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Depending upon substitution, the UV absorption spectrum is changed to match the application. Concentrations normally range from 0.05% to 2%, with some applications up to 5%. Frequently, glass can be a better alternative to polymers when it comes to UV degradation. Most of the commonly used glass types are highly resistant to UV radiation ...
Polypropylene, a common material in our everyday environment, is a very significant example of this approach. Its chemical structure where many tertiary carbons are present (bound to three carbon atoms and only one hydrogen) makes it a particularly sensitive material to ageing.
UV damaged polypropylene rope (left) and new rope (right) UV degradation is one form of polymer degradation that affects plastics exposed to sunlight. The problem appears as discoloration or fading, cracking, loss of strength or disintegration. The effects of attack increase with exposure time and sunlight intensity.
The protection of food from photodegradation is very important. Some nutrients, for example, are affected by degradation when exposed to sunlight. In the case of beer, UV radiation causes a process that entails the degradation of hop bitter compounds to 3-methyl-2-buten-1-thiol and therefore changes the taste. As amber-colored glass has the ...
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene . Polypropylene belongs to the group of polyolefins and is partially crystalline and non-polar .
Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate): A primary antioxidant consisting of sterically hindered phenols with para-propionate groups. Primary antioxidants (also known as chain-breaking antioxidants) act as radical scavengers and remove peroxy radicals (ROO•), as well as to a lesser extent alkoxy radicals (RO•), hydroxyl radicals (HO•) and alkyl radicals (R•).
For example, the PVC eliminates HCl, under 100–120 °C. CH 2 (Cl)CHCH 2 CH(Cl)→CH=CH-CH=CH+2HCl Side group elimination can also proceed in a radical manner. For instance, methyl groups in polypropylene are susceptible to homolysis at high temperatures, leaving radicals on the polymer backbone. [6]
Polymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition.Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. [1]