Tapioca Starch Based Green Nanocomposites with Environmental Friendly Cross-linker

Abstract

Starch based films have drawn considerable attention on food packaging owing to their attractive combination of price, environmental friendliness, and abundance. Nevertheless, the use of starch based films in industrial application were restricted by its poor mechanical properties and naturally intractable behavior. The aims of this work were to develop starch green composite films prepared with sustainable materials in agreement with ecology and economic requirements including environmental satisfactory disposal and to investigate the effects of nanocellulose and citric acid on tensile properties, and thermal properties of tapioca starch green composite films. Through the advance of nanotecnology, nanocellulose recovered from oil palm empty fruit bunches (EFB) by chemical approaches acted as reinforcing material incorporated into tapioca starch green composites. Citric acid was a cross-linking agent added to crosslink the tapioca starch molecules in the films. A series of tapioca starch green composite films with varying amount of nanocellulose (0.5, 1, 2, 3, 4, and 5 phr) as per dry weight of tapioca starch were produced by casting method. Plasticizer such as glycerol was added to improve the processing of tapioca starch green composite films by softening the polymer matrix. Confirmation of nanocellulose characteristics were carried out by using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Whereas the effects of nanocellulose and citric acid on tapioca starch green composite films were performed by Instron Universal tensile testing machine and thermogravimetric analyzer (TGA). FTIR analysis on nanocellulose verified that the chemical treatments and acid hydrolysis removed non-cellulosic constituents including hemicelluloses and lignin from empty fruit bunches. XRD diffractograms revealed that the crystallinity of nanocellulose increased from 43.1 % of raw EFB to 65.8 %. TEM images confirmed the diameter of nanocellulose was in nano-sized with needle like structure. The tensile strength and modulus of elasticity of tapioca starch green composite films were enhanced significantly as the amount of nanocellulose increased from 0.5 to 3 phr and decreased for further addition of nanocellulose. While the value of break elongation sharply increased from 9.08 % for neat tapioca starch (TS) films to 109.36 % for crosslinked TS films. Therefore, these results reasonably remarked that nanocellulose from empty fruit bunches and citric acid could improve the tensile of tapioca starch green composite films. However, crosslinked TS/NC films using citric acid slightly lower the thermal stability.