The Effect of Incorporation of Cellulose Nanocrystal on Polymer Dynamics and Rheological Properties of Polylactic-acid Nanocomposites

Polylactic acid (PLA) is a representative biopolymer with excellent mechanical and thermal properties and its natural biodegradability. The physical properties of PLA can be reinforced by incorporating nanoparticles (NPs), producing polymer nanocomposites (PNCs). In PNCs, the adsorption of polymers onto NPs gives rise to an interfacial layer (IL) with distinct properties from the bulk polymer. The precise control is important for harnessing the enhanced properties of PNCs. However, research on PLA nanocomposites with a focus on their interfacial layer, remains scarce.

In this regard, we investigate the IL of PLA composites focusing on its dynamics and its effect on the rheological properties of PLA composites. Among various NPs used in PLA nanocomposites, cellulose nanocrystal (CNC), an environmentally friendly NP, is considered a suitable filler for producing PLA/CNC composites, while silica NPs were also employed for comparison. CNC showed superior reinforcement in rheological properties than silica NP and significantly slower mobility of PLA chains is found within the IL of PLA/CNC composites. The surface property of CNC with a high aspect ratio of rod-like shape and large surface area readily forms the IL with PLA, ultimately resulting in a remarkable enhancement in mechanical properties.