Sterilizable PVC-free closures

A vessel cap made of metal or plastic for a vessel for receiving foods or beverages, comprising a seal insert made of a seal material which comprises at least three different polymers mixed with further substances,

• wherein the seal material comprises no polyvinyl chloride (PVC),
• wherein the seal material is substantially free from components that are liquid at application temperature,
• wherein the seal material has a Shore A hardness between 40 and 95,
• wherein the seal material comprises at least three different polymers, wherein the first polymer is a propylene polymer and/or propylene copolymer, the second polymer is a thermoplastic elastomer, and the third polymer is a polyolefin elastomer,
• wherein the seal material is composed such that the seal insert withstands a sterilization at temperatures of above 100° C. and up to 132° C.,
• and wherein the seal material, in a dynamic mechanical thermal analysis (DMTA), demonstrates a heating curve for the phase angle tan (delta) the inflection point of which lies above the required sterilization temperature.