Preparation And Properties Research Of Conductive UHMWPE/PANI Composite Fibers

Ultra-high Molecular Weight Polyethylene (UHMWPE) fiber is a new kind ofhigh performance fiber which has been widely used in many fields now. However, theaccumulation of electrostatic charge on UHMWPE fiber is generally observed duringits processing and practical use, which may lead to processing difficulties and causeproblems. Therefore, the present applications of UHMWPE fiber are restricted inanti-static, electromagnetic shielding, electrical engineering and other fields. Recently,with the continuous innovation of the application, the study on the conductingapplication of UHMWPE fiber becomes more and more fierce. The conductiveperformance can greatly enhance the functionality and added-value of UHMWPE fiberproducts, and thus more applications and broader market can be expected to bedeveloped.In this dissertation, UHMWPE fiber was pre-treated by plasma firstly in order toimprove its adsorption performance. Then during the conductive treatment onUHMWPE fiber, aniline monomer was used as the raw material, and a layer ofconductive polyaniline polymerized film was formed on the surface of the fiber byin-situ polymerization. The influence of the plasma pretreatment parameters and thein-situ polymerization process parameters on the conductive properties of theUHMWPE/PANI composite fibers was investigated. To overcome the disadvantages ofthe conventional in-situ polymerization, a novel method based on in-situpolymerization for continuous manufacturing conductive UHMWPE/PANI compositeyarns was presented, and the effect of the process parameters on the conductiveproperties of composite yarns was discussed. Additionally, the structure and propertiesof the conductive composite fibers and yarns were investigated in details. Finally, the knitted fabric of conductive UHMWPE/PANI composite yarns was prepared, andits strain-resistance performance was researched. The electromagnetic shieldingmaterials were prepared using the parallel conductive UHMWPE/PANI compositeyarns, and its anti-electromagnetic radiation property was investigated.The results showed that the oxygen plasma pretreatment could improvethe conductivity of conductive UHMWPE/PANI composite fibers, and the electricalconductivity showed a trend of first increasing and then decreasing with the extensionof exposure time, the increase of discharge power and the increase of oxygen pressure.The optimum pretreatment parameters were the exposure time of1min, thedischarge power of70W, and the oxygen pressure of40Pa.The conductivity of the conductive UHMWPE/PANI composite fiber prepared bythe conventional in-situ polymerization was affected by many factors, such asoxidant, doping acid, reaction time, and reaction temperature. The conductivity of theconductive UHMWPE/PANI composite fiber could reach0.2S/cm, with the35g/Lammonium persulfate as the oxidant, the0.7mol/L HCl as the doping acid, the reactiontime of80min and the reaction temperature of20°C.The conductive UHMWPE yarn was continuously manufactured using ahome-made yarn pretreatment device with atmospheric pressure plasma and ahome-made conductive composite yarn continuous manufacture device based on themethod of in-situ polymerization. The electrical conductivity of the conductiveUHMWPE/PANI composite yarn could reach the highest value of1S/cm, with the150g/L ammonium persulfate as the oxidant, and the1.75mol/L H2SO4as the doping acid.Meanwhile, the conducting processing speed, roller pressure and the supply rate ofreaction mixture also had influences on the electrical conductivity of theconductive composite yarn. The electrical conductivity of the conductiveUHMWPE/PANI composite yarn increased with the reduction of theconducting processing speed and the increase of the roller pressure. However, eithertoo fast or too slow supply rate of the reaction mixture could cause an adverse impacton the electrical conductivity of the conductive composite yarn. The electrical conductivity of the composite conductive yarn could reach the highest value, when thesupply rate of the reaction mixture was10ml/min.Through the analysis on the structure and properties of the conductiveUHMWPE/PANI composite fiber and yarn, it could be obtained that either thecomposite fiber or the composite yarn was the blend of the UHMWPE fiber andthe polyaniline, which had skin-core structure. The thermal stability of the conductivecomposite fiber was close to that of the matrix fiber, while the thermal stability of theconductive composite yarn became weaker than that of the matrix. The breakingstrength of the conductive composite fiber increased slightly and the elongation atbreak did not change, compared with those of the matrix fiber. However, both thebreaking strength and the elongation at break of the conductive composite yarnincreased, compared with those of the yarn without treatment, but the initialmodulus decreased. The electrical conductivity of the composite conductive fiber andyarn became weaker after drying, washing and after a period of time. Meanwhile, thetolerance of alkali of the composite conductive fiber and yarn was not satisfactory.The knitted fabric of conductive UHMWPE/PANI composite yarn was used as astrain sensor. Under the small strain condition, the resistance of the sensorincreased with increasing the strain, and the sensor presented the better linearity,sensitivity and repeatability. The linearity, sensitivity and repeatability of the sensorcontinuously increased with the increase of the fabric count. Under the large straincondition, the resistance of the sensor increased firstly with increasing the strain andthen decreased. However, the repeatability of the fabric sensor in the largestrain condition was worse than that in the small strain condition.The electromagnetic shielding materials prepared usingthe parallel UHMWPE/PANI composite yarns showed a certain electromagneticshielding effect. The electromagnetic shielding effectiveness increased withthe increase of the density of the conductive yarn arrangement. The SE value couldreach more than10dB, when two parallel yarn layers with the distance of1mmbetween the adjacent yarns in each layer were overlapped perpendicularly. The arrangement angle of two layers also affected the electromagnetic shieldingeffectiveness, and the SE value was the highest when the arrangement angle was90°,and the anti-electromagnetic radiation effect decreased gradually with the decrease ofthe arrangement angle.