The Secret Behind Diaper Getting Wet

Most mothers can tell at a glance whether their baby has urinated when changing diapers. Do you know why? There are two yellow lines on the surface of the diaper, which are the built-in wetness indicator function. The introduction of this feature has made it easier for inexperienced parents to handle diaper changes. Mothers can now judge how much urine the diaper has absorbed based on the color change of the wetness indicator, thereby reminding themselves to change the diaper in time, without having to wait until the diaper becomes swollen and heavy to realize it's wet.

So what is the principle behind the diaper's wetness indicator function? Currently, the more mainstream technologies are hot-melt wetness indicator adhesive technology and ink-based wetness indicator technology.

• Hot-melt wetness indicator adhesive:

The wetness indicator adhesive works by combining hot-melt adhesive with substances that are sensitive to PH changes and exhibit color variations. The adhesive is applied in lines on the side of the back sheet facing the absorbent core. When urine soaks the core layer and reaches the surface of the wetness indicator adhesive, it causes a change in pH value, resulting in a color change and achieving the visual monitoring effect of the wetness indicator.

• Ink-based wetness indicator:

The principle involves adding small colored molecules to the ink. When urine comes into contact with it, the ink and these small molecules are washed away by the urine, causing the color to disappear and achieving the alert effect.

Next, we selected several diapers with wetness indicator functions for evaluation to closely examine the magical wetness indicator lines.

1. Color-changing wetness indicator evaluation:
The sample selected for this evaluation is an M-size Shymoon brand soft cotton diaper. The evaluation results are as follows:

From the evaluation results, it can be clearly seen that the diaper's wetness indicator is yellow before absorption; after a high absorption diapers test of 500ml water, the color changes to green. When the entire wetness indicator line changes color, it proves that the diaper has absorbed the maximum amount of urine and needs to be changed.

2. Disappearing-type wetness indicator evaluation:

Now let's look at the evaluation of an M-size Japanese brand diaper's wetness indicator:

From the evaluation results, it can be clearly seen that the diaper's wetness indicator is blue before absorption; after absorbing 50ml of solution, the blue color gradually disappears, with about half gone; after absorbing 100ml, two-thirds of the blue disappears, which can serve as a reminder to change the diaper. When the wetness indicator line completely disappears, it proves that the diaper has absorbed the maximum amount of urine and needs to be changed.

The design of the diaper's wetness indicator may not be very useful for experienced parents, but it provides considerable convenience for new parents. It can promptly remind parents to change their baby's diaper, preventing issues like diaper rash or eczema caused by wetness, and make it more comfortable diapers during the growth conditions for baby.