PVC, Vinyl and Polyurethane Comparison

Scientific opinion? Wrong place.

First, what's the difference between vinyl and PVC?

Second, the resistance to memory and tangling has as much to do with the inner core and how it is constructed as it does with the outer coating.

Finally, the resistance to twist and tangle are dependent on the stiffness/rigidity of the outer coating.

Because PVC and "vinyl" are by nature rigid they must include plasticizers to impart some flexibility. These can be problematic.

Based on my knowledge of polymers, I'd go with polyurethane.

To actually give an informed answer would require far more detail on your part and lots of research.

Lyn----Thank you for your reply. Not being a trained scientist, I can only give you anecdotal information. The cores of braided nylon, dacron or spectra are quite limp and don't tend to twist or coil on their own. Don't know what happens once they are encased in a polymer coating. My educated guess on construction is that in a .032 diameter running line, the core makes up half of the diameter and the coating the other half. This estimate is derived from my experience in stripping the coating from the core. Any further input from you is appreciated. Regards, Capt. Bob

As a part-time novice fly fisher I'm glad you guys are always looking!

Especially us amateurs need all the help we can get

These guys make a good case for PVC...but there certainly is a lot more to it then just coating the line...

http://www.sexyloops.com/manufacturers/rioproducts.shtml

http://americanangler.com/gear/cooking-up-some-lines

Although both articles are somewhat non-technical as far as polymer science is concerned, the specific characteristics needed to make a good fly line are what's important. That's where I fall short in the knowledge department.

Speaking strictly from a durability standpoint, urethanes will win most every time, whether thermoset (generally two part, heat cured, doesn't soften when re-heated) or thermoplastic (gets soft when re-heated).

Not sure that in this case durability is the major attribute needed in the line.

Different sample materials and testing is the only way to know for sure.

Sounds like an interesting project.

Vinyl and PVC or polyvinyl chloride are all pretty much the same thing. Depending on the softening agents and other goo a polymer scientist can go from something fairly soft and clear like shower curtain bags to the white hard PVC plumbing you see at your hardware store. So, you should be asking your supplier of vinyl base stock about the effects you should be working toward and the additives needed to meet your needs. Note: over time vinyl releases the chemicals that gives it, its characteristics. Think about the once clear, soft, pliable vinyl windows in tent and camper windows that eventually turned cloudy and brittle. Also under right or wrong, depending on your perspective, vinyl can turn to goop, think of the soft pliable fishing lures in your tackle box that ended up melting into the trays where it laid, and may end up doing some real damage to the fishing reels your proposed line would go on to. Can you say "customer complaints" and "warranty service" issues? This depends on the quantity and type of additives mixed into the vinyl during extrusion. Next PU is an entirely different animal. It is a very popular polymer used for making products that must be tough, long lasting and resilient. Think automotive body parts, drive belts in high temperature service areas, solid fork lift tires, and specialized shock absorbers. As with PVC/vinyl, there are many, many variations of PU to use for your product with different characteristics. Check with Bayer and their PU lines. PU is a lot more expensive that PVC Nylon can be formulated to do a lot of different things, so check with your supplier for ideas. As with PU, Nylon is also expensive when compared to PVC. Another alternative is PET. I don't have a clue as to how it would react on a nylon base. Again, formulation can have a lot of impact on the performance. One major issue that could work in your favor with PET is the issue of recycling. If you can find a happy blend of recycled PET and agents on your nylon line, you may be able to advertise the line as an eco friendly product. So, there are issues that can work for you here, too. Good luck.

which would resist coiling and tangling most effectively?

The more flexible the line is made the more it can tangle but the less coil memory it would have. Same can be said if we make it more rigid it would have more coil memory and tangle less.

All this is being control with proprietary plasticizers to get an even balance between the two. To also lower the coefficient of friction of the covering so it shoots thru the guides with more ease. To increase weather resistance.

If you are looking for a coating I would look at PE. Lighter then the others so you may not have to induce air bubbles to get the line to float. Lower coefficient of friction, Blends well with teflon which is flexible which would reduce the coefficient of friction even more.

I wasn't aware that PE blends well with teflon, or at all.

Have I missed something?

And Nylon is only soluable in hexafluoroacetone sesquihydrate, as far as I know, so altering the viscosity may be tricky.

Some where I was looking at coatings one was blend of PE AND PTFE. See if I can find it.

As a engineer with a mechanical rather than a chemical orientation I view your question as fairly unrelated to your problems. The plastics you mention are all appropriate for the application, the differences small.

Nylon is not mentioned but probably for good reason. Expense and difficulty in extrusion. The possible gain in performance I would expect to be small.

In terms of the line memory problem. The origin of this problem lies with the setting of the polymers, primarily those of the coating. The core is as you mention by design rather random in the expression of stresses. The coating whether thermoset or thermoplasitic requires time to fully set. In extrusion production there is no time, product must be spooled very shortly after production.

Spooling on large drums especially tapered core vertical drums or bobbins are proven techniques from the weaving industry that could be easily adapted to your production.

Stress reduction techniques are typically thermal or mechanical or vibratory.

For thermal stress reduction running the fresh line through a very cold very light oil bath before spooling would be a easy and probably effective approach, especially for thermoset coatings. A very cold water oil emulsion could be environmentally appropriate and cold enough to be effective.

Mechanical stress reduction techniques would involve stretching and or stretching and relaxing the line as part of the respooling operations that must be necessary as a part of your packaging operations. Here - do some testing, my expectations for the usefulness of this approach are low, but testing the concept is so simply why not find out.

Vibratory methods are seldom used but are often highly effective and energy efficient. Basicly you would take a initial spool ready for pachaging and shack the living crap out of it on a vibratory machine. This is the bulk approach. A continuous process approach would involve drawing the line being respooled through a vibratory "bath". The bath would consist of typically ceramic polishing media in a vibratory drum. I would test this method first. It is simple, inexpensive, and likely to work. Keeping the media clean by continuous washing will prevent dirty looking product problems if you choose this method for full production.

Finally, you could attempt to solve this problem at its roots by radically altering the coating extrusion process. The transformation of the limp core to the stiffer coated product is due to the adhesion of the coating to the core created during the final extrusion process. Extruding the coating as a tube with the core enclosed would increase the buoyancy of product, eliminate most memory problems and only reduce the strength of the line slight.y.

You would have to convert your production process from a coating die to a lamination die and convert your finishing stage from extrusion to pull-trusion. Your company would be extruding the coating around the core and some air and then stretching the product while it cools around the air/braided core in order to reduce the diameter of the coating to the point of moderate contact/adhesion to the braid. I would expect this to be a difficult process to perfect but you would have a unique product that could offer superior performance in this market. A good friend of mine is a engineer with significant experience in exactly this type of extrusion. His e-mail is <email removed>