Surface modification of polymers. IV. UV initiated degradation of polymers with stabilizers grafted onto the surface

Polypropylene (PP), Polyethylene (PE), and polystyrene (PS) films were grafted with glycidylmethacrylate in thin surface layers. To the oxiran groups thus grafted onto the surface three UV stabilizers were attached, 4‐amino‐2,2,6,6‐tetramethylpiperidine (AP), 2,4‐dihydroxybenzophenone (DHBP), and phenyl 4‐aminosalicylate (PAS). The amount of stabilizer grafted onto the surface varied between 25 and 40 nmol/cm2 depending on the polymer substrate. The samples were exposed to UV radiation in air, and the degradation and oxidation of the polymers were studied with IR, UV, and ESCA spectroscopy and by stress–strain measurements. PP grafted with AP exhibited a near 20‐fold increase in lifetime compared with the unprotected PP, AP did not stabilize the PE or PS samples. DHBP was an efficient stabilizer of PE, the oxidation rate of the grafted sample being 1/2 to 1/3 of the ungrafted. A similar effect was observed when DHBP was grafted onto PP and PS. PAS underwent a rearrangement reaction when irradiated with UV light, and had only a slight stabilizing effect.