This is determined by both safety regulations and functional requirements. Windshields must stop occupants’ heads from being thrown out in collisions and retain partial visibility after breaking, hence laminated glass is used. Side and rear windshields need to be breakable to create escape access for rescue operations while avoiding flying sharp fragments, so tempered glass is the mainstream choice. Nevertheless, some high-end vehicles equip side windows with laminated or tempered-laminated glass to boost safety (penetration resistance, anti-theft performance) and sound insulation.

Tempering must be completed prior to edge encapsulation (typically plastic injection molding). Plastics cannot withstand the ultra-high temperatures inside tempering furnaces. After tempering, the cleanliness, surface temperature and primer coating treatment of glass edges are critical factors that directly affect the adhesion and sealing performance of subsequent injection-molded encapsulation.