Views: 0 Author: Ocean Yang Publish Time: 2026-04-15 Origin: Ljvogues
Last week, a European client sent us a technical brief for a reusable incontinence underwear program. Halfway through the document, one line stood out:
"Absorbent core must use SAP encapsulated technology — not standard microfiber."
That single sentence told me two things. First, this buyer deeply understands the difference between period underwear and incontinence underwear. Second, the market has officially moved beyond the "one core fits all" era.
If you are a brand owner developing reusable leak-proof underwear, the most important technical decision you will make in 2026 is not the fabric, not the silhouette, and not the colour palette. It is the absorbent core architecture. And if you are building products for bladder leak (stress urinary incontinence) consumers — not just period care — then standard microfiber terry is no longer adequate.
Here is why. And here is what you should be specifying instead.
This sounds obvious. But the majority of reusable underwear brands treat them identically — using the same microfiber terry core for both period and incontinence products, differentiated only by marketing copy.
That is a fundamental engineering mistake.
Property | Menstrual Blood | Urine |
Volume per event | Gradual release, 5–15ml over hours | Sudden gush, 10–50ml in seconds |
Viscosity | Thick, slow-moving | Thin, fast-flowing, like water |
Release pattern | Continuous slow seep | Sudden burst under physical stress (cough, sneeze, jump) |
Pressure scenario | Low — wearer is usually stationary or walking | High — leaks happen during running, jumping, laughing, lifting |
pH | Slightly acidic (3.5–5.0) | Variable (4.5–8.0), more chemically aggressive over time |
A microfiber terry core works well for menstrual blood because the fluid arrives slowly, giving the fibres time to wick and absorb. The blood's higher viscosity means it tends to stay where it lands rather than spreading rapidly or being pushed out under pressure.
Urine is a completely different challenge. It arrives fast, in a large volume, with low viscosity — meaning it spreads rapidly across the core and actively seeks escape routes through seams and edges. Worse, bladder leaks typically happen during physical exertion — running, jumping, coughing, sneezing, laughing — which means the core is simultaneously being compressed by body movement.
A standard microfiber terry core under compression releases absorbed fluid back toward the skin. This is called rewetting or wet-back — and it is the number one complaint from incontinence underwear users who have switched from disposable pads to reusable underwear.
The consumer experience is devastating: she goes for a jog, has a small leak, the microfiber absorbs it — but when she sits down afterward, the compression squeezes the fluid back out onto her skin. She feels wet. She feels like the product failed. She never buys from that brand again.
Ljvogues-Microfiber towel core
SAP stands for Super Absorbent Polymer — a class of cross-linked sodium polyacrylate materials that can absorb 30 to 60 times their own weight in liquid. When SAP particles contact fluid, they undergo a chemical transformation: the liquid is pulled into the polymer structure through osmosis and converted into a stable gel that does not release the fluid back — even under significant mechanical pressure.
This is the same technology that powers disposable baby diapers, adult incontinence briefs, and medical-grade absorbent pads. It is why a disposable diaper can hold 1.5 litres of fluid without feeling wet on the surface. It is why clinical-grade SAP products maintain dryness for up to 12 continuous hours.
"Encapsulated" means the SAP particles are fixed within a structured matrix — typically a cellulose fibre web or a nonwoven pocket — rather than floating loose. This encapsulation serves three critical purposes:
Prevents migration: SAP particles stay in place during wear, movement, and washing — no clumping, no shifting, no dead zones in the core
Controls gel expansion: When SAP absorbs fluid, it swells. Encapsulation contains this swelling within a defined area, preventing the core from becoming lumpy or misshapen
Enables washability: In disposable products, SAP is single-use. In reusable underwear, the encapsulation structure allows the SAP to be washed, dried, and reused through multiple cycles while maintaining its absorption capacity
Based on the technical architecture that our European client specified — and that represents the current state of the art in reusable incontinence underwear — here is the full layer stack from skin to outer shell:
Function: First skin contact — must feel dry, soft, and non-irritating.
A soft performance mesh that allows liquid to pass through rapidly while preventing backflow. The key spec here is strike-through speed — how fast liquid penetrates the top layer and enters the absorption system below. Target: under 3 seconds.
Function: Catch the sudden gush and spread it evenly across the core.
This is the layer that differentiates incontinence cores from period cores. A fibrous nonwoven web that captures the rapid, high-volume urine release and channels it laterally across the full width and length of the absorbent zone. Without this layer, a sudden 30ml gush would overwhelm a single point in the core, causing pooling and side leaks.
Think of it as a highway system: liquid enters at one point, and the ADL distributes it across multiple lanes so the core can absorb it evenly.
Function: The main absorption engine.
This is where the SAP particles live — encapsulated within a structured fibre matrix. When fluid arrives (distributed by the ADL above), the SAP particles absorb it and convert it to gel. The absorption capacity here is massive: a well-engineered SAP core can achieve 50–100ml retention in a thickness of just 2–3mm.
The gel-lock mechanism is what makes SAP fundamentally different from microfiber:
Microfiber absorbs liquid into the spaces between fibres — and releases it when compressed
SAP absorbs liquid into the polymer itself — and holds it as gel even under pressure
This is why our client specified "not standard microfiber." For a stress incontinence scenario — where the wearer is running, jumping, or sitting down hard — microfiber gives back what it took. SAP does not.
Function: Contains the SAP gel expansion and prevents particle migration.
As SAP absorbs fluid, the particles swell to many times their original volume. This layer provides the structural containment, ensuring the core maintains a uniform profile without lumps or hard spots. It also prevents any loose SAP particles from migrating toward the skin or toward the waterproof barrier.
Function: Secondary absorption and final fluid capture.
A super-absorbent fibre block that acts as the last line of defense before the waterproof barrier. Any fluid that passes through the primary SAP core (during an extremely heavy leak event) is captured here. This creates a dual-lock system — primary absorption in Layer 3, secondary absorption in Layer 5 — that provides protection redundancy.
Function: The final barrier — blocks liquid, allows vapour to escape.
A PFAS-free TPU membrane that prevents any fluid from reaching the outer shell. The breathability spec matters here: because SAP gel retains heat slightly more than microfiber, the backing layer needs a higher MVTR (Moisture Vapour Transmission Rate) to prevent the gusset zone from feeling warm and humid.
SAP package absorber core structure
For brand owners making the core technology decision, here is the honest comparison:
Dimension | Standard Microfiber Terry | SAP Encapsulated Core |
Absorption mechanism | Capillary action (liquid held between fibres) | Osmotic absorption (liquid converted to gel inside polymer) |
Absorption capacity | 10–30ml typical | 50–120ml achievable |
Rewetting under pressure | High — compression squeezes fluid back to surface | Very low — gel locks fluid even under body weight |
Absorption speed | Moderate (wicking takes time) | Fast (SAP absorbs on contact) |
Best for | Period care (slow, viscous flow) | Incontinence (fast, sudden, high-volume) |
Thickness at 30ml capacity | 3–4mm | 2–2.5mm |
Odour control | Limited — liquid remains in fibre spaces | Strong — gel encapsulation traps odour molecules |
Wash durability | Excellent (100+ cycles) | Good (60–80 cycles depending on encapsulation quality) |
Cost | Lower | Higher (SAP material + encapsulation engineering) |
Ideal product | Period underwear, light daily liners | Moderate-to-heavy incontinence, sport incontinence, overnight protection |
The bottom line: microfiber terry is a sufficient technology for period care, but an insufficient technology for serious incontinence protection. If your product promises bladder leak protection and your core is standard microfiber, you are setting your customer up for rewetting failures — especially during the active scenarios (exercise, daily movement, sleep position changes) where incontinence actually happens.
This is the question every brand asks, and it is the right question. Disposable SAP is designed for single use. Reusable SAP must survive repeated washing and drying without losing absorption capacity.
The answer depends entirely on encapsulation quality.
Cheap SAP integration (particles loosely scattered between fabric layers) will degrade quickly — particles wash out, clump together, or lose their absorption capacity after 20–30 washes.
Professional SAP encapsulation (particles fixed within a structured nonwoven matrix with thermal or ultrasonic bonding) can maintain 85–90% of original absorption capacity through 60–80 wash cycles. Some next-generation encapsulation systems using hydrophilic fibre matrices are now pushing toward 100-cycle durability.
For brand owners, the critical specification is: ask your manufacturer for wash-cycle degradation data. Not just "it's washable" — but exactly how much absorption capacity remains at cycle 30, 50, and 80. If they can't provide this data, they haven't tested it. And if they haven't tested it, your customer will be the test subject.
Not every product needs SAP. And not every product should use standard microfiber. Here is a practical framework:
Product Category | Recommended Core | Why |
Light period underwear (10–20ml) | Microfiber terry | Slow flow, low pressure, cost-effective |
Heavy period underwear (30–50ml) | Microfiber terry or hybrid (microfiber + light SAP) | Higher capacity needed, but flow is still gradual |
Light bladder leak (10–20ml) | Microfiber with enhanced ADL layer | Small volume but fast release — needs better distribution |
Moderate bladder leak (30–50ml) | SAP encapsulated | Fast, sudden release under physical pressure — rewetting resistance critical |
Heavy incontinence (50–100ml+) | Full SAP encapsulated with dual-lock system | Maximum capacity, maximum pressure resistance, overnight protection |
Sport / active incontinence | SAP encapsulated, ultra-thin | Compression during exercise makes rewetting resistance non-negotiable |
Postpartum (mixed fluid) | Hybrid (microfiber + SAP) | Manages both lochia (blood) and stress incontinence simultaneously |
This framework should guide your conversations with your manufacturing partner. If they offer only one core type for all product categories, they don't understand the clinical differences between the use cases — and your customers will pay the price.
Different absorbency levels of sanitary underwear are available to meet customer needs.
In 2026, the incontinence underwear landscape is undergoing a fundamental shift:
Ultra-thin absorbent technology using advanced SAPs allows designs that are no thicker than standard underwear while providing clinical-grade protection
Nanotechnology-enhanced SAPs embedded within absorbent gels enable faster retention and superior leak protection without increasing bulk
"Dry-Fast" technologies enable absorption in under 3 seconds, instantly eliminating the sensation of moisture
The average thickness of absorbent protection has decreased by 40% since 2020 thanks to next-generation super-absorbents
The best washable incontinence underwear now measures no thicker than 5mm (0.2 inches) in the absorbent zone — completely invisible under trousers
These aren't future promises. These are shipping products, available now, being purchased by consumers who are migrating from disposable pads to reusable underwear at an accelerating rate.
The brands that offer SAP-encapsulated reusable incontinence underwear in 2026 are positioning themselves in the premium, clinically-credible tier of the market. The brands still using microfiber-only cores for incontinence are increasingly being left behind — both in product reviews and in consumer trust.
At Ljvogues, we manufacture both microfiber terry cores and SAP encapsulated cores — because different products need different solutions.
Core Technology | Available Capacity | Thickness | Application |
Standard Microfiber Terry | 10–50ml | 2–4mm | Period underwear, light daily protection |
SAP Encapsulated Core | 30–120ml | 2–3mm | Moderate-to-heavy incontinence, sport incontinence, overnight |
Hybrid Core (Microfiber + SAP) | 20–60ml | 2–3mm | Postpartum, mixed-use, moderate bladder + period |
All cores are available with PFAS-free TPU barriers, OEKO-TEX certified fabrics, and full REACH/SVHC compliance documentation.
When a client comes to us and says "I want to make incontinence underwear," our first question is not "what colour?" It is: "What is the clinical scenario? What volume, what speed, what pressure? And what is the wearer doing when the leak happens?"
Because the answer to those questions determines the core. And the core determines whether your customer trusts your product — or throws it away after one failure.
Developing a reusable incontinence underwear line? Tell us your target absorbency, your target use case, and your target consumer — and we will recommend the right core architecture for your product. We can ship SAP-encapsulated counter-samples for evaluation within one week.
Ocean Yang is the CEO of Ljvogues, a Shenzhen-based manufacturer specializing in functional intimate apparel. He builds cores that don't give back what they take — because for the woman relying on your product during a morning run, a work meeting, or a full night's sleep, "rewetting" is not a technical term. It's a broken promise.
Ocean Yang
