Plexiglass is actually a brand name for a type of acrylic plastic. The primary difference lies in the specific manufacturing process, which gives Plexiglass certain distinct advantages over some other forms of acrylic.
Understanding Acrylic and Plexiglass
Acrylic is a versatile thermoplastic material known for its transparency, strength, and durability. Scientifically, it's a polymer known as polymethyl methacrylate (PMMA). It's commonly used as a lightweight, shatter-resistant alternative to glass.
Plexiglass, on the other hand, is a registered trademark for a specific brand of acrylic sheet, originally developed by Rohm and Haas. Just as "Kleenex" is a brand of facial tissue, Plexiglass is a brand of acrylic. Other well-known brand names for acrylic include Perspex, Lucite, Acrylite, and Optix.
Key Manufacturing Distinction: Extruded vs. Cell Cast
The most significant difference between Plexiglass and other acrylics often comes down to how they are manufactured:
- Extruded Acrylic: This type of acrylic is produced by melting acrylic polymer and pushing it through a die to form sheets. This process is generally more cost-effective, allowing for higher volume production and typically resulting in a lower price point for the consumer. Extruded acrylic can have wider thickness tolerances, and may contain more impurities or internal stresses, making it potentially more prone to chipping when cut or drilled.
- Cell Cast Acrylic: In this method, liquid acrylic monomer is poured into a mold made of two glass sheets. The monomer is then polymerized (cured) in an oven. This slower, more labor-intensive process results in a higher-quality material. Plexiglass is exclusively manufactured using this cell cast method. This is considered a significant benefit because cell-cast acrylic offers superior optical clarity, greater hardness, better scratch resistance, and improved overall strength compared to extruded acrylic. It also tends to be more consistent in thickness.
Comparative Properties
While both acrylic and Plexiglass share many characteristics, their manufacturing differences lead to variations in performance and application suitability:
| Feature | Extruded Acrylic | Cell Cast Acrylic (including Plexiglass) |
|---|---|---|
| Manufacturing | Melted and pushed through a die | Liquid monomer poured between glass molds and cured |
| Optical Clarity | Good, but can have slight distortions/impurities | Excellent, superior clarity, less internal stress |
| Hardness | Slightly softer, more prone to scratching | Harder, more scratch-resistant |
| Durability | Strong, but can be more brittle when machined | Stronger, more resistant to cracking or chipping when machined |
| Machinability | Can melt or chip more easily during cutting/drilling | Easier to cut, drill, and polish cleanly without melting |
| Cost | Generally lower | Generally higher |
| Applications | Picture frames, basic signs, economical glazing, display cases | Aquariums, high-quality signage, art pieces, aircraft windows, custom fabrication |
Practical Implications
Understanding this distinction is crucial when selecting materials for specific projects:
- Cost-Efficiency: For applications where budget is a primary concern and extreme optical clarity or precision machining isn't critical (e.g., simple protective barriers or non-illuminated signs), extruded acrylic is often the more economical choice.
- Premium Quality: For projects demanding the highest optical clarity, superior scratch resistance, and ease of fabrication (e.g., museum display cases, architectural glazing, high-end furniture, or detailed artistic work), cell-cast acrylic like Plexiglass is the preferred option despite its higher cost. It offers better performance in terms of longevity and aesthetic quality.
- Durability and Aesthetics: Cell-cast acrylic's harder surface makes it more resilient to wear and tear, and its pristine clarity ensures that colors and details seen through it remain vibrant and undistorted.
In essence, while Plexiglass is a premium form of acrylic, the term "acrylic" encompasses a broader range of products, including both extruded and cell-cast varieties, each suited for different applications based on their manufacturing process and resulting properties.
