Varnishing your acrylic artwork is always advisable, not only to seal & protect it but also to bring up the lustre of the colours and give the whole piece an even finish right across it so that your eye is not distracted from the desired focal point of your composition.
Archival permanent matt varnish for acrylic paintings. Seal your acrylic work with a transparent, matt acyrylic layer which is breathing, permanent and protects against UV damage.