Polycarbonate, PC, Lexan
Index
The diagram shows the "Mer" of the linear polycarbonate macromolecule. Polycarbonate is a polyester. 

The material has a good impact strength and is transparent, making it a good window material for face protection and eyeglasses. The material has a density of about 
1.2 Mg/m3, a Young's modulus of 2.4 GPa, tensile strength of 66 MPa, and an elongation to fracture of 110%. Its glass transition temperature is 150 C.
From: Callister, 
"Materials Science and Engineering," 
Wiley (1994)