if air is has a dielectric constant of 1 which is ~3kv/mm and material x has constant 30 does this mean that material x is infact 90Kv/mm going off the breakdown of air?

 

No. The constant is a way of comparing permittivity. We use it to compare flux, not voltage. Every media has it's own breakdown voltage.

It's how much of an electric field the media can align to. It's the same principle as the magnetic domains lining up in a media....permeability.

It's about how well a media aligns to flux. Or accommodation of flux.

 

That is the sort of question that I would use Google (Or some other search engine.) to find the answer to. I think it is by far the quickest way to find physical constant values.
I agree with BR-549 that you getting mixed up between dielectric strength and dielectric constant. You can also use Google to find the definition of the two terms.
Les.