Effects of alkaline treatments on natural fibers

Abstract

In the present investigation, analyses of the effects of alkalinization on three types of natural fibers (fique, pineapple, and flax) were carried out. Two chemical treatments were carried out on the natural fibers, the first one by means of a surface treatment leaving the fibers immersed for 1 hour, 2 hours, 8 hours, and 24 hours using concentrations of 1% w/w, 2% w/w, 5% w/w, and 10% w/w of sodium hydroxide and concentrations of 23% w/w, 33% w/w, 44% w/w, and 50% w/w of calcium carbonate, finally sodium silicate was used at a concentration of 68% w/w leaving the fiber immersed for 24 hours. The second treatment was carried out in a chemical reactor in which the fibers were subjected to a temperature of 30 °C for 30 minutes and 60 minutes using sodium hydroxide in the same way sodium silicate compounds at concentrations of 1% w/w, 5% w/w, and 10% w/w and finally calcium carbonate was used at concentrations of 23% w/w, 33% w/w and 50% w/w for the same periods of time. Tensile tests, hydrophobicity, optical microscopy, X-Ray diffraction, Fourier transform infrared, stress analysis and Young’s modulus were performed. The results show the elimination of some fiber components such as lignins and hemicelluloses in the treatment with sodium hydroxide, an increase in the crystallization and improvement in hydrophobicity with the sodium silicate treatment, as well as an increase in the stress supported by the treated fiber compared to the natural fiber.