Enriquecimento de filmes de carboximetilcelulose com cera de carnaúba e molibdato de sódio para aplicação agronômica

Abstract

The aim of this research was to develop biodegradable films formulated from carboxymethylcellulose, with a focus on agronomic applications and mitigating the use of petroleum-based packaging. Films based on carboxymethylcellulose (CMC) incorporated with carnauba wax (CW) and enriched with sodium molybdate (SM) were prepared using the casting technique, varying the concentrations of the additives according to a rotated central composite design (DCCR) 22. With regard to physical properties, water vapor permeability (WVP) was not affected by the additives, nor was moisture content. Due to the hydrophilic nature of CMC, it was not possible to experimentally determine the solubility and degree of swelling of the water films, since the films disintegrated completely during the tests. The results indicated that mechanical resistance is optimized when one of the components predominates, with better results at concentrations above 7.65% SM and above 20.00% CW. Furthermore, the combination of SM and CW in appropriate concentrations can increase the mechanical strength of CMC films without altering their barrier properties or moisture content. Structural and thermal analysis of the films revealed possible interactions between the polymer matrix and the additives, affecting the crystalline structure and thermal properties of the films, especially at higher concentrations of CW. Investigating the interactions between the polymer matrix and the additives, infrared spectroscopic analysis (FT-IR) revealed the appearance and displacement of bands, indicating that there were interactions between the matrix and the additives, and X-ray diffraction (XRD) showed a narrowing and lengthening of the diffraction peaks at higher wax concentrations, suggesting an improved crystalline organization. With regard to the morphology of the materials, thermogravimetry (TGA) showed a possible compromise in thermal stability, with a slight reduction in the temperature of the second stage of decomposition. In differential scanning calorimetry (DSC), for the analysis conditions used, the glass transition temperature could not be observed for the films and the presence of endothermic and exothermic peaks associated with the melting and crystallization of the wax was noted when there was a greater amount of lipid. Scanning electron microscopy (SEM) revealed rough surfaces and wax droplets in the samples with the highest concentration of lipid. Analysis of the release of SM impregnated into the solid material over time indicated that stabilization of the nutrient concentration in the aqueous medium was achieved after 60 min. The biodegradability assessment showed that the films degrade completely within three days of burial. This rapid decomposition indicates that they are environmentally friendly, as well as acting as an efficient means of supplying molybdenum to the soil.