🧩 PMMA-CST – Cast Polymethyl Methacrylate
(Premium variant of acrylic, obtained by casting in molds, with a dense molecular structure and superior stability. It is more rigid, more chemically resistant, and optically clearer than extruded PMMA. Used in high-quality automotive lenses and premium decorative parts.)
🔹 What is PMMA-CST
PMMA-CST (Cast Polymethyl Methacrylate) is the mold-cast variant of acrylic (PMMA). The casting process produces a material with reduced internal stresses, increased hardness, and superior transparency, ideal for optical and aesthetic applications. Cast acrylic has excellent dimensional stability, better solvent resistance, and higher clarity than extruded PMMA (PMMA-EX).
🔧 Composition
- Polymethyl Methacrylate (MMA): 98–100 %
- UV / Thermal Stabilizer Additives: 0.5–2 %
- Density: 1.18–1.20 g/cm³
- Softening Point: ≈ 110–120 °C
- Melting Point: ≈ 170–190 °C
- UV Resistance: Excellent – does not yellow.
- Transparency: 92–93 % (maximum optical clarity).
🚗 Where PMMA-CST is used in the automotive industry
| Component | Example parts | Observations |
| Premium Headlights | Lenses, covers, diffusers | Superior clarity, perfect optical finish |
| LED Lighting | Transparent caps, optics | High UV and thermal resistance |
| Interior Decorative | Glossy frames, panels | Deep gloss, glass-like appearance |
| Technical Optics | Prisms, light guides | Maximum precision and clarity |
🔧 Welding Temperature and Methods
| Method | Optimal Temperature | Observations |
| Hot Air | 230 – 250 °C | Uniform melting, requires precise control |
| Heat Plate (Mirror) | 210 – 240 °C | Clean joint, no optical bubbles |
| Chemical Bonding | — | Recommended for clear finishes (acrylic solvent) |
🔩 What to Weld PMMA-CST With (Material Compatibility)
Cast PMMA is compatible with all materials in the acrylic family, but requires temperature precision to avoid cracking.
✅ Compatible with:
- PMMA-CST ↔ PMMA / PMMA-EX / PMMA-HI / PC+PMMA – ideal.
- PMMA-CST ↔ Transparent / Optical PMMA – fully compatible.
❌ Incompatible with:
- PP, PE, PA, PVC, PS, simple ABS, TPO – no thermal adhesion.
💡 ReplastMD Recommendation:
Use cast PMMA rods or transparent PMMA rods at 230–240 °C. Slow and controlled heating is essential — the material can crack if overheated. For aesthetic results, chemical bonding with acrylic solvent (e.g., Acryfix) offers an invisible joint.
🏭 Manufacturers and Trade Names
- Röhm / Evonik: Plexiglas® GS (Cast)
- Arkema: Altuglas® Cast / ShieldUp®
- Mitsubishi: Perspex® Cast / Lucite® GS
- Chi Mei: Acrypet® Cast
🧠 How to Identify PMMA-CST
- Engraved marking: >PMMA<, >PMMA-C<, >PLEXIGLAS GS<.
- Very rigid, glossy surface, with a “glass-like” feel. Scratches less easily than PMMA-EX.
- Softens at ≈ 230 °C, slow melting, no bubbles.
- ReplastMD practical test: if the part is extremely clear, rigid, and reacts slowly to hot air, it’s confirmed PMMA-CST (cast acrylic).
🛠️ PMMA-CST Welding at ReplastMD:
At our ReplastMD service center (Chisinau, Ciocana sector), we perform professional PMMA-CST welding and bonding for premium lenses and thick optical panels, ensuring an invisible joint and perfect optical gloss.