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

My YouTube channel

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

My YouTube channel

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/

Flame Retardants - Why Do We Need Them and What Are The Major Systems?

Hello and welcome to a new blog post. Today with the topic of flame retardants, starting with an overview and then discussing as an example effective flame retardants for Polyamides. 

Why do we need flame retardants in plastics?

In general, adding flame retardants to your polymer compound formulation helps to prevent the immediate start of fire or slowing the growth of fire of your material. This in turn helps to fulfill a certain burning classification such as the UL V0 at a certain material thickness. The material requirement list of your application should consider flame rating needs since it will be easier later during polymer material selection to not miss such an important detail. 

Do all polymers need them?

Aliphatic polymers need them to achieve a desired level of UL V0. Semi-aromatic polymers such as PPS do not need them since the benzene rings enable an intrinsic flame retardancy. As a rule of thumb the higher the aromatic amount (benzene) the better the flame retardancy level of your polymer compound. 

Overview of the 3 major systems

There are three major systems used in the plastics industry: nitrogen-phosphorus systems, halogenated systems, and metal-hydroxide systems.

Nitrogen-phosphorus systems are halogen free and show a lower smoke emission compared to halogenated flame retardants. Furthermore they do not decrease the mechanical properties of your base polymer too much. Usually, adding the flame retardants results in a lowering of properties. Downside of this system is the narrow production window, water solubility and poss surface aesthetics. 

Halogenated systems are very good flame retardants and can be used at low concentration levels, together with a wide production window. Major disadvantage is the use of halogens (pay attention to local regulations) and during combustion it develops a lot of smoke emissions, together with the release of free radicals. Also, stabilization against weathering is not possible. 

Metal-hydroxide systems are halogen free and stabilization towards weathering is possible. During combustion, this system only releases water. Downside is the high concentration of flame retardant needed, and lower mechanical properties as a result. 

Figure 1 summarizes the advantages and disadvantages of the different flame retardant systems. 

Figure 1: Comparison of the advantages and disadvantages of the different flame retardant systems

Example: Use of flame retardants in Polyamide PA 6

Alumina Trihydrate (ATH) is a widely used flame retardant and can be a starting point for Polyamide 6. The decomposition temperature of ATH is around 180°C and it releases water.  However, the compounding and processing temperature of PA 6 is between 230°C and 290°C which leads to an activation of the decomposition of ATH. Therefore we need an alternative to safely bring PA 6 onto a certain flame rating. The solution is in Magnesium Hydroxide (MDH) which has a decomposition temperature of 330°C. Apart of MDH, boron zinc oxide and organophosphorus salt can be used for high performance Polyamides such as PPA and PARA. 

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

My YouTube channel

Literature: 

[1] https://www.hubermaterials.com/products/flame-retardants-smoke-suppressants/flame-retardant-smoke-suppressant-applications.aspx

[2] https://www.findoutaboutplastics.com/2019/03/plastics-part-design-continuous-use.html

Plastic Part Design Properties for Engineers - HDT @ 1.82 MPa Filled and Unfilled Thermoplastics

Hello and welcome to a new blog post. Today we have a look at the HDT (1.82 MPa) of filled and unfilled amorphous and semi-crystalline polymers. 

In a previous post we discussed the HDT values of high performance polymers such as PPS and PEEK. In general the Heat Deflection Temperature or Heat Distortion Temperature (HDT) describes the temperature at which a polymer test bar bends 0.25 mm under a given load and is estimated by the ASTM D 648 or ISO 75. Apart from the DMA, HDT can be used to predict the maximum service temperature of parts under mechanical loads. For this the HDT at 1.8 MPa is used. It can be measured at 0.46 MPa and 8 MPa too. 

HDT @ 1.82 MPa of filled and unfilled thermoplastics

Figure 1 shows the HDT values at 1.8 MPa loading for unfilled and filled (30% glass fiber) amorphous and semi-crystalline polymers. 

HDT @ 1.82 MPa of filled and unfilled thermoplastics

Are there differences in the HDT between amorphous and semi-crystalline polymers when they are filled with glass fibers?

Yes, there are differences. Amorphous polymers such as Polystyrene, ABS, Polycarbonate, and Polysulfones show a minimal effect in change of HDT with glass fiber incorporation. However, semicrystalline polymers show large effects and the HDT value can be increased. For unfilled semicrystalline polymers, the HDT is close to the glass transition temperature and the filled version have a HDT close to the melting temperature. 

How does the HDT with other fillers such as mineral?

Figure 2 compares the HDT of glass and of mineral filled PA 6.6 and PEI. Mineral filler increases the HDT of semi-crystalline polymers, however not as much as glass fibers. Amorphous polymers show again a lower impact in terms of HDT increase. 

Figure 2: Comparison of PA 6.6 and PEI filled with glass and mineral

This needs to be kept in mind during your part design phase and polymer material selection, especially for technical parts and temperature load, glass fiber reinforced materials can make the difference. 

Check also out my UL RTI vs. HDT post here. 

Thanks for reading!

Greetings and #findoutaboutplastics

Herwig 

Literature:

[1]  McKeen - the effect of temperature and other factors on plastics and elastomers

[2] https://www.findoutaboutplastics.com/2021/09/design-properties-for-engineers-ul-rti.html