Friday 28 April 2023

Polymer Selection Funnel Example - Yoga Mat (Example Sporting Goods Market)

Polymer Material Selection Example - Yoga Mats

Hello and welcome to another polymer materials selection example using the Polymer Funnel methodology. In this post we discuss the material selection of the optimal material for Yoga mats. Figure 1 presents the four different stages of the material selection funnel and this overview serves us as a guideline.

Figure 1: The four different stages of the polymer material selection funnel.

Global sporting goods market

The global sporting goods market is a billion dollar industry and can be split into the following sections: 

  • athletic footwear
  • exercise equipment
  • licensed sports merchandise
  • and athletic apparel.

Sports clothes use plastic fibres such as Polyamide, Polyester, Acrylic, Lycra, and Spandex which make this segment leading in the use of polymers. Sports shoes use ethyl vinyl acetate (EVA) for the mid-sole to provide lightweight cushioning. Extra comfort for the insoles is provided by polyester foam padding. We see more and more recycling plastics used for shoes too. Also for stadium seats recycled plastic bottles can be used. Millions of recycled plastic bottles were used to make 6,700 seats for the MaracanĂ£ stadium at the Rio 2016 Olympics.

Polymer material selection for Yoga mats

Figure 2 shows a standard exercising Yoga mat which can be found in stores already. We will select the optimal material for such a mat.

Figure 2: Standard Yoga mat in green. 

Funnel stage 1: Material selection factors

In Funnel stage 1 we assess the yoga mat requirements and turn them into material selection factors:

  • Keeping thickness level of 4 mm (6 mm depending on type) over time
  • Lightweighting, considering different densities of materials (min. Density of 0.38 g/cm3)
  • Balance of comfort and stability
  • Length of min 180 cm 
  • Good surface texture
  • Hardness between Shore A 40 and 60
  • Colorability
  • Eco-friendly (no harm to environment) 
  • No allergic reactions to skin and easy cleaning
  • Price level

Table 1 summarizes the important requirement information with quantitative and qualitative values (requirement worksheet).

Table 1: Summary of important requirements and information of the Yoga mat project. 

Funnel stage 2: Decision on thermoplastic or thermoset

In Funnel stage 2 we decide between the thermoplastic and thermoset material route. Since we need soft surfaces together with cushion, thermoplastics are the preferred selection path. Additionally we consider rubber materials too. Proposed materials are Polyurethane (PU), Polyvinyl Chloride (PVC), Thermoplastic Urethane (TPU), and Natural Rubber (NR): 

-Elastopan CS 9530 (PU)

-Elastollan® C 60 A HPM (TPU Shore A 60)

-Vinnolit S4170 (PVC)

-NR A 560 (NR, Semperit Shore A 40)

Table 2 summarises the preselected polymers. 

Table 2: Summary of pre-selected polymers.

Funnel stage 3: Selection discussion with worksheet (qualitative matrix analysis)

In the third funnel stage we use the qualitative matrix analysis methodology to assess the suitability of the pre-selected polymers (Table 3). For starting, we insert the material selection factors from Table 1 in the top upper line and assign each a priority number (ranging from 0= low to 5= high priority). This is followed by adding the pre-selected materials. Now we rank each material how good it can fulfil the requirements listed in the top layer (5 = perfectly fulfilled). In the end we multiply the priority number of each requirement with the fulfilment number and add them up to a total sum. On the right side of Table 3 the results are listed. In our case, NR has the highest number (85), followed by TPU and PU (both 70), and PVC (66).  NR offers a good balanced density, haptic level, and is made from natural materials. TPU combines certain properties of NR and PVC and stands in the middle. The cheapest and more sticky solution for Yoga mats is PVC. For further mechanical testing, NR, TPU, and PU are considered. 

Table 3: Results of the qualitative matrix analysis for the Yoga mat material selection.

Funnel stage 4: Testing, selection of material and vendor

Now mechanical, chemical and other specific tests are done based on prototype mats. Auch tests can include potential customers too to receive their feedback if they feel comfortable with one of the materials. In the case of Yoga mats it is feasible to use 1-2 different materials since the customer preferences can be different. Some prefer natural based materials and others like the TPU and TPE based Yoga mats. 

Check out other polymer material selection examples: 

Polymer Material Selection Funnel Example - Baby Bottles (Consumer Packing Example)

Polymer Material Selection Funnel Example - Water Pipes for Plumbing (Building & Construction Example)

Polymer Selection Funnel Example - Vacuum Cleaner Canister and Canister Holding (Example Electronics Consumer Goods)

Thanks for reading and #findoutaboutplastics



Interested to talk with me about your polymer material selection, sustainability, and part design needs - here you can contact me 

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.







Thursday 13 April 2023

Mass Balance Approach for Plastics (ISCC) - A Concise Overview

Mass Balance Approach for Plastics (ISCC) - A Concise Overview

Hello and welcome to a new post where we discuss the basics of the mass balance approach for plastics. We touched on this topic in our previous posts and today we include some more examples too. 

Linear vs. circular economy

The linear economy consists of three major phases: produce, use, and waste disposal. The circular plastics economy also has three phases, however the waste disposal is replaced by recycling. Therefore we have to produce, use, and recycle.

Mass balance approach

The mass balance is a crucial step to enable the circular plastics economy. Essentially it is the production of polymers in a sustainable way by using alternative feedstocks (bio-based and recycled) and combining them with fossil-based feedstocks.

Bio-based can be bio-naphta which is a side product of the wood- and paper industry. Bio-based feedstoock can be obtained from bio-waste as well. Another bio-feedstock source is pyrolysis oil, generated by mixed plastic waste which is depolymerized back to their monomers. 

The plastics generated over this way can be ISCC (International Sustainability and Carbon Certification) certified and used to make new products. Another advantage is that you have virgin plastic quality and can use such polymers for engineering and high performance applications. 

Examples of the mass balance approach with plastics

A comparison of the renewable PC-Copolymer Elcrin HPX4B with the Lexan HPX4 PC-Copolymer shows that there is a 43% CO2 reduction achieved by using bio-based feedstock (IPCC Co2 equivalent analysis; LCA based on ISO 14040). 

Another example is the Bornewables™ polyolefin portfolio which allows to reduce the reliance on fossil-based feedstock by at least 73%.

In case you need support during polymer material selection to also consider ISCC certified materials, please feel free to reach out to me

More posts on the topic can be found here: 

Thanks for reading and #findoutaboutplastics


Herwig Juster

Interested to talk with me about your polymer material selection, sustainability, and part design needs - here you can contact me 

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.








Tuesday 11 April 2023

Guest Interview: Bianca Gubi – Product Manager Circular Economy at ENGEL Austria GmbH “Plastic waste is a valuable raw material. If we manage to keep it in circulation, we can protect our environment and our climate.”

Hello everyone and welcome to this guest interview. Today I present to you Bianca Gubi who is product manager Circular Economy at Austrian injection moulding and automation manufacturer ENGEL AUSTRIA GmbH. We have the chance to deep-dive into Circular Economy moulding, learn about the newly developed two-stage moulding process for recycled materials, and what to take care in design for recycling in injection moulding.

Enjoy the interview!

Guest Interview with Bianca Gubi, working as Product Manager Circular Economy at ENGEL Austria GmbH.  

1. Tell us about yourself, your current role, and your way into the Circular Economy and recycling.

I have been working intensively on the subject of the circular economy for five years now because it's also very important to me personally. Plastic waste is a valuable raw material. If we manage to keep it in circulation, we can protect our environment and our climate. As product manager for Circular Economy at ENGEL, I'm happy to be able to make an active contribution now. That’s something I really like about my work. Here in the Circular Economy Division, we focus on sustainable technologies and are committed to ensuring that recycled plastic waste can be reprocessed to create high-quality plastic products. As an injection moulding machine manufacturer, ENGEL is part of the plastics industry and takes its responsibility very seriously. We are continuously enhancing our machines and have a range of new technologies for the circular economy in our portfolio. As a product manager, I am responsible for the design and marketing of this technology portfolio. That means I analyse what our customers need and collaborate very closely with R&D to meet those requirements. 

2. What are the differences between regular injection moulding and Circular Economy moulding? And are there things which need to be handled with special attention?

For the injection moulding machine, it's more or less irrelevant whether you process granulate, that is, virgin material, or a regranulate, that is, recycled material. This is basically good news if you're looking to establish a circular economy, because it means that it's very easy to switch to regranulate in many applications. But two things, above all, are important if you want to achieve high product quality across the board. Firstly, the plasticising unit needs to be precisely matched to the properties of the material you want to process. ENGEL has a great deal of in-house plasticising expertise and produces all the plasticising units itself; this means that we can offer our customers fantastic support here. Secondly, when you are processing recycled material, you have to take into account that the material is exposed to more pronounced batch fluctuations than you are accustomed to from virgin material. We meet this challenge with smart assistance. For example, the iQ weight control smart assistance system can automatically adjust the injection moulding parameters responsible for quality to match the current conditions for each individual cycle and ensure consistently high component quality by doing so. For standard injection moulding, it is important for the regranulate to be single grade and free of impurities. And if there are impurities, our Circular Technology engineering helps to produce good parts anyway – with our new two-stage process for example. 

3. Can you tell us about the newly developed two-stage moulding process for recycled materials? And can you point to some of the benefits of processing flakes directly compared with ready-to-use recycled pellets? 

Thanks to the new two-stage process, ENGEL makes it possible to process plastic waste as flakes in injection moulding directly after grinding. Since this eliminates pelletising, as a separate and particularly energy-intensive, process step, this innovation significantly improves energy- and cost-efficiency in plastics recycling.

To be able to process flakes in injection moulding, we have broken down plasticising and injection into two independent, but mutually tuned, process steps. In the first stage, the raw material, for example plastic flakes originating from post-consumer or post-industrial collection, is melted in a conventional plasticising screw. The melt is transferred to a second plasticising unit for injection into the cavity. Depending on the material and application, a melt filter and a degassing unit can be integrated between the plasticising and injection units; this allows customers to create high-quality products from contaminated plastic waste. 

The two-stage process is far leaner than the legacy recycling process, where plastic waste is ground, compounded, filtered and pelletised after sorting and cleaning. Thus far, the plastic has had to be melted twice for reprocessing. Pelletising the recycled material is an energy-intensive process which typically also involves logistics overhead. The need for this step is removed completely in the two-stage process. Based on calculations by ENGEL, the energy required for manufacturing the product is reduced by at least 30 percent.

4. How do you see “Design for Recycling” in injection moulding? And what are the upcoming trends in sustainability for plastics moulding?

Design for Recycling is an absolute must-have, if we are serious about the circular economy. Later recycling needs to be taken into account and planned for as early as in the development of new products. One example is thin-wall packaging produced using in-mould labelling. The trend here is towards monomaterial solutions, which allow the containers to be recycled along with the label. Another field where a great deal is happening in terms of design for recycling is lightweight construction in the mobility sector. At ENGEL, we are focusing on thermoplastic composite solutions. In the ENGEL organomelt process, thermoplastic sheets or UD-tapes are formed and functionalised in an integrated process by moulding the functional elements directly onto the preform. Again, the aim is to use materials belonging to the material group of the fibre composite prepreg matrix material for moulding on. The parts created in this way can then be fed back into the material cycle at the end of their service lives.

When it comes to trends for greater sustainability in injection moulding processing, ENGEL is taking action at various levels. Among other things, this is about innovative technologies for processing recycled materials, about process stability thanks to smart assistance systems, but also about the energy efficiency of the processing machines. 

5. Where can the readers find out more about you and the Circular Economy offers?

Just contact me and my colleagues. We are on site at very many trade fairs worldwide and can be contacted at any time by phone, email or on LinkedIn. Our website also gives people great overview of our commitment to sustainability at ENGEL: ▷ Circular Economy & Plastics Recycling - ENGEL ( We also have our own blog there to keep our readers up to date at all times.

That was the guest interview with Bianca Gubi from ENGEL AUSTRIA GmbH – thank you Bianca and the whole team for sharing such interesting insights of the Circular Economy moulding!

Thanks for reading!

Greetings and #findoutaboutplastics

Herwig Juster

Polyarylamide vs Polyamide (PARA vs PA): What are the Major Differences Between PARA and PA (Polymer Material Selection Tip)?

Hello and welcome to a new post. During material selection you may realize that high strength, stiffness, excellent surface properties, low water uptake and good processing is needed which cannot be fulfilled with the selected aliphatic Polyamide, then Polyarylamide (PARA or MXD6) may be an excellent way forward. 

Differences between PARA and PA

Table 1 compares the properties of PARA, PA 6.6, and PA 6 with a 50 wt% glass fiber loading, together with a PBT having a 30 wt% glass fiber reinforcement. PARA takes up 87% less water compared to PA 6.6 and contains high modulus levels also after moisture pick up. Table 2 shows the dimensional change after moisture absorption of PARA, PPA, and standard PA. It can be shown that 50 wt% glass fiber reinforced PARA changes only 0.32% after 24-hour water immersion (at 23°C), where else other semi-aromatic polyamides changed twice and standard polyamides four times as much compared to the PARA value. Apart from the low water uptake, PARA offers the best surface among all Polyamides due to its fine crystallization in the surface regions. This makes it a good choice for coating or painting applications. The high modulus comes from the fact that PARA is a fairly large molecule with its aromatic ring structures which entangle. Furthermore, this kind of crystallization allows during injection moulding to apply longer effective packing pressure and prevent sink marks. 

Table 1: property comparison of PARA, PA 6, PA 6.6 and PBT.

Table 2: dimensional change after moisture absorption of PARA, PPA, and PA after 24 hours at 23°C, ISO 62 test
Another major difference between PARA and standard Polyamides is the surface finish. Moulded parts in glass-fiber reinforced PARA achieve a low surface roughness value of 0.10 mu Ra  (Figure 1) and standard Polyamides are around 0.25 mu. Mechanically polished steel has the equivalent surface roughness value as PARA. Among the Polyamides (aliphatic and semi-aromatic), PARA has the lowest surface roughness value. Reason is the fine crystallization of PARA in the surface layers of a moulded part. 

Figure 1: surface roughness of glass-fiber re-inforced PARA and standard Polyamides

Differences between PARA and PPA

If we compare PARA to PPA (Polyphthalamide) we see one major difference: the location of the aromatic rest with the double bonds. PARA is build up via polycondensation of an aliphatic dicarboxylic acid (adipic acid) and an aliphatic diamine with aromatic ring (1,3-xylylenediamine; MXD)

-PPA: aromatic rest is coupled to C=O 

-PARA: aliphatic rest is coupled to C=O 

This difference is shown in Figure 2. 

Among the high heat plastics, PPA and also PPS play an important role; PPAs based on 6T/6I/66 have a Tg of 123°C, a 6T/6I has even a Tg of 133°C which makes them useful for high heat applications. 

PARA on the other hand has a Tg of 85°C and although you need for moulding tool temperatures of 120°C (for optimal crystallization), it is not a typical high heat plastic.

However, due to this small difference in the main chain, it has a high Young's modulus and makes it a perfect metal replacement material where optimal surface aspects are needed too. Here an example of a metal replacement for a children buggy where high strength, and stiffness as well as outstanding surface finish is needed. 

Figure 2: differences in chemical structures of PARA and PPA.

Pros of PARA 

-low water uptake (<1,5%)

-high dimensional stability which enables complex parts

-high stiffness and strength (metal replacement)

-very good flow properties (like PPS) and thick parts without sink marks are possible

-PARA has low thermal expansion and it is similar to glass making PARA a good candidate for automotive interior applications. Polymers such PC/ABS and PPS do not have such low thermal expansion. 

-crystallisation in injection mould takes place slowly with a fine crystal structure. This has the advantage of filling the part even in the packing phase and having a part with outstanding surface appearance although it has a high glass fiber loading (up to 60 wt%). 

-thin wall moulding down to 0.5 mm is possible too

Cons of PARA 

-it  is not a typical high temperature polymer such as PPS and PPA, however for many metal replacement and aliphatic Polyamide temperature resistance levels are sufficient. PARA with 60 wt% glass reinforcement can compete with a PPS - 65 wt% glass and mineral filling up to 150°C as shown here

-it has not the best UV resistance capabilities, however with proper additives is possible to fulfil certain Automotive UV standards. 

-price range is between PA 6.6 and PPA. 

Application examples: 

-Metal replacement with PARA for healthcare applications

-Other application fields include air vents in car interior and buggy parts. 

In conclusion, if you need a combination of low moisture uptake, high dimensional stability (complex parts), excellent surface, together with outstanding stiffness & strength, and very good flowability than PARA is the material of choice. 

Thank you for reading and #findoutaboutplastics


Herwig Juster

Interested to talk with me about your polymer material selection, sustainability, and part design needs - here you can contact me 

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.





Tuesday 4 April 2023

Thin Wall Moulding of Engineering Polymers (Rule of Thumb)

 Hello and welcome to this new Rule of Thumb post. Today we discuss the thin wall injection moulding of engineering polymers. 

High performance polymers such as PPS and LCP reach low viscosity levels at high injection moulding shear rates and temperatures. Other polymers such as Polycarbonate and Polymethyl methacrylate have a high melt viscosity, however flow properties can be improved by adding additives

Thin wall injection moulding with engineering polymers

The common wall thickness of engineering plastics ranges between 2 to 4 mm. Thin wall moulding focuses more on wall thickness below 2 mm. In general, the wall thickness influences the stiffness of the part, achievable flow lengths in the mould, cycle times, shrinkage, and weight of the part. Thin wall injection moulding results in high shear rates and injection pressures too. Drivers for thin wall parts are the Electric & Electronics, Automotive, and Telecommunication industries. 

How can we classify thin wall moulding in a quantitative way?

Spiral flow data is one way and is a good alternative to melt flow index (MFI) measurements. Another way of classification is over the flow length to wall thickness ratio (L/t). Since each polymer has different flow properties, the maximum achievable L/t ratios vary. Figure 1 shows the L/t ratio of commodity and engineering polymers based on a 2 mm wall section. Polyolefins, Polystyrenes, and ABS are good candidates for parts with 2 mm wall thickness and below. 

Figure 1: Maximum L/t of commodity and engineering polymers based on a 2 mm wall section.

More Rule of Thumb posts can be found here

Thanks for reading and #findoutaboutplastics


Herwig Juster

Interested to talk with me about your polymer material selection, sustainability, and part design needs - here you can contact me 

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.



[2] DuPont Design Guide