This article is about sodium polyacrylate.
Sodium polyacrylate
Sodium polyacrylate belongs to superabsorbent polymers with the chemical formula [−CH2−CH(CO2K)−]n.
In functionality, it can absorb hundreds of times its weight of water and then turns to water gel form.
In the safety aspect, it's non-toxic, non-pollutant, and harmless. It's easy to find the MSDS (Material Safety Data Sheet).
Basic info
| Appearance | white powder/particle (turn to transparent crystal after absorbing water) |
| Odor | imperceptible |
| CAS number | 9003-4-7 |
| Function | Absorbing, retaining, or blocking liquid |
| Physical property | Non-toxic, harmless, non-polluting, natural degradation |
| Market price | USD 800-3000 per ton (updated in 2018) |
Mechanism
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.
Tip: Metal ions can deeply reduce or destroy the water-absorbing capacity of sodium polyacrylate.
Production process
Types
There're many types of sodium polyacrylate for different uses, such as:
- starch-based type (which is biodegradable),
- catalyst improved type (for water blocking of cable),
- cation type (for concrete additive),
- *defective type & recycled type (for waste liquid absorption).
Uses
Sodium polyacrylate can
- be used directly;
- be used as the raw material of products.
Here are the details:
1. Be used directly
- for production
water blocking, inflatable rubber, thickening agent, fire-retardant gel, desiccant agent, thermal storage agent.
- for building
concrete protection, anti-foggy agent.
- for environment
waste liquid control, excreta collection.
- other
drilling fluid, collection of tattoo liquid waste, oil-water separation.
2. Be used as a raw material
- product for animals
pet pads, a drown-free water source for feeder insects.
- products for personal care
paper diapers, sanitary napkins, nursing mats, and contact lenses.
- products in home
the ice pack, fragrance carrier, water beads, growing toys, cosmetics, solid waterbed.
- other
cable, urine bag, anti-flood bag, instant snow, waterproof paint.
FAQs about sodium polyacrylate
Can sodium polyacrylate go down the drain?
Yes for sodium polyacrylate gel. It’ll slowly be decomposed into the water, carbon dioxide, and some sodium ions, which will not cause environmental pollution.
tip: Sodium polyacrylate powder has a strong water swelling property. This will cause the toilet to block.
Can you reuse sodium polyacrylate?
Yes. It can be reused indefinitely. But it’s important to avoid direct sunlight and high temperature.
How can I get sodium polyacrylate?
Sodium polyacrylate can be used everywhere. We can easily get it from paper diapers, sanitary towels,s or nursing pads.
How to make sodium polyacrylate?
It’s polymerized by Sodium acrylate (which is made of sodium hydroxide and acrylic acid).
The production process is:
a. sodium hydroxide + acrylic acid -> sodium polyacrylate (semi-finished);
b. sodium polyacrylate (semi-finished) -> drying -> smashing -> sift out -> sodium polyacrylate.
There’re four ways to produce sodium polyacrylate: Copolymer chemistry, Gel polymerization, Solution polymerization, and Suspension polymerization.
Here’s the common process picture for your conference:
As you see, sodium polyacrylate is not a natural product.
tip: there is sodium polyacrylate produced by starch grafting. The manufacturer claims that it is a “natural product” as a gimmick.
In theory, sodium polyacrylate can be applied to all applications that need to absorb water or lock water. But as mentioned before, it cannot be used for agricultural water retention. This will be explained in detail later.
Current application list of sodium polyacrylate
Sodium polyacrylate can absorb a lot of liquid & lock it firmly.
So it can be used in:
paper diapers;
sanitary napkins;
nursing pad.
Sodium polyacrylate becomes a stable gel after absorbing water.
So it can be used in:
ice bag;
hot/cold gel pack;
growing toys;
Fragrance carrier;
Sodium polyacrylate’s hydrogel formed after absorbing water can block water.
So it can be used in:
water blocking tape in cable;
Water swelling sandbag for flood control.
Sodium polyacrylate’s hydrogel can be made in color and into a spherical shape.
So these sodium polyacrylate beads/balls can be used in:
Toy gun bullet;
Transparent vase interior decoration;
Sodium polyacrylate can quickly turn liquid into solid for easy collection and processing.
So it can be used in:
Human or animal feces and urine collection;
Wastewater treatment;
Sodium polyacrylate can be modified in the production process.
So it can be used for some special purposes like:
Artificial snow.
Fire-retardant gel.
Additives for drilling lubricants.
Concrete protection. It can effectively prevent the concrete from drying out during the solidification process.
Some uses that have not been widely used or proven:
Water bed;
Thickening agent;
The drown-free water source for feeder insects.
Is it safe to eat sodium polyacrylate?
It’s safe to eat it.
The pharmaceutical-grade sodium polyacrylate is totally nontoxic. As a safe water gel material, it can be even used in body implants such as artificial vitreum and artificial skin.
For other grade sodium polyacrylates, the only poisonous substance is acrylic acid. Its content is less than 1000 PPM and won’t be harmful when eaten.
But as a highly absorbent material, it would bring stomach discomfort to eat sodium polyacrylate.
Is sodium polyacrylate OK in food?
Although the claim of “food grade sodium polyacrylate” has existed for many years, no manufacturer has claimed to be able to produce it. This may be related to the production process.
Is sodium polyacrylate safe/good for the skin?
Although sodium polyacrylate is not toxic, there’re extremely strict requirements on technical parameters especially used in hygiene products like diapers, sanitary napkins, and nursing pads.
As a manufacturer of hygiene products, it’s necessary to check out the MSDS (Material Safety Data Sheet) of sodium polyacrylate.
As a customer of hygiene products, please try to choose well-known brand products.
note: acrylic acid content is a very important indicator. It may cause skin allergies and rashes when the content exceeds the standard.
Is sodium polyacrylate safe for plants?
Safe but not recommended.
Sodium polyacrylate would be decomposed into Sodium ions which cause soil salinization.
Although the price of sodium polyacrylate is much lower than potassium polyacrylate, it’s whimsical to use it as a water-retaining agent.
List a few reasons why you should NOT use sodium polyacrylate for plants:
As a water-retaining agent, sodium polyacrylate can hardly absorb water underground causing the high ion concentration of soil leachate.
The water gel from sodium polyacrylate is easily melted and photodegraded at a lower temperature (such as 40°C).
Sodium polyacrylate is decomposed into a large number of sodium ions that cannot be absorbed by plants, which leads to increased soil salinization.
Note: different from A, B, which is specially designed for the water-retaining agents, effectively solves the above three problems.
Is sodium polyacrylate toxic to dogs/animals/insects?
Strictly speaking, the answer can be yes only if sodium polyacrylate meets the food-grade standard.
What’s the Ph value?
Generally speaking, sodium polyacrylate is weakly acidic because it has very little acrylic residue. (Sodium polyacrylate is formed by the polymerization reaction of acrylic acid and sodium hydroxide. )
What’s the melting point?
It’s 150℃.
In addition, after sodium polyacrylate absorbs water and becomes a hydrogel, it will be easily melted and photodegraded at a lower temperature (such as 40°C). This is one of the reasons why sodium polyacrylate cannot be used as a water-retaining agent for agriculture and forestry.
What is the use of sodium polyacrylate?
It can be used as:
a. water-retaining agent (for plants);
b. water-absorbent material (for diapers);
c. expanding material (for inflatable toys);
d. thickener (for cosmetics);
e. water blocking material (inflatable sandbag);
f. cooling storage (ice pad).
What’s water absorption?
As the strongest water-absorbing material at present, sodium polyacrylate can absorb up to several thousand times its own weight of pure water.
In addition, whether the water is pure or not directly affects the absorption of sodium polyacrylate. If salt is added to the water, the water absorption will be greatly reduced. The concentration of water ions in the soil is extremely high, and the water absorption of sodium polyacrylate is greatly reduced — This is one reason why it is not suitable for use as a water-retaining agent.
Where to find/get sodium polyacrylate at home?
As I said, you can easily find sodium polyacrylate in sanitary napkins or paper diapers.
Why does sodium polyacrylate absorb water?/how does sodium polyacrylate work?
You may have been wondering how sodium polyacrylate works. In fact, the entire water absorption process has undergone complex physical and chemical reactions.
Simply speaking, there are network molecular chains in the molecular structure of A. Its electrolysis occurs immediately after encountering water and dissociates into positively and negatively charged ions. The positively and negatively charged ions have a strong affinity with water. Therefore, it has strong water absorption and water retention capabilities.
