What Is 2-Hydroxypropyl Acrylate (2-HPA)?
2-Hydroxypropyl Acrylate (2-HPA, CAS No. 25584-83-2) is a functional acrylic monomer produced by the addition reaction of acrylic acid with propylene oxide. Commercial 2-HPA is a clear, colorless liquid comprising a major isomer (2-hydroxypropyl acrylate, ~75–80%) containing a secondary hydroxyl group, and a minor isomer (1-methyl-2-hydroxyethyl acrylate, ~20–25%) containing a primary hydroxyl group.
With a molecular formula of C6H10O3 (molecular weight 130.14 g/mol), 2-HPA combines a low homopolymer glass transition temperature (Tg ≈ -7°C) with low volatility, excellent flexibility and moderate crosslinking reactivity.
Key Physical and Chemical Characteristics
| Technical Parameter | Standard Specification | Significance |
|---|---|---|
| CAS Registry Number | 25584-83-2 | Global regulatory compliance |
| Assay (Total Isomers by GC) | ≥ 93.0% / ≥ 97.0% | Polymerization efficiency |
| Molecular Weight | 130.14 g/mol | Low VOC formulation profile |
| Appearance | Clear, colorless liquid | High-clarity coatings |
| Density at 20°C | ~1.050 g/cm³ | Consistent formulation dosing |
| Boiling Point | 198°C – 205°C (decomposes) | Low volatile loss during baking |
| Flash Point (Closed Cup) | 96°C | Safe industrial handling |
| Homopolymer Tg | -7°C | Balanced flexibility and toughness |
| Moisture Content (KF) | ≤ 0.3% / ≤ 0.5% | Prevents isocyanate consumption |
| Acid Value (as Acrylic Acid) | ≤ 0.3 / ≤ 0.5 wt% | Prevents catalyst poisoning |
| MEHQ Inhibitor | 200-400 ppm | Ensures storage stability |
★ Primary vs. secondary hydroxyl reactivity in 2-HPA
Because the predominant isomer in 2-HPA contains a secondary hydroxyl group (-CH(OH)CH3), its reaction rate with isocyanates is naturally more moderate and controlled than that of 2-HEA. This extended pot life provides superior flow, leveling and bubble release in high-solid automotive OEM coatings.
Major Industrial Applications of 2-HPA
1. Automotive OEM & Coil Coatings — in automotive topcoats and industrial coil coatings, 2-HPA provides the optimal combination of flexibility, impact resistance and weatherability. The branched methyl group on the propyl chain disrupts polymer crystallization, enhancing film clarity and flexibility even after thermal aging.
2. UV/EB Curable Formulations — 2-HPA acts as an efficient monofunctional reactive diluent in radiation-cured wood finishes, plastic coatings and screen-printing inks. It exhibits significantly lower skin irritation and lower volatility compared to lower-molecular-weight acrylates.
3. Specialty Acrylic Adhesives and Sealants — when copolymerized into pressure-sensitive adhesives (PSAs), 2-HPA improves polymer cohesion and substrate wet-out on hydrophobic plastic substrates (polyethylene and polypropylene films) while maintaining high tack.
4. Synthetic Leather & Resin Modification — in polyurethane dispersions (PUDs) and acrylic leather coatings, 2-HPA enhances tensile elongation, bending fatigue resistance and soft tactile feel.
Storage, Handling and Procurement at DECHEM
DECHEM ensures steady supply and strict batch-to-batch consistency of 2-HPA. Product is packaged in standard 200 kg steel drums, 1,000 kg IBC totes or bulk ISO tanks.
- Storage temperature: store between 15°C and 25°C, away from direct sunlight, open flames and oxidizing agents.
- Shelf life: up to 12 months under recommended warehouse conditions with proper container seal (per DECHEM TDS).
FAQ
Q: Is 2-HPA supplied as pure or mixed isomers?
A: 2-HPA is supplied as a mixture of isomers, which is the standard commercial form of this monomer.
Q: What grades are available?
A: DECHEM supplies 2-HPA-93 (≥ 93%) and 2-HPA-97 (≥ 97%), both inhibited with MEHQ and supplied with COA per lot.