Biodegradable nanocomposites based on the polyester poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and layered silicate or expanded graphite

Novel nanocomposites based on the biodegradable polymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx) and layered fillers, specifically layered silicate (clay25A) and expanded graphite (EG), were prepared by melt intercalation. The dispersion of the fillers in the PHBHx was characterized by wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The effects of the fillers on the polymer structure, thermal stability and mechanical properties of the nanocomposites were also studied, by differential scanning calorimetry, thermogravimetric analysis, and strain-stress measurements in elongation, respectively. The WAXD and TEM results showed that the clay25A and EG was exfoliated into well-dispersed sheets in the polymer matrix, especially when the filler concentration were relatively low. This gave rise to considerable improvements in Young's modulus, and resulted in increases in the thermal degradation. It should be possible to convert the EG dispersions obtained thus far to ones yielding filler-filler networks that show electrical conductivity.