𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞 : 𝐔𝐕 𝐃𝐞𝐠𝐫𝐚𝐝𝐚𝐭𝐢𝐨𝐧 𝐄𝐟𝐟𝐞𝐜𝐭𝐬 𝐢𝐧 𝐏𝐨𝐥𝐲𝐦𝐞𝐫𝐬

𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞

𝐔𝐕 𝐃𝐞𝐠𝐫𝐚𝐝𝐚𝐭𝐢𝐨𝐧 𝐄𝐟𝐟𝐞𝐜𝐭𝐬 𝐢𝐧 𝐏𝐨𝐥𝐲𝐦𝐞𝐫𝐬

𝐄𝐟𝐟𝐞𝐜𝐭𝐬 𝐨𝐟 𝐔𝐕 𝐝𝐞𝐠𝐫𝐚𝐝𝐚𝐭𝐢𝐨𝐧 𝐨𝐧 𝐩𝐨𝐥𝐲𝐦𝐞𝐫𝐬 𝐦𝐚𝐲 𝐛𝐞 𝐚𝐬𝐬𝐞𝐬𝐬𝐞𝐝 𝐟𝐫𝐨𝐦 𝐭𝐡𝐞 𝐟𝐚𝐜𝐭𝐨𝐫𝐬 𝐝𝐢𝐬𝐜𝐮𝐬𝐬𝐞𝐝 𝐛𝐞𝐥𝐨𝐰.

Change in chemical structure - Natural weathering is normally an oxidative degradation which produces hydroperoxy, hydroxy, carbonyl groups and cross-linking, which can be detected by IR, UV and NMR spectroscopy.

Change on surface - Most of the oxidative degradation takes place at the surface of polymeric material because oxidative processes are more intense at surface due to greater availability of oxygen and high temperature. Thus, a brittle outer layer is formed on polymer surface due to weathering and with the help of SEM or optical microscopy it can be observed.

Embrittlement - Many oxidative degradation processes cause embrittlement in polymers, which can be easily examined manually.

Generation of free radicals - Almost all the degradation processes are free radical reactions and generation of various types of free radicals can be detected by electron spin resonance spectroscopy.

Change in molecular weight - Reduction in molecular weight due to chain scission processes is commonly observed phenomenon during polymer degradation. Viscosity measurements and GPC are the commonly used techniques to study this aspect of polymer degradation.

 

Loss in mechanical properties - Change in chemical structure and chain scission processes are reflected in the loss in mechanical properties of a degraded polymeric material.

 

Impairment of transparency - This can be observed even manually that transparent polymeric material loses its transparency upon degradation. This is due to formation of different morphology on polymer degradation. This results in heterogeneity in bulk of a polymeric material, which scatters incident light rather than transmitting it. Eventually polymeric material loses its transparency.

The understanding of degradation mechanisms is further complicated by factors such as morphology, diffusion processes and interactions of additives.

source : SpecialChem