| HS Code | |
| Product Name | Acrylic Acid |
| Chemical Formula | C3H4O2 |
| Molecular Weight | 72.06 g/mol |
| Cas Number | 79-10-7 |
| Einecs Number | 201-177-9 |
| Appearance | Colorless liquid |
| Odor | Acrid, pungent |
| Melting Point | 13 °C |
| Boiling Point | 141 °C |
| Flash Point | 50 °C (closed cup) |
| Density | 1.051 g/cm³ at 20 °C |
| Vapor Pressure | 4.1 mmHg at 20 °C |
| Solubility | Miscible with water |
| Pka | 4.25 |
| Viscosity | 1.3 mPa·s at 25 °C |
| Un Number | 2218 |
| Hazard Class | 8 (Corrosive) |
| Packing Group | II |
As an accredited Acrylic Acid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Acrylic Acid is typically packaged in 200 kg lined steel drums or 1,000 kg stainless steel IBCs, with polymerization inhibitor. |
| Container Loading (20′ FCL) | 20′ FCL loading of inhibited Acrylic Acid, UN 2218, Class 8 corrosive, securely stowed, labeled, and documented per IMDG rules. |
| Shipping | Acrylic acid (UN 2218, stabilized) ships as a Class 8 corrosive liquid with Class 3 flammable subsidiary, Packing Group II. It requires polymerization inhibitor, temperature control, and compatible stainless steel or lined containers. Placard, label, and document as hazardous cargo; avoid heat, oxidizers, and contamination. |
| Storage | Store acrylic acid in a cool, dry, well-ventilated, fire-resistant area, ideally at 15–25°C, away from heat, sparks, flames, oxidizers, bases, and polymerization initiators. Keep containers tightly closed, upright, labeled, and corrosion-resistant. Maintain dissolved oxygen and inhibitor levels; avoid inert blanketing. Use secondary containment, grounding, and spill controls. Protect from freezing, direct sunlight, and incompatible materials. Regularly inspect for leaks and deterioration. |
| Shelf Life | Acrylic acid shelf life is typically six months when stored cool, dark, inhibited, and oxygenated; otherwise it may polymerize. |
Partially neutralized polyacrylic acid superabsorbent polymer production begins with dilution of glacial acrylic acid to 25–45 wt% in deionized water, followed by neutralization of 65–75 mol% of carboxylic acid groups with sodium hydroxide. Trimethylolpropane triacrylate is metered at 0.02–0.4 wt% of acrylic acid mass as internal crosslinker, and the redox pair potassium persulfate and sodium metabisulfite is charged at 0.05–0.20 wt% and 0.04–0.10 wt% respectively. The feed is chilled to 4 ± 2 °C before entering a continuous polymerization belt because the adiabatic exotherm routinely reaches 96–104 °C within 10–30 min. On production-scale lines, insufficient chilling causes localized gel popcorning and uneven particle morphology, while excessive neutralization above 75 mol% increases the gel block temperature and produces a hard, low-absorbency crumb that later resists milling. After polymerization, the hydrogel is crumbed to 2–6 mm particles, dried in a through-circulation belt dryer at 160–180 °C for 20–40 min, milled, and sieved to 100–850 µm. Surface crosslinking is then performed with ethylene glycol diglycidyl ether or propylene carbonate at 0.05–0.15 wt% of dry powder in a continuous paddle mixer at 150–170 °C. The resulting polyacrylate superabsorbent is incorporated into baby diaper cores, adult incontinence pads, feminine hygiene layers, and water-blocking tape for cables.
| Parameter | Test method | Production control range | Equipment or observation |
|---|---|---|---|
| Free swell capacity in 0.9 wt% NaCl | ISO 17190-4:2001 | 45–60 g/g | Adjusted through surface crosslinker dosage |
| Centrifuge retention capacity | ISO 17190-4:2001 | 28–34 g/g | Controlled by internal crosslinker and neutralization ratio |
| Residual acrylic acid monomer | ISO 17190-2:2001 | ≤400 µg/g for infant hygiene | HPLC-UV after 0.9 g/100 mL NaCl extraction |
| Saline flow conductivity | ISO 17190-6:2001 | 10–40 × 10⁻⁷ cm³·s/g | Gel bed permeability under 0.3 psi load |
The critical processing window for surface crosslinking is narrow: residence time below 20 min leaves insufficient reaction at the particle periphery, while time above 40 min produces overdried particle surfaces and reduced gel-bed permeability. Residual monomer limits under ISO 17190-2:2001 are low enough that any interruption in the neutralization stage or inadequate post-polymerization stripping results in failed batch release for hygiene-grade material.
In 10 m³ semibatch emulsion polymerization for architectural latex binders, acrylic acid is not the backbone monomer but a functional acid monomer charged at 0.8–2.5 wt% of total monomer mass to control colloidal stability, mechanical stability, and adhesion to alkaline mineral substrates. The pre-emulsion is prepared with deionized water, anionic surfactant at 1.0–2.0 wt% of total monomers, and a monomer mixture of butyl acrylate, methyl methacrylate, and the specified acrylic acid fraction. Ammonium persulfate initiator is introduced at 0.3–0.5 wt% with sodium metabisulfite as a redox co-agent. The monomer feed is delivered over 3.5–4.5 h into a reactor held at 80 ± 2 °C, followed by a chase polymerization at 85 °C for 60 min. Under these conditions, acrylic acid addition above 3.5 wt% generates water-soluble oligomers that increase reactor wall fouling on the agitation shaft and raise coarse grit formation, which is removed through a 250 µm basket strainer before letdown. The final latex is adjusted to pH 8.0–9.0 with ammonia and formulated with binder solids at 18–28 wt% in finished paint, coalescent at 2.0–4.0 wt% of binder solids, and associative thickener at 0.3–1.0 wt%. Wet-scrub resistance is evaluated under ISO 11998:2006 and ASTM D2486-17, while volatile organic compound content is controlled against EU Directive 2004/42/EC Phase II limits for waterborne decorative paints. The terminal forms produced from this route include interior and exterior flat, satin, and semigloss paints, elastomeric roof coatings, and alkali-resistant masonry primers.
Acrylic acid in emulsion pressure-sensitive adhesive polymerization is limited to 1.0–5.0 wt% of total monomers in a butyl acrylate/2-ethylhexyl acrylate copolymer backbone. Chain transfer agent tert-dodecyl mercaptan is present at 0.02–0.08 wt% to control gel fraction and molecular weight distribution. The reaction is run in a 6 m³ jacketed glass-lined reactor at 78–84 °C, with the pre-emulsion feed split so that acrylic acid can be front-loaded, uniformly distributed, or back-loaded. Production records show that front-loading acrylic acid in the first 30% of monomer feed raises gel content and static shear resistance but lowers loop tack; back-loading in the final 20% improves adhesion to stainless steel and polar substrates but increases edge curl on coated film. After polymerization the latex is adjusted to pH 7.0–7.8 with ammonia and coated onto release liner by reverse roll or slot-die at 20–40 g/m² dry coat weight, then dried at 90–110 °C for 3–5 min. Peel adhesion is measured under ISO 29862:2018, static shear under ISO 29863:2018 and ASTM D3654/D3654M-06(2020). Terminal products include permanent paper labels, clear overlaminate films, high-performance masking tapes, and low-peel protective films for electronic display surfaces.
A 5 m³ jacketed stainless steel reactor operating at 60–70 °C is used for aqueous solution copolymerization of acrylic acid and isoprenyl oxy polyethylene glycol macromonomer in polycarboxylate ether superplasticizer production. The acrylic acid-to-macromonomer molar ratio is held between 2.8 and 4.2, with potassium persulfate initiator at 0.6–1.2 wt% on total monomer and mercaptopropionic acid chain transfer agent at 0.4–0.8 wt%. The reaction is fed over 3.5–5.0 h, and the anchor impeller speed is maintained at 60 rpm. Temperature excursions above 75 °C are a known production failure mode because they widen the molecular weight distribution and produce a high molecular weight tail that degrades slump retention in concrete. After polymerization, the carboxylate groups are neutralized with sodium hydroxide to pH 5.0–6.5, and the resulting polymer solution is standardized to 40–50 wt% solids. Final dosage in concrete is 0.15–0.35 wt% by cement mass. The product is qualified under ASTM C494/C494M-19 Type A and Type F and EN 934-2:2009+A1:2012 Tables 3.1 and 3.2. The terminal concrete types include ready-mix concrete, precast elements, self-consolidating concrete, and high-strength structural concrete.
Ceramic tile body slips are dispersed with sodium polyacrylate derived from acrylic acid, with a molecular weight of 2,000–5,000 g/mol and liquid solids of 40–45 wt%. The addition rate is 0.15–0.45 wt% on dry solids of the mill charge, and slip solids are maintained at 68–72 wt%. Production ball milling uses high-alumina grinding media to a sieve residue of 0.5–1.0% on a 45 µm screen. Slip apparent viscosity is measured at 100 s⁻¹ under ISO 3219:1994, and particle size distribution is verified by laser diffraction under ISO 13320:2020. After 72 h of aging, slips above 0.6 wt% dispersant often display viscosity rebound when hard water calcium exceeds 200 mg/L as CaCO₃, requiring the addition of a chelating agent before dispersant loading is adjusted. Conversely, insufficient dispersant causes pump cavitation in the spray dryer feed line. The spray dryer is operated at an inlet temperature of 480–520 °C and outlet of 110–130 °C, with atomizer wheel speed at 12,000–18,000 rpm. Fired tile performance is controlled under ISO 13006:2018. Terminal products are porcelain stoneware tiles, glazed wall tiles, sanitaryware bodies, and technical ceramic components.
Foam application of self-crosslinking acrylic emulsion binders for carded nonwoven substrates is constrained by the wet tensile requirement of ISO 9073-3:2023 and thickness retention under ISO 9073-2:1995. Acrylic acid is incorporated into the binder polymer at 1.0–4.0 wt% of total monomer to generate carboxyl functionality for adhesion to cellulosic and synthetic fiber blends. Binder add-on is controlled at 15–25 wt% dry fiber, with foam density of 150–300 g/L produced on a foaming unit feeding a stenter frame. Curing is performed at 140–170 °C for 1–3 min. At curing temperatures below 130 °C, wet tensile strength fails the ISO 9073-3:2023 specification; above 180 °C, yellowing of cellulosic fiber and embrittlement of the binder film are observed. Rub fastness is evaluated under ISO 105-X12:2016, and hygiene-grade binders are audited for restricted substances under OEKO-TEX Standard 100. Terminal nonwoven products include wet wipes, interlinings, automotive carpet backing, and air filtration media.
At a typical finishing line speed of 12–18 m/min, leather base coat application by reverse roll coater uses an acrylic emulsion binder in which acrylic acid constitutes 2.0–4.0 wt% of binder solids. The wet base coat is applied at 30–50 g/m² and dried in a multi-zone tunnel at 60–80 °C for 2–4 min, followed by hydraulic plating at 70–90 °C under 10–15 MPa to compact the film and improve bond to the leather substrate. Top coat is applied at 8–15 g/m² wet and dried at 80–100 °C. If the finish mix pH drops below 3.5, destabilization of co-formulated polyurethane dispersion occurs and causes cratering in the top coat. Tensile strength of the finished leather is measured under ISO 3376:2020, tear strength under ISO 3377:2016, and colour fastness to rubbing under ISO 11640:2018. The finished product types are automotive seating leather, upholstery leather, shoe upper leather, and full-grain leather goods.
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Acrylic acid, CAS 79-10-7, is an α,β-unsaturated carboxylic acid supplied as a clear, colorless liquid with the formula CH2=CHCOOH and a molecular weight of 72.06 g/mol. The product model AA-995-MEHQ describes glacial acrylic acid with a purity specification of ≥99.5 wt% and monomethyl ether of hydroquinone inhibitor at 180–220 ppm. The material is used primarily as a reactive monomer rather than as a finished acid; the terminal vinyl group permits radical polymerization, while the carboxylic acid function supports neutralization, esterification, and hydrogen-bonding interactions. Industrial demand is concentrated in superabsorbent polymers, acrylate esters, detergent additives, and water-treatment dispersants. Physical properties relevant to handling include a normal boiling point of 141 °C, freezing point of 13 °C, density of 1.05 g/cm³ at 20 °C, and a closed-cup flash point below 60 °C. Unlike acetic acid, the molecule contains a polymerizable vinyl group; unlike methacrylic acid, it lacks the α-methyl substituent and therefore shows higher radical propagation rates in aqueous and bulk polymerization. These structural distinctions are amplified in storage and process design.
Specifications for the AA-995-MEHQ model are controlled by gas chromatography, Karl Fischer titration, and colorimetric inhibition testing. The table presents typical release limits for a glacial acrylic acid grade intended for superabsorbent and esterification use. Technical ester grade may carry tighter water limits, while polymer grade may tolerate slightly higher dimer but not higher color.
| Property | Limit | Method |
|---|---|---|
| Acrylic acid purity | ≥99.5 wt% | GC-FID, producer method |
| Water | ≤0.10 wt% | ASTM E203 |
| Dimer | ≤0.50 wt% | ASTM D4415 |
| Color | ≤10 APHA | ASTM D1209 |
| MEHQ inhibitor | 180–220 ppm | ASTM D3125 |
MEHQ is not an inert stabilizer; it requires dissolved oxygen to function as a radical scavenger. Bulk storage under inert gas therefore removes the co-inhibitor and increases polymerization risk in vapor-phase dead spaces. The product should be held at 15–25 °C with an air padding, not nitrogen blanketing. Dimer content is the most specification-sensitive variable for superabsorbent producers because the Michael adduct dimer can act as a chain-transfer agent or introduce branching. Elevated storage temperatures accelerate dimer formation; release at ≤0.50 wt% dimer preserves molecular weight control in high-solids continuous polymerization. Water above 0.10 wt% is not generally a safety issue but shifts stoichiometry in neutralization and esterification reactions. Under CLP, the substance is classified Acute Tox. 4 H302, Acute Tox. 4 H312, Skin Corr. 1A H314, and Aquatic Acute 1 H400.
For bulk handling, 316L stainless steel or glass-lined equipment is specified; carbon steel and copper alloys are excluded because copper ions can initiate polymerization and carbon steel is corroded by warm acid. Production-scale storage experience shows that bottom outlets and pump suction lines are the highest-risk dead zones when temperature stratification develops, particularly in tanks with side-mounted agitators. Transfer pumps should be sealless centrifugal or canned-rotor types with local high-point vents to prevent vapor accumulation. Freezing at 13 °C is a predictable operational boundary; thawing must be conducted below 40 °C and without direct steam lances to avoid localized inhibitor depletion. Acrylic acid vapor is lachrymatory and corrosive, so conservation vents and scrubbers should be rated for low-pressure service with flame arrestors. Transport classification is UN 2218, Class 8, Packing Group II, with the proper shipping name “Acrylic acid, inhibited.” The product should not be held under nitrogen blanket because MEHQ inhibition requires dissolved oxygen; an air padding is maintained in storage. Any maintenance activity on polymerization reactors requires a written monomer-free start-up check after oxygen removal, because residual acid in dead legs can self-initiate over extended shutdowns.
The structural difference between acrylic acid and methacrylic acid is a single α-methyl substituent. The methyl group increases steric hindrance at the propagating radical, reduces propagation rate, and raises the glass transition temperature of the homopolymer from ~106 °C to ~228 °C. Acrylic acid also has a lower pKa than methacrylic acid, leading to higher aqueous dissociation and different neutralization behavior in aqueous polymerization. Compared with acetic acid, which has a pKa of 4.76 and no vinyl group, acrylic acid is both acidic and polymerizable. Compared with acrylate esters such as methyl acrylate or butyl acrylate, acrylic acid contributes carboxylic acid functionality rather than a permanent ester group. In esterification, acrylic acid is converted to the same esters, but the acid form requires corrosion-resistant distillation and storage systems that esters do not.
| Property | Acrylic acid | Methacrylic acid |
|---|---|---|
| Molecular weight | 72.06 g/mol | 86.09 g/mol |
| Freezing point | 13 °C | 15 °C |
| Homopolymer glass transition temperature | ~106 °C | ~228 °C |
| pKa at 25 °C | 4.25 | 4.65 |
The distinction matters in polymer design. Water-swellable crosslinked networks use acrylic acid because the neutralized carboxylate group provides osmotic driving force for fluid absorption; methacrylic acid copolymers are selected when hydrolytic stability, higher stiffness, or reduced water sensitivity is required. In emulsion polymers, a small fraction of acrylic acid is often added for colloidal stabilization and adhesion to metal oxides, with the amount limited to avoid excessive water sensitivity.
Neutralization of acrylic acid to 70–75 mol% sodium acrylate is the first unit operation in continuous superabsorbent polymer production. The heat of neutralization, combined with the polymerization enthalpy, must be removed before the monomer mixture reaches the belt polymerizer; typical feed cooling uses chilled water at 5–10 °C and in-line static mixers to prevent premature gelation. Residual dimer above 0.50 wt% has been observed on production lines to reduce peak molecular weight and to raise extractables in the final polyacrylate network; the specification is therefore enforced at receiving, not after storage. Crosslinkers are added at 0.05–1.0 mol% relative to monomer to create the network. After adiabatic polymerization on steel belt conveyors, the gel is shredded in high-torque extruders, dried in through-circulation dryers, milled, and classified to 150–850 µm for hygiene applications. Residual moisture in dried SAP is typically controlled below 5 wt% and confirmed by loss-on-drying procedures aligned with ISO 17190. Residual monomer is measured by HPLC and specified below 300 mg/kg in hygiene grades; this limit is not achievable if the incoming acid contains excessive dimer and water because side reactions alter the gel curing profile. Unneutralized acid is incompatible with aluminum packaging lines; the acid attacks the oxide layer and liberates hydrogen, so the polymer is partially neutralized and buffered before finishing.
Acrylate ester production converts acrylic acid with methanol, ethanol, n-butanol, and 2-ethylhexanol in the presence of acid catalysts. A continuous reactive distillation train operates with excess acrylic acid to drive conversion; reaction water is removed azeotropically. The acrylic acid feed specification of ≤0.10 wt% water avoids excess water load in the azeotropic separation and reduces ester hydrolysis back-reaction. Acid catalysts are neutralized before distillation; unconverted acrylic acid is recovered and recycled. Esterification plants specify 316L stainless steel or Hastelloy for reboilers and overhead condensers because the warm acid-catalyst mixture is more corrosive than the finished acrylate ester. Unlike acrylic acid, the ester products have lower water solubility and may be stabilized with MEHQ or phenothiazine at different use levels. The change from carboxylic acid to ester functionality changes coating film properties: acrylic acid improves adhesion to metal substrates as measured by ASTM D4541, while esters such as butyl acrylate reduce glass transition temperature and modify flexibility. The acid itself is not used as a solvent or final coating binder; it is a precursor that imparts functionality through copolymerization or esterification.
Low-molecular-weight polyacrylic acid and acrylic acid copolymers with sulfonated monomers are formulated as scale inhibitors and dispersants. Typical weight-average molecular weights for this use are 2,000–5,000 g/mol; fractions above 10,000 g/mol can act as flocculants rather than dispersants and may reduce calcium carbonate inhibition performance. The carboxylic acid density of acrylic acid, compared with methacrylic acid or maleic acid, provides a controlled charge distribution for crystal modification on calcium carbonate and calcium sulfate surfaces. Efficacy is not inferred from composition alone; formulations are screened in dynamic scale loop rigs according to NACE TM0374 or equivalent producer methods. Acrylic acid-based polymers in detergent applications must be compatible with zeolites, carbonates, and bleach systems; the acid monomer is fully neutralized before blending to avoid pH shock and corrosion in spray-drying towers. Because the monomer itself is corrosive, detergent polymer synthesis is usually conducted at dedicated acrylic acid derivative plants rather than at formulating sites.
