Preparation and characterization of candelilla fiber (Euphorbia antisyphilitica) and its reinforcing effect in polypropylene composites

Candelilla bagasse fiber (CBF) was prepared by a mesh sieve and ball-milling process and its reinforcing effect in a polymer matrix analyzed. Composites of polypropylene (PP) and CBF were prepared by melt blending with varying amounts (20, 25, and 30 wt%) of fiber using maleic anhydride PP as coupling agent. The chemical composition of CBF was analyzed according to Technological Association of the Pulp and Paper Industry (TAPPI) methods, and the morphology and thermal and chemical properties of CBF and its composites were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile testing. In general, fibers extracted from candelilla by a reduction process are comparable in terms of micro- and nanostructure to other lignocellulosic fibers. Dynamic light scattering (DLS) results reveal that sieve-milling reduces the fiber size. The results also show that the thermal stability of PP was enhanced when using CBF, but the crystallinity index of the PP composites decreased slightly according to DSC and XRD results. Furthermore, the Young's modulus was increased in PP/CBF samples with and without MAPP to obtain improved wettability and fiber-polymer adhesion. We found that CBF is an excellent alternative to replace conventional materials or synthetic fibers, as well as for reinforcement in polymer composites.