A soccer ball’s bladder is its innermost part and the component that holds air.
Bladders are built out of butyl or latex, being butyl the most commonly used material.
Butyl bladders retain air very well and for much longer periods of time (several weeks) and offer greater feel quality when compared to latex bladders.
However, butyl bladders are less responsive when kicked as soon as they get deformed — which occurs more easily.
This kind of bladder material is used in the majority of middle to upper priced footballs.
Latex bladders, due to their responsiveness and better surface tension, are the preferred choice in professional competitions.
Latex bladders’ disadvantages are that they tend to lose air much faster (so they need to be filled frequently) and latex isn't as durable as butyl.
Natural latex rubber bladders have the softest responsiveness and feel.
Nevertheless, due to their micro pores letting air slowly escape, their weak spot is air retention. They need to be re-inflated with greater frequency, once a week minimum.
Carbon-latex bladders, as the name suggests, have carbon powder inside of them to help close many of their micro pores preventing them from losing air so quickly.
This offers soccer balls using carbon-latex bladders softer feel, proper bounce and same angle re-bounce benefits.
Polyurethane (PU) bladders are also being used in balls made by some manufacturers.
Futsal and indoor soccer ball bladders are filled with foam instead of air to reduce their bouncing capability because of the hard flooring those soccer variants are played on.