High strength bio-composite films of poly(vinyl alcohol) reinforced with chemically modified-fly ash

Fly ash (FA) was chemically modified by activation with sodium hydroxide and used in fabrication of bio-composite films with poly(vinyl alcohol) (PVA) by aqueous casting method. The particle size distribution patterns of modified-fly ash (MFA) were shifted from 2–20 μm to the higher regions 2–40 μm in the analysis chart of Malvern Light Scattering Particle Size Analyser (MLSPSA). On the oxides based chemical analysis by X-ray Fluorescence Spectroscopy (XRF), the compositions of major oxides, SiO2 73.5%, Al2O3 19.2% and Na2O 1.4% were significantly changed to SiO2 52.9%, Al2O3 23.6% and Na2O 5.9%, due to the dissolution and re-crystallisation of new phases which are characterised by X-ray diffraction (XRD). The composite film reinforced with 20 wt% MFA showed up to higher tensile strength 289% (three-fold) compared to those of unmodified FA filled films. The alkali treatment (sodium hydroxide) of FA is a very promising approach to improve the mechanical strength, and hence, further enhance the potential for recycling FA as a suitable filler material in bio-composite materials.