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PU Foam vs EVA vs Sponge Bra Cups Compared
Ask three lingerie factories what their bra cups are made of and you may get three answers: PU foam, EVA, or simply “sponge”. All three describe soft, formable materials, but they behave very differently once the cup is molded, washed twenty times, and worn on a hot afternoon.
This guide compares the three materials buyers actually meet in sourcing, and shows how to write the material line on a purchase order so nothing is left to interpretation.
The three materials buyers actually compare
PU foam (polyurethane foam)
PU foam is the mainstream material for molded bra cups, and it is what we produce at Senfeng. It is an open-cell foam, which means the tiny bubbles inside are connected to each other. Air and moisture vapour can travel through the structure rather than being trapped, which is the physical reason a PU cup can be made genuinely breathable.
Its second advantage is thermoformability. PU foam holds a molded three-dimensional shape reliably, so a cup keeps its profile through wear and washing instead of relaxing back toward flat. Our production runs at 160-200°C with 15-30 tons of press pressure and an 8-15 second dwell time, logged every shift so any batch stays traceable.
Typical Senfeng specification for PU foam cups:
- Density: 25-30 kg/m³
- Hardness: ILD 28-35
- Yellowing resistance: grade 4 or above
- Ventilation: 1.5-2 mm holes, 6-12 per cup, included as standard at no extra charge
If those two numbers are unfamiliar, we have covered them in detail in what PU foam density means for bra cup buyers and what ILD and rebound tell you about bra cup foam.
EVA (ethylene-vinyl acetate)
EVA is a closed-cell foam. Each bubble is sealed off from its neighbours, so water does not soak in and the material does not compress the way an open-cell foam does. That makes EVA excellent at holding a rigid, springy shape and at resisting water absorption, which is why it is common in shoe midsoles, sports padding and some swimwear components.
The same closed structure is its limitation for everyday bra cups. Because air cannot pass through the cell walls, an EVA cup traps heat and moisture against the skin, and drilling holes only helps at the holes themselves. EVA also feels firmer and bouncier than the soft, yielding hand most lingerie brands want against the body.
Conventional sponge (PE and polyester sponge)
“Sponge” is the loosest term of the three. In practice it usually means a low-cost PE or polyester foam used as a soft filler layer. It is cheap, light, and easy to cut, which is why it shows up in low-price bras and in cut-and-sew constructions where the fabric layers do the shaping.
The trade-off is durability. Low-density sponge loses thickness quickly under repeated compression, so the cup goes thin and creased after a season. Shape retention after molding is also weaker, making it a poor choice when the cup has to carry the garment’s silhouette.
Side-by-side comparison
| Property | PU foam | EVA | Conventional sponge |
|---|---|---|---|
| Cell structure | Open cell | Closed cell | Mostly open, low density |
| Breathability | Good, improved further with vent holes | Poor, sealed cells block airflow | Moderate |
| Shape retention after molding | Strong and long lasting | Strong but stiff | Weak, relaxes over time |
| Hand feel | Soft, yielding, skin friendly | Firm and springy | Soft but thin feeling |
| Water absorption | Absorbs, then dries | Very low | Absorbs and holds |
| Durability through washing | High | High | Low, thins out |
| Typical use | Everyday, sports and fashion bra cups | Protective padding, some water sports parts | Budget bras, soft filler layers |
Materials you will hear about but rarely buy
Two more materials come up constantly in sourcing conversations, so they are worth understanding even though most bra cup orders do not use them.
Memory foam is a viscoelastic PU variant. It softens with body heat and moulds slowly to the wearer, which feels luxurious in a fitting room. It is also slower to recover, heavier, warmer against the skin, and considerably more expensive. It suits premium comfort lines rather than volume production. To be clear: Senfeng does not produce memory foam cups. We mention it here as industry background, and if a project genuinely needs it we are happy to point you toward peers who specialise in it.
Latex, natural or synthetic, offers high elasticity and springy support, but cost, weight, heat sensitivity and the allergy question around natural latex keep most brands away from it in intimate apparel.
Matching material to garment
- Everyday and t-shirt bras: PU foam. Soft hand, stable shape, breathable.
- Sports bras: PU foam at the firmer end of the ILD band, with generous venting for heat and sweat management.
- Swimwear: PU foam cups are widely used, with fast-drying and chlorine exposure handled through material selection and construction. EVA appears mainly in structural or protective parts rather than the cup itself.
- Maternity and nursing: PU foam at the softer end of the band, with certified low-irritation materials against the skin.
- Budget promotional lines: conventional sponge can hit the price point, as long as everyone accepts the shorter useful life.
For a garment-by-garment breakdown, see how to choose bra cup type by garment.
How to write the material line on your purchase order
A material name alone is not a specification. “PU foam cup” can describe products that differ by half their service life. A workable line looks like this:
Molded PU foam bra cup, density 25-30 kg/m³, ILD 28-35, yellowing resistance grade 4 minimum, ventilation 1.5-2 mm holes at 6-12 per cup, OEKO-TEX Standard 100 compliant, physical sample sealed by both parties as the final reference.
The last clause matters most. Numbers set the range; the sealed sample settles anything the numbers cannot describe, such as hand feel and edge finish.
Where Senfeng fits
We are a molded bra cup factory in Dongguan, Guangdong. Our core product is PU foam molded cups, and we also work with sandwich mesh and laminated materials. We hold OEKO-TEX Standard 100, GRS and ISO 9001 certification, which covers restricted substances, recycled content and quality management respectively.
Practically, that means a library of over 2000 existing molds, samples in 1-2 days from an existing mold or 3-7 days for a new one, a 500-pair minimum order, and a finished-goods pass rate that holds above 95 percent with per-shift records behind every batch. Eight years of export experience with zero bad debt and Sinosure coverage sits behind the commercial side. You can browse our bra cup product range or read more about Senfeng Bra Cup.
Frequently asked questions
Is EVA better than PU foam for bra cups?
For breathability and hand feel against the skin, no. EVA resists water better and holds a rigid shape, which suits protective padding, but its closed cells trap heat and moisture, so PU foam remains the better everyday choice.
Can I tell PU foam and cheap sponge apart by hand?
Partly. Press a thumb firmly into the cup and release. Quality PU foam recovers smoothly with no lasting dent; low-density sponge stays creased or feels hollow. For anything contractual, ask for the density and ILD figures and confirm on a sealed sample.
Does Senfeng make memory foam or EVA cups?
No. We specialise in PU foam molded cups, plus sandwich mesh and laminated materials. If your project needs memory foam we can help you find a suitable partner rather than pretend it is our line.
Which material is best for swimwear?
PU foam cups are the standard choice, selected for fast drying and shape stability. Tell us the exposure conditions and we will recommend a specification and confirm it on a physical sample.
How quickly can I compare materials on a real sample?
From our existing mold library, 1-2 working days. A new mold takes 3-7 days. Minimum order is 500 pairs.
Contact us directly: WhatsApp +86 137 1289 0858 | Website: sf-bracup.com
