The structural adhesive system in diapers is not composed of a single material, but rather constitutes a *composite structural system* formed by multiple layers of materials bonded together with adhesives. Its core function is to precisely bond various functional layers using hot-melt adhesives, creating a robust, lightweight, and elastic unified structure.
Top Sheet (Non-woven Fabric) + Hot-Melt Adhesive + Acquisition Layer
The top sheet consists of a skin-friendly non-woven fabric that comes into direct contact with the baby's skin. Through a spray-coating or slot-coating process, a hot-melt pressure-sensitive adhesive (HMPSA) is applied to specific areas to bond it with the underlying acquisition layer, thereby ensuring that urine penetrates rapidly and the layers remain securely in place.
Acquisition Layer + Hot-Melt Adhesive + Absorbent Core (Composite Core)
The acquisition layer guides the urine to disperse evenly; its underside is bonded via hot-melt adhesive to the absorbent core (such as a composite core comprising air-laid paper, SAP, and non-woven fabric). This structural configuration prevents the core from "clumping" or "delaminating" after absorbing liquid, thereby maintaining a flat and uniform surface.
Absorbent Core + Hot-Melt Adhesive + PE Backsheet/Breathable Film
The composite core is bonded to the underlying breathable PE backsheet using hot-melt adhesive to form a leak-proof barrier. During this stage, the quantity of adhesive and the temperature must be carefully controlled to prevent clogging the micropores in the backsheet, thereby ensuring breathability remains unimpaired.
Leak Guards & Elastic Bands + Elastic Strand Adhesive + Side Sealing Structure
Elastic bands are embedded within the leg leak guards; a specialized elastic strand adhesive is used to secure them between the non-woven fabric and the backsheet. This configuration enables elastic stretch and recovery, allowing the diaper to contour snugly to the baby's legs and effectively prevent side leakage.
