Preparation of Polypropylene-based Cellular Materials with Stronger Deformation Ability and Research on Their Pressure Sensing Performances
Polypropylene(PP)has the advantages of low cost,thermoplastic processing and good biocompatibility,and is widely used in the fields 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,and then the blends were foamed by supercritical carbon dioxide batching foaming.The microstructure and mechanical properties of the TPU/PP blends and their foams were characterized.Based on this,the effects of the TPU on the mechanical and foaming properties of the blends,and thus on their pressure sensing performances were analyzed.The SEM images of the blends showed that the TPU droplets were uniformly distributed in the PP matrix.And the mechanical results suggests that the deformation abilities of the blends were significantly improved by these TPU droplets.Thus,the pressure sensors with the blends as dielectric layers show higher sensitivity(S).It is also found that,the melt strengths of the blends were improved by the TPU.And thus the cellular structures of the TPU/PP foams were improved:the solid area and wormlike-connected cellular structure in the TPU/PP foams were significantly reduced or even disappeared.Therefore,the deformation abilities of the TPU/PP blends were improved by foaming.And the values of S for the sensors with TPU/PP foams were higher than those with the TPU/PP blends.For example,for the blend with 30 wt％ TPU,the values of S in elastic bending and buckling regions were increased by 4.1 and 0.4 times,respectively,after foaming.The application testing results show that the sensor with the PP-based cellular materials as dielectric layers reveals good application prospect in detecting human movements,such as walking,sitting and grasping.
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