Bis(3,5,5-trimethylhexyl) phthalate is primarily 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, flooring, and synthetic leather. Additionally, it is utilized in the formulation of adhesives and sealants to improve their performance and longevity. The chemical is also found in certain coatings and inks, where it aids in achieving desired consistency and adhesion properties. Its compatibility with various polymers makes it a versatile additive in industrial and consumer product manufacturing.