Answer by
LeheckaG (1826)
Particle board or other composite-glued woods,
because of their porousness,
require (2) coats of a good primer or a good polymer (polyurethane) sealant.
Otherwise, much of your paint soaks up into the material,
resulting in an uneven finish,
which can get dirty and is more difficult to clean or re-paint.
Use an appropriate-paint for whatever your-particle-board will be used for.