Uso de bionanocompósitos quitosana/argila na modificação superficial de tecidos de algodão e seu efeito antimicrobiano e bloqueador UV.

Abstract

The objective of this work was to develop a textile finishing based on chitosan/clay bionanocomposites in cotton fabrics in an attempt to confer antimicrobial and UV blocking properties. First, two commercial chitosans, coded as Q86 and Q92, were tested, according to their datasheets they had degrees of deacetylation (GD) of 86.7% and 92.0%. 1% and 2% (w/v) solutions of chitosan in 1% (v/v) acetic acid were prepared, where 100% cotton tissue samples were immersed (with 150 (T150F) and 200 (T200F) yarns), to promote surface modification. Chitosan was characterized by spectroscopy in the infrared region (FTIR) for determination of GD and by capillary viscosimetry for determination of Molecular Weight (Mv). The tissue samples were impregnated with chitosan and bionanocomposite chitosan/clay solutions at concentrations of 5, 10 and 50% of Cloisite C20A clay in relation to chitosan mass. Under the same conditions of preparation, chitosan solutions were obtained with the addition of the plasticizer Polyethyleneglycol (PEG), to promote better impregnation of the films and/or Irgacure® crosslinking agent, with subsequent exposure to a UV source to promote crosslinking. The coated tissues were characterized by FTIR, Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Swelling Degree, Contact Angle measurement, and Dispersive Energy Spectrometry (EDS). In addition to these characterizations, the antimicrobial activity and sun protection factor were also evaluated. The GD values of the two chitosans used were differed from those reported by the manufacturers, with both chitosans being approximately 76%. For molecular weight, it was observed that Q86 had a value near 35 kDa and Q92 of 90 kDa and that immersion of the tissues in chitosan solutions at any concentration altered the color of the samples. The Q86 was selected for the evaluation of the antimicrobial activity, since it presented lower molar mass than Q92, potentiating the activity against Gram negative strains. The T200F tissue was also selected, as it provided a greater useful surface for the coverage by chitosan films. The Swelling Degree, Contact Angle, MO and MEV tests showed that there was no contribution of the processing variables or the use of the PEG to the sample coverage. The SEM showed a superficial alteration of the tissue samples and the Dispersive Energy Spectrometry (EDS) confirmed the change in the chemical composition of the same. The FTIR data from the tissue samples confirm the results of EDS. The results of antimicrobial activity demonstrated only tenuous activity against E. coli. The Ultraviolet Protection Factor (FPU) results statistically show that the bionancomposite coatings elevated the FPU of the crosslinked samples. According to these results it is evidenced that cotton fabrics coated with chitosan/clay bionanocomposites can be promising as active tissues - with antimicrobial characteristics and with UV protection.