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Bonding to woven UHMWPE fabric (aka a real PITA)


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  • #3768985
    Justin W
    Spectator

    @light2lighter

    I recently bought and am waiting on some 200D UHMWPE woven fabric from Aliexpress.  I would like to bond a film to it for waterproofness and dimensional stability.  From past attempts, and from reading/researching, it seems like this is fairly difficult to do because UHMWPE doesn’t really “melt” like most other plastics and has such a low surface energy.

    You can thermally bond it to other UHMWPE or other forms of PE, but it requires fairly high pressure and very precise temps and times otherwise you run the risk of weakening the fibers by decreasing the molecular crystalinity (via overheating).    So unfortunately, I don’t think I can just take an iron and melt some PE film into it like I want to. I might be able to do it if I melt encapsulate the PE film around the fibers from from front to back though?

    Another thought was to dissolve some HDPE in acetone or tolulene (or the like) and brush the solution onto the fabric.  The hope is that the surface of the fabric might get very weakly attacked before the solvent evaporates and would help the PE bond to it?  But, I am not certain even this would work well enough.

    Can’t afford a sonic welder or the like, so that is out.

    Last possible solution is making one of these, a cold plasma “wand”: 
    https://youtu.be/wOV8kliF4eo

    My spouse already has one of those violet ray devices for cosmetic use and that should provide the necessary voltage (you need around 50, 000 volts and these typically output around 25 to 50k).  Probably the most difficult part would be trying to find a container of helium reasonably priced.

    With the cold plasma, I can alter the surface of the UHMWPE.  This is essentially what makers of DCF do to be able to bond the thin mylar/PET films to the UHMWPE. Then bonding it should be a lot easier.

    Any suggestions, tips, or the like?

    #3769522
    Alan W
    BPL Member

    @at-reactor

    As you have learned, bonding with UHMWPE is EXTREMELY difficult.  You’ve nailed the problem statement: non-melting, no-surface energy (lay term).

    Following is reinforcement, perhaps much more than you wanted, using my understanding for the science of why “gluing” to PE is so hard, how this has been traversed with PEs before UHMWPE, and why UHMWPE is an even more difficult challenge.

    All PE’s are essentially CH2 repeating units in very long chains, just “macromolecules” in the family of saturated (negligible C=C double bonds), linear hydrocarbon oils and waxes. Such saturated, linear hydrocarbons don’t surface bond usefully to anything. There is no molecular functionality (polarity and/or reactivity) available for bonding, either hydrogen or covalent.

    How does one bond something to oil? By using surfactant molecules having a hydrocarbon end of the molecule and a functional end of the molecule comprising Oxygen, Phosphorous, or other non-hydrocarbon moiety. Think about a washing machine and detergent. One uses the “long enough” detergent molecules to provide (entropy driven) mixing on the oil side and hydrogen bonding on the water side.

    Multi-layer plastic bottles use this approach to bond less expensive PE layers used for structural heft to various barrier layers used for limiting permeation of O2, CO2, water, etc. (typically nylons, EVOH, etc.). Mil-thickness tie layers, typically comprising expensive PE copolymers with Oxygen moieties, are placed between the PE layer and a very dissimilar barrier layer. The tie layers partly mix with the PE on one side and mix and/or bond to the barrier layer on the other side. It’s sort of like laundry detergent but in reverse. Instead of washing away the oil using surfactant to bond oils with water, the polymers are “frozen” (cooled to ambient) while in the mixed and/or bonded state. Food and beverage bottles and films only a couple of millimeters thick can have 11 layers of different structural, tie, and barrier polymer layers.  (A useful bottle, but a recycling nightmare.)

    Alas, the dissimilar layers are coupled while in the melt phase under high pressure, and this is not easily applicable to non-melting UHMWPE. See below.

    Optionally, the linear paraffins, including UHMWPE, will MIX with select other molecules when not too dissimilar (without significant molecular polarity) – BUT!! this is useful only when the molecules are in liquid form. Think grease with oil, melted paraffin wax with gasoline, etc. But don’t think about mixing “frozen” wax or gelled diesel, unless willing to heat to a more liquid state. (And don’t put polar water or too much polar ethanol in your gas tank or they will phase separate.)

    On the mixing thought, thick-walled HMWPE pipes for pressurized water and natural gas service can be “welded” to other pipe sections by thermal melting (liquefaction) of the pipe ends. (HMWPE is “extra” high MW for extra strength but it still meltable, unlike Ultra High MW for extreme strength.) The melted HMWPE PE molecules in their liquid states are forced one pipe end to the other, and then the joint is frozen in place by cooling. Although it is difficult to obtain uniform melting with enough contact time for molecular mixing without distortion and weak spots, heating rigs and supporting collars have been developed for such PE pipe welding. However, for residential and commercial construction, simple mechanical clamping methods are typically preferred as cheaper and more reliable for PE and PEX piping joints (unlike gluing or solvent bonding for PVC and CPVC piping).

    The additional, intractable problem for such a melt mixing with UHMWPE is its strength. Literally. Although the Ultra High MW weight is essential for the incredible strength to weight ratio and abrasion resistance of this material, the very extreme MW means that the molecules are so large that heating UHMWPE tends to thermal decomposition before full melting (liquification); and even when melted the molecules are so large as to be incredibly viscous and not easily mixed for molecular entanglement.

    This brings us to your idea of dissolving conventional HDPE to create a glue, which follows the lines of thought using 1) similar molecule type to be the binding agent and 2) solvation vs melting.
    • Yes, conventional HDPE, LDPE and LLDPE can be dissolved, but even these “smaller” PE molecules are so large that they must be heated to almost their melting points in order to obtain solvation. Solvation temperatures ≥ about 100°C are needed.
    • Acetone and other polar solvents are specifically adverse for solvation, because the PEs are so definitively non-polar.
    • Instead, hydrocarbon solvents are useful for dissolving PEs. Xylene is often used in laboratory tests requiring partial or total solvation of PEs. Other hydrocarbons comprising hexane, cyclohexane, and decalin are used for industrial manufacture and fabrication processes for PEs.
    • At home one would likely select xylene as the simplest, safest solvent for dissolving conventional PEs including HDPE, but even that can be hazardous since the needed 100°C is far above the (fire) flash point of xylene.

    Alas, such a solution of HDPE would still not be a useful glue because it lacks any BONDING energy (enthalpy driven) to bind to the surface of the ambient UHMWPE fibers. Yes, the solution could in theory MIX (entropy driven) with the UHMWPE surface, but only if the UHMWPE surface were also liquid, which it distinctly is not — unless heated far hotter than 100°C, and near the point of UHMWPE thermal decomposition.

    How else are conventional PEs bonded to other things such as printing inks and paper laminations, which we know exist as common products?

    Often, this is done by converting a wee tiny bit of the surface of the PE to not-just-PE. Examples follow.

    For adhering printing inks to PE bags, the surface of the PE film is converted into not-just-PE by air oxidation using a thermal or electrical corona treatment of the formed film.  The surface oxidation adds a wee bit of acid, aldehyde and other Oxygen functionally into parts of some of the surface PE molecules; and these molecularly embedded polar moieties then bind with printing inks. A careful balancing is needed for the amount of antioxidant compounds included in the PE, which is needed to protect the extruder and die systems from oxidative fouling and to provide good shelf and service life of the PE film, versus the intensity of the corona treatment needed for film surface oxidation for ink bonding.

    A similar surface (light) oxidation happens with air-stretch-blow-molding of PE for milk jugs, etc. A small amount of surface oxidation provides a weak linkage for applying pressure sensitive product labels. However, peal one of these labels from a PE milk jug and try to stick it to (unoxidized) UHMWPE materials. There will be a slight tack, but not the structural bond that we seek for making backpacking gear.

    Lamination of PE films onto paper, aluminum foil, and other plastics also relies on a slight oxidation of the extruded web of molten PE before being pinched together with the other layer. (More expensive PE copolymers comprising Oxygen functionality (acids, esters, carbonyls, etc.) are used for more difficult lamination applications.)

    This conversion of a very thin surface layer PE to not-just-PE sounds like your musing on cold plasma electrical device. You have hit on a very key concept here!  However, obtaining sufficient and sufficiently uniform partial oxidation of the surface of the UHMWPE fabric to obtain a strongly glued bonding sounds extremely problematic at home. Has it even been done industrially?

    As a practical demonstration of all this theory, reflect that “Cuben” fabrics are a lamination of dispersed (separated) UHMWPE fibers between 2 very thin layers of PET and that the PET layers are not really well bonded to the UHMWPE fiber, i.e., fiber “racking” occurs when laminate structure is stressed on bias.

    Reflect further that the Cuben laminates reached commercial utility about 3 decades ago. If it were commercially “easy” to bond (glue) the UHMWPE fibers on 1-side only, as contrasted to sandwiching between 2 bonded layers of PET (or other) film, some type of “Ultra” would likely have become a commercial reality years ago.

    I wonder how exactly Challenge Sail Cloth has bonded the urethane waterproofing layer to the UHMWPE fabric, but I’ve not dug for patents, and they are likely keeping much as trade secrets.

    Reflect also that there are delamination stories already circulating, even with their “proprietary adhesive”.

    Then reflect that the strength of the bonding of the waterproofing layer to the UHMWPE fabric need not be nearly as strong as would be needed to bond one piece of UHMWPE fabric to another to make a tent or backpack.

    Why not make a UHMWPE that includes comonomers like organic acids, esters, etc. so that gluing is easier? Because no one has found a polymerization catalyst and process technology that can make at reasonable cost the extraordinarily (Ultra) high MWs needed for the exceptional mechanical properties when there is a comonomer other than ethylene.

    In summary, gluing for UHMWPE is extremely difficult both conceptually and practically; but is it impossible? Perhaps not. Conceptually, a very uniform oxidation, sulfonation etc. of the fabric surface might be possible with industrial technology.  Conceptually, melt phase coextrusion of fibers having UHMWPE gel core and a PE copolymer sheath might be possible to form and devolatilize. How else? How else? At what cost (and value vs. other material options)?

    #3769524
    Murali C
    BPL Member

    @mchinnak

    wow! I didn’t know that we had latin speakers on BPL :-) Trying to follow :-)

    #3769525
    Matthew / BPL
    Moderator

    @matthewkphx

    I feel smarter just having read that. Thanks for explaining that, Alan. I’m going to read it a few more times and then maybe I’ll have a follow-up question or two.

    #3769527
    Sam Farrington
    BPL Member

    @scfhome

    Locale: Chocorua NH, USA

    Folks, it is Ult1a High Density Molecular Weight Polyethylene.  Sorry for any mispellings – it is a mouthful.

    I fell into a similar situation by ordering 2.92 oz/sq/yd “Ultra 100” from Extrem Textil; but it is not clear whether the UHDMWPE is the woven fabric or the transparent plastic that is sandwiched over it to make it waterproof.  I liked that it was woven inside, because could sew it; but if it is not bondable, it probably won’t be seam sealable either.  Unless it is the outer material that is not UHDMWPE and can be sealed.  The above weight spec is from Extrem Textil; but maybe I should weigh it myself.  It seems awfully heavy.

    At this point, there are too many ifs, so would not use it for a pack.  It is also more stiff than I would want for a pack.  So will wait until I find out more about it, and in the meantime will use something else for the pack project.  Just one more purchase to roll up, label, and store with the others.  Of which there are plenty, because all the laminated .wonder fabrics I’ve bought have turned out to have issues of one sort or another.  Except the ‘ballistic’ nylon pack that was taken to the Canadian Rockies on a train from Montreal and was almost indestructible.  That did not stop the grizzly bears I met; one of them just patiently sat down and opened up all the pockets and searched the pack for goodies.  How do they do that with such sharp claws?

    Fortunately, I’ve got several simpler woven alternatives that are not laminates, and are almost as light.

    #3769535
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    wow!  thanks for taking the time to write that all up Alan

    hmmm… maybe I’ll just stick to 200D woven nylon for my pack.  I wish it was more waterproof.

    #3769538
    Justin W
    Spectator

    @light2lighter

    Hi Alan,

    Thank you for the excellent holistic, detailed, scientific run down of the issues with bonding to UHMWPE.  I wasn’t aware that HDPE and even LDPE’s needed such a high temp + solvent to liquefy (not that it would matter anyways, as you pointed out).  Sounds like I’m up the creek without a paddle and SOL.  Thankfully I only spent 36 dollars on the material and do have the option for returning it (may just keep it as a material to experiment on).

    Think I will do some experimenting with the fiberglass cloth + silicone + silpoly composites instead and potentially use that as a pack material.  (I have 3 types of fiberglass cloth left over from other projects, a 3.7 oz/yd2 E grade cloth, a 3.7 oz/yd2 S grade, and a 2.1 oz E grade one.  Also have some basalt cloth but that is too heavy and stiff for this purpose I think, plus I’ll be using that for high temp rocket stove etc. builds).

    #3769543
    Justin W
    Spectator

    @light2lighter

    Quick question for Alan. Re: oxidation, could this work at all?   Lightly wipe the surface of the fabric with a quickly evaporating, highly flammable solvent and then ignite it?  Theoretically, it might only damage and lightly oxidize the surface of the fabric?

    (At the very least, it would be somewhat psychologically satisfying… “Burn, burn you material from hell!”)

    #3769544
    Murali C
    BPL Member

    @mchinnak

    Regarding Jerry Adams’s question: I am also curious as to why you cannot add silicone to both sides of 200d nylon and make it waterproof? just like tents etc?

    #3769548
    Justin W
    Spectator

    @light2lighter

    If you can get a 200d nylon fabric that is completely uncoated, you could add your own silicone coating to improve water resistance, but it probably won’t ever be highly waterproof unless you add a lot.  Reason being is that water resistance is not just a function of surface energy/coatings, but also the physical structure of the material itself.  These very large fibers don’t lend themselves to high water resistance in an innate, structural sense.

    You want smaller fibers (but not too small, like microfibers), woven together very tightly and then coated with something like silicone, silicone-PU blend, etc.  There were some excellent posts in the past by Richard Nisley and to a lesser extent, Roger, about the topic of how the structure and weave of the fabric affected HH levels.

    This is why when I will be experimenting with siliconzing fiberglass cloth, I will be bonding it to a silpoly (which will be on the the inner side of the pack), so that it will be more waterproof.  Reason being is that the fiberglass cloth is not nearly tightly woven enough to be a good waterproof fabric (even with silicone coating) by itself.

    #3769550
    YoPrawn
    Spectator

    @johan-river

    Locale: Cascadia

    Since they went with the PU coatings that don’t go yellow and peel with age like before, I think we need to see more of the Gridstop fabrics with PU coatings.

    Whatever Zpacks used on my Arc Haul, is really excellent for both durability and waterproofness.

    I personally think nylon is still the end-all material choice in a lot of cases. It is self-lubricating to a degree and is just plain tough in so many ways, and easy to work with. I have ultralight nylon pants that have something insane like 700+ days of use on them. Countless washes. The only wear they show is fading color. Incredible.

    I have some PU coated rain pants that are also going on many years without fail. The old PU coatings were junk though and would peel in a year or two.

    #3769553
    YoPrawn
    Spectator

    @johan-river

    Locale: Cascadia

    Oh, looks like I wandered to the wrong thread with my post above. Sorry if that was confusing. :)

    #3769590
    Alan W
    BPL Member

    @at-reactor

    Justin, and others:

    UHMWPE is the effectively same as UHMWHDPE (adding HD for High Density) because UHMWPE is inherently in the High Density range (having very low molecular branching, both short chain and long chain, and therefore somewhat denser when solidified) with all practicable chemistry and process technology to date for achieving the Ultra High MW.

    Re surface oxidation, even with continuous, highly reproducible industrial equipment, control of time and temperature and air exposure for air oxidation of the PE layer surface during final product fabrication takes some tuning.  The temperature of PE melt (web, bubble, parison, etc.) first reaching air contact and the subsequent cooling rate of said melt or the intensity and duration of corona treatment are adjusted.   And for stronger surface bonding, one still reverts to using the more expensive PE copolymers having their embedded, much greater Oxygen functionality.

    The intensity of a liquid flash fire method of surface oxidation seems irreproducible, even if every now and then part of the surface finds the “Goldilocks” zone of sufficient oxidation for adhesive surface bonding without damaging the structural properties.

    About fiber glass cloth, remember to consider flexural resistance to fiber breakage, which is not the same as tensile strength or abrasion resistance.

    Is sewing, without gluing or hot bonding, Ultra fabric really so bad compared to the options?

    Importantly, don’t let me or others quench “baby ideas”.  Some of these ideas work in spite of prior beliefs of “experts”.  But do seek to understand the fundamentals in play, as you have done, so that experimental results even of “failures” are better interpreted to enable the next steps – hopefully leaps – forward.

     

    #3769610
    Justin W
    Spectator

    @light2lighter

    Hi Alan,

    Thank you for the follow up reply/info.

    Re: Ultra, I have no issue with sewing. Are you saying that sewing would counter balance the delamination issue that some packs have been having?  I was under the impression that had to do with the basic structure/composite of the Ultra itself and not pack makers using adhesives etc to avoid sewing?  My other issue with Ultra is the expense. The UHMWPE fabric that I bought from Aliexpress was 16 dollars per meter and free shipping. The cheapest Ultra fabric on the other hand, is 48 dollars per yard, and I would need around 2.5 yards. Meanwhile, I already have extra fiberglass on hand from other projects.

    Re: glass fibers/fiberglass cloth, yes, I am very aware of the issue that this material doesn’t have the flexual durability of nylon, polyester, etc fibers. But, I don’t see that being much of an issue in a pack. I’ll probably use a different fabric for the closure/lid part.  I wouldn’t ever use fiberglass cloth for things like clothes, tarps, tents, etc because of that issue.  There is just too much folding, twisting, and general flexing for such items. In comparison, a pack is a relatively static and stiffer structure*.  Plus, I think a thick silicone coating may help a bit, similar to how it helps to improve some of nylon’s strengths–not sure on this though.  It will be bonded and sewn to a silpoly fabric as well, to help with waterproofness and sewing of the overall “composite”.

    * Especially since I am considering building in a stiff frame to the pack via a thinn’ish plywood that I will bond to the fiberglass with a high strength epoxy (and on the other side of the plywood sheet will be a layer of S-glass fiberglass and high strength epoxy).  The rest that will need to flex some, will be siliconized and bonded/sewed to the silpoly (which will go on the inside of the pack) as mentioned above. Due to the combo of thick silicone coating, the stiff back frame, being bonded to another fabric, and the greater stiffness of the fiberglass cloth itself, I expect the pack to be stiffer than the average UL pack (which in my mind, will not only help to prolong the longevity of the fiberglass fibers, but also carry higher weights better if/when needed).

    Cheers and thanks again for your input.

    #3769622
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    “Importantly, don’t let me or others quench “baby ideas”.  Some of these ideas work in spite of prior beliefs of “experts”.”

    Yeah!  and even if the idea doesn’t make sense, maybe it stimulates some other more useful idea

    “These very large fibers don’t lend themselves to high water resistance in an innate, structural sense.”

    I think that’s right.

    I made a pack with Dyneema which has an inner layer that’s waterproof, but it failed after a while.  That inner waterproof layer also has to be strong enough not to fail after a while.

    I am currently using plan B – if it’s hot and I’m sweaty or rainy, I’ll put my polycro groundcloth on the back and bottom inside surface of pack to keep any water away from the rest of my stuff.

    I hate having a second layer that’s waterproof because it adds weight.  Too bad they can’t make a coating for 200d nylon that’s actually waterproof.  For years of use.

    #3769709
    Justin W
    Spectator

    @light2lighter

    Thank you for the encouragement Jerry (and Alan).  Since I’ve decided to keep the UHMWPE fabric as an experimental fabric, I will probably (eventually) run some of the above proposed experiments (such as cold plasma and flame oxidation) and probably on little squares.

    That sucks about the Dyneema (grid?) pack.  Yeah, it would be nice, wouldn’t it.

    What about using a liner made out of .77 oz/yd2 Mountain silnylon?  It wouldn’t add much weight all in all.  I made a tarp out of it and it seems surprisingly strong/durable for the weight.

    #3769712
    Alan W
    BPL Member

    @at-reactor

    Justin, no, I was not opining that sewing might reduce delamination issues.  I was thinking about wanting UHMWPE bonding to another layer of same for structural construction of a pack or tent, like the hot bonding of the outer PET layers of DCF as in some tents made by Tarptent, Durston, Locus Gear, etc.

    In considering how to explain the difficulties of bonding to UHMWPE, I perhaps lost track that you might only be trying to bond a waterproof layer to this extra special PE to make an Ultra knockoff.

    Find some HDPE milk jugs, water jugs, etc. and slowly peel the labels off.  This is the strength of bond that one can expect for a very good adhesive to an oxidized surface of the PE, be it “ordinary” PE or UHMWPE fabric similarly surface-oxidized.  And, these jug labels and bonding are formulated to resist liquids (water, milk, etc.) leaking from an adjacent failed jug, plus a little flexure along its life cycle from factory, filling, transportation, retailing t0 consumer.

    * If one can obtain a similarly nice, uniform surface oxidation of the UHMWPE fabric AND —

    * If one can find a waterproofing layer with good inherent (hydrogen bonding) tack for the oxidized PE surface OR one can find an adhesive tie layer to place between the oxidized UHMWPE fabric surface and some suitable waterproofing layer —

    * Then one might expect to have a usefully bonded (similar to consumer HDPE jug labeling) waterproof coating to turn an UHMWPE fabric into an Ultra knock-off (or improvement!).

    Of course, that inner waterproof layer must also have its own abrasion resistance, even if well bonded to the UHMWPE. (Altogether, not easily or cheaply done: It has been about 30 years since “Cuben” hit the market.)

    Don’t be afraid to look for Challenge Sail Cloth patents for ideas.  (USPTO, EPO, WPO websites.) Though not a lawyer, my understanding is that the purpose of the patent systems globally is to disseminate new technology broadly into the public domain (YEA) in exchange for a LIMITED right of exclusivity for a limited time period (legally agreed trade off).  The LIMITED rights of exclusivity are specifically limited by all terms within each of the allowed claims.  Read ’em and learn, if you are so inclined.

    Best wishes.  Have fun!  I’m headed to trails for the next few weeks and will be off-line mostly.

    #3769715
    Justin W
    Spectator

    @light2lighter

    Appreciate the feedback, but am thinking this is all probably currently above my pay grade (know how) so to speak.

    I hope you have a great trip Alan.

    #3769734
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    yeah, a liner of 0.77 oz/yd2 silnylon might work.  There’s maybe 1 yd2 in a pack so adding 0.77 oz would be insignificant

    the silnylon wouldn’t fail like the inside layer of dyneema

     

    #3769921
    Dan @ Durston Gear
    BPL Member

    @dandydan

    Locale: Canadian Rockies

    Here is some nice bonding to UHMWPE:

    The technology is quite proprietary but I’ll have more to say about it later this year.

    #3769929
    Sam Farrington
    BPL Member

    @scfhome

    Locale: Chocorua NH, USA

    Jerry,

    What I’ve been doing for pack bottoms is using ripstop nylons, 4-6 osy, including inner coating, just for a bathtub pack bottom, with a light silnylon liner sewn inside the pack bottom for added protection.

    The heavier outside material is mostly to deter abrasion, while the silnylon is to insure waterproofness.  All the sealing is on the inside, except for around the top of the bathtub, a few inches high, where there are sewn seams around the top of the bathtub where it joins the pack.

    Although the outer bottom is made of heavy fabric, it doesn’t weigh much because it doesn’t use much fabric.  There have never been any bottom leaks for many years.  Of course, I’ve never set the pack down in a stream where the water could rise above the level of the light pack fabric, usually around 3 osy.

    Note the silnylon inner in the bottom is not bondable to the urethane coated heavier nylon on the outside; so it is just suspended and sewn in place, with the seam sealed on the inside with with a silicone sealer.  There has not been any bunching up of distortion on the silnylon inner, possibly because the sleeping bag in its stuff sack goes in first on the bottom of several stuff sacks that are made to fit snugly, stacked vertically inside the pack.

    I see Dan is really pushing the envelope with the UHMWPE.

    #3769932
    Jon Solomon
    BPL Member

    @areality

    Locale: Lyon/Taipei

    It must be the solvents used in the bonding process that give DCF a large environmental footprint. I wonder if Challenge is developing greener bonding techniques?

    #3771692
    Alan W
    BPL Member

    @at-reactor

    In my post on 2023-01-07, the following is misleading at best and actually inaccurate as stated: “heating UHMWPE tends to thermal decomposition before full melting (liquification)”.

    The crystalline phase of the UHMWPE melts and becomes amorphous by about 120 degC, about the same as the crystalline phase of other variations of PE.

    Anyone who has put flame to UHMWPE cord ends has seen this melting.

    My point more accurately should have said that the Molecular Weight of this polymer is so very great that it does not flow for forming by conventional extrusion and molding fabrication techniques, such as multilayer co-extrusion and film lamination, until the melt is so hot that it is tending to decomposition.  The amorphous melt, without low MW solvent, is simply too viscous owing to the Ultra MW of the polymer.

    However, UHMWPE can be taken from its synthesis solvent and be formed into incredibly slick and tough sheets and other solid shapes by non-traditional fabrication methods using apt combinations of  temperature, pressure and time.

    Sheets of UHMWPE thus formed are so slick and tough that they can be used to line the cones of solids handling bins (silos) for coal, gravel, etc. providing both superior longevity and solids flow properties compared to even the hardest, slickest alloys of steel.

    Back to bonding something to the UHMWPE, here are the options I appreciate, to date.

    * One will need to encapsulate  (wrap around) the UHMWPE fibers, such as with the 2 layers of PET film used in DCF, even though the UHMWPE fibers are not really well bonded to the PET layers (hence “racking” when stressed on bias).  Optionally, a more conventional fabric of UHMWPE fabric that is still loosely enough woven and thus usefully porous might be treated with a waterproof coating that soaks through and encapsulates around the PE fibers.

    * One will need careful control of 3 factors, temperature (enough above crystalline melting, >> 120 degC; but not so hot as to enable bulk fiber flow and/or loss of fiber orientation), bonding pressure, and time, to increase the molecular mobility of the “melted” (amorphous phase) UHMWPE for co-diffusion at a molecular level with another polymer, either another PE (such as bonding a mass of UHMWPE fibers into sheets) or a PE copolymer comprising long segments of PE along with segments of acid, ester, etc. comonomers that can then be used as a tie-layer for bonding to a waterproofing layer, for example.

    * One will need to oxidize (sulfonate, etc.) the surface of the UHMWPE fibers to promote their bonding adhesion to another layer.

    * How else?  How else?  There’s (almost) always another way, sometimes a better way.

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