Stearic acid as coupling agent in fly ash reinforced recycled polypropylene matrix composites: Structural, mechanical, and thermal characterizations


Correspondence to: Dipa Ray (E-mail:


Two industrial wastes, fly ash (FA) and recycled polypropylene (RPP) were used to prepare a value-added, sustainable, low cost composite material. Improving the interfacial interaction between the hydrophobic RPP matrix and the hydrophilic FA particles is important to get a good combination of properties. In order to tailor the interface, stearic acid was used as the coupling agent. The FA particles were coated with a saturated fatty acid, stearic acid (SA), in different weight % like 1, 2, 3, and 5. The SA coated fly ash particles were incorporated as filler in RPP matrix composites by melt mixing in 1 : 1 weight ratio. The composites were tested for their flexural properties, impact behavior, dynamic mechanical properties, fracture surface analysis, X-ray diffraction (XRD) study, and differential scanning calorimetry (DSC). An increase in flexural modulus and impact strength was observed in the stearic acid coated FA/RPP composites. In 1 wt % SA treated FA/RPP (RFASA1) composites, a significant increase in glass transition temperature was observed along with an increase in crystallinity. A green, renewable, inexpensive chemical like stearic acid was thus found to be an effective coupling agent in fabrication of a composite with 50 wt % filler loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1996–2004, 2013