Effect of Chemically Modified Castor Seed (Ricinus Communis) Shell Powder on The Mechanical Properties of Natural Rubber Vulcanizate

Abstract

Mechanical properties of natural rubber filled with modified castor seed shell powder for some engineering applications were studied. Castor seed shells were obtained and treated with 20% NaOH for 1h, washed and dried at 75oC and were pulverized and sieved to 75μm. Treated castor seed shell (TCSS) powder showed improved characteristics when compared to the untreated (UCSS) in terms of pH, bulk density, moisture content, lignin content, cellulose content, hemicelluloses content, thermal stability, SEM and FTIR spectra respectively. Natural rubber was compounded at varying filler loadings of 0, 10, 20, 30, 40 and 50phr on a two-roll mill. The cure characteristics of the compounded rubber were determined using a Mosanto Rheometer (model MDR 2000) and the result obtained were used for vulcanization in a hydraulic press. The cure characteristics, mechanical and morphological properties of the vulcanizates were analysed and compared with carbon black filled samples. The preliminary results showed that castor seed shell is hydrophilic which was chemically treated to decrease the hydrophilicity. The maximum and minimum torques increased with filler loadings. The result of the natural rubber filled vulcanizates showed improved mechanical properties such as; tensile strength, modulus, tear strength, hardness, abrasion resistance which increased with increased filler loadings while elongation at break, flex fatigue, compression set, impact strength and rebound resilience decreased with filler loadings. The TCSS filled vulcanizate showed superior abrasion resistance and compression set when compared with UCSS and CB filled. The sample morphology at 30phr revealed that TCSS was well dispersed due to strong interfacial adhesion between the filler and the matrices contributing to the improved mechanical properties investigated when compared to UCSS filled with poor interfacial interaction. The result reveal that TCSS is a reinforcing filler that can be used for the production of natural rubber-based products for some engineering applications.