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Is Higher SAP Content in a Diaper Core Always Better? How to Balance Absorbency and Cost?
Is Higher SAP Content in a Diaper Core Always Better? How to Balance Absorbency and Cost?
More SAP Does Not Always Mean Faster Absorption
The job of SAP is to lock in liquid, not to distribute it. SAP particles swell into a gel when they absorb liquid, which locks the fluid inside the core. But if the SAP ratio is too high, liquid cannot be pulled deep into the core quickly – it pools on the surface. In simple terms, absorption slows down and leaks become more likely. Industry tests show that when SAP content in the core exceeds about 60%, absorption speed drops noticeably. That is why a pure SAP core is not practical. It needs wood pulp to help distribute the liquid. For mainstream Baby Diapers, the ratio of wood pulp to SAP is roughly 1:1.
⭐Too Little SAP Reduces Dryness
On the other hand, if there is too little SAP, the core relies mainly on wood pulp. Once wood pulp is saturated, any pressure pushes liquid back to the surface – the pad feels wet. Today, SAP is one of the most expensive raw materials in a diaper core. The amount of SAP directly affects the exfactory price. A quick formula: a diaper with SAP is about 30% to 60% more expensive than an all wood pulp diaper. That extra cost buys visible performance improvements: lower rewet, a thinner core, and easier movement for the baby.
How to Find the Best Balance? Depends on Target Market and Price Point
For a mid range baby diaper, SAP content can be set at 35% to 45%, combined with wood pulp and an acquisition distribution layer (ADL). This ensures basic dryness without making the product too expensive. For a premium ultra thin diaper, SAP content can be increased to 50% to 55%, the core compressed to about 2 mm, and absorption speed also needs to be faster. For Adult Pull Up Pants, adults urinate a larger volume at once, so the locking requirement for SAP is higher than for baby diapers. Typically, SAP content is set at 45% to 55%, and the backsheet also needs better breathability.