Although the types and functions of paper diapers on the market are different, their internal logic is actually the same. Deepen specific details through the main structure. What we want to discuss today is the direct contact with users, which is also the most important part affecting the user experience: surface layer.

1. Pervious principle

First of all, the baby's urine is directly exposed to the skin. But in fact, its liquid absorption is almost zero, which can only guide urine into the core layer, rather than the raw materials, thickness and structural density of weaving materials, which has an important impact on the water permeability of paper diapers. From the molecular point of view, the water permeability principle of the surface layer can be considered to have three main forms: the direct absorption of water molecules by fibers, the capillary between fibers and water pressure forcing water molecules through the fabric gap. Since the surface layer needs to be kept dry, hydrophobic fibers with low moisture absorption are usually selected, that is, the first water permeability method is excluded, and the second and third methods are the main water permeability methods of the surface layer.

2. Penetration time

Penetration time is an important measure of paper diapers. The penetration time of nonwovens is often related to their own structure. Therefore, in the structural design of nonwovens, the penetration time is often included in the reference factor, otherwise even if the exquisite structure has a long penetration time, it will seriously affect the performance of products. There are usually three forms: through hole, closed hole and semi closed hole. At present, the most commonly used materials are hot-air or hot-rolled nonwovens. Hot air nonwovens have a good spatial structure, and the liquid bends through most holes, that is, through holes; The fiber distribution of hot-rolled nonwovens is regular, the fiber around the rolling point is consolidated after hot rolling, and the thickness of nonwovens is thin, mainly closed holes and semi closed holes, so as to prolong the penetration time.

3. Back seepage

Back osmosis is another important index of paper diapers. Due to the compaction of rolling point, the area density of hot-rolled nonwovens increases. The rolling point is concave on the front of the surface layer, and the surface in contact with the guide layer and absorption core layer is convex. The liquid penetrates into the absorption core layer through the surface layer and guide layer. Due to external force, the liquid first contacts the convex surface formed by the rolling point. However, due to the high fiber density, close arrangement between fibers and small gap, it can hinder the rise of liquid and is not easy to exude. The thickness of hot air nonwovens is 3 ~ 5 times that of hot rolled nonwovens, textile adhesives, melt blown nonwovens and other nonwovens. Good spatial structure increases the gap between fibers. A certain thickness makes the liquid recovery channel complex. It can also be used as a barrier to prevent liquid flow, so as to reduce liquid reflux.

As a structure in direct contact with the skin, the importance of the surface layer in the paper diaper is self-evident. The first step for the paper diaper to give full play to its role is to check the surface layer.