Experimental Investigation on the Thermal Behavior of Untreated and Alkali-Treated Pineapple Leaf and Coconut Husk Fibers

The primary objective of this research work is to study the thermal behavior of untreated and alkali treated pineapple leaf (PALF) and coconut husk fibers (COIR). In this context, firstly the cellulosic fibers were treated with an alkali solution of various concentration (2%, 4%, 6%, 8%, and 10 wt%) then secondly the change in their surface chemistry and thermal stability were investigated by means of a Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analysis technique (TGA) respectively. A significant variation in the chemical composition of cellulosic fibers was observed after an alkaline treatment. Changes in the peak at 1745, 1525, and 1250 cm⁻¹ in FTIR spectra corresponds to the partial removal of hemicellulose and lignin components. The thermal degradation of lignocellulosic fibers consists of two major steps i.e. moisture loss (below 150^°C) and the decomposition of hemicellulose, cellulose, and lignin components (between 150^°C to 400^°C). An alkali treatment increases the thermal stability of pineapple leaf and coir fibers through physical and chemical changes. It was observed that the 4 wt% NaOH treated PALF and COIR fibers possess higher thermal stability as compared to other treated and untreated fibers. PALF exhibits a higher rate of decomposition than the COIR fiber but its main decomposition peak lies at a higher temperature of about 40°C.