Electrically conductive elastomers based on natural rubber and polyaniline

Authors: MALMONGE, JOSE - Sao Paulo State University (UNESP); SANTIM, RICARDO HIDALGO - Sao Paulo State University (UNESP); McMahan, Colleen

Submitted to: Rubber World
Publication Type: Trade Journal
Publication Acceptance Date: 11/21/2022
Publication Date: 11/25/2022
Citation: Malmonge, J., Santim, R., McMahan, C.M. 2022. Electrically conductive elastomers based on natural rubber and polyaniline. Rubber World. 267(2):34-36.

Interpretive Summary: Natural rubber is an electrically insulating material, but introduction of conductive fillers like carbon-based materials (carbon black, graphite, carbon nanofibers or nanotubes) or metal fillers can increase the conductivity of the resulting composite. These materials are frequently used for electromagnetic/radiofrequency interference (EMI/RFI) shielding, and laboratory and military uses. Intrinsically conductive polymers (ICPs) are well known and include materials such as polypyrrole (PPy) and polyaniline (Pani), which can be considered semiconductors. When blended with elastomers, PPy and Pani can increase the electrical conductivity of the matrix and expand its application range. ICPs can be incorporated into elastomers by in situ polymerization. The use of natural rubber in an electrically conductive elastomer is attractive to increase biobased content of products designed for new applications in wearables and electronics. Here we demonstrated the feasibility of polymerization of aniline in a pre-vulcanized natural rubber latex matrix to produce electrically conductive natural rubber-based elastomers.

Technical Abstract: Natural rubber nanocomposites with polyaniline were obtained by in situ polymerization of aniline in the presence of pre-vulcanized and unvulcanized latex. The synthesis was carried out without the presence of organic solvent. The nanocomposites obtained with the pre-vulcanized latex showed higher electrical conductivity in relation to the non-vulcanized one, for the same NR/An ratio, a fact that is related to the different microstructures formed by Pani in the rubber matrix. Mechanical properties are dependent on the NR/An ratio and also on whether the latex is pre-vulcanized or not, with the highest values obtained for nanocomposites obtained from pre-vulcanized latex. Importantly, the use of pre-vulcanized latex introduces flexibility and ease in formulation optimization and processing. These remarkable materials combine properties of flexible elastomeric materials based on natural rubber produced in an environmentally attractive (low energy) process for manufacture of the nanocomposite.