Polycarbonate vs Nylon: A Procurement Pro’s View on Hydrolysis Resistance and Long-Term Cost

If you’re choosing between polycarbonate and nylon for your next project—whether it’s a plastic chain, a resin keychain, or a structural component—the single most overlooked factor is hydrolysis resistance. Not tensile strength. Not cost per pound. The ability to survive heat and moisture over time. I’ve seen 5-figure chargebacks because someone assumed nylon would hold up outdoors. It took me about 150 rush orders and one big loss in 2023 to really internalize that.

Why Hydrolysis Resistance Matters More Than You Think

People often think the key difference between polycarbonate and nylon is just strength or price. That’s not quite right. The real split is how they handle wet environments over time. Nylon absorbs moisture—up to 8-10% by weight in some grades. That changes its dimensions, reduces its stiffness, and can cause part failure if the design doesn’t account for it. Polycarbonate, especially hydrolytically stabilized grades like Covestro’s Makrolon, resists that absorption. It stays dimensionally stable in humid or wet conditions.

I had a client in March 2024, 36 hours before a trade show launch, who discovered their nylon parts for a resin keychain display had warped because the room was humid. Normal turnaround on molded PC parts is 5 days. We found a vendor who could run a rush in 24 hours using a hydrolysis-resistant polycarbonate. Paid $1,200 extra in rush fees on top of the $4,500 base cost. Saved the $18,000 project. The alternative was showing up with nothing.

You hear “nylon is stronger” a lot. And it’s true—nylon has higher tensile strength dry. But wet? Polycarbonate holds its properties much better. That’s the hidden variable.

The Sustainability Angle: Where Covestro Actually Delivers

Covestro’s focus on sustainability isn’t just marketing fluff, but I want to be clear: we don’t claim 100% recyclability on everything. What we do have is a range of bio-based and recycled TPU and polycarbonate grades that actually perform. For something like a plastic chain exposed to outdoor weather or a resin keychain that might get sweaty or wet, a bio-attributed polycarbonate with enhanced hydrolysis resistance is a smarter choice than standard nylon in terms of lifespan.

To be fair, nylon still has its place. If you need high abrasion resistance and the part won’t see humidity, nylon is often cheaper. But for anything that touches moisture or needs dimensional stability in changing climates, polycarbonate wins.

Three Real-World Considerations I’ve Learned the Hard Way

After 5 years in procurement and emergency order management, here’s what I’ve come to believe:

1. Don’t rely solely on datasheet numbers. A nylon grade might show 12,000 psi tensile strength dry. At 50% relative humidity, it can drop 20-30%. Polycarbonate doesn’t change nearly that much. I’ve had to rush-order replacement parts twice because teams trusted dry numbers.
2. Think about the supply chain for rush orders. Polycarbonate from Covestro is broadly distributed. When I needed a hydrolysis-resistant grade for an emergency plastic chain order, I found it in stock at three suppliers. Nylon can be harder to source on short notice, especially specialty grades. That matters when you’re on a 48-hour deadline.
3. Cost per part is not the whole story. Nylon pellets might be 10-15% cheaper per pound. But you’ll lose that savings if parts fail in the field or you need tighter humidity-controlled storage. Our company lost a $35,000 contract in 2022 because we tried to save $800 on standard nylon instead of paying a small premium for hydrolysis-resistant PC. The customer’s product line failed in a high-humidity environment. We paid the replacement cost out of pocket to keep the account. That’s when we implemented our ‘hydrolysis-first’ policy for any outdoor or food-contact applications.

Boundary Conditions: When Nylon Still Makes Sense

I don’t want to sound like polycarbonate is always better. It’s not. Nylon is better for:

• Parts that see constant friction or wear (gears, bearings)
• Applications where some moisture absorption is actually desirable (like nylon bushings that swell for a tighter fit)
• Cost-sensitive projects where the environment is controlled (indoor, low humidity)

Also, polycarbonate can be more prone to stress cracking with certain chemicals. So if your plastic chain is going to be exposed to solvents or strong cleaners, check that. Nylon can handle some solvents better.

Industry standard color tolerance for branded parts is Delta E under 2. Polycarbonate generally holds color better than nylon in variable conditions, which matters for resin keychains or branded components.

Quick Decision Framework

Based on our internal data from 200+ rush orders and last quarter’s 47 rush jobs with 95% on-time delivery, here’s a simple way to decide:

• Will the part see humidity or water? → Polycarbonate (hydrolysis-resistant grade)
• Is high wear/friction the main requirement? → Nylon
• Do you need dimensional stability for tight tolerances? → Polycarbonate
• Is cost the absolute priority and the environment is dry? → Nylon

It took me years of mistakes to get comfortable with this. I’d rather spend 10 minutes explaining the difference upfront than dealing with an emergency order later. An informed customer asks better questions and makes faster decisions.