Study On The Process Of Polyacrylonitrile Fibers Modified By Copper Sulphate Penthydrate

Polyacrylonitrile(PAN)fibers modified by copper sulphate penthydrate have excellent electrical conductivity.It is widely used in industry and civil fields.These commercial conductive PAN fibers have been prepared through the post-processing of PAN filaments.However,These process has the disadvantages of long preparation step,high cost,poor stability,large energy consumption and so on.Online modification of pre-collapsing PAN fibers which have loose structure and micropores is an effective way to solve these problems.Recently,these modifying methods have drawn much attention by the PAN fibers enterprises.Based on the technology of gel dyeing process,the pre-collapsing PAN fibers were modified with copper sulphate penthydrate by one-bath dipping process and then the conductive PAN fibers were obtained.Effects of reagent concentration,dipping temperature,dipping time on the structures and properties of PAN fibers were studied.On this basis,weak reducing agents were used to improve the stability of these conductive PAN fibers in alkaline solution.Finally,various models were applied to investigate the adsorption dynamic behavior and adsorption mechanism.The purpose of this work is to verify the feasibility of online preparation of conductive PAN fibers.The main conclusions are summarized as follows:(1)The conductive PAN fibers modified by copper sulphate penthydrate were prepared by one-bath dipping method using pre-collapsing PAN fibers as the raw material.Through a series of experiments,the optimum processing parameters were obtained as follows:the concentrations of copper sulfate and sodium thiosulfate were 15g/L and 15g/L,respectively,and the dipping temperature and time was 85 ? and 30min.Under this condition,the volume resistivity of these fibers are up to 0.07? · cm.(2)The conductive component of the conductive PAN fibers mentioned above is CuS.The content of CuS particles presents as a gradient distribution across the fibers,which have high content at surface and a low content in center.After 4 days impregnating in the 5wt%NaOH solution,the volume resistivity of modified PAN fibers increased by 1700%.Meanwhile,after 180 days exposing in the air,the volume resistivity of these fibers also increased by 260%.These results showed that the conductivity of the PAN fibers had a significant decrease.(3)With the precondition of volume resistivity of the PAN fibers in the range of 10-1?10-2?·cm,the high-stability conductive PAN fibers were prepared by adding weak reducing agent.The fibers prepared by adding 5g/L weak reducing agent were immersed in 5 wt%NaOH solution for 4 days,and the volume resistivity rose by 189%.Besides,the volume resistivity of these fibers slightly increased by 10.8%in the air for 180 days,showing a good conductive stability.(4)The conductive component of the high-stability conductive PAN fibers is Cu9S5.Although the volume resistivity of Cu9S5 is higher than CuS,its stability in the alkaline solution is better than CuS and it will be helpful to the dyeing process.Through above conclusion,the conductive component could be controlled by adding weak reducing agent,so that to keep the conductivity and stability of PAN fibers.(5)The investigation of adsorption kinetics shows that the process of copper ions diffusing into PAN fibers is a chemical adsorption process.