| http://www.w3.org/ns/prov#value | - Prior art bladders, which are typically made of a rubber or plastic film material by processes such as welding of films, rotational molding, or dipping, typically could only contain a liquid filler, such as a glycerin, oil or other liquid, for a period of months before the glycerin, oil or other liquid began to migrate through the bladder wall, causing a mess and changing the properties of the fil
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