Chemical engineer. Master's in Precise Organic Synthesis and Bachelor's in Nuclear Chemistry. 7+ years of competitive lab experience - formulation, synthesis, analysis. Managed people. Educated people. Project led. More than 28 finished international and local science projects.
On topic - The process described is called yellowing. It's caused by the UV radiation. There are some chemicals that slow it (most added in the process of manufacture). A coating can be developed, too. Its results will be weaker, due to the sole advantage of binding between UV stabilizer or Optic Whitener and the base of the polymer. The yellowing is unavoidable with time, irreversible and sooner or later all plastics and polymers start to yellow.