SPE Library

Revisiting the Sustainability of Flame Retardant Ethane Bis(pentabromophenyl): Assessing the Degradation Throughout its Lifecycle

Rajeev Mathur, March 2023

Photolytic and thermal degradation are important processes to the overall sustainability and environmental impact of a flame retardant for a given commercial application. Details on accelerated photolytic aging and recycling studies of ethane bis(pentabromophenyl) (EBP), often called decabromodiphenyl ethane (DBDPE), will be presented.

Effects of Ionizing Irradiation on Mechanical Properties of Polymeric Medical Devices

Md Kamrul Hasan, Ph.D., March 2023

The chemical and physical effects of ionizing radiation on polymeric materials is reviewed with a primary focus on radiation sterilization of disposable medical device materials.

Fundamentals of Foam Sheet Extrusion Using a Tandem Extrusion Line

Mark A. Spalding, John L. Sugden, Gary C. Welsh, March 2023

Tandem foam sheet extrusion is a complex process that requires optimization to produce quality sheet at high rates. The goal of this paper is to describe the process, show how rates can be increased, provide a guideline for sheet quality, and provide case studies.

A Novel Approach to Control Switchover Between Injection and Holding Phase for a Hydraulic Injection Moulding Machine

Rasmus A. Hertz, Jesper K. Christensen, Ole Therkelsen, Søren Kristiansen, Christian-Emil Helver, Frederik A. Hansson, Lasse Schmidt, March 2023

Simulating and Validating the Low Constant Pressure Molding Process, iMFLUX

Jay Shoemaker, Riley Browne, Mason Houtteman, March 2023

A new injection molding processing strategy called iMFLUX is becoming popular. iMFLUX is a low constant pressure process for filling and packing the part. Commercial injection molding simulation software traditionally is not designed for this process. However, you can simulate it. This paper will show how to set up and run simulations using currently available simulation software. Validation work of simulation work is also discussed.

Design for Sustainability — A Case Study with Appearance Nylon

Bruce M. Mulholland, March 2023

Material selection during the design phase can dictate a final part's ability to be recycled or not. This paper looks at an appearance part that transformed three different material solutions into a single material solution such that the final part was now recyclable and produced at lower cost. A look at the technical challenges and solutions to achieve this result is included.

Melt Rupture of Bimodal Molecular Weight Polyethylene in Simple Shear With Slip

M. Sattari, Y. W. Inn, P. M. Wood-Adams, March 2023

The melt rupture of a bimodal molecular weight distribution polyethylene is studied under simple shear with slip and time-to-rupture is analyzed. The time-to- rupture results show that there is a negative power law relation between the nominal shear rate and the time- to-rapture. The relationship between time to rupture and stress changes with the slip regime. Moving from weak to strong slip, there is a shift in the time-to- rupture curve down.

Digitalization — The Key for Circularity in Plastics

Christian Hopmann, Ph.D., March 2023

Outline

• Production, usage and lifetime of plastics by industry sector
• Circular economy
• The reality 2018: global plastics flow
• Options for plastics waste utilization
• Key action areas for sustainable use of plastics
• Ingredients of a nominal PE-LD recyclate
• Recycled material based on post-consumer packaging waste
• Value chain of packaging products
• DPP – Digital Product Passport
• Information exchange concept
• Scaling to industrial level
• AI based process model based on synthetic data
• Digitalization as enabler for robust and sustainable production
• Holistic approach towards a circular plastics packaging economy
• Conclusion and Outlook

Changes of Plastics Used in EVs Compared to ICVs & Why

Ashok Adur, Ph.D., March 2023

Electric vehicles have garnered a lot of interest and sales of these EVs are growing with many companies around the world producing them and entering the market besides Tesla. This presentation will cover changes in polymer usage in EVs compared to conventional internal combustion engine vehicles (ICVs). It will include: • Very interesting and unbelievable history of electric vehicles, • Plastics, elastomers, composites and other materials for light-weighting, • Changes in polymer materials and design needed for the several differences between the requirements of ICVs and battery electric vehicles (BEVs) and what factors led to these changes, • Use of recycled materials and sustainability, • Challenges BEVs faced, and how innovation overcame those challenges, and • Other challenges that remain and need more innovative approaches.

BlowView Simulation Tools for Design and Optimization of Thermoplastic Liner in Hyperbaric On-Board Hydrogen Storage Tanks for Mobility

Zohir Benrabah, Ph.D., March 2023

A key challenge to the widespread commercialization of fuel cell electrical vehicle, is to design compact and cost effective on-board Compressed Gaseous Hydrogen tanks which store sufficient quantities of H2 without sacrificing passenger and cargo space. The first generation of FCEVs use 700 bar Type IV pressure vessels to store hydrogen. These vessels have a cylindrical BMPL, overwrapped by carbon-fiber composite material to maintain the internal pressure, which serves as a hydrogen gas permeation layer. However, due to its small molecular size, H2 permeates through the plastic liner wall. This represents a serious issue that should be addressed early in the design stage in order to minimize H2 emissions from the liner and conform to legal safety requirements and standards. Meanwhile, automotive OEMs and their suppliers are being challenged to design longer and thinner liners with very consistent wall thickness. One way to meet the hydrogen permeation rate requires a judicious choice of liner material. In the thermoplastic forming industry, it is still common practice to rely on trial and error to find the appropriate barrier layer configuration/thickness required to meet the permeation rate limit requirement. A tool offering a more efficient alternative, based on reliable predictive/virtual analysis of the H2 diffusion through the BMPL wall, could significantly shorten the design/development cycle by allowing product prototypes to be analyzed and tested virtually. A finite element based model that could help a designer better understand barrier layer properties was integrated in the latest version of NRC’s BlowView software. The mathematical diffusion model adopted is based on Fick’s diffusion law to predict H2 diffusion through a polymeric wall. Promising results, in terms of H2 permeation rate on an industrial BMPL, will presented during the presentation.

Recycling of Polyvinyl Butyral From Automotive Windshield

Manoj Nerkar, Ph.D., March 2023

Polyvinyl butyral (PVB) is used in laminated glass to bind multiple glass layers. Key applications of laminated glass include safety glasses in architectural and automotive. Even if glass breaks, adhesive nature of PVB keep pieces of glasses together preventing human injury and damage to the surrounding. Because of this aspect of PVB, its used in automotive windshield applications. Each car windshield contains ~ 1kg of PVB. At the end of car life, glass in windshield is separated from PVB and recycled. In this study the PVB removed from glass was evaluated for its feasibility to recycle. Specifically, rigidity and indentation properties of PVB were studied. Substantial improvement in these properties was achieved by adding acrylic additives to PVB, making it suitable for applications such flooring. It was found that hardness of PVB was increased by addition of acrylic additives, resulting in improved indentation and rigidity. Glass transition temperature of PVB was increased by > 10°C. Significant increase in storage modulus was also observed. Effect of acrylic additives on tensile and impact properties are also presented. Being adhesive in nature, PVB tends to stick to metal surfaces making it difficult to melt process, addition of acrylic additive improved handling of PVB during melt processing preventing it from sticking to metal surfaces. Modification of PVB with acrylic enabled recycling of PVB in various applications, specifically flooring. With improved indentation and rigidity performance, use of PVB in flooring can be increased significantly. PVB modification can diverge >100,000 lbs. of PVB from land fill and can be used in value added applications. Acrylic modification showed potential to recycle PVB into useful applications making complete recycling of windshield possible, leading to overall improvement in automotive recycling.

Recycling of Airbag Wastes

Sinja Pagel, March 2023

Multi-layer materials (e.g. in packaging or technical parts) are used to achieve certain properties of products. However, a major challenge of plastics recycling is the separation of the various polymer layers. One example for this are airbags. Airbags consist primarily of polyamide 6.6 fibers and an additional silicone coating. To prepare for recycling, the wastes are processed to easily dosable fabric particles. However, the fabric particles subsequently do not consist exclusively of PA66, but still contain the silicone coating. In principle, it is possible to process these PA66 silicone fabric particles into plastic granules by extrusion, though this results in a product of low quality. This is mainly due to the low adhesion between the PA66 matrix and the contained silicone particles. The low adhesion leads to increased interfacial delamination and thus to premature failure. Mechanical properties such as impact strength or elongation at break are therefore very poor and high-quality technical components cannot be manufactured from this recyclate. An alternative to the extrusion of silicone-contaminated PA66 waste is the chemical separation of the silicone from the polyamide. However, the disadvantages of this recycling alternative are the large amounts of solvents required as well as the high energy requirements. Up to now, there is no efficient process for the mechanical recycling of PA66 wastes which contain silicone. However, from an environmental point of view and due to the large available amount of this type of waste (e.g. airbags), it would be desirable to process it into a high-quality recyclate which can be applied in the production of technical plastic components. Therefore, the aim of this work was to investigate a new approach for the recycling of PA66/silicone wastes using the example of airbag wastes. Thereby, the silicone particles should not be regarded as impurities but as a functional additive/impact modifier. To this purpose, a coupling between the PA66 matrix and the silicone particles was formed through a reactive extrusion in a twin-screw extruder by means of a silane coupling agent. This type of modification intents to reduce the risk of interfacial detachment in the resulting recyclate. After the reactive extrusion, an in-depth material analysis was conducted to verify the achieved coupling reaction in the twin-screw extruder. Rheological tests confirmed the formation of a cross-linked structure through the addition of the coupling agent. However, it cannot be determined through the rheological analysis if a chemical bonding has taken place. It can be assumed that the silicone has become inert during the airbag production and therefore none or only few functional groups are available. However, silanes and silicones have a basic structural similarity. Therefore, physical bonding can be expected, which may well lead to improved mechanical performance. The improved integration of the silicone particles into the PA66 and the reduction of cavities in the compound could be demonstrated by using Nano-IR-AFM analyses. Additionally, mechanical tests showed the increase in notched impact strength and elongation at break and therefore the possible function of the silicone as an impact modifier. The reactive extrusion process was further investigated in a hinged twin-screw extruder. After stopping the process, it is possible to open the processing unit and to take samples at different positions along the processing zone. This further analysis of the process emphasized the need for an adjustment of the machine parameters as well as the screw concept in order to optimize the reaction conditions in the processing zone and to prevent post-reactions as well as degradation effects. Future experiments will concentrate on the detailed investigation of the exact nature of the formed bonds (physical and/or chemical). In this context, the formation with additional silane types should also be taken into account. Furthermore, the process parameters of the reactive extrusion will be optimized with the aim to increase the additive content in order to further increase the notch impact strength while avoiding process-related post reactions that could hinder the processing of the compounds.

Novel Polyamide Solutions to Dampen Structural Vibration

Bradley Sparks, Ph.D., March 2023

A portfolio of innovative solutions has been developed that affectively address NVH and weight challenges of the EV market space. Significant advancements made in modeling, testing and correlation of the material properties to the part performance across frequencies. Ascend offers a wide range of products that address these goals from standard automotive grades up to our AVS High Damping grades.

Extrusion and Thermoforming of Flame Retardant, Halogen-Free, Glass-Filled Thermoplastic Composite Material for EV Battery Pack Applications

Anil Tiwari, Carlos Pereira, March 2023

Thermoforming is a widely employed technology for large part manufacturing, in part because of lower initial tooling costs and the suitability of this process for medium to low production volumes. Currently, the industry manufactures electric vehicle (EV) battery components predominantly through sheet metal forming. Though these solutions are relatively heavy and present challenges with respect to thermal and electrical insulation, lack of alternate mature large-scale manufacturing processes has kept sheet metal forming as the industry’s leading choice. The challenges and limitations of using conventional metal solutions for battery pack components such as top covers and bottom trays may potentially be addressed through the development of thermoplastic-intensive solutions. The incumbent large metallic battery enclosure applications present immense scope for significant weight savings, range extension and enhanced thermal runaway protection through use of thermoplastics. Furthermore, thermoplastics can deliver added benefits, such as increased functional integration, and enhanced thermal and electrical insulation, among others. Developing such solutions requires a holistic approach combining optimal design, novel thermoplastic material formulations and creative approaches for manufacturability. It also requires developing methods for validation at sub-system level. This study highlights novel thermoplastic composite materials – 30% glass-filled, intumescent, halogen-free, flame-retardant (FR) polypropylenes (PP) – used to manufacture an EV battery pack’s top cover, through sheet extrusion and thermoforming. The composite material was first extruded successfully into flat sheets at both pilot scale and commercial scale to exhibit its manufacturability. Next, the sheets were tested under different fire scenarios to assess performance of the material against thermal runaway conditions. Finally, the extruded sheets were thermoformed into multiple prototype geometries, from small to large-scale – to validate formability of the material for the top cover and enclosure pats of a large EV battery pack. Study findings demonstrate the feasibility of extrusion and thermoforming of the thermoplastic composite material for large-scale components with complex geometric features. In addition, tests show the potential of the enclosure made using the FR glass-filled PP material to withstand the thermal runaway conditions encountered in battery packs so they can meet the respective GB standards.C21

Parting Ways With PFAS Through Novel Fluorine-Free PPAs

Joshua Heidebrecht, March 2023

Due to the viscoelastic flow characteristics of polyethylene (PE) and the interaction of molten PE with metallurgy of a die surface, flow instabilities occur after exceeding a certain shear rate, temperature or mean velocity, which was initially discovered in 1958. This flow instability and melt fracture leads to an undesirable product appearance and can negatively impact product properties due to the emergence of a “sharkskin” morphology of produced film. In addition, melt fracture is one of the first instabilities that occurs at higher throughput, which can limit rates of commercial applications. Although the flow characteristics of polyethylene cannot be modified easily, specialty additives such as polymer processing aids (PPAs) can deposit on the die surface, inducing slip and enhancing flow. With this additional lubrication, die pressure can be lowered and the onset for melt fracture can be delayed, leading to significant commercial rate improvements. Fluoropolymers are ubiquitous within the field of PPAs for polyethylene and incorporate fully-fluorinated carbons to reduce interactions of the molten polyethylene and the die surface. While the efficacy of fluoropolymers to delay the onset of melt fracture is well described, the current regulatory landscape is progressing rapidly for the broad ban of perfluoroalkyl substances, which incorporates fluoropolymers. Although the chemistry and migration of fluoropolymers is quite different than that of perfluorooctanoic acid and perfluorooctanesulfonic acid which bans initially targeted, the current legislations are covering all compounds with at least one fully fluorinated carbon. Regarding plastic packaging, there are multiple states that have passed bans effective in 2023, with additional regulations going through the US and EU that come into effect within the next few years. For converters and film producers to maintain current rates and product morphology, new PFAS-Free technology needs to be developed and implemented within a very short timeframe. This presentation will provide insight into the mechanism at which processing aids lubricate the die and reduce melt fracture, cover academic and literature-based PFAS-Free PPA technologies and deliver an overview into the development of PFAS-Free PPAs at NOVA Chemicals. The performance of NOVA Chemicals fluorine-free PPA technology and efficacy towards melt fracture clearing will be presented alongside the effectiveness of fluorine-free PPA to prevent die lip build up.

Novel Analytical Toolkit for the Development of Halogen Free Flame Retardant (HFFR) Polypropylene Compounds

Swaraj Paul, March 2023

Polymer materials are made fire resistant basically by controlling either the bulk properties of polymers i.e., the condensed phase or by controlling the gas phase chemistry i.e., the volatiles that are formed due to polymer degradation under burning conditions or by controlling both. This suggests that if materials could be designed with low specific mass loss rates under fire conditions, the amounts of volatiles formed would be substantially reduced resulting into less combustion and thereby less heat generation. The latter would result into less increase of surface or ignition temperature of the materials resulting into less thermal degradation of materials. This suggests that important parameters that control the condensed phase properties of polymers to make them fire resistant are surface or ignition temperature and the kinetic degradation parameters of the materials. Another parameter that has a great influence on the fire properties is the gas phase chemistry, which in turn, is controlled by the volatiles formed during the burning process. The volatiles formed differs both with respect to flammability and generation of heat of combustion. This suggests that both the total amount of volatiles and the chemical composition of the volatiles formed because of burning are important to improve fire resistance properties of the materials. Therefore, preferred volatile compositions are also presumed to be effectively improve the fire properties of the materials. Furthermore, in phosphorus (P) and Phosphorus-Nitrogen (P-N) based (PFR) halogen free flame-retardant systems, it has been suggested that formation of P and PO radicals in the gas phase are important to obtain good fire-resistant properties because they both function as effective radical quenchers and char formers resulting into less heat generation. For radical quenching presence of phosphorus in the form of P and PO radicals in the gas phase are important. This suggests that distribution of phosphorus both in the condensed and in the gas phase should play an important role in controlling the fire properties. This proposes that selection of suitable PFR compounds that renders a preferred P distribution in the gas and in the condensed phase is important to obtain good fire resistance properties. Unfortunately, quantitative estimations of the above-mentioned parameters are lacking in the literature. In this presentation, we shall present a toolkit to experimentally measure these parameters for different HFFR PP model compounds and their correlations to the UL94V results. The study shows that we obtain a good agreement between these quantitative parameters and UL94V tests. This suggests that our toolbox could be very helpful and effective tool both to characterize and develop new and effective HFFR formulations instead of using single point UL94V tests that are being commonly used today.

A Numerical Study on the Fiber Detachment affecting the Complex Stress State at Microstructural Level of Unidirectional Fiber Reinforced Plastics

Nicolas Rozo López, March 2023

The fatigue performance of unidirectional fiberreinforced plastics is subjected to complex damage mechanisms, dependency on the load direction, and straindependent material behavior. In addition, the strength of the fiber/matrix interface is one of the main influential fa ctors on the composites’ fa tigue life. Its characterization, however, is effortful and the results are prone to large scatter. Moreover, the microstructure within the composite leads to a complex stress-strain field that changes with each fiber break, or detachment. So far, this resulting internal stress-strain fields only have been possible to be investigated by numerical approaches. In this work, a single fiber break model was extended to a representative volume element model (RVE) within the finite element method. A composite material made of carbon fibers and epoxy resin is being investigated. The behavior of the two constituents is assumed to be orthotropic and isotropic elastic, respectively. The complex microstructure is represented by a random fiber distribution generated with a sequential expansion algorithm, and periodic boundary conditions are applied. The fiber strength is modeled as a Weibull-distribution. A parameter study is carried out to analyze the influence of the fiber/matrix detachment rate on the internal stress distribution. Principal Component Analysis (PCA) is introduced to reduce the dimensionality of the problem. The obtained results show that PCA can reduce successfully complex stress-strain fields to an eigenvalue and eigenvector problem. Furthermore, the simulations show that the fiber detachment length correlates with the number of load cycles.

Generation of Tough, Stiff Polycarbonate Nanocomposites Through the In-Situ Nanofibrillation of Rubber Network

Hamidreza Akrami, March 2023

In this study, we introduce the concept of in-situ nanofibrillation as an efficient, low-cost, and environmentally friendly tailored technique for the enhancement of polycarbonate (PC) properties. PC/ Ethylene Propylene Diene Monomer Rubber (EPDM)-fibril composites are prepared by a twin-screw extruder. Taking advantage of the crosslinked rubber phase as well as nanofibrillation processing play the main role in properties improvement. Modifications of the mechanical and rheological properties of PC via fiber-spinning of PC/EPDM are distinguished by elongation and crosslinked network of the second phase (EPDM) properly in the main matrix (PC). Morphological observations showed the well-dispersed fibrillar phase of EPDM with a high aspect ratio in the PC matrix. PC with nanofibrillated EPDM also improved the mechanical properties, especially the ductility and the toughness, while increasing the stiffness, in comparison with neat PC. The change in the tensile, Izod Impact and flexural properties was governed by the draw ratio. Hence, having stretched fibrils is an effective way to enhance the mechanical and rheological properties. Rheological investigations proved that PC with nanofibrillated EPDM has dramatically improved melt elasticity compared with neat PC. Linear viscoelastic behavior of small amplitude oscillatory shear measurements showed a strain-hardening, solid-like, behavior in the fiber-spun PC/EPDM, which was not observed in the neat PC or the melt-blended PC/EPDM.

Smart Foams Generated via Supercritical Carbon Dioxide

John Daguerre-Bradford, March 2023

Natural and synthetic polymeric foams display a variety of open and closed pores with diverse shapes, sizes, and degrees of anisotropy. In state-of-the-art foaming processes, microcellular anisotropy is generated by releasing confinement in one or more directions during the expansion of an initially isotropic melt or resin. As a result, the entire monolith foamed in this way exhibits cells aligned in the direction dictated by the confinement. This, in turn, results in a uniform deformational response that is dictated by the loading condition relative to the microcellular orientation. In this work, investigation was performed into generating a foamed morphology within an anisotropic medium (e.g. film or fiber) to understand how molecular orientation affects the resulting anisotropy in the microcellular structure. Additionally further investigation into the use of this strategy to generate complex microcellular hierarchical constructs was performed by using fibers and or films as templates to understand their effect on the corresponding deformation. Herein, results are presented to show how assemblies of fibers are woven or twisted with a bias or helical structure and then foamed using superheated water (shH2O) and/or supercritical carbon dioxide (scCO2) to manufacture complex microcellular structures. In addition, results from mechanical tests also show how the imposed bias in the foams result in complex deformation imposed by the bias. That is, foams generated to create a helical bias are shown to undergo torsional deformation commensurate wit h uniaxial deformation when compressed uniaxially. These concepts propose a technology to manufacture “smart foams” by assembling templates (films and/or fibers) that have locally different molecular orientations that ultimately create locally changing anisotropic microcellular patterns that govern complex deformational behavior under applied loads.

Micro/Nano-layer Structured Foams With Tunable Foam Morphology and Properties

Patrick Lee, Ph.D., March 2023

In the frame of polar, deep water, and exoplanet exploration, lightweight multifunctional materials with durability targeting extreme environments are highly sought. Specifically, mechanical strength and a high degree of thermal insulation are among the most critical properties of structural materials in these applications. Mechanical strength imparts the structural integrity needed to minimize damage to sensitive electronic components, while thermal insulation is needed to protect equipment in extreme temperature conditions. Herein, this work uses micro/nano-layered technology to fabricate film/foam alternating structures for an advanced structural architecture that combines the mechanical performance of multilayered materials with the thermal insulation properties characteristic of polymer foams. We used PC as the film layer, PMMA as the foam layer, and CO2 as the foaming agent. With respect to foam structure, our work demonstrates that due to the confinement effect of the film layers, samples expand only in the thickness direction with no noticeable expansion along the in-plane direction. The apparent expansion ratio in the thickness direction increases with increasing layer numbers (up to 513 layers), ranging from 2.3 to 11 times expansion. With respect to cell morphology, there is a clear decrease in cell size with increasing layer numbers, with a concomitant increase in cell density. Specifically, we obtain the highest cell nucleation density and smallest cell size, around 1.1×1013 cells/cm3 and 400 nm, respectively, from the 513-layer sample foam, when treated at 70 C and 20 MPa. This micro/nano-layered film/foam alternating system offers an outstanding combination of tensile strength (~33 MPa) and low thermal conductivity (~0.0297 W/m·K), in comparison to foams or aerogels with similar thermal conductivity and tensile strength of less than 1 MPa. The balanced tensile performance and insulation properties offered by this multi-tiered structure open the door for use in applications including the exterior layer of vehicles operating in extreme conditions.