Polymer molding compositions

composition, closure and method of forming it. the invention relates to formulated compositions which can easily form bottle caps, without the need for a liner while still maintaining the pressure requirements, such as for carbonated beverages. the compositions may include an ethylene polymer having a density in the range of about 0.947 to 0.962 g / cm3 a melt index of about 1 to about 10 mm g/10, and another ethylene polymer having a density in the range of about from 0.912 to 0.932 g / cm3, a melt index of about 0.25 to about 6 g / l0 mm, in which the two polymers have a difference of densities greater than or equal to 0.03 g / cm3. in other cases, the composition may include a single component resin with a density from 0.935 to 0.955 g range / cm3 with a melt index in the range 0.3-1.2 g / l0 minutes, wherein the resin comprises a polyethylene polymer.