Triphenyl phosphate

Triphenyl phosphate (CAS 115-86-6), commonly abbreviated as TPP, is an organophosphate ester used commercially as a flame retardant and plasticizer across a broad range of industrial materials. It functions by releasing phosphoric acid derivatives during combustion, interrupting the flame cycle without relying on halogenated chemistry. In plastics and polymer compounding, TPP is incorporated into cellulose acetate and PVC.

It is used in engineering resins to meet UL 94 or similar flammability standards while simultaneously improving flexibility. Electronics manufacturers use it as a flame-retardant additive in circuit board laminates and connector housings. It is also used in encapsulant resins where thermal stability under load is a qualification requirement. Lubricant formulators add TPP to hydraulic fluids and gear oils where fire-resistant performance is specified.

This is particularly important in aerospace and industrial environments with ignition risk. In construction materials, it is used to treat rigid foam insulation and sealant formulations requiring passive fire protection. Triphenyl phosphate is supplied as a white crystalline solid or flake, with purity grades typically ranging from 98% to 99%+ for industrial and specialty polymer applications.

Technical grade is the standard commercial form, with high-purity grades available for electronics and aerospace end uses where trace impurity limits are tightly controlled.