What Is Cast Nylon? Properties, Uses and Limits

Material Guides

By B. Decker  •  Updated October 2026  •  Laird Plastics Engineering Team  •  9 min read

Cast nylon is nylon 6 (PA 6) made by pouring liquid caprolactam into a mold, where it polymerizes into solid stock. The process produces large rods, tubes, plates, and custom shapes with strong wear resistance. Machine shops use cast nylon for gears, bushings, wear pads, sheaves, and rollers.

Cast nylon shows up in gears, bushings, wear pads, sheaves, and rollers. Buyers still mix it up with extruded nylon. The two share a name and a family, but they form in different ways and usually use different polymers. This guide covers how cast nylon is made, what its properties look like on real datasheets, where it works, and where it does not.

Cast Nylon Facts at a Glance

Every number in this section comes from a published producer, supplier, or regulatory source. Start here, then read the sections below for context.

Typical properties of cast nylon 6

Values are typical at 73°F. They are not specifications. The Professional Plastics sheet lists ASTM D638 for tensile strength, D256 for notched Izod impact, D570 for water absorption, D648 for heat deflection, and D3418 for melting point. The Cast Nylons Limited figures come from its published capabilities brochure.

Why two columns: Producers publish different values for the same material class. Impact strength, service temperature, and melting point all differ in this table. Use it for orientation. Get the datasheet for the exact grade you plan to buy.

How Cast Nylon Is Made

Cast nylon starts as a liquid. Producers pour caprolactam into a mold, where it polymerizes in place by anionic polymerization into solid nylon 6. FDA's nylon resin regulation, 21 CFR 177.1500, defines nylon 6 as the polymer of epsilon-caprolactam.

The chemistry is older than the product. Paul Schlack of IG Farben polymerized caprolactam in 1938, according to the Deutsche Biographie. Cast nylon 6 reached commercial production in the 1960s, as Mitsubishi Chemical Advanced Materials describes it.

Near-net-shape castings

A near-net-shape casting is poured close to its final geometry. The machinist removes less material. Cast Nylons Limited pours sheaves and other parts this way. Laird's nylon cast and extruded category points to cast nylon for near-net custom shapes.

Mitsubishi describes cast nylon as the middle path between machining standard stock and investing in injection molds. That is the main reason machine shops reach for it.

Cast Nylon vs Extruded Nylon

The short version: cast nylon is nylon 6 formed in a mold. Extruded nylon is usually nylon 6/6 pushed through a die.

Nylon 6 and nylon 6/6 are both polyamides

Both are polyamides and both are polymers. The difference is the chemistry. Nylon 6 comes from one monomer, caprolactam. Nylon 6/6 (nylon 66) comes from hexamethylenediamine and adipic acid. Nylon 6/6 melts higher. 21 CFR 177.1500 lists a melting range of 392 to 446°F for nylon 6 resin and 475 to 495°F for nylon 66 resin.

Emco Industrial Plastics says in its nylon FAQ that cast nylon is more ductile and cost-effective in large sections. It also says type 6/6 tends to have slightly higher temperature capability. Treat both as general tendencies. The datasheet for the grade decides.

Rule of thumb: Pick cast nylon when the part is large or the shape is custom. Pick extruded nylon when a standard small-diameter size covers the job.

Cast Nylon Grades and Fillers

Producers modify base cast nylon 6 to change friction, heat resistance, or load behavior. Grade names vary by producer. Confirm the exact grade code on the datasheet.

Availability varies by grade and size. Ask your local Laird location what is in stock.

Where Cast Nylon Is Used

Cast nylon fits parts that slide, roll, or take wear. Mitsubishi lists wear pads, sheaves, outrigger feet, trackplates, rollers, bushings, and gears among its applications.

• Gears and gear rings. Cast gear rings reach 96 inches on Mitsubishi's published range.
• Bushings and wear pads. Machine shops turn and mill them from cast rod, tube, and plate.
• Sheaves and rollers. Producers cast sheaves directly in near-net shape.
• Outrigger feet and trackplates. Both appear on Mitsubishi's application list.
• Food processing and packaging machinery. Gears and wear parts here need food-contact grades.

Machine shops are the main buyers. See which plastics machine shops use and browse Laird's machine shop plastics page. For food plant parts, start with Laird's food and beverage plastics.

Limits of Cast Nylon

Nylon fits many parts and misses on others. Check these limits before you specify it.

• Moisture. Nylon absorbs water. One supplier table lists 0.3% in 24 hours and 7.0% at saturation. Another lists 4.0% to 6.0% at saturation. Absorbed water changes part dimensions, so plan for it on tight-tolerance parts. Compare acetal when dimensional stability matters most.
• Heat. Maximum operating temperature is 200°F on one sheet and 230°F continuous on another. Heat deflection at 264 psi is 200°F for the unfilled grade on the first sheet. Heat-stabilized grades go higher.
• Impact values vary. Notched Izod runs 0.4 ft-lb/in on one sheet and 1.5 to 2.5 ft-lb/in on another. Get the datasheet for your grade. Radius internal corners on parts that take shock.
• Chemicals. Nylon handles fuels and lubricants well. Phenols, strong acids, and oxidizing agents attack it. Check a resistance chart for your exact media and temperature.
• Flammability. Nylon is combustible. One supplier table lists cast nylon 6 at UL 94 HB. Request the rating for your grade when a flame rating matters.

Food-Contact Cast Nylon

Not every cast nylon is food safe. Only grades with compliance documentation qualify. FDA regulates nylon resins for food contact under 21 CFR 177.1500.

Cast Nylons Limited states that named grades (6PA Natural, 6PA FG, and NYLOIL FG) were third-party tested to that regulation. The maker of the finished article must still evaluate its own article. Laird's extruded nylon rod page lists natural grade compliance with FDA, USDA, NSF, and 3A-Dairy requirements. Ask for the compliance letter on the exact grade before you order for a food plant.

How to Specify and Order Cast Nylon

1. Name the material: cast nylon 6 or extruded nylon 6/6.
2. Pick the grade: natural, heat-stabilized, oil-filled, MoS₂, or food-contact.
3. State the form and size. Emco notes that cast tubes are cast with excess outside diameter, inside diameter, and length for machining, so allow for finish cuts.
4. List operating temperature, moisture exposure, load, and chemicals.
5. Ask for the datasheet and any compliance letters for the grade.

Laird lists nylon in its nylon cast and extruded category. Its engineering plastics page says cut-to-size and custom fabrication are available nationwide.

Frequently Asked Questions

Bottom Line

Cast nylon is nylon 6 formed in a mold. It fits large parts, custom shapes, and wear components that machine shops finish to size. Extruded nylon 6/6 fits smaller diameters and tends to run slightly hotter. Check moisture, temperature, and food-contact needs before you choose. Read the datasheet for the exact grade.

This article is for informational purposes only. Material selection, thickness specifications, code compliance, and installation requirements must follow project specifications, manufacturer datasheets, and applicable building codes and standards. Verify current standards, certifications, and material grades with the manufacturer and your design professional before specifying.