Obtenção e caracterização de nanocristais de celulose extraídos da macroalga Padina sp. para produção de filme flexível

Abstract

Plastics, although versatile and low-cost, generate serious environmental impacts due to their slow degradation and improper disposal. Biodegradable films made from biopolymers such as corn starch and cassava starch are emerging as a sustainable alternative, especially when reinforced with cellulose nanocrystals (CNCs), which improve their mechanical and thermal properties. The main objective of this work was to study the effect of CNCs extracted from the macroalga Padina sp., obtained from the combined pre-treatment (alkaline and bleaching) of biomass, followed by acid hydrolysis, on biodegradable films. After hydrolysis, the CNCs suspension was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS), zeta potential, X-ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). The most relevant results indicated that the combined treatment of the macroalga Padina sp. showed FTIR spectra with a reduction in the typical lignin and hemicellulose peaks, as well as an increase in the intensity of the peaks related to cellulose. There was also a ecrease in the intensity of the peak associated with water absorption, suggesting that the reduction in the number of free hydroxyls is related to the dissolution of amorphous regions. The zeta potential indicated a suspension of -60.8 mV. XRD analysis indicated that pre-treatment did not alter the structure of native cellulose to the type II cellulose form. However, the crystallinity index (Ic) was 87.46%. Thermogravimetric analysis revealed that the combined treatment caused a reduction in the thermal stability of the biomass, which can be attributed to the replacement of hydroxyl groups by sulphate groups during the hydrolysis process. Finally, the DLS results showed particle sizes ranging from 164 to 300 nm. The CNCs were incorporated into the flexible films to study the efficiency of the nanobiocomposites at different concentrations. The films were then characterized by physical characteristics, transparency, elongation and FTIR. The results showed that CNCs improve the water barrier and crystallinity of the films, but reduce transparency and elongation, with greater compatibility in cassava films. FTIR analysis showed better organization of the polymer chains in the films with CNCs, highlighting their potential as effective additives for nanobiocomposites.