Degradation of Polylactide–Polyethylene Blends in Aqueous Media

Abstract

Film samples of 30 : 70, 50 : 50, and 70 : 30 (wt %) polylactide–low-density polyethylene blends and of the pure components were prepared and studied. Polylactide and polyethylene absorb water weakly (about 2%), whereas the water absorption by the blends was higher, 4–8%. The thermal characteristics of the samples before and after the action of distilled water and a sodium chloride solution were determined by differential scanning calorimetry. After keeping in water at 22 ± 2°С for 10 days, the thermal characteristics of polyethylene in the blend do not change noticeably, the melting point of polylactide decreases by 1–3°С, and its degree of crystallinity increases by 3–4% for all the samples. The action of distilled water and a sodium chloride solution on the polymer blends leads to changes in the intensity of the structure-sensitive absorption bands of the samples at 3000–2800, 1740, and 1300–900 cm–1. The hydrolytic degradation of polylactide for 120 days results in appearance of pores of 170–230 nm size, detected by atomic force microscopy.