Reprocessable materials are provided that include a product of cross-linking a glycidyl methacrylate grafted high-density polyethylene (HDPE-g-GMA) with a polymacrolactone of formula (II) to form a cross-linked polymer exhibiting vitrimer characteristics. Methods for preparing the cross-linked polymer materials include reacting the glycidyl methacrylate grafted high-density polyethylene of with the polymacrolactone in the presence of a first catalyst under conditions that initiate cross-linking of HDPE-g-GMA with the polymacrolactone. Mechanically reprocessable articles include a structural element that is or includes the cross-linked polymer material. Examples of the mechanically reprocessable articles include pallets or molded structures formed from the material and configured to support a load of at least 1000 kg without bending.