Synthetic Yarn Degradation Testing
Ultraviolet light can cause a synthetic yarn to turn to powder. Whether this is a defect or not depends upon how much light the yarn receives and there is no convening authority to determined if this is a defect. However, some expert believe that if a carpet's yarn start turning to powder after 300 hours of AATCC 16E LIGHT (XENON ARC) at testing laboratory, then it is defective. If not then the problem is too much sun light. Below is an example of nylon that has turned to powder in front of a sliding-glass-door.
UltraViolet Light Degradation. This black pair of paints was rubbed on the area of carpet where the degradation was taking place. The white material is degraded carpet fibers.
James Smith has written two reports on this topic: one was considered defective and other was not.