PC plastic is polycarbonate, a strong, lightweight, and nearly transparent thermoplastic used in everything from eyeglass lenses to bulletproof windows. It’s one of the most impact-resistant plastics available, roughly 250 times stronger than glass against impacts, while still letting about 88% of visible light pass through. That combination of toughness and clarity is what makes it so widely used.
What Polycarbonate Is Made Of
Polycarbonate is a polymer built from repeating carbonate groups linked to aromatic rings. The conventional manufacturing process combines bisphenol A (BPA), a chemical compound made from phenol and acetone, with either phosgene or diphenyl carbonate. The result is a long-chain molecule that’s rigid, optically clear, and remarkably tough.
There are two main commercial routes to produce it. The older method, called interfacial polymerization, uses phosgene as a raw material. Because phosgene is highly toxic and difficult to transport, manufacturers have increasingly shifted to a melt transesterification process that avoids phosgene entirely. This newer method converts methanol into dimethyl carbonate, which then reacts with phenol and bisphenol A in a melted state with a catalyst. Both processes yield the same final material, but the melt route is safer and produces fewer problematic byproducts.
Key Physical Properties
Polycarbonate’s defining trait is impact resistance. Where acrylic (plexiglass) is about 17 times more impact-resistant than glass, polycarbonate hits 250 times that of glass. This is why it’s the go-to material for safety shields, bulletproof glazing, and protective eyewear. Its tensile strength sits around 60 to 70 MPa, which is slightly lower than acrylic’s 80 MPa, but polycarbonate absorbs energy from sudden impacts far better without shattering.
Transparency is another major selling point. Standard polycarbonate transmits about 88% of visible light, just slightly below acrylic’s 92%. For most applications, that difference is negligible.
Polycarbonate has a glass transition temperature of about 147 to 148°C (around 297°F), meaning it stays rigid and dimensionally stable well above the temperatures encountered in everyday use. It doesn’t actually melt in a clean, defined way like some plastics. Instead, it begins to decompose between 480 and 535°C. This thermal stability makes it suitable for applications near heat sources, like automotive headlight covers and electronic housings.
Where You’ll Find It
Polycarbonate shows up in a surprisingly wide range of products:
- Eyewear: Most prescription lenses and safety glasses are polycarbonate because it’s lightweight, impact-resistant, and optically clear.
- Electronics: Phone cases, laptop housings, and LED light covers rely on its durability and ability to be molded into complex shapes.
- Automotive: Headlight lenses, interior trim panels, and instrument panel covers use polycarbonate for its heat resistance and toughness.
- Safety equipment: Helmets, face shields, riot shields, and bulletproof windows all take advantage of its extreme impact strength.
- Medical devices: Diagnostic equipment housings, sterilizable containers, and face shields are made from polycarbonate because it can withstand sterilization and handles frequent use well.
- Optical media: CDs, DVDs, and Blu-ray discs are made from polycarbonate.
Weaknesses and Limitations
Polycarbonate isn’t invincible. It scratches more easily than glass, which is why polycarbonate eyeglass lenses typically come with a scratch-resistant coating. Without UV stabilizers, it will yellow and become brittle over time when exposed to sunlight, so outdoor applications generally require UV-protected grades.
Chemical resistance is another weak point. Polycarbonate dissolves or degrades when exposed to certain organic solvents, including dichlorobenzene, tetrahydrofuran, dioxane, and cyclopentanone. Strong alkaline solutions like hot sodium hydroxide can also attack it. In practical terms, this means you shouldn’t clean polycarbonate with harsh chemical cleaners or expose it to gasoline, acetone, or similar solvents.
The BPA Safety Question
Because conventional polycarbonate is made from bisphenol A, there’s been ongoing concern about BPA leaching into food and drinks from polycarbonate containers. Small, measurable amounts of packaging materials can migrate into food, and polycarbonate is no exception.
The FDA’s current position is that BPA is safe at the levels that actually occur in foods from approved packaging. A four-year review of more than 300 scientific studies, completed in 2014 by FDA specialists in toxicology, endocrinology, epidemiology, and related fields, did not find evidence to change that assessment. FDA research has also found that humans metabolize and excrete BPA much more rapidly and efficiently than rodents, which are the animals used in most concern-raising studies. When BPA is consumed orally, the body quickly converts it to an inactive form, resulting in much lower internal exposure than what occurs from other routes like injection.
That said, the FDA has taken a precautionary stance for infants. BPA-based polycarbonate is no longer authorized for use in baby bottles, sippy cups, or infant formula packaging. The agency noted this change was based on the industry having already abandoned those uses rather than on a specific safety finding, but the practical result is that these products are now BPA-free.
Newer BPA-free polycarbonates are in development, using alternative monomers that avoid bisphenol A entirely. These are beginning to appear commercially but haven’t yet replaced conventional polycarbonate at scale.
Recycling Polycarbonate
Polycarbonate falls under resin identification code 7, the “Other” category that acts as a catch-all for plastics that don’t fit into the six main recycling streams. In practice, this means polycarbonate is generally not recyclable through curbside programs. Most municipal recycling facilities can’t process it, so polycarbonate products typically end up in landfills unless handled through specialized industrial recycling channels. If you’re looking at the bottom of a plastic container and see a number 7 inside the recycling triangle, that’s likely polycarbonate or another specialty plastic, and your local program probably won’t accept it.