SMKS nanoparticles were prepared by the sol–gel technique using TEOS as silica precursor and G-silane as surface modifier. This silica shell on the surface of kaolinite with many silanol groups greatly promoted silylation of kaolinite. The PHBHHx composite filled with a low loading of SMKS showed an increase in the tensile strength and
toughness from 18.2 to 23.5 MPa and 2.6 to 4.2 MPa respectively. These strong improvements in mechanical properties were attributed to the more finely dispersed SMKS nanoparticles into the polymer matrix and to covalent interactions between the polymer chains and the modified surface of SMKS nanoparticles. TEM images confirmed that SMKS nanoparticles were well dispersed in the PHBHHx matrix. SEM observations of fracture surfaces indicated that samples filled
with SMKS had a rough surface and became stress whitened compared
to control samples.