Natural Rubber Nanocomposites: A Review.

Liliane Bokobza

doi:10.3390/nano9010012

Abstract

This paper reviews studies carried out on natural rubber filled with nanofillers such as spherical silica particles (generated by the sol gel reaction), clays and carbon nanostructures. It is shown that the mechanical response of NR is influenced by several parameters including the processing conditions, the state of filler dispersion, the polymer-filler interactions and the filler morphological aspects. Even if the sol gel process conducted in vulcanized rubber yields almost ideal dispersions, rod-shaped particles such as clay, carbon fibers or carbon nanotubes are by far more efficient in terms of mechanical reinforcement on account of their anisotropic character and their ability to orientate in the direction of stretch. The efficiency of layered fillers such as clays or graphitic structures clearly depends on the way they are dispersed (exfoliated) in the rubber. Complete exfoliation still remains difficult to achieve which limits the tremendous nanoreinforcement expected from a single layer of clay or graphite. In all cases, the onset of crystallization is observed at a lower strain value than that of the unfilled matrix due to strain amplification effects.

Highlights

Natural rubber (NR) known as cis-1,4-poly(isoprene) is contained primarily in the milky sap or latex of the Hevea brasiliensis tree in addition to a small amount of nonrubber products including proteins, carbohydrates, lipids and inorganic salts
As already observed in nanoclay-filled rubber [49], the results reveals that, contrary to unfilled NR that exhibits a single crystallization step, the MWCNT-composite has a slope similar to that of pure NR in the strain range of 2.8-3.8 and a much larger slope value above 3.8 showing that the nanotubes accelerate the of ultra-lightweight, low cost, and advanced composite materials [84,85]
As already observed in nanoclay-filled rubber [49], the results reveals that, contrary to unfilled NR that exhibits a single crystallization step, the MWCNT-composite has a slope similar to that of pure NR in the strain range of 2.8-3.8 and a much larger slope value above 3.8 showing that the nanotubes accelerate the crystallization rate at large deformations

Summary

Introduction

Natural rubber (NR) known as cis-1,4-poly(isoprene) is contained primarily in the milky sap or latex of the Hevea brasiliensis tree in addition to a small amount of nonrubber products including proteins, carbohydrates, lipids and inorganic salts. Nanofillers have concentrated huge attention as reinforcing agents for elastomeric materials because they are expected, if well dispersed in the host medium, to offer a large interfacial area with the polymeric medium, available for polymer-filler interactions Spherical particles as those generated by the sol-gel process, layered fillers such as clays or graphitic structures, single layer of graphite such as graphene, rod-shaped particles such as clay and carbon fibers or carbon nanotubes, are playing an increasingly important role in the development of rubber nanocomposites. This work presents a brief overview of studies carried out on natural rubber nanocomposites based on fillers of different morphology It focuses on the manufacturing techniques, the extent of reinforcement provided by each type of particles with a special emphasis on their effect on the strain-induced crystallization process as well as on the prevailing problems of filler dispersion

Sol-Gel In Situ Generation of Filler Particles

Clay Particles

Birefringence measurements for unfilled

Carbon Nanomaterials

Findings

Conclusions