Which type of pipe is not suited for exposure to ultraviolet rays?

The type of pipe that is not suited for exposure to ultraviolet rays is PB (polybutylene). PB pipes are sensitive to UV radiation, which can degrade the material and compromise its structural integrity over time. This exposure can lead to brittleness and eventual failure, making PB unsuitable for applications where direct sunlight or UV exposure is likely.

In contrast, other materials like iron, PVC, and concrete have varying degrees of UV resistance. For instance, PVC is often used in plumbing and irrigation systems specifically because it can withstand UV degradation better than PB, while concrete does not get significantly affected by UV rays in the same way. Iron, although it can rust, is not as directly impacted by UV exposure in terms of structural performance. Each of these materials has its own characteristics that lend them to different applications in environments where UV exposure might be a factor.