Monday, 11 October 2021

Bio-Based Polyamides – Part 2: Short and Long Chain Aliphatic Polyamides (PA 6, PA 11, PA 6.10, PA 10.10)

Hello and welcome back to our bio-based polyamide blog series. In part 1 we discussed the bio-based PA 5.6 and today in part 2 we discuss bio-based homopolyamides (short and long chain) as well as long chain copolyamides (polyalkylene sebacamides).

Homopolyamides from Biomass Derived Monomers

There are two commercially feasible ways in making biomass based Polyamide 6 (Figure 1): the first route is over sugar and the second route uses starch as a starting point. In the second route an additional processing step is needed (hydrolysis of starch to obtain Glucose). For obtaining a long chain homopolyamide (PA 11), five processing steps are involved and 93% more biomass is needed to obtain 1 metric ton of Polyamide. AS a starting point for Bio-PA 11, caster beans are used.

Figure 1: Routes for making Bio-PA6 and Bio-PA 11

Copolyamides from Biomass Derived Monomers

For obtaining a long chain biomass based copolyamide we need a diamine which reacts with a diacid and either both (fully bio-based) or just one (partially bio-based) is derived from biomass. In Figure 2, the reaction routes of Bio-PA 6.10 and Bio-PA 10.10 are shown.

Figure 2: Routes for making Bio-PA 6.10 and Bio-PA 10.10

Selected properties of bio-based polyamides

In Table 1, typical properties of petroleum-based and bio-based polyamides are shown. The functional amide group which facilitates an internal hydrogen bond between the polymer chains, leads to properties such as hardness, good impact strength and excellent abrasion resistance. Comparing short chain to long chain aliphatic polyamides, the short chain outperforms the long chain in terms of thermal and mechanical properties. However, the long chain aliphatic polyamides have a higher chemical resistance as well as hydrolysis resistance together with low water uptake. Bio-based Polyamides cover the short chain and long chain spectra and depending on the application case, they can outperform or underperform petrol-based Polyamides. The properties shown in Table 1 are the base polymer properties and in most cases the base polymer will be modified with glass fibers and additives. This in turn will make direct comparisons more difficult and more data must be considered in the polymer material selectionprocess (long term data, cyclic data, and chemical data).  

Table 1: Selected properties of petrol- and bio-based Polyamides

Processing and Applications

Injection moulding polyamides represents around 76% of the total polyamide consumption and the automotive and truck market is here in the lead in terms of annual consumption. Other important markets are consumer articles, electrical and electronic parts and appliances parts. Extrusion represents 23% of the total polyamide consumption and covers applications in the field of wire and cable, tubing and piping, and non textile filaments. The remaining 1 % represents powder coating applications.

Bio-based Polyamides start to capture applications in the automotive field, especially for Electric Vehicles. However, due to the current price level and capacities, Automotive will not be the dominating applications field. Long chain bio-based Polyamides offer different properties compared to the more price sensitive short chain Polyamides. Blending and co-polycondensation with petrol based Polyamides will allow to reach the ideal price-to-performance ratio faster. Ongoing regulations to reach certain CO2 levels and Global Warming Potentials (GWP) allows bio-based Polyamides to faster capture applications in different industry sectors. Also, customer demand for such solutions is increasing as well as the regulations.

Thank you for reading and #findoutaboutplastics


Herwig Juster

#materialselection #polymerengineering #biobased #biopolyamides

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[4] Bio-Based Plastics Materials and Applications, S. Kabasci;

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