Preparation of gelatinized strach/polylactide blends

Biodegradable polymer blends between gelatinized starches (GS) with polylactide (PLA) prepared at various blends compositions were studied. The effects of starch, plasticizer, and compatibilizer content on the physical, thermal, morphological, and mechanical properties of blend films were investigated. Two types of starches namely tapioca and corn starches were compared; whereas, three types of plasticizers used in the films were glycerol, propylene glycol (PG), and poly(ethylene glycol) 400 (PEG400). In addition, methylenediphenyl diisocyanate (MDI) was used as a compatibilizer to improve the interfacial interaction between plasticized PLA and gelatinized starch phases. GS content was varied from 0 to 40 wt%, while MDI content was differed from 0 to 10 wt% based on the GS content of blends composition. Biodegradation of the blend films was evaluated by soil burial test, and followed by measuring the changes in physical appearance, weight loss, and tensile properties of the films. The results showed that plasticized PLA with 10% PEG400 and GS with 25% glycerol had appropriate physical, thermal, and mechanical properties. The suitable blend composition between gelatinized starches and plasticized PLA (40:60) was the presence of 1.25% MDI, leading to an increase in the tensile properties compared with the film without a compatibilizer due to the interfacial adhesion improvement between two phases, as evidenced by the morphological results. Furthermore, the tensile properties of the films slightly decreased with increasing amount of GS, whereas the biodegradation rates obviously increased. However, the presence of MDI inhibited the biodegradation efficiency of the blend films. These results are in agreement with water absorption isotherm of the films.