Induction of the β-phase in isotactic polypropylene with pimelic acid modified graphene nanoplatelets

In this work, graphene nanoplatelets (GnPs) were oxidized to functionalize them with molecules of pimelic acid (PA). This fact was confirmed by the presence of two characteristic bands assigned to C-H bonds of the aliphatic chains of the pimelic acid (2939 cm-1 and 2860 cm-1). Furthermore, the IR spectra show two vibration bands about 1575-1570 cm-1 and 1413-1410 cm-1, which could be attributed to an ionic bridging linkage between the oxygenated sites of the oGnPs and the organic molecules. The chemical modification was followed by XRD and RAMAN, where an increase in the D/G ratio would suggest a major disorder in the structure because of the attaching in the first instance of oxygen and the pimelic acid during the functionalization. The modified ones were added at different percentages of 0.05, 0.5, and 1 wt% into an iPP matrix to demonstrate the beta nucleating ability of our nanofiller. The relative percentages of the beta-crystal for all samples were determined by DSC and WAXD, 72% and 75% for the oGnP and 0.05%-PA, respectively. DMA measurements were carried out to follow the influence of the reinforcements on the visco-elastic properties of the iPP matrix. The results showed an increase in the storage modulus of 161.2% at-40 degrees C and an improvement in the loss modulus of 54.2% for the composite with 1 wt% of the modified ones. The impact strength for this nanocomposite was 39% higher than the raw iPP.

Automated summary

In this study, graphene nanoplatelets (GnPs) were oxidized and functionalized with pimelic acid (PA). The chemical modification was confirmed by the presence of characteristic bands in the IR spectra and an increase in the D/G ratio in XRD and RAMAN. The modified GnPs were added to an iPP matrix and showed improved beta nucleating ability and enhanced visco-elastic properties, as indicated by DSC, WAXD, and DMA measurements. The impact strength of the nanocomposite was also significantly higher than the raw iPP.