A Guide to SLS Nylon Materials!

It is no secret the forefront role Nylon has in 3D printing and its fast development of newer innovations regarding blends and formulations in the latest years, especially in SLS printing. Formlabs just recently released their new Nylon 12 Glass Filled material for the Fuse 1 SLS system. With so many Nylon types, it’s likely for users to lose track of what material to choose for any specific application. This article will dig deeper into the wide world of Nylon materials in engineering and what the Formlabs SLS products’ swift development means for the industry.

What’s So Great About Nylon?

Polyamides or PAs, better known for their commercial name, Nylons, is the industry standard for engineering-grade thermoplastics, given their outstanding mechanical, thermal, and chemical resistance properties. Rather than being a single material, we’re talking about a whole material category when discussing polyamides.

However, some notable things we can say they all have in common is their low friction coefficient, high melting temperatures, thus high abrasion resistance, not to mention their excellent durability when submitted to fatigue. For instance, you’ll see that Nylon is ideal for moving and flexible parts; It is often used for interlocking gears, screws, nuts, bolts, wheels, rollers and living hinges.

Other advantages of Nylon include high weight-to-strength ratios, toughness, a good base for composite fills, electrical insulation, non-sensitising and biocompatible properties.

One Major Drawback for Nylon  

Nylon is also craved for its high environmental stability. These materials usually perform under exposure to alcohols, hydrocarbons, lubricant oils and cleaning agents, just to name a few. However, polyamides have one major drawback: hygroscopicity. These materials tend to absorb a considerable amount of moisture, which can dramatically affect the expected outcome when it comes to mechanical performance, dimensional accuracy and manufacturability.

This property is detrimental in delivering predictable performance. So, it’s crucial to manage storing and drying processes adequately. Nonetheless, this disadvantage can become an advantage in some cases since it enables Nylons to be dye friendly.

From Traditional Manufacturing to 3D Printing

PA certainly is the most used engineering thermoplastic, which can be attributed to its long history and revolutionary breakthrough in manufacturing and numerous industries. Nylon 66 began its commercialisation by DuPont in 1935 as the first synthetic thermoplastic in the industry. We can now see it in all kinds of consumer goods, such as toothbrushes, guitar strings, cable ties, and numerous textiles from sportswear to fishing lines to some of the toughest ropes in the market.

Its versatility enables compatibility with multiple traditional fabrication processes and additive manufacturing processes such as FDM, MJF and SLS. Though every technology has its pros and cons, SLS is the most suited when considering precision and printability. However, SLS printing processes tend to be very expensive if we consider that most SLS printers currently in the market involve industrial-grade equipment.

Thankfully, benchtop SLS solutions are becoming obtainable for SMEs’ budgets. Last year, Formlabs made its debut in SLS printing with the acclaimed Fuse 1 system with that clear necessity in mind. Up to date, the fruits of its success are evident. Just in one year, Formlabs managed to grow its powder catalogue from just one product to the current three: Nylon 12, Nylon 11 and the new Nylon 12 GF. Taking from this fast evolution, we’re sure we’ll be seeing much more from Formlabs SLS in the near future.

Nylon Types

Again, unlike other thermoplastics, referring to polyamide or Nylon is, in fact, vague. Rather than a single material, Nylon is a category with a wide variety of materials with unique properties and polymerisation methods. We’ll have a look at key types within SLS printing like Nylon 12, Nylon 11 and Nylon 6/66. And, what do the numbers mean? That’s just the number of carbon atoms within their polymer structures.

Nylon 12: Versatile

Nylon 12, also known as PA 12, polylaurolactam or Daiamid (Evonik’s trade name), is the standard material for SLS printing. Aside from its excellent mechanical properties and chemical resistance, this material is the most friendly to work with among other polyamides given its lower hygroscopy, low melting point and high dimensional stability. As a result, printed Nylon 12 parts can offer exceptional surface resolution and feature details.

This material is especially stiff and stable even under temperatures below freezing. Moreover, Nylon 12 is excellent for processes that involve biocompatibility and sterilisation, allowing users to 3D print objects for medical applications such as prostheses.

Nylon 12 parts have uses in both prototyping and end-use with high environmental stability when it comes to applications. Other uses for Nylon 12 are:

• Permanent jigs, fixtures, and tooling
• Housings and enclosures
• Insulation for electronic components
• Impellers, connectors, complex ductwork and snap-fit designs    

Nylon 11: Impact Resistant

Nylon 11, also known as PA 11 or Rilsan (Arkema’s trade name), is one of the rare bio-based thermoplastics available. Contrary to the usual fossil sources, this material is produced from castor beans, ultimately leaving a lower environmental impact. However, the most notorious feature for this type is its superior elasticity, ductility and impact resistance. Compared to Nylon 12, Nylon 11 is more flexible, less brittle, and better at printing thin walls and lattice structures.

PA11 is best suited for applications where repetitive and dynamic loads exist, such as living hinges and crash-relevant automotive parts. Other uses are:

• Impact-resistant prototypes, jigs, and fixtures
• Thin-walled ducts and enclosures
• Snap-fit designs
• Orthotics and prosthetics

Nylon 6 and 66: Industry Standards

Nylon 6 is known by many names, such as PA6, Polycaprolactam and Ultramid (BASF trade name). Along with Nylon 66, this material is probably the most used engineering thermoplastic. Most traditionally manufactured Nylon consumer goods are made from one of these materials. Both of these materials have similar properties since Nylon 6 was initially developed to reproduce the properties of Nylon 66 without violating the patent on its production.

They excel at chemical resistance to substances such as acid and alkaloids. However, one major drawback is their particular tendency to absorb water, reaching up to 2.5%. As a consequence, these polyamides will decrease in strength and tensile modulus. From another perspective, moisture can be favourable to improve plastic properties like flexibility, impact absorption and toughness throughout controlled conditioning processes.

Although not as common as Nylon 12 and 11 in SLS manufacturing, PA6 and PA66 powders do exist. If we take Nylon 12 as a comparison, Nylon 6 tends to be stronger but less high temp, less resistant to UV and harder to process.

GF Nylon: Extra Stiff, Extra Heat-Resistant

Nylons can be easily blended to form composites, enhancing their performance parameters. This is common in the automotive industry. Undoubtedly, the most popular in 3D printing are glass-filled and carbon-filled Nylon; we’ll focus on the first one.

In SLS printing, Nylon 12 is the go-to choice for composites. Nylon 12 GF combines the utility of Nylon 12 with the rigidity and heat resistance of glass, making the resulting material an ideal option for any application requiring sustained load-bearing ability, elevated thermal resistance and better dimensional stability than pure Nylon. Compared to CF Nylon, GF Nylon tends to be less brittle and have better insulation properties. However, CF Nylons are usable at higher temps.

To Illustrate, some applications of Nylon 12 GF are:

• Parts under load in high-temperature environments like vents, valves and carburettors                     
• Stiff, load-bearing jigs and fixtures, such as brackets
• Stiff and stable medical devices
• Threads and sockets

Other Blends

Aside from glass and carbon-filled blends, there’re other options in the market, such as alumide (an aluminium filled polyamide), which offers improved stiffness, wear resistance and ESD properties, and mineral-filled PA which also improves stiffness and thermal properties.

Additionally, Nylon is also versatile with additives that can enhance ESD (Further improvement of electrical insulation properties) and flame retardancy (Since Nylon is not inherently flame retardant)

To end this article, it is also worth mentioning the potential that the SLS process has with other materials besides Nylons, such as PAEKs, PP, TPE and more. Possibilities are not only endless but are becoming more accessible as this technology develops.

For further information on Formlabs SLS opportunities, Solid Print is here to help you. Please feel free to call Solid Print at 01926 333 777 or email info@solidprint3d.co.uk.