Influence of aqueous environments on the stability of modified polylactide materials

The effects of fillers of different nature (chalk and native starch) and plasticizer (epoxidized soybean oil), their concentration, and process temperature on the patterns of water absorption of polylactide materials were investigated. Based on the obtained data, the diffusion coefficients of water in polylactide composites and the activation energy of the diffusion process were determined. It was found that the equilibrium water absorption of the developed materials is relatively high and equals to 3–5 wt.%, regardless of the nature of the additives, while an increase in water temperature leads to an increase in water absorption values. It was established that the process of water absorption of materials based polylactide filled with starch occurs faster and requires less energy to activate the process. Based on the results of infrared spectroscopy, a shift of the typical absorption bands of polylactide starch-containing materials was revealed, indicating the presence of intermolecular interactions in the system. The stability of the developed polylactide materials in acidic and alkaline water environments was determined; in particular, it was found that in an acidic environment, starch-containing materials demonstrate a reduced rate of degradation compared to an alkaline environment. At the same time, in an alkaline environment, the destruction of samples occurs with high values of weight loss, regardless of the composition of the composite. Alkali concentration affects both the rate of destruction of composites and the maximum values of weight loss, especially for composites with a small amount of filler.