Acrylic glass, a transparent thermoplastic known as Plexiglass (polymethyl methacrylate or PMMA), is a lightweight, shatter-resistant material widely used in aviation for its versatility and clarity.

Background and Evolution

Acrylic glass was developed in the 1920s by chemists like Otto Röhm, commercialized as Plexiglass by 1933. Its aviation use began during World War II, replacing glass in aircraft like the B-17 Flying Fortress for canopies and windows due to its durability and formability. In commercial aviation, it gained prominence in planes like the Boeing 707, evolving into a staple for modern designs such as the Airbus A320.

How Acrylic Glass is Used

• Passenger Windows: Forms outer or secondary layers of cabin windows, providing visibility and safety.
• Cabin Dividers: Shapes transparent partitions or decorative panels, enhancing aesthetics and space division.
• Lighting Covers: Used in cabin light diffusers and secondary exterior lenses, distributing light evenly.
• Instrument Panels: Covers non-critical gauges or displays, offering clarity and impact resistance.

Why Acrylic Glass is Used

• Lightweight: At 1.19 g/cm³, half the density of glass, it reduces aircraft weight for better fuel efficiency.
• Shatter Resistance: Breaks into large, dull pieces rather than sharp shards, improving safety over glass.
• Optical Clarity: Transmits ~92% of light, rivaling glass for visibility in windows and displays.
• Formability: Easily molded or thermoformed into complex shapes, ideal for custom fittings.
• Cost-Effectiveness: Cheaper to produce and replace than glass, balancing performance and budget.

Technical Specifications

• Density: 1.19 g/cm³, significantly lighter than glass.
• Melting Point: ~160°C, limiting high-heat applications.
• Hardness: ~3 Mohs, softer than glass but sufficient for non-abrasive roles.
• Thickness: Typically 2–10 mm for aviation uses.

Comparison to Alternative Materials

• Laminated Glass: Stronger and safer for windshields, but heavier and costlier.
• Soda-Lime Glass: Harder and heat-resistant, but brittle and denser.
• Polycarbonate: Tougher and more impact-resistant, though less scratch-resistant and costlier.
• Chemically Strengthened Glass: Stronger and harder, but heavier and less moldable.

Acrylic glass excels in weight savings and formability over durability-focused options.

Role in Modern Aviation

In aircraft like the Boeing 737 and Airbus A350, acrylic glass dominates passenger windows (outer layers) and interior fittings, reducing weight while maintaining functionality. It complements laminated glass in critical areas and polycarbonate in high-impact zones, as seen in the Boeing 787 Dreamliner.

Environmental and Economic Considerations

• Production: Energy-efficient extrusion or casting, with moderate costs.
• Cost: Lower than glass or polycarbonate, ideal for widespread use.
• Recycling: Recyclable into new PMMA, though less common in aviation due to wear.

Future Trends

Thinner, UV-resistant formulations could expand its use in larger1 windows or lightweight composites may reduce its role in favor of advanced materials.

Summary

Acrylic glass’s lightweight, shatter-resistant nature and clarity make it a key plastic in aviation’s windows, dividers, and lighting. Since World War II, it has supported safety and efficiency, holding a vital role despite competition from stronger plastics and glass.