Urethane as laminated to form an airtight coating on a (waterproof?) textile fabric might not be the same thing as a stand-alone urethane film, despite the fact that both contain a form of *gasp* urethane.
Actually the same type of urethane is used both for the straight films and the thin films that are glue laminated to textiles.
Are not most conventional BCD bladders made of the laminated urethane coating? Most BCD bladders stand up very well over time, in my experience (though I only ever owned a Scubapro Classic and Knighthawk). I know most Scubapro BCD bladders are laminated urethane coated nylon--my Classic certainly was.
Many BC are made using laminates, and many are made using internal urethane bladders. The single layer laminated inflatables can easily be distinguished by the "taped" external seams. The material beyond the weld line is covered with essentially a piece of ribbon sewn in place. Think lift bag.
BC's with internal bladders and a sewn outer shell have the seams to inside.
I don't at all feel at ease folding hard, to the point of forming a crease, a thicker (and still thicker, thicker than a waterbed in the case of some urethane film bladders) material versus a thinner one.
Heavy gauge urethane is very resistant to such handling. With the proper selection of thickness and durometer folding or rolling is no problem. We've never had a wing returned because somebody folded it too tightly. Impacts cause pinch flats, not folding wings up for transport.
I've folded the urethane we use over and closed this fold in a large *8 inch* bench vise without even leaving a mark on the material.
With some materials, thicker means less pliable and easier to snap or crack or pinch puncture when folded hard (forced flat at the point of the fold). Might this be true of urethane film, say versus laminated urethane coated nylon? I don't know, again, knee-jerk common sense reaction.
Overall, I would say mine is an over-reaction.
Here we agree completely. You made sweeping general statements based on a self admitted limited understanding of the materials involved.
I'm curious, Tobin, which type of inner bladder has a higher manufacture cost, assuming the highest quality of each type?
That depends on a number of factors. The 22 and 30 mil urethane fiilms we use for bladders are custom produced, in other words they are "mill runs" Nobody stocks this material. We buy 1000's of pounds each time.
The laminated materials can have light nylon fabric and a thin ~maybe 5mil film glued to it. These are often available "off the shelf" at a cost per yard less than the heavy gauge pure urethanes and in much smaller quantity.
Something tells me that more is entailed in making the laminated urethane coated nylon bladder and so the cost might be higher.
What's "something"? Have you ever done any RF welding?
The laminating is done by specialty converters, not by bladder fabricators. There's basically no difference in labor to weld a bladder from heavy urethane film vs laminated fabric. It's a bit more work to cut the heavy films and trim the bladders after welding than it is with laminates, but not a huge difference.
If so, what might this suggest about the fact that it appears in so many high-end wings?
10-12 mil urethane films are pretty easy to source. These are often used for BC bladders and other inflatable applications, hydration bladders, etc. Contract BC producers often have these lighter materials on hand.
Does a say a 400 denier nylon with 3-5 ounce per square yard of urethane film perform better than a 10 or 12 mil urethane film in terms of pinch flat resistance?
Yes it does.
Is it better than a 30 mil urethane film? Not in our tests.
Is it easy to source 30 mil urethane's? No, it's sort of a struggle. Thermoplastic films (think trash bags, etc.) are often produced by lofting the melted material on a stream of air. The process is limited by the rate at which the plastic can be melted. This often means heavier gauge materials either cannot be produced or only produced in narrow widths. Took me about two years to convince a mill to even try and blow a wide heavy gauge film.
Is easier to buy 50-100 yards of laminates? Yes because these materials are widely used for other inflatables.
Pinch flats are the result of impacts, typically the corner of the back plate hitting the bench or boat deck with the wing in between, not the result of folding or rolling.
I have no concerns about folding or rolling up any DSS wing.
Tobin
