Chemical combination of nano-silica and alkaline lignin for property enhancement of polylactic acid-based composite films

As a key byproduct from alkaline pulping industry, alkaline lignin (AL) exhibits tremendous potentials for the development of high-value-added biomaterials, ascribed to its renewability and unique polymeric structure. In this study, the alkaline lignin was first oxidized and then modified with aminated nano-silica. After further hydrophobic modification with a silane coupling agent, a novel lignin-based filler was finally prepared and applied for property enhancement of PLA-based composite films. As revealed from SEM results that, a uniformed state of filler distribution could be achieved if the filler content is no more than 1%. Under this condition, the thermal stability of composite film could be effectively improved, as well as the enhancement of tensile strength (50.7 MPa) and Young's modulus (2847 MPa). Notably, the composite films also exhibit selective resistance against UV lights rather than visible lights, especially at higher filler content.