2-Ethylhexyl Acrylate (2-EHA) CAS 103-11-7

Introduction to 2-Ethylhexyl Acrylate (2-EHA)

2-Ethylhexyl Acrylate (2-EHA) is a branched long-chain acrylate ester monomer produced by direct esterification of acrylic acid with 2-ethylhexanol over acid ion-exchange catalyst. The bulky, asymmetric 2-ethylhexyl side chain introduces maximum free volume among commercially common acrylate esters, yielding homopolymers with Tg of approximately –85 °C (–121 °F)—the lowest among standard acrylate monomers used in adhesive and coating formulations. This ultra-low Tg translates into permanent tack, exceptional low-temperature peel adhesion, and high elongation at break in the final polymer film.

In formulation design, 2-EHA functions as the primary “soft segment” and tack-contributing monomer. Its long, branched alkyl chain provides strong van der Waals interaction with low-surface-energy substrates (polyethylene, polypropylene, silicone release liners), making it the backbone monomer of acrylic PSA systems for packaging tapes, labels, and medical plasters. Compared to n-butyl acrylate, the 2-ethylhexyl group provides 30 °C lower Tg, significantly better sub-zero tack retention, and enhanced hydrophobicity. Compared to isooctyl acrylate, 2-EHA offers faster emulsion polymerization kinetics and lower residual monomer levels due to reduced steric shielding at the vinyl site. 2-EHA is also a key comonomer in architectural latex paints requiring crack-bridging flexibility at temperatures down to –20 °C (–4 °F).

Key Features of 2-Ethylhexyl Acrylate (2-EHA)

• Lowest Tg among standard acrylate monomers. 2-EHA homopolymer Tg of –85 °C (–121 °F) produces permanently tacky, highly elastomeric films that maintain peel adhesion and flexibility down to –40 °C (–40 °F), critical for freezer-grade labels and cold-chain packaging tapes.
• Superior low-surface-energy substrate adhesion. The long branched alkyl chain maximizes van der Waals contact with PE, PP, and powder-coated surfaces, providing peel strength 30–50% higher than BA-based PSAs on polyolefin substrates without surface treatment.
• Enhanced hydrophobicity and water resistance. The C8 branched chain provides the lowest water absorption (< 1% at 24 h immersion) among common acrylate ester homopolymers, ensuring long-term adhesion retention in high-humidity environments.
• Excellent compatibility with hard and functional monomers. Miscible and copolymerizable with MMA, VAc, acrylic acid, hydroxyethyl acrylate, and acrylamide across all ratios, enabling Tg tuning from –85 °C to +80 °C (–121 °F to 176 °F) in a single emulsion or solution system.
• Controlled polymerization for low residual monomer. Despite higher steric bulk than BA, 2-EHA achieves > 99% conversion in semi-continuous emulsion polymerization at 75–85 °C (167–185 °F), keeping residual monomer below 100 ppm for food-contact adhesive compliance.

2-Ethylhexyl Acrylate Chemical & Physical Properties

Applications of 2-Ethylhexyl Acrylate (2-EHA)

Pressure-sensitive adhesives (PSA) for tapes and labels: 2-EHA is the dominant soft monomer in acrylic PSA triaxial formulations. At 70–90% 2-EHA with 2–5% acrylic acid (functional) and 5–25% MMA or VAc (hard), produces packaging tapes with peel strength 10–18 N/25mm, tack > #18 steel ball, and shear holding > 10,000 hours. The branched chain provides permanent tack at –20 °C (–4 °F) for cold-chain logistics labels.

Architectural latex paints and elastomeric coatings: Copolymerized with MMA, BA, or VAc at 30–60% 2-EHA loading in semi-continuous emulsion polymerization at 75–85 °C (167–185 °F). Produces exterior elastomeric coatings with crack-bridging capacity at –15 °C (5 °F), dirt pick-up resistance, and 10-year exterior durability. Typical solids 45–55%, particle size 150–300 nm.

Textile finishing and nonwoven binders: 2-EHA-acrylic latex applied at 5–20% add-on to polyester, cotton, and nonwoven substrates for ultra-soft hand feel, wash durability, and dimensional stability. Cured at 140–160 °C (284–320 °F) for 60–90 seconds. The hydrophobic C8 chain provides superior wet-rub fastness and water repellency versus BA-based binders.

Flexible packaging laminating adhesives: 2-EHA copolymerized with functional monomers (hydroxyethyl acrylate, glycidyl methacrylate) for solvent-free laminating adhesives bonding PE/PP films to aluminum foil and PET. Provides peel strength > 4 N/15mm on untreated polyolefin films without corona treatment.

Construction sealants and caulks: 2-EHA-based acrylic emulsions used as binder in high-elongation (> 400%) acrylic sealants for expansion joints, window perimeters, and concrete crack repair. Maintains flexibility at –30 °C (–22 °F) without plasticizer migration.

Storage & Safety Precautions for 2-Ethylhexyl Acrylate (2-EHA)

• Storage: Store in tightly sealed, grounded steel drums or IBC totes in a cool, well-ventilated warehouse below 30 °C (86 °F), away from heat, sparks, open flame, and direct sunlight. Do NOT store above 40 °C (104 °F). 2-EHA is stabilized with 15–20 ppm MEHQ inhibitor which requires dissolved oxygen to remain effective—maintain 5–10% air headspace in bulk tanks. Keep away from oxidizers, strong acids, strong bases, peroxides, and free-radical initiators. Shelf life 12 months unopened; 30 days after opening with proper headspace.
• Safety: 2-EHA is a combustible liquid (Flash point 82 °C / 180 °F)—not classified as flammable under GHS, but vapor can form explosive mixtures at elevated temperatures. Causes skin sensitization and eye irritation. Harmful to aquatic life with long-lasting effects. Wear butyl rubber gloves, chemical splash goggles, and organic vapor respirator during handling. Ensure ventilation to keep airborne concentration below 5 ppm (TWA). In case of skin contact, wash immediately with soap and water—do NOT use solvent wash. In case of spill, contain with inert absorbent.
• Transport: 2-Ethylhexyl Acrylate is classified as Non-DG under IATA/IMDG/ADR (flash point exceeds 60 °C threshold for Class 3). No UN number, no packing group required for transport. Standard dry container shipping acceptable. Ensure drums are upright, secured, and protected from temperature extremes above 40 °C (104 °F). Avoid co-loading with strong oxidizers or peroxide initiators. Summer shipments in tropical regions benefit from shaded or ventilated container stowage.
• QC note: On receipt, verify GC purity (≥ 99.0%), water content (≤ 0.10%), and MEHQ inhibitor level (15–20 ppm). Check for premature polymerization: presence of gel particles, cloudiness, or viscosity increase above 2.2 mPa·s indicates inhibitor depletion or thermal exposure—reject the lot. Confirm drum integrity and pressure relief vent functionality before opening. Verify inhibitor level if material has been in transit for more than 30 days at ambient temperatures above 35 °C (95 °F).

2-Ethylhexyl Acrylate (2-EHA) FAQ

Q: How does 2-EHA compare to n-Butyl Acrylate (BA) in PSA formulations?

A: 2-EHA homopolymer Tg is –85 °C (–121 °F) versus –54 °C (–65 °F) for BA. The 2-ethylhexyl chain provides significantly better low-temperature tack (peel retention at –20 °C), 30–50% higher peel strength on untreated PE/PP, and lower water absorption. BA polymerizes faster and is more cost-effective. For general-purpose packaging tapes, BA performs adequately; for freezer-grade labels, medical plasters, and polyolefin bonding, 2-EHA is the preferred soft monomer.

Q: Why does my 2-EHA drum show slight viscosity increase after summer transit?

A: This indicates partial thermal polymerization caused by inhibitor depletion at sustained temperatures above 40 °C (104 °F). MEHQ requires dissolved oxygen; in sealed drums at high temperature with insufficient headspace, inhibitor consumption accelerates. If gel content is below 0.1% and viscosity remains under 2.2 mPa·s, the material is usable after filtration through 200-mesh screen. Specify drums with 5–10% air headspace and avoid prolonged exposure above 35 °C (95 °F) during transit.

Q: Can 2-EHA be used as the sole monomer for PSA without any hard monomer?

A: No. 2-EHA homopolymer at Tg –85 °C is too soft and lacks cohesive strength—tape would exhibit excessive cold flow, poor shear holding, and adhesive transfer. A hard monomer (MMA, VAc, or styrene) at 5–25% is required to raise Tg into the –30 °C to –10 °C window and provide internal cohesion. Acrylic acid (2–5%) is additionally needed for crosslinking sites and substrate wetting.