1,4-Phenylene diisocyanate (PDI), also known as 1,4-benzenediamine diisocyanate, is an aromatic compound characterized by the presence of two isocyanate (-N=C=O) functional groups attached to a phenylene ring. This compound is primarily utilized in the production of polyurethanes and other polymers due to its reactivity and ability to cross-link with various polyols. Its unique structure allows for the synthesis of rigid and flexible foams, elastomers, and coatings with enhanced mechanical properties and chemical resistance. Additionally, PDI plays a significant role in the development of specialty materials in industries such as automotive, construction, and textiles.