Laminated glass is the type of windshield glass made from two glass layers bonded around a plastic interlayer.
The interlayer is commonly polyvinyl butyral, or PVB. When the glass is struck, it usually forms a spiderweb pattern while remaining attached to the plastic instead of scattering into large, sharp fragments. That helps preserve occupant protection and keeps the windshield in its frame.
French chemist Édouard Bénédictus patented an early laminated-glass process in 1909 after observing that a coated laboratory flask could crack without completely shattering. Automobile windshields became its most familiar application, and laminated safety glass became widespread during the 1930s and 1940s.
Tempered, toughened glass is different: it is heat-treated to strengthen it and typically breaks into many small blunt pieces. It is common for side and rear windows, while laminated glass is standard for most modern front windshields. The plastic layer can also improve sound insulation and block much ultraviolet radiation.