Recent progress of silicone-based electromagnetic shielding materials
With the rapid advances in electronic device and communication technologies,the electromagnetic radiation and electromagnetic interference(EMI),which causes adverse effect to human health and the stable functioning of electronic equipment,becomes increasingly serious.Effective EMI shielding materials that meet a series of requirements,such as chemical corrosion resistance,lightweight,flexibility,tunable morphology and processing easiness et al.,to satisfy increasingly complex application environment in fields related to aerospace,wearable electronic devices and artificial intelligence are thus highly desired.Polysiloxane,as an elegant representative of semi-inorganic polymer with repeated silicon oxygen bonds(-Si-O-)in the main chain,has a series of unique properties,such as high elasticity,insulation,flame retardancy,hydrophobicity,UV radiation resistance et al.,that other polymers do not possess.However,as highly insulating materials,the silicon rubber matrix generally requires high filling of electrical/magnetically conductive fillers to form conductive pathways inside system to achieve the desired EMI shielding performance.Thus,the selection of electromagnetic shielding fillers,the design of conductive networks,and the preparation process of composite materials were important factors affecting the electromagnetic shielding performance of silicone rubber composite materials.Over the last decade,a variety of silicon rubber based high-performance EMI composites have been developed and applied in various electronics due to versatility,stable performance,and processability.This mini-review will provide a brief overview of the latest progress on silicone rubber based EMI composite.The content is organized based on the electromagnetic shielding filler type and conductive network construction strategies,catalogzied as single component systems,multi-component composite systems,and three-dimensional conductive skeleton systems.The progress is mainly reflected in the following aspects:(1)Improve the interface compatibility between the filler and silicone rubber in various form(liquid silicone rubber,high-temperature vulcanized silicone rubber,silicon gel,silicone resin,etc.)through a variety of traditional mixting processes,such as three roll grinding method,double planet mixing method,double roll mill method,mechanical mixing method combined with ultrasonic method and other dispersion processes;(2)the construction of efficient conductive networks by the combination of fillers with different characteristics,shapes and size,to make the silicone rubber EMI composites multifunctional,including high voltage retraction elasticity,aging resistance,bending resistance,lightweight,insulation and thermal conductivity;(3)developing new structural hybrid fillers,such as multi-layer heterogeneous core-shell structured fillers,and three-dimensional continuous conductive skeletons,and it is application in high-performance silicon rubber composites,and the construction of multi-layer structured composite.From our view point,how to fully utilize the unique characteristics of silicone rubber,such as flexibility,chemical corrosion resistance,high insulation,and strong designability,and combine them with specific application scenarios to prepare multifunctional EMI silicone rubber composite will be the future development trend.At present,many research works are based on the construction of efficient conductive networks,and the obtained silicone rubber composite generally have certain conductivity.With the rapid development of electronic and communication technology,many new application scenarios require electromagnetic shielding materials with insulation properties to avoid short-circuiting.Thus,the preparation of silicone-based EMI composites with multiple functions such as electrical insulation,thermal conductivity,and super-hydrophobicity,will be highly desired.
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维普
