Changes of carbonyl and vinyl index of three plastics by outdoor exposure

Abstract

Three polymer types [low-density polyethylene (LDPE), polypropylene (PP) and expanded polystyrene (EPS)] were exposed to outdoor sun light in Korea for 12 months. The exposed polymers were sub sampled in every month and measured the carbonyl index (CI) and vinyl index (VI) which used to characterize the degree of photo-oxidation of polymer by FTIR-ATR. The CI and VI of PE showed a linear increase with UV exposure duration from 1.8 to 16.5 and 0.006 to 0.101, respectively. The CI of PP also increased, but has a jagged graph shape and the VI rapidly increased, reached a plateau after 3 months. In EPS, the CI increased until it reached at about 3 months (1.97), and then slowly increasing again. The VI of EPS increase to until it peaked at about after 6 months (2.67) and then slowly declined. When CI and VI was compared between outdoor and laboratory exposure, amount of outdoor sunshine is approximately 24% of UV chamber’. So the CI of PE (11.6), PP (0.76) and EPS (3.63) and VI of PP (0.16) and EPS (2.67) expose to UV in chamber for 4 months was similar to those (16.5, 0.70 and 2.97 for CI, and 0.13 and 2.33 for VI, respectively) in outdoor for 12 months. However, VI of PE exposed for 12 months in outdoor was 3.9 times higher than those in UV chamber for 4 months. CI and VI could be applied to field sample to assume that the degree of weathering of them in environment.l index (CI) and vinyl index (VI) which used to characterize the degree of photo-oxidation of polymer by FTIR-ATR. The CI and VI of PE showed a linear increase with UV exposure duration from 1.8 to 16.5 and 0.006 to 0.101, respectively. The CI of PP also increased, but has a jagged graph shape and the VI rapidly increased, reached a plateau after 3 months. In EPS, the CI increased until it reached at about 3 months (1.97), and then slowly increasing again. The VI of EPS increase to until it peaked at about after 6 months (2.67) and then slowly declined. When CI and VI was compared between outdoor and laboratory exposure, amount of outdoor sunshine is approximately 24% of UV chamber’. So the CI of PE (11.6), PP (0.76) and EPS (3.63) and VI of PP (0.16) and EPS (2.67) expose to UV in chamber for 4 months was similar to those (16.5, 0.70 and 2.97 for CI, and 0.13 and 2.33 for VI, respectively) in outdoor for 12 months. However, VI of PE exposed for 12 months in outdoor was 3.9 times higher than those in UV chamber for 4 months. CI and VI could be applied to field sample to assume that the degree of weathering of them in environment.