Key Performance Indicators of Diaper Polymer: Absorption, Retention and Gel Stability

Introduction

Selecting a suitable diaper polymer requires more than comparing basic absorption capacity.
In modern diaper engineering, performance evaluation focuses on how super absorbent polymer behaves under realistic use conditions.

This article explains the key performance indicators (KPIs) used to evaluate super absorbent polymer for diaper applications and how these parameters influence diaper performance.

Why Free Absorption Alone Is Not Enough

Free absorption capacity measures how much liquid SAP can absorb without load.
While useful as a reference, this parameter alone does not reflect real diaper performance.

Diapers operate under continuous pressure, making retention behavior and liquid stability far more critical than free absorption values.

Absorption Speed and Intake Efficiency

Absorption speed determines how quickly SAP captures liquid after insult.

Fast intake reduces the risk of surface wetness and leakage during initial wetting. However, extremely rapid swelling without sufficient structure can negatively affect liquid distribution.

Balanced absorption speed is therefore essential for effective diaper polymer performance.

Absorption Under Pressure

Absorption under pressure evaluates how well SAP retains liquid when compressed.

This KPI is considered one of the most critical indicators of diaper polymer performance because it directly influences:

• Rewet levels

• Leakage risk

• Wearer comfort

SAP grades designed for diapers prioritize stable retention under pressure rather than maximum free absorption.

Gel Strength and Gel Stability

Gel strength describes the mechanical stability of swollen SAP particles.

Strong gel structure helps prevent gel blocking, a phenomenon where swollen particles restrict liquid flow within the core. Controlled gel strength supports uniform absorption and sustained performance during repeated wetting.

Particle Size Distribution and Core Uniformity

Particle size distribution affects how SAP is dispersed within the diaper core.

Uniform particle distribution promotes even absorption and reduces localized saturation. Excessively fine or coarse particles may negatively impact intake speed or retention stability.

Evaluating Diaper Polymer as a System

No single KPI defines diaper polymer quality.
Industry evaluation focuses on the combined performance of absorption speed, retention under pressure, gel stability, and particle distribution.

This system-level approach explains why SAP selection must be aligned with diaper core design and production conditions.

For a complete overview of diaper polymer selection and application, refer to the main page on super absorbent polymer used in diaper absorbent materials.