Plasticizer Enhancement on the Miscibility and Thermomechanical Properties of Polylactic Acid-Chitin-Starch Composites

Abstract

In previous research, a polylactic chitin starch composite was prepared without the use of a solvent to enhance the miscibility. In this study, a polylactic acid (PLA) chitin starch composite was produced with chloroform as a plasticizer in the ratio 1:10. The blending of chitin and starch with PLA ranges from 2% to 8%. Tensile strength, impact, thermogravimetry analysis-Fourier-transform infrared spectroscopy (TGA)-FTIR, and differential scanning calorimetry (DSC) were used to test the thermomechanical properties. Also, the morphological properties, water absorption, and wear rate of the material was observed. The results showed that the tensile strength, yield strength, and impact strength were improved compared to the pure polylactic acid. Also, the elastic modulus of the samples increased, but were lower compared to that of the pure polylactic acid. The result of the fractured surface morphology showed good miscibility of the blending, which accounted for the good mechanical properties recorded in the study. The thermogravimetric analysis (TGA) and derivative thermogravimetric analysis DTA show a single degradation and peak respectively, which is also shown in the glass temperature measures from the DSC analysis. The water absorption test shows that the water absorption rate increases with starch content and the wear rate recorded sample A (92% P/8% C) as the highest. The high miscibility projected was achieved with no void, with the use of chloroform as a plasticizer.

Keywords: biopolymer; composite; extrusion; miscibility.

Figure 1

Tensile modulus and contact angle of samples A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C—92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P.

Figure 2

(a) Tensile properties and (b) Impact strength of samples A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C—92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P.

Figure 3

Scanning electron microscope images for samples with the ratios A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C— 92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P.

Figure 4

(a) Thermogravimetry analysis (TGA) result of samples A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C—92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P. (b) Derivative thermogravimetric analysis (DTA) result of samples A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C—92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P.

Figure 5

FTIR plot of samples A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C—92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P.

Figure 6

Picture representation of the interfacial bonding between polylactic acid (PLA)–chitin and chitin–starch.

Figure 7

DSC plot of samples A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C— 92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P.

Figure 8

(a) Wear and (b) water absorption properties of samples A—92% polylactic acid (P)/8% chitin (C); B—92% P/6% C/2% starch (S); C— 92% P/4% C/4% S; D—92% P/2% C/6% S; E—92% P/8% S; F—100% P.