Photodegradation testing, polymers

The need for fundamental and applied research on lifetime under service conditions is great. As a result, the subjects of dielectric breakdown, fatigue, wear, creep, fracture, oxidation, photodegradation, additive migration, etc., are increasingly important to the eflFective use of synthetic polymers. The development of a scientific basis for tests that predict accurately the useful service life is a primary need. 

Outdoor weathering is undoubtedly the most valuable test of practical polymer stability because of the extreme complexity of the natural conditions. Indeed, though photodegradation is initiated by light, ambient temperature, humidity, rainfall and atmospheric contaminants all have an influence on the course of the degradation, and the interrelationship of these factors is not yet fully understood. Several chemical reactions, the relative importance of which are dependent on the weathering conditions, usually contribute to the failure of the sample. 

Preliminary work ( 5, 18) in this laboratory and at JPL indicates that the residual monomer can play an important role in photodegradation. (We can test the presence of residual monomers using the technique of fluorescence depolarization described before.) Thus, it is desirable to find new meterlals and new schemes of attaching these dyes in or into the polymer to increase the stability and the Stokes shift (e.g., by using well-known techniques such as dimerization). Finally, an interesting problem which we plan to pursue is related to the physics of efficiency limitations can one approach (or perhaps even overcome ) the so-called thermodynamic limit ... 

D Aquino CA, BalmantW, Ribeiro RLL, Munaro M, Vargas JVC, Amico SC. A simplified mathematical model to predict PVC photodegradation in photobioreactors. Polym Test 2012 31 (5) 638-644. 

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