We have Akainu, who is a Logia user with magma capabilities, and Luffy, who can stretch with the Gomu Gomu no Mi. Are their clothes made up of some special material that doesn't burn or tear apart?
From the Devil Fruit article on One Piece Wikia (emphasis mine):
Like many series, One Piece follows the trope that a Devil Fruit power also generally affects the clothes the user is wearing. Paramecia fruit users alter their clothes along with themselves automatically (for example, Luffy's shirt will never burst a button when his chest is swollen in Gear 3rd, Mr. 1's pants become blades along with his legs, etc.), Zoan fruit users' clothes will fit in the same proportions after transformation (Chopper's hat grew big when he was in Monster Point, Jabra's shoes are considerably stretched when in the hybrid form), and Logia fruit users transform their clothes (and subsequent accessories) to their element along with themselves. Oda explained in a SBS once that if he had done it realistically, the comic would have too much unnecessary nudity. However, some users do not seem to apply to this, such as Jewelry Bonney and Honey Queen, whose clothes do not change proportionally to their powers.
So basically, their clothes are just normal clothing. Just that the Devil Fruit's power also affects the user's clothing.
And Oda even explained the reason why he did it that way.