How do patio tiles made from rubber granules age?
Patio tiles made from PU-bound rubber granules change over time in colour and surface appearance, while their elastic properties change more slowly. The extent of these changes depends on the type of granules, sunlight at the installation site and the use of the area. Patio tiles pass through a bedding-in phase during the first few weeks. With coloured recycled tyre rubber granules (ELT), the pigmented PU binder initially becomes slightly darker in sunlight; because individual patio tiles receive differing amounts of light, the surface can temporarily appear uneven. A freshly cut EPDM wearing layer may take on a slightly warmer tone during its first days in sunlight.
In sunlight, a patio tile may temporarily become darker because of the PU binder rather than the EPDM rubber granules. This change is reversible: the colour subsequently becomes lighter again and the appearance will generally even out. With UV-stabilised tiles, UV radiation affects the tile more slowly; this does not refer to colour shade and is not a promise that the colour will remain unchanged.
Over the longer term, the colour appearance changes for different reasons depending on the type of granules. Natural black ELT rubber granules are deep black when new, gradually developing an anthracite tone under UV exposure, similar to the colour change seen in car tyres. In coloured ELT, the PU binder is pigmented and forms a coloured coating around the black rubber granules. The colour is held in this coating rather than in the granules themselves, so use on walked-on areas can abrade the coating and reveal the black rubber granules beneath. An EPDM wearing layer is coloured throughout, colour-stable and UV-resistant.
Deposits can also alter the appearance. Dust, pollen and fine sand can settle in the surface structure, making the area appear duller; these residues can be removed, while the slip-resistant properties remain. This should be distinguished from the long-term behaviour of pure ELT under sustained intense sunlight: it slowly loses elasticity and becomes more brittle near the surface, a process that develops more slowly than visible colour changes.