Three new tetra-Schiff bases were synthesized and characterized to be used as photostabilizers for poly(vinyl chloride) (PVC) films. The photostability of PVC films (40 μm thickness) in the presence of Schiff bases (0.5 wt %) upon irradiation (300 h) with a UV light (λmax = 365 nm and light intensity = 6.43 × 10-9 ein∙dm-3∙s-1) was examined using various spectroscopic measurements and surface morphology analysis. The changes in various functional groups' indices, weight and viscosity average molecular weight of PVC films were monitored against irradiation time. The additives used showed photostability for PVC films, with Schiff base 1 being the most effective additive upon irradiation, followed by 2 and 3. The atomic force microscopy (AFM) images for the PVC surface containing Schiff base 1 after irradiation were found to be smooth, with a roughness factor (Rq) of 36.8, compared to 132.2 for the PVC (blank). Several possible mechanisms that explain PVC photostabilization upon irradiation in the presence of tetra-Schiff bases were proposed.
Keywords: Schiff bases; atomic force microscopy; functional group’s indices; irradiation; photodegradation; poly(vinyl chloride); viscosity average molecular weight.