Effects of Amino Hyperbranched Polymer-Modified Carbon Nanotubes on the Crystallization Behavior of Poly (L-Lactic Acid) (PLLA)

Abstract

Poly-L-lactic acid (PLLA) is an environmentally friendly and renewable polymer material with excellent prospects, but its low crystallization rate greatly limits its application. Through the amidation reaction between amino hyperbranched polymer (HBP N103) and carboxylated carbon nanotubes (CNTs), CNTs-N103 was obtained. The modification was confirmed by Fourier-transform infrared (FTIR) spectroscopy, X-ray electron spectroscopy (XPS) and thermogravimetric analysis (TGA). Using transmission electron microscopy (TEM), we observed the changes on the surface of modified CNTs. PLLA/CNT composites were prepared, and differential scanning calorimetry (DSC) was used to investigate the crystallization behavior of the composites. The results showed that the addition of CNTs could greatly improve the crystallization properties of PLLA; at the same concentration, the modified CNTs had better regulation ability in PLLA crystallization than the unmodified CNTs. Moreover, in the concentration range of 0.1–1%, with the increase in HBP concentration, the ability of CNTs-N103 to regulate the crystallization of PLLA increased as well. Wide-angle X-ray diffraction (WAXD) once again proved the improvement of the crystallization ability. The results of polarized optical microscopy (PLOM) showed that the number of nucleation points increased and the crystal became smaller.

Effects of Different End Functional Groups Hyperbranched Polymers-Modified Carbon Nanotubes on the Crystallization and Mechanical Properties of Poly(l-lactic acid) (PLLA)

“…According to TGA results, HBP N102 has a lower grafting rate than HBP H202, which also resulted in more carboxyl groups on the surface of CNTs-N102, so it had a better effect on the improvement of the crystallization performance of PLLA. However, previous studies have shown that we can regulate the grafting rate of HBP on the surface of CNTs by adjusting the molecular weight of HBP …”

“…To explore the influence of modified CNTs on the crystallization properties of PLLA, we prepared pure PLLA and PLLA composites with unmodified CNTs, HBP H202-modified CNTs, and HBP N102-modified CNTs, which were named PLLA, PLLA/C, PLLA/C-H, and PLLA/C-N, respectively. In the composites, according to the previous research, we discussed the effect of the concentration of CNTs on the crystallization of PLLA, and the results showed that the 1 wt % concentration of CNTs has the best regularity on the crystallization of PLLA . Therefore, the concentration of unmodified CNTs, HBP H202-modified CNTs, and HBP N102-modified CNTs is 1 wt %.…”

“…In the composites, according to the previous research, we discussed the effect of the concentration of CNTs on the crystallization of PLLA, and the results showed that the 1 wt % concentration of CNTs has the best regularity on the crystallization of PLLA. 23 Therefore, the concentration of unmodified CNTs, HBP H202-modified CNTs, and HBP N102-modified CNTs is 1 wt %.…”

“…However, previous studies have shown that we can regulate the grafting rate of HBP on the surface of CNTs by adjusting the molecular weight of HBP. 23 3.2.2. WAXD.…”