Most common cross-linkers are solid epoxy resins in so-called hybrid powders in mixing ratios of 50/50, 60/40 and 70/30 (polyester resin/ epoxy resin) for indoor applications and triglycidyl isocyanurate (TGIC) in a ratio of 93/7 and β-hydroxy alkylamide (HAA) hardener in 95/5 ratio for outdoor applications.  When the powder is baked, it reacts with other chemical groups in the powder to polymerize, improving the performance properties. The chemical cross-linking for hybrids and TGIC powders—representing the major part of the global powder coating market—is based on the reaction of organic acid groups with an epoxy functionality; this carboxy-epoxy reaction is thoroughly investigated and well understood, by addition of catalysts the conversion can be accelerated and curing schedule can be triggered in time and/or temperature. In the powder coating industry it is common to use catalyst masterbatches where 10-15% of the active ingredient is introduced into a polyester carrier resin as matrix. This approach provides the best possible even dispersion of a small amount of a catalyst over the bulk of the powder.