Teach You To Know Super Absorbent Polymer Powder

Super absorbent polymer powder is a new type of functional polymer material, which is widely used and has broad market prospects. This article introduces its structural characteristics, water absorption mechanism, characteristics and classification to help you understand this new type of polymer material.

1. Structural characteristics and water absorption mechanism of super absorbent polymer powder

 (1) Structural features

super absorbent polymer powder is prepared by cross linking and hydrolysis technology on the basis of water soluble polymer. It has the structure and performance characteristics of low cross linking degree, high swelling rate, and water insolubility. In terms of chemical structure, the main chain or side chain of super absorbent polymer powder

 contains hydrophilic genes such as hydroxyl, amide, carboxyl, sulfonic acid, etc.; in terms of physical structure, it is a three dimensional network with low cross linking degree.

(2) Water absorption mechanism

super absorbent polymer powder absorbs water in several stages. In the initial stage, the water absorption rate is very slow, because the water absorption at this time is achieved by capillary adsorption and dispersion, and then the water molecules interact with the hydrophilic groups of the resin through hydrogen bonds to dissociate, and the anions are fixed in the polymer chain. , the cations can move freely. With the further dissociation of the hydrophilic groups, the number of anions increases, and the electrostatic repulsion between the ions expands the resin network; at the same time, in order to maintain electrical neutrality, the cations cannot diffuse to the external solvent, resulting in an increase in the concentration of cations in the resin network. , so the osmotic pressure is generated inside and outside the network, and the water further penetrates. With the increase of water absorption, the osmotic pressure difference inside and outside the network tends to zero; while the network expands, its elastic contraction force also increases, gradually offsetting the electrostatic repulsion of anions, and finally reaching a water absorption balance.

2. Features of super absorbent polymer powder

(1) High water absorption

Commonly used water absorbing materials such as sponges have a water absorbing capacity of about 20 times their own weight, while starch based resins can absorb hundreds of thousands of times their own weight in water.

(2) Good water retention

After the ordinary water absorbing material absorbs water, it is easy to release water under pressure, but the super absorbent polymer powder is pressurized, and the water is not easy to be released from the resin, that is to say, it still has good water retention under external pressure.

(3) Good thermal stability

Different super absorbent polymer powder have different thermal stability. Starch is heated at 150 degrees for 1h, and begins to turn black, and the water absorption capacity is reduced.

If the super absorbent polymer powder

 is stored in a sealed container, it can be stored for 3-4 hours, and its water absorption capacity remains unchanged.

(4) Thickening property

After absorbing water, it is water coagulated, with a higher viscosity than ordinary water soluble ones, and has obvious thickening effect.

3. Classification of super absorbent polymer powder

(1) Starch

Starch is a kind of polyhydroxy natural compound with a wide range of raw materials, many kinds and low price. The monomers for graft copolymerization with starch are mainly hydrophilic and vinyl monomers which become hydrophilic after hydrolysis. At present, free radical graft copolymerization is usually used to synthesize super absorbent polymer powder.

(2) Synthetic resin system

There are many kinds of it, and with the deepening of research, there are more and more. There are mainly acrylics, polypropylene alcohols, etc., among which acrylics are the most important.

(3) Fiber series

Due to the emergence of starch based super absorbent polymer powder, people have thought of using cellulose as a raw material to prepare SAP powder. Fiber raw materials have a wide range of sources and can react with a variety of low molecules, which is an aspect of the development of new polymer materials in the past decade.

(4) Organic inorganic composite super absorbent polymer powder.

In recent years, the development of SAP powder has developed rapidly in my country. After years of efforts, my country has developed a series of new organic inorganic composite high efficiency water absorbent resins, which have achieved low cost salt alkali resistance and multi functionality. In this paper, the structural characteristics, water absorption mechanism, characteristics and classification are explained to help you understand this new type of polymer material.