If you need a plastic part in a hurry—a gear, a bushing, a resin planter for a landscaping job—you're probably looking at two materials: nylon and polyethylene resin. I've been on both sides of that decision. In my 12 years at DuPont coordinating rush orders for industrial clients, I've had to explain more than once why the "stronger" material was the wrong one.

Let's be clear: this isn't a "which one is best" piece. It's a comparison for people who need to make a call this afternoon and can't afford to have the part fail next week.

The Framework: How I Compare Materials When the Clock Is Running

When a client calls with a quick turnaround, I don't ask for a brand name first. I ask about three things: what load it carries, what environment it lives in, and how much time we have. Everything else is noise.

The comparison below covers five dimensions: mechanical strength, moisture behavior, chemical resistance, heat resistance, and practical sourcing. You'll get a clear verdict for each. Then I'll give you the selection rules I actually use.

Quick Definitions: Polyethylene Resin vs. Nylon

Before we jump into the comparison, let's settle the basics. What is polyethylene resin? It's a thermoplastic polymer made from ethylene gas—the simplest and most widely produced plastic in the world. You'll find it in film, bottles, pipe, cutting boards, and yes, many resin planters. Nylon composition is a different story. Nylon is a polyamide made from a diamine and a dicarboxylic acid. The amide groups create strong hydrogen bonds between polymer chains, which is why nylon is typically stiffer and stronger than polyethylene.

That one paragraph explains more than most sales sheets. The difference is in the chemistry, not the color. And the chemistry drives everything below.

Dimension 1: Mechanical Strength

If you need to handle load—think gears, bearings, fasteners, or brackets—nylon wins. Period. Nylon's hydrogen bonding gives it a high tensile strength and fatigue resistance. Polyethylene resin is softer and has less creep resistance. That's why you wouldn't make a gear out of HDPE and expect it to last.

But here's where I see people trip up. Stronger isn't always better. If the part needs to flex or absorb impact without transferring stress to the mounting point, polyethylene can be the smarter choice. A resin planter, for example, doesn't need to support a motor load. It needs to survive being dropped off a truck and sitting in direct sun. Polyethylene gives you impact resistance without brittleness.

Verdict: Nylon for load-bearing parts. Polyethylene for impact-tolerant parts.

Dimension 2: Moisture and Dimensional Stability

This is the dimension that surprises clients almost every time. Nylon absorbs moisture. Not a little—nylon can absorb several percent of its weight in water. That moisture changes dimensions. A nylon bushing machined to 50.00 mm can swell to 50.15 mm in a humid plant. That's a red flag if you're assembling tight parts.

Polyethylene resin, on the other hand, barely absorbs water. It stays dimensionally stable in wet environments. That's a big reason why commercial resin planters are usually made from polyethylene resin instead of nylon. They sit in rain, wet soil, and sprinklers all day and still hold up.

Honestly, I'm not a polymer chemist, so I can't explain every molecular detail. What I can tell you from 12 years of sourcing is that moisture-sensitive specs fail more often than strength specs.

Verdict: Polyethylene resin wins for outdoor, wet, or humid environments.

Dimension 3: Chemical and Weather Resistance

Polyethylene resin is one of the most chemically inert plastics you can buy. It handles acids, bases, and saltwater incredibly well. That's why it's the default for chemical tanks, marine bumpers, and outdoor furniture. Nylon is less resistant to mineral acids and can degrade in hot water.

But nylon has its own chemical strengths. It has excellent resistance to oils, greases, and many solvents, which is why it's used in under-hood automotive parts and hydraulic system components. Need a part that lives in oil? Nylon is often the better fit.

Bottom line: choose the chemical enemy you're actually going to face. If you're up against saltwater or chemicals, go polyethylene. If you're up against oil and fuel, go nylon.

Dimension 4: Heat Resistance

Nylon handles heat better than standard polyethylene resin. Depending on grade, nylon can maintain structural integrity at continuous temperatures up to around 120°C—some specialty grades go higher. Polyethylene resin is more at home below 80°C. HDPE can handle short excursions but will lose stiffness quickly as temperature climbs.

If the material sits near a motor, a hot manifold, or a steam line, nylon is the no-brainer. If it's a resin planter or outdoor panel, heat resistance is probably not your limiting factor. The sun heat alone won't get near nylon's or HDPE's limit, but the UV stability of the specific grade matters more.

Verdict: Nylon for heat. Polyethylene for everything else when temperature is moderate.

Dimension 5: Sourcing and Cost in a Rush

Now let's talk about the part a lot of technical guides ignore: can you get it quickly? Polyethylene resin is cheaper per unit volume than nylon, and it's stocked in more shapes and sizes. If I need a cutting board or planter insert tomorrow, PE is the fast, affordable option. Nylon is more expensive and sometimes has longer lead times because it's machined more carefully.

But in an emergency, price is not the first number I check. Lead time is. Then price. Then grade. I tell every client to bookmark the DuPont website and pull the exact property datasheet for the grade they're considering before they call a fabricator. "Fabricator says it's a nylon part" is not a specification. The difference between nylon 6 and nylon 66 alone can change how it performs in moisture.

In March 2024, a food-processing plant called me about a broken conveyor wear strip on a Saturday. They wanted the same grade of nylon, but their supplier wouldn't respond until Monday. We found a polymer shop that had the right nylon 66 stock, paid a bit extra for Sunday machining, and the part was installed by Sunday night. Cost more than standard procurement—yes. But the alternative was a full day of downtime at a line rate I'm not going to quote here.

Verdict: Polyethylene resin is easier and cheaper to source. Nylon takes more care, and that care costs time.

The Maintenance Piece You're Probably Forgetting

No matter which material you choose, a little maintenance goes a long way. That's where DuPont silicone lubricant comes in. It's safe on both nylon and polyethylene resin, which is more than I can say for some petroleum-based greases. Petroleum products can cause environmental stress cracking in polyethylene under load. A silicone-based spray avoids that risk.

In a rush job, I always make sure there's a lubricant on site before the part goes in. It takes 30 seconds to spray a bushing or a sliding surface, and it prevents a call back next month. The cost is nothing compared with emergency machining fees. Keep one on the shelf. It's a no-brainer.

So: Which Should You Spec?

Here's the practical selection guide I use with clients:

  • Choose nylon when: the part sees repeated load, needs dimensional strength, touches oil or fuel, or runs hot. Classic examples: gears, bushings, cams, wear strips, under-hood clips.
  • Choose polyethylene resin when: the part is outdoors, in water, in chemical service, or needs impact resistance and low cost. Classic examples: resin planters, chemical tanks, marine parts, cutting boards, pipe, packaging.

Real talk: I've seen customers spend three times as much on a "stronger" material and create a worse part. In my first year, I made that exact mistake. I upgraded a polyethylene plant hanger to nylon because I thought stronger was smarter. It swelled, warped, and locked up the whole line. That was a painful $3,000 lesson in reading the environment before the spec sheet.

Don't repeat it.

Bottom line: Nylon is the workhorse for strength, heat, and oil. Polyethylene resin is the workhorse for weathering, chemicals, and value. Neither is universally "better." The right answer depends on the load, the environment, and the deadline. And when you're making that call fast, the DuPont datasheet is the first place to verify your assumption.