Wednesday, 24 May 2023

Guest Interview: Alexander Lehner-Jettmar – Technical Sales Engineer at Biesterfeld Interowa GmbH & Co KG

Hello and welcome to this guest interview. Today I present to you Mr. Alexander Lehner-Jettmar from the international plastics trading and distribution company Biesterfeld Interowa GmbH & Co KG. We have the chance to learn about the most common injection moulding defects and how one can avoid them.

Enjoy the interview!


1. Tell us about yourself, your current role, and your way into the polymer industry
 
Hello Herwig, thank you for interviewing me and having me on your blog! I am Alexander Lehner-Jettmar and work as a technical sales engineer at Biesterfeld in Austria. I have been working in the plastic industry for 8 years and before that I completed the study of plastics and environmental technology at the TGM in Vienna.
Biesterfeld is one of the leading international distributors in the plastics industry and a partner for innovative solutions in the field of high-performance plastics, engineering thermoplastics, thermoplastic elastomers, styrene copolymers as well as standard polymers and additives. In my role as technical sales engineer, I support customers from the very first idea to the finished application and provide technical advice in the areas of material selection, tool and component design, processing and failure analysis.

2. Based on your experience, what are the most common injection moulding defects and how can one avoid them?

There are different types of injection moulding defects which I help to resolve at my customers. Among the defects I am confronted with are: too small gate designs, holding time too short, bad venting, wrong melt temperature, wrong tool temperature, and moisture in the granules.
Let me discuss a few of these issues.

Small gate design
Polymer parts are designed by using complex methods such as computer-aided design, finite element analysis and mould flow calculations. While these methods are very useful, I often see that there is less focus on the importance of the correct design of the feed system. Semi-crystalline thermoplastics undergo a volume shrinkage during the transition from the molten state to the solid state. This shrinkage, which may be as much as 14 %, depending on the type of resin, has to be compensated during hold time by the supply of additional melt into the mould cavity. That can only be done if the gate cross-section is adequate to ensure the presence of a fluid centre during the holding phase. If the gating system is too narrow, the holding pressure cannot remain effective beyond the desired holding pressure time. In that case, volume shrinkage cannot be adequately compensated, resulting in the formation of voids and sink marks.
In designing the feed system, the first point to be considered is the wall thickness of the moulded part. The diameter of the runner should never be less than the wall thickness of the moulded part.
When moulding partially crystalline, unreinforced polymers, the minimum gate thickness should be 50 % of the wall thickness of the moulded part. This would also be adequate for reinforced compounds. To minimise the risk of damage to the fibres and also bearing in mind the higher viscosity of these compounds, the gate thickness should be up to 75 % of the wall thickness of the moulded part. How a self-separating sprue system is optimally designed can be seen in Figure 1.

Figure 1:  Optimally design of a self-separating sprue system [Biesterfeld/DuPont].

If the sprue cannot go direct into the cavity, the gate length is especially crucial. The gate length should be ≤1 mm to prevent premature solidification of the sprue, so that the mould will heat up near the gate, and the holding pressure is working most effective (Figure 2).

Figure 2: Optimal design of gate if the sprue cannot be placed directly into the cavity [Biesterfeld/DuPont].


Also the gate position should be in the region of the maximum wall thickness of the moulded part to avoid voids and sink marks. This is especially essential for semi-crystalline plastics.

Bad venting
A well designed venting system is crucial for the durability and maintenance intervals of an injection mould.  Especially when processing flame-retardant materials, the durability of a tool can be significantly extended by implementing a good ventilation.

Since flame-retardant modified compounds are demanded more and more often, the subject of proper ventilation is also becoming more and more important.

Nearly always, I see insufficient venting when I look more closely at tools in the field. In most cases, the vent is not placed close enough to the cavity which prevents it from working efficiently. Also, the width of the ventilation gap, the so called "vent land" is often not adequately designed. The recommendation is that the vent land is max 0,8 mm long before the vent channel gets bigger and leads the air outside. In most cases, the vent channel is more than 3 mm away from the cavity. This leads to defects such as burn marks, mould deposits, poor part surfaces and an increased mould tool abrasion. If the venting is insufficient, component quality also suffers. Besides fire marks at the end of the flow path, also the weld line strength is affected. A well placed vent near the weld lines can double the weld line strength by allowing air to escape more easily in this section.

In essence, the following rules are applicable when designing a venting system.
  • Vent land must be as short as possible (max 0,8 mm)
  • Vent land must be as wide as possible
  • Moving cores/inserts should also be vented (parting line or add ejector)
  • Relief channels must exit to atmosphere without restriction

The following Figure 3 illustrates the recommendations.

Figure 3: Design of proper venting around injection moulding tool cavity [Biesterfeld/DuPont].

It should not only be vented at the end of the flow path. The earlier the ventilation is intended, the more air can be pressed out of the cavity prematurely to avoid higher pressure at the end of the flow path.

In many cases the injection pressure can reduce by a good venting and energy costs can be saved, which is also a nice side effect.

Holding time too short
In practice many injection moulders, working from their experience of amorphous polymers, tend to use shorter hold pressure times and longer cooling times. Unfortunately, this approach also tends to be used for semi-crystalline polymers.

Once the mould cavity has been filled, the polymer molecules start to crystallise, i.e. the molecule chains become aligned with respect to each other, resulting in higher packing density. This process starts in the outer zone and ends in the centre of the part. As mentioned the shrinkage can be up to 14% of the volume and has to be compensated during holding time. I often see that the holding pressure time is too short to compensate for this shrinkage. Parts made in this way often show excessive shrinkage, warpage, sink marks, voids and, in some cases, enormous loss of mechanical properties. In addition, there may be considerable dimensional variations too.

The required holding pressure time depends on the polymer and the additives used. The following Table 1 shows the typical required holding pressure time per mm wall thickness for different materials.

Table 1: Crystallisation time in seconds per mm wall thickness.

Wrong melt temperature
Choosing the optimal melt temperature is vital for part quality when moulding semi-crystalline engineering polymers. As a rule of thumb we can state that the margin of tolerance for semi-crystalline polymers is less than when processing amorphous resins. The moulder at his machine directly influences the properties of the end-product.

Melt temperature can be too high or too low and both are wrong. In addition, even distribution of temperature in the melt is also a factor to be kept in mind.

Temperatures that are too high degrade the polymer, that is, destroying the molecular chains. Another consequence may be that additives in the melt, such as pigments, impact modifiers, flame retardants etc., also decompose or start reacting too early. The results are poorer mechanical properties as a result of the shorter molecular chains, surface defects and a bad odour in the production.
When the temperature is too low, the polymer melt fails to achieve the required homogeneity. This drastically reduces impact resistance and leads in most cases to considerable variations in physical properties.

The data sheets for engineering polymers indicate the optimum melt temperature range for each polymer. In general, the temperature setting of the barrel heating zones alone is not reliable because, apart from the temperature rise due to the heater bands, friction from the screw rotation also generates heat. How much heat is generated this way depends on screw geometry and rpm as well as on back pressure. For the correct melt temperature, you should therefore not only rely on the machine parameters, but also measure the actual temperature of the melt.

What I also often see is that the hot runner is set hotter than the plasticising unit. Since the granulate should already be completely melted before it reaches the machine nozzle, a higher temperature in the hot runner makes no sense. The material is only thermally damaged and the risk of black specs is increased if there are dead spots in the hot runner system, which leads to quality issues.
For semi-crystalline materials the nozzle and the hot runner system should run 5-10°C lower than the last zone of the cylinder, as long as the hot runner nozzles do not freeze. If the hot runner nozzles freeze, you should have a look at the thermal decoupling of them. 

3. Let us deepen the impact of residual moisture in various polymers such as Polyamides, Polyesters (PET, PBT), Polycarbonate and others. 

Many plastics absorb moisture from the atmosphere. How much they absorb depends on the type of resin. Moisture in the granules, even if it is only surface condensation, can cause problems in parts moulded with engineering polymers. Many types of undesired effects can occur, including processing problems, poor surface on moulded parts or loss of mechanical properties. It is seldom possible to tell if moisture is present by visual inspection alone.

The following Figure 4 shows the maximum moisture absorption of various plastics at room temperature and 50% humidity.

Figure 4: Maximum moisture absorption of various plastics at room temperature and 50% humidity [Biesterfeld/DuPont].

Most engineering polymers require the moisture content of the granules to be below a certain maximum level for a proper processing.

During the injection process, moisture in the granulate can act as a processing aid, which increases the flowability. A certain amount of moisture is therefore useful. However, if the moisture content is too high, surface defects on the part and hydrolytic degradation of the polymer chains can occur, which reduces the mechanical properties and is not reversible.

The need for drying depends mainly on how sensitive the raw material is to water. Naturally, the moisture content of the material as it is delivered, the type of packaging and the period of storage are also important criteria. For example, polyamide is generally packed in bags with a barrier layer of aluminium, so that it can be used straight out of the bag. However, most processors of PA prefer to dry the resin in any case, even though drying is not necessary if the material is used within one hour. PET and PBT, on the other hand, are far more critical regarding moisture uptake and must always be dried to ensure that impact strength of the moulded parts is not affected. Another factor is that these resins pick up moisture very rapidly after drying, so that moulders should exercise special care when handling open containers of PET and PBT, when they are in transport or conveyor systems, as well as regarding their dwell time in the hopper. Thus, in unfavourable climatic circumstances PET can absorb enough moisture in 10 minutes to exceed the maximum permitted moisture content for moulding of 0,02%.
Additionally. 

Table 2 shows the typical effects of high moisture uptake in engineering polymers.

Table 2: Typical injection moulding effects of high moisture uptake in engineering polymers.

It is important to follow correct drying procedures if you want good quality mouldings. Simple hot air dryers of various types are not suitable for drying polyesters, for example, however dehumidified air dryers are acceptable. Only these can provide the required constant and adequate drying, whatever the ambient climatic conditions. In addition to maintaining the correct drying temperature, it is important to ensure that the dew point of the drying air remains lower than ≤20° C. When operating multi-container systems with different fill heights and bulk densities, it is also important to ensure that the air throughput in each container is sufficient.

4. In recent years more and more Pre- and Post Consumer Recyclates are moulded - what do we have to consider with such materials in injection moulding?

Drying regrind e.g. in the case of containers which were left standing around open requires special care. In these cases the recommended drying times are usually not enough. Fully saturated polyamide may need more than 12 hours to dry. The yellowing associated with such treatment is practically unavoidable.

To minimize the moisture pickup when using regrind, the following points should be considered.
- Always store sprues and regrind in closed containers.
- Seal containers or bags that have been partially used.
- Leave a lid on the hopper.

5. Where can the readers find out more about you (LinkedIn, etc)?
If there are any questions or if anyone would like to dig deeper into these topics, I can be reached via my email address a.lehner-jettmar@biesterfeld.com, or via my LinkedIn profile.

That was the guest interview with Alexander Lehner-Jettmar from Biesterfeld Interowa – thank you Alexander for sharing your experiences and optimization tips in polymer injection moulding!

Thanks for reading!

Greetings 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.

Literature: 

[1] Biesterfeld/DuPont - Konstruktion und Verarbeitung von Kunststoffen: https://www.interowa.at/website/file/konstruktion_verarbeitung_broschuere_a5-richtig_print.pdf

Monday, 22 May 2023

Injection Moulding of POM - Checking Thermal Degradation (Rule of Thumb)

 

Injection Moulding of POM - Checking Thermal Degradation

Hello and welcome to this new Rule of Thumb post, discussing how to check the thermal degradation of Polyoxymethylene (POM) during injection moulding.

Setting the optimal melt temperature during processing is important for POM since it cannot be thermally stretched too much. Polymers such as Polyamide and Polyesters can handle higher set temperatures better during processing compared to POM which develops gases as result of degradation.

What are signs for thermal degradation? 
Typical signs of POM degradation are: 
-melt shows a foamy structure when leaving the injection nozzle
-it has a strong odor
-the nozzle tends to spill material out
-black and brown specks
-black flow lines on moulded part

How to test for thermal degradation?
Once moulding with POM has started and has run a couple of cycles, the machine will be stopped at the end of the dosing time. Now the machine stands still for 10 minutes (natural POM) or 2 minutes (coloured POM). After the waiting time is over, injection of the melt into the open is done. During ejection, check if there is formation of foam. After cooling down the melt cake, the swimming test is done. If the melt cake swims, then there is too much formation of foam and the material is thermally damaged. 

For POM, the recommended melt temperature is 215 +/-5ºC at which the melt for standard grades will remain stable without degradation (residence time is around 30 minutes).

More Rule of Thumb posts can be found here

Thank you for reading and #findoutaboutplastics
Greetings, 

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.

Literature: 

[1] DuPont - Serie Teil 3: Spritzgießen von Polyoxymethylen (POM)

Sunday, 14 May 2023

Pumping Plastics 2022 - My New Book "Pumping Plastics" is Now Available as Paperback Worldwide on Amazon!

 

Pumping Plastics 2022 by Herwig Juster


Dear community, 

welcome to this special book update! 

Pumping Plastics is the name of my new book and it contains all the blog posts of 2022.

For instances, this include topics such as :

-Sustainability in the plastics industry

-Guest interviews with innovative material start-ups

-Polymer design properties and multi-point design data

-Plastics additives (three part series)

The book can be read chronologically from month to month, but not necessarily.You can also directly jump to the post(s) of your interest.

As a bonus, the first chapter of my first book "Polymer Material Selection" is included.

I invite you all to have a look and grab a copy.

Enjoy the read! 

Greetings

Herwig

Wednesday, 10 May 2023

ISO 1043 - Examples of Often Found Plastic Part Marking Codes and Their Meaning (incl. Miniguide for Downloading)

Hello and welcome to a new post. Today’s post will highlight examples of often found part marking codes on plastic parts and their meaning using the standard ISO 1043.

Supporting this topic, I  made a miniguide (download here), and detailed blog post (here) allowing to deep-dive into the basics. 

Figure 1 shows an example of a glass fiber reinforced PA 6 with a flame retardant package consisting of three different types of additives. 

Figure 1: Part marking example of a glass fiber reinforced PA 6 with a flame retardant package

Table 1 presents often used examples of engineering and high performance polymers which can be used as a guidance for your next polymer material selection and plastic product development project. 

Table 1: Examples of engineering and high performance polymers for plastic part marking

Thanks for reading and #findoutaboutplastics

Greetings, 

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.

Literature:

[1] ISO 1043 



Friday, 5 May 2023

Plastic Multipoint Design Data: Shrinkage of Amorphous (ABS, PC) and Semi-Crystalline (PA 6) Polymers as a Function of Wall Thickness and Fillers

Hello and welcome to this plastics multipoint design data post in which we discuss the shrinkage of amorphous (ABS, PC) and semi-crystalline (PA 6) polymers as a function of wall thickness and fillers.

Impact of filler and reinforcing materials on shrinkage

Table 1 compares the shrinkage in longitudinal and transverse direction of a non-reinforced Polyamide 6 with filled and reinforced Polyamide 6. It is possible to influence the shrinkage values by using certain filler content and filler type. Using spherically-shaped fillers reduces the shrinkage in longitudinal and transverse directions. However, using glass fibers helps even more in the longitudinal direction since they impede thermal contraction in the glass fiber direction. In the transverse direction it is almost the same range as the spherically shaped fillers. Adding glass fibers is an effective way to influence shrinkage values of PA 6 (decrease between 50-80%) and the optimum level of glass fibers is at 30 wt%. From there on it levels off and adding more glass fibers will not result in lower shrinkage values. This is illustrated in Figure 1 where a PA 6.6 is loaded with different amounts of glass fibers, reaching a maximum load at 35 wt%. 

Table 1: Comparison shrinkage in longitudinal and transverse direction of a non-reinforced Polyamide 6 with filled and reinforced Polyamide 6.

Figure 1: Estimation of moulding shrinkage of a PA 6.6 loaded with different amounts of glass fibers, reaching a maximum load at 35 wt%.

Shrinkage of semi-crystalline (PA 6) polymer as a function of wall thickness and fillers

Figure 2 shows the correlation between shrinkage and wall thickness of an unreinforced PA 6 and a 30 wt% glass fiber PA 6 (both dry as moulded - DAM). Influence of the wall thickness on the shrinkage can be in particular seen with unreinforced PA 6. Explanation for this is that an increased wall thickness leads to slower cooling and allows the crystalline regions to fully grow. As a consequence, higher crystallisation results in higher shrinkage values. If the shrinkage becomes too much, warpage will most likely be the consequence in your final part, especially when it is a flat shaped part. 

Figure 2: Correlation between shrinkage and wall thickness of an unreinforced PA 6 and a 30 wt% glass fiber PA 6 (both dry as moulded - DAM).

Shrinkage of amorphous (PC, ABS) polymer as a function of wall thickness and fillers

Figure 3 shows the correlation between shrinkage and wall thickness of an unreinforced Polycarbonate (PC) and glass fiber reinforced PC. Figure 4 shows it for Acrylonitrile Butadiene Styrene (ABS). Amorphous polymers have a lower shrinkage level due to its missing crystalline sections. 

Figure 3: Correlation between shrinkage and wall thickness of an unreinforced Polycarbonate (PC) and glass fiber reinforced PC.

Figure 4: Correlation between shrinkage and wall thickness of an unreinforced ABS.

More multipoint data post can be found here: 

Thanks for reading and #findoutaboutplastics

Greetings, 

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.

Literature:

[1]  Zöllner, O.: “Prozessgrößen beim Spritzgießen von Thermoplasten als Produktionskostenfaktor” paper presented at the SKZ Würzburg, Bayer AG, 1993

[2] Covestro: The fundamentals of shrinkage in thermoplastics, 2016: https://solutions.covestro.com/-/media/covestro/solution-center/whitepapers/the-fundamentals-of-shrinkage-in-thermoplastics.pdf

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 Maracanã 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

Greetings 

Herwig 

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.

Literature: 

[1] https://branded.disruptsports.com/blogs/blog/tpe-vs-pvc-vs-rubber

[2] https://www.statista.com/topics/961/sporting-goods/

[3] https://www.plasticsmakeitpossible.com/about-plastics/wait-thats-plastic-sports-edition/#:~:text=Nylon%2C%20polyester%2C%20acrylic%2C%20lycra,%2C%20comfy%2C%20sweat%20wicking%20fabrics.

[4] https://plasticseurope.org/plastics-explained/plastics-in-use/sport-leisure/#:~:text=Plastics%20in%20sports%20footwear&text=For%20comfort%20and%20support%2C%20the,extra%20comfort%20on%20the%20insoles.

[5] https://branded.disruptsports.com/blogs/blog/tpe-vs-pvc-vs-rubber

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

Greetings

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.

Literature: 

[1] https://www.sabic.com/en/products/documents/material-technologies-to-support-drug-delivery-devices/en

[2] https://www.solvay.com/en/news/solvay-launches-iscc-plus-certified-mass-balance-hydroquinone-and-hydroquinone-monomethylether

[3] https://www.iscc-system.org/about/circular-economy/mass-balance-approach/

[4] https://www.omv.com/en/blog/plastic2plastic-reoil-completes-the-circle-in-plastics-recycling

[5] https://www.iscc-system.org/process/overview/

[6] https://plasticseurope.org/case-studies/how-borealis-bornewables-portfolio-of-iscc-plus-certified-polyolefins-are-helping-reduce-carbon-footprints-for-customers-while-contributing-to-the-circular-economy/


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 (engelglobal.com). 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) - 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) 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. Apart from the low water uptake, PARA offers the best surface among all Polyamides due to its fine crystallisation 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 crystallisation allows during injection moulding to apply longer effective packing pressure and prevent sink marks. 

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

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 1. 

Figure 1: 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 fullfil 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. 

Thank you for reading and #findoutaboutplastics

Greetings, 

Herwig Juster


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

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Literature:

[1] https://www.solvay.com/en/brands/ixef-para/properties

[2] https://www.findoutaboutplastics.com/2020/02/metal-replacement-with-polyarylamide.html