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AssigneeMassachusetts Institute of Technology
InventorsChul B. Park, Nam P. Suh, Daniel F. Baldwin
Estimating the term…
An extrusion system for providing a foamed material in which a material such as a polymer material is supplied to an extruder for movement through a rotating screw member. The material is placed in a molten state and a foaming agent, such as a supercritical fluid, is introduced into the extruder at a selected pressure so that a two-phase mixture of the molten material and the foaming agent is formed. The foaming agent is then diffused into and dissolved in the molten material to form a single-phase solution which is forwarded from a solution formation to a nucleation device. A thermodynamic instability is induced through a rapid pressure drop, e.g., higher than 0.9 GPa/s in the nucleation device to nucleate microcells in the solution. A further shaping device, e.g., a die, can be used to produce a foamed material of a desired shape.
A method comprising:
A method for forming foamed material comprising mixing together a supercritical carbon dioxide foaming agent and a material to be foamed, forming a single-phase solution of said foaming agent and said material to be foamed, maintaining said single-phase solution at a pressure greater than a solubility pressure of said foaming agent in said material to be foamed at a pressure of at least about 1530 psi, subjecting said single-phase solution to a pressure drop at a pressure drop rate of at least about 0.18 GPa/s (26,100 psi/s) to form sites of nucleation therein by passing said single-phase solution through a constriction causing friction in the solution, expanding said sites of nucleation to form cells, and causing said solution having cells therein to take the shape of a continuous extrusion of microcellular material having a cell density of at least 10.sup.7 sites/cm.sup.3.
Dependencies are inferred from the claim text.