The environmental factor that most significantly accelerates the degradation of polymeric materials is UV radiation.

- Polymeric materials can degrade due to various environmental influences, including elevated temperature, moisture, mechanical stress, and UV radiation.
- Among these, UV radiation plays a critical role in breaking down the chemical bonds within the polymer chains, a process known as photodegradation.
- This leads to loss of mechanical strength, discoloration, surface cracking, and overall material deterioration.

- UV radiation causes photooxidative reactions that generate free radicals, initiating chain scission or cross-linking in the polymer structure.
- While elevated temperature can accelerate degradation through thermal oxidation, it generally acts as a secondary factor compared to UV exposure when materials are used outdoors.
- Moisture exposure can lead to hydrolysis in susceptible polymers, but many common plastics are hydrophobic and less affected.
- Mechanical stress causes physical damage but does not by itself chemically degrade the polymer at the molecular level.

Therefore, UV radiation is the primary environmental factor responsible for the rapid degradation of most polymeric materials, especially those exposed to sunlight.

Reference: Polymer Science and Engineering, Volume 3, Chapter 12, Page 245