A novel vegetable oil nanoemulsion-plasticized natural rubber latex compound: Effect of ingredient blending sequence on crosslink density and tensile strengths

Abstract

The use of natural-based plasticizers in substitution of the conventional petroleum-based plasticizers present an attractive market value along with the increasing worldwide trend towards the usage of new bio-based materials made from renewable resources. This research studied the effect of ingredient blending sequence in natural rubber (NR) latex compounding that utilized a vegetable oil nanoemulsion as a natural-based plasticizer. The effects on crosslink density in relation with tensile properties of the latex films were investigated. A vegetable oil nanoemulsion of particle size 10.43 nm was first prepared from the blend of coconut kernel oil (CKO) and soybean oil (SBO) in the ratio of 7:3 using phase inversion temperature (PIT) method. The compounding of this nanoemulsion and vulcanizing chemicals into NR latex was distinguished by the blending sequence. Latex films were subsequently prepared for each compound and analysis of crosslink density and tensile properties were carried out. Results showed that ingredient blending sequence influenced the crosslink density in proportion with tensile properties. The high crosslink density was formed in (NR/E)/C ternary blend where the emulsion was first blended with NR latex and kept for maturation overnight prior to addition of rubber chemicals. This indicated that CKO/SBO nanoemulsion could serve as a potential natural-based plasticizer for NR latex compounding when NR latex was pre-matured with vegetable oil nanoemulsion to promote easier penetration and dispersion of vulcanizing chemicals in NR latex. This (NR/E)/C blending sequence subsequently improved the crosslinking within NR particles and tensile strength of the latex films compared to the other ingredient blending sequences.