• sheet
  • and the method described in -U.S. Patent No. 2,961,710 which consists in treating a polyester urethane foam sheet with a mixture of methylene chloride and silicone oil dissolved in petroleum oil to impregnate the same and subjecting the impregnated sheets to jets of high velocity air to rupture portions of the cellular structure to form a greater plurality of interconnecting cells. (google.com)