Preparation of Multifunctional Additive [MFA] from Castor Oil (CO) and Study of its Effects on the Physical Properties of Natural Rubber Vulcanizates

Abstract

This experiment focuses on the synthesis of Multifunctional Additives (MFA) from Castor seed oil (CO) and pure Oleic acid (OA) respectively. These multifunctional additives (CO-MFA and OA-MFA) were investigated as potential substitutes for process oil, activator, co-activator, and accelerator in the formulation of a natural rubber vulcanizate. During processing, the castor seed oil was characterized for acid value (AV), free fatty acid (FFA) and saponification value (SV) and subsequently reacted with 1, 6-hexane diamine to obtain a mixture of salts termed castor oil-based multifunctional additives (CO-MFA), similarly, a pure oleic acid was also reacted with 1, 6-hexane diamine to obtain a pure salt termed oleic acid-based multifunctional additive (OA-MFA). These compounds were investigated as substitutes for process oil/stearic acid, process oil/stearic acid/zinc oxide, process oil/MBT, and process oil/stearic acid/zinc oxide/MBT in the formulation and compounding of natural rubber vulcanizate. The pre-mastication of the rubber and subsequent mixing with additives was carried out in a Banbury Internal Mixer at a rotor speed of 50 rpm for 7 mins while the vulcanization was achieved on a compression molding machine at a temperature of 140oC for 15 mins. The various vulcanizates samples were evaluated for tensile properties, compression set, abrasion resistance, and hardness. The use of castor seed oil-based multifunctional additives (CO-MFA) as a substitute for process oil/stearic acid/zinc oxide/MBT gave the highest value of tensile strength (12.24 MPa) as against the conventional rubber compound (4.21 MPa).