The Difference Between Polycarbonate & Acrylic

Many of the plastics you use daily are made out of acrylic or polycarbonate.

Acrylic and polycarbonate are often confused as being the same type of plastic, but they are actually very different. They do share some characteristics, however. Both are lightweight and of high clarity, but they are manufactured using different processes and materials. They also have different strengths, weaknesses and applications.

Manufacturing

Acrylic typically contains polymethyl methacrylate, or PMMA, and is often sold as Plexiglas or Lucite. Acrylic plastic polymers are formed in a process called bulk polymerization that uses either batch cell or continuous method processing to form the plastic, depending on the shape and thickness of plastic required. Polycarbonate is sometimes called polycarbonate of bisphenol A. This is because it can be made with bisphenol A and phosgene. The process of making this polycarbonate begins by reacting bisphenol A with sodium hydroxide, the resulting sodium salt of bisphenol A being then reacted with phosgene. However, polycarbonate is also made in a process called free radical polymerization. The polycarbonate you see in bulletproof glass contains bisphenol A and is called a thermoplastic, meaning it can be molded when it is hot. The polycarbonate used in eyeglasses and in baby bottles is made using the second process; it is called a thermoset plastic, meaning it will not melt easily and cannot be molded.

Uses

Acrylic is used in motorcycle helmet visors, helicopter and submarine windows, and as protection for spectators in hockey arenas. Aquariums and terrariums also use acrylic as a barrier; it is used in a variety of lighting fixtures. Polycarbonate is used in CDs and DVDs, eyeglass lenses, safety glass lenses and in automotive headlamp lenses. It is also used in computers, drinking bottles, riot shields and visors, and bulletproof glass.

Strength and Durability

Acrylic is more likely to chip than polycarbonate because it is less impact-resistant. It does not scratch easily, however, and will not yellow over time. Acrylic can be polished to restore its clarity, while polycarbonate cannot. Polycarbonate is more flexible than acrylic and it has high impact-resistance, making it stronger. Acrylic cracks more easily than polycarbonate under stress, but polycarbonate has low flammability, while acrylic will burn slowly and is not recommended in areas where flames may be present. Acrylic is very rigid. Unlike polycarbonate, it cannot be purchased in more flexible grades.

Workability

Acrylic tends to be easier than polycarbonate to cut with tools such as saws or routers; it will crack if drilled near an edge. Polycarbonate typically does not crack when being drilled. The edges of acrylic can be polished smooth if necessary; polycarbonate cannot be polished.

Cleaning

Acrylic has a low chemical resistance; when cleaning acrylic, it is best to use only mild soap and water. Polycarbonate has a higher chemical resistance than acrylic; it can be cleaned by harsher cleaners containing chemicals such as ammonia. Neither plastic should be cleaned with solvents.

References

• Colorado Plastics; Polycarbonate (Lexan) vs Acrylic (Plexiglass); Drew Schwartz; 2010
• Hydrosight; Acrylic vs. Polycarbonate: A Quantitative and Qualitative Comparison
• Evonik Industries; Physical Properties of Acrylite FF Acrylic Sheet; 2001
• University of Southern Mississippi Polymer Science Learning Center; Polycarbonates; 2005
• Innovative SafPlast: About Polycarbonate