Resumo

NAVIA P., DIANA PAOLA; AYALA A., ALFREDO ADOLFO  e  VILLADA C., HÉCTOR SAMUEL. DETERMINATION OF WATER ADSORPTION ISOTHERMS IN BIOCOMPOSITES OF THERMOPLASTIC FLOUR AND FIQUE. Rev.Bio.Agro [online]. 2013, vol.11, n.1, pp.144-153. ISSN 1692-3561.

Thermoplastic cassava flour composites reinforced with fiquefiberwere manufactured by thermopressing technique using two varieties of cassava flour (MPER 183 and CM 4574-7), plasticized with glycerol. Composites were subjected towater vapor adsorption testing by the gravimetricmethod at 15, 25, and 35°C in the range of water activity between 0,12 and 0,98. The composites The experimental adsorptionvalues were mathematically modeled using GAB, Caurie,Oswin, Smith, Henderson and Pelegequations. The isosteric heat of adsorption (Q_st) was determined by the Clausius-Clapeyron equation. The results showed that all the isotherms were type III. The cassava variety factor did not influence significantly (p>0,05) on the equilibrium moisture content, while the temperature did show significant differences (p<0,05) in water activity valuesover 0,85.The model that best fitted the experimental results at storage temperature of 15 and 25 °C was Peleg, while at 35 °C the GAB model gave a better fit. The Qstdecreased with the increase in the equilibrium moisture content, varying between 66 and 44 kJ/mol.

Palavras-chave : Biodegradable; Humidity; Bioplastics.

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