Avaliação de biohíbridos sepiolita/rosin como agentes multifuncionais em embalagens biodegradáveis a base de PLA e PHBV

Abstract

Advances in materials science have enabled the development of multifunctional food packaging made from biodegradable polymers, such as polylactic acid (PLA) and polyhydroxybutyrate-co-valerate (PHBV), capable of replacing non-biodegradable single-use plastics. In this context, this thesis proposed the development of nanocomposites based on immiscible PLA/PHBV (70/30) blends reinforced with sepiolite (SEP, 5% by mass) esterified with rosin. SEP is a microfibrous clay mineral with high rigidity, while rosin is a resinous product of plant origin with biological properties. The multifunctionality comes from the biodegradability of the blend, the reinforcement provided by SEP, and the antimicrobial activity of rosin. The central hypothesis is that esterification of SEP with rosin would improve the chemical compatibility of the blend, increasing the mechanical properties and conferring antimicrobial activity to the nanocomposites. The work was conducted in three stages. Initially, four mixing protocols were prepared in a torque rheometer to obtain PLA/PHBV/SEP. The characterizations indicated greater compatibilizing action of SEP located preferentially at the interface. In the second stage, SEP was modified with rosin, obtaining r-SEP in two reaction times (4 and 10 h). In both cases, the chemical reaction was successful, resulting in greater thermal stability and a 73% increase in pore diameter compared to unmodified nanoclay. Microbiological tests showed greater activity of r-SEP 4 h against S. aureus and r-SEP 10 h against E. coli. In the third stage, r-SEPs were incorporated into (PHBV/SEP)PLA. The greater dispersion of nanoparticles resulted in a higher elastic modulus (G’) and an increase of up to 18% in maximum tension compared to PLA/PHBV/SEP. Thermal stability and antimicrobial activity were maintained after processing. The results demonstrated scientific merit, with superior compatibilizing and antimicrobial effects, as well as lower environmental impacts than silver nanoparticles (AgNPs), widely used as antimicrobial agents.