A new application of biosurfactant for the preparation of polycaprolactone/layered silicate nanocomposites

In this study, by using the biosurfactant as the clay modifier, one first attempted to prepare polycaprolactone (PCL)/montmorillonite nanocomposites via a melt-blending method. The production of biosurfactant (surfactin) and the modification of clay proceeded simultaneously by the incubation of Bacillus subtilis CWS1. The evidence for the formation of intercalated/exfoliated nanocomposites was assessed by X-ray diffraction spectroscopy, scanning electron microscopy, and transmission electron microscopy observations. The conclusions were also supported by the result of dynamic mechanical thermal analysis, thermogravimetric analyzer, and differential scanning calorimetry. As a result, the modified clay can be well dispersed into the PCL matrix in nanoscale sizes, because the biosurfactant is partially compatible with PCL chains intercalating into clay layers. As for mechanical properties, a marked increase in tensile strength and Young's modulus can be observed when the biosurfactant-pretreated clay was used to replace the neat clay for the preparation of nanocomposites. Based on the considerations of thermal and mechanical properties, it was also found that 10 wt% of clay content was optimal for the preparation of nanocomposite.