Sunlight contains ultraviolet which transform PVC particles to a complex structures with brownish discoloration. The effect of discoloration can be reduced with addition of UV absorbers such as titanium dioxide.
Based on past research results, the impact resistance is affected by sunlight exposure for two years on PVC pipes while there is no effect on tensile strength and pipe modulus. As flexible pipes resist loadings by deformation of pipe, there shall be no impact on the pipe’s load-carrying capacity owing to sunlight exposure. In general, smaller pipes with thin wall are more likely to be affected by sunlight than larger pipes with thick wall. For storage of PVC pipes for a long period, it is recommended to protect them against sunlight by tarpaulin or by painting. For painting PVC pipe, oil and solvent-based paint should not be used as this would dissolve the PVC pipe. Water-based paint should be adopted instead.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
If you have a query, you can ask a question here.