4,4'-(1,3-Dimethylbutylidene)diphenol, also known as Bisphenol I, is primarily used as a monomer intermediate in the production of polycarbonate resins. These resins are durable, high-strength materials commonly applied in the manufacturing of plastic sheets, impact-resistant panels (such as bulletproof glass), and electronic components. Additionally, it is utilized in the synthesis of heat- and chemical-resistant coatings and adhesives.