Polypropylene is used in the textile industry in the manufacturing of plastic yarns, tapes, etc., but its low tensile strength and Young's modulus limits its associated applications. Composites of polypropylene with reinforcement of CaCO3 and rice husk ash were processed by compression molding. Bimodal porosity in rice husk ash particles has shown an improved interfacial anchoring effect via capillary effect resulting in enhanced mechanical properties, whereas such an effect is not observed with CaCO3 reinforcement in polypropylene matrix. On reinforcement with 10 wt % of each of rice husk ash and CaCO3, thermal decomposition temperature of polypropylene (333.3 °C) shifted to higher value of 415.9 °C and polypropylene Young's modulus (749.5 MPa) increased to 789.5 MPa (by 5.3%), but tensile strength decreased from 23.5 to 21.2 MPa (by 2.3 MPa only). The isolated contribution of CaCO3 and rice husk ash has been delineated, and resulting interfacial strengths have been quantified using analytical models. Rice husk ash has shown a stronger interfacial anchoring and can effectively replace CaCO3 as reinforcement for achieving improved mechanical and thermal properties of polypropylene composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46989.

Polypropylene (PP)‐based composites with reinforcements of CaCO3and rice husk ash (RHA, agricultural waste) are extensively used in textile industry and manufacturing of plastic yarns, tapes, etc. Tribological properties of the PP‐CaCO3‐RHA based composite are studied using constant‐ and progressive‐load scratching. The progressive load scratching depicts a transient‐state interaction, whereas, constant load scratching depicts steady‐state of wear, hence, both modes of scratching are reported to highlight the aspects of damage initiation and damage tolerance on PP‐based composites. The average scratch hardness and toughness of the PP composites improved with reinforcement in both modes of scratching. The reinforcement of 20 wt% RHA and 10 wt% RHA with 10 wt% CaCO3 in PP matrix, marginally improves (0.8%‐1.6%) the wear resistance (wear rate, WR of 12.1‐12.2 mm3 N−1 m−1) during the progressive load scratching compared to that of pure PP (12.3 mm3 N−1 m−1). Poor wear resistance (WR = 12.6 mm3 N−1 m−1) with the addition of 20 wt% CaCO3 in PP matrix during the progressive wear is attributed to poor adhesion (adhesion factor: 0.61) of CaCO3 with PP. Also, an over estimation (3.4‐4.6 times) of wear rate is attributed to high recovery (0.63‐0.77) and the plastic deformation ahead of the scratch tip in the PP‐based composite with viscoelastic nature. High‐wear rate with CaCO3 agglomerate with poor sinterability at 200 °C can be substituted with the strong adhesive nature of RHA (bimodal pore distribution) in PP matrix to achieve optimal hardness, elastic modulus, and scratch resistance.