TPU nanocomposites tailored by graphene nanoplatelets: the investigation of dispersion approaches and annealing treatment on thermal and mechanical properties

The present work investigates the combined effect of the addition of graphene nanoplatelets (GNPs) to the thermoplastic polyurethane copolymer (TPU) and thermal treatment evaluation of the resultant TPU/GNP nanocomposite. Thus, this factor can be evaluated through a variety of dynamic mechanical and thermal measurements. The TPUs as nanocomposites were synthesised by three different approaches of mixing (in situ polymerisation melt compounding and solution mixing) with different weight ratios. Various dispersion processes were employed to obtain better dispersed GNP and thus strong interaction, leading to an effective performance of the TPU/GNP system. X-Ray diffraction and Raman spectroscopy tests displayed the inter-spacing planar quality of GNP nanofillers. Dynamic mechanical analysis revealed that the storage modulus (EMODIFIER LETTER PRIME) of TPU nanocomposites how a significant performance particularly at 20 wt.%, 10 wt.% and 5 wt.% of GNP for in situ polymerisation melt compounding and solution mixing, respectively. The microphase-separated structure of TPU nanocomposite samples after thermal treatment (at 80 degrees C for 4 days) was investigated from for all dispersion methods. Consequently, the overall TPU crystallinity decreased after thermal treatment compared with untreated samples, presuming an ordering suppression of hard segments that involved with GNP. Dispersion and interaction of GNP can play a crucial role in enhancing the thermal and mechanical properties, and thus, a significant improvement for TPU nanocomposites. The tensile test showed significant enhancement with GNP incorporation before thermal treatment. On the contrary, a deterioration in tensile modulus and tensile strength resulted from thermal treatment. A modified Halpin-Tsai model was utilised to predict the mismatch between the empirical and theoretical results. It found a clear diversity in modulus of TPU/GNP samples, in particular at greater GNP content.