Flame Retardant PC Mylar Sheet Die Cut Insulator for Square Cylindrical Battery Cell Product Overview A die-cut flame retardant polycarbonate Mylar sheet engineered as the interlayer part inside lithium battery modules. Two dedicated profiles are produced: a square profile for aluminum-shell prismatic cells and a circular and ring profile for cylindrical cells. In a square shell module the sheet sits between the cell body and the aluminum module frame, and between the cell