Chemical modification of starch and modified clays by microwave

Abstract Book of European Polymer Congress EPF 2013, Pisa, Italia. Vol. 1, 104 (2013).


Starch is one of the most important biopolymer because the diversity of its applications and the low cost. In the present work it was used potato starch from the discard potato, and in the plastification process it was added commercial modified clays 15A, 20A and 30B, in order to improve the mechanical properties of the blends with starch. The thermoplastic starch (TS) was realized with starch, glicerol and water (60/20/20) respectively, and additionally commercial clays was added (3% for the total of the blends) and was placed in a microwave with low power (~360W) by 2 min. This treatment was realized in order to increase the exfoliation of the clay in the blend. One drawback in the use of clays nanometric is its exfoliation in the matrix, the crystals consist of a thin layer of 1 nm with sheets octahedral type sandwiches between two sheets tetrahedral, clays are hydrophilic with balanced loads of Na+, Li+ or Ca+2, the improvement in properties is given to perform the peeling of said sheets which are initially agglomerated. Then the TS was blended with polylactid acid (PLA) and polybutyleneadipate-co- butyleneterephthalate (PBTA) in 48/26/23/3 (PLA/PBTA/TS/nano clay). The chemical modification was characterized by infrared spectroscopy, FTIR, finding new signals at 3627 cm-1 (free alcohols on the surface MMT), the double peak at 2880 cm-1 (CH3 vibration) and 992 cm-1 (C- C), as reported Liu et al (1), in their study but in this case the nanoparticles are mixed after the plasticization. We observed the structure of the mixture through a scanning electron microscope (SEM) observing the starch granule destruction and in transmission electron microscopy MET was observed exfoliation of the clay, also tested with an assay of X-ray diffraction, resulting in an increase in the d-spacing values, which could be attributed to that glycerol and starch chain had intercalated into the layer. The type of clays does not have a significant influence on the mechanical properties of the material, finding a modulus of elasticity of 40+10 MPa, and a breaking deformation percentage of 79+15%.

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