Accelerated photodegradation of poly(lactic acid) with weathering test chamber and laser exposure – A comparative study. (July 2019) - Litauszki, Katalin
Abstract: This study presents the comparative study of two different accelerated aging methods of poly(d -, l -lactide acid) (PLA). One is the well-known and widely used accelerated weathering chamber. The other procedure is photodegradation with a homogenized laser beam, which has not been used for the artificial aging of biopolymers so far. The film sample was artificially aged with a xenon test chamber for 200 h, with an acceleration factor of approximately 7:1. We also performed a comparative artificial aging test using a krypton-fluoride (KrF) excimer laser in a way that the amount of energy transferred by the laser is the same as the energy transferred by the xenon lamp; the acceleration factor of the laser is higher than 42000:1. The resulting two types of photodegraded film products were compared and broadly characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), gel permeation chromatography (GPC) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR); the goal was to create comparison and possible conformity between the two methods to achieve higher acceleration factor for accelerated aging. Highlights: Accelerated photodegradation of poly(lactic acid) via a xenon test chamber and via a homogenized laser beam were compared. Laser treatment can increase the acceleration factor considerably. The measured degradation of laser treated samples goes beyond the 200-h xenon test result. After laser treatment, amorphous poly(lactic acid) was able to go through cold crystallization. The effect of absorbed laser energy on the number of chain scissions can be described with the equation y = 0.0006x+0.0897.