Ácido cítrico como compatibilizante entre amido e poliéster em filmes tubulares produzidos por extrusão

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Blends of thermoplastic starch and polyesters, as PBAT may be immiscible at the molecular level. The use of compatibilizing agents such as citric acid, could reduces the interfacial tension between polymer phases (starch/PBAT) improving the mechanical properties and water vapor permeability of films produced by extrusion. Extruders are used as chemical reactors in developing strategies for compatibilization. The objective of the research was to produce films from cassava starch and PBAT using citric acid as compatibilizer. The work was divided into two stages. At first, films were produced by extrusion (temperature of 120/120/120/130/130°C and 40rpm) according to a mixture design where the components were: glycerol (7,5-10,5% w/w), citric acid (2,5-4.5% w/w) and starch:PBAT (3:2) (85-90% w/w). The films were characterized by mechanical properties (strength and elongation at break) and water vapor permeability (WVP). The multiresponse optimization process, with tensile strength specified as intermediate level, elongation at maximum level and minimum level in PVA was performed using the statistical technique of desirability. With the optimal formulation suggested by this technique (10,5% glycerol (w/w), 3.0% citric acid (w/w) and 86,5% starch/PBAT (3:2, w/w)) and another control, without citric acid, new films were produced to evaluate the effect of acid. The resulting films were characterized for microstructure (SEM and FTIR-ATR) and subjective analysis. The resistance of the films was more influenced by the interaction between the components, while the elongation was influenced the linear effect of glycerol. The interaction between the three components of the mixture (glycerol, citric acid and starch/PBAT) exerted a higher influence on the PVA. Through the micrographs of the films we could observe a more homogeneous and compact the material with the addition of compatibilizer. However, the infrared spectra revealed little about the formation of cross-linking esterification reaction because the characteristic bands of ester linkages can also be attributed to monoester bonds. More studies are needed, but it is undeniable the effect of citric acid as compatibilizer in the blends of starch/PBAT judging from the micrographs obtained from the films. One has to consider that, the structural characteristics of these materials work together for a better understanding of its other properties.

ASSUNTO(S)

filmes biodegradáveis - processo de extrusão plásticos nas embalagens biofilme alimentos - embalagens amido de mandioca - filmes Ácido cítrico biodegradable films extrusion process plastics in packaging biofilms food packaging starch films citric acid

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