Recycled Nylon vs Recycled Polyester in Performance Knits

Both fibers carry the same GRS certification logo, but they behave differently on the knitting machine, in the dye house, and in the finished garment. Recycled nylon (rPA) comes from post-industrial fishing nets, carpet fibers, and fabric scraps. Recycled polyester (rPET) comes from post-consumer plastic bottles and, to a lesser extent, post-industrial polyester waste. The feedstock difference drives most of the performance divergence — and it matters more than most sourcing guides acknowledge.

Fiber Properties: Where the Two Diverge

Recycled nylon has a moisture regain of about 4.0–4.5%, compared to recycled polyester at 0.4–0.8%. That five-to-one gap in moisture absorption changes how each fiber feels against the skin. rPA wicks moisture more effectively, which is why it dominates in base layers and next-to-skin performance knits. rPET, by contrast, sits drier on the surface — it doesn’t absorb moisture but instead pushes it along the fiber surface through capillary action in the yarn structure.

Tenacity is the other major difference. Recycled nylon 6,6 (from fishing nets and industrial waste) typically runs 5.5–7.0 cN/dtex. Recycled polyester from bottle-grade chip runs 4.5–5.5 cN/dtex. The higher tenacity of rPA means the yarn survives more abrasion cycles before pilling or breaking, which translates directly to garment durability. A recycled nylon performance knit will typically achieve ISO Grade 4 on the Martindale abrasion test at 30,000 cycles, while the equivalent rPET knit reaches Grade 3–4 at the same cycle count.

Elongation at break also differs: rPA stretches 25–40% before breaking, while rPET breaks at 15–30%. The higher elongation gives recycled nylon better recovery from deformation — a knitted rPA fabric bounces back more aggressively after being stretched, which is why it’s preferred in fitted performance garments like compression wear and swimwear.

Dyeing and Color: The Hidden Cost Difference

This is where sourcing decisions get expensive. Recycled nylon dyes with acid dyes, which offer a wide color gamut and excellent wash fastness (AATCC Grade 4–5). Recycled polyester requires disperse dyes, which have a narrower gamut and lower wash fastness (AATCC Grade 3–4 for standard depths).

The practical consequence: if your brand needs deep, saturated colors — navy, black, forest green — recycled nylon holds them more reliably through repeated home laundering. Recycled polyester in dark shades tends to show more surface fuzzing and color loss after 20+ washes, because the disperse dye molecules are smaller and migrate more easily under mechanical agitation.

For light and bright colors, the gap narrows. Both fibers handle pastels and mid-tones well. But there’s a cost difference in the dye house: acid dyeing of rPA runs at 95–100°C for 45–60 minutes, while disperse dyeing of rPET requires 130°C (high-temperature dyeing machine) for 30–45 minutes. The higher temperature means higher energy cost — roughly 15–20% more energy per kilogram of fabric for rPET dyeing.

Knitting Performance: What the Machine Operator Sees

On circular knitting machines, recycled nylon and recycled polyester behave differently in terms of yarn friction and loop formation. rPA has a lower coefficient of friction (0.20–0.25) compared to rPET (0.30–0.35), which means rPA yarns run through the knitting elements with less drag. This translates to fewer yarn breaks per 100 kg of fabric — typically 3–5 breaks for rPA versus 8–12 for rPET at the same machine speed.

The lower friction of rPA also means the knitted fabric has a smoother surface right off the machine, with less visible needle lines. rPET fabrics tend to show more needle lines and require additional finishing (singeing or brushing) to achieve the same surface smoothness. On a 300-loom mill, this finishing step adds USD 0.10–0.20 per meter for rPET knits that rPA knits don’t need.

For brands that run both fibers, the machine settings need adjustment. rPA knits at slightly lower tension (because the yarn stretches more), and the take-down speed needs to be calibrated for the higher elongation. Switching from rPET to rPA on the same machine without adjusting tension can cause loop length variation and fabric weight inconsistency.

Cost and Certification: What Buyers Actually Pay

Recycled nylon 6,6 commands a significant price premium over recycled polyester. At current market rates (mid-2026), GRS-certified rPA 6,6 yarn costs USD 3.80–4.50 per kg, while GRS-certified rPET yarn from bottle-grade chip costs USD 1.60–2.20 per kg. That’s roughly a 2× price gap at the yarn stage.

In finished knit fabric, the gap narrows because the knitting, dyeing, and finishing costs are similar for both fibers. A 160 GSM single jersey in rPA runs USD 5.50–7.00 per meter (FOB), while the equivalent in rPET runs USD 3.80–4.80. The fabric cost difference is about 35–45%, not the full 100% yarn gap, because the processing costs dilute the raw material premium.

Both fibers are eligible for GRS certification, which verifies the recycled content and tracks it through the supply chain. The U.S. Environmental Protection Agency reports that textile recycling diverted 3.2 million tons of materials from landfills in 2021, with polyester accounting for the largest share due to bottle-to-fiber programs. However, GRS certification alone doesn’t differentiate between pre-consumer and post-consumer content — for that, buyers need to check the transaction certificates (TCs) issued by the certification body.

For brands sourcing from a mill like Fursone, the choice between rPA and rPET often comes down to the end-use. Performance knits for next-to-skin applications (base layers, activewear, swimwear) justify the rPA premium. Outer layer knits, linings, and less demanding applications work well with rPET at lower cost. For more on how to verify the certification claims on either fiber, see our guide to GRS certificate verification.

Recyclability at End of Life: A Complicated Picture

Both fibers can theoretically be recycled again, but the reality is different. Recycled nylon 6 can be depolymerized back to caprolactam and repolymerized into virgin-equivalent nylon 6 — this is the process used by Aquafil’s ECONYL program. Recycled nylon 6,6 cannot be depolymerized as easily because the adipic acid component degrades at high temperatures, so rPA 6,6 is typically downcycled into lower-value applications.

Recycled polyester can be mechanically recycled again (melted and re-spun), but each cycle reduces the intrinsic viscosity by about 10–15%, limiting the number of recycling loops to roughly 3–5 before the fiber properties fall below usable thresholds. Chemical recycling of rPET (depolymerization to monomers) is technically possible but not yet commercial at scale.

For brands building a sustainable fabric program, the practical takeaway is: specify rPA 6 (not 6,6) if closed-loop recyclability is a priority, and specify rPET if cost is the primary constraint. Both carry GRS certification, but only rPA 6 has a commercially proven path back to virgin-equivalent fiber.