Mechanical And Shape Memory Properties Of Carbon Nanotubereinforced Thermoplastic Polyurethane Composites

Thermoplastic polyurethane(TPU)is a polymer with a special structure.It is a block linear polymer composed of soft segments and hard segments through copolymerization.This special structure makes it not only highly elastic,but also has certain properties.plasticity.Therefore,TPU has important applications in the automotive industry,the medical industry,and the sensor industry.However,when TPU is used as a shape memory polymer,its heat resistance and strength are weak,which limits its application range.In order to expand the application range of TPU,improving its performance has become the focus of research.As an excellent inorganic nanomaterial,carbon nanotubes(CNTs)have good mechanical properties,electrical conductivity and thermal conductivity,and become an excellent filler for modified polymers.In this paper,the surface of CNTs particles was treated with a mixed solution of sulfuric acid(H2SO4)/nitric acid(HNO3),and the CNTs/TPU composites were prepared by melt blending of the treated CNTs and TPU(contents of 1wt%,2wt%,3wt%,5wt%)%).The rheological behavior of the sample was tested by rotational rheometer;the crystallization behavior of the sample was tested by X-ray diffractometer(XRD);the thermal crystallization temperature of the sample was tested by differential calorimetry scanner(DSC)and thermogravimetric analyzer(TGA).and thermal stability;using universal testing machine,multi-functional friction and wear testing machine,nano-indenter and other instruments to test and analyze the performance of CNTs/TPU composite samples in terms of mechanics,tribology,etc.;Shape memory behavior was tested to observe the shape recovery and shape retention effects of the samples under thermal stimulation conditions.The experimental results show that the CNTs after the surface functional modification of the mixed acid solution have good dispersibility and compatibility in the TPU matrix.The addition of acid-modified CNTs improves the storage modulus and loss modulus of the CNTs/TPU composite to a certain extent,and preserves the processing fluidity of the composite under high-frequency shearing.After acidified modified CNTs were added to the TPU matrix,compared with pure TPU,the melt crystallization temperature of CNTs/TPU composites shifted to the high temperature region,and the thermal degradation temperature of the soft and hard segments increased to 335 °C and 415 °C,respectively,indicating that the composites The thermal stability of the material is enhanced.In terms of mechanical properties,compared with pure TPU materials,the tensile strength and impact strength of CNTs/TPU composites are enhanced,which reach the maximum in 2wt% CTN/TPU composites.With the addition of CNTs,the hardness and wear resistance of the composites have also been improved to a certain extent.In the shape memory performance test,with the addition of CNTs,the shape recovery and shape retention effects of the composites increased first and then decreased.For the shape recovery and shape retention effects of CNTs/TPU composites,with the addition of CNTs,compared with pure TPU materials,although there is a slight delay,the recovery effect is improved to a certain extent.And when the CNTs content reaches 2wt%,the shape recovery and shape retention of the composites are the best.With the increase of the number of memory cycles,the shape recovery and shape retention effects of all materials decreased,but the effect of 2wt% CNTs/TPU composite was always better than that of pure TPU material.