Effect of sodium hydroxide on properties of shrimp-shells-extracted chitin nanofibers

Abstract Shrimp shells from seafood wastes were used as a raw material to prepare chitin nanofibers (ChNFs) by combined chemical and mechanical treatments. The extraction of chitin from shrimp shells involved multistep procedures of deproteinization, demineralization and deacetylation. The deacetylation refers to the replacement process of acetyl groups by reactive amino groups (-NH 2 ). After that, treated chitin were fibrillated by high-speed blending to disintegrate ChNFs. In this work, we studied the effect of sodium hydroxide (NaOH) concentrations (0 - 30 %wt) on properties of ChNFs. Fourier transform infrared (FT-IR) spectra showed with increasing concentrations of NaOH, the intensity of the peak located at ∼1550 cm -1 , corresponding to the presence of amide groups (-NH) on chitin molecules decreased. This was an indication of the removal of acetyl groups. The thermal stability of ChNFs was subsequently analyzed by thermogravimetric analysis (TGA). With increasing the concentrations of NaOH, the lower thermal stability of ChNFs was obtained. In addition, the morphologies of ChNFs with widths of a few nanometers were observed by a field emission scanning electron microscope (FE-SEM). The prepared ChNFs in this work could be possibly used as a reinforcing agent for composite applications.