What is 1 N of PG to SI?

1 N (Newton) of PG (propylene glycol) refers to the force needed to accelerate a mass of 1 kg at a rate of 1 m/s². In SI units, force is measured in Newtons, so 1 N is already in SI. If you're referring to the conversion of PG's properties, such as density, you would need to specify which property you're interested in converting.