Isophthalic acid is a dicarboxylic acid with the chemical formula C8H6O4, known for its distinctive aromatic structure. It appears as a white crystalline solid and is an important intermediate in the production of polyesters and resins. Isophthalic acid is primarily utilized in the manufacture of polyethylene terephthalate (PET) and other copolymers, enhancing their thermal stability, mechanical strength, and chemical resistance. Its applications extend to the coatings, fiber, and plastics industries, making it a valuable compound in various manufacturing processes, especially in producing high-performance materials.