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
Injection Molding Of Thinner Parts Using Mold Surface Coatings
Davide Masato, March 2019
Injection molding of parts characterized by large overall dimensions is a challenging task due to the rise of cavity pressure during the filling phase. Process limitations lead to oversized design solutions and cavity thicknesses that are greater than the structural properties required for the part. In this work, a novel approach to thickness reduction is proposed exploiting the thermal-insulation effect of mold surface coatings. The effects of different mold surface coatings on the melt flow resistance of polyethylene terephthalate was experimentally characterized. Then, the thermal boundary condition of a numerical injection molding simulation was calibrated and it was used to quantify the thickness reduction associated to each coating. The results show that mold surface coatings can be used to improve the design of injection molded parts by reducing their wall thickness.
An Injection Moldable Ultra-High Molecular Weight Polyethylene For Medical Applications
Jeff Haley, March 2019
There is a long history of the use of ultra-high molecular weight polyethylene (UHMW-PE) in orthopedic implants, due to its excellent wear, friction, and impact properties. But the high molecular weight and extremely high viscosity of UHMW-PE limits the processing methods available. This paper examines the properties of a UHMWPE material with a viscosity that makes injection molding possible. We compare the injection molding performance of this material with a standard high density polyethylene, and compare the mechanical and wear properties of the material with conventional UHMW-PE. Additionally, we explore the effect of electron beam treatment on material properties.
Investigation On The Electrical Induced Mechanical Deformation Of Polycarbonate Monolithic Film
Ci Zhang, March 2019
Electrically induced mechanical stress was produced within polycarbonate(PC) monolithic films when subjected to an instantaneous DC voltage using a needle-plane electrode setup. The electrical induced mechanical deformation on PC surface was measured and characterized. It was found that a conical indentation was created upon the application of the field, and the depth and volume of the indentation increased as applied electric field increased. The loss energy was determined from the recorded charge-discharge current profile, and its relationship with the indentation will be discussed. A series of experiments on the application of instantaneous DC field with different durations between charge and discharge was carried out to study the effect of time on the plastic deformation. The results manifested that the indentation is a time-dependent deformation under a constant applied field, which is similar to creep phenomenon. Annealing treatment at elevated temperature was performed on the indentation and full recovery of the deformed volume was observed at temperature above the Tg of polycarbonate, indicating that the indentation is a mechanical deformation.
Inline System For Optical Quality Assurance Of Multi-Step Processes
Jens Wipperfurth | Jonathan Alms | Christian Hopmann, March 2019
The quality of foams especially the foam structure or the porosity is often controlled using cameras and image processing tools. These approaches require an expensive sample preparation and a complex illumination to provide highly contrasted images and is therefore not suitable as an inline system. In addition, subjective parameters such as sharpness and contrast have to be adjust subjectively by trained employees and prevent a consistent quality assurance. A serious alternative are neural networks as they are able to analyze images very quickly and accurately without the need for high contrast images. In this paper we present a neural network that is able to classify low contrasted foam structures with a prediction accuracy of 90 %. On this basis an optical inline system is presented using the example of the value chain of a ceramic foam filter that ensures the quality of each filter across the entire value chain.
Study Of The Effect Of Process Parameters On Fiber Length, Fiber Orientation And Tensile Strength Of Long Glass Fiber Reinforced Polypropylene Molding
Po-Wei Huang, March 2019
In this study, investigation of the effect of process parameters on fiber length, fiber orientation and tensile strength of long glass fiber reinforced polypropylene molding. In the study, the polypropylene composite material with glass fiber length of 25 mm was taken as the research object. The special long fiber injection molding machine was used to investigate the change of fiber quality, and the injection molding experiment was carried out with different screw speed and back pressure, and observation on the fracture condition of the fiber during the plasticization process, using this as the basis for the process parameters setting. A tensile test specimen mold with different melt flow path was designed to understand the effects of process parameters on tensile strength properties of long fiber injection molding. It can be found from the experimental results that in the fiber breaking length experiment using the three-stage with plunger mechanism of the special injection molding machine for long fiber reinforced thermoplastic composite molding, increasing the screw speed and the back pressure will shorten and break the fiber (retain 40~50% of the fiber length). The length of the fiber further affects the tensile strength of the molded specimen. On the other hand, as the melt temperature and mold temperature increase, it affects the fluidity and compatibility between melt and glass fiber, the tensile strength will have a relatively increased trend. From the microstructure observation showed that the tensile specimen closer to the gate has poor fiber diffusibility and affects the tensile strength of the molded specimen; moreover, the tensile specimen with double gate melt flow path resulted lower weldline strength.
Application Of Transfer Learning Of Cae To The Training Of Neural Networks Of Different Injection Products
YANMAO HUANG, March 2019
A neural network has the advantages of high accuracy and fast speed in numerical prediction, and its disadvantage is that a large amount of training data is required for network training. There is a great variety of injection molding products, and the neural networks of various products cannot be shared directly. Therefore, each prediction module needs to take up a lot of time to make the training data, meaning that the prediction module cannot be applied to an actual injection molding mold trial. This research imported the concept of transfer learning to retrain the well-trained neutral networkarchitecture and hyperparameter according to the training data of similar products and to explore the effect of form and structure of training data on the accuracy of transfer learning. This research used 2 models of a circle plate and square plate to transfer the well-trained circle plate model to be used by the square plate. The research results showed that the Random Shuffle method for data pre-processing can improve the overfitting problem in addition to reducing the error rate of prediction. The prediction of complicated warpage is the most obvious. In the training of the circle plate, the error of gate warpage fell from 29.85% to 19.90%. When the Random Shuffle method is used in combination with the square plate model of transfer learning, the error rate of warpage also fell from 59.61 to 31.05. Keywords: Injection Molding, CAE, BPNN, Machine Learning, Transfer Learning
Metallurgical Comparison Between The Two Main Types Of Additive Manufacturing Methods Used To Produce Conformally Cooled Plastic Injection Molding Dies
NORMAN HUBELE, March 2019
Powder metal “printed parts,” using 3-D additive manufacturing (AM) methods using selective laser sintering (SLS, also known as SLM for “Selective Laser Melting”) of metal powders run under argon, have been widely tried by many plastic injection molding die manufacturers with only limited success. Injection molds manufactured using 3-D powder bed SLS AM methods typically suffer from poor material properties (particularly low ductility and early fatigue crack failures) and porosity. As a result, SLS has only found limited usefulness as either a tooling design aide or for very small batch part prototyping programs. Fundamental surface physics, associated with adsorbed air and water vapor bound to the surface of most commercially available powder metals is believed to be partly responsible for the formation of local oxides on the surface of the grain boundaries formed during SLS performed under argon atmospheres. The overlay of multiple layers of thin oxide films formed repeatedly on the grain boundary surfaces of SLS sintered structures substantially contributes to parts having lower part ductility and reduced fatigue properties. SLS printed parts typically become much more brittle and are subject to premature cracking. The “in-situ” oxide inclusions formed also contribute to both the low part density and hermeticity issues experienced with 3-D AM printed components, but local variations in the printing technique still drive most of the structural porosity issues being experienced. Traditional injection molding dies fabricated using wrought materials that are diffusion bonded using the “Laminated Object Manufacturing” (LOM) method do not suffer from the same uptake of oxygen at the grain boundaries during the liquid interface diffusion (LID) bond joining of the mold body. As a result, these dies do not suffer from the low ductility and early fatigue life failures seen with SLS printed injection molding dies, and often have fatigue lives three orders of magnitude higher than for parts SLS printed under argon.
Simulation Of Flow Through An Injection Molding Machine Non-Return Valve; Influence Of Material Parameters
Reinhard Fechter, March 2019
In this investigation the flow of a thermoplastic polymer melt through the non-return valve of an injection molding machine was simulated using the Finite Element Method (FEM). Only the dosing step of the injection molding cycle was considered. The simulated results showed that as expected an axial pressure flow is induced within the non-return valve. The corresponding pressure differential can be used to determine a simulated pressure at the entrance to the non-return valve. An analysis of the change in the relevant material parameters, in this case the parameters for the Bird-Carreau-Yasuda viscosity model; 𝜂0, 𝜆 and 𝑛, showed that a change in the zero viscosity 𝜂0 effects the pressure differential but not the velocities or shear rates whereas 𝜆 effects the shear rates without having a significant effect on the pressure and the velocities provided that shear thinning (the extent of which 𝜆 directly effects) is present. If shear thinning is present 𝑛 has a similar effect on the simulated results as 𝜆.
Performance Of Minerals In Polyamide 6
Saied Kochesfahani, March 2019
A study has been conducted to evaluate the performance of wollastonite, talc and mica minerals in comparison with chopped glass fiber in Polyamide 6. The results reveal special attributes to minerals that could be beneficial depending on the specifications required for desired applications. These include the best balance of properties for HAR wollastonite in specimens with melt flow weldline, and for HAR mica and talc where isotropic properties and best cross-flow performance are desired. Talc also significantly increases PA6 crystallization temperature, while both talc and wollastonite improve the melt rheology of PA6 formulations compared to chopped glass fiber.
Scalable Production Of “z” Aligned Ultra-Sensitive, Transparent And Flexible Piezoelectric Pressure Sensors And Loudspeakers
Armen Yildirim, March 2019
Here, we report a novel method to produce dual-functional ultra-sensitive, flexible and transparent piezoelectric pressure sensors and high performance loudspeakers. The key innovation of this technology is based on electric field induced alignment of piezoelectric Lead Zirconate Titanate (PZT) nanoparticles along with Graphene Nanoplatelets (GNPs) in a polymer matrix. The electric field alignment not only improves the piezoelectric response but also provides transparency for applications such as flexible touchscreen interfaces and also significantly reduces the amount of filler required to obtain high piezoelectric output. The ultra-sensitivity of the resulting material is demonstrated by the detection of a 1.4 mg bird feather. Apart from its sensing capabilities (direct piezoelectric effect), it can also operate as a high-performance transparent loudspeaker when a certain voltage is applied across the material (indirect piezoelectric effect). A 10 ft long large-area sample is also prepared to demonstrate the scalable production of the system via a novel roll-to-roll (R2R) manufacturing line which was also designed and developed by our group.
Non-Linear Rheological Response As A Tool For Measuring Dispersion In Nanocomposites And Blends
Thomas Ellingham, March 2019
Polypropylene (PP) was blended with polycaprolactone (PCL) and nanoclay (NC) in a twinscrew extruder (TSE) using a traditional extrusion process or a sub-critical gas assisted process (SGAP). Impact, morphology, and X-ray diffraction (XRD) properties indicated a smaller PCL phase droplet size and an increase in dispersion of the NC when SGAP was used. Standard small amplitude oscillatory (SAOS) rheological tests for storage modulus G’ were not sensitive enough to discern the difference between the traditionally extruded and SGAP samples. Fourier Transform rheology was used to determine the intrinsic non-linearity Q0, which was able to distinguish the added dispersive and mixing capabilities of SGAP. Practical implications of SGAP and Fourier-Transform (FT) Rheology are discussed.
Dual-Mode Viscoelasticity For Polymer Melts
Donggang Yao, March 2019
Polymer melts containing entangled chains of high molecular weight and high polydispersity typically show a distinct power-law relaxation region prior to a terminal relaxation region. It is difficult to describe this multiplex property using the generalized Maxwell model unless a large number of fitting modes are used. In this paper, we propose to establish relaxation models directly in the Laplace transformed s-domain, by defining constraints or admissibility conditions for acceptable transfer functions for modeling the multiplex entanglement effect. This leads to a single-mode relaxation modulus with only four model fitting parameters. In combination with a normal Rouse relaxation mode to describe initial short-range structural relaxation, the resultant two-mode relaxation model is found to fit realistic linear viscoelastic material functions and holds a promise for modeling nonlinear deformation of polymer melts.
A Novel Small-Diameter Eggshell Membrane/Tpu Double-Layered Vascular Scaffold With Wavy Structure
Shujie Yan, March 2019
In this study, a double-layer, small-diameter vascular scaffold mimicking the wavy structure and mechanical properties of native blood vessels was developed. It was found that eggshell membrane (ESM) could provide an extracellular matrix (ECM) environment for human umbilical vein endothelial cells (HUVEC) in vitro. The avian eggshell membrane has a fibrous structure and has long been utilized in Chinese medicine for recovery from burn injuries and wounds in Asian countries. Therefore, ESM is expected to be an excellent natural material for biomedical use. However, its low mechanical properties have hampered its use in scaffold applications. Herein, we use synthetic thermoplastic polyurethane (TPU) fibers combined with ESM via electrospinning using a wavy cross-section rotating collector. The purpose of combining these two materials was to leverage the bioactivity of ESM with the tunable mechanical properties of TPU. The circumferentially wavy biomimetic configuration provides the scaffolds with a sufficient toe region and the capacity for long-term use under repeated dilation and contraction.
Low Emission, Uv Stabilized Lasermarkable Pom For Automotive Interiors
Bruce Mulholland, March 2019
Laser marking on plastics is growing in use. Barcodes and product lot data can currently be marked with lasers some commodity resins. However, of specific interest is the use of lasers to mark functional or decorative information on engineering resins. Because of their inert surface characteristics, these resins can be difficult to mark via printing using ink. This paper focuses on the development of specialty grades of engineering resins that yield excellent sharp, clear images when laser marked. Grades have been developed for laser marking white characters on black, dark characters on white and other effects.
Molecular And Morphological Parameters Governing Yield Behavior Of Polyethylene Pipe Materials
Andrey Buryak, March 2019
The ductile behavior of PE in Region I of the pipe failure regime is mainly governed by the time / and temperature-dependent yield stress of the polymer [1]. Two different deformation mechanisms are relevant in PE. One governing shorter times and/or lower temperatures and the other longer times and/or higher temperatures which is relevant for the long-term ductile failure behavior of PE pipes. For the former, clear structure-property relationships were elaborated in literature. However, for the latter hardly any work was performed. This paper presents an accelerated method to characterize the ductile failure of PE pipes and tries to identify its limits and applicability. Furthermore, as a first attempt the structures of three model PE pipe grades are linked to their long-term ductile failure properties.
Novel V/P Transfer Actuation Method And Injection Molding Strategy And Their Comparison To Traditional Methods
Brad Johnson, March 2019
The use of one novel and three well-known injection strategies were investigated to determine the effect on variation in part weight for each when variation in material viscosity and check ring leakage were introduced to the process. In addition, a comparison was made of the use of traditional screw position, cavity pressure sensing, and a novel switch closed by the melt front to actuate v/p transfer with each of the processing strategies. Velocity to pressure transfer when the part was not quite full (2-stage, pack with second stage), after the part was packed with a fast velocity (2-stage, pack with first stage), and after the part was packed with a slow velocity (3-stage) were the well-known injection strategies evaluated. The novel strategy was a modified 3-stage where the v/p transfer was actuated after the first velocity (as in 2-stage, pack with second stage) and the pack velocity was set as the limit during the first profile of the second stage of injection. It was found that the modified 3-stage process reduced variation compared to traditional 3-stage and that the novel switch used to detect the flow front was the most consistent method to actuate v/p transfer.
Evaluation Of Novel Switch To Detect The Melt Flow Front In Injection Molding
Brad Johnson, March 2019
A cost effective filling control device was designed, prototyped, and evaluated in an attempt to reduce variation in the quality of injection molded parts. The patent pending method consists of an internal switch that is actuated by the melt flow in the cavity. A four run full factorial DOE was carried out for each of the V/P transfer methods that were compared: screw position, cavity pressure, mold surface temperature, and the new in-mold switch (MeltSwitch™). The part weight was measured to determine how each method was affected by viscosity and decompression variation. It was found that the mold surface temperature and MeltSwitch™ performed the best in minimizing part weight variation.
Wet Compounding Of Cellulose Nanocrystals Into Polylactic Acid For Packaging Applications
Ronald Sabo, March 2019
Cellulose nanomaterials have been demonstrated to improve the mechanical and barrier properties of various polymers, but numerous challenges, such as drying, remain to viably produce polymeric cellulose nanocomposites for packaging applications. In this paper we describe a method for drying and blending cellulose nanocrystals into polylactic acid (PLA) using a single process referred to as wet compounding. Aqueous suspensions of CNCs were directly compounded with PLA in a thermokinetic mixer in which viscous heating creates sufficient temperature to evaporate water and melt polymers during mixing. Here, CNCs with and without lignin were compounded with PLA followed by cast extrusion to produce films, which were evaluated for their mechanical and barrier properties. Composite films with de-lignified CNCs produced through wet compounding were found to have improved mechanical and barrier properties compared to neat PLA, whereas lignin-containing CNCs did not improve the barrier properties of PLA. The process of rapid wet compounding was not found to detrimentally affect the properties of PLA controls. In addition, using a discharge temperature setpoint well below the melting point of polymer resulted in the most favorable composite properties, indicating that further optimization and investigation of wet compounding is needed. The use of novel processing, such as wet compounding, has tremendous promise for advancing the viability of cellulose nanocomposites.
'Advancements In Aspects Of Automotive Anti-Scratch'
Barbara Syvy, March 2019
Slip additives have been used to reduce friction in films, aid mold release, and facilitate the application and removal of closures. Mono-unsaturated fatty acid amides, such as erucamide and oleamide, are traditionally used for high slip application. At modest dosing, these additives provide high slip performance at low addition levels, typically below 0.5%. However, these products are prone to breakdown due to prolonged exposure to UV light, high ambient temperatures, and oxidation. Croda determined there was a need for a more stable slip additive that does not reduce in performance over time. Incroslip™ SL is Croda’s latest innovation in slip additive technology. Through the course of two case studies it was found to provide excellent stability over time, which benefits to extended shelf life and cost savings, and optimum torque release and application performance through dosing HDPE via a LDPE masterbatch.
A Composition-Morphology Mapping Of Fumed Silica Filled Polymer Blends
Derrick Amoabeng, March 2019
We explore the effects of adding fumed silica particles to blends of two immiscible homopolymers, polyisobutylene (PIB) and polyethylene oxide (PEO) across a wide range of composition. Blends of PIB and PEO with fumed silica loading up to 10 vol% were studied. The fumed silica has strong affinity for PEO, and hence, when there is enough PEO to fully engulf the particles, a combined phase of fumed silica-in-PEO is formed. Due to the fractal-like nature of fumed silica particles, this combined phase can be strongly solid-like even at low particle loadings. We observed two morphological changes different from what was observed in spherical particulate filled in polymer blends studied in the past. The first is that, at low loadings of fumed silica, a huge qualitative change was seen in the morphology of the polymer blends. More specifically, particle-free blends that showed a dispersed phase microstructure often became cocontinuous upon adding particles. The second is when fumed silica together with the PEO formed a combined phase, a capillary aggregates network survived across a wide range of composition at 10vol% fumed silica loading.
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