US Patent 8177603 Polishing pad composition

Polishing pads for use in chemical mechanical planarization (CMP) or polishing elements/surfaces of such pads are made from a combination of immiscible polymers, for example polyurethane and polyolefin. The polymers are selected on the basis of interfacial interaction, melt index and ratios of melt indices between the polymer phases—a matrix phase and a dispersed phase. By selecting the polymer system such that the two polymers are immiscible in one another and preferentially form separate domains, the dispersed phase can be removed when conditioning or polishing processes expose it. The melt index of individual polymers and the ratio of melt indices determines dispersability of a smaller phase into the matrix, hence the phase size.