Impact of citric acid on guar gum carboxymethylcellulose crosslinked blend films
Marcos Antonio Pereira Morais, Maurício Silva, Maria das Graças Barros, Peter J. Halley, Yêda Medeiros Bastos de Almeida, Glória Maria Vinhas
Abstract
Abstract This research intends to create biodegradable packaging films using solution casting method. The films are composed of guar gum, carboxymethylcellulose, and blends of these materials with citric acid as a crosslinking agent. The concentration of citric acid ranges from 10 to 30% (w w −1 ). This study performs a curing treatment at 140°C for 30 min on the dried films containing the crosslinking additive to promote the esterification between the polymeric matrix and the crosslinking agent. The thin films have a smooth, homogeneous, and transparent aspect. Although the crosslinking reaction – evidenced by FTIR spectra – does not affect the thickness of the material, it causes a slight color variation making the samples assume a yellowish shade. Moreover, the crosslinking process enhances the water resistance, decreases the crystallinity index, and improves the water vapor barrier and thermal resistance of the films. The SEM images reveal the excess of unreacted crosslinking agent accumulated on the samples; these particles work as a plasticizer, affecting the morphology of the films as well as their water resistance, crystallinity, and thermal resistance.