Chemically modified fly ash for fabricating super-strong biodegradable poly(vinyl alcohol) composite films

Composite films of poly(vinyl alcohol) (PVA) and chemically modified fly ash (MFA) by sodium hydroxide were prepared by aqueous cast method with 5, 10, 15, 20 and 25 wt% MFA treated with 1 wt% cross-linking agent (glutaraldehyde, GLA). The tensile strengths of the composite films were found to increase proportionally with MFA and the maximum strength attained was 414% higher in the case of 20 wt% MFA than that in neat PVA film. The percentage of strain at break exponentially decreased with addition of MFA. The modulus of the composites was determined to increase proportionally up to a maximum 685% at 20 wt% MFA compared to that of neat PVA film. Interfacial networking between the MFA and PVA was evident from scanning electron microscopy (SEM) images of tensile-fractured surfaces, which was not observed for the unmodified fly ash (FA) system. Atomic force microscopy (AFM) analysis showed that the mean square surface roughness of the composite films of PVA–MFA was 53% smoother than the films with FA.