The present invention provides a method for producing an at least partially crosslinked polymer composition, having a first melt index (MI) value and a first tensile strength, comprising the steps of: a. providing an ethylene vinyl acetate (EVA) copolymer, the EVA copolymer having a second MI value and a second tensile strength and containing at least 30 wt % units derived from vinyl acetate, b. adding from 0.01 to 0.03 wt % of an organic peroxide, wherein the organic peroxide is diluted in 0.001 to 0.05 wt % of white oil, and c. blending the EVA copolymer and the organic peroxide at a temperature sufficient to initiate crosslinking. The first MI value of the at least partially crosslinked polymer composition is less than 5 g/10 min (190° C., 2.16 kg).