Ralph Scerbo

Photoinitiators TPO and TPO-L

Blog Post created by Ralph Scerbo on May 18, 2018

In the midst of the daily grind, we tend to forget just how interesting chemistry is. There are chemicals being utilized in various industries which can be catalyzed by UV light. These specialized chemicals are known as TPO photo initiators.


TPO (trimethylbenzoyl diphenylphosphine oxide) is produced in both the solid and liquid state. The solid state TPO has a CAS number of 75980-60-8, while liquid state TPO has a CAS number of 84434-11-7. What makes TPOs so unique is the fact that they undergo hemolytic cleavage, when exposed to UV light, and produce free radicals. Currently, TPOs are being used in various industries. It is being used for UV curing of unsaturated polyesters and resins containing acrylic ester groups. Its particle use here derives from its ability to photo-bleach, resulting in low yellowing coatings. This is needed for white pigmented coatings and printing inks. TPOs can also be utilized as key processing aids for polymerization in artificial nail systems (nail polishes).