Method of forming thermoplastic foams using nano-particles to control cell morphology

Abstract

A process for making closed-cell, alkenyl aromatic polymer foams using nano-particle nucleation agents to control the cell morphology of the resulting foam includes forming a polymer melt at a temperature above the polymer glass transition temperature (for crystal polymers) or the polymer melt point (for amorphous polymers); incorporating selected nano-particles into the polymer melt; incorporating blowing agents into the polymer melt at an elevated pressure; optionally incorporating other additives, such as flame retardants, into the polymer melt; and extruding the polymer melt under conditions sufficient to produce a foam product having a desired cell morphology, characterized by parameters such as reduced average cell size range and / or increased asymmetry of the cells.

Description

Background of the invention

[0001] The present invention relates to a method for preparing alkenyl aromatic polymer rigid foams with a wide range of cell morphologies by using nanoparticles as nucleating agents. This type of rigid foam can be used to form rigid insulating foam panels suitable for many conventional insulation applications.

[0002] The physical properties of rigid polymer foam sheets (e.g., their compressive strength, thermal conductivity, dimensional stability, water absorption) depend largely on the microstructure of the material from which the sheet is formed, i.e., the cells of the foam. hole shape. However, controlling polymer foaming to the extent required to consistently produce a desired cell morphology that will optimize the overall properties of the foam, or improve a specific property (e.g., the insulating value of the foam) is difficult.

[0003] Prior art attempts to prepare foam microstructures with desired cell morphologies include the use of ...

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