Experimental Analysis of the Physical Degradation of Polymers – The Case of Polymethyl Methacrylate

Polymers are known to be sensitive to aging; their lifetime can be predicted through experimental tests. This paper displays an experimental study on the long-term performance of polymethyl methacrylate (PMMA) exposed to solar (UV) radiations and artificial (UV) lamp radiations, drinking water and sea water. The performance of this polymer was analyzed in terms of strain variation; strain at break in tension, and Young's modulus. The results obtained showed that the amount of absorbed water is independent of the nature of the solvent, and only the absorption kinetics may be regulated by the species contained in the medium. This seems to indicate that plastification of polymers is a reversible phenomenon. In addition, it was found that the tensile strength and elastic modulus drop with increasing immersion time. Compared with seawater, the absorption of drinking tap water, after 36 months, leads to a non-linear behavior of the polymethyl methacrylate. Exposition of PMMA to artificial (UV) lamp radiations and solar (UV) radiations, for the same duration of exposure, resulted in greater performance degradation when the polymer was exposed to artificial (UV) lamp radiations. In addition, the results obtained after a 19 month exposure period that the artificial (UV) lamp radiations changes the behavior of this material from viscoelastic to viscoplastic