Long-term influence of soil environment conditions on the structure and selected properties of PLA packaging

Studies on packaging made of polylactide (PLA) subjected to long-term influence of soil environment conditions have been presented in this paper. The scientific objective of this study was to determine changes in selected properties of the PLA packaging after long-term incubation in soil. These changes were investigated by scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The structure, thermal properties, and disintegration degree of the packaging after their three-year incubation in soil have been discussed. It was found that the PLA packaging did not disintegrate significantly in the soil environment, and slight changes in their structure and lack of significant changes in thermal properties indicate that the efficiency of their degradation in soil conditions after three years is very low. This was mainly due to inadequate temperatures in the soil. It was also found (based on the results of scanning electron microscopy and gel permeation chromatography) that initiation of the biodegradation process took place and that this process is much faster than in the case of conventional non-biodegradable polymers. The results are confirmation that materials obtained of various biodegradable polymers (not only PLA) should be biodegradable only under strictly defined conditions, allocated to a specific type of polymer, i.e. those in which they are easily and quickly biodegradable.