GreenLake wrote:I know standard sailcloth uses fillers, mainly to make the cloth stiffer; presumably they also add to the UV resistance, but I couldn't find anything definite on that. For laminate sails, they definitely add coatings to reduce the effects of UV exposure on the fibers. I imagine none of that is done for parachutes.
Correct: the Nylon fabric of a parachute canopy will undergo hundreds if not thousands of, frankly, quite violent openings during it's typical lifespan (even a "normal" opening, while quite non-injurious to the jumper, is hell on the canopy). The only treatment that really works with any degree of success is a silicone impregnation of the fabric, as well as heated calendaring (flattening of the fibers, thereby reducing the air space between them) that is used to make the zero-porosity fabric common on main canopies today. Being ZP makes the airfoil more aerodynamically efficient. All that does nothing to combat UV tho. But as far as any external coatings? Fuhgeddabouddit! They come off within the first few deployments. That's why any sort of graphics or art/logos done on canopies have to be either more fabric sewn on/appliqued (a very tedious, expensive process, as you have to account for all the seam allowances between cells), or large-format dye sub printing, which is also very expensive, but showing a lot of promise. Screen printing is right out!
But again, the upside is that that canopy only sees about 2-5 minutes of direct UV exposure each jump. Unless the user is an idiot who packs it in the direct sun, or leaves it in their trunk all the time!
Now, paragliding canopies, which don't go through a deployment every time they're used, but spend a lot more time in the sun, are another story, and they are making huge advances with those things.