•  On Apr, 08, 2022
•  admin
•   PVA Sponge

We have discussed about the PVA sponge water retention ability earlier, and in this article, we want to talk about the water absorption rate. This is the property indicates how fast the water is moving through the PVA sponge.

Let us recap what we had concluded so far. We know that the water retention is affected by many factors, not only the PVA sponge structure but also the trapped air void in the sponge. Hence, the absorption rate also being affected by the trapped air void.

The PVA sponge water’s absorption rate is affecting by sponge structure, and other factors.

The Absorption Rate

In this experiment, we tested the water absorption rate on several PVA sponge samples, this include PVA sheet wiper, sponge block form and circular sponge. We started the water absorption data collection from dry stage until fully wet or soak for 1 hour.

Below are some of the findings from the above chart.

• All the 5 samples are having difference absorption rate.
• The absorption rate is highly related to the PVA form pattern or outer structure.
• The thin Wiper Sheet is having the highest absorption rate and it is fully soaked within 3 min.
• The block sponge only achieve 60-80% water retention. Perhaps, we had revealed that this is due to trapped air void in the sponge is affecting the water retention.
• The absorption rate fall between the range of 0.4g-water/min-g ~ 4g-water/min-g.

The Affecting Factors

Besides those micro view which we had discussed in the PVA Sponge Water Retention, such as the pore size and porosity ratio, the sponge appearance also affects the water absorption rate.

Several appearance factors we conclude:

• The sponge outer design. Block form, Circular sponge and Sheet foam design gives difference absorption rate.
• Sponge status. Dry stage is the slowest absorption rate. Perhaps, difference moisture level also affect the absorption rate too!
• Water movement direction. There always a limit between force absorption force vs. gravity force. The vertical water placement definitely being affected by the gravity.

Sponge Moisture Level is affecting

Paper is having the fastest absorption rate whereby PVA sponge is the slower. This is because the water transferring mechanism for 2 materials are difference.

Apart from the structural differences, the moisture level in the PVA sponge also playing an importance role in water transferring speed. We are setting up a simple mechanism to show you the difference of water absorption rate via various moisture content. In order for intuitive comparison, we are using blue colour dye and PVA sheet wiper to illustrate the water absorption rate comparison.

The Water Transfer Rate

Besides the water absorption rate, another parameter we also come across is the transfer speed This is something like how fast the water shall move in the sponge. In the study, we are using the “blue” colour dye together with the PVA sheet form to illustrate the concept. We have the below conclusion:

• The absorption rate with 8x moisture content is higher than 2x moisture contain.
• From the experiment, the colour dye is transferred with the rate between 6cm – 9cm/min

The water absorption rate is an engineering parameter which affected by many factors. The field engineer shall select the PVA sponge base on in-line test result if this is very crucial.

So far, we had discussed the water absorption rate and transferring rate within a sponge. These are the 2 concepts while come to actual practical application. Just a note that the absorption rate shows in this experiment should not be used as a generalize parameter for a PVA sponge.