Study of PBAT Photostabilization with Ultraviolet Absorber in Combination with Hindered Amine Light Stabilizer and Vitamin E, Aiming Mulching Film Application

Abstract

This work evaluated two combinations of additives, i.e. “carbon black and hindered amine light stabilizer (HALS)” and “carbon black and vitamin E” to prevent photodegradation of poly(butylene adipate-co-terephthalate) (PBAT) aiming its application as mulch films. A 22 factorial rotatable central composite design (α = 1.414) with three central points was conducted. Five different concentrations for each additive were used (0.1, 0.5, 1.0, 1.5 and 2.0% in mass). The formulations were exposed in an environmental simulator to radiation and condensation cycles. The both combination did not avoid the gel formation but its action reduced PBAT chain scission process during photodegradation. Nevertheless, comparing the two different combinations with carbon black, HALS additive was more efficient than vitamin E to minimize the reduction on tensile strength and elongation. The chain scission and crosslinking processes were evaluated by chain scission distribution function. The chain scission was the predominant process during photodegradation of pure PBAT and it was possibly favored by hydrolysis during condensation cycles in the accelerated aging test. It was verified that higher concentrations of carbon black in the formulations led to a reduction on light transmission in both experimental designs. Considering the responses of studied factors on mechanical properties and light transmission it was possible to identify the most promising formulations for application in mulch films, which correspond to 1.5% (weight) for each additive.