First a bit of general info on paraglider fabric, which you might already know. Then I'll go on to summarize a whole list of things which can do bad things to your wing, and the ways to avoid them.
Parachutes and paragliders share the same type of material, which is Ripstop Nylon.
The reasons for using this material and not some other synthetic cloth is nylon's combination of strength, flexibility, resistance to abrasion and ease of drying. That last one's more important than you might think!
Ripstop refers to how the cloth is woven, where a double or triple thread is used at regular intervals.
This has the effect of making the material bunch up when something tries to cut or tear it. It doesn't make paraglider fabric immune to ripping, but it sure slows it down a lot.
Are you looking for a ball-park figure for the lifetime of a typical canopy? Forget it - it depends so much on the kind of use it gets and the environment in which it is used. Oh, and how well the pilot takes care of it too!
The two major problems with used paragliders are in increase in porosity and a decrease in strength, compared to the 'as new' properties of the fabric.
Porosity just means how fast air can be forced through the fabric. Ideally, none at all should get through.
Strength relates to how well the material resists tearing and stretching. Either one is bad news for a paraglider canopy.
The following factors affect one or both of these problems.
Nearly everyone knows that sunlight is not good for paraglider fabric. In particular, the frequency of light just past the blue end of the spectrum which we can't actually see. This UltraViolet (UV) light component of natural sunlight is the same thing that wrecks the elastic in your underwear when you hang it out in the sun! Just about any synthetic material will degrade when exposed to enough UV. Paraglider fabric suffers with increased porosity and decreased strength.
UV Exposure - Solutions
The most obvious solution is just common sense. Keep the wing packed away out of the sun when it's not actually being flown.
Some manufacturers add UV inhibitors in the fabric coating. Sun-screen lotion for paragliders! I also understand that some manufacturers are now using raw materials that offer increased protection from UV without adding extra weight to the coatings.
Believe it or not, the color of your canopy affects its UV resistance! Apparently Dark Blue is one of the best, while Black and Red also do well. However, wings with florescent colors have been known to fade and degrade quicker than others with exposure to sunlight.
Heavier cloth will age slower from UV exposure than a lighter grade. But who wants a heavier glider?
The problem with sand, dirt and anything else that finds its way into your wing is that it wears away the protective coating. I imagine this would be more of a problem with a laminated coating, as compared to the type which is impregnated right into the nylon fibers.
Ever found bugs crawling around amongst the fabric? Apparently yellow attracts insects more than any other color! Insect remains would also contribute to wear and tear of paraglider fabric if not removed.
Abrasion - Solution
Most obviously, don't drag your wing across the ground. Treading on your wing is a rather silly thing to do as well.
When packing the wing, don't include small twigs, stones, insects or anything else.
As often as you think it needs it, wash the wing. Find somewhere dry and clean, and wet-sponge it down with an olive oil based natural soap such as Savon de Marseille. Using solvents or anything abrasive is not a good idea.
NEWS FLASH - Humidity is worse for paraglider fabric than UV radiation! Strange but true according to at least one manufacturing insider in the industry.
The main problem here is when the wing is packed up in a wet or damp state. The protective coating can then be exposed to higher than normal humidity for a long time. While you're waiting for the weather to improve, your wing is quietly suffering water torture in its bag. The fabric porosity can be affected if this happens.
Moisture - Solution
Ripstop nylon dries quickly, so it's quite feasible to just let a wing dry in the shade. In the sun would be quicker, but have a think about that ;-)
Only store the wing when you can see it's quite dry. Also, store it in a dry cool place with the bag open.
Manufacturers these days are also trying to make things easier for the pilot by using water repellent materials during construction. This should mean shorter drying times.
This can be a significant problem for paragliding operations that are based right on the coastline. Salt in the air and water speeds up the destructive processes if a wing is stored wet.
Salinity - Solution
As for a dirty or dusty wing, washing is the key. A good wash every few months will remove all traces of salt off the fabric.
Unless you live in an un-air-conditioned tin shed in the Sahara Desert, the most likely way to accidentally cook your wing is to leave it in the boot (trunk) of your car. If this happens for enough hours during hot weather, the life of the paraglider fabric will be significantly reduced.
Extreme Heat - Solution
Just common sense - in hot climates, don't make a habit of leaving your wing in the boot!
As with just about every other facet of paraglider construction, the development of paraglider fabric has really advanced over the years. In 2008, wings can be expected to last several times longer than they did in the 90s, if given similar usage in a similar environment.
The coating of the fabric is what makes all the difference. Silicone, polyurethane or a combination of the 2, plus other components are used to treat the raw cloth. The coating doesn't do much for resisting tearing, but it does strongly resist stretching. More importantly, it makes the material airtight, and even contributes to UV resistance with the right additives.
The manufacturers are constantly trying new things and conducting numerous tests on paraglider fabric. For example, there are standard tests which measure
These are useful things to know for any application, however other tests are much more relevant to paragliding in particular. For example, the fabric might be subjected to:
I hope you have found all this information about paraglider fabric helpful for preserving your valuable investment!