Is a plastic-free bikini or swim trunk possible?

Hey founders,

If you're showing at Miami Swim Week this year, you've probably gotten the question from buyers already. "Is your swim line plastic-free?" Maybe in the first meeting. Maybe in the follow-up. But it's coming.

And I'll be honest: the first time I heard a buyer ask this, I had to pause. Because the answer is not a clean yes or no. It's more like, "Define plastic-free, and I'll tell you what's actually possible."

So let's do that. Let's walk through what 'plastic-free swimwear' actually means at the fiber level. Where we are today. Where the science is blocked. And what you can actually put on a runway or a line sheet right now.

What's in a traditional swimsuit, anyway?

Most swimwear on the market today is built from some combination of nylon and spandex. That's been the industry standard for decades, and there's a reason: the fiber blend gives you stretch, recovery, chlorine resistance, and shape retention. The combination works.

The problem is that both fibers are petroleum-derived plastics.

Nylon, or polyamide, is synthesized from adipic acid and hexamethylenediamine, both derived from fossil fuels. Spandex (also called elastane or Lycra) is a polyurethane-based fiber, also built from petroleum feedstocks. So when we say "plastic" in this context, we mean: the raw material came from crude oil, and the resulting fiber is a synthetic polymer that does not biodegrade in any meaningful timeframe.

What about recycled fabrics? ECONYL, REPREVE, all the regenerated nylon and polyester programs?

They're a step in the right direction. They divert plastic waste from landfills and oceans. They reduce the demand for virgin petroleum extraction. But here's the part that most brands don't love hearing: recycled nylon and recycled polyester are still plastic. They still shed microplastic fibers. The feedstock changed. The polymer didn't.

The microplastic shedding problem

This is where the conversation gets uncomfortable.

A single wash cycle can shed between 700,000 and 12 million microplastic fibers, depending on the fabrics in the load. Synthetic textiles are now the largest source of microplastic pollution in the ocean, accounting for roughly 35% of all primary microplastics.

And it's not just washing. The fabrics commonly used in the manufacture of swimwear, notably nylon and polyester, are under scrutiny for their propensity to shed microfibres upon immersion in aquatic environments. This phenomenon raises pivotal concerns regarding the sustainability of traditional swimwear materials. The exposure to water during swimming, whether in the ocean or pools, acts as a catalyst for the release of these minuscule fibres.

A recent study by Arizona State University researchers found that swimsuits significantly increase microplastic levels in pools and nearby rivers. Published in the journal Water Emerging Contaminants & Nanoplastics, the study found that swimsuits significantly increase microplastic levels in pools and nearby rivers like the Salt River. They discovered a nearly tenfold increase in microplastics following peak visitor hours. "Before, there were around 20,000 to 27,000 microplastics per cubic meter of water," explained study author Kanchana Chandrakanthan. "At peak activity time, it spiked to about 222,000."

So when a buyer asks about plastic-free, they're asking about more than feedstock. They're asking about what happens when that suit hits water.

The bio-nylon solution

Here's where real progress is happening.

The nylon portion of your swimwear can now be derived from plant-based sources instead of petroleum. The most commercially viable pathway uses castor oil from the castor bean plant.

Nylon 11, also known as polyamide 11 (PA11), is a high-performance engineering plastic known for its chemical resistance, flexibility, and durability. Unlike conventional nylons like Nylon 6 or 6,6 derived from fossil feedstocks, Nylon 11 is 100% bio-based, made from castor oil, a non-edible, drought-resistant crop cultivated primarily in India and Brazil.

Castor oil is extracted from castor beans (Ricinus communis), grown primarily in India, Brazil, and China. It contains approximately 90% ricinoleic acid. It's a non-food crop with minimal competition with global food supply. It grows in arid regions with minimal irrigation needed.

The process works like this: castor seeds are cold-pressed to extract castor oil. That oil is converted through a series of chemical steps into a monomer called 11-aminoundecanoic acid. That monomer is then polymerized into nylon 11. The resulting fiber is chemically similar to conventional nylon but derived from renewable biomass instead of crude oil.

In one recent example, Arkema was capable of reducing the carbon footprint of biobased Rilsan 11 by around 70% compared to traditional nylon production, achieving less than 2 kg CO2e/kg.

And the performance? "We wanted an eco-friendlier nylon, and we were looking for an environmentally sustainable nylon made with bio-renewable sources that do not conflict with plants for human consumption," explains one creative director. "The outcome is a fiber not too shiny, not too opaque, strong and versatile."

Brands are already using this. The fashion industry is making strides in sustainable material innovation with the adoption of Evo fiber, a bio-based yarn derived from the drought-tolerant castor oil plant. This development offers a direct alternative to conventional nylon, a fossil-fuel-dependent synthetic. Brands like Reformation and Lululemon are already integrating Evo fiber into swimwear and T-shirts.

The stretch problem: why 100% plastic-free is essentially impossible today

Here's where most "plastic-free" claims fall apart.

You can source bio-based nylon. That's real, proven, commercially available. But swimwear needs stretch. And stretch comes from elastane.

Conventional elastane is 100% petroleum-derived. It's a polyurethane-urea copolymer made through complex petrochemical synthesis. Elastane is a plastic derived entirely from petroleum. Its entire lifecycle, from extraction to polymerization, relies on fossil fuels, contributing to climate change and resource depletion.

Without elastane, you don't get 4-way stretch. You don't get shape retention. You don't get the recovery that makes a swimsuit hug your body instead of bagging out after one pool session.

So what about bio-based stretch fibers?

They exist. Today, one offering is a more eco-friendly spandex derived in part from plants. Renewable LYCRA fiber is crafted from 70% plant-based ingredients, including dent corn grown in the US Midwest.

Hyosung's bio-spandex uses sugar-cane-based feedstock, which offers several advantages over corn-derived alternatives, including lower land-use intensity, reduced fertilizer requirements, and improved overall environmental efficiency.

There's also YULASTIC, a plant-based, sustainable alternative to elastane. Developed by Yulex, the pioneers behind natural rubber-based wetsuits, YULASTIC is a fine, natural rubber filament harvested from the Hevea brasiliensis tree. It's fully renewable, responsibly sourced, and poised to become the go-to stretch fiber for brands looking to reduce their reliance on synthetic materials.

But here's the catch: bio-based elastane at commercial scale for swim-specific applications is still emerging. The 70% plant-based formulations are real, but they're not 100%. And the natural rubber alternatives are better suited for knits and denim right now than chlorine-exposed performance swim.

What 99.5% plant-derived actually looks like

So if 100% plastic-free performance swimwear isn't quite there today, what is achievable?

The best formulation I've seen for swim: 76% bio-based nylon from castor, corn, and straw feedstocks combined with 24% bio-based elastane.

Let me break that down:

• 76% bio-nylon: Derived from plant sources (primarily castor oil). Replaces the petroleum-based nylon 6 or nylon 66 in conventional swimwear.
• 24% bio-based elastane: The stretch component. Current bio-based formulations get you to around 70% plant-derived content in the elastane portion.

When you do the math, a 76/24 blend where the nylon is 100% bio-based and the elastane is 70% bio-based gets you to roughly 99.5% plant-derived content overall. The remaining fraction is the petrochemical component in the stretch fiber.

That's not marketing spin. That's what the chemistry allows right now.

Performance specs: what actually matters for swim

Buyers at Miami Swim Week aren't just asking about sustainability. They're asking whether your fabric will hold up. Here's what matters:

Chlorine resistance

Swimwear lives in chlorinated water. If your fabric degrades after 20 pool sessions, you don't have a product. Bio-based nylon (PA11) actually has excellent chemical resistance. The castor-derived polymer structure holds up well against chlorine exposure, comparable to conventional nylon.

4-way stretch

This is the ability to stretch in both horizontal and vertical directions. A 76/24 bio-nylon and bio-elastane blend delivers true 4-way stretch. Your customer can move in every direction without restriction.

Rebound (elastic recovery)

Rebound is whether the fabric snaps back after being stretched. Industry benchmark is around 95% recovery. In lab tests, plant-based stretch fibers matched synthetic elastane in strength, elongation, and durability, and actually outperformed in elastic recovery, which means stretch fabrics bounce back better, keeping their shape longer.

OEKO-TEX 100 certification

This one matters for retail and especially for any buyer thinking about EU markets or eco-conscious positioning.

OEKO-TEX STANDARD 100 is one of the world's best-known labels for textiles tested for harmful substances. OEKO-TEX STANDARD 100 is an independent testing certification that verifies a finished textile product, every thread, button, and accessory, has been tested against over 1,000 harmful substances and found to be safe for human health.

PFAS are banned in all OEKO-TEX standards, including STANDARD 100. That means your bio-based swimwear can carry the certification without worrying about the PFAS regulatory wave hitting the industry.

For operator purposes: OEKO-TEX 100 certification means your fabric has been third-party tested and verified safe for direct skin contact. No heavy metals, no banned azo dyes, no carcinogenic compounds, no PFAS. OEKO-TEX Standard 100 certification is valid for 12 months and must be renewed annually.

What to tell buyers at Miami Swim Week

Here's my advice for how to position this:

Don't say "plastic-free" if you're using any elastane, even bio-based. The stretch component still has a petrochemical fraction. Saying "plastic-free" when you're 99.5% plant-derived is technically false and opens you up to greenwashing claims.

Do say:

• "99.5% plant-derived"
• "76% bio-based nylon from renewable feedstocks"
• "Bio-based stretch fiber"
• "Drastically reduced petroleum content"
• "Lower microplastic shedding profile" (if you have the test data to back it)

Buyers at the Hammock Show and PARAISO are smart. They've seen the greenwashing. They want specifics. Give them the numbers.

The honest answer

Is a 100% plastic-free bikini or swim trunk possible today? Technically, not quite. The stretch fiber problem isn't fully solved for chlorine-exposed performance swim applications.

But is 99.5% plant-derived possible? Yes. And that's a massive shift from where the industry was even three years ago.

The bio-nylon tech is proven. The bio-elastane is getting better every season. The performance matches or exceeds conventional petroleum-based swim fabrics on chlorine resistance, stretch, and recovery.

"The industry has already shifted. The question now is whether your brand is going to lead that shift or play catch-up."

Miami Swim Week 2026 runs May 27-31. This season's new initiative sits at the intersection of fashion, sustainability, and philanthropy. If your fabric story isn't ready, you're missing the moment.

For what it's worth, this is exactly the problem we built OHZEHN-TEX to solve: a 76/24 bio-nylon and bio-elastane platform that delivers swim-ready performance with OEKO-TEX 100 certification. But regardless of who you source from, get clear on your fiber story before you land in Miami.

The buyers are asking. Make sure you have an answer.

Cheers,

Dougie

Dougie Taylor

Co-Founder, Ohzehn Textiles · Forbes & Inc. recognized brand operator