Mechanical and Thermal Properties of PLA Films Irradiated by Ultra Violet Irradiation

Abstract

The degradation of polymers under ultraviolet (UV) irradiation has been a great concern for biomaterial and agricultural applications. The major objective of this study is to examine the effect of UV radiation on biodegradable polylactic acid (PLA), and to understand the mechanisms of degradation induced by radiation. The PLA studied in this work presented in the form of a film of two thicknesses, 100 and 200 μm. The samples are artificially aged under varying doses of irradiation. Study of virgin systems under deferent speeds by tensile drawing showed that Young modulus of the thick films is higher than that of thin films, the thick material loses its rigidity from speed 25 mm/min. Under UV irradiation, at ambient temperature and crosshead speed 12 mm/min, all samples show ductility at the neat state and become rigid for doses over 324 mJ/cm2. The Young modulus increases with the amount then goes down. This is due to the drop in molar mass, confirmed by GPC, induced by scission of macromolecular chains followed by an increase due to recombination of free radicals. The storage modulus and loss factor of PLA were also investigated by DMA, its value is changed for 1300 MPa to 1000 MPa then it increases to 3250 MPa. The information on the functions of the material before and after the irradiation, in particular the degradation and the crystallinity of the biomaterial in question. DSC allowed access to Tg as well as crystallinity before and after irradiation which are correlated with mechanical properties given by tensile test.