, either 222nm or 254nm, material degradation is usually much more accelerated than Ultraviolet-A (UVA) or Ultraviolet-B (UVB). At this moment, this study only observed color change when exposing polystyrene to UVC light, and it is believed that this is one of the first studies, if not the first, conducted with this material. Polystyrene was selected because of its availability, abundance of relevant research (ie. UVA/UVB exposure results), and its use in weathering standards. Additionally, since there are no standards specifically about UVC exposure, this preliminary research may provide some direction.

Scratch & Fracture Behavior Of Talc-Reinforced Polypropylene
Kwanghae Noh, Hung-Jue Sue, June 2022

Thermoplastic polyolefins (TPOs) have been widely utilized in a variety of automotive applications. Most importantly, the TPOs used in interior and exterior parts in automotive applications require aesthetics and good mechanical properties simultaneously. Among many of the inorganic fillers, talc is an inexpensive and natural mineral, which has the platelet structure with individual layers holding together by week Vander Waals forces. This distinct layer structure can be delaminated at low shear forces to easily disperse in TPOs. Additionally, the talc particle size can be manipulated by the various micronizing processes. In this research, talc-reinforced polypropylene (PP) systems as a set of model systems have been chosen to investigate how the particle size and surface treatment of talc influence the TPO fundamental scratch and fracture behaviors.

Monitoring Of Injection Molding Process With Piezo-Electric Sensor
Mostafa M. Pasha, Kyehwan Lee, Heinrich Foltz, Jesus Valladares, June 2022

Injection molding is one of the most popular techniques for global plastic production. With this automation technique, the plastic products can be manufactured at low cost with a complex geometrical shape. A manufacturing process with high productivity of an injection molding machine depends on optimized injection molding parameters. Injection molding pressure and temperature inside the mold cavity are the most critical parameters. However, cavity pressure transfer is not used due to cost and maintenance issues. During this research, an experimental procedure is performed to determine a process monitoring system using asynchronous data acquisition, through the incorporation of a wired piezo-ceramic sensor to acquire pressure of the injection molding system. This piezoelectric sensor is designed in such a way that, a Bluetooth device can be connected with a sensor and can take live data reading of parameters from the running molding machine.

A Recycle Stream In The Reactive Extrusion Process For Preparing Lignocellulosic Thermoplastic
Jinlei Li, David J. W. Lawton, Guerino G. Sacripante, Michael R. Thompson, June 2022

Processes needing to extrude biopolymers can be challenged by the poor flow properties often exhibited by this class of materials. Lignocellulose is one such material that is very attractive to the future polymer industry as a potential engineered biopolymer suitable for structural applications. To convert the poorly processable lignocellulose pulp into a flowable thermoplastic, the chemistry of both cellulose and lignin need to be modified, and to do so economically, attention is turned towards reactive extrusion. A reactive solution is required for the modification but also, to simply allow the lignocellulose to flow through the extruder. This study examines the novel idea of a recycle stream in reactive extrusion to reduce the normally high concentration of reactive solution needed. The goal behind the recycle stream was to produce an exiting product requiring minimal recovery of the unreacted solution without the introduction of a contaminant into the process to aid lignocellulose flow. The results showed that a comparable thermoplastic product could be produced with ~50% less reactive solution by recycling 25% of the exit stream back into the process, The recycled polymer was an effective plasticizer for the lignocellulose pulp, lowering the reliance on the reactive solution to offer this function in addition to acting as the modifier.

Experimental Studies Of High Density Polyethylene Exposed To Chlorine Dioxide Media With Various Concentrations And Temperatures
Min-Seok Choi, HyeongJu Lee, Ilhyun Kim, Byoung-Ho Choi, June 2022

High density polyethylene (HDPE) is one of the most widely used materials in the pipe industry because of its several advantages such as low price, excellent productivity, light weight and high resistance to chemical degradation. For potable water pipes, their lifespans are supposed to be over 50 years, so it is essential to check their long-term performance in certain service conditions. The point is that potable water contains disinfectants including chlorine or chlorine dioxide which shortens the service time of water pipes. In addition to disinfectant, environmental conditions like internal pressure and temperature of media inside also cause deterioration of properties of plastic pipes. To understand the degradation mechanism by potable water, we focused on two parameters, the concentration of disinfectant and the temperature of the solution. In this study, specimens obtained from HDPE pipes were artificially degraded in 5 different kinds of chlorine dioxide solutions with various concentrations and temperatures. Micro-tensile tests were conducted to study the variation of mechanical properties of HDPE specimens. The Fourier transform infrared (FTIR) spectrometry and the gel permeation chromatography (GPC) analysis were also conducted to study the variation of chemical properties of HDPE according to exposure time to chlorine dioxide solutions.

Density-Based Analysis Of Polymers Using Magnetic Levitation Device Constructed By Magnet Arrays
Peng Zhao, Jun Xie, Yuhan Jia, Lih-Sheng Turng, June 2022

Standard magnetic levitation (MagLev) device consists of two identical square permanent magnets with like poles facing each other. Limited by the size of the permanent magnet, standard MagLev device cannot levitate samples with large size. This paper proposed a novel MagLev device using magnet arrays, which can accommodate large-scale samples. Unlike magnet arrays in previous studies, all magnets employed herein face the same direction. The magnetic field generated by the magnet arrays is similar to that of the standard magnet. Within the magnetic field induced by the magnet arrays, the polymer can be levitated to an equilibrium position in a paramagnetic solution and the levitation height is related to its density. The equation correlating density and levitation height can be obtained according to the simulation results. Solutions of different concentrations were used to measure densities of a variety of polymers with an accuracy of ±0.0003 g/cm3. The non-destructive testing could also be used for plastic parts based on its posture (orientation) within the paramagnetic solution. The use of magnet arrays circumvents the trouble of manufacturing large magnets, realizes testing of polymers/parts with large sizes, and facilitates industrialization of magnetic levitation detection.

Analytical Method Development For Additive Analysis In Polyethylene
Praveenkumar Boopalachandran, Jörg Theuerkauf, Alexander Williamson, Jorge Gomes, Avery Brown, June 2022

The overall goal of the project targets the development of a product containing a rheology modifier additive in polyethylene (PE). This product is being sold to film converters for addition to the extruders of blown-film lines together with LLDPE resins. This increases the melt-strength during processing and the shrink tension for collation shrink films, enabling reduction in LDPE content and resultant tougher films. A tougher film will allow down-gauging and hence reduce material consumption, increasing the sustainability component for customers. This study focuses on the development of an analytical method at Dow to measure the concentration of the rheology modifier additive in PE. The method was validated and implemented successfully.

Colloidal Stability And Gel Prevention Of Urethane-Acrylate Interpenetrating Polymer Network Systems
Puneet Garg, Zbigniew Stachurski, David Nisbet, Antonio Tricoli, June 2022

Advances in nanotechnology and surface sciences have necessitated superior polymeric coatings with novel applications. Urethane-acrylate-based interpenetrating polymer networks are one such class of ultra-tough polymers being researched actively for their wide-ranging applications from bullet-proof vests to binders for super dewetting coatings. Urethane-based systems are well-known for undergoing side reactions which could result in instability of colloidal suspensions engendering gelation resulting in significantly reduced shelf life of synthesized formulations and coating inconsistencies over time. Consequently, it becomes crucial to examine and control the factors inducing gelation. In this study, we investigate two approaches to prevent the gelation of colloidal urethane-based suspensions. In the first approach, we tune the NCO:OH ratio, and in the second approach, urea groups were formed in the presence of water. It was observed that both approaches resulted in storage stable colloidal suspensions with more than six months of shelf life. Durability assessment of coatings however indicated that urea-containing formulation resulted in notably robust coatings as compared to NCO:OH tuned coatings which can be attributed to the presence of strong hydrogen bonding arising from bifurcated hydrogens of urea.

Extraction Of Cure-Dependent Fatigue Behavior Of Filament-Wound Composites For Fuel Cell Vehicle Applications
Royan J. D’Mello, Shardul Panwar, Anthony M. Waas, Umesh Gandhi, June 2022

The extraction of cure-dependent fatigue behavior under tension-tension fatigue is presented for filament-wound coupons. Displacement controlled fatigue tests are performed on tubular filament-wound coupons. The state of the tube is characterized by performing interrupted static tests in between the fatigue cycles. At the coupon level, the state of damage in the matrix is obtained using micromechanics expressions with the help of Digital Image Correlation (DIC) technique. The results show a noticeable difference between fully cured (95%) and 80% cured composite specimens.

Development Of A Non-Destructive Measurement Method For Quality Assessment Of Foamed Plastic Parts
Ruben Schlutter, Alexander Paskowski, Manuel Schneider, Rainer Jahn, Joshua Voll, Thomas Seul, Andreas Wenzel, Gerd Telljohann, June 2022

Foamed parts are being produced in ever greater quantities. This is done, on the one hand, to save weight and, on the other hand, to take advantage of the greater design freedom in the layout of foamed components. Until now, quality control of the foam structure has hardly been possible without destructive testing methods. Therefore, a test method is presented to qualitatively evaluate the foam structure of foamed components without destruction.

The Toughening Of Highly Crosslinked Epoxy Networks Using Core-Shell Rubber Particles
Samuel R. Swan, Claudia C. Creighton, Russell J. Varley, James M. Griffin, Bekim V. Gashi, Sayed Mohsen Seraji, June 2022

This work explores the effect of core shell rubber (CSR) addition on the resulting properties of a highly crosslinked bi-component epoxy resin blend. The effects of network structure and topology are explored and related to the efficacy of CSR as a toughener for rigid, high-Tg polymer networks. A combination of thermal, spectral, and mechanical testing shows that excellent toughness enhancement can indeed still be achieved, despite a modest reduction in flexural properties for a high glass transition temperature (~259°C) network.

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