The Surface Electric Conductive Modification In Order To As Semble Of Polymer Microspheres

Metal-organic composites have been widely studied for their excellent electrical,thermal,and mechanical properties.Among them,a layer of metal is modified on the surface of polymer microspheres to prepare conductive microspheres with a core-shell structure.The density is smaller than that of metals and can be uniformly dispersed in resin.It significantly improves the electrical conductivity of the resin and is an ideal filler for preparing conductive adhesives.Inspired by the fact that particles can be directionally moved by the electric field force in the resin,in the process of preparing conductive adhesive,the microspheres are assembled in an orderly manner in the electric field,which can reduce the use of microspheres,and improve the orientation of microspheres.The dielectric constant and thermal conductivity of the resin expand its application range.This article is divided into three chapters,which explore the process conditions of nickel(Ni)and silver(Ag)plating on polystyrene(PS)surface,and a typical acidic nickel plating waste liquid recovery and treatment process.(1)Preparation of nickel-plated polystyrene(Ni@PS)microspheres:First,a batch of polystyrene microspheres with a particle size of about 3.7μm was synthesized by means of dispersion polymerization.Pretreatment steps such as sensitization and activation,Ni@PS microspheres were prepared using a plating solution system using sodium hypophosphite as the reducing agent and nickel sulfate as the main salt,and the glass transition temperature was 110 ~oC.The thermal decomposition temperature is 400~460 ~oC,and the quality of the nickel plating layer accounts for about 50%of the total mass of Ni@PS microspheres.According to XPS and XRD,about 10%of the surface of Ni@PS microspheres is oxidized.The optimal conditions for electroless nickel plating are 75 ~oC,reaction time 10 hours,0.1M plating solution concentration,and acidic bath solution(pH=3~5)is selected.The synthesized nickel-plated microspheres have the best conductivity,with a conductivity of1.22 S/mm.(2)Preparation of silver-plated polystyrene(Ag@PS)microspheres:Mono-dispersed PS microspheres of about 3.7μm are used as the substrate.After optimized pretreatment steps,different reducing agents and silver-ammonia plating solutions are used.Ag@PS microspheres were prepared.When glucose was used as a reducing agent,the Ag coating on the surface of the microspheres was uniform and there were not too many Ag particles.The Ag@PS microspheres had excellent electrical conductivity.The Ag mass fraction on the surface of the Ag@PS microspheres increases with increasing concentration.When the silver ammonia solution concentration is 0.5 M,the Ag mass fraction can reach 65%.The conductivity performance of silver-plated microspheres under different temperature,time and main salt concentration conditions was studied.At the same time,cost and other factors were considered.The optimal silver-plating conditions were 65°C,reaction time 2 hours,0.2 M plating solution concentration,and Ag@PS microspheres of conductivity is 231.5S/mm.(3)Orientation and arrangement of Ni@PS microspheres in epoxy resin:First,the effect of different conductive microsphere additions and epoxy curing conditions on the performance of conductive adhesive was studied,and the optimal formula was 35%,Curing temperature is 70 ~oC,curing time is 6 h,the conductivity of the prepared conductive adhesive is 0.89 S/mm,and the peeling strength is 1.32 N/mm.Ni@PS microspheres were added to the bisphenol A epoxy resin matrix diluted with allyl glycidyl ether,and dispersed uniformly using ultrasonication and stirring.The applied electric field uses different frequencies,voltages,times,and temperatures to perform the alignment.At the same time,the effect of the amount of nickel-plated microspheres and the amount of diluent on the arrangement of the electric field is studied.35%,electric field strength is 6×10~5 V/m,frequency is 100 Hz,time is 30min,the prepared film has an electrical conductivity of 1.05S/mm,a dielectric constant of 7.89,and a thermal conductivity of 42 W/(m·K).