dyneema...

[Sailingsaves]

For those that have not forgotten all the science (as I have).

Nylon is weakest.

polyethylene is next

Polyester is the best of them.

But dyneema is "Ultra-high-molecular-weight polyethylene"

Why is Ultra-high-molecular-weight polyESTER not in existence? Or is it? Or can it not exist?

 

[Neeves]

But nylon has its advantages.

Best has different meanings

Jonathan

Interesting thread, just needed some refreshing?

 

[macd]

But nylon has its advantages.

Best has different meanings

Indeed. You won't find many rock climbers using dyneema for dynamic lines. Or yachtsmen for mooring lines or snubbers.

 

[ithet]

For those that have not forgotten all the science (as I have).

Nylon is weakest.

polyethylene is next

Polyester is the best of them.

But dyneema is "Ultra-high-molecular-weight polyethylene"

Why is Ultra-high-molecular-weight polyESTER not in existence? Or is it? Or can it not exist?

Except that Nylon is stronger than equivalent polyester but stretches more.

 

[thinwater]

For those that have not forgotten all the science (as I have).

Nylon is weakest.

polyethylene is next

Polyester is the best of them.

But dyneema is "Ultra-high-molecular-weight polyethylene"

Why is Ultra-high-molecular-weight polyESTER not in existence? Or is it? Or can it not exist?

Not correct. The link is from the Cordage Institute, which I believe we can agree is authoritative.
https://screenshots.firefox.com/Qf2SKCq09tC6oRJT/www.gpjrope.com

Polyethylene is the weakest common synthetic fiber, followed closely by polypropylene.

Nylon and polyester are close, with different characteristics, but nylon can be stronger (climbing ropes use the good stuff, 3-strand not always so much).

The polymer science behind high strength an high modulus defies a two-sentence explanation and on my specialty; the really short version is that it is related to the crystalline structure and smart guys work on it. But even if there were HM polyester, you might not like its characteristics. It might be fatigue-prone than Kevlar, making it useless.

 

[Sailingsaves]

But nylon has its advantages.

Best has different meanings

Jonathan

Interesting thread, just needed some refreshing?

Yes, quite right. I was thinking of a particular application but didn't write it down. The application in brief was where no stretch, high strength was required, hence me talking about dyneema (which 'beats' the other 3 materials in terms of stretch and strength. Nylon is probably better for tights (that ladies wear on their legs) than polyethylene for sure !

(The lack of elasticity in dyneema is one reason why it is safer than steel cable on 4x4 vehicle winches; no heads chopped off if dyneema snaps).

As an example of what you point out, on my mooring lines, as well as using rubber snubbers, I put a bight (just a loop) in the lines and wrap with a bit of nylon webbing. Idea being that in a storm, the nylon will stretch and take out shock loading and even break well before the mooring lines do, without harming the mooring lines. There is also another bight secured by simple gaffer tape (duct tape). My swinging mooring has plenty of space around it, so length of lines to accommodate all these eccentricities is acceptable.

Once upon a time I would have been able to think and discuss the material science of Ultra-high-molecular-weight polyethylene in depth, but age and other factors mean I can't remember or think like that any longer.

Looking forward to making some soft shackles soon.

I would buy different types of dyneema and do load testing but I don't want to 'waste' money on good line and the data is out there already I am sure (doing research oneself is still more fun imo, but I can't afford the luxury at the moment).

 

[GHA]

I would buy different types of dyneema and do load testing but I don't want to 'waste' money on good line and the data is out there already I am sure (doing research oneself is still more fun imo, but I can't afford the luxury at the moment).

Lost of work, loadtesting, but great fun.

Lots been done before though not immediately obvious from google as the web site is no more, but there is some great reports out there and with with the wonders of the time machine web....

https://web.archive.org/web/20160318230212/http://www.bethandevans.com:80/load.htm

 

[Sailingsaves]

Lost of work, loadtesting, but great fun.

Lots been done before though not immediately obvious from google as the web site is no more, but there is some great reports out there and with with the wonders of the time machine web....

https://web.archive.org/web/20160318230212/http://www.bethandevans.com:80/load.htm

Thanks for that. Looks like the BethEvans website (that disappeared as you say). I think it was the fantastic work done there that got me into dyneema some time ago.
cheers

 

[tudorsailor]

And for those of you with an artificial joints, are you aware that the plastic component is also made from ultra high molecular weight polyethylene? For those of you who have had a tendon repair such as the rotator cuff in the shoulder the suture used is called "fibre wire" but is also ultra high molecular weight polyethylene - AKA Dyneema.
https://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene

TudorDoc

 

[Sailingsaves]

And for those of you with an artificial joints, are you aware that the plastic component is also made from ultra high molecular weight polyethylene? For those of you who have had a tendon repair such as the rotator cuff in the shoulder the suture used is called "fibre wire" but is also ultra high molecular weight polyethylene - AKA Dyneema.
https://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene

TudorDoc

That's really interesting, thanks.
I am guessing the "self-lubricating" and (contrary to what some people say) "abrasion resistance" makes it a good material for joints.

Interesting article, thanks. Used for stitching tendons back together ! Lots of H-C bonds, 'all' molecules parallel (partly responsible for its strength), but easily disrupted by heat because the strength is derived from physical attributes (crystaline structure e.g. as Thinwater pointed out) rather than strong chemical bonding. Hence why dyneema is not good for capstan winches on old landrovers (where slippage can occur and heat built up).

 

[thinwater]

That's really interesting, thanks.
I am guessing the "self-lubricating" and (contrary to what some people say) "abrasion resistance" makes it a good material for joints.

Interesting article, thanks. Used for stitching tendons back together ! Lots of H-C bonds, 'all' molecules parallel (partly responsible for its strength), but easily disrupted by heat because the strength is derived from physical attributes (crystaline structure e.g. as Thinwater pointed out) rather than strong chemical bonding. Hence why dyneema is not good for capstan winches on old landrovers (where slippage can occur and heat built up).

Additionally, Dyneema does NOT do particularly well in all chafe scenarios. It does not do well against high-hardness materials like rock, it does not like heat, and side-to-side is limited. In fact, much of the best chafe gear is either polyester or nylon; these materials, woven as webbing, are better at retaining a protective layer of fuzz. Test it yourself.

 

[Neeves]

Nylon is probably better for tights (that ladies wear on their legs) than polyethylene for sure !

Funny when I read the thread this was my immediate thought - and I then progressed to dyneema tights!

But moving on

Testing dyneema, or any other product, if you have the equipment (which is not particularly cheap) has merit as we all have different ideas and different tests might show up interesting data. I confess to not being strongly motivated toward testing dyneema, I'm more interested in steel, so welcome anyone willing to explore cordage.

Dyneema when it was first introduced, I first came across it in the late 80's, was said to be very UV sensitive and abrasion prone. It then 'became' abrasion resistant - but Thinwater points out - it is not abrasion resistant in some envoronments (and it is quite UV resistant). It appears to be still sufficiently 'new' that we are still learning and new applications are constantly being found. If you look at Thinwater's blog, I'm sure he quotes it above, he has some interesting data - and is 'still current' (he is still, or can be, working in this area). For example - he uses dyneema as a bridle - which seems contradictory - until you read how he does it.

There are new industrial applications - and the DSM website is worth a look - as some of the developments and applications might trickle down. I'm not sure if soft shackles trickled up, or down but dyneema anchor rodes have been used for years.

It could be an interesting thread!

Jonathan

Thinwater's blog is linked on Post 5 and 11 above.

 

[thinwater]

Worth noting, is that soft shackles and other Amsteel splicing tricks can also be done in any single braid. They won't be as strong, but that doesn't always matter.

 

[GHA]

Additionally, Dyneema does NOT do particularly well in all chafe scenarios. It does not do well against high-hardness materials like rock, it does not like heat, and side-to-side is limited. In fact, much of the best chafe gear is either polyester or nylon; these materials, woven as webbing, are better at retaining a protective layer of fuzz. Test it yourself.

Tested some d12 max from Marlow which has some sort of added chafe coating, did very well indeed after months rubbing against stainless with high loads.

 

[Neeves]

GHA

Useful information

I think Thinwater was suggesting dyneema was not good on rock (which is commonly rough and tough) nor with side to side abrasion (though he does not define, in his post, the surface.

To be useful it would be interesting to learn how you tested and what you mean by 'high' loads.

Jonathan

 

[Sailingsaves]

Worth noting, is that soft shackles and other Amsteel splicing tricks can also be done in any single braid. They won't be as strong, but that doesn't always matter.

Worth noting, is that soft shackles and other Amsteel splicing tricks can also be done in any single braid. They won't be as strong, but that doesn't always matter.

Yes.

After I found the joys of amsteel some years ago, a friend and I toyed with a piece of paracord as seen below. Not even genuine paracord; just cheap stuff from ebay. I was only toying around (I could have used a friend's hydraulic press if I wanted to). Difficult to see, but the cord did not break at the splice.

I have been trying to find some cord (8 or 12 strand something) cheaper than dyneema to make some soft shackles for low load applications, but where metal would be less than useful, but have not found anything yet (in the UK).

Clicking on the word "youtube" to make the clip larger and jumping along to 60 seconds or somewhere cuts out a lot of boring stuff.