|
1. A method comprising producing a flame retardant thermoplastic fiber-reinforced porous core by combining reinforcing fibers, a first thermoplastic polyolefin material and a compounded material comprising a flame retardant compounded with a second thermoplastic polyolefin material, wherein the flame retardant thermoplastic fiber-reinforced porous core comprises a web formed from the reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, wherein the compounded material comprises an antioxidant that turns from a first color to a second color upon exposure to an environment comprising oxidizing agent present at a first concentration, and wherein the antioxidant turns from the second color back to the first color upon exposure to an environment comprising oxidizing agent present at a second concentration lower than the first concentration, and wherein the flame retardant thermoplastic fiber-reinforced porous core is stored in the environment comprising oxidizing agent present at or below the second concentration to maintain the flame retardant thermoplastic fiber-reinforced porous core at the first color.
|