Monitoring of degradation of starch-based biopolymer film under different composting conditions, using TGA, FTIR and SEM analysis

This paper presents the results of a composting lab-scale test carried out on Mater-Bi® film, a starch-based biopolymer. The test material is composed by starch, additives and polybutylene adipate terephthalate (PBAT). The test lasted for 45 days and was developed in three replicates under different temperature and moisture conditions, with the aim to assess the influence on Mater-Bi® degradation of less favourable composting conditions as short thermophilic phase, absence of moistening, and a combination of the two factors. The chemical nature and the morphology of the material and of its single components have been investigated before, during and at the end of the composting process, by means of different analytical techniques. ThermoGravimetric Analysis (TGA) allowed to obtain activation energy and weight loss; Fourier Transform InfraRed spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were used to study changes in the polymeric and morphological structure, and visual analysis provided information on the size of the Mater-Bi® particles. The results show that the biodegradation of PBAT is strongly influenced by the environmental conditions (temperature and moisture); on the contrary, in all the three replicates, both starch and additives are completely biodegraded within the first days of the process.