Diisononyl phthalate is widely used as a plasticizer in the production of flexible polyvinyl chloride (PVC) products. Its primary application is to enhance the flexibility, durability, and workability of PVC materials. This makes it a key component in manufacturing items such as cables, wires, flooring, and synthetic leather. It is also used in the production of automotive parts, including dashboards and seat covers, due to its ability to improve resistance to temperature variations and wear. Additionally, it finds use in adhesives, sealants, and coatings, where it helps improve performance and longevity. Its compatibility with various polymers makes it a versatile choice in industrial applications.