Preparation And Properties Of Polyether Ether Ketone/Polyether Imide Anti-corrosion Coatings

With the continuous development of industrialization,environmental,economic and safety problems caused by metal corrosion appear constantly.The protection of metal has always been an important research topic.Because of the advantages of simple operation,excellent anti-corrosion and low cost,the coating protection method is widely used in the protection of metal.Polyether ether ketone（PEEK）is a semi-crystalline thermoplastic polymer with excellent mechanical properties,high temperature resistance,corrosion resistance,chemical resistance and other properties,which is widely used in aerospace,automotive,biomedical and other fields.Because of its excellent performance,more and more researchers have applied it in the field of metal anti-corrosion.However,due to PEEK is insoluble in water and solvents,it is difficult to prepare liquid coatings.Most of the previous researchers used electrostatic spraying,flame spraying and other methods to prepare coatings under complex construction conditions.There are relatively few reports about air spraying,and PEEK is usually added into the coating system of epoxy resin,polyurethane and other normal or low temperature curing,so it is difficult to give full play to the excellent performance of PEEK.Polyether imide（PEI）is a kind of high temperature resistant thermoplastic special engineering plastics.The PEEK/PEI system is completely compatible at high temperature melting.At the same time,PEI do not change the crystallization mode of PEEK,and only reduce the crystallization rate and partial crystallinity,which can better control the crystallization process of PEEK.In this paper,aiming at the problem that PEEK is difficult to prepare liquid coatings,and the excellent properties of PEEK coatings cannot be fully played after being prepared by using epoxy resin,polyurethane and other film forming materials,PEI was introduced as an auxiliary film forming material to prepare PEEK coatings,and the relationship between its properties,formula and crystallization as well as the high temperature and high pressure application test was explored.First,a series of PEEK/PEI composite coatings containing polyether ether ketones with different melt indices were prepared.The results show that the impact resistance of the coating is obviously improved by adding PEEK with excellent mechanical properties.At the same time,the water absorption of the coating decreases obviously because of its barrier property.With the increase of melting index of PEEK added,the coating has better leveling property.In the DSC test,the glass transition temperature of the coating changes from two to one when PEEK melting index exceeds 12 g,which proves that PEEK and PEI are completely compatible.The electrochemical test and neutral salt spray test showed that the coating KI96 with PEEK melting index of 96 g had the best anti-corrosion performance.Secondly,a series of PEEK/PEI composite coatings with different polyether ether ketone contents were prepared.The results showed that the mechanical properties of the coating were significantly improved with the increase of PEEK content.The coating maintains good chemical resistance,low water absorption and excellent thermal properties.The electrochemical test results show that the Bode pattern of KI50 coating remains above 10¹⁰ after 120 days of immersion.After 1000 h neutral salt spray test,only slight corrosion flow was generated on the surface of the coating,and there was no foaming around the scratches,indicating that the coating KI50 has the best anti-corrosion performance.Furthermore,in order to investigate the effect of heat treatment on the structure and properties of composite coatings,a series of semi-crystalline coatings were prepared by different cooling and heat treatment methods.The results show that the coating cooled naturally at room temperature has a certain degree of crystallinity.After heat treatment,the crystallinity of the coating is slightly improved.This is because the crystallization process of the coating has taken place,and the crystal structure has not changed much,and the crystallinity of the coating has been improved to a certain extent.The quenched coating is amorphous.With the heat treatment of the coating,the coating begins to crystallize,the structure changes greatly,and the crystallinity increases obviously.The results show that the hardness of the quenched coating increases and the wear rate and friction coefficient decrease with the increase of treatment temperature.At 300℃,the coating has the best hardness and friction performance.Finally,combined with the actual application,the coating was tested at high temperature and high pressure,the experimental conditions were 140℃,160℃and180℃,and the test time was 1 h.The results show that the surface integrity of the coating has no obvious change under the conditions of 140℃and 160℃.At 180℃,foaming,loss of light and adhesion were found on the surface of the coating,and the coating lost its protective ability.