Arkema
Laser Sintering (LS) is the most developed Additive Manufacturing technology for the production of industrial parts thus far. It is best suited to carry the industry beyond prototyping due to the mechanical properties attainable by sintering.
Origin and characteristics of Polyamide 11
Polyamide 11, also known as Nylon 11, was launched as a commercial product in 1947 as an alternative to the Polyamide 6.6 developed for textile applications.
Polyamides are semi-crystalline polymers obtained by a polycondensation process from monomers; for example amino-11-undecanoic acid for Polyamide 11, and lauryllactam for Polyamide 12. The major difference resides in the number of carbon atoms in the polymer chain (11 carbons for Polyamide 11), which leads to highly different crystalline structure and hydrogen bonding resulting in superior mechanical properties to Polyamide 12.
Polyamide 11 is derived from castor oil while Polyamide 12 is derived from fossil oil. According to ISO 14040, the Eco Profile of Polyamide 11 shows a -41% CO2 emission and a –44% fossil energy use compared to Polyamide 12 (1).
Polyamide 11 and Laser Sintering
Having been used since the 1990’s, Polyamide 11 was qualified for flying LS parts in aerospace in the 2000’s. With the development of new powders specially designed for this demanding technology, Polyamide 11 is now broadly used either neat or filled (carbon fibers, glass beads or fibers, fire-retardant) in industries such as aeronautics and racing (2), automotive, sport, and medical.
Processing Polyamide 11 has been dramatically improved (3) over the last 5 years with the development of optimized LS grades. The processing window for neat Polyamide 11 is larger than that of neat Polyamide 12 resulting in greater choice of processing parameters to obtain reproducible mechanical properties (4).
Benefits of Polyamide 11 in Laser Sintering
All LS test specimens described herein have been manufactured using an EOS Formiga P100 machine, and the parts have been conditioned 2 weeks @ 23°C under 50% Relative Humidity.
Elongation at break
Thanks to its more ductile crystalline structure (5), Polyamide 11 exhibits superior tensile properties such as elongation at break, especially in the Z direction (usually the weakest direction of AM technologies). (See figure 1)
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Impact resistance
Low temperature has a very negative effect on the resistance to impact of Polyamide 6 or Polyamide 6.6, however this has no influence on the excellent resistance of Polyamide 11 (See figure 2).
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Fatigue testing
Regarding fatigue, the superiority of Polyamide 11 is particularly evident in the Z direction, with a +60% performance at high number of cycles vs. Polyamide 12 (See figure 3).
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figure 3
Elastic memory
One of the key characteristics of Polyamide 11 is the excellent elastic memory due to the higher ductility before irreversible plastic deformation: figure 4 shows that when submitted to a 20% distortion, the part made from Polyamide 11 can fully recover its initial dimension, whereas the part in Polyamide 12 keeps a minimum 5.6% distortion.
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figure 4
Aesthetical and functional parts made from 100% from renewable origin
Parts manufactured in LS using Polyamide 11 have a very distinguished look and can be either natural or deep black for excellent finish with little required post-treatment.
On top of this, Polyamide 11 is the only LS material that is manufactured industrially from castor plants, a non-GMO, non-edible crop growing on poor soil in semi-arid areas and using very few pesticides. As a result, the manufactured LS parts are using 100% renewable carbon resources.
Summary
The use of Polyamide 11 in Laser Sintering is the best existing, commercial answer to deliver functional parts that exhibit excellent mechanical properties (elongation at break, impact resistance, fatigue behavior, elastic memory), while being the only current solution to delivering parts made from 100% renewable origin.
It is particularly exciting that Polyamide 11 is exhibiting fairly isotropic mechanical properties, as opposed to most of the materials used in Additive Manufacturing technologies. The excellent performance of the parts made with Polyamide 11, in all directions, and especially in the Z direction, is the current solution to the manufacturing challenges of the Industry 4.0.
Sources
(1) Arkema internal data
(2) TCT Show UK 2015, Brett Lyons, Patrick Warner, Rick Booth, Developing Materials for Aerospace and Motorsports
(3) SFF 2012, Ben Fulcher, David K. Leigh (Harvest Technologies), Effect of Segregated First and Second Melt Point on Laser Sintered Part Quality and Processing
(4) iCAT 2014, Andreas Wegner (University of Duisburg-Essen, Germany), Influence of Process Parameters on the Part Properties of Laser Sintered Polyamide 11
(5) 2008, Patrick Dang, Sylvie Tence-Girault, Polyamide 11 and Polyamide 12 : So close but So different, Why PA11 is the best!
