PC
A clear, tough plastic used in protective eyewear lenses.
- Also known as
- polycarbonate, bisphenol A polycarbonate
In everyday products
- Safety glasses — Clear polycarbonate lenses
Structure and behaviour
[–O–C₆H₄–C(CH₃)₂–C₆H₄–O–C(=O)–]ₙ
Carbonate links connect bisphenol-A-derived units. The selected melt route supplies the carbonate carbonyl from diphenyl carbonate and removes phenol; this differs from addition polymerisation of a vinyl monomer.
- Optical grades provide a transparent path through a curved lens without using glass.
- High impact toughness is useful in eyewear, but lens thickness, mounting and defects also affect failure.
- Moulding determines curvature and optical form; it does not create a protection rating by itself.
- Hard coatings address surface wear because a tough lens can still scratch.
- PC and PMMA can both look clear; choosing between them requires the desired balance of toughness, surface performance and processing.
Preparation routes
Bisphenol A and diphenyl carbonate route
Melt transesterification and polycondensation. The phenolic groups of bisphenol A react with diphenyl carbonate to build carbonate-linked chains. Phenol is removed as the chains grow. Each chain-forming unit needs two reactive ends. Removing phenol favours carbonate-chain growth; it is not a by-product of later lens moulding.
Industrial catalysts and controlled removal of small molecules support chain growth. Drying and optical-grade processing come later. Optical-grade shaping and coating cannot identify which industrial PC synthesis supplied the resin.
Material limits
PC lenses, coatings and frames form a complete eyewear system. The material trace includes a BPA-based melt-polymerisation route.