Preparation of multiwalled carbon nanotube/nylon‐6 nanocomposites by in situ polymerization

Multiwalled carbon nanotube/nylon‐6 nanocomposites (MWNT/nylon) were prepared by in situ polymerization, whereby pristine MWNTs (P‐MWNTs) and purified MWNTs (A‐MWNTs) were used as reinforcing materials. The A‐MWNTs were purified by nitric acid treatment, which introduced the carboxyl groups (COOH) to the MWNTs. The SEM micrographs from the fractured surfaces of the nanocomposites showed that the A‐MWNTs were well dispersed in A‐MWNT/nylon as compared to the P‐MWNTs in P‐MWNT/nylon. The percolation thresholds of P‐MWNT/nylon and A‐MWNT/nylon, which were studied by rheological properties, were found at ∼ 1 wt % of the MWNTs. The conductivity of P‐MWNT/nylon and A‐MWNT/nylon were 3.15 × 10−5 and 7.46 × 10−5 S/cm by the loading of 5 and 7 wt % of MWNTs, respectively. Differential scanning calorimetry (DSC) showed that the crystallization temperatures of P‐MWNT/nylon and A‐MWNT/nylon (195°C) increased more than that of pure nylon (189°C) due to the nucleation effect of MWNTs. Wide‐angle X‐ray analysis indicated that the incorporation of MWNTs into the nylon matrix resulted only in α‐crystalline structure, which were quite different from those reported for the clay/nylon nanocomposite (show both α‐ and γ‐crystals). It might be due to the different geometry between the MWNTs and the nanoclay platelets, which have one and two‐dimensional geometry, respectively.