Preparation And Properties Of Multifunctional Electromagnetic Shielding Material Based On Rock Wool

Electromagnetic pollution has adverse effects not only on electronic equipment or precision instruments through interferring their normal operation,but also on human health.Electromagnetic shielding materials can effectively absorb unnecessary electromagnetic radiation,thereby reducing the harmful effects of electromagnetic waves.Extensive research has been carried out on the design and construction of electromagnetic interference(EMI)shielding materials with ultra-high shielding performance,ultra-light weight or ultra-thin thickness,However,there are few reports about the multifunctional electromagnetic shielding materials with hydrophobicity,flame retardancy and thermal insulation.In the first part of this thesis,we prepared RW-rGO composites by dipping rock wool(RW)in a graphene oxide solution,and then reducing it.Thermal insulation,flame retardancy and hydrophobicity were explored.The results showed that,1)the electromagnetic shielding effectiveness of RW-rGO composites was positively correlated with electrical conductivity,and the highest shielding effectiveness can reach 30.4 dB;absorption was the main shielding mechanism;2)rGO aerogel burned vigorously under flame attack,while the RW-rGO composite material could maintain its structural integrity;no sparks were observed;it indicated that the RW-rGO composite material had excellent flame retardant property;3)thermal conductivity of the RW-rGO composite material is only about 0.041 W/m·K,equivalent to the thermal conductivity of commercially available thermal insulation materials;4)the original RW is hydrophilic,while the RW-rGO composite material showed good hydrophobic property that the water contact angle of could reach 132.7°.In the second part of this paper,we prepared a multifunctional RW/AgNPs/Fe₃O₄/PDMS electromagnetic shielding composite material by a two-step dip-coating method.Firstly,RW/AgNPs composite was obtained by dipping rock wool in silver nitrate solution,and then the adsorbed Ag⁺was reduced to Ag nanoparticles(AgNPs)by hydrazine hydrate.Secondly,the RW/AgNPs composite was dipped in the dispersion of Fe₃O₄ and PDMS to obtain the RW/AgNPs/Fe₃O₄/PDMS composite.The electromagnetic shielding effectiveness,flame retardancy and hydrophobicity of the composite were examined.The results showed that,1)the resistivity of RW/AgNPs/Fe₃O₄/PDMS composites was negatively correlated with the concentration of silver nitrate solution.When using a 20 wt%silver nitrate solution,the resistivity of the RW/AgNPs/Fe₃O₄/PDMS composite material was as low as 0.8?·cm,and the electromagnetic shielding effectiveness could reach 35 dB;absorption is the main shielding mechanism;2)the RW/AgNPs/Fe₃O₄/PDMS composite showed excellent flame retardant performance;it maintained original shape and integrity,and no sparks were observed,when being subjected to flame attack for 90 s;3)the composite showed superhydrophobicity and self-cleaning ability;water contact angle of the composite material could reach 153.1°.