TPO (Thermoplastic Polyolefins) is a mixture of a polyolefin-based plastic (usually PP) and an elastomer such as EPDM. Unlike TPV, TPO is not or only partially cross-linked.
TPOs are polymer blends. Depending on the composition, TPO can be made hard or soft. Hard TPO, of which PP and talcum make up about 75% of the composition, are often used as impact-reinforced plastics.
Soft TPO has a much higher elastomer content, sometimes up to 70%. The advantage over other thermoplastic elastomers is that TPO is on average much cheaper. Soft TPO is used as a roofing material, among other things, because it has good UV resistance.