The influence of surfactants on the processing of multi-walled carbon nanotubes in reinforced cement matrix composites

Five surfactants [sodium dodecyl benzene sulfonate (SDBS), sodium deoxycholate (NaDC), Triton X-100 (TX10), Arabic gum (AC), and cetyltrimethyl ammonium bromide (CTAB)] were employed separately or jointly as superficial active agents (SAAB), to enhance solubilization/dispersion of multi-walled carbon nanotubes (MWNTs) in aqueous solution and cement matrix. The stabilizations of MWNTs in 12 SAAs solutions were estimated through sedimentation time of each suspension with centrifugation or sitting in 60 days. The mechanical and electrical properties as well as microstructures of MWNTs/cement composites (MNT/CCs) using the SAAs of SDBS, NaDC, AG, or the mixture of SDBS and TX10 were investigated. It was found that the capability of SAAB in dispersing MWNTs roughly decreases in the order as SDBS&TX10, SDBS, NaDC&TX10, NaDC, AG, TX10, and CTAB. The SAA of SDBS and TX10 with a mixing ratio of 3:1 by weight exhibits the best solubilization/dispersion capability. The delaminating time of the suspension of the above SAA with or without centrifugation is 80 min and 60 days, respectively. The microscopy observation indicates that the nanotubes form a stable network in the MNT/CC using SDBS&TX10 SAA. In addition, compared to the Plain/C, the corresponding MNT/CC increases in flexural strength, compressive strength, and the electrical conductivity by 29.10%, 20.8%, and two orders of magnitude, respectively. The enhancements are attributed to the uniform and stable distribution of MWNTs with the suitable surfactants and the ultrasonic dispersion method. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim