Diisononyl phthalate is widely used as a plasticizer in the production of flexible polyvinyl chloride (PVC) products. It enhances the flexibility, durability, and workability of PVC, making it suitable for applications such as cables, wires, flooring, and synthetic leather. Additionally, it is employed in the manufacturing of automotive parts, including dashboards and seat covers, due to its ability to withstand varying temperatures and resist degradation. Its compatibility with polymers also makes it a key component in adhesives, sealants, and coatings, providing improved performance and longevity.