Rayon loses much of its strength when it is what?

Rayon is a semi-synthetic fiber that is known for its soft texture and vibrant color, making it popular in the textile industry. However, one of its significant weaknesses is that it loses a considerable amount of its strength when it becomes wet. This is due to the structure of rayon, which is derived from cellulose fibers. When wet, the hydrogen bonds that help maintain the structural integrity of the fibers become weakened, causing them to be less durable and more prone to damage.

In contrast, the other options, while they may pose threats or limitations to rayon, do not have the same immediate and drastic effect on its tensile strength. For example, exposure to sunlight can lead to fading but does not inherently weaken the fiber's structural integrity as significantly as moisture does. Worn fibers can become frayed or thin over time, but this is a gradual process. Stretching can also affect the appearance or immediate feel of the fabric but does not lead to an acute reduction in strength when compared to the impact of moisture.