Fantastic banner!
I don't know anything about the league or team.
The silk used for some stuff back into the 1800's had stuff added to stiffen it which isn't good long term. The ones at Yale have probably suffered from years of being displayed.
From a different hobby on the Smithsonian website.
http://www.si.edu/encyclopedia_si/nmah/vicquilt.htm
The part that applies.
"Many of the silk fabrics used in "crazy" quilts are weighted with mineral salts and other substances. This means the fabrics have been coated with, or have actually absorbed, these substances to give them more weight and a stiffer texture. Unfortunately, weighting substances also speed up the fabric's deterioration.
Silk is extremely susceptible to light damage, which can be seen in brittleness, splits, and the eventual powdering of the yarns. Sometimes, even though a piece of silk may appear in perfect condition, it can be extremely fragile. Unfortunately, we know of no way to stop this deterioration or reverse it. We can, however, slow it down by keeping the textile out of sunlight and bright household lighting -- especially fluorescent. If a quilt is to be displayed, it should be protected by keeping the room's draperies drawn, the light level low, and the lighting fixtures placed at a distance from the quilt."
Just swap "banner" "ribbon" etc for "quilt" and it works fine.
Steve B