Equations for UV degradation of condensation polymers
Having spoken to my Chemistry teacher, the idea is that the UV causes the molecules to split; after the fission, the molecules may rejoin or react with 'other radicals' to break the polymer down, hence degrading it.

E.g. for a polyester:

$R_1COOR_2 \xrightarrow{hv} R_1CO\boldsymbol\cdot + R_2O\boldsymbol\cdot$