Wednesday, 5 March 2025

Polyarylamide (PARA; MXD-6) and Recycling: How much regrind is possible?

Hello and welcome to a new post in which we discuss the usage of regrind when processing the high-performance Polyarylamide (PARA; MXD-6).


Recycling Process:

Polyarylamide regrind (sprues, runners, etc.), containing reinforcements such as glass fibers, can be recycled with virgin PARA compound. Important is to exclude any contamination such as oil, release agents, and other additives.

Impact on Mechanical Properties and Color Variation:

Several studies and experiments have shown [1] that a split of 70/30 (70 wt% virgin PARA / 30 wt% regrind) is preferred. The compound used in each cycle is 70% virgin compound (containing 50 wt% glass fibers) mixed with 30% regrind from the preceding cycle. Very little change is observed in these mechanical properties (tensile strength, elongation at break) after recycling. Successive recyclings may cause a slight change in color. 

Recommendations:

Important is to confirm the recycling rate experimentally to ensure the finished part meets specifications. Also, drying the regrind prior to injection unless ground and reinjected at the press. Mark parts to facilitate after-use recycling (check out the part marking codes here).

Thanks for reading and #findoutaboutplastics

Greetings

Literature: 
[1] https://content.solvay.com/ixef-para-processing-guide



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Tuesday, 4 March 2025

Become a Master in Polymer Material Selection - Learn & Apply the “6 POMS” Skills

Hello and welcome to a new blog post. Over the course of my career as a polymer engineer, I have sought to delineate the requisite skills for effective polymer material selection. Through discussions with polymer engineers responsible for successful plastic product development over the past decade, it has become evident that proficiency in six distinct areas is consistently demonstrated. These individuals not only possess comprehensive knowledge but also apply it rigorously across multiple product development cycles. Through iterative refinement and detailed analysis, these six areas have been systematically mapped. Consequently, I have formalized these competencies into what I now refer to as the "6 POMS" skills (Figure 1).

The 6 Polymer Material Selection Skills

Figure 1: Overview of the 6 POMS skills helping to become a Master in polymer material selection [1].

Let us discuss each of the 6 P's:

P- Properties: Understanding key polymer properties 

To effectively select polymers for specific applications, a thorough understanding of their key properties is essential. This includes familiarity with polymer structure properties like morphology, molecular weight, and thermal transitions. Knowledge of mechanical properties such as tensile, flexural, and impact strength, stiffness, and elongation is crucial. Additionally, a grasp of thermal properties, including glass transition temperature (Tg), melting temperature (Tm), and heat resistance, is necessary. The ability to assess chemical resistance to acids, bases, solvents, and oxidation is also vital. Furthermore, awareness of both long-term and short-term properties and their relationship to application requirements is paramount. Finally, understanding multi-point property data and its relevance to application needs ensures optimal material selection.

P - Part Design: Defining Application Requirements for Plastic Part Design 

The success of a plastic part depends heavily on its ability to meet the specific demands of its intended application. To ensure this, a structured approach to defining requirements is essential. This involves using tools like requirement checklists and methodologies such as the FLERP approach (Function, Loading conditions, Environmental Factors, Regulatory requirements, and Processing requirements).

A crucial aspect of this process is the ability to write clear and concise product specifications. This requires a deep understanding of the part's true functions, load cases, and material requirements. Additionally, it is important to consider the data needed for plastic part design, including material properties, processing parameters, and environmental factors.

Finally, cost considerations should be integrated throughout the design process. This involves evaluating material and manufacturing costs to optimize the overall design and ensure economic viability. By following these steps, engineers can effectively define application requirements and design plastic parts that meet the needs of their intended use.

P - Polymer material values: Translating application requirements to qualitative and quantitative material values

Translating plastic application requirements into actionable material values is a critical step in the selection process. This involves understanding how qualitative and quantitative application needs correspond to specific material properties. A systematic approach, such as listing all application requirements and their translated material values in a dedicated system or sheet, significantly enhances the selection process by providing a clear and organized framework for evaluation.

P - Process: Polymer material selection process

The process of selecting polymer materials involves several key considerations. It's important to determine if a structured, step-by-step approach is currently in place. Utilizing online databases like CAMPUS or Omnexus for material identification is common practice. A fundamental understanding of how to interpret technical datasheets for plastics is also crucial. Furthermore, the selection process should involve a degree of critical thinking, including challenging the use of established materials and exploring alternative options. Questioning the rationale behind choosing specific resins and ensuring they align with actual requirements is vital. Finally, the use of decision-making tools can significantly facilitate the selection of appropriate plastics.

P - Performance: Evaluation of material and part performance

Evaluating plastic material and part performance requires a comprehensive approach. Utilizing CAE tools, like injection mould filling simulation and FEA, enables virtual testing and optimization of plastic parts. Familiarity with standard ISO tests, such as tensile tests, is essential for quantifying material properties. Physical prototyping plays a critical role in verifying material and part functionality. Ultimately, experience in testing both material and part performance is crucial to confirm the suitability of the chosen plastic for its intended application.

P - Plastic supplier: Selection of material and supplier

The selection of plastic materials and suppliers involves active engagement and collaboration. Regularly discussing application requirements with polymer application engineers is crucial for ensuring material suitability. Direct contact with material suppliers to obtain samples supports the selection process by allowing for physical testing and evaluation. Seeking recommendations from plastics experts and material suppliers on new material developments ensures access to the latest advancements and potential solutions.

How to train the 6 POMS skills and become a master in polymer material selection? 

Start by taking my new developed Polymer Material Selection test and discover your polymer material selection score. Assess where you are currently ranking at the different POMS skills and increase your ability to select plastics better. It is a simple test which consists of 26 Yes/No questions. After submitting, you will receive a report containing your overall POMS score, the detailed score and recommendations for improvements.

I invite you to take the test, get your POMS-score and review the suggested improvements.

Thanks for reading & #findoutaboutplastics!

Greetings, 

Herwig 

New to my Find Out About Plastics Blog - check out the start here section


Literature: 

[1] https://www.polymermaterialselection.com/poms-score

[2] https://www.amazon.de/-/en/Polymer-Material-Selection-practical-systematic/dp/B0BSWM6BPD


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Thursday, 20 February 2025

📚 My new book, "Pumping Plastics 2024," is out now! Available as Paperback Worldwide on Amazon!

Dear community, I'm thrilled to announce the release of "Pumping Plastics 2024," featuring guest interviews with leading material manufacturers and medical-grade plastics consultants. Explore the latest advancements in high-performance polyamides (PARA), material selection, polymer design properties, and more. 

My new book, "Pumping Plastics 2024," is out now!

This book, weighting 135 pages, contains all the posts published on my FindOutAboutPlastics.com blog in 2024. It is part of my "Pumping Plastics" book series. 

For instances, this include topics such as:

  • Guest interviews with innovative material manufacturers and medical grade
  • plastics consulting
  • High performance polyamides such as Polyarylamides (PARA)
  • Polymer design properties and multi-point design data
  • Polymer material selection examples
As a bonus, the first chapter of my first book "Polymer Material Selection" is included.

Pumping Plastics 2024 by Herwig Juster is part of the "Pumping Plastics" book series. 

Level up your materials knowledge – grab your copy here and stay ahead of the curve!

Thanks & #findoutaboutplastics

Greetings,

Herwig Juster

#PumpingPlastics2024


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Monday, 17 February 2025

Injection Moulding of Polyphenylene sulfide (PPS) - The Key to High Crystallinity and Performance

Hello and welcome to a new post in which we discuss the importance of mould temperature for achieving optimal crystallinity and performance in polyphenylene sulfide (PPS) moulded parts.  

Why is mould surface temperature critical with PPS?

The high-performance polymer PPS is a semi-crystalline polymer and its backbone consists of aromatic rings (phenylene groups) linked by sulfide bridges. It has a glass transition temperature of 88°C, melting temperature of 282°C and a processing temperature of 320°C. It combines high heat resistance (UL 746B exceeding 200°C), with high chemical resistance and mechanical strength at an economical price range.  As a high temperature plastics, also attention to proper processing, especially injection moulding needs to be given. Achieving the optimal level of crystallinity of PPS parts is important. 

Crystallinity significantly impacts the part's performance and stability, and even cooling is essential for high-quality mouldings. Mould surface temperature for PPS should be between 135° and 150°C in order to obtain high levels of crystallinity (maximum crystallinity levels of PPS: 55%).

Injection mould temperature settings for PPS

There is the "hot mould" and "cold mould" approach.  "Hot mould" temperatures (above 135°C) are preferred for precision parts as they promote crystallization, resulting in the best overall appearance, thermal stability, and dimensional stability.  "Cold mould" temperatures (below 88°C), on the other hand, produce amorphous parts with a mottled/grainy surface appearance. While cold moulds offer some advantages in physical properties and less shrinkage directly out of the mould, hot moulds are generally favored for achieving the best balance of properties, especially in precision applications.

Important are suitable cooling methods, and it is recommended to use circulation-type systems using hot oil or pressurized water.  If heater cartridges are used, they should have a minimum capacity of 1 kW per cartridge. 

Differential Scanning Calorimetry (DSC) can assess crystallinity in an effective way.

After moulding the PPS part, we can use the DSC to check if the part was fully crystallized and as a consequence, all important properties such as thermal and chemical stability, as well as dimension stability are fully developed. Figure 1 shows the results of two DSC curves. The upper curve shows a not fully crystallized PPS, having a so-called cold crystallisation peak at 114°C (exothermal) and a melting peak at 282°C. The lower curve shows a fully crystallised PPS part having only a melting peak at 282°C. 

Figure 1: Example comparison DSC curve of a not fully and fully crystallized Polyphenylene sulfide (PPS) moulded part. 

Conclusion

In essence, the careful control and selection of mould temperature (135-150°C), along with appropriate cooling methods, are crucial for optimizing the crystallinity and ultimately the performance of PPS moulded parts.

If you need support in moulding high-performance polymers such as PPS and PEEK, you can reach out to me here .

Learn more about high performance polymers such as PPS in my series “High Performance Thermoplastics Selection” .

Thanks for reading and #findoutaboutplastics

Greetings

Literature: 
[1] https://www.syensqo.com/en/brands/ryton-pps
[2] https://analyzing-testing.netzsch.com/de/produkte/dynamische-differenzkalorimetrie-dsc-differenz-thermoanalyse-dta
[3] https://www.solvay.com/sites/g/files/srpend221/files/2018-08/Ryton-PPS-Mold-Temperature_EN-v1.0_0.pdf

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Friday, 7 February 2025

Polymer Selection Funnel Example - Base plate of a filter coffee machine (POMS-Funnel Method)

Hello and welcome to another polymer material selection example for which we use the POMS-Funnel Method (in detail explained here and in this video). Today’s mission is to select the optimal polymer for a base plate used in traditional filter coffee machines (Figure 1). 

Figure 1: Polymer Selection Funnel Example - Base plate of a filter coffee machine using the POMS-Funnel Method.

You want to get quickly started with plastics selection -  I created a practical guide which leads you fast in 5 steps through a selection journey (check it out here). 

Also, my post on 10+ key considerations for selecting the optimal polymer material can help to kickstart your material selection journey. 



Now, back to the selection example. 

For a more detailed selection approach, as mentioned before,  I created the Polymer Selection Funnel methodology (POMS-Funnel) which you can check out here and practical examples in the start here section.

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: Polymer Selection Funnel - overview of the four different funnel stages and tools.

Funnel stage 1: Material selection factors

In the first Funnel stage we focus on gathering and understanding all the requirements of the base plate for the  filter coffee machine. 

Following questions can help us with this assessment:
-What are the performance requirements (structural, etc.)?
-Do you want to combine multiple parts or functions?
-What will be the structural load of the part (static, dynamic, cycling, impact, etc.)?
-What will be the environmental impact on the part (chemical, temperature, time)?
-What is the expected lifetime of the product?

After answering the functionality questions, we continue with the, in my point of view,  six essential questions on material selection factors (6 What's):
1. What is the service environment of your part?
2. What are the regulatory requirements?
3. What types of load at which service temperature and time need to be fulfilled?
4. What other things such as wear and friction, electrical properties such as CTI, electrical breakdown strength, aesthetics and colour (relevant for application with food contact, and toys), and more, need to be considered?
5. What is the processing and fabrication method?
6. What are the economic and commercial considerations?

A more detailed list can be found here (incl. download): Material Selection Requirements Checklist

I split the requirements in three different sections: 
  1. Functional requirements related to the part: the base plate serves as a housing for electrical components and needs to protect the electrical equipment against external mechanical impacts according to the IEC 62262 (needs to pass the “spring hammer test”). Therefore, design weaknesses need to be avoided and materials with high impact resistance are needed. To stand properly on the floor, good mechanical stability needs to be ensured. Achieving this stiffness can be done over ribs, however ribs may increase surface defects and increase tooling costs. Therefore, a polymer with high stiffness  is preferred  (high elastic modulus; engineering polymers). Keeping the coffee warm for a longer time, temperatures up to 110°C can be reached. Polymers with high continuous use temperatures, as well as long heat aging durability  are preferred. Being used in a kitchen, the coffee machine is exposed to all kinds of fats, oils, soaps, cleaning agents, alcohols, fruit and vegetable acids. Additionally, water vapor and hot coffee will touch the base plate too and therefore hydrolytic resistance is needed. Surface finish and optical quality are a key requirement too. High gloss and scratch resistance surface are required, together with customer specific coloring of the parts. 
  2. Production/processing-related requirements: Since long screw bosses need to be used, polymers with good flow properties need to be used (including good ejection). In addition, there should be no shrinkage and warpage problems after the part was moulded. 
  3. Assembly-related requirement: In order to save costs in the assembling, snap fits should be used to easily connect parts with each other. Therefore a material is needed with high elongation at break and flexural strength. Additionally, some self-tapping screws need to be used and therefore more viscoelastic material is needed. 
After we collected all requirements, we turned them into quantifiable data and added them to our requirement worksheet.  The main criteria will be continuous use temperature (CUT), heat resistance and ageing stability, and optical surface quality. Heat ageing stability can be achieved by additives and therefore, CUT and optical properties are the main driver for the selection. High filled polymers achieve not the desired outcome (with expectation such as PARA) and only neat polymers will be considered. 

Table 1: Overview of requirements for the coffee machine base plate using the requirement worksheet.


Funnel stage 2: Decision on thermoplastic or thermoset

Funnel step 2 leads us through a decision tree, starting with the first branch of taking the thermoplastic route or thermoset route. Reviewing the application requirements (impact, optical, processing), thermoplastics can fulfil the requirements in a better way. Next decision branch in the thermoplastic route is to select whether amorphous or semi-crystalline polymers are feasible. Both amorphous and semi-crystalline materials are feasible to fulfil the coffee base plate requirements. 

Now we can screen the databases and material suppliers for suitable material candidates.  There are reliable database such as Campus and Omnexus and I created dashboards to support this step too: 
  • Dynamic Mechanical Analysis (DMA) Data of Engineering and High Performance Polymers
  • Plastics Pricing Dashboard 
  • Chemical Resistance of Polymers 
  • Plastics Environmental Sustainability Dashboard
All dashboards can be found here.

Among the amorphous polymers, unfilled Polycarbonate (PC) can match the requirements. However, due to long flow length combined with thin ribs and high viscosity, filling of the part is harder. Styrene acrylonitrile resin (SAN) can be considered too, however will not fulfil the high continuous use temperature of 110°C (SAN: 85°C). Polyamide 6.6 will fulfil the 110°C continuous use temperature requirement (PA 6.6: 120°C), however there are limitations of use due to easy coloring when in contact with food. For example, parts moulded in PA 6.6 easily take up the red spots when touched by red beet. 

For our detailed discussion in Funnel step 3, Polybutylene terephthalate (PBT), Polypropylene (PP), and Polyketone (POK) are considered (Table 2):
Table 2: Pre-selected materials for Funnel step 3. 

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

Now we reached the core element in the whole material selection funnel: the  qualitative matrix analysis. It is a detailed selection discussion with a worksheet. It ranks all of the pre-selected polymers on how good each fulfills the requirements. Additionally, the requirements are ranked according to their importance too. The decision matrix analysis consists of five steps (explained in detail here) and the calculation principle is a scoring of each of the pre-selected materials for each of the material selection factors. As a result, we obtain scores for each material. The materials with the highest score are most suitable for selection and will be further investigated in the fourth stage.

How to start the qualitative matrix analysis?

We can use my online tool in order to facilitate this step (Polymer Material Selector V1.1). As an alternative, you can reach out to me and I will provide you with an excel version of it. I only considered the must-have requirements and ISO test standards; Long-term and multi-point test data needs to be checked in Funnel step 4 too. 

In Table 3 the outcome of the qualitative matrix analysis is presented. PBT scored the highest number of points (score: 182 points), followed by PP (score:180 points) and POK (score: 180 points). All three materials should be validated in the Funnel stage 4 since there are important tests. Also, assessing the commercial and processing situation of the materials is important. 

Table 3: Outcome of the qualitative matrix analysis - PBT scored the highest points, followed by PP and POK. 

Funnel stage 4: Testing, selection of material and vendor

In the previous steps, we exclude PA 6.6. due to the potential of being colored by kitchen foods and liquids. Also, Polycarbonate was excluded due to low flow and difficult part filling. Now, in Funnel step 4, PBT, PP, and POK will be tested. In this test series, simple ISO based tests are one part, however the major knowledge on the material performance comes by making prototype parts and assembling them into a part group. 

Major tests include safety tests according to the IEC, and CEE, as well as long-term testing. Long term endurance testing is done in two phases and represents 10 years of life time. In phase one, prototypes of all parts with all three materials are done, including the base plate. Then, water in the tank is overheated and kept for 20 minutes at the high temperature. Then, in phase two, the device is allowed to cool down for 5 minutes and the tank is refilled. This is repeated 7.000 times. This long-term test allows access to things such as deformation, warpage, coloring, material change, and embrittlement of the material. As a result, PBT performed well. PP and POK performed well too, however the design of the part needs to be adapted to compensate for higher shrinkage and warpage. The design of the coffee machine gets more complex by using PP and POK, in order to have the same part quality as with PBT. It is challenging to achieve the same part performance with a material which has a lower overall performance profile. However, with good training in part design and part optimization, materials such as PP and POK are replacing more and more expensive engineering polymers. 

Conclusion

In conclusion, PBT can be used for the premium segment of filter coffee machines, and PP, as well as POK can play an important role in the more mass market application with more price sensitivity. 

More polymer material selection examples using the funnel approach can be found here and below:

I offer to select the optimal polymer for your project, doing the polymer material selection together with you, and also teaching polymer material selection as a training in a group - let me know how I can help you here.

Thanks for reading and #findoutaboutplastics

Greetings

Literature: 
[1] https://kdfeddersen.com/de/produkte/polymere/polyketon#Eigenschaften
[2] https://www.campusplastics.com/campus/en/datasheet/Ultradur%C2%AE+B+4450+G5/BASF/20/401a0566
[3] https://www.borealisgroup.com/products/product-catalogue/bh348mo
[4] Bednarz J: Kunststoffe in der Elektrotechnik & Elektronik



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Monday, 3 February 2025

Plastics Industry - How to Kickstart Innovation in 2025

Hello and welcome to a new post. Today we discuss how to kickstart innovation in the plastics industry. Why? Most of us find ourselves in the position that in the 1st quarter of the business year the management staff and executives will present to you some expectations regarding innovation, especially how innovation will drive further business growth.

This can look like:

-Five new product ideas

-Three new programs started

-Minimum one new innovation project as part of the bonus goals

-Several patent applications.

It is combined with sentences like: ‘This year we need a push from our technology division to drive business forward’.

Also, emerging global megatrends, the fear of recessions and losing of market share increases the uncertainty at management level. In other words: now we must innovate to keep the business afloat!

It is in our hands to fulfill these expectations

How to start? Review the 4 types of innovation

Greg Satell, author of  Mapping Innovation created the 2x2 Innovation Matrix, which helps us to identify the right type of strategy to solve a problem. The Innovation Matrix is linked to two questions:

1) How well can the problem be defined?

2) Who in the organization is best placed to solve the problem?

Figure 1 shows the 2x2 Innovation Matrix which includes basic innovation, breakthrough innovation, sustaining innovation, and breakthrough innovation.

Figure 1: Kickstart innovation - start by reviewing the 4 types of innovation (2x2 Innovation Matrix) [1].

Basic Innovation:

  • Driven by fundamental research and the discovery of new phenomena.
  • Leads to new knowledge and fuels the creation of novel applications.
  • Accessible to small and medium sized enterprises (SMEs) through online resources and collaborations with scientists.

Breakthrough Innovation:

  • Solves complex problems by combining expertise from different fields.
  • Emphasizes cross-domain knowledge exchange and open innovation.
  • Example: Using the behavior of clams to inspire a novel sensor design.

Improvement Innovation:

  • Focuses on incremental enhancements to existing products.
  • Aims to increase profitability through higher prices and added features.

Disruptive Innovation:

  • Occurs when market shifts render established products obsolete.
  • Requires a fundamental shift in business models and operational approaches.

How to apply this to your organization

First step is to locate where you and your innovation challenges are situated in the Innovation Matrix. Once done, it is time to apply tools which are especially suitable for each of the innovations:

-Basic innovation:

• Dedicated research departments in large corporations

• Accessing highly specialized research through local universities

• Academic partnerships

-Breakthrough innovation:

• Open Innovation Method Framework designed by Roland Harwood [2] consisting of degree of

openness (Open inside; Outside in; Inside out) on the x-axis and stage of innovation (explore, extract,

exploit) on the y-axis.

-Improvement innovation:

• Strategic road mapping

• Traditional R&D labs

• Acquisitions allowing to bring new know-how and skill sets into the organization

• Design thinking methods

-Disruptive innovation:

• The Lean Start-Up method with its three key principles (hypotheses testing with a framework

called a business model canvas; listening to customers and incorporate their feedback, and agile

development which allows for short, iterative product development cycles)

• Value Proposition Canvas is a framework which helping you to ensure that your product/service is

positioned around what the customer values and needs.

Generally, businesses emphasize the efficiency and good enough type of innovation since one can gain fast results, which can be measured well too. This can be a good start for you too, however gradually focus should be put on the four major types of innovation to uncover the next game changer in your industry.

Ready to revolutionize innovation in your organization? 

My new book, How to innovate when you must, is your guide. It contains 15 actionable strategies to ignite creativity, spark new ideas, and drive business growth. Additionally the included innovation readiness assessment will help you pinpoint your organization's current innovation maturity and guide you toward a more innovative future.

Thanks for reading & #findoutaboutplastics

Herwig Juster

Literature: 

[1] https://www.amazon.co.uk/Mapping-Innovation-Playbook-Navigating-Disruptive/dp/1259862259

[2] https://theharwoodinstitute.org/approach


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Monday, 13 January 2025

Injection Moulding of PolyArylAmides (PARA; PA - MXD6) - Avoid this important mistake with the mould and melt temperature

Hello and welcome to a new post. Today we discuss the crystallization behavior of PolyArylAmide (PARA; PA MXD6), a semi-crystalline high performance Polyamide. Learn the ABCs of PARA here and the differences between PA and PARA here. 

PARA combines excellent surface finish with high glass fiber loadings, outstanding stiffness (over 38 GPa possible), outstanding strength (>300 MPa possible), low creep, excellent flow (thin walls), and a CLTE which is similar to that of metal. 

Crystallinity is Key

PARA's performance heavily relies on the level of crystallinity achieved during processing. Higher crystallinity leads to improved physical properties, dimensional stability, and high-temperature performance.

Semi-crystalline materials like PARA require temperatures above their glass transition temperature (Tg = 85°C for PARA) to crystallize effectively. Mould temperature directly influences the material's temperature during solidification. Studies indicate that a mould temperature around 120°C is necessary, especially for thin-walled parts, to maximize crystallinity. Figure 1 shows the relative crystallinity of PARA (PA MXD6) as a function of mould temperature [1]. The measured part had a thickness of 3 mm and samples from the core and from the skin where checked for crystallinity. 

Figure 1: Relative crystallinity of PARA (PA MXD6) as a function of mould temperature [1].

DSC analysis as an effective tool to check crystallinity of semi-crystalline polymers

Differential Scanning Calorimetry (DSC) can assess crystallinity in an effective way. An exothermic peak in the DSC curve around 80-120°C signifies incomplete crystallization during injection moulding. Figure 2 shows a DSC curve of a fully crystallized and incomplete crystallized PARA. In the area of the Tg (85°C), an exothermal peak is visible, indicating that the tool temperature during moulding was too low. Sometimes lower tool temperatures are applied to decrease cycle time or to decrease shrinkage and warpage effects. However, this comes at the cost that the part which uses a high performance polymer, will not perform like a high performance polymer. 

Figure 2: Comparing a DSC curve of a fully crystallized and incomplete crystallized PARA [1].

The maximum crystallinity of PARA can vary depending on factors like processing conditions, specific grade of PARA, and additives. PARA typically exhibits crystallinity levels ranging from 40% to 60%.

What are factors influencing crystallinity in general?

  • Moulding temperature: As discussed, high mould temperatures (> 120°C) are crucial for achieving higher crystallinity.
  • Cooling rate: Slower cooling rates generally allow for more complete crystallization.
  • Nucleating agents: Adding nucleating agents can significantly enhance crystallinity rates.

What are the consequences of low mould temperature with PARA?

There are five issues related with low mould temperature which I come across over and over again when moulding PARA: 
  • Increased water absorption: Higher amorphous content leads to increased water absorption, affecting dimensional stability.
  • Post-Crystallization and distortion: Incomplete crystallization can lead to post-crystallization after moulding, causing part distortion.
  • Higher creep: Parts moulded at lower temperatures exhibit increased creep behavior.
  • Poor surface finish: Irregular surfaces and fiber appearance can result from insufficient mold temperature.
  • Ejection issues: Very low mould temperatures can lead to extremely low shrinkage, hindering part ejection.
How to measure the tool surface temperature best?

A practical option to measure the surface tool temperature is to use a non-contact IR temperature measurement device. They cover a temperature range from -50°C up to 600°C and can be fast applied to many surfaces. 

Melt temperature and residence time are important too

Apart from applying the correct mould temperature with PARA, checking the melt temperature and residence time is important too. Too high melt temperatures (>285°C) in combination with long residence time can lead to thermo-degradation. This is not only affecting the base polymer, in our case PA-MXD6), but also the processing additives and other additives. Aim for a residence time of 5 minutes, with a maximum residence time of PARA of 10 minutes. 

If you are not sure about the residence time, you can easily estimate it with this calculator.

The upper DSC curve in Figure 3 shows again a fully crystallized PARA with two melting peaks. The first, larger melting peak belongs to the PARA base resin and the second smaller belongs to an additive which is used in the formulation (most probably a processing aid). The lower DSC curve shows PARA when exposed to high melt temperatures (>285°C), combined with too long residence times (>10 minutes). The second smaller melting peak disappeared indicating that termo-degradation did take place. This in turn has an influence on the final mechanical properties of the moulded PARA part. Also, it can happen that the additive melting peak is overlapping with the main melting peak of the PARA, making it harder to detect it.

Figure 3: Thermo-degradation of additives in the PARA compound formulation caused by too high melt temperature and residence time. 

Conclusion

High mould temperatures (>120°C) are crucial for processing PARA (PA MXD6) compounds. They ensure optimal crystallinity, leading to superior mechanical properties, dimensional stability, and overall part performance. Also, check from time to time the mould surface tempature to ensure that there is a match between set temperature vs. real temperature. 

I hope this blog article has been helpful. If you have any questions, please feel free to leave me a message.

Thanks for reading & #findoutaboutplastics

Herwig Juster

Literature: 

[1] https://www.syensqo.com/en/brands/ixef-para/documents

[2] https://www.findoutaboutplastics.com/2023/11/design-properties-for-engineers-abcs-of.html

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Thursday, 9 January 2025

10+ Key Considerations for Selecting the Optimal Polymer Material I Polymer Material Selection Tip

Hello and welcome to a new post on polymer material selection. In the world of plastics, selecting the right polymer material for your project is crucial. The wrong choice can lead to costly mistakes, product failures, and even safety hazards. To help you make the right decision, I have outlined 10 key considerations to keep in mind (Figure 1):

1. Cost: Polymer materials come in a wide range of prices. It is important to balance price and performance when making your selection. Consider factors such as processing and tooling costs, as well as the cost per volume rather than weight.

2. Environmental Exposure: The end-use environment of your product will play a major role in determining the suitability of a polymer material. Consider factors such as temperature, UV light, and chemical exposure.

3. Material Property Data: Gather as much data as you can about the material's properties, including short-term, long-term, and cyclic properties. This information can be found in technical data sheets, material suppliers, and databases such as CAMPUS (Check out my collection of databases here).

4. Processing Data: Ensure that the material you select is compatible with your chosen manufacturing process, such as injection molding or extrusion. Also consider factors such as part design and compatibility with other materials.

5. Appearance: If the appearance of your product is important, be sure to select a material that meets your aesthetic requirements. This includes factors such as surface haptics, finish, and color. Using glass-fiber reinforced compounds will have lower surface aesthetic compared to unfilled polymers. 

6. Agency Approvals: If your product will be used in a regulated industry, such as food, medical, or automotive, you will need to ensure that the material complies with all relevant regulations and standards.

7. Industry Specifications: Some industries have specific requirements for polymer materials. Be sure to check for any relevant industry specifications before making your selection.

8. Actual Requirements and Load Cases: It is important to map out the true load cases and material requirements for your specific application. This will help you select a material that can meet the demands of your product.

9. Prototype Testing: Before making a final decision, it is always a good idea to test prototypes of your product to ensure that the material you have selected performs as expected.

10. Choosing Suppliers: When selecting a polymer supplier, be sure to choose a company that has a broad product portfolio, strong customer support, and a global presence.

Figure 1: 10 key considerations for selecting the optimal polymer - polymer material selection tip.


Update: based on the community feedback (thanks !!), I added sustainability/circularity considerations, as well as checking for Intellectual Property (IP) protection (Figure 2).

Figure 2: Extended key considerations for selecting the optimal polymer - polymer material selection tip.

By following these 12 key considerations, you can make sure that you select the optimal polymer material for your project. This will help you avoid costly mistakes and ensure that your product is successful.

In addition to the above, it is also important to consult with a polymer expert. They can help you understand the different types of polymer materials available and make recommendations based on your specific needs.

Conclusion

Selecting the optimal polymer material for your project is an important decision. By following the tips in this article, you can make sure that you choose a material that is both cost-effective and suitable for your application.

I hope this blog article has been helpful. If you have any questions, please feel free to leave me a message.

Thanks for reading & #findoutaboutplastics

Herwig Juster

Literature: 

[1] https://www.polymermaterialselection.com/start-the-book

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Thursday, 2 January 2025

Rule of thumb: Water Lilies and Polymer Melts - Both Show Exponential Behaviours

Hello and welcome to the first post of the new year 2025! I hope you had a great Christmas break and I welcome you all back to a new exciting year of polymer engineering topics. 

Let us start with a Rule of Thumb post (check out my other Rules of Thumb posts here). We are living in non-linear, exponential times, which can be seen daily by the rapid advancements in technology, from Artificial Intelligence (AI), to the stock market. 

For example, if you take the compounded interest of the S&P 500, we see an exponential growth over time. Compounded interest is for Warren Buffet the key for wealth building.

For our brain it is harder to imagine exponential relations, since for us humans, linear thinking is the main "operating model"

There are lots of examples of exponential behaviour: 

  • Population growth
  • Growth of cells
  • Spread of a disease in a pandemic
  • Financial - compounding interest rates

Water lily and exponential growth

A good way to represent exponential behaviour is by looking at a pond where water lilies are growing. Water lilies double in area each day, resulting in an exponential growth. Let us imagine the following: the water lilies take 30 days to cover the whole pond. When will they cover half of the lake? 

Exactly, on the twenty-ninth day. 

Example from polymer engineering: power-law of polymer melt viscosity

Also in the plastics industry and polymer engineering, a well known example of exponential behaviour is the viscosity of polymer melts (Figure 1). 

Figure 1: Water Lilies and Polymer Melts - Both Show Exponential Behaviours.

In general, the viscosity of plastics is a function of shear rate, temperature, pressure, and chemical composition. 

At low shear rates, polymer melts show a linear behaviour (= Newtonian behaviour). In the lower shear rate region, the viscosity is independent of the shear rate.

The viscosity reaches a level which is referred to as zero-shear viscosity. 

At higher shear rates, the Power law behaviour takes over and the viscosity decreases with increasing the shear rate following a negative slope of (n-1), where n is the Power-law index.

This quantitative relationship is represented by the Power-Law model, where n is the Power-law index and k is consistency (Pa*s); Typical n values of polymer melts are between 0.2 and 0.6.

Conclusions

Exponential behaviours are dominating not only our daily life, however also the plastics industry and polymer engineering topics. It is important to have a certain awareness about such behaviours to not be suppressed and use the exponential times in our favours. 

More Rule of Thumb posts can be found under “Start here”

Latest Rule of Thumb posts:

Rule of Thumb in Polymer Injection Moulding: Fast Estimation of Cooling Time

Rule of Thumb in Polymer Engineering: How Economy of Scale Can Lower Costs

Rule of Thumb: Dealing with Weld lines in Polymer Injection Moulding

Thanks for reading & #findoutaboutplastics

Herwig Juster

Literature: 

[1] https://www.forbes.com/sites/bill_stone/2024/08/25/warren-buffetts-secret-formula-for-wealth-creation/

[2] https://www.azom.com/article.aspx?ArticleID=19175



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