Synthesis of polyisoprene/montmorillonite nanocomposites via differential microemulsion polymerization

Abstract

Polyisoprene-montmorillonite nanocomposites were successfully synthesized via differential microemulsion polymerization by using 2,2-azoisobutylronitile. PIP-CS15A nanocomposites with particle size of 30 nm and narrow size distribution were obtained. PIP was intercalated in the layer of CS15A, as confirmed by X-ray diffractometer that d-spacing of CS15A layer was expanded from 3.11 nm to 3.82 nm. Morphology of PIP-CS15A nanocomposites was determined by transmission electron microscope (TEM). Surfactant concentration, monomer to water ratio and CS15A loading were found to affect monomer conversion, solid content and particle size of PIP-CS15A nanocomposites. The monomer conversion of 81% was achieved at 10 %wt CS15A loading, monomer to water ratio of 0.24:1, initiator concentration of 0.25 %wt and surfactant concentration of 12 %wt based on isoprene monomer. PIP-MMT nanocomposites could be used as an effective nano-filler in natural rubber (NR) latex for the preparation of NR/PIP-MMT composites by pre-vulcanization. For NR/PIP-MMT composites, the mechanical properties in tensile strength and modulus of elasticity were dramatically improved as compared to unfilled NR. The tensile strength of NR/PIP-CS15A composites of 17.7 MPa was obtained at 2 %wt of CS15A content. The stability of NR/PIP-CS15A composites after thermal ageing increased as compared to unfilled NR by maintaining 87.6% of its tensile strength and 84% of its modulus of elasticity at 2 %wt of CS15A content.