Threads

Don't know if 240 thicker is than 140, but do know that 6/0 is thicker than 8/0. Only bought one spool of Kevlar thread and had trouble with it breaking all the time. Was told that it is probably old. Got it for spinning deer hair and it breaks easier than the 8/0. Never bought another spool to find out.

I don't know whether 240 is thicker than 140, but I do know they are stronger.  I have used 240 to spin deer hair.  I have used kevlar also & it is very tough & very strong.  As killdeer mentioned it doesn't break easily & it can dull your scissors quickly. 

When talking about denier, the higher the number the thicker the thread.
 
When talking the ought system (8/0, 6/0, etc) the higher the number the thinner the thread, but there is variation from manufacturer to manufacturer.  One manufacturers 8/0 is another's 10/0 and another's 12/0.  Just like the variations we see in material colors from different manufactures.  Olive is not olive across the board.
 
There are many folks in the industry trying to unify thread sizes using the denier system, that way the consumer (us) will be able to have consistency when buying from multiple manufacturers.
 
As far as Kevlar thread.  I have tied with several manufacturer's brands of it and can safely say that you can drag a jeep out of mud with the stuff.  I recommend a ceramic bobbin if you will use it a lot because it will groove a steel bobbin relatively quickly.  Regular thread will too, but it usually takes many years to do so.  Downfalls of Kevlar threads are they can be difficult to cut, especially if your scissors are not super sharp and you have a good bit of tension on the thread as you cut it.  Since they are so strong, you can bend hooks easier if you are not careful and also cut right through your materials you are tying with due to too much tension.  I have seen this the most with hollow hairs, such as deer, elk, etc.  I use Kevlar for eggs made of glo bug or Mcfly foam the most. 
 
Hope this helps.