Biodeterioration of plasticized PVC/montmorillonite nanocomposites in aerobic soil environment

The aim of this study was to assess the effect of montmorillonite nanofillers, Cloisite Na+ and Cloisite 30B, on the biodeterioration of PVC-based nanocomposites plasticized by means of dioctyl adipate (DOA), dioctyl phthalate (DOP) and modified poly(propylene adipate) (PPA), in the aerobic environment of soil (soil burial test, time of exposure: 198 days). Tests were carried out at 25 +/- 1 degrees C, under moisture-controlled (55 %) and aerobic conditions. The extent of the biodeterioration process was evaluated on the basis of changes in weight, tensile strength and elongation-at-break values. Finally, analysing chemical structures using FTIR and visual observation, both macroscopic and microscopic via scanning electron microscopy assisted in the evaluation process. The results of this study suggested that plasticized PVC/montmorillonite nanocomposites have an increased susceptibility for undergoing biological deterioration in comparison with plasticized PVC. In each instance, adding Cloisite 30B resulted in reducing the resistance of PVC/montmorillonite nanocomposites to the actions of microorganisms. In the case of Cloisite Na+ as the filler, results cannot be clearly quantified, although a negative influence prevailed, particularly a change in colour, whose change intensity was also dependent on the type of plasticizer, increasing in the following sequence: PVC/DOA/Cloisite Na+ > PVC/DOP/Cloisite Na+ > PVC/PPA/Cloisite Na+. However, each sample containing Cloisite Na+ achieved a lower rate of degradation (by normalised weight loss and FTIR) compared with nanocomposites containing Cloisite 30B. This can be attributed to the migration and accumulation of Cloisite Na+ on the surface of the nanocomposites particles where the former phenomenon producing a surface barrier which caused a reduction in the permeability of the material toward water and microorganisms, during the test.