The Research On Sidewall Carboxyl-functionalization And Polyurethane Composite Of Carbon Nanotubes

Carbon nanotubes(CNTs) has become the research focus of chemistry physics and materials science rapidly, and has a lot of potential applications in the future Hi-Tech field, due to its peculiar mechanical, electronic, chemical properties and unique one-dimensional tubal structure. However, CNTs is chemical inertia and cannot be dissoluble in general organic solvents, which become most serious impediment during developing its researches and applications. In term of these, sidewall carboxyl-functionalization was carried out between multiwalled carbon nanotubes(MWCNTs) and succinic acyl peroxide in order to improve its chemical active and solubility in the paper. On the basis of this, polyurethane(PU) was grafted from MWCNT sidewalls via in situ polycondensation, and the effect of different content and modification MWCNTs on mechanical and thermal properties of MWCNTs/PU composites was investigated.Firstly, sidewall carboxyl-functionalization was carried out between MWCNTs and succinic acyl peroxide via the approach of free radical addition reaction, the resulted product was characterized by spectroscopy and its solubility was surveyed. The results showed that attack of carboxyl free radical resulted in the conversion of some C atom from sp~2 hybrid to sp~3 hybrid on MWCNT sidewalls, which resulted that sidewall carboxyl-functionalization MWCNTs was achieved and the quantity of sidewall carboxyl group had a certain increase compared with purified MWCNTs. TEM results showed that the degree of MWCNT twining was reduced after sidewall functionalization. Moreover, sidewall carboxyl-functionalization caused MWCNT suspension have higherζelectric potential, therewith inter-tube electrostatic exclusion effect among MWCNTs was strengthened also, so its suspension had higher dispersion stability.Secondly, sidewall functionalization MWCNTs was modified by grafted with polyurethane via in situ polycondensation approach, and the modification effect was characterized. The results showed that the graft process was combined with two approaches of"grafting to"and"grafting from", which ensure the graft efficiency of MWCNTs. MWCNTs were tethered a layer of polyurethane with a thickness in the range of 2~5 nm, and its surfaces presented a"bumpy"sidewall morphology. TG analysis showed that a graft rate of PU is up to about 54%.Finally, MWCNTs/PU composites with different modification and different content MWCNTs were prepared via in situ complex approach, and the effect of them on mechanical and thermal properties was investigated. The results showed that tensile strength and elongation at break of composites appeared the variation tendency of dropped after increasing...