Viscoelastic behavior and crystallization property of poly(lactic acid)/silica nanocomposite

Abstract

The rheological properties of poly(lactic acid)/silica nanocomposite are important to practical industry application, but little research is available regarding this field. In this study, SiO2 nanoparticles were first surface-modified by silane coupling agent KH570 and then melt blending with poly(lactic acid) in a twin-screw extruder to prepare poly(lactic acid)/SiO2 nanocomposites. The effect of the SiO2 content on the viscoelasticity of the nanocomposites was studied. The results showed that the complex viscosity of the nanocomposites decreased with the addition of the SiO2 nanoparticles. The storage modulus was enhanced and the loss modulus was weakened at low frequencies. Both the critical strain and modulus depended on the content of the nanoparticles. The good dispersion of the SiO2 nanoparticles in poly(lactic acid) matrix was identified from field emission scanning electron microscopy. The dispersibility was improved after surface modified by KH570, in comparison to the original nanoparticles. The crystallization property analyzed by differential scanning calorimetry indicated that the presence of the SiO2 nanoparticles had effect on the crystallization behavior and the crystallinity ( Xc) of poly(lactic acid)/SiO2 nanocomposites. The Xc of the nanocomposites was bigger than those of pure poly(lactic acid), since the SiO2 nanoparticles dispersed in poly(lactic acid) matrix served as a nucleating agent.