High limiting oxygen index electrical insulation laminates

A laminate structure suitable for use as electrical insulation in on-board equipment in railcars or railways, comprising:

• a) a mica-aramid paper layer comprising 35 to 55 weight percent mica, 20 to 60 weight percent of a first binder, and 5 to 25 weight percent of a first aramid floc, based on the amount of mica, first binder, and aramid floc in the mica-aramid paper layer, the mica being distributed uniformly in the mica-aramid paper layer, the mica-aramid paper layer having a first and second face;
• and
• b) an aramid paper layer comprising 35 to 75 weight percent of a second binder and 25 to 65 weight percent of a second aramid floc, based on the amount of second binder and second floc in the aramid paper layer, the aramid paper layer being essentially free of mica, the aramid paper layer having a first and second face;
• wherein the mica-aramid paper layer by itself has a limiting oxygen index (LOI) of 37 percent or greater, and the aramid layer by itself has a LOI of 30 percent or less, the aramid paper layer having a tensile strength and elongation greater than the mica-aramid layer;
• and
• wherein the first or second face of the mica-aramid paper layer is homogeneously and continuously bound to the first face of the aramid paper layer;
• the laminate structure further having:
• i) a thickness of at least 0.10 mm,
• ii) a LOI of greater than 32 percent, and
• iii) when exposed to a flame in an oxygen environment to determine LOI, the laminate structure burns as one piece.