Sunday 31 January 2021

HDPE Plastic Bag Degradation - The Experiment

The increased amount of plastic bags in our environment lead to discussions about whether or not plastic bags degrade in the short or long term (for example, the 450 year plastic bottle degradation live stream) and how much they harm our environment.  Therefore, in the beginning of this year I started a plastic bag degradation experiment, using a piece of simple high density polyethylene (HDPE) bag and sea water.

The motivation – find out when bag degradation starts

For that I took a standard HDPE plastic bag and cut a 240x160x0.1 mm part out. Then I filled an empty marmalade glass with sea water right from the beaches of Sesimbra, Portugal (California Beach; close to our holiday rental). Then the glass filled with sea water and the HDPE bag was placed in a storage room without the influence of sunlight.

Every year around January, I will check the degradation progress. Let us see how the bag looks in one year and in 30 years.
HDPE Plastic Bag Degradation - The Experiment (up: the HDPE bag sample; down left: identification stamp on the bag; down right: glass with bag sample and sea water; start: January 2021; findoutaboutplastics.com).

It is a simple experiment and there are several scientific studies dealing with this topic. One of them is from Mr. Telmo Ojeda [1] who investigated the degradability of linear polyolefins under natural weathering conditions. Four different polymers were used for the study: high density polyethylene (HDPE), linear low density polyethylene (LLDPE), isotactic polypropylene (PP), oxo-biodegradable HDPE/LLDPE blend (containing a pro-oxidant additive to accelerate degradation).

They found out that it took less than a year for polyolefin films, which have low or no content of antioxidants to degrade by natural weathering. Mechanical properties got lost due to the decrease in molar mass caused by oxidative degradation. There are differences in terms of degradation speed of the investigated polymers. HDPE and LLDPE films showed a more slow degradation, however this degradation was significantly in a timeframe of few months. Rapid degradation could be found with PP and oxo-bio HDPE/LLDPE blend. Since pro-oxidant additives are present in the oxo-bio HDPE/LLDPE blend, acceleration of degradation was accepted and could be proven.  The PP film contained primary (sterically hindered phenols) and secondary (phosphite) antioxidant additives, which slow down the degradation process. However, the antioxidant additives, applied in low concentration, could not prevent the rapid photo-oxidative degradation.  Secondary antioxidant additives showed little influence to delay the abiotic degradation (photodegradation and hydrolysis) in HDPE and LLDPE.

The second study I selected was conducted by Napper and Thompson [2]. The researchers investigated the degradation of biodegradable, oxo-biodegradable, compostable, and HDPE bags over 3 years.

All the materials were exposed to three different environments: open-air, buried in soil, and immersed in sea water. The sea water has a tremendous impact on the compostable bag, which disappeared within three months. The same bag material was still present after 27 month of exposure in soil. However the mechanical strength was so much reduced that it could not hold weight without cracking. Interesting result was that all bag materials decompose into fragments after nine month exposure to open-air.

Governments in different European countries react and made already laws to ban plastic bags. In Austria, for example, plastic bags for shopping are forbidden since 2020. In Austria, the plastic bag consumption sums up to 7000 to 8000 tons per year which represents around 1% of overall waste. Looking at the per head consumption of plastic bags per year, it has a CO2 equivalent of a 15 km passenger car ride [3].

Fact is that plastic bags should not end up in our oceans nor in our environment in general. We have a littering problem and not plastic problem. I hope this conception is changing over the years ahead of us, since plastics are among the most environmentally friendly materials out there [4,5].

I will update you in 2022 on the degradation progress of the HDPE plastic bag immersed in sea water.

Thanks for reading and #FindOutAboutPlastics! 

Greetings,

Herwig Juster

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
Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Literature

[1] Ojeda et.al., Degradability of linear polyolefins under natural weathering, 2011

[2] I. E. Napper & R. C. Thompson, Environmental Deterioration of Biodegradable, Oxo-biodegradable, Compostable, and Conventional Plastic Carrier Bags in the Sea, Soil, and Open-Air Over a 3-Year Period,(2019)

[3] https://www.nachrichten.at/oberoesterreich/ein-sackerl-statt-einem-debatterl;art4,3159915

[4] https://fortune.com/2019/09/04/dow-ceo-plastic-waste/

[5] Chris DeArmitt - The Plastics Paradox: https://plasticsparadox.com/


Sunday 24 January 2021

Design Properties for Engineers: Fuel and Oil Resistance of High Performance Polymers

 In this blog post, we discuss the influence of fuels and oils on different high performance polymers.

Generally, plastics show a good resistance towards fuels (Diesel and Gasoline), oils and greases. Especially, applications used in air- and spacecraft need to be resistant towards aggressive lubricants such as turbine oil and hydraulic oil.

Among the high performance polymers, PEEK, PAI, and PI are often used for applications in air- and spacecraft. If polymers such as PEEK, PAI and PI are exposed to hydraulic oil (for example Skydrol) for a long time (1000 hours), then no significant reduction of mechanical properties could be seen [1].  Tensile strength properties were reduced below 5% in comparison to their initial value. PAI and PI keep their properties nearly on the initial level (tested at a temperature of 120°C). PEEK, PAI, and PI are also resistant towards turbine oils.

Below an overview of the resistance of different high performance polymers towards fuels, oils and greases is shown.

Fuel and Oil Resistance of High Performance Polymers

Checking your application for the need of  fuel, oil and greases resistance already during material selection will decrease chances of plastics part failure at a later stage. 

Thanks for reading and #findoutaboutplastics,

Herwig

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
Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Literature

[1] https://www.polytron-gmbh.de/unternehmen.aspx




Sunday 17 January 2021

Design Properties for Engineers: Adhesion of High Performance Polymers

 In this blog post, we discuss the adhesion capability of different high performance polymers.

In general, adhesion bonding has several advantages compared to mechanical (screw based) connection methods:

- Glue joints allow a more uniform force distribution over the entire adhesive surface (especially under mechanical stress).

- Reduction of stress peaks

- Reduction of material damage due to drilling holes

- Weight reduction

- Excellent sealing properties

- Combination of different materials

There are several industrial adhesives available on the market. Selection of the optimal adhesive is not only dependent on the polymer compound, but also on the use conditions of the final part. The adhesive can enable a flexible or stiff bonding between the plastics. Also, there are adhesives which are temperature and chemical resistant. Furthermore, they can be electrical isolating or electrical conductive.

High performance polymers are not easy to bond since they have a high chemical resistance towards solutions. The chemical resistance of high performance polymers we discussed here. However, even for extreme chemical resistance polymers such as PTFE and PVDF, adhesives are available.

Adhesion of High Performance Polymers

Thanks for reading and #findoutaboutplastics,

Herwig

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
Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Sunday 10 January 2021

Rule of Thumb for Polymer Engineering: The Polymer Product Pentagram

 


In this rule of thumb post, we discuss the Polymer Product Pentagram used as an overarching framework for injection moulded plastic products.

There are five factors, summarized as the Polymer Product Pentagram, which influence the outcome in having best in class injection moulded parts [1]:

1. Part design: polymer parts have an anisotropic behavior compared to isotropic metal parts. This needs to be considered in the part design, especially for injection moulded parts and specific design support during this phase.

2. Material selection: it is important to collect all the application requirements and key performance indicators. Furthermore, once the base design of the part is done, material selection can start. Among the first steps is the translation of the application requirements into material properties. There are frameworks which can support you with the systematic polymer materialselection.

3. Mould design and construction: in this phase, mould design takes place. The mould must be able to withstand the moulding process (injection pressures) and can handle the selected polymer. This is in particular important when moulding of high performance polymers, such as PPS which need a minimum of 135°C tool temperature, is done.

4. Moulding machine selection: after completing the mould design, selecting the injection moulding machine should be done. This step can be done in parallel to the mould design too (depending on the data available).

5. Moulding process: after we have obtained the first parts which passed the quality check, optimization of the process can start. It is the last step and often neglected, however, it allows making the whole production more efficient and economically robust.

Thanks for reading and #findoutaboutplastics

Greetings,

Herwig

If you liked this post, please share and like!


Check out my other rule of thumb posts: 






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
Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Literature:

[1] Distinctive Plastics Inc.:  The 5 critical factors to produce a successful injection moulded product, 2011,


Thursday 7 January 2021

European Plastics Demand by Resin Types (2009-2019) [Racing Bar Chart]

Racing bar chart about the European plastics demand by resin types (in %; 2009-2019):


Thanks for watching and #findoutaboutplastics

Greetings

Herwig 

Date source: PlasticsEurope Market Research Group

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
Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Sunday 3 January 2021

30 Publicly Traded Materials Stocks - 2020 Performance and Outlook

The eventful year 2020 is over and it is time to look how 30 publicly listed material companies have performed.

The “Corona-Crash” hit bottom in March 2020 (around 16-18th) and with it the S&P 500 Index dropped around 34%. Central banks in the USA and EU reacted fast and flushed the markets with money to stabilize the situation – with success!

The S&P 500 Index recovered in a V-shape in a month and most stocks rose again. Travel, leisure and oil kept a much slower recovery, since those sectors are still heavily impacted by the Corona Pandemic.

Overall materials performance

The Vanguard Materials ETF, which tracks the performance of a benchmark index that measures the investment return of stocks in the materials sector, closes with a 20% return in 2020.

30 material stock companies in detail


18 out of the 30 stocks could make gains for their shareholders (date of estimation: 02.01.2021).

This year, we will see a growth in resin demand. However material companies still feel the recession in the US and European markets. The plastics industry played a key part in battling the Covid-19 crises by supplying resins for various healthcare applications. This calmed the rage against plastics.

In the long-term, the plastics industry counts with a yearly polyolefin market growth of 3 to 4% per year, since the world population is growing and access to clean water over the piping systems is in high demand, as well as medical care products and electronics.

Thanks for reading and #findoutaboutplastics

Herwig

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
Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course