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Evaluation the effect of cross-linking with BTCA and reinforcement with cardboard (OCC) microfibers on the properties of plasticized starch
Biopolymers such as starch, are an alternative to the excessive use and waste caused by synthetic polymers because of their biodegradable, sustainable and renewable character. The development of plastic materials from starch has been limited due to its high hydrophilic character and its low mechanical properties, whereby the researches are focused on improving its performance by reinforcing the polysaccharide with natural fibers (biocomposites) as well as a chemical compatibilizer (crosslinker). Under this point of view, the present work aims to evaluate the effect of the chemical crosslinking by polycarboxylic acid onto microfibers from unbleached (MFLC) and bleached (MFC) cardboard and plasticized starch biocomposites by means of their morphology, structural order, mechanical properties, and the chemical composition. For this purpose, biocomposites films with an average thickness of 0.2 mm were prepared by solution casting method varying the amount of microfibers of 0, 4, 8 and 12 % based on starch weight. As a crosslinking agent, 1,2,3,4-buthanetetracarboxylic acid (BTCA) was used in 5 % based on starch weight. Microfibers were characterized by TEM and SEM, it was possible to observe their fibrillar structure and their dimensions. Regarding the characterization of the biocomposites, the study of their morphology allows to appreciate homogeneous distribution of the microfibers in the matrix of plasticized starch and good interaction between the reinforcement and the matrix. The chemical crosslinking via esterification of polycarboxylic acid (BTCA) with the starch chains (amylose and amylopectin) was confirm by a band obtained around 1723 cm-1 on the FT-IR spectra. The results obtained on the stress study showed that the incorporation of microfibers and the cross-linking of the starch improve the physic and mechanical properties, increasing the values of resistance and Young´s modulus. Crystallinity was also determined by X-ray diffraction, presenting increments in the percentage of crystallinity with the incorporation of the reinforcement and the crosslinking of the matrix.