Exfoliation and physico-chemical characterization of novel bioplasticizers from Nelumbo nucifera leaf for biofilm application

Abstract

Due to the extreme threats as environmental and health issues caused by the petroleum-based leachable plasticizers, researchers among different domains are more interested in finding unique biodegradable plasticizers from natural sources. The present study used Nelumbo nucifera leaf to extract novel biopolymers as viable substitutes for chemical plasticizers. The biopolymers extraction was carried out through chemical means and its physico-chemical and morphological characterization were carried out to confirm its plastic nature. The polymers extracted possess a low glass transition temperature (77.17 °C), good thermal stability (230 °C), low density (0.94 g/cc), good surface roughness (34.154 μm), low crystallinity index (25.1%) and moderate crystallite size (16.36 nm). The presence of an organic polymer with specific chemical groups as olefinic alkenes, epoxide, imino/azo groups, and hydrophobic organic siloxane groups, signify that the material is a condensed phenolic derivative. Furthermore, bio-film was formulated using NLP and poly lactic acid (PLA) matrix to evaluate its plasticizing effect and film-forming ability. Variation in specific properties of film was noted after bio-plasticizer addition, where tensile strength (20.94 ± 1.5 MPa to 19.22 ± 1.3 MPa) and Young's modulus (1.462 ± 0.43 GPa to 1.025 ± 0.52 GPa) was found to be decreased whereas increased the percentage of elongation at break (26.30 ± 1.1% to 39.64 ± 1.6%). In addition, decreased glass transition temperature (Tg) (59.17 °C), good surface compatibility, and increased flexibility of NLP-PLA film in contrast to pure PLA film authorizes the plasticizing effect of bio-plasticizers on PLA. Since the extracted bio-plasticizers could be a suitable replacement to harmful synthetic plasticizers for lightweight packaging applications in bioplastics sector.

Keywords: Bio-plasticizers; Characterization; Composites; Extraction; Nelumbo nucifera leaf; Polymers.

Graphical abstract

Fig. 1

Preparation stages of bio-plasticizers from Nelumbo nucifera Leaf.

Fig. 2

FT-IR spectrogram of NLP.

Fig. 3

UV spectrogram of NLP.

Fig. 4

XRD spectra of NLP.

Fig. 5

(a) TGA/DTG curves and (b) Coats-Redfern plot of NLP.

Fig. 6

DSC analysis curve of NLP.

Fig. 7

(a–d). SEM images of NLP at different magnifications.

Fig. 8

Microscopic image of particles measured (a), particle size variation of NLP (b), and size distribution histogram plot (c).

Fig. 9

2D/3D surface view (a & b), line profile (c) and roughness parameters (d) of NLP.

Fig. 10

Energy-dispersive X-ray spectrogram (a) and major elements (b) of NLP.

Fig. 11

Tensile properties of pure PLA film and 5% NLP/PLA film.

Fig. 12

DSC spectra of pure PLA film (a) and 5% NLP/PLA film (b).

Fig. 13

Pure PLA based bio-film (a), 5% NLP/PLA based bio-film (b), pure PLA film flexibility confirmation (c), NLP/PLA bio-film flexibility demonstrated (d), SEM images of pure PLA film (e&f) and 5% NLP/PLA based bio-film (g&h) at different magnifications.