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

Investigation Of The Induced Electric Field Molecular Alignment Of Sliver-Based Solvate Ionic Liquid (SIL) And Silver Nanoparticles (AgNPs) In A Toughened Epoxy Resin Composite

Ahmed Al-Qatatsheh, Anna Sokolova, Nishar Hameed, March 2023

We report using the coordinated silver (I) complex based on SIL in a toughened epoxy resin composite to enable electrical and thermomechanical properties. The toughened epoxy resin was aligned at the molecular level utilizing an electric field, demonstrating a relatively high electric conductivity, energy storage, and rapid curing behaviour that can save energy, reduce unnecessary heat, and optimize capital and operating costs. Applying Small Angle Neutron Scattering (SANS), our work thoroughly studied the effect of alignment changes on the silver (I) complex and AgNPs under an applied electrical field and assessed the stability of the alignment after the electric field was constantly removed. Furthermore, the in-situ SANS investigation of the kinetic effects under external impulse influence helped identify the clusters of silver under an external electric field in various composite matrices. This technology can be used for accurate noninvasive blood circulation; increasing material electrical conductivity by applying induced electric field molecular alignment can tremendously increase sensor sensitivity. This approach opens the door to the next generation of thermoset polymers with multifunctional properties.

Direct Measurement of the Thermal Conductivity Depending on the Thermal Crystallisation Conditions of Injection Moulding processes Using Flash-DSC

Jonathan Alms, Hakan Çelik, Christian Hopmann, March 2023

During the production of injection moulded components made of semi-crystalline thermoplastics, the material is locally exposed to different thermal conditions and thermal histories. While in the injection phase the surface layer material that gets in direct contact with the cold mould wall solidifies at cooling rates of up to 700 K/s, the core layer material solidifies at cooling rates of ~1 K/s, especially for thick-walled components. This results in variation of crystallisation degree throughout the thickness of the component. Typically, an increasing crystallisation degree is related to an increase in thermal conductivity of a polymer. Since the heat of the whole component is transferred through the surface layers, where a low crystallisation degree is expected, the prevailing reduced thermal conductivity effects the injection moulding process significantly. To measure the crystallisation degree dependent thermal conductivity, a method using a Flash- DSC is presented and tested with isotactic polypropylene. To reduce effects of the Flash-DSC measurement itself a large parameter sweep is used to calibrate the measurement instrument. Using the Flash-DSC, however, delivered an inverse relation of thermal coefficient and crystallisation degree which contrasts with literature, which expects a direct proportional relation.

Mass Spec Solutions for Polymer Analysis

Mark Arnould, March 2023

Mass Spectrometry (MS) has become an indispensable tool for polymer analysis and has been widely used to study polymer structure and composition, end-groups and additives, molecular weight distribution, degree of polymerization, and so on. MS analysis is extremely sensitive, allowing the detection and identification of minor polymer components and synthesis by-products, as well as low-level impurities and products of decomposition. Matrix Assisted Laser Desorption Ionization (MALDI) MS is a well-established method of polymer characterization that continues to be developed and improved with new generations of MS instruments, bringing new analytical capabilities and enhanced performance. Modern MALDI-MS instruments generate rich chemical information highly specific for polymer structural analysis, copolymer composition and complex polymer mixtures characterization, and can even be used for imaging of synthetic polymer surfaces. Because of its unique capabilities, this technology has been widely used in a great variety of polymer analysis applications in both academic and industrial settings. In some cases, MALDI-MS is the only technique that can provide the information required to solve a practical problem. It allows for rapid MS analysis where no prior sample treatment or extensive separation is needed, including characterization of challenging insoluble polymers. TIMS technology has redefined the capabilities of Ion Mobility separation by providing an unmatched combination of resolution, speed, robustness and sensitivity. In polymer analysis applications, the timsTOF instruments expand the analytical boundaries by combining the TIMS technology with ultra-high-performance MS and providing an additional dimension for separation of complex polymer mixtures and structural analysis of challenging polymer compositions. Compatible with HPLS-ESI, GC-APCI and MALDI workflows, Bruker timsTOF fleX is a go-to multitool for a modern polymer lab.

Analytical Characterization to Evaluate Coating Efficiency of Fertilizers

Praveen Boopalachandran, March 2023

There are unique opportunities to develop coatings for non-urea fertilizers and provide desired performance such as enhanced controlled nutrient release and dust resistance. The key contributions from this work; provided advanced analytical solutions to evaluate fertilizer coating quality and developed quantitative QC tools for nutrient release and dust resistance. In conclusion, developed hydrophobic polyurethane fertilizer coating solutions that provides significant shelf stability and controlled nutrient release.

Failure Analysis of Glass Fiber Reinforced Plastics

Jeffrey Jansen, March 2023

The strength that glass reinforcement can impart to plastic materials is phenomenal. Glass fiber reinforced plastics offer enhanced mechanical properties, particularly strength and stiffness over unfilled materials. Their use is widespread in a wide variety of applications where mechanical integrity is essential. However, this benefit is not without its challenges. This presentation will focus on the investigation of failures of components manufactured from glass fiber reinforced plastics. The goal of a failure analysis is to identify the mechanism and cause of the component failure - to distinguish how and why the part broke. This presentation will explore the challenges unique to glass fiber reinforced materials and techniques that can be used to gain the maximum information from these failures.

Rheo-Raman Spectroscopic Study of Flow-Induced Crystallization of Polyethylene

Takumitsu Kida, March 2023

We developed a rheo-Raman spectroscopic system by combining a Raman spectroscope and rheometer to investigate the flow-induced crystallization behavior of polyethylene. Conformational changes that occurred during the flow-induced crystallization such as the formation of consecutive trans sequences or crystalline structure can be detected using Raman spectroscopy. We confirmed that no crystallization takes place at 130 ºC without shear flow because the fraction of the consecutive trans sequences and the crystalline structure was almost zero for 60 min. In the case of the flow-induced crystallization at 130 ºC with a shear flow of 100 s-1 for 30 s, the fraction of the long-consecutive trans sequences composed of more than 10 trans conformers increased with increasing time while the crystallinity was almost zero after applying the shear flow to the sample. Moreover, the long-consecutive trans sequences were formed as the precursor of the crystalline structure only at the shear rate with the Weisenberg number, which is the product of the shear rate and the Rouse relaxation time, greater than unity. These results suggest that the long-consecutive trans sequences are formed as precursors of the crystalline structure due to the stretching of the molecular chains under shear flow.

Investigating the Rapid Solidification Involved in Thermoplastic Processing Using Fast Scanning Calorimetry and Beyond

Xiaoshi Zhang, Ph.D., March 2023

Processing of thermoplastics during injection molding and blow molding usually includes rapid cooling with rates up to 103 K/s and solidification at high supercooling. Fast scanning calorimetry (FSC), an advanced calorimetry, is able to cover high processing rates and wide temperature windows by just using a few nanograms of the sample. With the advent of FSC, the crystallization fingerprint of many thermoplastics has been revealed. In this work, we expand the existing capability of FSC by coupling it with other techniques, including micro-IR spectroscopy (Micro-IR), atomic force microscopy (AFM), polarized optical microscopy (POM), and X-ray computed tomography (XCT). Polymorphism and morphology transition associated with processing conditions will be discussed in polyamide 66, polyamide 6, poly (ether ether) ketone and its composites. A more accurate simulation of plastic solidification can be achieved using fast scanning calorimetry and related technology.

Optimizing and Monitoring UV-Cure Process by DSC, DEA and DMA

Yanxi Zhang, Ph.D., March 2023

A variety of questions may arise in the UV-curing process of polymeric materials. For example, when does UV-curing start? When is UV-curing complete? What is the reactivity of the resin? What is the glass transition temperature after curing? Which photo initiator does show best performance? How does mechanical property of the cured material change in UV-curing process? Differential Scanning Calorimetry (DSC), Dielectric Analysis (DEA) and Dynamic Mechanical Analysis (DMA) offer effective means to help to answer these questions. DSC measures reaction enthalpy and degree of cure initiated by radiation. DEA allows for the measurement of changes in the dielectric properties related with ion mobility and dipole alignment during cure. Compared with DSC, DEA is good for fast cure system because data acquisition rate is less than 5ms and more sensitive to small change in cure process when close to the end of cure. DMA measures modulus changes during UV-curing process. These thermal analysis methods are indispensable in both R&D and quality control in the area of UV cure.

Compressive Behavior of Additively Manufactured Elastomeric Thermoplastic Polyurethane Honeycomb Structures With 2D Density Gradients

Mohammad Ahmed, March 2023

The advent of additive manufacturing (AM) brought in new dimensions to the research and development efforts of cellular polymeric structures by offering design freedom, resulting in tailorable architected structures optimized for specific applications. This work proposes a two-dimensional (2D) density gradient approach to design graded honeycomb structures for energy absorption applications. Graded honeycomb structures having three levels of density gradients (low, medium, and high) and their uniform density honeycomb equivalents were manufactured using material extrusion (MatEx) based fused filament fabrication (FFF) AM process. The material used for the FFF process was thermoplastic polyurethane (TPU) elastomer (Polyflex). The relative density of the structures was in the range of 0.259 – 0.346. A comparative study of the compressive behavior of the graded and regular honeycomb structures was carried out using in-plane quasi-static compression tests. Unlike regular honeycomb structures, all the graded honeycombs showed gradual stepwise deformation. Compared to their honeycomb equivalent counterparts, the high gradient honeycomb showed significantly different force-displacement profile compared to medium and low gradient honeycombs. While high gradient honeycomb showed higher maximum crushing force compared to the honeycomb equivalent, medium and low gradient honeycombs showed higher crush force efficiency. The experimental results were evaluated and compared with non-linear finite element analysis (FEA) simulation results. The hyperelastic properties of the TPU material were defined using Mooney-Rivlin constitutive model. The simulation results agreed well with the experimental results. The proposed 2D gradient parametric design methodology, coupled with the experimental and simulation results, can broaden the knowledgebase of graded honeycomb design principles, thus providing unique opportunities to develop and improve additively manufactured light-weight structures for commercial applications, ranging from automotive and transportation to healthcare and consumer products.

Structure Development of Semi-Crystalline Polymers in Laser Based Powder Bed Fusion

Simon Cholewa,,reas Jaksch, Dietmar Drummer, March 2023

The impact of melt hardening at low melt undercooling and under atmospheric pressure creates boundary conditions that have yet to be extensively studied since traditional techniques do not require such information. However, for powder bed fusion of polymers, the transition from the melt after exposure to an elastically dominant melt is critical as the crystallization in the building phase occurs under these conditions yielding stresses due to crystallization volume shrinkage. As a result, a process-adapted evaluation is required to determine how long the molten polymer remains viscously dominant, and the point where the stresses are stored in the melt. Therefore, the crystallization of semi-crystalline melt is investigated in this work using rheological data in conjunction with FTIR microscopy. A modified measurement setup of the rheometer with an ATR crystal allows a simultaneous description of crystallization by FTIR spectroscopy and measurement of the rheological behavior of the material. A comparison between the different techniques indicates that the increase in viscoelastic properties during crystallization begins at low degrees of crystallinity. It is determined that the solidification of the melt is detectable at relatively low degrees of crystallization conversion and that no stresses are accumulated in the material until this point.

Comparison of the Anisotropy of the Mechanical Properties of Injection Moulded and Additively Manufactured Parts

Johannes Austermann, Rainer Dahlmann, March 2023

Based on its mouldless, layer-wise manufacturing principle, screw-extrusion-based Additive Manufacturing (AM) allows for the efficient and economical production of thermoplastic prototype parts. During manufacturing, thermoplastic pellets are molten in a single-screw extruder and discharged through a nozzle. As the extruder is moved by a kinematic, the melt is subsequently locally discharged in a strand- and layer wise fashion to successively build up a part, similar to established AM processes such as the Fused Filament Fabrication (FFF). In contrast to FFF, standard thermoplastic pellets can be processed, as a single-screw extruder instead of a heated nozzle is used for plasticising the material. Thus, enabling injection moulding (IM) prototypes to be manufactured from series IM grade materials, including filled materials such as talc-filled polypropylene. However, the layer-wise additive manufacturing leads to anisotropic mechanical part properties in terms of strength and stiffness, which differ from the properties of the final IM-part, currently limiting the use of AM-parts to concept- and geometric-prototypes. These properties not only result from lower part strength orthogonal to the direction of deposition due to incomplete healing between adjacent strands, but also from a difference in filler-orientations, based on the process specific flow behaviour of the melt during processing. To extend the use of parts manufactured in screw extrusion AM to functional- or even technical prototypes, for which the mechanical properties are crucial, an understanding of these differences in the anisotropic mechanical behaviour of AM- and IM-parts is necessary. In the scope of this work, the quasi-static tensile and flexural properties as well as the high-speed tensile properties of additively, screw-extrusion-based manufactured and injection moulded parts are investigated, taking into consideration differences in the filler orientation between the manufacturing processes. To account for the anisotropy, testing is performed in several directions relative to the direction of deposition in AM or the direction of flow in IM. Furthermore, optical investigations are performed to assess the impact of filler orientations. The investigations are performed by manufacturing 1BA tensile test specimens from a 20 wt.% talc filled IM grade polypropylene material in screw-based AM and IM, which are subsequently used to perform quasi-static tensile and high-speed tensile testing. In addition, test specimens in accordance with DIN EN ISO 178 are manufactured for flexural testing. To allow for comparability, the test specimens are indirectly manufactured, i.e. both in AM as well as IM plate geometries are produced, from which the test specimens are milled. The AM parts are tested parallel and orthogonal to the strand-direction as well as at an angle of 30° and 60° relative to the strands. For IM, testing is carried out parallel and orthogonal to the direction of flow. In addition, µCT and microscopic investigations are conducted to analyse the orientation of the filler. While the results show an anisotropy in strength and stiffness for both IM and AM specimens, the anisotropy of these properties is significantly more pronounced in case of AM. This is based on the higher degree of filler orientation in the strands of the AM-parts. At the same time, only a partial orientation of the fillers in flow direction can be determined for IM-parts, showing that the fillers used can impact the comparability of AM and IM-prototypes. Additionally, it is shown that a higher comparability of the part properties is possible in the case of a quasi static load, compared to high-speeds of load application, limiting the use of AM-prototypes to such load cases.

Numerical Simulation and Experimental Investigation of the Flow Behavior in Material Extrusion Additive Manufacturing

Julian Kattinger, March 2023

The melting of a plastic filament in an FFF extruder is characterized by the fact that there is hardly any frictional heating, and instead heat conduction and radiation between the nozzle wall and the filament plays the major role. Experiments have shown that these heat transfer mechanisms limit material heating and thus the overall production rate. For this reason, many efforts have been made to capture the melting behavior of the filament through analytical models, numerical simulations or experiments. This presentation focuses on a CFD simulation of non-Newtonian and non-isothermal polymer flow through the nozzle of a fused filament fabrication printer. The simulations were performed for a wide range of filament velocities at different nozzle temperatures and then compared with two different types of experiments. A comparison with experimentally measurements of the force required to push the filament through the nozzle showed that the assumptions used for the simulations are suitable to predict the melting and flow behavior in the relevant processing range. In addition, an experimental method was used to allow in-situ observation of melt flow in a printing nozzle using X-ray micro-computed tomography. In this way, it was possible to study the velocity distribution in the nozzle and to gain insights into the melting mechanism that can be used for future modeling approaches.

Strategic Cost and Sustainability Analyses of Injection Molding and Material Extrusion Additive Manufacturing

David Kazmer, Ph.D., March 2023

Economic and environmental costs are assessed for four different plastics manufacturing processes, including stock and upgraded material extrusion 3D printers, as well as cold and hot runner molding. Characterization indicated the larger stock 3D printer had a melting capacity of 14.4 ml/h while the smaller but upgraded printer had a melting capacity of 36 ml/h. 3D printing at these maximum melting capacities resulted in specific energy consumption (SEC) of 16.5 and 5.28 kWh/kg, respectively, with the latter value being less than 50% of the lowest values reported in the literature. Even so, analysis of these processes found them to be only 2.8 and 3.5% efficient, respectively, relative to theoretical minimum energy requirements. By comparison, all-electric injection molding with a cold runner mold had a specific energy consumption of 0.205 kWh/kg and was 54% efficient relative to the theoretical minima. Breakeven analyses considering the cost and carbon footprint of mold tooling found injection molding provided lower costs at a production quantity around 70,000 units and a lower carbon footprint at a production quantity around 10,000 units. Parametric analysis of model inputs indicates that the breakeven quantities are robust with respect to carbon tax incentives but highly dependent on mold costs, labor costs, and part size.

Effective Wall Thickness for Computational Modeling of Polymer Extrusion Additive Manufacturing

Saratchandra Kundurthi, Mahmoodul Haq, Abdifitah Adan, March 2023

Polymer material extrusion additive manufacturing processes like fused filament fabrication (FFF) are increasingly being used for structural applications. Accordingly, there is a growing need for computational modeling to characterize and predict the process output and printed part performance under load. Prior studies have shown that the modulus and strength in the build direction (Z-direction) are sensitive to the surface bead shapes and can vary extensively depending on the print settings used. This presents a challenge for part-level (macro-scale) finite element analysis (FEA) because the material properties required for such models can vary from part to part or even different locations within the same part. The use of stress concentration factors is a critical step in computing effective material properties to be used in macro-scale numerical models. However, theoretical stress concentration factors (kt) published in literature for material extrusion AM are limited to tensile loading only. In this work, we demonstrate how the kt from tensile loading can be extended to other load cases. Meso-scale FEA was used to perform parametric studies with varying bead shapes. The models were subjected to pure bending loads as well as bending loads combined with shear loads. The stress concentrations were then evaluated, but with multiple iterations of the wall thickness used for nominal stress calculations. The results were compared to the results from pure tensile loading, and it was observed that the choice of wall thickness is trivial for tensile loads but is critical for bending loads. An equation for effective wall thickness was derived that yields consistent stress concentration factors for any bead shape, irrespective of the applied load. The results were also compared with the effective wall thickness for calculating the Z-direction modulus as published in literature. Ultimately, separate recommendations for effective wall thickness are presented for calculating modulus, strength, and the actual geometry used in macro-scale FEA models.

Dry Stereolithography

Manilal J. Savla, March 2023

Dry stereolithography is a new and patented process that uses thermoplastic photopolymers in film or sheet/plate form instead of liquid photopolymer resins and does not require support structures during the build process. The process generally relates to the use of dry photopolymers to make a 3D printed object formed from individually and selectively exposed dry photopolymer layers of the same or gradually varying shape. Suggested markets for dry stereolithography are outlined. Photopolymer plates/sheets/films as raw materials are environmentally friendly.

Simultaneous Processing of Thermosets and Thermoplastics in Additive Manufacturing of Multi-Material Polymer Parts

Robert Setter, Katrin Wudy, March 2023

Multi-material additive manufacturing (AM) pushes the barriers of complex part production with a comprehensive and complementary material spectrum to unprecedented heights. The experimental “Fusion Jetting” technology is one of the first attempts to simultaneously process thermoplastics and thermosets within a single AM process to functional multimaterial parts. Applications lie in the field of load-path optimized reinforcements, hard-soft and smart structures as well as the strategic variation of the mechanical, thermal, and electro-magnetic part properties. This investigation focuses on the implementation of UV-curable acrylates within thermoplastic polyurethane (TPU) parts utilizing an experimental laser-based AM process to specifically alter the mechanical behavior of future parts. Process parameters like the laser power or the acrylate content within each plane are strategically varied to examine their respective impact on the mechanical and microscopic part properties. Based on tensile testing results, an increase of the Young’s Modulus for TPU parts with acrylate reinforcements is detected. The choice of the sequence of the individual process steps proofs fundamental towards the laser/material interaction and the infiltration behavior. This includes the detection of increased infiltration of the acrylate within melted regions of TPU using low energy densities resulting in parts with increased porosity. The results are further discussed towards the bonding behavior between the materials, including the potential impact of selected process parameters on the visually detected delamination behavior during mechanical testing.

Characterization of Polyaryletherketone (PAEK) Filaments and Printed Parts Produced by Extrusion-Based Additive Manufacturing

Manuel Garcia-Leiner, Benjamin Streifel, Steven M. Kurtz, Daniel W. MacDonald, Cemile Basgul, March 2023

This study describes a detailed analytical characterization of polyaryletherketone (PAEK) polymers used in extrusion-based additive manufacturing. The results provide key observations and highlight differences between commercially available polymers of the PAEK family, specifically polyetheretherketone (PEEK) and polyetherketoneketone (PEKK). Results suggest that inherent differences in their molecular structure led to notable differences in terms of their viscoelastic, thermal and physical properties. Similarly, direct comparison of the properties between parent filaments and three-dimensional printed (3DP) parts suggests that, as observed in subtractive processes, the molecular structure of the PAEK polymer selected (PEEK or PEKK), as well as the inherent physical properties associated with it, determine greatly the performance of final 3DP parts. Differential scanning calorimetry results suggest that the glass transition temperature (Tg) of PEEK 3DP bars (146.8 °C) is about 8 °C lower than that of the parent PEEK filament (154.8 °C). These small differences manifest greatly in the viscoelastic response after Tg, and the temperature at which a decrease in storage modulus is observed occurs consistently at lower temperatures in 3DP PEEK bars (ca 130 °C) compared to PEEK filaments (ca 150 °C). In contrast, no observable differences are noted between parent filaments and 3DP bars in PEKK polymers. For these polymers, the inherent semi-crystalline behavior dominates their thermal and viscoelastic response. These structure–property relationships provide fundamental understanding to aid in the design and manufacturing of several industrial and biomedical applications that could potentially leverage the advantages of high temperature thermoplastic PAEK resins, as well as in the incorporation of these polymers in a growing number of technologies encompassing the field of additive manufacturing.

Powder Bed Fusion of Polymer-Based Separators for Solid-State Batteries

Katrin Wudy, Ph.D., March 2023

Powder bed fusion of plastics has reached a high maturity level up to now and the technology is used for different applications in the area of transport, consumer goods and for medical applications. Having a look at the area of energy storage systems mainly metal additive manufacturing techniques are used. The is an increasing need for innovative storage technologies, such as solid-state batteries, as well as novel production technologies. In this paper, a novel approach to manufacturing the so-called polymer separators for solid-state batteries with powder bed fusion is represented. Two different potential candidates for the polymer materials for the separator are analysed regarding their process behaviour in powder bed fusion. PEO and PVDF are commonly applied as materials for the solid-state separator. Optimal process parameters for the manufacturing of PVDF and PEO with powder bed fusion process to generate homogenous and dense layers are the key findings of this paper and provide deepened process understanding. As a result, the first proof of concept for producing separator layers by printing in a scalable process is shown.

Let AI Run Your Compounding

Saeed Arabi, March 2023

Compounding is a science. It requires a great knowledge of Chemistry, Formulation, Processing, Equipment and the Human Factor and most recently Artificial Intelligence. Compounders of today are facing many challenges that their predecessors did not face. Market fluctuation due to global issues, labor shortages as a result of pandemic, force majeure by raw material producers are few of many challenges facing compounders now. Purpose of this presentation is to show how you can use AI in your compounding operation and potentially increase your efficiency by at least 25%.

A Digital Twin for Setup Time Reduction in Single-Screw Extrusion of PVC Tubes

Enrico Bovo, March 2023

A Digital Twin (DT) can be defined as a digital representation of an actual physical system, where the data flow between the virtual and the real entity is fully integrated in both directions. In this work, a soft-sensor-based DT was developed for the real-time monitoring of the most important quality indexes in the manufacturing of plastic extruded tubes, i.e. the weight per unit length and the inner diameter. An extensive experimental campaign was conducted on a real tube extrusion line using three polyvinyl-chlorides (PVC) and different process conditions, and machine learning regression algorithms were trained and tested to create the models of the extruder and the extrusion die, on which the DT is based. The characterization of the considered material, whose properties were given as input to the digital models, was carried out according to a procedure based only on the data collected by the production line. The DT was tested for the startup of the production of a single-layer tube, and allowed to achieve the specified customer requirements (thickness and weight) in few minutes. The proposed solution thus proved to be a useful tool for reducing the setup time, thus increasing the efficiency of the process.