Poly(amidoamine) dendrimer-grafted carbon nanotube and polyurethane composites

Carbon nanotube (CNT) grafted with hyperbranched poly(amidoamine) (PAMAM) dendrimer (CNTD) were used as a multifunctional curing agent in the preparation of polyurethane (PU) nanocomposites. In this process, amino-functionalized CNT was used as the core for grafting the first generation of PAMAM dendrimer by sequential addition of methyl acrylate and ethylenediamine. Two different epoxy-terminated PUs (PUB and PUI) were prepared from the reaction of poly(ethylene glycol), excess amounts of hexamethylene diisocyanate, and different chain extenders (۱,۴-butanediol (BDO) for PUB and pyromellitic dianhydride (PMDA) for PUI), and subsequent end group transformation of the isocyanate groups to epoxy functionalities using glycidol. Fourier transform infrared spectra and thermogravimetric analysis (TGA) results showed that CNTD was successfully prepared. TGA thermograms revealed that decomposition of composites happens in two main steps related to the soft and hard segments. In addiiton, char content and thermal stability of the nanocomposites were increased with increasing the CNTD content. Most importantly, PMDA as the chain extender of the epoxy-terminated PU resulted in high thermal stability of the composites in comparison with BDO. X-ray diffraction and scanning and transmission electron microscopies presented morphological and structure properties of nanotubes and hybrid samples.

Keywords:

Carbon nanotube , chain extender , poly(amidoamine) dendrimer , polyurethane , thermal stability.