The effect of filler size on the cure characteristics, processability, mechanical properties, and morphology of stearic acid-coated CaCO3 filled natural rubber compounds


  • Wanvimon Arayapranee Department of Chemical and Material Engineering, Rangsit University, Phathum Thani, 12000, Thailand
  • Garry L. Rempel Department of Chemical Engineering, University of Waterloo, Ontario N2L 3G1, Canada


natural rubber, filler, stearic acid-coated CaCO3, mechanical properties


The effects of filler loading and size on curing characteristics and mechanical properties of stearic acid-coated CaCO3 filled natural rubber (NR) compounds have been studied.  A two-stage conventional mixing procedure was used to incorporate two particle sizes, 1 and 5 mm, of stearic acid-coated CaCO3 into natural rubber.  Filler loading was varied from 0-60 parts per hundred of rubber (phr) at 15 phr intervals.  The cure time (t90) of both filler sizes decreased with increasing stearic acid-coated CaCO3 loading.  At a given filler loading, larger particle size coated CaCO3 showed shorter t90.  The Mooney viscosity increased with an increase in filler loading and smaller particle size showed higher viscosity.  Tensile strength of the coated CaCO3 filled NR compounds increased with filler loading until a maximum level was reached (at approximately 30 phr) and then started to decrease with further increase in filler loading.  As the coated CaCO3 loading increased, the compounds became stiffer and harder.  Thus, an increase in the modulus at 300% elongation with increasing filler loading was obtained.  Again, the compounds filled with smaller coated CaCO3 size showed higher tensile strength and 300% modulus.


Arayapranee, W., & Rempel, G. L. (2008). A comparison of the properties of rice husk ash, silica, and calcium carbonate filled 75 : 25 NR/EPDM blends. J Appl Polym Sci, 110, 1165-1174.

Atikler, U., Basalp, D., & Tihminlioğlu, F. (2006). Mechanical and morphological properties of recycled high-density polyethylene, filled with calcium carbonate and fly ash. J Appl Polym Sci, 102, 4460-4467.

Chan, C. M., Wu, J., Li, J.-X., & Cheung, Y.-K. (2002). Polypropylene/calcium carbonate nanocomposites. Polymer, 43, 2981-2992.

Chiu, H.-T., & Chiu, W.-M. (1996). Influence of mechanical properties in carbon black (CB) filled isotactic polypropylene (iPP) and propylene-ethylene block copolymer. J Appl Polym Sci, 61, 607-612.

Ess, J. W., & Hornsby, P. R. (1986). Characterisation of distributive mixing in thermoplastics compositions. Polym Test, 6(3), 205-218.

George, K. M., Varkey, J. K., Thomas, K. T., & Mathew, N. M. (2002). Epoxidized natural rubber as a reinforcement modifier for silica-filled nitrile rubber. J Appl Polym Sci, 85, 292-306.

Ismail, H., Nordin, R., & Noor, A. M. (2002). The comparison properties of recycle powder, carbon black, and calcium carbonate filled natural rubber compounds. Polym-Plast Technol Eng, 41, 847-862.

Kiss, A., Fekete, E., & Pukánszky, B. (2007). Aggregation of CaCO3 particles in PP composites: Effect of surface coating. Compos Sci Technol, 67, 1574-1583.

Nasir, M, & Choo, C H (1989) Cure characteristics and mechanical properties of carbon black filled styrene-butadiene rubber and epoxidized natural rubber blends. Eur Polym J, 25, 355-359.

Rigbi, Z. (1982) Reinforcement of rubber by carbon black. Rubber Chem Technol, 55, 1180-1220.

Sahnoune, F., Lopez Cuesta, J. M., & Crespy, A. (2003). Improvement of the mechanical properties of an HDPE/PS blend by compatibilization and incorporation of CaCO3. Polym Eng Sci, 43(3), 647-660.

Shah, G. B., & Fuzail, M. (2006). Modification of polyethylene and incorporation of fillers for effective reinforcement of mechanical and better flame retardant properties. J Appl Polym Sci, 99, 1928-1933.

Supaphol, P., Harnsiri, W., & Junkasem, J. (2004). Effects of calcium carbonate and its purity on crystallization and melting behavior, mechanical properties, and processability of syndiotactic polypropylene. J Appl Polym Sci, 92, 201-212.

Xu, T., Lei, H., & Xie, C. S. (2002). Investigation of impact fracture process with particle-filled polymer materials by acoustic emission. Polym Test, 21(3), 319-324.




How to Cite

Wanvimon Arayapranee, & Garry L. Rempel. (2023). The effect of filler size on the cure characteristics, processability, mechanical properties, and morphology of stearic acid-coated CaCO3 filled natural rubber compounds. Journal of Current Science and Technology, 3(2), 113–119. Retrieved from



Research Article