Rayon fibers can be weakened by chlorine bleach. Undiluted bleach should never be applied directly to the fibers. Dilute solutions can be used safely on rayon or cellulosic fibers for stain removal and whitening. However, even dilute solutions will weaken fibers causing them to rip and wear out if used too often.
Extremely high temperatures when ironing can scorch cellulosic fibers. The scorching or yellowing occurs as the fibers begin to burn. Burned fibers cannot be revived.
Specific questions? Just ask here.