Acrylamide-Acrylic Acid Copolymer (CAS#9003-06-9) – Anionic Flocculant PAM

1. Properties:

• Appearance and Physical Form: Acrylamide-acrylic acid copolymer is supplied as a white to off-white free‑flowing powder, granular solid, white beads, or as an aqueous solution (10–50% active). The product is odorless and exhibits high purity (≥90% industrial grade; ≥98% research grade).
• Solubility: The copolymer is readily soluble in both cold and hot water, forming highly viscous solutions even at low concentrations (0.05–0.5%). It is insoluble in most organic solvents including ethanol, acetone, hydrocarbons, and non‑polar solvents.
• Chemical Properties: Acrylamide-acrylic acid copolymer is an anionic water‑soluble polymer synthesized by free‑radical copolymerization of acrylamide (AM) and acrylic acid (AA) monomers. The polymer backbone contains both amide (-CONH₂) and carboxyl (-COOH) functional groups. The carboxyl groups can be deprotonated to carboxylate anions (-COO⁻) as pH increases, giving the polymer pH-responsive behavior. The ratio of acrylic acid to acrylamide (typically 5–30% carboxyl content) determines the anionic charge density, which influences flocculation performance, viscosity, and electrolyte tolerance. The high molecular weight (typically 200,000 to over 15 million g/mol) allows the polymer chains to entangle, forming bridges between suspended particles—a mechanism known as polymer bridging—and adsorbing onto particle surfaces via charge interactions, enabling efficient particle aggregation and sedimentation.

2. Applications:

Water & Wastewater Treatment (Primary):

• Wastewater Treatment & Sludge Dewatering: As a high‑efficiency flocculant, PAM binds fine suspended particles, organic matter, and solids, forming larger flocs that settle rapidly under gravity. It is widely used in municipal sewage treatment plants, industrial effluent treatment, sludge thickening and dewatering operations (centrifuges, belt presses, filter presses). The polymer improves solid-liquid separation, reduces sludge volume, and produces clearer effluent meeting discharge permit requirements.
• Drinking Water Purification: PAM is used as a coagulant aid in potable water treatment to remove turbidity, color, and colloidal impurities.
• Industrial Process Water: Applied in cooling towers, boiler feed water treatment, and recycling loops to clarify water and reduce suspended solids.

Oil & Gas Industry – Enhanced Oil Recovery (EOR):

• Polymer Flooding: HPAM is the polymer of choice for enhanced oil recovery in mature reservoirs. It increases the viscosity of the water phase (up to 5–30 times), improving the mobility ratio between injected water and reservoir oil, which enhances sweep efficiency and oil displacement. The polymer maintains high viscosity even at low concentrations and exhibits good salt resistance, making it suitable for brine‑based injection systems. PAM reduces water cut and improves tertiary oil recovery rates.
• Drilling Fluids: Functions as a viscosifier, shale inhibitor, and clay extender in water‑based drilling muds. It reduces fluid loss, controls wellbore stability, and improves hole cleaning capacity. PHPA (partially hydrolyzed polyacrylamide) effectively stabilizes reactive shales and extends bentonite clay performance in low‑solids mud systems.
• Fracturing Fluids: HPAM is used as a friction reducer and viscosifier in hydraulic fracturing operations for unconventional oil and gas reservoirs, improving proppant transport and fracture conductivity.
• Workover & Completion Fluids: Rheology modifier for brine‑based completion and workover operations.

Paper & Pulp Industry:

• Retention Aid: PAM increases fiber and filler retention on the paper machine wire, reducing raw material loss and improving paper quality. It functions by forming large flocs with fine particles, which are retained more efficiently during sheet formation.
• Drainage Aid: Improves dewatering rate on the paper machine wire, increasing production speed, reducing energy consumption for drying, and lowering manufacturing costs.
• Dry‑Strength Resin: Enhances paper strength properties without reducing drainage performance. Cationic or amphoteric PAM grades are often preferred for strength applications. PAM copolymers used as dry-strength resins typically have molecular masses up to 1 million g/mole.
• Dispersant: Prevents fiber and filler agglomeration, improving sheet uniformity and paper formation.
• Wastewater Treatment: PAM is used as a flocculant for primary and secondary clarifiers in paper mill effluent treatment, reducing suspended solids and BOD loads before discharge.

Textile Industry:

• Warp Sizing Agent: PAM is used as a sizing agent for cotton, polyester, and synthetic yarns. It improves yarn strength, reduces hairiness and breakage during weaving, and is easily removed during desizing operations. PAM is widely used in many textile applications including sizing and printing.
• Printing Paste Thickener: Provides precise color definition, uniform dye transfer, sharp pattern edges, and easy wash-off after printing without affecting fabric hand feel.
• Fabric Finishing: Used as a finishing agent to improve fabric feel, stiffness, and antistatic properties.

Mining & Mineral Processing:

• Tailings Treatment & Thickening: PAM accelerates solids settling in mineral tailings ponds, improves thickener underflow density, and clarifies overflow water for recycling. It reduces tailings volume and improves water recovery.
• Froth Flotation: Used as a flocculant and settling aid in mineral concentration circuits for copper, gold, iron ore, and coal processing. In mining applications, PAM is effective for removing inorganic suspended solids, with the most common formulations containing 5–30% carboxyl content.
• Coal Washing: Applied as a flocculant in coal preparation plants to clarify process water and recover fine coal particles.

Personal Care & Cosmetics:

• Rheology Modifier & Thickener: PAM functions as a viscosity builder, stabilizer, and texture enhancer in creams, lotions, gels, and hair styling products, providing smooth, non‑greasy feel, shear‑thinning behavior for easy application, and enhanced formulation stability.
• Emulsion Stabilizer: Prevents oil‑water separation in cosmetic emulsions, improving shelf life and product appearance.
• Film Former: Forms flexible, transparent films on skin and hair, providing hold, protection, and conditioning benefits.

Industrial Adhesives & Binders:

• Adhesive Thickener and Rheology Modifier: PAM is used as a water‑soluble polymer additive in industrial adhesive formulations (paper laminating, packaging, wood glues), improving viscosity control, increasing bond strength, and enhancing open time and water resistance.
• Binder for Pigments and Coatings: Used as a binder for pigments, fillers, and coatings in construction materials, ceramics, and refractory products.

Other Industrial Applications:

• Agriculture: PAM is used as a soil conditioner to improve water infiltration, reduce soil erosion, enhance moisture retention, and minimize nutrient runoff in irrigation furrows. High molecular weight PAM (12–15 million) is effective for stabilizing soil aggregates.
• Biomedical Hydrogels: Forms hydrophilic gels for controlled drug release, tissue engineering scaffolds, and wound dressings.
• Detergent Processing Aids: Used as a processing aid and anti‑redeposition agent in laundry detergent formulations.

3. Preparation Method:

• Laboratory Method: The copolymer can be prepared by mixing acrylic acid and acrylamide in a 2:1 molar ratio in deionized water, adding 7% ammonium persulfate solution as the free‑radical initiator, heating to 60°C, and reacting for 3 hours under stirring. The resulting polymer solution can be used as‑is or isolated by precipitation, drying, and milling.
• Industrial Process: Industrial production of high‑quality acrylamide-acrylic acid copolymer follows a solution or inverse‑emulsion polymerization route: (1) Monomer Preparation: Acrylamide (AM) and acrylic acid (AA) monomers are dissolved in deionized water at controlled ratios (typically 70:30 to 95:5 AM:AA mole ratio). (2) Initiation: A free‑radical initiator (ammonium persulfate, potassium persulfate, or AIBN) is added under inert atmosphere (nitrogen purge). (3) Polymerization: The reaction proceeds at controlled temperature (40–80°C) for 2–6 hours, yielding a highly viscous polymer solution. (4) Neutralization (Optional): The carboxyl groups may be partially or fully neutralized with sodium hydroxide to produce the sodium acrylate form for enhanced water solubility and ionic character. (5) Isolation & Drying: The polymer can be used as an aqueous solution (10–50% active) or isolated by precipitation with a non‑solvent (acetone, methanol), followed by drying, milling, and sieving to produce powder/granules with controlled particle size distribution. Key quality parameters include molecular weight, carboxyl content, residual acrylamide monomer (<1 ppm for food‑contact grades), solution viscosity, charge density, and moisture content.

4. Safety Information:

• Hazard Classification: Under GHS/CLP Regulation (EC) No 1272/2008, acrylamide-acrylic acid copolymer is generally classified as non‑hazardous or of very low hazard, with most industrial grades requiring no hazard label. However, the product may contain residual acrylamide monomer (<1 ppm for specialized grades; higher in technical grades), which is classified as a suspected human carcinogen and Category 2 mutagen. Commercial PAM products typically carry hazard statement H302 (Harmful if swallowed) in some classifications, along with H315 (Causes skin irritation), H317 (May cause an allergic skin reaction), and H335 (May cause respiratory irritation). Hazard pictograms: GHS07 (for certain dusty grades). Signal word: Warning. Not classified as flammable, explosive, or environmentally hazardous under standard criteria.
• Health Hazards:
  • Inhalation: Inhalation of airborne PAM dust may cause mild to moderate respiratory tract irritation, coughing, sneezing, or throat discomfort in sensitive individuals.
  • Skin Contact: Generally non‑irritating to intact skin; may cause mild mechanical irritation due to powder abrasion. Prolonged or repeated exposure may lead to dermatitis in sensitive individuals.
  • Eye Contact: Fine dust particles may cause mechanical irritation; contact with solution may cause mild transient irritation.
  • Ingestion: Low acute toxicity (LD₅₀ oral > 2000 mg/kg in rats). Ingestion of large quantities may cause gastrointestinal discomfort.
  • Acrylamide Monomer Residue: Residual acrylamide monomer is a neurotoxin and potential carcinogen. Industrial PAM is polymerized to <0.05% residual monomer; food‑contact and potable‑water grades are processed to <1 ppm.
• First Aid Measures:
  • Eye Contact: Rinse cautiously with plenty of water for at least 15 minutes, removing contact lenses if present. Seek medical attention if irritation persists.
  • Skin Contact: Wash skin with plenty of soap and water. Remove contaminated clothing. If irritation develops, seek medical advice.
  • Inhalation: Move person to fresh air. Keep at rest in a position comfortable for breathing. If symptoms (coughing, throat irritation) persist, seek medical advice.
  • Ingestion: Rinse mouth immediately. Do NOT induce vomiting. Drink water to dilute if conscious. Seek immediate medical attention if large amount is ingested or if symptoms develop.
• Fire & Explosion Hazards: PAM is not combustible but may burn if involved in a fire. Accumulated settled dust may form explosive concentrations in air when disturbed and dispersed, as with any organic dust. In case of fire, use water spray, foam, dry powder, or CO₂ as extinguishing media appropriate for the surrounding fire. Thermal decomposition may produce irritating and toxic fumes including carbon monoxide (CO), carbon dioxide (CO₂), and nitrogen oxides (NOₓ).
• Environmental Precautions: Polyacrylamide is not readily biodegradable due to its synthetic polymer backbone. However, it is not classified as hazardous to the aquatic environment under most regulatory schemes. Avoid direct release into natural water bodies, drains, or soil in large quantities. Comply with local environmental regulations for disposal. Degrades slowly via mechanical shearing and photodegradation in aqueous environments.
• Personal Protective Equipment (PPE):
  • Respiratory protection: Use a dust mask (N95 or P2 respirator) if airborne dust concentrations are present or when handling powder forms in poorly ventilated areas.
  • Eye protection: Safety goggles or dust‑resistant safety glasses to prevent mechanical eye irritation.
  • Skin protection: Chemical‑resistant gloves (nitrile) and protective clothing to minimize skin contact and dust exposure.
  • General hygiene: Wash hands thoroughly after handling. Do not eat, drink, or smoke in work areas. Minimize dust generation and avoid breathing dust.
• Storage & Stability: Store in tightly closed, moisture‑proof containers in a cool, dry, well‑ventilated area away from direct sunlight, heat sources, and strong oxidizing agents. PAM is hygroscopic; exposure to atmospheric moisture leads to caking, lump formation, and reduced dissolution rate. Under recommended storage conditions (room temperature, low humidity), shelf life is 12–24 months from date of manufacture in sealed original containers. Some solution grades require refrigerated storage (4°C) to prevent viscosity loss and microbial degradation.
• Regulatory Compliance: Acrylamide-acrylic acid copolymer (CAS#9003-06-9) is listed on EINECS (231-545-4 for PAM; the copolymer may fall under 500-002-2), TSCA, DSL, AICS, NZIoC, ENCS, KECI, and other regional chemical inventories. Food‑contact grades and potable‑water treatment grades must comply with FDA 21 CFR § 173.315, EU Regulation (EC) No 2019/1009 for fertilising products, and NSF/ANSI Standard 60 for drinking water treatment chemicals. Residual acrylamide monomer limits are strictly regulated: typically <1 ppm for potable water treatment and food contact applications. Always consult the Safety Data Sheet (SDS) and local regulations for complete safety, environmental, and regulatory information specific to each product grade and application jurisdiction.