Hello and welcome to a new blog post. In this post we are comparing glass-fiber filled PET vs. PBT, especially heat distortion properties (HDT). We dive into why PET's higher stiffness, heat resistance, and lower water uptake can be a game-changer for E&E and metal replacement applications. It can help you to elevate your material selection process - let us get started!
PET compounds vs PBT compounds
When it comes to high-performance engineering plastics, glass-fiber reinforced compounds of PET (Polyethylene Terephthalate) and PBT (Polybutylene Terephthalate) are often top contenders. While both offer enhanced strength and rigidity, their distinct properties can make one a clear winner over the other for specific demands.
One of PET's significant advantages lies in its higher stiffness, which directly translates to reduced creep under sustained loads. This superior mechanical integrity ensures long-term performance where dimensional stability is critical. Furthermore, PET compounds boast a notably higher heat distortion temperature (HDT). Specifically, when measured with HDT/B, PET can exhibit a delta of up to 20°C higher than PBT, making it more resilient in high-heat environments (Figure 1).
Figure 1: Comparison of HDT/A and HDT/B of PET-GF30 and PBT-GF30
Another crucial differentiator is PET's lower water uptake. This property directly contributes to better dimensional stability, as the material is less prone to swelling or warping in humid conditions. In the realm of electrical and electronic (E&E) applications, glass-fiber filled PET truly shines due to its good dielectric properties and the potential for achieving high UL RTI (Relative Thermal Index) values. These characteristics ensure reliable insulation and performance at elevated temperatures.
These combined attributes—superior stiffness, higher heat resistance, better dimensional stability, and excellent electrical properties—make glass-fiber filled PET compounds particularly compelling for demanding applications in the E&E industry. They are also an excellent choice for metal replacement, offering a lighter, often more cost-effective, and corrosion-resistant alternative without compromising on critical performance metrics. When designing your next component, understanding these nuances can lead to superior product design and longevity.
Hello and welcome to a new post. For many of us, LEGO® bricks are synonymous with durability and endless creative possibilities. They withstand countless builds, deconstructions, and even the occasional barefoot step. So, when a childhood treasure, carefully preserved for decades, suddenly crumbles in your hands, it's a stark reminder that even the most robust plastics have a lifespan. This is precisely the experience my friend Dirk Moses recently encountered with his 1986 LEGO® "Mobile Recovery Vehicle" set, and it offers a fascinating case study into the world of plastic part failure, particularly in ABS.
Dirk's story is a familiar one: a nostalgic journey with his son, building a cherished set from his own youth, only to be met with the disheartening sound of "crack!" as original, seemingly well-preserved parts disintegrated. No sunlight, no moisture exposure – just the relentless march of time. This isn't just a frustrating experience; it's a prime example of how polymers, even when seemingly inert, undergo subtle changes that can lead to catastrophic failure over extended periods.
Figure 1: Broken ABS bricks of the LEGO® "Mobile Recovery Vehicle" set from 1987 [1].
The Material Culprit: ABS and Its Vulnerabilities
The iconic LEGO® bricks are predominantly made from Acrylonitrile Butadiene Styrene, or ABS. ABS is a terpolymer, meaning it's made from three different monomers (check my detailed review on ABS here):
Acrylonitrile (A): Provides chemical resistance, rigidity, and hardness.
Butadiene (B): A rubbery component that contributes toughness and impact strength.
Styrene (S): Offers rigidity, processing ease, and gloss.
This combination gives ABS its desirable balance of properties – stiffness, impact resistance, and a good surface finish – making it an ideal choice for durable toys like LEGO®. However, it's the "Butadiene" component that often holds the key to its long-term degradation.
The Invisible Enemy: Thermal Oxidation of Butadiene
While Dirk meticulously stored his LEGO® set away from sunlight and moisture, he couldn't escape the effects of thermal oxidation. This is a common degradation mechanism in polymers, where oxygen from the air reacts with the polymer chains, often accelerated by even ambient temperatures over extended periods.
The butadiene component in ABS, with its unsaturated double bonds, is particularly susceptible to oxidation. Here's a simplified breakdown of what happens:
Initiation: Heat and oxygen initiate the formation of free radicals on the butadiene backbone. These free radicals are highly reactive.
Propagation: These free radicals react with more oxygen and then abstract hydrogen atoms from adjacent polymer chains, creating new free radicals. This forms a chain reaction, leading to the formation of hydroperoxides and other oxidized species.
Chain Scission and Cross-linking: The hydroperoxides are unstable and can decompose, leading to further free radical formation. This ongoing process results in two primary detrimental effects:
Chain Scission: The polymer chains break down into smaller fragments. This leads to a reduction in molecular weight and a loss of mechanical strength, making the material brittle and prone to cracking.
Cross-linking: In some cases, the free radicals can also react with each other to form new covalent bonds between polymer chains, leading to excessive cross-linking. While some cross-linking can increase stiffness, excessive cross-linking makes the material extremely rigid and brittle, also reducing its ability to absorb impact.
In the case of Dirk's 40-year-old LEGO® bricks, it's highly probable that the butadiene in the ABS underwent significant oxidation. This would have caused the once tough and resilient material to become brittle, explaining why parts that felt solid suddenly "cracked" under minimal stress. The internal structure of the plastic had been fundamentally altered at a molecular level, even without external stressors like UV light or repeated use.
The Takeaway for Polymer Engineers and Consumers Alike
Dirk's experience is a valuable lesson for polymer engineers and consumers alike. For engineers, it underscores the critical importance of understanding long-term material degradation mechanisms, even in seemingly stable polymers. Accelerated aging tests are crucial, but real-world shelf-life data, like Dirk's, provides invaluable insights. Developing new additives that can better inhibit thermal oxidation in ABS and other polymers is an ongoing area of research.
For consumers, it's a gentle reminder that even our most cherished plastic possessions have a finite lifespan. While storing items in their original packaging and away from harsh conditions can certainly extend their life, it cannot stop the slow, inexorable march of molecular degradation. During material selection, understanding all the requirements and transforming them into proper part specifications is key to prevent part failure at a later stage.
Dirk's spontaneous shift to a new LEGO® Dreamzzz set for his son, and the "priceless" joy it brought, highlights a beautiful truth: while the physical bricks may crumble, the spirit of play and connection that LEGO® fosters endures, bridging generations even when the plastic sometimes falls apart. And perhaps, for Dirk, his new mission to "quality control" his "Wrinkle Knights" castle will offer further valuable data in the ongoing saga of plastic longevity!
Many thanks to Dirk for sharing with us his experiences!
Hello and welcome to a new rule of thumb post. Today we discuss how to select the optimal PET grade (fiber vs sheet vs bottle grade) for your application.
Figure 1: Selecting the optimal PET grade
PET Intrinsic Viscosity (IV; dL/g) as a Key Indicator for selection and quality
Polyethylene terephthalate, or PET, is a ubiquitous polymer in our daily lives, from clothing to packaging. John Rex Whinfield and James Tennant Dickson, British chemists, are credited with inventing polyethylene terephthalate (PET) in 1941. They patented the material while working at the Calico Printers' Association of Manchester, building upon early research by Wallace Carothers. By using an aromatic diacid, properties of the resulting Polyester could be improved. This was the major start of PET which became the foundation for synthetic fibers like polyester, Dacron, and Terylene, as well as bottles, and sheets.
But not all PET is created equal. The key to its diverse applications lies in its Intrinsic Viscosity (IV), a crucial measure of its molecular weight and, consequently, its strength and processing characteristics. This is especially vital when utilizing recycled PET. Figure 2 shows the different process steps in PET production, including the IV obtained at every stage and the resulting potential applications.
Figure 2: PET process technology and the importance of Intrinsic Viscosity (IV) [4].
Application-Specific IV Ranges
For yarn and fiber applications, where flexibility and drape are paramount, PET with an IV between 0.6 and 0.7 dL/g is preferred. Moving up the scale, 0.7 to 0.8 dL/g PET is ideal for sheet applications, offering the necessary rigidity for thermoforming.
The familiar PET bottles we see daily, typically created through injection moulding into preforms, require an IV of 0.8 to 0.85 dL/g to ensure robust performance. For demanding uses like water jerry cans, where extreme durability is essential, PET with an IV greater than 0.85 dL/g is selected.
Summary of the PET IV ranges:
Yarn & Fiber (0.6-0.7 dL/g)
Sheet (0.7-0.8 dL/g)
Bottle (0.8-0.85 dL/g)
Jerry Cans (> 0.85 dL/g)
Choosing the correct IV grade is fundamental for achieving optimal product performance and ensuring efficient processing, highlighting why precise PET grade selection is critical for quality and sustainability across industries.
Hello and welcome to a new blog post in which we discuss the benefits of incorporating Life Cycle Assessment (also referred to as Life Cycle Analysis; LCA) into your plastic product design.
What is a LCA and why is it important?
LCAs are part of the holistic Life Cycle Engineering (LCE) approach and quantify the environmental impacts of plastic products across all stages of their life cycle, including raw material extraction, manufacturing, transportation, use, and disposal or recycling. One can analyze "cradle-to-cradle", where the end of a lifecycle is taken as the end of the recovery process or focus only on "cradle-to-grave", where the end of lifecycle is the disposal of post-consumer plastic waste. In addition, there is also "cradle-to-gate", where the end of lifecycle is taken to be delivery of the product at your factory gate (Figure 1). Altogether, a LCA provides a comprehensive picture of the overall environmental burden associated with a plastic part, allowing designers to identify areas where improvements can be made.
There are two major standards helping to bring a LCA to reality:
ISO 14040: providing the principles and framework.
ISO 14044: provides the roadmap on how to make the LCA. It provides information on the four steps a LCA should contain in order to systematically be able to quantify the environmental impact.
Figure 1: Overview of Polymer Life Cycle Engineering (LCE) and Life Cycle Assessment (LCA).
What are the four stages of a LCA?
Following is a brief description of the four stages of a Life Cycle Assessment (LCA), which should help you understand the process (Figure 1):
1. Goal and Scope Definition: This initial stage defines the purpose and breadth of the LCA study. It clarifies the product system being assessed, its functions, the intended application of the results, and the audience. This step also outlines the system boundaries, functional unit, and data quality requirements.
2. Life Cycle Inventory (LCI): This stage involves collecting data on all inputs and outputs associated with the product system. This includes raw material acquisition, energy consumption, manufacturing processes, transportation, use phase, and end-of-life treatment. The LCI aims to quantify all relevant environmental exchanges, such as resource use and emissions.
3. Life Cycle Impact Assessment (LCIA): In this stage, the environmental impacts associated with the inventory data are evaluated. The LCIA aims to translate the LCI results into environmental impact categories, such as climate change, ozone depletion, acidification, eutrophication, and resource depletion. Different LCIA methods are available, each with its own set of impact categories and characterization factors.
4. Interpretation: The final and crucial stage involves analyzing the LCI and LCIA results to draw conclusions and make recommendations. This stage assesses the significance of the results, identifies key environmental issues, and evaluates the consistency and completeness of the study. The interpretation should provide clear and transparent conclusions that address the defined goal and scope of the LCA.
The single stages can be supported by software solutions such as GaBi (Sphera) or Echochain.
What are the benefits of incorporating LCA into your plastic product design?
Currently, over 80% of the product's environmental impact is determined at the design stage. Integrating Life Cycle Assessment right from the design phase of plastic products can unlock some really significant advantages. Here are five key benefits for you to keep in mind:
1. Reduced Environmental Impact: LCA allows you to identify environmental hotspots and by considering the entire life cycle – from raw material extraction to end-of-life disposal – during design, you can actively choose materials and processes that minimize environmental burdens. This includes lower greenhouse gas emissions, reduced water and energy consumption, and decreased waste generation. For example, opting for recycled plastics or designing for easier recyclability can significantly lessen the environmental footprint.
2. Enhanced Resource Efficiency: LCA encourages designers to think critically about material usage and optimize product design for longevity and repairability. This can lead to using less material overall, extending the product's lifespan, and facilitating component reuse or remanufacturing. Think about modular designs that allow for easy replacement of worn-out parts rather than discarding the entire product.
3. Cost Optimization: While the initial LCA might involve some investment, it can lead to significant cost savings in the long run. By identifying resource-intensive stages or materials with high price volatility, designers can explore more cost-effective alternatives. This could involve using less expensive but equally functional materials, replacing metal by high performance polymers, streamlining manufacturing processes, or designing for efficient logistics and waste management.
4. Improved Product Performance and Innovation: The insights gained from an LCA can actually spark innovation and lead to better-performing products. Understanding the environmental constraints and material properties throughout the life cycle can drive the development of novel polymeric materials, innovative designs for durability and functionality, and even new business models like product-as-a-service.
5. Stronger Brand Reputation and Stakeholder Engagement: In today's environmentally conscious world, companies that demonstrate a commitment to sustainability through practices like LCA often build stronger brand loyalty and attract environmentally aware consumers. Transparently communicating the environmental performance of products based on LCA findings can also enhance engagement with stakeholders, including investors, regulators, and the wider community.
6. Informed Decision-Making: By providing a quantitative assessment of environmental impacts, LCAs help designers make more informed choices about polymer material selection, design features, and end-of-life strategies. This can lead to the development of more sustainable plastic parts with a reduced environmental footprint.
7. Comparing Alternatives: LCAs can be used to compare the environmental impacts of different plastic types, manufacturing processes, and end-of-life management options, helping designers choose the most sustainable approach. This can lead to the development of plastic parts that are not only functional but also environmentally responsible. As an example, Figure 1 compares the Global Warming Potential (GWP) and density of different plastics.
8. Supporting Circular Economy and Waste Reduction: LCAs are valuable tools for promoting a circular economy for plastics by helping to identify opportunities for reuse, recycling, and remanufacturing. By understanding the full life cycle of a plastic part, designers can create products that are more easily recycled or repurposed, reducing waste and promoting a more circular approach to plastic production.
Example of a LCA: Packaging
A LCA was done on 10,000 units of 12oz packages produced in different materials in the United States [10]. In the stage four, (interpretation), a contribution analysis was done, in order to understand the Global Warming Potential (GWP) of the different packaging materials. This in turn allows for better decision making, when the aim is to reduce the product carbon footprint of the packaging material.
Figure 2 presents the comparison of the GWP of aluminum can, glass bottle and PET bottle. By switching from glass bottle to PET-bottle, a 50% reduction in GWP can be achieved.
Figure 2: Comparison of GWP of a 12oz bottle made out of glass, aluminum and PET [10].
Conclusion
In conclusion, LCAs are essential tools for promoting sustainable plastic part design by providing a comprehensive and quantitative understanding of the environmental impacts associated with plastic products throughout their life cycle. By using LCAs, designers can identify hotspots, make informed decisions, and develop more sustainable and eco-friendly plastic parts that contribute to a circular economy and a healthier planet.
Often, a full LCA is not needed, it is better to make a simplified one and focus on one or two key outputs, than to have no LCA done at all.
Want to deep-dive into designing a sustainable future with polymers? Check out my talk on this topic:
Curious about how Life Cycle Assessment can revolutionize your plastic product design process? Do you have questions about its implementation or the benefits it can unlock? I'd love to hear from you. Contact me here to start a conversation and discover the possibilities.
Hello and welcome to a new post and today I present to you 4 tips for effective polymer material selection. In the realm of plastic product development and engineering, the selection of the appropriate polymer material stands as a pivotal decision, directly influencing the functionality, durability, cost-effectiveness, and overall success of the final product.
Navigating the vast landscape of available plastics and their diverse properties can feel like traversing a complex terrain. To ensure optimal outcomes, a structured and thoughtful approach is paramount. This guide illuminates four essential tips that will empower engineers and designers to make informed and effective polymer material selections, laying the groundwork for robust and reliable applications.
Let us geht started!
1. Requirement Analysis
Map out the true part functions, load cases, and material requirements.
Consider industry standards for properties like flammability, thermal, and electrical characteristics.
Include qualitative properties such as haptic perception and optical qualities.
These tools provide documentation and help understand decisions made by others.
Conclusion
Mastering the art of polymer material selection is an ongoing process of learning and refinement. By diligently applying these four tips – thorough requirement analysis, insightful questioning, maintaining a resin-neutral perspective, and leveraging decision-making tools – you can significantly enhance the effectiveness of your material choices. Embracing this structured approach not only leads to better performing and more cost-efficient products but also fosters a deeper understanding of material science and engineering principles within your team. Ultimately, the thoughtful and informed selection of polymers is a cornerstone of innovation and a key driver in creating successful and sustainable solutions for a wide range of applications.
Ready to begin your journey to Polymer Mastery? Take the Polymer Material Selection scorecard today and discover your POMS score!
Hello and welcome to this new post, today in the theme of Star Wars, together with polymer material selection.
FindOutAboutPlastics.com presents: The Path to Polymer Selection Mastery - A Jedi's Journey.
The path to becoming a master of polymer material selection is a challenging one, requiring dedication, perseverance, and a deep understanding of the Force, or in this case, the properties of plastics. Just as a Padawan must undergo rigorous training and face numerous trials to become a Jedi Knight, so too must an aspiring polymer engineer navigate a series of challenges to master the art of material selection.
This journey begins with a thorough understanding of the fundamental principles of polymer science, including the various types of polymers, their structures, and their unique properties. It is akin to a Padawan learning the basics of lightsaber combat and the Force. From there, the aspiring engineer must delve into the intricate details of polymer behavior, exploring how different polymers react under various conditions, such as heat, stress, and chemical exposure. This is similar to a Padawan mastering the subtle nuances of the Force, understanding its power and limitations.
The next step involves applying this knowledge to real-world applications, selecting the most suitable polymer for a specific purpose. This is where the true test of skill lies, as the engineer must weigh various factors, such as cost, performance, and environmental impact, to make the optimal choice. This is analogous to a Jedi Knight facing a dangerous mission, where they must use their knowledge and skills to overcome obstacles and achieve their goal.
Finally, the journey culminates in mastery, where the engineer can seamlessly integrate their knowledge of polymer science with their understanding of engineering principles to create innovative and sustainable solutions. This is akin to a Jedi Master, who has achieved enlightenment and can use the Force for the greater good.
In essence, becoming a master of polymer material selection is a continuous learning process, requiring a combination of theoretical knowledge, practical experience, and a deep understanding of the challenges and opportunities that lie ahead. It is a journey that demands dedication, perseverance, and a willingness to embrace the unknown, just as it does for a Padawan seeking to become a Jedi Master.
The path to polymer mastery may be arduous, but the rewards are great. Those who persevere will gain the ability to shape the future, creating products that are not only functional but also sustainable and beneficial to society. So, embrace the challenge, hone your skills, and embark on your journey to polymer mastery.
Ready to begin your journey to Polymer Mastery? Take the Polymer Material Selection scorecard today and discover your POMS score!
Hello and welcome to a new post in which we explore the new flexible pultrusion technology introduced by Technoform. I met with Dirk Moses, Head Of Market Development, at the KPA fair Ulm, Germany, discussing their new pultrusion technology. Watch the whole video here and check out our previous interview series here.
Dirk Moses from Technoform (right in picture), together with Herwig Juster, discussing the new thermoplastic pultrusion technology at KPA Ulm, Germany.
Thermoplastic pultrusion: combining extreme strength with maximum cost-efficiency
Dirk explained to me their company's new thermoplastic pultrusion technology which was developed by Sindy Richter, Head of the Development Department at Technoform, and her team.
It is flexible in terms of material selection, allowing for the use of standard plastics such as polypropylene - PP, engineering plastics such as polyamides (PA6, PA66), and high-performance polymers. This positively impacts the properties of the pultruded profiles as well as their ability to connect to other plastic components. Furthermore, the fiber content can be varied depending on the specific application. The resulting products are characterized by a lower weight combined with high impact resistance and bending strength.
Thermoplastic pultrusion is an advancement of the classic pultrusion process, in which thermoplastics serve as the matrix material instead of thermosetting resins. In both processes, continuous fibers are impregnated with plastic to ensure optimal force transmission through the connection of adjacent fiber elements. A key challenge in thermoplastic pultrusion is the high viscosity of thermoplastics compared to the lower-viscosity thermosets, which makes fiber impregnation more difficult. To address this challenge, Technoform has developed a special process for thermoplastic melt pultrusion.
Potential applications
Furthermore, Dirk highlighted significant potential in sectors prioritizing lightweight construction and recyclability, particularly the automotive industry for components like battery casings and structural reinforcements. Other promising applications include façade elements using recyclable thermoplastics and opportunities within the sports and furniture sectors where lightweight and flexible materials are advantageous.
Figure 1: Herwig and Dirk discussing profiles, façade elements, and automotive battery casings.
What about recycling of pultruded profiles?
Dirk emphasizes the technology's benefits over thermosets or aluminum, citing recyclability, material adaptability, and the ability to reshape or weld thermoplastic products. Their approach enables customized material combinations to meet specific requirements more effectively than aluminum. Regarding recycling, he explains that their pultruded profiles can be shredded and reused as high-quality components, with the retention of long fibers enhancing the mechanical properties of the recycled material.
Metal replacement
In terms of economic viability, Dirk asserts that their technology presents an attractive alternative, especially when replacing steel or aluminum parts with intelligent system solutions that incorporate integrated functions, lightweight design, and recyclability, leading to both sustainable and economic advantages.
Thanks to Dirk and the team for the exchange on the new thermoplastic pultrusion technology!
Hello and welcome to a new Rule of Thumb post on plastics processing. In my previous post we discussed how to locate the maximum shear rates by using injection moulding fill simulations. Now we explore what shear rate limits we need to consider to not harm the processed polymer.
Rheology of polymers
Plastics exhibit non-Newtonian fluid behavior, where viscosity is dependent on the applied shear rate. In certain polymers, shear rate exerts a more significant influence on viscosity than temperature.
Under high stress conditions, such as during processing, polymer molecules align, leading to a substantial reduction and stabilization of the resin's viscosity. This phenomenon is known as shear thinning.
Injection moulding and shear rate / stress limit of polymer melts
In injection moulding, the injection rate or fill time directly correlates with the shear rate experienced by the plastic material. Fill time is a critical process parameter that affects shear heating and shear thinning.
Variations in fill time can alter the viscosity, pressure, and temperature of the polymer within the mould cavity, ultimately impacting the quality of the final part. Maintaining a consistent, optimized fill time is therefore crucial for process stability across different machines.
Excessive shear rates can induce polymer degradation, resulting in a decline in both the aesthetic and mechanical properties of the moulded component.
The shear rate within specific mould geometries, such as sprues, runners, and gates with a round cross-section, can be calculated using the formula:
γ˙=4Q/Ï€r^3, where γ˙ represents the shear rate (1/s), Q (mm^3/s) is the volumetric flow rate, and r (mm) is the radius of the channel.
Shear stress and shear limit control table
Calculated shear rate values can be compared against established material-specific shear rate limitations to identify potential processing issues related to excessive shear. This data facilitates the mathematical determination of optimal flow rates and mould design considerations. Your calculated shear rate should not exceed the shear rate limit for the material. Figure 1 shows the shear stress and shear rates limits of different plastics, based on empirical experiments and literature.
Figure 1: Shear stress and shear rate control table.
Conclusion
In plastics processing, maximum shear rates can reach over 10,000 s⁻¹ in injection moulding and 1000 s⁻¹ in extrusion, with even higher rates (exceeding 1,000,000 s⁻¹) occurring in specific applications like wire coating. Calculating the shear rates of the material during processing and checking if they are below the shear rate limit of the material will lower the risk of polymer damage. Furthermore risk of plastic part failure is reduced since the part will have the desired properties.
More Rule of Thumb posts can be found in the "Start here" section.
Hello and welcome to a new post. Today I would like to start with a quote of mine:
"Nature is built on 5 polymers. Modern life is built on over 200 different polymers. Therefore, optimal polymer selection is key for successful applications and to prevent plastic art failure in the long run."
"Nature works with 5 polymers," is a statement from Mrs. Janine Benyus and reflects a key concept in her advocacy for biomimicry. It highlights the efficiency and elegance of natural systems compared to human industrial processes. Here's a breakdown of what she means:
Polymers in Nature:
Polymers are large molecules made up of repeating smaller units. They are the building blocks of many materials. Nature primarily uses a limited set of these polymers to create a vast array of structures and functions.
These "five polymers" generally refer to:
Cellulose: Found in plant cell walls, providing structural support. Cellulose was used in the past to create one of the first human made plastics: Celluloid. It is made by mixing nitrocellulose and camphor.
Chitin: Forms the exoskeletons of insects and crustaceans, as well as fungal cell walls.
Lignin: A complex polymer that provides rigidity to plant cell walls, particularly in wood.
Proteins: Versatile polymers that perform a wide range of functions, from structural support to enzymatic activity.
Nucleic acids (DNA and RNA): Carry genetic information.
Benyus's statement encourages us to look to nature for inspiration in materials science.
By mimicking the way nature uses these polymers, we can create materials that are:
Stronger
More durable
More sustainable
Easier to recycle.
In essence, "Nature works with five polymers" is a powerful reminder of nature's ingenuity and a call to action for us to learn from its wisdom.
Modern life is built on over 200 different polymers - How to select the right one?
An important step in the selection journey are the mastering of the what i refer to as the 6 Polymer Material Selection skills (6 POMS skills; Figure 1):
P - Part Design: Defining Application Requirements for Plastic Part Design
P - Polymer material values: Translating application requirements to qualitative and quantitative material values
P - Process: Polymer material selection process
P - Performance: Evaluation of material and part performance
P - Plastic supplier: Selection of material and supplier
Figure 1: Overview of the 6 Polymer Material Selection skills.
Check out the detailed description of the 6 POMS here.
In order for you to assess where you are currently ranking at the 6 POMS skills, I created a simple scorecard consisting out of 26 Yes / No questions and after completing the questionnaire, you receive an overall POMS score and detailed scores for each of the six critical elements of polymer material selection.
Also, you get a customised report with actionable steps to immediately start improving your POMS score and your impact in the field of polymer material selection.
A quick 5-step selection guide
Selecting the optimal thermoplastic material can be challenging and my aim is to provide you with a practical guide which leads you fast through the selection journey.
Improper selection of plastics for the application is the leading cause for plastic part failure and since most parts fail along weld lines or knit lines, optimal mould design including filling and processing of the part are crucial too.
Apart from the 200 polymers, there are almost 100 generic “families” of plastics and additionally blending, alloying, and modifying with additives results in 1,000 sub-generic plastic types. Also, selecting the wrong polymer for your product may result in additional financial resources, since the selection process needs to be repeated (including making new tools) or even worse, product failure leads to claims and recalls. The following guide will help you to prevent the major mistakes and if you want to be sure, you can always reach out to a plastic expert to review your selection or help you to select the optimal grade.
1. Define Application Requirements: In the first step we lay out all the application requirements and focus on Function, Loading Conditions, Environmental Factors, Regulatory Requirements, and Processing Considerations. A suitable acronym for this step is called FLERP: F- Function; L- Loading conditions; E - Environmental Factors; R- Regulatory requirements; P- Processing requirements.
2. Identify Candidate Materials: Based on your application requirements, research potential engineering plastics that possess the necessary properties. Material selection charts and dashboards, supplier websites, and technical data sheets can be helpful resources. Consider factors like: Mechanical properties (short- and long-term; as a function of time and different temperature levels), thermal properties, chemical resistance, electrical properties, processing characteristics, and cost.
3. Evaluate Material Performance:
Carefully review technical data sheets from potential suppliers to understand the specific properties of different plastic grades within a material family. Most of the time only a single temperature is covered (room temperature). This is useful for comparing different material data sheets to each other, however for part design it has its limitations. Also, consider Multipoint Design Data which helps to think in time-dependency and temperature-dependency behaviors. Graphically such behaviors can be better accessed. Utilizing CAE software to simulate the filling of your part as well as the performance of your design using different material options.
4. Additional Considerations: Consider processing methods and cost. Evaluate environmental and regulatory factors.
Consider the material availability in order to ensure the chosen material is readily available from reliable suppliers. Additionally, evaluation of the environmental impact of the material, including its recyclability or biodegradability, if applicable can be done. Long-term performance check is needed to check the material's resistance to degradation and expected lifespan in your application.
5. Testing and validation.
In the last step, prototyping is done. You can start by obtaining samples from material suppliers for simple analysis.
Next is to create prototypes using the previous identified candidate materials to test performance under real-world conditions. After concluding the final tests, final material selection can be done and a suitable supplier of the material chosen.
6. Bonus Consult with Plastic Experts and Material Suppliers:
Discuss your application requirements with experienced polymer engineers and material suppliers. Seek recommendations based on their expertise and access to the latest materials.
My Polymer Selection Funnel Method
For a more detailed selection approach, as mentioned before, I created the Polymer Selection Funnel methodology (POMS-Funnel). Figure 2 presents the four different stages of the material selection funnel as well as the tools we can use to facilitate the selection. We can use this as a guideline throughout the selection journey.
Figure 2: Overview of the Polymer Selection Funnel method.
Funnel stage 1: Material selection factors
In this first stage we map out the true part functions and material requirements. After this we translate the requirements into material selection factors.
Funnel stage 2: Decision on thermoplastic or thermoset
After translating the requirements into material selection factors, the first decision is made:
Which is the most suitable polymer chemistry to fulfill the listed requirements and selection factors? Thermoplastics or thermosets?
Funnel stage 3: Selection discussion with worksheet (qualitative matrix analysis)
The third funnel stage represents a core element in the whole material selection funnel. It is a detailed selection discussion with a worksheet. I call it the decision matrix analysis and it ranks all of the pre-selected polymers. The decision matrix analysis consists of five steps. The base calculation principle is a scoring of each of the pre-selected materials for each of the material selection factors. In the end we add up all weighted scores for each material. The material with the highest score is most suitable for selection and further investigation in the fourth stage.
Funnel stage 4: Testing, selection of material and vendor
In the last funnel stage, we would like to know in detail how the materials with the highest scores perform as a final part in a system of plastic parts or as a single plastic part alone. After all the tests are done and the material has passed all tests, commercial conditions with the material supplier can be finalized and first small serial production can start.
I created a dedicated page for Polymer Material Selection which contains all you need for your material selection, from taking the scorecard test, online selection tools, and examples which have used the POMS funnel method.
In material selection, there is no "one-size-fits-all" solution. The optimal material will depend on the unique needs of your specific application. A balance between performance, cost, and processing is often necessary. By following a five step guide or the POMS funnel method, leading to a thorough evaluation, you can make an informed decision and select the optimal engineering plastic for your project!
