Superabsorbent polymer (SAP)

*This page is about superabsorbent polymer, slush powder, potassium polyacrylate, sodium polyacrylate, SAP.

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Brief introduction

The origins of superabsorbent polymer chemistry trace back to the early 1960s when the U.S. Department of Agriculture developed the first superabsorbent polymer materials.

As a function polymer material, superabsorbent polymer (SAP) has a strong water-absorbing ability.

It can absorb hundreds of times its weight and lock water firmly.

After absorbing, SAP powder (or granule) will turn into water gel.

According to different usage, there are many types of superabsorbent polymers.

What is SAP

There are many types of SAPs such as sodium polyacrylate, potassium polyacrylate, etc.

SAP (Superabsorbent Polymer) is a functional polymer with higher water absorption and superior water retention capability.

It :

Absorb plenty of water (or other inorganic solution),

Lock water and

Become water gel form after absorbing.

The advantageous aspect of using SAP is that it is:

  • Non-Toxic,
  • Non-pollutant, and
  • Harmless in every aspect.

Tips: Its most beneficial property lies in the fact that it absorbs liquids equivalent to several hundred times of it body mass and transforms it into a Gel; that is why it is able to retain or stop the water.

How does SAP work?

It consists of a set of polymeric chains that are parallel to each other and regularly linked to each other by cross-linking agents, thus forming a network.

When water comes into contact with one of these chains, it is drawn into the molecule by osmosis. Water rapidly migrates into the interior of the polymer network where it is stored.

Quality grade


SAP’s main compositions are sodium polyacrylate or potassium polyacrylate.

The grades of SAP as follows,

Improved SAP – Improved on some side like:

  • Starch-based SAP – The biodegradable type SAP;
  • Minerals based SAP (for plants) – Available in soil for years;
  • SAP with improved catalyst – High expansion ability (for water blocking of cable);
  • Cation type SAP – concrete additive.

Common SAP

  • Potassium polyacrylate – mainly used in agriculture as a water retaining agent;
  • Sodium polyacrylate – widely used in industrial production such as Paper diapers, Sanitary napkins, Ice bags, Air fresher, Expanding rubber, etc.

Defective SAP

  • Recycled SAP: the SAP was used and recycled;
  • Burnt SAP: the SAP was produced in over-temperature.

Uses of SAP

For plants

As the type of superabsorbent polymer for plants, it is a unique superabsorbent granule, which acts to provide increased moisture availability to plants.

Important indicator as follows,

Absorbing capacity in soil;

Granular size;

The photolysis resistance;

Period of validity.

For hygiene products

With its awesome properties of liquid absorption and locking it has found very useful application in products prone to moisture like:


Sanitary napkins,

Nursing pads and

Pet pads.

Important indicator as follows,

Absorbent rate;

Absorption under pressure and retention capacity after centrifugation;

Liquid Permeability;

Residual Monomer.

For miscellaneous industrial products

With each passing day, SAP is being employed in more and more industries and applications due to its increasing popularity and efficiency in water deterrence.

Some applications as follows,

For waterproofing cables

SAP is a highly coveted product as far as the manufacture of water-proof tapes and ointments for all sorts of cables are concerned; even, optical fiber cables use SAP. The extent and the speed of absorption are quite high and so are the overall inflation rate and its quantum of inflation upon encountering water.

Important indicator as follows,

Expansion height;

Granular size.

In Ice Bags

Freshwater is directed at the individual sheets of ice packs to activate them; Superabsorbent Polymer instantly starts absorbing the water and converting it to a Gel by placing them under fresh tap water; in about 20 minutes time it is seen to soak up enough water to form small cushion-shaped Ice Cubes. They are now ready for use by placing them in the freezer.

Important indicator as follows,

Hydration time;


Granular size.

Inflatable Anti-Flood Sandbags

SAP has this unique application in Disaster Management where it is used in preparing sandbags which, when coming in contact with water, quickly absorb it and expand to form a barrier to the advancing water. Though we call them Sandbags, they actually do not contain any sand; they are so-called because that is how they have been known traditionally.

These Sand-less Sandbags are quite small in size and light in weight initially but they soak up the water to assume a solid shape. They are much easier to store and transport and take up lesser space when unused.

Important indicator as follows,

Absorbent rate;

The photolysis resistance.

Concrete Protection

Its permeability happens to be quite low; it totally shuts out the water content,

Due to its fibrous texture, it can be stored to form a vertical barrier,

Since it is an effective sealant, it finds application in Cement-based items.

Other Applications

It finds extensive usage in a number of species of products due to its amazing properties; some of them may be listed here:

  • As an additive for functional coating in many specific applications,
  • As an additive in Air fresheners,
  • For expanding rubber requirements,
  • Absorption of wastewaters from industries,
  • In the mining industry for disaster management and normal seepages,
  • In certain cosmetics.

Due to its awesome capacity to act on moisture, SAP (Superabsorbent Polymer) is finding newer purposes for which it is being employed.

  References: Sodium polyacrylate: Sum up all knowledge about it

 References: Potassium polyacrylate: Sum up all knowledge about it