Diaper structures are divided into: topsheet, flow-through layer, cover layer, absorbent layer, side leakage prevention layer, and composite backsheet.
Topsheet:
1. Air-through nonwoven fabric: The main material is PP/PE bicomponent staple fibers, which are self-melted and bonded together based on the different melting points of the two materials. Standard air-through nonwoven fabrics and whitening air-through nonwoven fabrics are available on the market. The staple fibers are all hydrophilic. Hot-through hydrophilic fabrics are further divided into single-pass hydrophilic and multi-pass hydrophilic. Choose according to customer needs. Multi-pass hydrophilic hot-through nonwoven fabrics are generally used for diapers, while single-pass hydrophilic products can be used for sanitary napkin topsheets. While these fabrics offer softness and comfort, their disadvantages are low strength and linting, leading to higher costs. This is achieved by using 22-28gsm products (due to limitations in hot-through production lines, products below 22gsm are difficult to produce, and their weight is too low to meet demand).
2. Hot-rolled nonwoven fabric: The main material is PP staple fibers, which are combed by a carding machine and then hot-rolled by a hot-rolling machine. This type of fabric is characterized by relative softness and average surface uniformity. However, its production cost is high and its production capacity is low.
3. Perforated Nonwoven Fabric: This type of fabric is typically made from 20gsm or 22gsm spunbond, whitened, multi-layered hydrophilic nonwoven fabric. It is characterized by its softness, low linting, and characteristics of air-through nonwoven fabrics. The requirements for perforated nonwoven fabric vary from company to company and are determined by their perforation process. It is popular in the domestic, Japanese, and Korean markets and has relatively high quality requirements.
4. Spunbond, multi-layered hydrophilic nonwoven fabric is low-cost and primarily used in the low-end market. Typically, a 15gsm white, multi-layered hydrophilic product is used.
The distribution layer：
is typically made of PP/PET bicomponent short-fiber air-through nonwoven fabric (multiple hydrophilic), with a typical weight of around 40-45g. Some manufacturers offer lower weights to reduce costs (too low a weight may not evenly distribute urine longitudinally). Some domestic manufacturers also use spunbond nonwoven fabric with multiple hydrophilic properties to replace the distribution layer (fake distribution) to reduce costs.
The covering layer ：
is typically made of 15-20g dust-free paper and 10-12g multi-hydrophilic spunbond nonwoven fabric. The disadvantage of dust-free paper is that it increases the chance of the diaper bursting after saturation. This is less likely with spunbond nonwovens. Dust-free paper is also weaker than nonwovens.
Absorbent layer:
Also called a water-locking layer, it’s typically made from a mixture of wood pulp fluff and a water-absorbent polymer (SAP). SAP can absorb up to 2,000 times its own weight in water.
Leak prevention:
11-15gsm white SMS spunbond meltblown composite nonwoven fabric is typically used. 15gsm SMS should have a hydrostatic pressure resistance of at least 150mm, but the single value requirement is relatively high. Its primary function is to prevent unabsorbed urine from leaking out of the diaper, providing a barrier.
Composite backsheets:
1. Hot air-through water-repellent nonwoven composite breathable film;
2. Hot-rolled conventional nonwoven composite breathable film;
3. Spunbond conventional perforated nonwoven composite breathable film;
4. Spunbond conventional nonwoven composite breathable film.