Monday, 8 August 2022

Plastic Part Design Data - Thermal Conductivity of Polymers as a Function of Temperature

 Hello and welcome to a new blog post. Today we discuss the thermal conductivity of amorphous and semi-crystalline polymers (unfilled; only the polymer resin) as a function of temperature.

The importance of multi-point data

Multipoint data of different polymer and polymer compound properties prevail information which would otherwise may be overlooked during material selection and product design. 

In other posts we discussed multi-point data such as the DMA results of engineering and high performance polymers. Multi-point data are important for material selection since it has a lot to do with thinking in relationships of time-dependency and temperature-dependency behaviors. Graphically such behaviors can be better accessed. Single point data can lead to misjudgment and negatively impact the material selection process.

Thermal conductivity of polymers was already several times topic on this blog: 

-Thermal conductivity of filled and unfilled high performance polymers

-Thermal conductivity of 96 plastics for EV application design support

-Guest Interview: Max Funck from PlastFormance – “Our patented technology for innovative plastic compounds allows for high filler contents - up to 80% vol.”

-Polymer Chemistry meets A.I. – Finding and Developing New Polymers with Target Properties in the 21st Century

However, in those posts thermal conductivity mostly was discussed as a value estimated at one single temperature. Now we look how the thermal conductivity changes in a temperature range of -150°C and up to 150°C. There is no linear behavior of the different polymers in this temperature range. 

Amorphous polymers: thermal conductivity as function of temperature

Amorphous polymers: thermal conductivity as function of temperature

Semi-crystalline polymers: thermal conductivity as function of temperature

Semi-crystalline polymers: thermal conductivity as function of temperature

Here you can find further design property data of various polymers for your part design and material selection. 

Thanks for reading and #findoutaboutplastics

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.

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

Literature: 

[1] VDI Wärmeatlas

[2] Griesinger: Wärmemanagement in der Elektronik

[3] Hanser Kunststofftaschenbuch


Wednesday, 3 August 2022

Polymer Material Selection: Defining the Part Requirements as Common Starting Point

Hello and welcome to a new post. Today we discuss the starting point in polymer material selection. 

In general there are several procedures for material selection such as the Ashby methodology or my own developed funnel approach

However, all the selection processes and procedures should have the definition of the part requirements as their common starting point. 

How to do it the best? 

Polymer Material Selection - Estimation of product requirements as common starting point

First we have to ask some questions on the functionality of the part. 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?

With the collected answers we can define the part requirements as accurately as possible. Together with the understanding of the differences of thermoplastics (amorphous and semi-crystalline) and thermosets we have an understanding of the performance, thermal and mechanical properties, as well as chemical resistance and processing differences of thermoplastics and thermosets. 

Selection factors - checklist for your material selection 

There are more detailed lists , however in this post we cover the six essential questions on material selection factors. 

1. What is the service environment of your part?

-what is the operating temperature: high, low, duration, thermal expansion

-exposure to chemicals, solvents, lubricants, salt

-exposure to water and humidity

-UV stability for use in outdoor / indoor environment

2. What are the regulatory requirements?

-flammability rating needed such as UL 94 at different wall thickness

-food contact

-fulfillment of medical standards

-any other regulation such as IP 44 for electrical devices

3. What types of load at which service temperature need to be fulfilled?

-continuous load represented by Young modulus and creep resistance

-intermittent load represented by tensile strength

-impact load represented by impact strength

-fatigue represented by cycles to failure for example over a Wöhler curve

4. Other considerations such as: 

-dimensions and tolerances which need to be met

-electrical properties such as CTI, electrical breakdown strength

-wear and friction 

-thermally conductive materials with or without electrical isolation

-aesthetics and colour (relevant for application with food contact, and toys)

-painting and printing 

-life time needs 

5. What is the processing and fabrication method?

-injection moulding, extrusion, thermoforming

-assembling by using screws, laser welding, or adhesives

-secondary operations

6. What are the economic and commercial considerations

-useful to make when material short-list is available

The combination of questions on part functionality and selection factors will help to facilitate your polymer material selection, together with fundamental data in a systematic way. 

Thank you 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.

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

Literature:

[1] GE Plastics - Product Guide

[2] https://www.grantadesign.com/education/students/charts/

[3] https://www.findoutaboutplastics.com/2020/11/plastic-part-failure-part-2-antidote.html

Sunday, 24 July 2022

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

Hello and welcome to a new blog post. In a previous post we discussed the coefficient of linear thermal expansion (CLTE) of high performance polymers such as PPS, PEEK and PVDF already. 

In this post we will introduce the CLTE of commodity polymers, mineral fillers and metals with the focus on how to control CLTE in an optimal way. 

Optimizing the CLTE of polymer compounds - how to do it? 

Comparing the CLTE values of metals, minerals and polymers (Figure 1) we notice that polymers have a factor 3 to 5 times higher CLTE in comparison to metals. Comparing the polymer CLTE with minerals the factor is with 10 even higher [1]. Based on this fact, lowering the CLTE of polymers can be done by mixing them with minerals. Also it is important to use isotopic fillers which result in equal mechanical properties and CLTE in the x,y, and z directions. 

Figure 1 compares the CLTE of unfilled and filled plastics as well as minerals and metals. 

Figure 1: CLTE of polymers, minerals, and metals.

Example of talc filled Polypropylene 

Figure 2 shows the CLTE of PP in comparison with 10 w% and 20 w% talc filled PP. The CLTE could be reduced from 150 to 95 x 10-6 K-1 (36%). 

Figure 2: CLTE of PP and talc filled PP

CLTE can be a critical requirement for enclosed or metal overmoulded parts. Modification of polymers with certain fillers to reduce the CLTE needs to be kept in mind during polymer material selection

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

Literature:

[1] https://phantomplastics.com/fillers-for-cte-clte-modification-of-plastics/

[2] https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

[3] https://www.findoutaboutplastics.com/2020/04/design-properties-for-engineers_28.html


Wednesday, 20 July 2022

Highly Filled PP Compounds - Materials for Improved Flame Retardancy, Cost, and Functionality

Highly Filled Polypropylene Compounds 

Hello and welcome to a new blog post. Today we discuss highly filled PP compounds as enabler materials for improved flame retardancy, cost, and functionality.

Some time an industry colleague said to me that if the application does not have a high temperature and precision demand, most of them will end up made out of Polyolefins (PP, PE): “PP can do the job”.

And we see more and more engineering polymer replacements (PA, PC, PBT) by PP with fillers (functional or non-functional). Therefore, let us have a look at highly filled PP compounds. 

Which types of highly filled Polypropylene are there and what are some major application fields for highly filled Polypropylene?

As a first overview we can cluster them in three groups: 

-Calcium carbonate filled PP: main drive is cost out and improved dimensional stability; calcium carbonate belongs to one of the most used inorganic fillers which increases the modulus of elasticity. Loading levels of 30 parts per hundred result in 11 % by volume. 

-Mineral filled flame retardant PP: main driver  is to comply with more stringent flame retardant requirements; Magnesium Hydroxide (MDH) can be used as flame retardant. 

-Graphite filled PP: main driver are Electrostatic discharge (ESD) applications such as fuel connectors, and fuel cell applications.

What filler levels can be realized?

For reaching certain stringent flame retardancy ratings with PP compounds, filler levels of flame retardant filler MDH can be 60-65% by weight. This would result in a composite density of 1.45 g/cm3. However, the balance need to be found between property reduction and processing capability. 

How to increase filler amounts to improve performance?

New technologies such as the patented PlastFormance technology (Guest interview here) allows loading a base polymer up to 80% weight and keeping still good flow capabilities for injection moulding. 

Examples of PP replacing engineering polymers

Also, we see talcum filled PP (min. 20% by weight) replacing ABS and long-glass fiber filled PP replacing short glass fiber PA.

Key for highly filled compounds is the understanding of filler shape, their size and how their surface is treated to be able to make a proper bonding with the base polymer. Using such compounds helps to enlarge your repertoire for polymer material selection

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

Literature:

[1] https://phantomplastics.com/highly-filled-plastic-for-reduced-cost/

[2] Introduction to Polymer Compounding  Raw Materials, Volume 1 by Natamai Subramanian 


Wednesday, 6 July 2022

Polymer Material Selection: What are PTFE free alternatives for friction and wear compounds?

Hello and welcome to a new blog post in which we discuss if there are PTFE free alternatives for lubrication.

Why replace PTFE in friction and wear materials?

In the regulation "EU 2019/1021" of the European Union, Perfluorooctanesulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA) are already listed and restricted in use. Further restrictions are under discussion and alternatives to replace materials such as PTFE gain traction. 

PTFE is due to its chemical composition an extremely stable polymer with a low static and dynamic coefficient of friction. Using it in small amounts as additive for friction and wear materials is advantageous. Also, self-lubrication properties are possible. On the other hand, the fluorine is subject to more stringent regulation and the PTFE containing compounds are more aggressive during processing (mould deposits, corrosion and fumes). 

What are PTFE free alternatives for friction and wear compounds?

Ultra-high-molecular-weight Polyethylene UHMW-PE is known for its high abrasion resistance. By using UHMW-PE dispersed in a base polymer similar coefficient of friction values can be achieved. 

There are several methods to estimate the material wear resistance. The sand slurry test (ISO 15527) is a good test to estimate the wear resistance of thermoplastics. In this test, the specimen is rotated 200 - 2400 RPM for 3 hours inside a box which contains the abrasive material (aluminum oxide or silica). The loss of mass is calculated after the test and compared to other material specimens. UHMW-PE has a coefficient of friction of 0.25, which is higher than the coefficient of friction of PTFE (0.1), however the wear resistance is 8 times better than PTFE.

Apart from the sand slurry test, there is the taber abrasion test. The specimen is exposed to an abrasive wheel for 1000 cycles and weight loss of a material is measured. Also in this test, UHMW-PE performs well and outperforms PTFE (Table 1). 

Table 1: Taber abrasion test - results of different polymers and steel

In conclusion, from an polymer material selection point of view, UHMW-PE is an alternative material for applications that need excellent sliding properties as well as excellent wear resistance. Furthermore, flame retardant properties can be achieved by mixing UHMW-PE (wt 80%) with PTFE (wt 20%). 

Thank you for reading and #findoutaboutplastics

Greetings,

Herwig 

Interested to talk with me about your plastic 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.
New to my Find Out About Plastics Blog – check out the start here section

Literature: 

[1] https://www.umco.de/de/blog/artikel/PFAS-Einschraenkungen.html

[2] http://www.sugison.com/div-eng/_shared/files/PE-UHMW%20compare%20to%20PTFE.pdf

[3] https://www.plastix-world.com/ptfe-free-self-lubricating-compound/

[4] https://www.corzan.com/en-us/piping-systems/specification/abrasion-resistance

Wednesday, 29 June 2022

Summary of Testing Standards for Polymer Material Selection

Hello and welcome to a new post.  Looking at a technical data sheet of an engineering polymer, we can find the values and also the standard how this value was estimated. 

It is helpful in the material screening phase during polymer selection for your application to have a feeling which tests can be done and what standards are linked to them. 

In general there are two standardization companies: the American Society for Testing and Materials (ASTM) and  the International Organization for Standardization (ISO). Both are well known organizations in the plastics industry. 

Apart from plastic tests, they also develop all kinds of standards for different industries.

ASTM vs ISO - Are they the same? 

Results of ASTM and ISO are similar and there are one-to-one correlations of some ASTM and ISO standards. 

ASTM and ISO differ in measurement procedures and conditions leading to slightly different results.

Example tensile modulus

The plastic's tensile modulus can be measured according to ASTM D638 or ISO 527-1. Looking at the results, they are similar however not the same. 

There are cases where they are the same, however they are rare cases.

Overview of plastics testing standards: mechanical, thermal, and electrical. 

Figure 1 shows the summary of the mechanical standards, Figure 2 of the thermal standards, and Figure 2 of the electrical standards. 

Figure 1: Overview Standards for Mechanical Tests

Figure 2: Overview Standards for Thermal Tests

Figure 3: Overview Standards for Electrical Tests

There are more standards which can be accessed over the ASTM and ISO homepages. 

Also I made a video where I compare the ASTM/ISO data with real world application requieremnts: 


Thanks for reading and #findoutaboutplastics

Greetings

Herwig 

Interested to talk with me about your plastic 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.
New to my Find Out About Plastics Blog – check out the start here section

Tuesday, 21 June 2022

Ocean Plastics Episode 2 - What The Media, NGOs and Others Still Not Tell You

Ocean Plastics - Episode 2

Hello and welcome back to a new post. Today we continue with Episode 2 of  “Ocean Plastics”. 

Here is the link to Episode1.

Media and NGOs are pushing the topic of ocean plastic contamination in their publications up and down in turn for attention and more funding. It was already proven by Mr. DeArmitt and others that the science was ignored in most cases and even pictures of turtles were photo shopped to make it even more dramatic.

Due to the low density of plastics (0.9 -1 g/ccm) they are floating on and right beneath the water surface which allows them to be relatively easy to bee seen. 

Since plastics represent only 1% of the material and waste, following key question opens up to me: 

What else is in and on the ground of our seas? 

Turns out a lot! Let us examine in detail. 

Oil 

Oil represents a large share of sea pollutants. It was estimated that there are 6,300 wrecks, sunk in World War II, rusting at sea for more than 70 years. Researchers estimate the amount of oil left in them at up to 15 million tons. If the oil storage of the wrecks starts to burst, oil spills will destroy all the plant and animal life of a particular region. Additionally to the 6,300 potentially polluting wrecks around the world, there are 1,583 tank vessels which are a ticking bomb too. Apart from oil, a warship itself contains huge quantities of bronze, brass, copper, and other non-ferrous metals. Interesting is the low-background steel from wrecks sunk before 1945 since this type of steel is not emitting ionizing radiation.

Heavy metals

Metals with a density greater than 3.5 g/ccm can be classed as heavy metals. In this category fall copper, nickel, cadmium, iron, lead, mercury and zinc. Out of the aforementioned metals, lead, mercury and cadmium are the most concerning for sea life. Due to increased industrial activity, heavy metals get into the atmosphere and from there they end up in the oceans. 

Radioactive waste

Mr. Calmet investigated back in 1989 the radioactive waste disposal in oceans and found out that thirteen countries used ocean disposal to get rid of their radioactive waste. 200,000 tons in nuclear waste was approximated which derives mainly from the medical, research and nuclear industry.

Airplanes

Particularly in the WWII area, hundreds of airplanes found their last station on the bottom of the sea. Similar to ship wrecks, they have oil and ammunition which can impact sea life.

Ocean dumping in the United States prior to 1972

The US National Academy of Sciences estimated in 1968 the following annual volumes of ocean dumping by vessel or pipes: 

-100 million tons of petroleum products;

-two to four million tons of acid chemical wastes from pulp mills;

-more than one million tons of heavy metals in industrial wastes; and

-more than 100,000 tons of organic chemical wastes.

Conclusion

The "out of sight, out of mind” attitude for dumping waste into our ocean is wrong. Also, blaming plastics to be the number one littering source for our oceans is wrong too. The data speaks a clear language. There is more and more ideological thinking involved in such anti-plastics topics and too less decision making based on facts. Plastics are part of our solution and are not the problem. 

Thanks for reading and #findoutaboutplastics

Greetings, 

Herwig 

Interested to talk with me about your plastic 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.
New to my Find Out About Plastics Blog – check out the start here section

Literature:

[1] https://www.linkedin.com/pulse/plastic-fact-over-fiction-chris-dearmitt-phd-frsc-fimmm/

[2] https://www.newscientist.com/article/mg20727761-600-why-wartime-wrecks-are-slicking-time-bombs/

[3] https://www.youtube.com/watch?v=XgdE55ZAFvs&t=4s

[4] Michael F. Ashby: Materials and the Environment: Eco-informed Material Choice

[5] https://assembly.coe.int/nw/xml/XRef/Xref-XML2HTML-en.asp?fileid=18077&lang=en

[6] https://www.envirotech-online.com/news/water-wastewater/9/breaking-news/why-is-there-heavy-metal-in-our-oceans/32291

[7]https://www.todayifoundout.com/index.php/2020/12/the-bizarre-market-for-old-battleship-steel/

[8] https://inis.iaea.org/search/searchsinglerecord.aspx?recordsFor=SingleRecord&RN=21044010

[9] https://www.epa.gov/ocean-dumping/learn-about-ocean-dumping#Before

[10] https://www.findoutaboutplastics.com/2018/08/what-media-does-not-tell-you-about.html

[11] https://plasticsparadox.com/