Dyneema

Dyneema is a brand of ultra-high-molecular-weight polyethylene fiber spun into rope that is stronger than steel wire of the same weight and barely stretches. It has displaced stainless wire for halyards, sheets, and increasingly for standing rigging and soft shackles on racing yachts, cutting weight aloft and reducing pitching. The fiber floats, resists chafe and ultraviolet better than aramid, but creeps slowly under sustained load, so highly loaded stays are pre-tensioned and inspected.