Extraction of Cellulose Nanowhiskers from Flax Fibres and Their Reinforcing Effect on Poly(furfuryl) Alcohol

The aim of this study was to explore the use of flax fibres as a source of raw material for the production of cellulose nanowhiskers (CNWs). The flax fibres were first cleaned using sodium hydroxide (NaOH), sodium chloride (NaClO2) and potassium hydroxide (KOH) and then separated to obtain CNWs by mechanical treatments such as the ultrasonication as well as chemical acid hydrolysis. Untreated and chemical treated flax fibres were characterized by Fourier transform infrared (FTIR), environmental scanning electron microscopy (ESEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The morphology of the isolated CNWs was characterized using atomic force microscopy (AFM). The crystallinity of the untreated flax fibres was 51.32% and it increased to 68% after the cleaning process. The resulting CNWs were rod-like shape with lengths ranging from 200 to 400 nm, while diameters were ranging from 10 to 16 nm and their aspect ratio were ranging from 20 to 25, respectively. CNWs were then incorporated into poly(furfuryl) alcohol following the in-situ polymerization to develop PFA/CNWs composites. The effect of CNWs on thermal, mechanical and thermomechanical properties of the neat PFA was investigated using thermogravimetric analysis (TGA), tensile test and dynamic mechanical thermal analysis (DMTA). The TGA results clearly showed a decrease in thermal stability of PFA/CNWs composite relative to the neat PFA. The incorporation of CNWs into PFA led to the increase in mechanical properties. SEM and FTIR suggest that there is interaction between CNWs and PFA. Glass transition temperature (T-g) and storage modulus (E') improved after the addition of CNWs. Therefore, CNWs can improve thermomechanical properties of PFA and they are promising reinforcing elements for the development of industrial composites.