Reactivity estimation of polybutylene terephthalate with noncovalently functionalized multiwalled carbon nanotubes and reactivity effect on the composite reinforcement

Abstract Multiwalled carbon nanotubes (MWCNTs) with physically absorbed pyrene derivatives containing a hydroxyl group are investigated as an effective filler for polybutylene terephthalate (PBT) composites. During extrusion, transesterification reaction occurred between the hydroxyl group of 1-pyrenebutanol (PBOH) and ester group of PBT, thereby grafting PBT onto MWCNTs. Reactions between PBT and 1-hydroxypyrene (POH) and 1-pyrenemethanol (PMOH) absorbed onto the MWCNTs were also observed. Compared to the POH and PMOH absorbed MWCNTs, the higher amount of PBT was grafted onto PBOH absorbed MWCNTs (PBOH-MWCNTs). Calculation results using the density functional theory suggest that the reactivity of PBT was higher with PBOH than that with POH and PMOH, due to the lowest free energy change at the rate determining step and most stable intermediate formation at the rate determining step for PBOH. PBT/PBOH-MWCNT composite exhibited the highest tensile strength and fatigue life. The highest reactivity of PBT with PBOH among the pyrene derivatives resulted in the greatest amount of PBT grafting onto the PBOH-MWCNTs, best interfacial adhesion between PBT and the PBOH-MWCNTs, and highest mechanical reinforcement in the PBT/PBOH-MWCNT composite.