Polypropylene (PP) has the advantages of low cost

thermoplastic processing and good biocompatibility

and is widely used in the research of household appliances and medical devices. However

it has rarely been used in the preparation of capacitive pressure sensors. In this research

thermoplastic polyurethane (TPU)/PP blends were prepared by melt blending method

the prepared blends were foamed by supercritical carbon dioxide batching foaming technology. The microstructure and mechanical performances of the prepared TPU/PP blends and their foamed samples were characterized. Based on this

the effects and their mechanism of TPU on the mechanical and foaming properties of the blends and thus on the sensitivities of the sensors were analyzed. The results showed that TPU droplets were uniformly distributed in PP matrix. The deformation abilities of the blends were significantly improved by the TPU

and the values of modulus of the TPU/PP blends were much lower than that of the PP. In addition

the melt strengths of the blends were also improved by TPU. And thus

the cellular structures of the foamed TPU/PP samples were improved: the solid area and wormlike-connected cellular structure were significantly reduced or even disappeared in the foamed TPU/PP samples. Therefore

the foamed TPU/PP samples showed stronger deformation abilities

and the values of S of their corresponding sensors were higher. The values of S of the sensor for TPU/PP blend with 30 wt% TPU are 2.5 times (0~17 MPa) and 18.8 times (17~25 MPa) that for pure PP

respectively. By foaming the TPU/PP blend with 30 wt% TPU

the S of the corresponding sensor in the lower pressure range was further increased by 4.1 times. The application testing results show that the prepared sensor reveals good application prospect in detecting human movements such as walking

sitting and grasping.