A diaper is the hardest test any fluff pulp faces. It must absorb fast, hold capacity under load, stay thick after being compressed in a bag, and feel soft against skin that cannot complain.
Application Overview
A modern diaper is a layered structure: a topsheet, an acquisition and distribution layer (ADL), an absorbent core built from fluff pulp and superabsorbent polymer (SAP), and a backsheet. Fluff pulp appears in the ADL and the core, and it does two jobs at once — it provides the capillary network that pulls liquid away from the skin, and it holds the SAP particles in a fixed, distributed position.
When a core fails, it usually fails in one of three ways: it collapses after packaging, it releases liquid back to the surface under pressure (rewet), or it lets SAP migrate and clump. All three trace back to fiber properties — bulk, fines content and fiber length — rather than to SAP quality alone.
That is why diaper development is a fiber conversation, not just a SAP conversation.
Product Formats We Support
Premium Taped Diapers
High-bulk cores with thickness retention as a visible quality cue
Pull-Up Pants
Cores that survive repeated stretching and compression in the pack
Newborn & Preemie
Small-format cores where absorption speed matters more than total capacity
Overnight Products
High-capacity cores requiring wet integrity through long wear
ADL Layers
Open, fast-wicking structures with controlled density gradients
Eco-Positioned Lines
Bamboo and unbleached fiber options with a documented material story
Typical Requirements and Our Approach
| Requirement | Typical Target | How We Meet It |
|---|---|---|
| Thickness after packaging | ≥ 85% of pre-compression thickness | Long-fiber softwood with fines below 6% resists compaction and recovers |
| Absorption rate | First wetting under 3 s (ADL) | High-freeness fiber opens into an open-pored structure that wicks fast |
| Rewet under pressure | Below 0.5 g at 3.5 kPa | Bulk retention keeps pore structure open instead of collapsing wet |
| SAP retention | No visible migration after vibration | Long-fiber network mechanically traps particles in place |
| Softness | Smooth surface, no protruding fiber | Bamboo or hardwood blend at 30–50% for skin-contact layers |
| Unit cost | Target defined per SKU | Blend ratio tuned against the performance floor, not above it |
Targets vary by market and product tier. The values above are starting points for a specification discussion, not a universal standard.
Detailed Description
The core is a structure, not a mixture
Fluff pulp and SAP do different jobs. SAP absorbs and holds liquid; fluff pulp creates the void volume that lets liquid reach the SAP quickly and distributes it across the core. A core with excellent SAP and poor fiber structure will show slow absorption and high rewet, because liquid never reaches the SAP fast enough.
This is why increasing SAP loading often fails to fix a rewet problem. The constraint is the transport network, and the transport network is fiber.
Where thickness goes missing
Diapers are compressed hard during packaging and transport. A core built on high-fines pulp compacts under that pressure and never recovers, so the product arrives thin. Consumers read thin as “less absorbent” regardless of the actual capacity. Long-fiber, low-fines pulp is the direct fix, and it usually allows a small reduction in basis weight at the same delivered thickness.
If a customer complains the product feels thin out of the pack, measure thickness after compression, not before. The number before packaging tells you nothing about what the consumer experiences.
Choosing between bleached, blended and bamboo
Bleached softwood is the default for the structural core. Blended pulp takes cost out of volume tiers where the performance floor allows it. Bamboo enters where the product is sold on softness or a natural material story — usually at 30–50% in the skin-contact layers rather than as the whole core.
