Abstract:
In this research, the properties of 50/50 NR/NBR blends containing MWCNT/NR masterbatches prepared using the predispersing method (P) and conventional method (C) were studied. The amount of MWCNT in both blends was varied from 0 to 6 phr. Additionally, the properties of NR/NBR blends at various blend ratios prepared from the MWCNT/NR masterbatch (mNR) and MWCNT/NBR masterbatch (mNBR) were compared. The amount of MWCNT for both mNR and mNBR blends was kept constant at 4 phr. Furthermore, the properties of 50/50 NR/NBR blends filled with 4 phr of MWCNT, OH-MWCNT, and SiOH-MWCNT were determined. The results show that modulus, tensile strength, tear strength, and electrical and thermal properties of the P blends are significantly higher than those of the C blends. This is simply due to the better MWCNT dispersion in the P blends. At 4 phr MWCNT, modulus, tensile strength, tear strength, and electrical conductivity of the P blend in the milling direction (MD) are higher than those of the corresponding transverse direction (TD) sample. Moreover, the anisotropic properties of the P blends are clearly observed when 4 phr MWCNT is loaded. This is because most of the MWCNTs in the P blends are aligned along the MD when MWCNT is not more than 4 phr as confirmed by dichroic ratio. Also, SEM images show that the number of MWCNT agglomerates increases when MWCNT is more than 4 phr. It was also found that hardness, modulus, tensile strength, tear strength, oil resistance, and thermal and electrical conductivities of the mNR blends are superior to those of the corresponding mNBR blends. Additionally, the results show that 100% modulus, storage modulus at 30 ºC, tensile strength, tear strength, and electrical conductivity of both mNR and mNBR blends in MD are higher than those of the corresponding TD samples. Moreover, the 50/50 mNR blend gives the best overall properties. Furthermore, it can be seen that modulus, tensile strength, tear strength, and oil resistance of the 50/50 NR/NBR blend containing SiOH-MWCNT are greater than those containing OH-MWCNT and MWCNT. Also, 300% modulus, storage modulus at 30 ºC, tensile strength, tear strength, and electrical conductivity of these blends in MD are higher than those of the corresponding TD samples. However, modification of the MWCNT surface does not affect the electrical and thermal conductivities of the blends.