Synthetic fibre lifting and lashing gear

Green Pin should be a well known brand for mariners around the world. They have now developed a new lifting and lashing chain made from synthetic fibre that is much lighter than steel for the same strength:

But they are not alone using synthetics to produce lifting gear. Even for the largest heavy lifts there are synthetic fibre slings being used:

This reduce the weight on hook quite drastically, thus increasing both the weight that can be lifted and the reach of the crane used.

Ultra-high-molecular-weight polyethylene ( UHMWPE , UHMW ) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene , ( HMPE ), it has extremely long chains, with a molecular mass usually between 3.5 and 7.5 million amu.[1] The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made.[2]

UHMWPE is odorless, tasteless, and nontoxic.[3] It embodies all the characteristics of high-density polyethylene (HDPE) with the added traits of being resistant to concentrated acids and alkalis, as well as numerous organic solvents.[4] It is highly resistant to corrosive chemicals except oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating (see boundary lubrication); and is highly resistant to abrasion, in some forms being 15 times more resistant to abrasion than carbon steel. Its coefficient of friction is significantly lower than that of nylon and acetal and is comparable to that of polytetrafluoroethylene (PTFE, Teflon), but UHMWPE has better abrasion resistance than PTFE.[5][6]

been on yachts for many years now
melts at low temp and not that resistant to abrasion I would say
How do you know when to replace it?