Lauric acid coated fly ash as a reinforcement in recycled polymer matrix composites

Sustainable composites were developed from fly ash (FA) and recycled polypropylene (R) with lauric acid (LA) as the coupling agent. The FA particles were surface‐coated with 1, 2, 3, and 5 wt % LA, and the coating on the FA particles was verified by transmission electron microscopy and Fourier transform infrared spectroscopy. R and LA‐coated FA particles were melt‐mixed in a 1:1 weight ratio to achieve a high‐filler‐loaded composite. The flexural, impact, nanoindentation, and fracture surface analyses were carried out to examine the properties of the composites. The flexural strength and modulus values increased in the 2 wt % LA‐coated FA/R composites by 6 and 50%, respectively, compared to the values of the uncoated FA/R composites, whereas the impact strength increased considerably by 119% in the 1 wt % LA‐coated composites. Nanoindentation tests also showed an increase in the mechanical properties in the case of the 1 and 2 wt % LA‐coated composites in comparison to the uncoated ones. Fracture surface studies done by scanning electron microscopy revealed improved interfacial interactions between the filler and matrix in the presence of the LA coupling agent. X‐ray diffraction (XRD) studies indicated reorientations of the polymer chains in the presence of different concentrations of the LA coupling agent; this resulted into different crystallinities and crystallite sizes. Differential scanning calorimetry showed a significant difference in the crystalline peaks of the composites, and this corroborated well with the XRD observations. LA, thus, significantly influenced the structural properties of the composites, and this, in turn, influenced their mechanical and thermal properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41586.