Coating Nylon 3D Prints to Decrease Moisture Absorption Could Open Up New Applications

Share this Article

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.

Specimens coated with Exc and Rub: a) compression samples; b) tensile samples

“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.

Failure of two tensile specimens coated with Rub product: a), b) with a raster angle of 90º; c), d) with a raster angle of 45º

“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.

 

Share this Article


Recent News

Georgia Middle Schoolers 3D Print Parts for the Space Station

3DPOD Episode 47: Metal Powders Deep Dive with Carpenter Additive’s Ben Ferrar



Categories

3D Design

3D Printed Art

3D Printed Food

3D Printed Guns


You May Also Like

3DPOD Episode 46: Engineering CAD with nTopology CEO Brad Rothenberg

Max and I had a really great time talking to nTopology CEO Brad Rothenberg. Brad started nTopology as a series of tools for creating lattices, but it became much more...

3DPOD Episode 45: Sarah Goehrke, Additive Integrity, and Women in 3D Printing

Today, we’ve got the whirlwind that is Sarah Goehrke on the 3DPOD. Max and I had a great time talking to the former 3DPrint.com Editor-in-Chief about her editorial business, Additive...

3DPOD Episode 44: Jennifer Coyne of Wabtec & John Barnes

Today, we talk once again with John Barnes, but we also have Jennifer Coyne of the Wabtec Corporation joining the program. Wabtec is a huge Pittsburg-based train company that makes...

3DPOD Episode 43: Powder Bed Fusion Innovations with Aerosint’s Edouard Moens de Hase

Edouard Moens de Hase talks to us today about Aerosint. For the last few years, they have been working on improving powder bed fusion. The company has an innovative drum...


Shop

View our broad assortment of in house and third party products.