Lightweight thermoplastic composite products and methods of making same

A method of forming a lightweight polymer-based composite product via casting, the method comprising:

• applying a lightweight filler material to a mold cavity, the lightweight filler material having a density of between 0.1 and 1.0 g/cm3;
• applying a reactive resin to the mold cavity;
• and
• heating the reactive resin and lightweight filler material to polymerize the reactive resin and thereby form a body of polymer material having a shape corresponding to the mold cavity;
• wherein:
• the body has a density that is less than a comparable product that consists mainly or essentially of the polymer.

A lightweight polymer-based composite product comprising:

• a polymer material body formed of an in-situ polymerized polymer, the polymer material body having a first surface and a second surface that is positioned opposite the first surface and the polymer having a density of at least 1.0 g/cm3;
• and
• a lightweight filler material that is embedded in the polymer and that is concentrated on at least a portion of the first surface of the polymer material body so that the lightweight filler material forms a layer on the at least a portion of the first surface of the polymer material body;
• wherein the lightweight filler material has a density of between 0.1 and 1.0 g/cm3.

A method of forming a lightweight thermoplastic composite product, the method comprising:

• positioning a fabric reinforcing sheet within a mold cavity so that the fabric reinforcing sheet extends longitudinally along at least a portion of the mold cavity, wherein the fabric reinforcing sheet includes a plurality of fibers;
• applying a lightweight filler material to a mold cavity, the lightweight filler material having a density of between 0.1 and 1.0 g/cm3;
• applying a reactive resin to the mold cavity such that the reactive resin fully saturates or impregnates the lightweight filler material;
• and
• heating the reactive resin to polymerize the reactive resin and thereby form the thermoplastic composite product having a shape corresponding to the mold cavity;
• wherein:
• the polymerized reactive resin fully impregnates and saturates the lightweight filler material;
• and
• the thermoplastic composite product has a density that is less than a comparable thermoplastic product that consists mainly or essentially of the polymer.