Introduction to 2-Hydroxyethyl Acrylate (2-HEA)
2-Hydroxyethyl Acrylate (commonly known as 2-HEA, CAS No. 818-61-1) is a versatile, clear and colorless functional acrylic monomer bearing both a highly reactive acrylic double bond and a primary hydroxyl functional group (-OH). With the molecular formula C5H8O3 and a molecular weight of 116.12 g/mol, 2-HEA serves as an essential building block in modern polymer chemistry, particularly in the synthesis of thermosetting acrylic resins, radiation-curable formulations and performance-driven specialty polymers.
In the global specialty chemicals market, 2-HEA is widely prized by formulators and chemical engineers for its unique dual functionality: the acrylate vinyl moiety allows rapid copolymerization with various acrylic, vinylic and methacrylic comonomers, while the terminal primary hydroxyl group offers active crosslinking sites for polyisocyanates, melamine-formaldehyde crosslinkers and epoxy curing agents.
Key Physical and Chemical Specifications
DECHEM produces 2-HEA to strict international quality standards. Key technical parameters include:
| Property | Standard Value | Test Method |
|---|---|---|
| Chemical Name | 2-Hydroxyethyl Acrylate (2-HEA) | IUPAC Standard |
| CAS Number | 818-61-1 | Chemical Abstracts Service |
| Purity (Assay by GC) | ≥ 97.0% (special grades available) | Gas Chromatography (GC) |
| Molecular Weight | 116.12 g/mol | Theoretical Calculation |
| Appearance | Clear, colorless transparent liquid | Visual Inspection |
| Density at 20°C | ~1.100 g/cm³ | ASTM D4052 |
| Boiling Point | 215°C at 760 mmHg (decomposes) | ASTM D1078 |
| Flash Point (Closed Cup) | 101°C (214°F) | ASTM D93 |
| Glass Transition Temp (homopolymer Tg) | -15°C (flexible polymer backbone) | DSC Analysis |
| Water Content | ≤ 0.5% (moisture-sensitive grades lower) | Karl Fischer |
| Free Acid (as Acrylic Acid) | ≤ 0.50 wt% | Acid-Base Titration |
| Inhibitor (MEHQ) | 200-400 ppm (customizable) | HPLC / Spectrophotometry |
★ Why primary hydroxyl reactivity matters in 2-HEA
The terminal hydroxyl group in 2-HEA is a primary alcohol (-CH2-CH2-OH), which exhibits higher steric accessibility and significantly faster reaction kinetics with polyisocyanates (HDI, IPDI) compared to secondary hydroxyl monomers such as 2-HPA. This provides faster ambient cure speeds in two-component (2K) polyurethane systems.
Core Industrial Applications of 2-HEA
1. Automotive OEM & Refinish Clearcoats — 2-HEA is copolymerized with methyl methacrylate (MMA), butyl acrylate (BA) and styrene to produce hydroxy-functional acrylic polyols. When crosslinked with aliphatic polyisocyanates (HDI biuret or trimer), the resulting polyurethane network delivers high-gloss retention, scratch resistance, chemical durability and superior outdoor weathering.
2. UV/EB Radiation-Curable Coatings and Inks — 2-HEA acts as an active reactive diluent and modifying monomer in ultraviolet (UV) and electron-beam (EB) cured printing inks, wood finishes and overprint varnishes. Its low viscosity reduces formulation viscosity without volatile organic solvents, while the acrylate double bond ensures fast radical polymerization under UV exposure.
3. Pressure-Sensitive Adhesives (PSA) & Emulsions — Because the homopolymer of 2-HEA possesses a low glass transition temperature (Tg of -15°C), copolymerizing 2-HEA into acrylic adhesives imparts remarkable flexibility, low-temperature tack and peel strength. The hydroxyl functionality also provides polar anchoring onto metal, glass and plastic substrates.
4. Textile Finishing and Leather Treatment Agents — 2-HEA is widely used in textile binding resins and leather finishing polyacrylates to enhance washability, soft hand feel, abrasion resistance and fiber adhesion.
Handling, Packaging and Quality Assurance at DECHEM
Due to the thermal reactivity of acrylic double bonds, 2-HEA requires stabilized storage under controlled conditions. DECHEM supplies 2-HEA with precisely calibrated MEHQ inhibitor levels in ISO tanks (20-24 MT), IBC totes (1,000 kg) and heavy-duty steel drums (200 kg), exported through our chemical logistics partners.
- Strict moisture control: moisture content is strictly held low to prevent unwanted side reactions in sensitive isocyanate-cured systems.
- Low diester impurities: advanced distillation minimizes diethylene glycol diacrylate (DEGDA) to prevent premature gelation and resin cloudiness.
FAQ on 2-HEA
Q: What is the main difference between 2-HEA and HEMA?
A: 2-HEA is an acrylate with a low Tg (-15°C) offering higher flexibility and faster cure rates, whereas HEMA is a methacrylate with a higher Tg (+55°C) offering greater hardness and thermal stability.
Q: What is the typical shelf life of 2-HEA?
A: When stored below 25°C in original unopened containers away from direct sunlight, stabilized 2-HEA has a guaranteed shelf life of at least 6 months; the confirmed shelf life per DECHEM TDS is up to 12 months depending on grade and storage conditions.