Study On Preparation And Properties Of Biomass Electromagnetic Shielding Composites

In this paper,the preparation methods of two kinds of electromagnetic shielding composites and the properties of two kinds of biomass composites were studied.Prepared electromagnetic interference(EMI)shielding materials based on carbon black(CB),carbon fiber(CF),respectively with bamboo charcoal(BC),and epoxy resin.The effects of adding bamboo charcoal on the mechanical properties and electrical resistivity of epoxy composites were studied.The composites were prepared at 120℃ by the curing-molding method through blending the fillers in epoxy resin.The dynamic thermal mechanical properties,electrical resistivity,and electromagnetic interference(EMI)shielding effectiveness were also investigated.Scanning electron microscopic(SEM)analysis shown the good dispersion of the mixed fillers blending in epoxy,the results revealed that the BC/CB and BC/CF composites had perfect conductive network structure and resulted in better dynamic thermal mechanical properties;The electrical resistivity declined with the increase of bamboo charcoal contents;consequently the EMI shielding effectiveness improved gradually.The electrical resistivity of BC/CB composites was declined from 2.128 Ω·m to 0.785 Ω·m,however,the electrical resistivity of BC/CF composites was from 0.538 Ω·m down to 0.071 Ω·m,corresponded to the best EMI shielding effectiveness of BC/CF composites,which could be above 60 dB over a frequency range of 30 MHz to 1500 MHz while the carbon fiber content was at 40 wt%.To investigating the effects of different graphene composites with different content of bamboo charcoal(BC)through curing molding,and fabricated BC/graphene electromagnetic interference(EMI)shielding composites with the good EMI shielding effectiveness by adding different content of BC to the natural graphene and synthetic graphene,respectively.And the mechanical performance,dynamic thermal mechanical properties,electrical resistivity,SEM,and EMI shielding effectiveness were studied.The results suggested that the Tg was improved of both natural and synthetic graphite composites when BC content increased;the electrical resistivity declined then the EMI shielding effectiveness increased all the time.The maximum EMI shielding effectiveness reached about 30 dB when the BC was 40 wt%of synthetic graphene composite.However,due to the aggregation between particles,the flexural modulus was decreased of both two kind graphene composites.The SEM showed that the better interface effectiveness of synthetic graphene composites.In all,synthetic graphene composites had the better mechanical properties when the content of BC was 30 wt%.And with the increase content of BC,the EMI shielding effectiveness of graphene composites enhanced.On the study of biodegradable electromagnetic shielding materials,the biomass foaming materials were prepared by the introduction of twelve surfactant sodium dodecyl sulfate(SDS)through the test in the low temperature,prepared the carbon fiber/cellulose electromagnetic shielding foaming material by adding different ratio of length to diameter of conductive filler with carbon fiber.The samples bubbles properties were analyzed by scanning electron microscopy on wet solution and dried foam,and analysis the microstructure of carbon fiber electromagnetic shielding conductive mesh structure,and also analysis the thermal conductivity and electromagnetic shielding effectiveness of the electromagnetic shielding with carbon fiber/cellulose foaming materials.The results showed that the introduction of surfactant molecules,increasing the foam bubbles in the pores,however,with the increase of the cellulose concentration,pore size decreases;The thermal conductivity of carbon fiber/foam cellulose electromagnetic shielding analysis showed that the thermal conductivity increasing with the adding of the carbon fiber content;The electromagnetic shielding effectiveness of the carbon fiber/cellulose electromagnetic shielding foaming materials showed that with the increasing of carbon fiber content,the shielding effectiveness were improved obviously.When the long carbon fiber content was 20 wt%,the electromagnetic shielding effectiveness of the long carbon fiber/cellulose electromagnetic shielding foaming material was better than the short ones,the biggest value was over 60 dB.