Effect of matrix oxidation and nanoclay addition on hydrophilicity of starch nanocomposites

DANILA MERINO; TOMY J. GUTIERREZ; VERA A. ALVAREZ

Buenos Aires

Congreso; Frontiers in Physical Sciences Humboldt Kolleg; 2016

It was organized by the International Center for Advanced Studies(ICAS) and the Max Planck Liason Office for Latin America, in cooperation with the Kolleg Programme of the Alexander von Humboldt Foundation.

Environmental pollution caused by accumulation of non-biodegradable petroleumderived plastics has led to the search of new natural and biodegradable polymers in order to replace them [1, 2]. These polymers must be ecofriendly, low cost and with comparable performance [3]. Among them, Starch has been seen as the most promising candidate to fulfill this function since it has many practical advantages as its biodegradability, availability and low cost [2, 3]. However, it has two main disadvantages that limit its use for several applications: hydrophilicity and brittleness [3]. Chemical modification of starch and preparation of nanocomposites are two possible solutions to overcome these drawbacks [2, 3]. In the literature has been reported that incorporation of chitosan into starch matrices helps to reduce the degree of hydrophilicity of these materials [4]. In order to obtain improved composite materialsfrom starch, six different materials were designed. First, the chemical modification of native corn starch was carried out by treatment with hydrogen peroxide. Secondly,different nanocomposites from natural bentonite and bentonite previously modified with chitosan were added to the two starch-based matrixes. Films of ∼0.5 mm thickness were obtained by extrusion and subsequent hot-pressing. The effect of starch modification and addition of nanoclay in the chemical structure of both starches was followed by Fourier Transform infrared spectroscopy (FTIR). The water affinity of each film was studied by means of tests of total and superficial moisture content, water solubility, contact angle and degree of swelling. Finally, thermal stability of the composites was studied by thermogravimetric analysis (TGA). The results obtained in this study allowed to establish that both composites added had better interaction with the matrix of oxidized corn starch, which allowed increase the thermal resistance of these composite materials and reduce their hydrophilic character.