Effect of surfactant content on rheological, thermal, morphological and surface properties of thermoplastic starch (TPS) and polylactic acid (PLA) blends

Heidy Lorena Calambás Pulgarin; Carolina Caicedo; Edwin Flórez López

doi:10.1016/j.heliyon.2022.e10833

Effect of surfactant content on rheological, thermal, morphological and surface properties of thermoplastic starch (TPS) and polylactic acid (PLA) blends

Heliyon. 2022 Oct 1;8(10):e10833. doi: 10.1016/j.heliyon.2022.e10833. eCollection 2022 Oct.

Authors

Heidy Lorena Calambás Pulgarin¹, Carolina Caicedo², Edwin Flórez López³

Affiliations

¹ Grupo de Investigación en Desarrollo de Materiales y Productos, Centro Nacional de Asistencia Técnica a La Industria (ASTIN), SENA, Cali, 760003, Colombia.
² Faculty of Engineering, Unidad Central Del Valle Del Cauca (UCEVA), Carrera 17a 48-144, Tuluá 763022, Colombia.
³ Grupo de Investigación en Química y Biotecnología QUIBIO, Universidad Santiago de Cali, Calle 5 No 62-00, 760035 Cali, Colombia.

Abstract

Miscibility in biopolymeric blends is a critical process that requires evaluation of the effect of surfactants or coupling agents under conditions similar to processing. Different mixtures in the molten state of plasticized starch and polylactic acid in the presence of a surfactant (Tween 20) at different concentrations were studied. This allowed knowing the rheological, thermal and surface behavior of the mixtures. The results of the dynamic rheological analysis showed increases in viscosity in the presence of the surfactant, in which strong interactions were produced at high shear rates that reflect possible crosslinking between the polymer chains, in addition to intermolecular interactions that were evidenced in the infrared spectrum. Likewise, the storage and loss modulus showed transitions mainly from viscous to elastic typical for thermoplastics. The thermogravimetric analysis did not show significant changes between the mixtures. However, the calorimetric analysis showed changes in the crystallinity of the mixtures, the tensoactive promotes greater freedom of movement and rearrangements in the microstructure with decrease of interface between polymers, and less compaction of the material induced by the emulsion. Analysis derived from biopolymeric films against contact with water shows significant changes. Interaction with water in short times (in the order of minutes) according to the sessile drop technique, favors hydrophilicity by increasing the concentration of Tween 20. However, interaction with water for prolonged times (in the order of hours), shows that the absorption reaches saturation in samples a stabilization in the absorption is observed. The results demonstrate that the miscibility of PLA in AS was achieved in the presence of the tween, under conventional processing conditions. The stability of the different formulations allows the production of films for packaging and biomedical applications.

Keywords: Achira starch; Biopolymers; Contact angle; Miscibility; Surface wettability.