Poly(lactic acid)/Functionalized Silica Hybrids by Reactive Extrusion: Thermal, Rheological, and Degradation Behavior

In the present work, poly(lactic acid) (PLA)/functionalized silica hybrids were prepared via reactive extrusion and their thermal, rheological, and degradation properties were investigated. The PLA was blended through reactive extrusion with functionalized silica, where silica network was formed by grafting-condensation reaction with tetraethoxysilane (TEOS) and (3-glycidyloxypropyl) trimethoxy-silane. The chemical structure and morphology were investigated by Fourier-transform infrared spectra, energy dispersive X-ray spectroscope and field-emission scanning electron microscope. Also, thermal, rheological properties and degradation behavior were measured. The glass transition temperature of the hybrids tended to decrease with increasing TEOS contents, while the degrees of crystallinity increased to about 57% according to TEOS contents. The complex viscosity and storage modulus of PLA/silica hybrids were enhanced clearly compared to that of neat PLA. While the molecular weight of pure PLA was decreased about 12% during processing, the decrease was smaller as less than 10% by the addition of TEOS. The eta(0) (zero-shear rate viscosity) using the Cross model was more than doubled by introducing TEOS. The resistance of hydrolysis was also improved as a result of the addition of silica network. In conclusion, the hybridization of PLA and silica network influenced the thermal and rheological properties, by which it may be possible to apply for various manufacturing process such as foam molding and blow molding, etc.