US Patent 9259820 Chemical mechanical polishing pad with polishing layer and window

A chemical mechanical polishing pad is provided having a polishing layer; and an endpoint detection window incorporated into the chemical mechanical polishing pad, wherein the endpoint detection window is a plug in place window; wherein the endpoint detection window comprises a reaction product of ingredients, comprising: a window prepolymer, and, a window curative system, comprising: at least 5 wt % of a window difunctional curative; at least 5 wt % of a window amine initiated polyol curative; and, 25 to 90 wt % of a window high molecular weight polyol curative.