The present invention is concerned with the process for preparing a cross-linked stabilized polymer composition using at least one graftable polymer stabilizer, and the subsequent use of that composition for forming pipes, for example PEX pipes. The graftable stabilizer becomes anchored to the polymer such that stabilizer activity is retained in the cross-linked product. Cross-linking can be achieved by conventional processes such as PEXa, PEXb and PEXc. Embodiments demonstrate excellent levels of antioxidant retention (as measured by oxidative induction retention after exhaustive solvent extraction) and the cross-linked product are suitable for portable water applications, including hot water applications.