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

Using Thermal and Rheological Techniques to Help Guide Recycled PET Extrusion Processing

Tianhong Chen, Ph.D., March 2023

Polyethylene terephthalate (PET) is one of the most commonly used plastics in our daily life. It is completely recyclable and is the most recycled plastic in the U.S and worldwide. However, recycled PET from different sources may have large variabilities, such as reduced molecular weight, broader molecular weight distribution, different crystallinity, and containing different impurity contents, all of which can affect their processing and application. This presentation will discuss of using thermal and rheological techniques to fingerprint the feedstock resins and help guide extrusion processing. Specifically, we will discuss using differential scanning calorimetry (DSC) to identify the type of impurities, monitor the effect of thermal history on the crystallinity and crystal melting. We will also discuss using rheological techniques to estimate the molecular architecture, measure melt stability, melt viscosity, and help optimize extrusion conditions.

Exploiting Structure-Process Property Relationships of Branched Polycarbonates for Industrial Applications

Manojkumar Chellamuthu, Ph.D., March 2023

Current electrification market needs materials with good balance of Flow, Flame Property and Mechanical Performance. In this talk, we will discuss the rheological features of three commercially available linear, branched and hyper-branched polycarbonates (PCs) using comprehensive investigations. Applications of rheological properties to enhance Z-strength in Large Format Additive Manufacturing (LFAM) will also be discussed. Additionally, high temperature extensional Rheometer (CaBER) was used to understand the evolution of microstructure at high temperatures. The experiments were performed at temperatures ranging from T = 250 to 370 °C to a maximum Hencky strain of ten. At lower end of the temperature range, no significant degradation of the linear and branched Polycarbonate (PC) was observed either in the shear or extensional measurements. Beyond, T > 300 °C branched PC showed a dramatic increase in extensional viscosity which helps in Flame performance (anti-drip) better than its linear counterpart.

Confinement and Complex Viscosity

Steacy Coombs, March 2023

Whereas much is known about the complex viscosity of polymeric liquids, far less is understood about the behaviour of this material function when macromolecules are confined. By confined, we mean that the gap along the velocity gradient is small enough to reorient the polymers. We examine classical analytical solutions [Park and Fuller, JNNFM, 18, 111 (1985)] for a confined rigid dumbbell suspension in small-amplitude oscillatory shear flow. We test these analytical solutions against the measured effects of confinement on both parts of the complex viscosity of a carbopol suspension and three polystyrene solutions. From these comparisons, we find that both parts of the complex viscosity decrease with confinement, and that macromolecular orientation explains this. We find the persistence length of macromolecular confinement, ?? , to be independent of both ?? ?? and?? ?? 0.

Steady State and Dynamic Oscillatory Shear Properties of Carbon Black Filled Elastomers

Avraam Isayev, Ph.D., March 2023

A correlation between the steady shear viscosity and complex dynamic viscosity of carbon black (CB) filled rubbers was found by evaluating the Cox-Merz rule and an alternative approach originally proposed by Philippoff for dilute polymer solutions, but since applied to amorphous polymers and concentrated suspensions. This was done by measuring the rheological properties of 16 industrially important rubber mixes containing CB N660 at concentrations of 20 and 35 % by volume. A capillary rheometer at various shear rates and a dynamic oscillatory shear rheometer at small and large amplitude oscillatory shear (SAOS and LAOS) were used. The apparent viscosity, storage and loss moduli, complex dynamic viscosity and Fourier transform harmonics were measured. Generally, the shear stress, storage and loss moduli increased with increasing CB loading. Also, the ratio of 3rd and 5th stress harmonics to 1st harmonics increased with increasing strain amplitude and filler loading. Viscous Lissajou figures (shear stress versus shear rate) at a strain amplitude of 14% showed a nearly linear response for compounds containing CB at 20% by volume. All other shear stress responses demonstrated a strong nonlinearity. The stress waveforms at a strain amplitude of 140% for compounds containing 35% CB by volume displayed a backwards tilted shape expected for highly filled compounds. The stress waveforms at a strain amplitude of 1,000% tended toward a rectangular shape expected for pure polymer. Generally, the nonlinear response of the compounds appeared to be dominated by the filler at strain amplitudes of 14% and 140% and by the rubber matrix at a strain amplitude of 1,000%. The Cox-Merz rule was not applicable for any of the compounds with their complex dynamic viscosity being greater than the apparent viscosity. However, a modification of the approach proposed by Philippoff provided reasonable agreement between the apparent viscosity and complex dynamic viscosity.

Introducing a Differentiable, Shear-Thinning Viscosity Model

Paul Van Huffel, March 2023

A differentiable model for non-Newtonian, shear- thinning viscosity is presented as derived by integrating the log-log domain derivative function of the Carreau-Yasuda viscosity model. This work starts with the discovery of the log-log domain derivative function as this is the foundation for the statement of the new viscosity model. Potential uses for this work include development of explicit or hybrid flow solvers for polymer flows and possibly extending into the incorporation of effects based on the rate of change of the spherical (i.e. expansion/compression) and deviatoric parts of the rate-of-strain tensor, although this model specifically deals with the deviatoric part. A fitting experiment of rheometer data that was initially fit for each temperature curve as part of another work is used to demonstrate the flexibility of having a variable curve shape parameter as opposed to a fixed value, and a simulation of a conical section is used to compare the apparent wall shear rate in a converging channel versus the numerically obtained shear rate by a finite element analysis of the same conical channel.

Experimental Characterization and Modelling of the Pressure Dependence of the Viscosity for Injection Molding Simulations

Steffen Verwaayen, March 2023

The pressure dependence of melt viscosity of thermoplastic materials is difficult to measure and is therefore often neglected, although it can have a major influence on the results of an injection molding simulation. Current viscosity models provide the ability to model this dependence. Therefore, the viscosity is measured in a high- pressure capillary rheometer and the pressure dependence of the viscosity is determined in an online rheometer for a polypropylene. The generated experimental data is used as input to fit the Carreau-WLF model. The accuracy of the models varies depending on the input data chosen. In particular, the pressure dependence of the viscosity could not be correctly represented while maintaining good viscosity representation. A correction of the neglected pressure during the high-pressure capillary rheometer measurement improved the modeling of the pressure dependence of the viscosity slightly.

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