Role of primary amine in polyoxymethylene (POM)/bentonite nanocomposite formation

Nanocomposites of Polyoxymethylene

“…In the case of POM/organo-modifi ed bentonite nanocomposites, T onset was shift ed to lower values by 1-2 ºC, and an excessive undercooling to initiate the crystallization process was needed. Th is indicated some obstruction of POM crystallization by dispersed silicate layers [25]. On the other hand, MWCNTs had a significant nucleating eff ect on POM, and 0.5 wt% MWCNTs enhanced the crystallization temperature of POM by about 6 ºC but did not change further with additional MWCNTs content [7].…”

“…In another work the thermal degradation temperature of POM/MMT nanocomposite was decreased by 40 ºC as compared to pristine POM [25]. Nanocomposites with N,N-dimethyl-N-phenyl-N-octadecyl ammonium (DMPhOA) used as a modifi er of surface properties exhibited particularly low thermal stability.…”

“…Introducing carbon nanofibers (CNFs) with intrinsically higher diameters than nanotubes did not result in improved elongation at break and toughness, but was reported to cause a considerable reduction in the creep and an increase in stiffness and strength [30]. Tensile strength and fl exural modulus of POM/organo-modifi ed bentonite nanocomposites were reported to remain at a similar level as for the neat POM [25]. However, fl exural strength and elongation at break of these nanocomposites were increased, especially of POM, with bentonite modifi ed with primary ammonium.…”

“…Kongkhlang et al demonstrated that the better the dispersion of nanoplates, the higher the resulting improvement in mechanical and gas barrier properties [25]. Th e oxygen barrier of POM/Organically modifi ed montmorillonite (OMMT) nanocomposite increased by 50% compared to neat POM.…”

“…Silicate layers are impermeable to gases and vapors and, when properly dispersed in polymer, increase the gas barrier property by creating a maze or "tortuous path" that elongates the diff usion path through the bulk of composite material [26,27]. Th e authors observed that when primary ammonium salt was applied as an organic modifi er of MMT the complex nanostructure of fl occulated and exfoliated clay layers was formed, whereas the quaternary ammonium-treated bentonite induced the formation of intercalated/fl occulated structure [25]. Th e better performance of nanocomposites containing primary ammonium-treated bentonite resulted from higher degree of exfoliation which, in turn, was explained in terms of favorable POM-OMMT interactions.…”