Friday 30 November 2018

Reviewing Key Engineering Plastics - Acrylonitrile Butadiene Styrene (ABS) [incl. Video]

Hello and welcome to this blog post where I will review one of the most famous and versatile plastic ever: Acrylonitrile Butadiene Styrene, or in short ABS. We will review the chemistry, look at the simplified petrochemical flow chart, and discuss the properties of ABS as well as its global demand and producers. I will provide you some price indications and talk about the end uses of ABS too.

1. Chemistry
ABS is an amorphous polymer with a glass transition temperature of 105°C. It is made out of 3 different monomers: Acrylonitrile which provides heat resistance and chemical resistance to strong acids and bases; Butadiene which brings the good impact resistance as well as inferior low temperature resistance; and Styrene which allows ABS to be easily processed and gives it some rigidity.
Where do the three different monomers have their roots?
In general, one can state that 95% of the organic chemical industry is based on seven raw materials (Ethylene, Propylene, C4-Oefins such as Butens and Butadiens, Benzene, Toluene and Xylenes). Those seven starters can be obtained by steam cracking of Naphtha. Therefore, Butadiene is obtained straight after steam cracking the naphtha into its core components.
Acrylonitrile is already more complex. Again you crack Naphtha and get Propylene. In a next step, catalytic ammoxidation of propylene leads to Acrylonitirle. This is also known as the SOHIO process.
Styrene has its foundation in ethylbenzene which is produced by the catalytic alkylation of benzene with ethylene. Then dehydrogenation of ethylbenzene is carried out to obtain styrene. Polymerization of Acrylonitrile with Styrene in the presence of Butadiene particles is done over a continuous mass process.

2. Properties
ABS is a versatile material with a number of good properties. It can be seen as an engineering plastic. However, ABS has limitations at higher temperatures where its physical properties show a sharp decline. As I mentioned in the beginning, the glass transition temperature is around 105°C and the selected application should have a continuous use temperature (CUT) not higher than 90°C. Altogether, we can summarize the properties as follows: ABS has a good stiffness combined with excellent toughness due to the Butadiene content. It shows good electrical properties and has a high gloss. The chemical resistance is good and it is platable. Furthermore, easy coloring is possible: ABS is available in 100’s of colors.

3. Capacity and Manufacturers
The global demand of ABS in 2016 was around 7.9 Million Tons. Asia Pacific is with 74% the highest end user. When we look at the ABS producers, we can say that the top 10 manufacturers provide 71 % of the global capacity. Chi Mei is with 1780 thousand tons per year the largest producer.

4. Price to Performance
A major point in material selection is the cost of plastic. ABS has a moderate cost level and ranges in the lower end of engineering plastics with around 2- 2.5 €/kg.

5. End Uses
ABS has many different end uses, ranging from pipe and fittings, appliance housings, and business machine housings. It is used in automotive parts such as grillers and body parts and due to the high gloss and good appearance it is used in luggage and sports accessories. ABS is known to most of us due to vacuum cleaner housings, LEGO bricks and a bit more unknown but quite interesting is that the car body parts of the Citroen Mehari are made of ABS.

To summarize, this was a review on ABS, a versatile material used in many applications.

Thanks for reading & till next time!
Herwig Juster

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

Literature: Charles P. MacDermott: Selecting Thermoplastics for Engineering Applications