Preparation of modified hydrotalcite based on click chemistry and its effect on the shear induced crystallization, rheological behavior and thermal degradability of poly (lactic acid) film

Abstract

In this work, Zn-Mg-Al-LDHs was prepared by co-precipitation. LDHs-B-OM was prepared with Zn-Mg-Al-LDHs by coupling method and thiol-ene click chemical reaction. The optimum conditions of thiol-ene click reaction were determined by orthogonal experiment as follows: reaction time of 5 h, mass ratio of OM to B-LDHs of 1: 1, mass ratio of LDHs-B to initiator of 100: 9. LDHs-B-OM was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy, scanning electronic microscope, and static contact angle, which showed that its surface modification was confirmed successfully. Then, PLA/LDHs-B-OM films were prepared by blow molding process using LDHs-B-OM as fillers and PLA as matrix. The mechanical properties, rheological properties, and crystallization behavior of PLA/LDHs-B-OM films were studied, which showed that the elongation at break, the tensile strength of PLA0 and PLA4 (0.7 wt% LDHs-B-OM) were 14.20%, 36.47 MPa, 74.09%, and 46.99 MPa, respectively, which demonstrated that LDHs-B-OM had a significant strengthening and toughening effect on PLA. Rheological behavior results showed that LDHs-B-OM effectively promoted the movement of PLA molecular chain. The shearinduced crystallization behavior and thermal degradation was analyzed by simultaneous rheology and FTIR technology, which showed that the carbonyl peak shifted from amorphous region to crystalline phase region. The reason was that LDHs-B-OM acted as a nucleating agent to accelerate the crystallization process of PLA. The carbonyl index reduction of PLA0 and PLA4 before and after thermal degradation was 14.93% and 7.97%, respectively, which provided sufficient evidence that the addition of LDHs-B-OM improved thermal stability of PLA.