NR-based composites

In modern vulcanization processes, NR is generally compounded (either under high or low temperature) with 0.5 to 1 wt% of accelerators, different concentrations of CBs (which act as a filler) (up to 45 wt% for tyre manufacturing), low concentrations of aromatic amines and phenols for antioxidation purposes and 5-8 wt% of sulfur. These types of vuleanized NR are commonly known as NR composites (when the filler dimension is on the microscale) or NR nanocomposites (when the filler dimension is on the nanoscale). NR-based composites or nanocomposites will be discussed in more detail in the following sections. 

Carbon black (CB) is indisputably the most widely used reinforcing filler in NR formulations. It improves tensile and tear strengths, modulus and hardness, abrasion and thermo-oxidative resistance, etc. of NR-based materials. CB is manufactured by a variety of processes, including the channel process, to produce furnace black, thermal black, lamp black and acetylene black. NR-based composites and nanocomposites with the addition of CB exhibit the monotonous black colour to the finished goods. 

The researeh and development of NR-based composites shall be strategized on optimization of production cost of the composites eoupled with enhancement of the meehanieal properties of NR filled with nanofiller at lesser filler content as eompared to that of the convention mierofiller. The development of eco-friendly miero- and nanostructured functional materials based on NR is of commereial importanee. 

This chapter discusses the role of microscopic analysis for investigating all the above mentioned (i) - (iii) aspects, presenting a rationalized overview of available results. As it is of increasing evidence that only a multidisciplinary approach can lead to a more accurate picture of a NR-based composite, the information brought about by microscopic analysis is also discussed as complementary to findings arising from other analytical techniques. 

Field emission SEM (FESEM), characterized by both improved spatial resolution (down to 1 nm) and minimized sample eharging and damage, was recently developed. This technique was also applied to the morphological characterization of NR based composites containing CNTs giving important information on the adhesion between filler and matrix. 

A combined self-assembly and latex compounding technique was used for preparing NR-based composites containing positively charged CNTs. " TEM and SEM indicated that the CNTs were homogeneously distributed into the NR as single tubes and their interfacial adhesion with the matrix was good. 

Natural rubber (NR) is a classic elastomer with good processability and excellent mechanical properties. It is widely used in various applications such as automobiles, gloves, tyres and seals. With the increasing demand for NR composite materials for applications at high temperatures with high performance, for example in the automobile industry, there has long been increasing interest in NR-based composites blended with other rubber systems. ... 

Das, N.C., Khastgir, D., Chaki, T.K., Chakraborty, A., 2000. Electromagnetic interference shielding effectiveness of carbon black and carbon fibre filled EVA and NR based composites. Composites Part A-Applied Science and Manufacturing 31, 1069—1081. 

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