Have you observed PVC pipes that are attached to the water tank? You might have noticed that the pipes exposed to sunlight lose colour after a while. These pipes will also lose their strength and become brittle. PVC pipes lose hydrogen chloride gas when exposed to high temperatures.
Polymers undergo a change their properties like colour, shape or molecular weight when they are exposed to one or more environmental factors like heat, light or chemicals. This change is known as polymer degradation. It is usually undesirable. However, it is useful in recycling polymer waste. Biodegradable plastics are degraded with the help of microorganisms.
Picture Credit : Google