From looks of it, Luffy’s fruit may have similar awakening to that of Katakuri’s fruit. Limitless possibilities!!
I'm starting to buy the theory that luffy's fruit is actually a logia
Kaido mentioned how it should be impossible for him to change the directions of his attacks
All logias have a special ability
Monet could absorb heat
Crocodile could dry anything he touched
Akainu,aokiji and ace could change the weather
Luffy's special ability could be vulcanization, or any other rubber property upped up to a hundred