As 3D printing materials advance, it’s becoming possible to create stronger 3D printed parts. Porosity is an issue that afflicts many 3D printed parts, however, including those produced by FDM. One of FDM’s weaknesses is poor bonding between layers, which results in tiny pores and less strength than is ideal. Other factors can weaken parts, as well, depending on the material. Nylon is generally an excellent 3D printing material, but it tends to absorb humidity, which reduces both strength and stiffness.
In a new paper entitled “Failure Analysis of Additive Manufacturing Nylon Parts Coated with Protective Products,” which you can access here, a group of researchers explored the option of applying a protective coating over 3D printed nylon parts to reduce porosity and moisture absorption. They tested the strength and stiffness of the parts as well as the water absorption after applying the coatings, in hopes of opening up new applications for nylon 3D printed parts.
The researchers 3D printed two samples using a Mark Two 3D printer from Markforged. They then applied two different protective materials to the samples: the polyurethane elastomer 10Excellent (denoted as Exc) and the liquid silicone Rubson SL 3000 (Rub). Both are used in outdoor waterproofing applications. After being treated and dried for 24 hours, the 3D printed samples were placed over a filter paper pile immersed in water. Periodically, the samples were removed from the water and weighed. Compression and tension tests were then performed on the samples to determine yield stress and strain, plateau stress and strain, and ultimate stress and strain.
“Although silicone displays good weather resistance properties to nylon, the Rub product was found to poorly adhere to polyamide,” the researchers state. “The polyurethane Exc product presented much better water absorptions results in comparison with Rub product. It is known that pure nylon having a polar structure attract moisture as it bonds with hydrogen water molecule. However, polyamide in the presence of polyurethane, accomplish hydrogen bonding taking place among the coating molecules, which will reduce water absorption.”
Because of the hydrogen bonding that takes place between polyamide and polyurethane, the researchers continue, it is possible that the polyurethane coating acts as a plasticizer, affecting material properties such as strength and stiffness – decreasing them, in fact. But the decrease in strength and stiffness wasn’t significant, and the reduction of water absorption from the coating made the treatment worth it.
“These results indicate that coating FDM parts with polyurethane based products is a new way to achieve polyamide parts with enhanced water absorption properties, which could contribute to a wide range of applications,” the researchers conclude. “Although a decrease in the strength and stiffness was detected of the nylon samples coated with polyurethane, they still show acceptable mechanical properties for non-load bearing applications, with a major reduction in the water absorption properties.”
Nylon 3D printed parts are being studied for use in medical applications, and are already being used in the automotive industry. Both of these applications could benefit from parts that absorb less moisture than untreated parts.
Authors of the paper include M. Miguel, M. Leite, A.R. Ribeiro, L. Reis, and M.F. Vaz.
Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below.
You May Also Like
In-Q-Tel and 3D Printing, Part 1: What’s In-Q-Tel?
So far, a venture capital company called In-Q-Tel has invested in three startups within the 3D printing and scanning space: Voxel8, Arevo, and Fuel3D. If you don’t recognize the name...
3D Printing News Briefs: January 11, 2020
We’ve got some business news to share with you in today’s 3D Printing News Briefs. For starters, Knust-Godwin has purchased a Sapphire 3D printer from VELO3D. The AMable project has...
Canada: University Researchers 3D Print GlioMesh to Treat Brain Cancer
In the recently published ‘A Drug-Eluting 3D-Printed Mesh (GlioMesh) for Management of Glioblastoma,’ Canadian researchers take on the topic of using 3D printing for better treatment of glioblastoma (GBM) as...
Sintratec Providing 3D Printing Support to Daimler Buses for Service Bases
The commercial vehicles segment of Mercedes-Benz parent company Daimler AG has fully integrated 3D printing into the development process and series production workflow for several of its divisions, such as...
View our broad assortment of in house and third party products.