Synthesis and Properties of Cross-Linkable Waterborne Polyurethane/HMMM-CNT Nanocomposite

A series of cross-linked waterborne polyurethane/hexamethoxymethylmel-amine-carbon nanotube nanocomposites (WBPU/HMMM-CNT) were synthesized using carboxylic group functionalized CNT. The carboxylic groups on CNT were reacted with the methoxy groups of HMMM to get bonded HMMM-CNT. Unreacted methoxy group of HMMM-CNT was crosslinked with the carboxylic acid salt groups of WBPU and made crosslinked WBPU/HMMM-CNT nanocomposite. The mechanical properties (tensile strength and Young’s modulus) of conventional WBPU, crosslinked WBPU/HMMM, WBPU/CNT and WBPU/HMMM-CNT nanocomposites were compared under three conditions: untreated, wet and dried. It was observed that the mechanical properties of the crosslinked WBPU/HMMM-CNT nanocomposites were the least affected by water compared to conventional WBPU, crosslinked WBPU/HMMM, and WBPU/CNT nanocomposites. Differential scanning calorimetry (DSC) analysis also confirmed that the WBPU/HMMM-CNT nanocomposite can absorbed least water which can be easily removed by heating without destroying their crystalline structure. Crosslinked WBPU/HMMM-CNT nanocomposite recovered most of its mechanical properties of (with optimum HMMM-CNT content) after drying.