UV-stabilization of Polyamides (aliphatic and semi-aromatic) - Effective Protecting of Applications against Exposure to Weather

Hello and welcome to this log post in which we have a look at the UV-stabilization of Polyamides and how effective protection of your applications against exposure to weather can be achieved. 

In a past post we already discussed the weather and UV resistance of styrene copolymers and PMMA. 

In case one of your requirements of your application is long-term outdoor usage, then additional protection considerations of your polymer need to be taken into account during polymer material selection. 

What is the difference between UV Stabilized and UV Resistant?

UV stabilized:  adding stabilizer to your base polymer in order to have protection towards long-term degradation from UV light. They prevent damage by absorbing or screening out UV radiation. The best results being achieved with carbon black.

UV resistant: there are polymers which are inherently resist against UV rays and prevent UV degradation. Examples are polymers such as PMMA and high performance polymers (PEEK, PAI, PPS, PEI, PBI).

UV stabilization of Polyamides

For aliphatic Polyamides such as PA 6.6, adding 2 wt% of carbon black is resulting in a good protection against UV radiation. 

Same is valid for semi-aromatic Polyamides such as the PolyArylAmide (PARA; MXD6), where 2 wt% up to 5 wt% will result in an excellent UV protection. 

Example cable tie fasteners used for terrestrial photovoltaic (PV) modules- PA66 vs PA66 UV stabilized

HellermannTyton and Germany’s Fraunhofer Institute for Solar Energy Systems ISE investigated the impact of their cable tie fasteners which are used to fix cables of PV modules [3].  The test was 1,600 hours long using a test chamber were the cable ties were exposed to a UV dose of 156.78 kWh/m2 (equals the natural solar irradiation of 1,000 kWh/m2 per year). Altogether, this testing time corresponds to 3 years of outdoor exposure. The cable ties are made out of standard PA66, UV stabilized PA66, and PA11.

Figure 1 shows the results of the test, which indicates a reduction of loop pull strength of around 86% for the standard PA 66. The reduction of the UV stabilized PA 66 is minimal and the PA11 even shows a constant performance, which makes the PA11 a suitable outdoor material without needing too much additional protection. 

Figure 1: Results of the 1600 hours UV test of PA66, PA66 UV stabilized and PA 11 cable ties [3].

Thanks for reading and #findoutaboutplastics

Greetings 

Herwig Juster

Interested in having a second opinion on your material selection and high performance polymers, including price evaluation or  discuss with me about your current 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.

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

Interested in our material solutions - check out our product page here

My YouTube channel

My personal website

Literature: 

[1] https://www.usplastic.com/knowledgebase/article.aspx?contentkey=601

[2] https://wurth-international.com/app/uploads/2016/10/CableTies_Technical_Information_2011.pdf

[3] https://blog.hellermanntyton.com/markets-and-industries/1275/uv-stability-hellermanntyton-products-tested-fraunhofer-ise

Pumping Plastics 2023 - My New Book "Pumping Plastics" is Now Available as Paperback Worldwide on Amazon!

Dear community, 

welcome to this special book update! 

Pumping Plastics 2023 is now available as book

The waiting has an end - Pumping Plastics 2023 book is available as paperback. On 185 pages it contains over 50 posts on various polymer engineering topics such as 

-polymer material selection examples, 

-high performance polymers (PARA and PPS), 

-design properties for plastics professionals, 

-bio-polyamides, sustainable materials, 

-and three guest interviews. 

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.

Don’t forget to check out the Pumping Plastics book from 2022 here too, as well as my Polymer Material Selection book. 

Thanks and #findoutaboutplastics,

Herwig 

Guest Interview with Harrison McVeigh Carroll, Business Manager for the Plastics and Packaging Industry at Pivot Search

Hello everyone and welcome to this guest interview. Today I present to you Harrison McVeigh Carroll who is Business Manager for the plastics and packaging industry at Pivot Search, which is a recruitment business that embraces flexibility, autonomy, trust & innovation.

In this guest interview, we have the chance to learn about the current recruitment industry, and in particular the plastics industry, as well as the value he brings to the plastic industry networks.

Enjoy the interview!

1. Tell us about yourself, your current role, and your company Pivot Search.

Business Manager at Pivot Search leading the industrial team and with 6 years experience recruiting in the plastics and packaging space globally. We are in our 4th year as a business and try to do things differently, our unique model hires only experienced, successful recruiters who get given complete flexibility in regard to where they work and as a company have gone from strength to strength focusing on developing relationships with our clients and are continuing to do so!

2. What trends are you currently seeing in the recruitment industry, and in particular the plastics industry? 

In the Plastic industry in the past 12 months I have seen a huge change in the market to being candidates lead. What I mean by this is experienced candidates with a high technical or commercial skillset in compounding, high performance plastics and additives for example are so in demand that they have more choice than ever when seeking a new role. This is leading to companies needing to be more agile, it is not enough anymore to set guidelines for a position and expect candidates to be interested due to simply the name of the company alone. Depending on particular role, candidates are not needing to relocate, take less than a 10% pay increase or settle for less in any sense.

The companies that are realising this, who are moving quickly and not leaving candidates waiting due to this shift in the market, are the ones who are winning the talent in most cases.

I also believe that the value of the plastics industry which I know your Blog is dedicated to is solidifying the industry. A lot of people I speak with are noticing the upward market trend of using the material, which at one stage in the not-so-distant past was seemingly becoming the 'enemy' to things like global warming with its links of the obvious difficulties to reuse. However, the alternates have been proven to not be all that and this goes beyond just Packaging the obvious example. The uses in construction, Aerospace and Automotive industries to name just a few prove that plastic is vital in our everyday life and when used correctly there isn't a material that can compare – the industry is certainly not going anywhere, and the growth plans and manufacturing increases from a couple of the companies I have been working with this year alone so far are a great example of that.

3. What are the reasons and rationale behind these trends?

I think we are now feeling the market boom following COVID. Just a couple years on when the market was tough certainly from a recruitment industry, companies in most part 'shut up shop' and a lot of promoting from within and being agile with the team they had. And from a candidate side it was risky to make a move and suddenly be in probation period in a new role, if something went wrong you would be the first line of fire if something goes badly from a business aspect. But now this has settled massively, and I know myself life is more or less the same as pre covid. And the market is reflecting this, but different to before it seems a much larger % of the market are looking to hire all at once and this has lead to candidates having that choice which means it is companies who are having to change their methods, or face being left behind and missing out on the best talent.

4. Based on the aforementioned information, what value can you bring to the plastic industry networks to improve the situation?

As always throughout my career I have tried to add more than just being a recruiter to my network. Whilst I will never claim to be a chemist or engineer, I try and learn the industry going the extra mile examples being the articles I have carried out and talks with people like yourself, and other KOL in the industry. In addition to this, it is important I don't lose sight of my role and what companies employ me and the team at Pivot to do. To bring top talent in the industry to them and the best way we can break this down is for starter learning the need of the company, where, who and what product experience is a nonnegotiable. Once this step is done, now we face the above-mentioned challenge of seeking the candidates. Using my network which I have built up recommendations is a big way I am able to either source candidates or be pointed in the right direction.

Screening the candidates specifically to companies need is then the leg work required, a linkedin search is no longer enough in this very competitive recruitment space. And results speak for themselves, we are working across Central Europe and North America with some of the best compounding, packaging and high-performance polymer businesses there are and building relationships that mean we are their first port of call when they face a challenge to source candidates.

5. Where can the readers find out more about you and your offers for the plastic industry?

Reaching out on LinkedIn is always the best place to start. Whether it's a candidates seeking a new role or a company looking to bring great talent, its always great to connect whether it be for now or in the future.

That was the guest interview with Harrison form Pivot Search – many thanks Harrison for our exchange on topics such as recruiting trends in the plastics industry and ideas on how to improve current challenges in the staffing of companies.

Thanks for reading!

Greetings and #findoutaboutplastics

Herwig Juster

Design Properties for Engineers: Coefficient of Linear Thermal Expansion (CLTE) of Glass Fiber Reinforced High Performance Polymers as a Function of Temperature

Hello and welcome to a new post in which we discuss the coefficient of linear thermal expansion (CLTE) as an important design data for polymer material selection. In general, CLTE is a performance indicator for the dimensional stability of materials when they are exposed to temperature. In general, plastics expand under the influence of temperature. The expansion is big compared to other materials. Length changes of millimetres at a temperature difference of 10 Kelvin are not unusual.

Furthermore, the effect of thermal expansion is different depending which polymer processing technique is used (injection moulding vs. extrusion). Different values are obtained in polymer flow direction and perpendicular to the flow direction. Thermal expansion is lower in flow direction compared to perpendicular to it.

Altogether, CLTE in flow and perpendicular direction is influenced by: 

-filler type, 

-filler amount, 

-the flow orientation (anisotropy),

-and the temperature.

CLTE (Coefficient of linear thermal expansion) of glass fiber reinforced high performance Polymers as a function of temperature

Knowing the CLTE of reinforced high performance polymers as a function of temperature allows you to better assess the suitability for your application. In case the continuous use temperature of your application is between 150°C and 160°C, the CLTE values in this range are helpful. 

Figure 1 shows the CLTE of glass fiber reinforced Polyphenylene sulfide (PPS), Polyphthalamide (PPA), Polyethersulfone (PESU), and Liquid Crystal Polymer (LCP) in flow direction. LCP has an extremely low CLTE (similar to metals) and it behaves almost linear over the temperature change However, in perpendicular direction, similar to other properties, the CLTE of LCP becomes larger over the temperature due to the anisotropy with glass fiber filling. 

Figure 1: CLTE (Coefficient of linear thermal expansion) of selected high performance polymers as a function of temperature [1]. 

CLTE of metals compared to high performance polymers - Example PEEK-GF 30wt%

Figure 2 compares the CLTE of a Polyether ether ketone (PEEK) with a 30 wt% glass fiber reinforcement to a Zinc alloy, an Aluminum alloy, and a stainless steel [2]. PEEK-GF30 wt% is able to compete in terms of CLTE in flow direction with the aforementioned metals which enable metal replacement or overmoulding of metal structures. A similar case is true for Polyarylamide (PARA; MXd6) with 50 wt% glass fiber reinforcement which has in flow direction a similar CLTE as steel and brass [3]. 

Figure 2: CLTE of PEEK-GF30 wt% as a function of temperature vs. metals [2].

Figure 3 compares the CLTE of PEEK to PEEK-GF 30wt% and PEEK-CF 30wt% as a function of temperature. It can be seen that carbon fibers are more effective in reducing the CLTE. At temperatures of 200°C, the differences between GF and CF are minimal, however compared to PEEK unfilled they are large.

Figure 3: Comparsion CLTE of PEEK vs. PEEK-GF 30wt% and PEEK-CF 30wt% [2].

Additional posts on this topic: 

Plastic Part Design Properties for Engineers - CTE/ CLTE of Polymers, Mineral Fillers and Metals

Design Properties for Engineers: Coefficient of Linear Thermal Expansion (CLTE) of High Performance Polymers

Plastic Multipoint Design Data - CLTE of Polymers as a Function of Temperature

Thanks for reading and #findoutaboutplastics

Greetings,

Herwig Juster 

Interested in having a second opinion on your material selection and high performance polymers, including price evaluation or  discuss with me about your current 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.

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

Interested in our material solutions - check out our product page here

My YouTube channel

My personal website

Literature: 

[1] https://www.sumitomo-chem.co.jp/sep/english/products/lcp/lcp_bs_sunpo.html

[2] Ketaspire KT-820 GF30: https://www.solvay.com/sites/g/files/srpend221/files/2018-07/ketaspire-peek-design-and-processing-guide-en.pdf

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

High Performance Polymers for Medical Technology Applications - Gradical Podcast Episode Nr. 21: Herwig Juster & Lucas R. Pianegonda

High Performance Polymers for Medical Technology Applications - Gradical Podcast Episode Nr. 21: Herwig Juster & Lucas R. Pianegonda

Hello and welcome to this new post. I was invited to the Gradical Podcast and I talked with the host Lucas about high performance polymers in medical technology field. Als, I gave a general overview on high performance polymers, what are the most important ones and in which industries, apart from medial, they are used. Episode is in German language.

Here the link to the Episode. 

Thanks and #findoutaboutplastics

Greetings,

Herwig Juster 

Interested in having a second opinion on your material selection and high performance polymers, including price evaluation or  discuss with me about your current 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.

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

Interested in our material solutions - check out our product page here

My YouTube channel

My personal website

Guest Interview with Lucas R. Pianegonda, Managing Director and Lead Plastic Expert at Gradical: "Form a better world – with plastics"

Hello everyone and welcome to this guest interview. Today I present to you Lucas R. Pianegonda who is Managing Director and Lead Plastic Expert at Gradical GmbH, which supports you in the medical sector with plastics evaluation, material compliance or material testing.

In this guest interview, we have the chance to learn about medical grade plastics and their selection, what their mantra “Form a better world – with plastics” means, and how one can incorporate sustainability in the medical device environment. 

Enjoy the interview!

Tell us about yourself, your current role, and your company Gradical GmbH. 

I’m a medical grade plastic expert and I help medical technology companies to choose the right plastic for their applications. This regarding their technical, regulatory and sustainability requirements. I studied material science at ETH Zürich and then went to industry. Initially I worked at a plastic manufacturing company EMS Chemie where I was responsible for material testing and material data models. I then went on to work for a company that produces two component mixing and storage solutions – medmix. There I was responsible for plastic material selection, material compliance and sustainable materials. Armed with this experience I founded Gradical in 2022. Gradical is a consultancy for all things medical plastics and I am simultaneously lead plastic expert and managing director. 

A main mantra of yours is to “Form a better world – with plastics” - How do you achieve this and what are your main service and solution offerings?

The goal of medical technology companies is to improve the lives of people. But medical technology companies are facing huge challenges. The regulatory landscape, new sustainability requirements and skilled labor shortage to name a few. Plastics currently have a bad reputation which is undeserved in my opinion. I think plastic are contributing in bringing said medical solutions to market. Medical technology companies are in need of plastic know-how in order to get their product to market and our services enable this. We offer services and trainings regarding plastic evaluation, material compliance and material testing. Our two standard trainings “Sustainable plastics in medical technology” and “regulatory aspects of plastic selection” are very popular. This shows that people are interested in these topics and want to learn more. 

How do you define the term “Medical Grade Plastic” and what are the most used Medical Grade Plastics in which applications?

“Medical Grade Plastics” is no protected expression. So a lot of plastics manufacturers call their materials “medical grade” as soon as they have tested some aspects of biocompatibility and there is an application in the medical field. However in 2017 the VDI has put together a guideline on what a medical grade plastic is. The main aspects of the definition are change management, regulatory support and supply security. I think it meets the requirements of medical technology companies and therefore this is the definition I always use.

As for main plastics and their applications: The most used plastics in medical technology, as in all applications, are commodities such as PP, PE and PVC. PE is used for packaging, caps and closures. PP is used for syringes and other disposables. PVC is used for tubing, blood bags, blisters or also for hospital flooring. Engineering plastics and high performance plastics are used where the commodities do not meet the requirements. Examples include clamps from PA6, Lenses from PMMA, surgical devices made from PPSU or implants made from PEEK. The class of thermoplastic elastomers also should not be underestimated too. They are used in applications where softness and elasticity is needed which includes tubing, handles and sealings. 

Industries are gradually switching to more sustainable material offering for their products. How is this trend affecting the material selection in the medical device industry in terms of using sustainable plastics alternatives such as recycled, bio-based or biodegradable plastics?

This is one of our expertise. Medical device companies start to look into sustainability more and more. They are still hesitant to using sustainable materials due to the major hurdles to bringing a device to market. If they bring something to market it needs to be a success and therefore they don’t want to make the wrong decision. There are however pioneers that are already using biobased plastics or even recycling plastics in their medical device. Biodegradable plastics seldomly bring advantages over biobased conventional plastics, therefore I think they will stay in niche applications. Recycling plastic have the issue of needing much more quality control and risk management measures, a topic that is already unclear for conventional plastics, this leads to the conservative approach of not using recycled plastics in medical device. I often hear that recycled plastics cannot be used due to “regulatory requirements” this is simply not true. A medical device company has to show that the recycled plastic yields to a safe and effective medical device. Most companies do not know how to show this, not that it is an easy task, and therefore decide against using recycled plastics. The most promising approach to sustainable plastics in the medical field however is the so called, mass balance approach, were the same plastics can be used as drop in solutions for existing grades. This with a vastly improved footprint. Since we believe in this approach we started offering project support and coaching for companies willing to obtain mass balance certifications such as ISCC+.

How do you see “Design for Recycling” in the field of Medical Grade Plastics? In addition, are there already some circular economy examples where medical grade plastics find a second life? 

Medical applications cause a significant portion of the plastic waste. I’ve seen studies that estimate it at 3-5 % of the total plastic waste. Another study showed that 80% of plastic waste in hospitals is neither contaminated nor infectious and therefore could be recycled. I think recycling of medical waste has a future. This also means that medical technology companies should think about how to design medical devices, pharmaceutical packaging and in-vitro diagnostics such that they can be recycled. As for examples, Novo Nordisk has launched a take back program for their self-injection pens which they then recycle. Currently there are still down cycling the materials into chairs, but it would not surprise me if it will be possible in the future to manufacture new pens from the recycled material. We have to be cautious tough, plastics are not infinitely recyclable. At some points properties degrade and we need to complement this with other solutions such as biobased or chemically recycled virgin-like plastics.

Where can the readers find out more about you and your offers for the medical device industry?

I mean the best source would definitely be to contact my for a quick exchange. I love meeting new people and whoever is interested in our services, I’m very happy to present them to you. The other obvious source is our website: www.gradical.ch which has gotten an upgrade recently. For the more auditive predisposed: we do also have a podcast Gradical Podcast - Der Podcast zu Kunststoffen in der Medizintechnik | Podcast on Spotify where I interview experts on different topics related to plastics in medical device. The reader might be interested in hearing your interview about high performance plastics. 

That was the guest interview with Lucas R. Pianegonda from Gradical – many thanks Lucas for our exchange on topics such as Medical Grade Plastics and their selection, and your motivation to “Form a better world – with plastics” .

Thanks for reading!

Greetings and #findoutaboutplastics

Herwig Juster

Design Data for PolyArylAmide (PARA; PA MXD6) Selection: Mechanical Properties as Function of Temperature and Humidity

Hello and welcome to this post in which I present additional multipoint data of reinforced PolyArylAmides (PA MXD6; PARA) as support during your material selection journey. 

Basic data of PARA I discussed in the following posts: 

Design Properties for Engineers: The ABCs of Polyarylamide (PARA; MXD6)

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

In this post, we focus on: 

• Tensile strength properties as a function of temperature
• Flexural strength properties as a function of temperature
• Impact properties as a function of temperature
• Tensile strength and modulus at equilibrium as a function of relative humidity

Tensile strength properties as a function of temperature

Figure 1 presents the tensile strength and tensile modulus as a function of temperature of a PARA with 50 wt% glass-fiber reinforcement (DAM = Dry as moulded). We can see a decrease in strength with increasing temperature and once we reached the glass transition temperature (85°C), this decrease becomes sharper (semi-crystalline region is still providing strength). 

Figure 1: Tensile strength properties of PARA GF 50 wt% as a function of temperature [1].

Flexural strength properties as a function of temperature

Figure 2 shows the flexural strength and flexural modulus as a function of temperature of a PARA with 50 wt% glass-fiber reinforcement. Flexural strength values are higher compared to tensile strength values since this test combines compressive, tensile, and shear stresses (ISO 178 or ASTM D790) leading to a greater plasticizing effect than in a pure tensile test. 

Figure 2: Flexural strength properties of PARA GF 50 wt% as a function of temperature [1].

Impact properties as a function of temperature

Figure 3 shows the Izod impact strength (notched and unnotched) of a 50 wt% glass fiber reinforced PARA compound. The figure illustrates how temperature affects the PARA compound's ability to withstand impacts. We can see that this characteristic essentially stays unchanged below the glass transition threshold of 85°C. The viscous condition of the amorphous portions causes an increase in impact resistance above this temperature.

Figure 3: Impact properties of PARA GF 50 wt% as a function of temperature [1].

Tensile strength and modulus at equilibrium as a function of relative humidity

Figure 4 presents the tensile strength at equilibrium and Figure 5 the tensile modulus at equilibrium of a PARA-GF 50 wt%, PARA-GF 60 wt%, and PARA-GF 50 wt% with impact modification. All aforementioned PARA compounds use a PA MXD6 resin which contains amide functions. In case the amide function is exposed to water, a reversible plasticizer complex is formed (as with all Polyamides). The water absorption leads to three major consequences which need to be considered during the design phase:

-The plasticzing leads to a reduction in mechanical properties (as shown in Figure 4 and 5).

-Swelling of the material and as a consequence, dimensional changes of the part

-Reduction in the glass transition temperature. PARA-GF 50 wt% which is saturated with water reduces its glass transition from 85°C down to 25 °C. This is influencing the creep resistance of the material and in case the part was injection moulded below 120°C, post-crystallization takes place. This leads to a deformation of the part.  

Therefore, testing the PARA compound at actual use conditions, especially if permanent water contact is present, is crucial in order to avoid problems related to water uptake. 

Figure 4: Tensile strength at equilibrium of PARA compounds as a function of relative humidity. [1]

Figure 5: Tensile modulus at equilibrium of PARA compounds as a function of relative humidity [1].

Conclusions

The advantage of having multipoint mechanical properties of PARA compounds plotted in a graph is that it enables a better decision making during the part design and material selection phase. 

More on high performance polymers can be found here and here.

Thanks for reading and #findoutaboutplastics

Greetings,

Herwig Juster 

Interested in having a second opinion on your material selection and high performance polymers, including price evaluation or  discuss with me about your current 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.

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

Interested in our material solutions - check out our product page here

My YouTube channel

My personal website

Literature: 

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

[2] https://www.albis.com/dam/jcr:3e0fc093-ea63-466f-9a67-43f796bc08ea/Ixef-PARA-Design-Guide_EN.pdf