Multiwalled Carbon Nanotubes Decorated with Layered Double Hydroxides as Multifunctional Fillers for Polypropylene

The multiwalled carbon nanotubes (CNTs) decorated with exfoliated and fragmented layered double hydroxides (CNT-LDH hybrids) were used as multifunctional nanofillers for isotactic polypropylene (iPP). Under similar experimental conditions, iPP/CNTs and iPP/LDH nanocomposites were also prepared. Compared to neat iPP, both CNT-LDH hybrids and LDH showed effective nucleation ability for iPP. Hybrid CNT-LDH fillers are found to improve the thermal stability and flame retardancy of iPP significantly even with minimum loadings (1 wt% CNTs + 1 wt% LDH) compared to the individual fillers. The highest 50 % weight loss temperature was observed for iPP/CNT-LDH nanocomposites. The nanocomposite prepared with 2 wt% of CNT-LDH hybrid fillers showed a reduction of heat release rate (HRR) of 59 %, which is much higher than the nanocomposites prepared with 2 wt% of CNTs (30.5 %) and 2 wt% of LDH (19 %). The limiting oxygen index value of iPP is 16.5 % and it increases to 23 % for iPP/CNT-LDH nanocomposites. We have shown that the synergetic effect between CNTs and LDH can surpass individual nanofillers as effective flame retardants due to the capability of formation of a jammed network in the polymer matrix and effective char formation to restrict the transport of volatile compounds during the burning of the polymer.

Automated summary

Decorated multiwalled carbon nanotubes with layered double hydroxides as fillers can significantly improve the thermal stability and flame retardancy of isotactic polypropylene. The formation of a jammed network and effective char formation can restrict the transport of volatile compounds.