Construction,physicochemical Properties And Anticorrosion Application Of Water-based Polyaniline Composites

Polyaniline（PANI）,as one of the most promising conducting polymers,is endowed with excellent conductivity,high thermal and environmental stability,easy preparation and low cost.However,similar to the other conducting polymers,PANI has poor solubility and poor processability both in melt and solution conditions,which is due to the conjugated backbone and strong hydrogen bonding interaction.Polyurethane（PU）has been considered as one of the most versatile polymeric materials due to its tailorable structure and excellent properties such as excellent abrasion resistance,flexibility,and adhesion.Phosphorylated poly（vinyl alcohol）（PPVA）has attracted considerable interest because it can be used as metal complexes,cation exchange resins and anionic polyelectrolyte hydrogels,as well as a stabilizer and co-dopant for PANI.Besides,the intermolecular force is smaller than that of polyvinyl alcohol（PVA）and the solution stability is better.In order to overcome the poor dispersibility of PANI and extend the application performance of PANI,sulfonated waterborne polyurethane（SWPU）and PPVA were used as matrix materials for the preparation of polyaniline dispersions.The composite dispersion of polyaniline and polymer matrix with good stability and compatibility was obtained through chemical grafting polymerization of aniline monomer in polymer matrix.The structure and properties of the two kinds of dispersions were characterized and investigated.（1）In this research,anionic-nonionic synergistic SWPU was adopted as matrix to prepare nanosized PANI-g-SWPU dispersions with good compatibility,stability and conductivity.It was found that the SWPU structure played an important role in the stability of PANI-g-SWPU dispersion.The PANI-g-SWPU dispersion is endowed with much higher stability and no PANI precipitation is detected after storage for 1 year when R value is 1.2 and the PEG molecular weight is 1000.Then the influence of PANI content on the properties of the dispersion was investigated.When the aniline content is 20 wt%,the material had the best conductivity and the resistivity was 1.39Ω·cm,the asprepared PANI-g-SWPU dispersion can be directly used as the antistatic coatings,which is also suitable for large scalable production.（2）First,PPVA was prepared by esterification and modification of PVA substrate.And then the monomer,epichlorohydrin（ECIP）,which was reacted with PVA and aniline monomer,was introduced to the main chain of PPVA.Polyaniline graft modified phosphorylated polyvinyl alcohol（PANI-g-E-PPVA）dispersions were prepared by chemical grafting polymerization of aniline on PPVA matrix.The effects of phosphorylated degree of PVA on the crystallinity,micromorphology,rheological properties and mechanical properties of PANI grafted PPVA composites were studied by XRD,TEM,rheology tester and tensile test.XRD results showed that the crystallization of PVA decreased after phosphate esterification,SEM study of the surface of the composite film showed that the film surface formed by the PANI-g-E-PPVA dispersion was smoother than that of the PANI-g-E-PVA film.The SEM of the composite membrane showed that the fracture mode changed from brittle fracture to ductile fracture with the increase of phosphate degree.The cross-section of PANI-g-E-PPVA-3 is smooth and no polyaniline particles appear.In addition,the tensile strength of the PANI-g-E-PPVA-3 composite membrane can reach 38.62 MPa,and the elongation at break can reach 241.15%,showing strong and tough characteristics.（3）The PANI-g-E-PPVA and PANI-g-SWPU dispersions were combined with a water-based alkyd resin（WAR）to prepare anticorrosion coatings.The performances of the two coatings were compared by electrochemical tests.And the effect of the degree of phosphate esterification and the dosage of PANI-g-E-PPVA dispersion on the anti-corrosion performance of the coating prepared from the PANI-g-E-PPVA dispersion was studied.The water resistance test results showed that WAR/PANI-g-E-PPVA-3 had the lowest water absorption,and the increase in the degree of phosphate esterification can improve the water resistance of WAR/PANI-g-E-PPVA film.Electrochemical impedance spectroscopy measurements of anticorrosive coatings with different degreesofphosphateesterWAR/PANI-g-E-PPVAshowthatthe WAR/PANI-g E-PPVA-3 coating has the highest impedance modulus in the low frequency region,reaching 8.56×10⁷Ω·cm².When the amount of PANI-g-E-PPVA dispersion was 3 wt%,the WAR/PANI-g-E-PPVA anticorrosive coating showed the largest frequency range of capacitance behavior,the impedance modulus reached 5.25×10¹⁰Ω·cm² at low frequency area,and the best anticorrosive property was.