Effect of multi-walled carbon nanotubes on the physical properties and crystallisation of recycled PET/TPU composites

Thermoplastic polyurethane (TPU) was blended with recycled polyethylene terephthalate (rPET) to prepare rPET/thermoplastic polyurethane (TPU) composites. Meanwhile, multiple-walled carbon nanotubes (MWCNTs) were employed as a reinforcing filler to study the synergistic effect between CNTs and rPET/TPU composites. The effect of CNT content on the morphology and micro-structure of the composites was investigated using a scanning electron microscope (SEM) and X-ray diffraction (XRD). The thermal properties were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The mechanical properties were investigated using tensile tests and hardness measurements. The results showed that TPU was compatible with rPET. The existence of rPET changed the crystalline phase and affected the glass transition and crystallisation temperature of the TPU matrix. The rPET/TPU composites displayed poor thermal stability and tensile properties when compared to pure TPU. The addition of CNTs had no effect on the crystalline phase of the rPET/TPU composites. Due to the occurrence of interfacial adhesion between the CNTs and rPET, the CNTs displayed an offset effect on the reaction of rPET and decreased the rigidity of the molecular chain in the rPET/TPU composites. The thermal stability and tensile strength of the CNTs/rPET/TPU composites improved with an increase in CNT content.