Effects of Compatibilizer on Properties of Polylactic Acid Nanocellulose Composites

Polylactic acid (PLA) has attracted much attention due to its degradability, but its stiff and brittle properties and processing instability limit commercial applications. The use of cellulose nanofiber (CNF) to enhance PLA can effectively overcome the above problems, but it also faces the problem of poor compatibility between the fiber and the matrix, and adding a compatibilizer will improve this situation. 
In this paper, the mechanical properties of the composites were studied by adding polylactic acid grafted maleic anhydride (PLA-g-MA) as a compatibilizer.

Figure 1 is a SEM image of the fracture surface of PLA and its composites. It can be seen that the fracture surface of pure PLA is smooth and belongs to brittle fracture; after adding CNF, the roughness of the fracture surface increases, which will help to improve the mechanical properties of the material, but CNF also has serious agglomeration phenomenon; compared with no addition In the composite material of compatibilizer, after adding PLA-g-MA, the agglomeration phenomenon of CNF is obviously improved, indicating that the addition of compatibilizer effectively solves the problem of incompatibility between matrix and fiber.

Figure 2 shows the impact strength of PLA and its composites. It can be seen that the impact strength of the composite PLA/CNF without compatibilizer is lower than that of pure PLA, and the change is not obvious with the increase of CNF addition, indicating that a large amount of CNF has agglomeration phenomenon, the interface strength with the matrix is low, and there is no impact. After adding PLA-g-MA, the impact strength was significantly improved, and the increase was significantly increased with the increase of CNF addition, indicating that PLA-g-MA effectively improved the interface strength between the matrix and the fiber.