PU paint has two types: curing type and two-component type. The advantages are good adhesion, high hardness and good toughness; the operation points of PU paint are as follows: spray viscosity; primer 14-16 seconds; top paint 10-11 seconds; color paint 12 -14 seconds; if the viscosity is too high or the spraying is too thick, it is easy to cause pinholes. The longer the recoat time interval, the less likely to be pinholes; diluent solvent: mixed solvent, selective use of PU thinner, not NC The thinner is replaced, because the curing agent will react with water and alcohol, which will cause no drying or rash; ratio: different curing agents will have different ratios, which cannot be changed at will; yellowing: dry film After a period of time or UV irradiation, it will change. For products that require yellowing resistance, such as white series, you must choose an appropriate main agent and curing agent, such as a yellowing resistance curing agent.