an easily recyclable cross - linked isotactic polypropylene that is additionally miscible with polyethylene is formed from a chemical reaction of combining a polymer , sulfur , peroxide , an accelerator , and at least one additive . the polymer can be mixtures of isotactic polypropylene homopolymer with an elastomer ; mixtures of isotactic polypropylene homopolymer with thermoplastic - based mixes ; mixtures of isotactic polypropylene copolymer with an elastomer ; mixtures of isotactic polypropylene copolymer with thermoplastic - based mixes ; or combinations thereof . the accelerator can be a sulfur accelerator .