Pyrolyzed Biomass Filler for PLA-Based Food Packaging

Abstract

Poly(lactic acid) (PLA) is a biodegradable thermoplastic polymer used in various applications, including food packaging, 3D printing, textiles, and biomedical devices. Nevertheless, it presents several limitations, such as high hydrophobicity, low gas barrier properties, UV sensitivity, and brittleness. To overcome this issue, in this study, biochar (BC) produced through pyrolysis of bio-mass waste was incorporated (1 wt.%, 2wt.%, and 3 wt.%-PLA 1, PLA 2, and PLA 3) to enhance thermal and mechanical properties of PLA composites. The impact of pyrolysis temperature on the kinetic parameters, physicochemical characteristics, and structural properties of banana and orange peels for use as biochar added to PLA was investigated. The biomass waste such as banana and orange peels were characterized by proximal analysis and thermogravimetric analysis (TGA); meanwhile, the PLA composites were characterized by tensile straight, TGA, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results indicated that the presence of biochar improved hygroscopic characteristics and Tg temperature from 62.98 °C for 1 wt.% to 80.29 °C for 3 wt.%. Additionally, it was found that the tensile strength of the composites increased by almost 30% for PLA 3 compared with PLA 1. The Young's modulus also increased from 194.334 MPa for PLA1 to 388.314 MPa for PLA3. However, the elongation decreased from 14.179 (PLA 1) to 7.240 mm (PLA3), and the maximum thermal degradation temperature shifted to lower temperatures ranging from 366 °C for PLA-1 to 345 °C for PLA-3 samples, respectively. From surface analysis, it was observed that the surface of these samples was relatively smooth, but small microcluster BC aggregates were visible, especially for the PLA 3 composite. In conclusion, the incorporation of biochar into PLA is a promising method for enhancing material performance while maintaining environmental sustainability by recycling biomass waste.

Keywords: AFM; DSC; PLA; SEM; TGA; biochar; composites.

Figure 1

Different heating rates TG curves for banana (A) and orange (B) peels.

Figure 2

Different heating rates—DTG curves for banana (A) and orange (B) peel.

Figure 3

Starink plots for thermal decomposition of banana peel (A) and orange peel (B).

Figure 4

Apparent activation energies for different conversion values (banana peel—(A); orange peel—(B)).

Figure 5

Parity diagrams from the analysis of banana peel degradation based on Coats–Redfern approach (A—region I; B—region II; C—region III; D—region IV).

Figure 6

Parity diagrams from the analysis of orange peel degradation based on Coats–Redfern approach (A—region I; B—region II; C—region III).

Figure 7

FT-IR spectra of samples (A—Banana; B—Orange).

Figure 8

Thermogravimetric analysis of PLA composites (A—TGA curves; B—DTG curves).

Figure 9

DSC thermogram of PLA composites.

Figure 10

Deformation curve of samples at room temperature.

Figure 11

SEM images on the surface of samples PCL1, PCL2, and PCL3 at magnification of ×100, ×1000, and ×5000: (a) PLCX100l, (b) PLCX1000, and (c) PLCX5000.

Figure 12

Topographic features of PCL1: (a) topographic image; (b) 3D image (scanned area 20 µm × 20 µm; Ra area 51.2 nm; Rq area 67.8 nm).

Figure 13

Topographic features of PCL2: (a) topographic image; (b) 3D image (scanned area 20 µm × 20 µm; Ra area 34.0 nm; Rq area 44.5 nm).

Figure 14

Topographic features of PCL3: (a) topographic image; (b) 3D image (scanned area 20 µm × 20 µm; Ra area 17.8 nm; Rq area 24.8 nm).

Figure 15

The plastograms of the PLA-based composites.