Mechanical And Electromagnetic Shielding Properties Of Carbon Nanomaterials Reinforced Thermoplastic Elastomers And Their Microcellular Foams

With the rapid development of modern science and technology,the use of wireless communication equipment and electronic equipment brings great convenience to people's life and industrial development,but it inevitably brings more and more serious electromagnetic radiation pollution.Electromagnetic radiation pollution not only interferes with the normal work of equipment,but also poses a threat to the safety of human life and causes serious harm to the normal development of society.The development of high-performance electromagnetic shielding material is an effective measure to solve this hazard,traditional metal and metal-based electromagnetic shielding material has excellent electromagnetic shielding performance because of its high conductivity,but there are many disadvantages,such as high density,poor corrosion resistance,high processing costs.In this context,the development of low-cost,environmentally friendly,lightweight,widely used in electromagnetic interference shielding conductive materials are becoming more and more urgent.Conductive polymer composite material is a powerful candidate material,which has the advantages of low cost,light weight,good chemical stability,good flexibility and simple processing,and has broad application prospects in the field of electromagnetic shielding.In order to meet the requirements of electronic informationization and intelligent electromagnetic shielding materials such as lightweight,flexible and wearable,thermoplastic elastomers can be used to prepare flexible conductive composite materials.At the same time,the use of microcellular foaming technology can better regulate the comprehensive performance of flexible conductive composite materials,expand the application of flexible conductive polymer materials in the field of electromagnetic shieldingIn this paper,thermoplastic polyurethane(TPU)and polyether block amide(Pebax)are used as the polymer matrix,and nano graphite and carbon nanotubes are used as conductive fillers to prepare flexible composite materials with electromagnetic shielding properties,The mechanical and electromagnetic shielding performance were regulated by microcellular foaming.The main research contents are as follows:First,the TPU/nanographite composite was prepared by the melt blending method.After the microcellular foaming,the influence of the filler and the microcellular foaming on the mechanical properties and electromagnetic shielding performance of the composite was studied.Studies have shown that high content of nano graphite can make the TPU matrix have excellent EMI shielding performance.Although foaming will cause a certain loss of electromagnetic shielding performance,it can effectively reduce weight and enhance elasticity,thereby greatly expanding the application field of TPU materials.For solid composite materials,an appropriate nano-graphite content(10 wt%)improves the strength,rigidity and toughness of TPU at the same time.However,if the content of nano-graphite is too high(20 wt%),the mechanical properties will be deteriorated,and the material exhibits lower mechanical properties after foaming.Secondly,the TPU/MWCNT composite material was prepared by the solution blending method,and the light-weight,high-strength,and good EMI shielding TPU/MWCNT composite material was prepared by the microcellular foaming with the foaming agent of carbon dioxide.Studies have shown that carbon nanotubes as a heterogeneous nucleating agent can significantly improve the cell structure of TPU.For solid composite materials,an appropriate carbon nanotube content(3 wt%)can simultaneously increase the strength and toughness of TPU by 25%,60%,high content(5 wt%)will reduce the strength.10wt%carbon nanotubes can significantly increase the electrical conductivity of the composite material to 4.1 ×10-3 S/cm,and endow the composite material with excellent electromagnetic interference shielding effectiveness,up to about 27 dB.The main mechanism of shielding is reflection.Although foaming will cause a certain loss of electrical conductivity and electromagnetic shielding performance,it can effectively reduce weight.Finally,the Pebax/MWCNT composite was prepared by the solution blending method.In order to fully study the effect of the carbon nanotube content on the morphology,thermal properties,mechanical properties,and EMI shielding performance of the composite,the Pebax/MWCNT composites were characterized and analyzed.Studies have shown that as the content of carbon nanotubes increases,the storage modulus of Pebax/MWCNT composites increases,and the loss factor decreases,showing low damping and low hysteresis loss,and it can maintain good mechanical properties at low temperature.After the addition of carbon nanotubes,due to the poor combination of carbon nanotubes and Pebax matrix,the tensile strength and elongation at break of the composite material are significantly reduced,but the modulus is significantly improved.In addition,In addition,10 wt%carbon nanotubes can increase the conductivity of the composite material to 1.23 × 10-3 S/cm,and endow the composite material with excellent electromagnetic interference shielding performance,the highest value is about 21 dB,and the main mechanism of shielding is absorption.