2-Hydroxyethyl Methacrylate (HEMA, CAS No. 868-77-9) is arguably the most widely recognized and extensively utilized hydroxy-functional monomer in the global polymer industry. Featuring a methacrylate backbone combined with a terminal primary hydroxyl group, HEMA combines excellent mechanical rigidity, thermal resistance, optical clarity, and chemical stability.
Unlike acrylate analogs, the alpha-methyl group (-CH3) on the methacrylate backbone sterically shields the polymer chain, imparting superior hydrolytic stability, higher glass transition temperature (homopolymer Tg around +55°C), and outstanding weatherability in outdoor environments.
Technical Specifications & Key Quality Parameters
In industrial and specialty polymer manufacturing, slight variations in monomer purity can drastically alter polymer molecular weight, viscosity, and optical clarity. DECHEM provides technical-grade and high-purity grades of HEMA meeting global standards:
| Key Parameter | Industrial Grade HEMA | High Purity Grade |
|---|---|---|
| Purity (Assay by GC) | ≥ 98.5% – 99.0% | ≥ 99.5% |
| CAS Number | 868-77-9 | 868-77-9 |
| Water Content (KF) | ≤ 0.15 wt% | ≤ 0.05 wt% |
| Color (APHA / Pt-Co) | ≤ 15 | ≤ 10 |
| Homopolymer Tg | +55°C | +55°C |
| Inhibitor (MEHQ) | 150–250 ppm | 50–100 ppm (or custom) |
Major Industrial & Specialty Applications of HEMA
1. High-Solid Thermosetting Acrylic Coatings
HEMA is the cornerstone monomer for producing hydroxylated acrylic resins used in two-component polyurethane (2K PU) and amino-baking systems. Its relatively high Tg (+55°C) contributes film hardness, mar resistance, and solvent tolerance in automotive OEM, machinery, and coil coatings.
2. Biomedical Hydrogels & Soft Contact Lenses
Crosslinked poly-HEMA (pHEMA) forms an optically transparent, hydrophilic hydrogel with water absorption capacity between 38% and 42%, making it the historical and modern benchmark material for soft contact lenses and intraocular devices.
3. Dental Materials
In dental composites and adhesive bonding agents, HEMA acts as a penetrating primer monomer on dentin collagen fibers, providing strong adhesion and durable restorations.
4. Emulsion Polymers & Industrial Adhesives
HEMA is incorporated into waterborne acrylic emulsions (0.5% – 3.0% by weight) to enhance mechanical shear stability, freeze-thaw resistance, and wet adhesion on polar surfaces.
Global B2B Buyer's Sourcing Checklist for HEMA
- Purity and By-product Profile: always verify the Certificate of Analysis (COA) for EGDMA and DEGMA limits tailored to your specific polymerization process.
- Inhibitor Balance (MEHQ): ensure inhibitor concentrations align with your storage timeline without impeding your initiator system during polymerization.
- Packaging & Sea Freight Logistics: HEMA should be shipped in coated steel drums (200 kg), IBC totes (1,000 kg), or ISO tanks from experienced chemical export ports such as Qingdao.