2-PAC
A polyurethane paint compound used for more permanent, lasting a12 months or longer, and hardened line markings on synthetic surfaces. The compound is a mixture (a two-pack finish) of polyurethane coloured resin along with a hardener of polyisocyanate resin. Unlike water-based paint markings, which can be easily applied by groundstaff, are short-term, lasting from a couple of weeks to a month or so, an application of a 2-PAC paint will usually require a specialist contractor, with appropriate PPE, as mistakes can be expensive to correct, unlike an error with a water-based paint, which can be easily rectified.
Due to the hardened nature of 2-PAC compounds there can be a gradual build-up of material with incremental applications and this can affect the playability of a pitch over time.