Aproveitamento de resíduos vegetais para material de reforço na produção de filmes biodegradáveis à base de gelatina

Abstract

The consumption of biodegradable packaging from renewable sources has become a response to a market increasingly seeking the incorporation of sustainable materials in the industry, in order to meet the demands of consumers who are more concerned with environmental issues. Aiming to contribute to the development of biodegradable packaging techniques, this study aimed to develop and characterize films made from commercial gelatin reinforced with microcelluloses from plant waste. In the first stage, microcelluloses were extracted and evaluated from the pods of the cowpea bean (Vigna unguiculata), CPMC, not reported in the literature, corn straw (Zea mays L.), CSMC, and pineapple peel (Ananas comosus), PPMC. To extract the microcelluloses, the residues underwent chemical treatment followed by ball milling with acid hydrolysis. The raw residues, cellulose and microcelluloses (MCs) were investigated using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). In the FTIR spectra, the absorption bands characteristic of hemicellulose and lignin at 1720, 1600, 1250, and 830 cm-1 disappeared. The TGA/DTG of the microcelluloses showed Tmax between 200-345°C. XRD revealed that the MCs exhibited crystallinity indexes between 69.23-75%. The micrographs showed materials at the micrometric scale with compact and lamellar conformations. Due to their higher efficiency in obtaining microcellulose from CPMC and CSMC (30.54% and 22.54%, respectively, from raw material), they were selected for use in the films. In the film production stage, 11 formulations were studied, defined by a 22 factorial experimental design with 4 axial points and 3 central points. Additionally, a film control (FC) was used without the addition of microcelluloses, containing 2.00% gelatin and 2.00% glycerol. The developed films were characterized in terms of their mechanical, structural, physical and chemical properties. The results showed that the film optimal (FO) from the experimental design was the formulation with 1.00% CSMC and 1.00% CPMC. The addition of MCs resulted in films that were 4x more resistant than the FC (2.71 MPa), reduced water vapor permeability (PVA) from 6.33 x 10-4 to 2.82 x 10-4 (gH2Omm/m2

h mmHg), decreased solubility (75.82%), and increased biodegradation from a total degradation in 1 day (FC) to 73.06% in 3 days (FO). The use of CSMC and CPMC proved to be promising, as they were able to improve the structural properties of the FO compared to the FC. Thus, the film made with 1% CSMC and 1% CPMC can be applied in the packaging industry and presents a potential alternative to conventional plastics.