Experimental investigations on material properties of alkali retted Pinus Roxburghii Fiber

Pinus Roxhurghii Needles (PRN) from the Pinus Roxhurghii tree is abundantly available as biomass waste worldwide. The PRN biomass waste can be effectively utilized as natural fibers in the fabrication of biocomposites. In this study, Pinus Roxburghii Fibers (PRF) was extracted from PRN biomass waste and treated with an alkaline solution using sodium hydroxide (NaOH). The investigation was carried out in terms of physical, chemical, thermal, mechanical, and morphological characterizations on the extracted untreated pinus roxburghii fibers (UTPRF) and extracted alkali-treated pinus roxburghii fibers (ATPRF). Fourier-transform infrared (FTIR) spectroscopy examination of UTPRF and ATPRF indicates that cellulose, hemicellulose and lignin functional groups were present in both ATPRF and UTPRF. X-ray diffraction (XRD) analysis was used to determine the crystallinity index (CI) of both untreated UTPRF and ATPRF samples. The findings revealed that the highest CI increase occurred in the 5% ATPRF (50.92%) sample compared to the UTPRF sample (47.20%). The chemical examination also revealed an increase in cellulose content from 58.30 ± 0.72 to 65.48 ± 0.80% after alkali treatment. The thermal stability of UTPRF and ATPRF was evaluated using Thermogravimetric analysis (TGA), which demonstrated an increase of 18 °C in stage-II degradation and 5 °C in stage-III degradation upon alkali treatment. The 5% alkali-treated fiber has achieved maximum tensile strength of 72.59 ± 25.55 MPa with a tensile modulus of 1.85 ± .81 GPa. From the investigations, it was revealed that the ATPRF with 5% concentration will be the most suitable for composite applications.