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 part 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.
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| 5 Natural Polymers: Cellulose, Chitin, Lignin, Proteins and Nucleic Acids [1]. |
Biomimicry Application:
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- Properties: Understanding key polymer properties
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
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| Figure 1: Overview of the 6 Polymer Material Selection skills. |
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.
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| 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.
For better remembering all the Funnel stages, i created an acronym which plays directly on the word PLASTic, giving the methodology immediate domain recognition for polymer engineers:
P.L.A.S.T (Parameters, Logic Choice, Analytical Matrix, System Testing)
P — Parameter Definition (Stage 1)
L — Logic Choice: Thermoplast/Thermoset (Stage 2)
A — Analytical Matrix Analysis (Stage 3)
S — System & Vendor Testing (Stage 4)
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.
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| Sketchnote as a summary of the framework and post. |
Conclusion
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!
Thanks for reading and #findoutaboutplastics
Greetings
Literature:
[1] https://www.amazon.de/-/en/Janine-M-Benyus/dp/1094025003
[3] https://www.polymermaterialselection.com/
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