Polyacrylic acid
[CAS# 9003-01-4]

Identification

• Classification: Catalysts and additives >> Polymer
• Name: Polyacrylic acid
• Synonyms: 2-Propenoic acid homopolymer; Acrylic acid polymer; Poly(acrylic acid); Propenoic acid polymer; PAA
• Molecular Formula: (C₃H₄O₂)_n
• Molecular Weight: ~450000
• CAS Registry Number: 9003-01-4
• EC Number: 618-347-7
• SMILES: C=CC(=O)O

Properties

• Density: 1.09 (30% aq.)

Safety Data

• Hazard Symbols: GHS07;GHS08 Danger
• Risk Statements: H315-H319-H335-H340-H350
• Safety Statements: P203-P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P318-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Carcinogenicity	Carc.	1A	H350
Germ cell mutagenicity	Muta.	1B	H340
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Acute toxicity	Acute Tox.	4	H332
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	4	H302
Skin corrosion	Skin Corr.	1B	H314
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Skin corrosion	Skin Corr.	1A	H314
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Skin corrosion	Skin Corr.	1	H314
Acute toxicity	Acute Tox.	4	H312
Flammable liquids	Flam. Liq.	3	H226

Discovery and Applications

Polyacrylic acid (PAA) is a synthetic polymer made from the polymerization of acrylic acid. It is a versatile material with a wide range of applications due to its water-absorbing and gel-forming properties. The discovery of polyacrylic acid dates back to the early 20th century during the development of synthetic polymers. As research into acrylic compounds progressed, polyacrylic acid emerged as one of the key materials for applications requiring water solubility and thickening properties. Its unique ability to absorb and retain water has made it a valuable polymer in industries such as pharmaceuticals, cosmetics, and water treatment.

The initial exploration of acrylic acid and its derivatives began in the 1900s, but it was in the mid-20th century that the polymerization process to create polyacrylic acid was optimized. PAA is formed by the free-radical polymerization of acrylic acid monomers, resulting in a polymer chain with carboxyl groups. These carboxyl groups, when exposed to water, ionize and allow the polymer to form hydrogels, a feature that is crucial for its many applications.

One of the most important uses of polyacrylic acid is in the production of superabsorbent polymers (SAPs). These materials can absorb and retain large amounts of water relative to their own mass, making them ideal for products like diapers, adult incontinence products, and feminine hygiene products. The carboxyl groups in PAA attract water molecules and swell, forming a gel that traps the liquid. This property is essential in personal care products, where moisture absorption and retention are critical for product performance.

Polyacrylic acid is also widely used in the pharmaceutical industry, particularly in drug delivery systems. Its biocompatibility and ability to form hydrogels make it an excellent material for controlled-release formulations. PAA-based hydrogels can encapsulate active pharmaceutical ingredients and release them gradually over time, ensuring a steady supply of the drug in the body. This controlled release mechanism is beneficial in improving the efficacy of medications, reducing dosing frequency, and enhancing patient compliance.

In the water treatment industry, polyacrylic acid is used as a dispersant and scale inhibitor. PAA prevents the formation of scale, which can accumulate in water pipes, boilers, and cooling systems, causing inefficiency and damage. By adsorbing onto the surface of particles, PAA prevents them from agglomerating and settling, keeping them suspended in the water. This property is particularly important in industrial water systems where the prevention of mineral deposits is essential for maintaining operational efficiency.

Polyacrylic acid also finds applications in the cosmetic industry, where it is used as a thickening agent, film former, and stabilizer in lotions, creams, and gels. Its ability to adjust the viscosity of formulations makes it a valuable ingredient in creating products with the desired texture and consistency. Additionally, PAA's compatibility with a wide range of ingredients, including oils and emulsifiers, allows formulators to create stable emulsions and suspensions.

Another key application of polyacrylic acid is in the production of adhesives and coatings. The polymer’s ability to form films and bond with various surfaces makes it suitable for pressure-sensitive adhesives, which are used in tapes, labels, and medical dressings. In coatings, PAA is employed to improve the durability and water resistance of paints and varnishes, enhancing the performance and longevity of the finished products.

Research on polyacrylic acid continues, with a focus on improving its properties and expanding its applications. Modifications of PAA, such as copolymerization with other monomers, have led to the development of polymers with tailored characteristics for specific uses. These advancements are helping to broaden the range of industries that can benefit from PAA-based materials.

In summary, the discovery and development of polyacrylic acid have had a significant impact on various industries. Its ability to absorb water, form hydrogels, and stabilize formulations has made it an essential material in products ranging from superabsorbents to pharmaceuticals. As research into its properties and applications continues, polyacrylic acid is expected to play an even larger role in both industrial and consumer products.

References

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