Aug 27, 2013 at 5:41 pm #1307025
As most of you know, Cuben fabric is essentially cross grid dyneema/spectra threads sandwiched between layers of mylar/polyester film.
Dyneema/spectra is essentially Ultra High Molecular Weight Polyethylene. Since Cuben fabric, especially at the lower weights is not very waterproof and prone to folding and crinkle stress damage reducing waterproofness (see Richard N.'s research on Cuben Fabric), and it is very expensive–i've been thinking about alternatives.
For example, what about UHMWP film? Why not cut out the middle man of turning the former into woven fibers and putting it in-between poly plastic, why not just pure UHMWPE?
It would be much more waterproof, puncture resistant, possibly cheaper (see below), and long lasting. I was doing some research on product prices of this stuff. Here is one site i found for just a quick example:
Their thinnest film is 3mil thick, which is probably too thick and heavy to compare to most tent/tarp use Cuben fabric, but hopefully one can find it thinner. But let's just use this as an example. If i wanted to make a 7×8 tarp, and i bought 28 feet of this material at 2.76 per foot of 24inch wide material, it would cost me about 77 dollars not including shipping.
Theoretically, if one could find thinner film, it would cost less and weigh less. I wish this website gave some weights, because i have no idea how much this 3 mil stuff would weigh per square yard. It may be that i'm missing something big in all this, so if anyone knows better please enlighten me. One issue that i foresee right off hand besides the uncertainty of weight is the issue of how to bond the film together. This stuff is notoriously slippery and doesn't glue well. Since UHMWPE has a lowish melting point, perhaps one could just simply use a clothes Iron and melt the film together?
As an interesting aside, apparently thicker panels/sheets of this material can be used for iceless skating rinks! I had never heard of that before, and found it quite interesting.Aug 27, 2013 at 5:52 pm #2019230
@slammerLocale: Oklahoma Flat Lands
Interesting concept but heat is most likely the only way of adhering pieces together. sewing might be possible but how to seam seal?
This set up would last through the post apocalyptic acid rain.
And bird droppings will wipe right off.Aug 27, 2013 at 8:48 pm #2019297
Perhaps one could sew, then melt some extra material over the sewn area to "seam seal it"? I would imagine it would be pretty hard to sew though.
Man, finally, a tarp that sheds bird droppings like a non stick Teflon pan sheds eggs…
I guess it would make an extremely bad tent floor material.Aug 27, 2013 at 9:20 pm #2019306
@scfhomeLocale: Chocorua NH, USA
There was a post on MYOG a while back about bonding heat sheets, that led me to try pieces on a bag heat sealer with adjustable heat. At the right setting, it sealed the stuff as strong as the material.
Also tried some Beacon spray-on contact cement and found that produced a tight bond, although messy to apply.
Perhaps the high mol. wt. stuff has different bonding characteristics. Mylar is certainly much more difficult to bond that many other plastics.
What interested me most were your comments about the strength of this stuff.
Can you be more specific, and possibly illustrate somehow its strength.
P.S. Not sure that the 3/4 oz weight Cuben has as low water resistance as you suggest, because there have been so many satisfied users who have posted here.
And it should be noted that there are lighter nylons and polyesters becoming available now. I've experimented with a .9 oz double-coated nylon from France made for Paragliders. The coating was too weak, but I plan to try several different sprays to see if can be reinforced, much as some have gotten good results using silicon sprays to refresh older silnylon flies.Aug 27, 2013 at 10:01 pm #2019323
Thank you for the bonding info/feedback.
I have yet to work with the stuff so i don't know exactly how strong or not it is, just have read enough to indicate that it's pretty strong stuff for the weight. Read the wikipedia article on it–it mentions it's somewhat unusual molecular pattern is what contributes to it's high tenacity, general strength and high abrasion resistance. It's not exactly the same thing as Dyneema/Spectra because these being gel spun orientates directionality of the molecules which increases the strength some more. The braiding of fibers also probably increases it's strength some too (especially the tensile strength).
I understand what you are saying about Cuben, but i would rather not take the chance as i'm looking for truly long lasting and durable qualities. I want something that i can be sure will be truly waterproof for years and under many conditions and constantly used. I think most Cuben is fine for what most use it for, semi-regular backpacking trips (with the occasional long trips interspersed). I'm looking at it more for living outside indefinitely in combo with backpacking trips. Hence why i'm looking for something a little more ultra, and would gladly pay a bit of weight penalty for it. If i can find some UHMWPE film that is 2oz per square yard and under, i would be happy.
I have a custom Zpacks PonchoTarp which uses the 1oz Cuben which has the thicker poly film plus some extra dyneema thread, and overall i'm happy about it and figure it should last a long while in being waterproof…but i'm a bit worried about the poncho part of it decreasing the life of the tarp part. Plus i'm looking for something separate for my wife. The poncho tarp isn't big enough for the both of us realistically (even with bivies).Aug 27, 2013 at 10:10 pm #2019325
3 mil polyethylene weighs 2 oz per square yardAug 27, 2013 at 10:34 pm #2019331
Hi Jerry, thanks for the info. I'm assuming you're referring to one of the more common and cheaper forms of P.E.? Do you know if there is any weight differences between that and the UHMWPE stuff?Aug 28, 2013 at 9:20 am #2019443
From what i gather so far, there probably isn't any significant weight difference between the different forms of PE film's.
In that case, i would like to go down to at least a 2 mil thick film, but i can't find anyone that makes this AND at the same time sells it in non bulk quantities. Most companies i've contacted have a minimum sell of 500 lbs of the stuff. That first company i linked is one of the very few i've found which sells it by the foot, but their minimum thickness is 3 mil.
Plus, i also found out that it's not as naturally/innately UV resistant as i thought it was. It can be treated or modified to be UV resistant but that also is hard to find, especially for film versions.
Argghh…Aug 28, 2013 at 9:57 am #2019464
I don't think polyethylene is UV resistant either, but you can have it out in the sun for months before it degrades a lot.
Maybe UV resistant isn't important for typical backpackers that don't spend that much time in the sun. Like if you just did a few weeks per year, or tended to hike somewhere and put your tent up at the end of the day or in the shade,…Aug 28, 2013 at 11:23 am #2019510
Tyvek is made from 100% polyethylene and it is UV resistant. Also the desity of the material probably will very between LDP,HDP,UHMW, and cros linked polethylene. So the best way to know what the weight is is to call the manufacture and ask.Aug 28, 2013 at 11:38 am #2019522
@owareLocale: Steptoe Butte
Fabrics made for shading plants from hot sun are made from polyethylene.Aug 28, 2013 at 12:18 pm #2019542
I've used regular polyethylene in garden and it disintegrates in one season
I've also used UV treated polyethylene and it lasts for several years
I don't know what they do to polyethylene to make it UV resistantAug 28, 2013 at 12:57 pm #2019558
@ckrusorLocale: Northwest US
UHMWPE film and fiber are very different. UHMWPE film is in no way a substitute for a composite of UHMWPE fibers (like cuben).
Consider carbon as an analogy. Carbon fiber composites (including laminar composites like carbon fiber-containing Cubic Tech products) are extraordinarily strong per unit weight. Carbon fiber composites are the gold standard for high strength, high rigidity, low mass parts. Monolithic blocks of carbon or carbon films, though, are mechanically worthless. They have very low strength and could never be used for load-bearing parts.
There are two major reasons that composites (like Cuben laminates and carbon fiber parts) are strong: a network of fibers creates many interfaces across which a propagating crack or tear must jump, and fibers can be highly oriented (much more than films) so long molecules are aligned to best withstand forces the part will experience. A piece of film has no interfaces that would retard the propagation of a crack or tear, and, even in "oriented" films (like Mylar), the molecules are mostly arranged in a chaotic jumble. Many polymers are available as both fibers and films (polyester, nylon, Vectran, UHMWPE), and the film is always much more mechanically weak and fragile than a layer of fibers of the same weight.
Also, as others have mentioned already, making seams will be close to impossible with UHMWPE film. Any UHMWPE film will be impossible to bond. The important property is free surface energy. The more free surface energy a material has, the more effectively it can be bonded. Plastic films that bond well (like Kapton) have a free surface energy in the neighborhood of 50 dynes. Mylar (the cuben surface) can be more difficult to bond because it has lower free surface energy: about 43 dynes. The surface energy of UHMWPE is about 28 dynes. This is close to some varieties of Teflon, which are in the range of 18-25 dynes.
There are adhesives that are marketed for UHMWPE surfaces, but don't overlook the bond strength values. Compare those to urethane adhesives for other films (like Mylar). Bond strengths for UHMWPE surfaces improve from abysmal (negligible) to poor if you flame or plasma treat them first to oxidize them, but plasma treatment is not practical for MYOG and flame treatments can't be used for films (it will just melt them). Even if you pay for plasma treatment and exotic adhesives, the best achievable bond will be very weak.
If you find a biaxially oriented UHMWPE film, you won't be able to heat-seal it because the oriented molecules will curl when heated, causing disorientation, deformation, and extreme shrinkage of the material near the heated area. Mylar (which is biaxially oriented) has this problem, and for the same reason. Mylar itself is never heat-sealed. It is often laminated to polyethylene (LDPE), and the polyethylene surfaces of the Mylar laminate are heat-sealed at a temperature low enough to avoid shrinkage of the Mylar. If you find a non-oriented UHMWPE film, you can heat-seal it the same way that painter's plastic or Heatsheets can be heat sealed, but non-oriented UHMWPE film will be similar in strength to painter's plastic or Heatsheets, so I don't see a reason to use it.Aug 28, 2013 at 2:54 pm #2019591
Maybe use the same adhesive tape as on CubenAug 28, 2013 at 7:51 pm #2019687
Thank you for taking the time to write that in depth and holistic reply–i learned a bit reading it. I basically agree with the points you made, and i was/am aware that UHMWPE, Dyneema, and Cuben fiber all have different properties, though some basic molecular similarities in common.
I wasn't trying to say earlier that pure UHMWPE could compare to Cuben, (or even dyneema cord) per similar weight, as far as tensile strength and tear resistance goes–knew there was a significant difference there. But it seems to me that the mylar is the weak point in Cuben fabric, as well as the cost. Both of which i would like to avoid, which is why i was musing about alternatives and looking for good feedback.
And while i agree with you somewhat comparing UHMWPE to other more common forms of plastic film/sheeting and their strength, i do suspect the former is perhaps just barely significantly stronger and more suited to being used as a tarp than lot's of other plastics and other versions of PE.
Even in it's more natural forms, UHMWPE has some interesting properties. Just a 1 inch thick sheet of it (non layered, non fibrous, but compression molded) can fully stop a 38 caliber bullet from close range. Course alternately layered, cross latticed dyneema cord could stop even signficantly more, but i would still say the former is impressive.
Anyways, you convinced me enough to do this in lieu. Rather than outright buy a boat load full of this stuff, i'm going to purchase just a few cheap feet of it for a relative few dollars, and experiment a bit with some pieces first. I will try tearing it apart from different directions, try puncturing it with different levels of pressure, try heat bonding it, and leave a piece outside in the sun and weather. Should give me a much better idea of what this stuff is actually about rather than reading and theorizing.
Thanks againAug 29, 2013 at 9:45 am #2019809
@ckrusorLocale: Northwest US
Yes, as you point out, the impact strength of UHMWPE is amazing. I think it is substantially higher than any other polymer.
This will be an interesting test. I don't know of any other experiments like this with UHMWPE film. I'm looking forward to hearing about your results.Aug 29, 2013 at 8:05 pm #2019997
@scfhomeLocale: Chocorua NH, USA
Thank you for the additional info.
By all means, please post any new discoveries.
You might also want to read the several posts of Matt Edwards on this site about the durability of his Cuben shaped tarp on extended treks.Aug 31, 2013 at 1:41 pm #2020499
"Consider carbon as an analogy. Carbon fiber composites (including laminar composites like carbon fiber-containing Cubic Tech products) are extraordinarily strong per unit weight. Carbon fiber composites are the gold standard for high strength, high rigidity, low mass parts. Monolithic blocks of carbon or carbon films, though, are mechanically worthless. They have very low strength and could never be used for load-bearing parts. "
that is not a good analogy in my opinion because the molecule of carbon fiber (graphene) is very different Carbon blocks which typically have graphite molecules. the shape and strength of the atomic bonds of the molecule will have a big impact on the strength of a material.
I found a wikipedia article on UHMWPE and it lists it as UV resistant. If you buy plastic sheeting in the store frequently the packaging doesn't list the type of plastic and if it does say polyethylene when the actual material maybe mostly polyethylene with anther type of plastic or a dye mixed in If it is a mix the other platic or dye may be quickly damaged by UV causing the plastic to become brittle or fall apart.
If using adhesives with polyehtylene make sure the label say it will bond to polyethylene. Many common glues don't. Dupont's tyvek tap does bond to it. Others have had good luck with contact cement and a 3M spray on adhesive.Aug 31, 2013 at 11:03 pm #2020595
"If using adhesives with polyehtylene make sure the label say it will bond to polyethylene. Many common glues don't. Dupont's tyvek tap does bond to it. Others have had good luck with contact cement and a 3M spray on adhesive."
Those are good suggestions, however, my current understanding (open to revision though) is that something like tyvek homewrap uses HDPE, which is fairly slippery, but even that doesn't compare to the slipperyness of UHMWPE which is significantly more so. Plus, tyvek homewrap is "flashspun" meaning there are individual fibers involved perhaps giving more surface area to bond too as compared to a true "film" type plastic and process?
Is it possible that this could create an issue for adhesives that even are meant to bond with general polyethylenes? Not having any kind of background in chemistry or physics, i really don't know (hell, i didn't even attend college).
What i would be very interested in seeing is Dupont or some other company, taking the process they use with Tvyek home wrap, and applying it to UHMWPE instead of HDPE. It would come closer to re-creating the strength of dyneema. One could make it thinner than tyvek homewrap to cut down on weight.
It probably still wouldn't be as strong on a same weight to weight basis as Cuben fabric, but strong enough and potentially A LOT cheaper because the process is already common, well known, and compared to Cuben fabric relatively simple. I actually know somebody who works for Dupont, perhaps i should inquire into whether or not Dupont has researched or has started to work with UHMWPE in such a manner.Sep 30, 2013 at 10:35 pm #2029793
Well, i finally got around to ordering some of this material. Unfortunately, i could only find 3 mil stuff, which based on what Jerry told me earlier, i expect to weigh around 2 oz per square yd.
However, where there is a will, there is a way. I'm going to experiment with heating it to a certain temp and stretching it out some, no idea how that will work, but hey, corn flakes and Teflon WPB membranes were created sort of accidentally and i'm working with some knowledge base.
So i ordered 10 feet of 24 inch wide, 3 mil material. I will keep some unadulterated for tear and puncture tests. I will try to upload a video of this (i've never uploaded videos before so…).
I'm also going to experiment with the stretched stuff (as mentioned) and folding it over and taking the smallest sewing needle or pin i can find, folding it over and pricking little holes through the material and trying it out poncho style. I will also experiment with bonding material together with a lot of elbow grease and a warm-hot Iron.
Stayed tuned. Might be a little while since i just got my M50 fabric and Apex and want to mod two of my down quilts first before i do anything, and a forum member asked if i could put up some pics of my Zpacks Cuben poncho tarp (2nd on list), then my polypro cord/baselayer/mid layer project (3rd).Sep 30, 2013 at 10:41 pm #2029795
Another experiment i plan to try, is to bond some film with some dyneema cord again using a lot of elbow grease and a hot iron.Oct 1, 2013 at 6:42 am #2029839
@fluffinreach-comLocale: no. california
on a side note, in my travels thru the depths of sewing, i have played with that iron on adhesive strip/gauze/rolls of stuff they sell at fabric stores. it will, at reasonably low temperatures stick to eff'n near ANYthing.
point of fact, i once made a wax-paper ~ aluminum foil sandwich using it which could not be pulled apart (without destruction).
it comes in assorted widths, and is cheap.
just a thought …
ps : good luck ya'll on bonding that hdpw (whatever stuff). i'v made gaskets for liquid 02 pumps out of it, and it is indeed some very slippery material. if what you have is a sheet of the same milk colored plastic… yikes.Oct 1, 2013 at 7:24 am #2029856
Hmmm..tis worth trying, thanks for the tip Peter!
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